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Sample records for electrophilic aromatic substitution

  1. Electrophilic aromatic substitution over zeolites generates Wheland-type reaction intermediates

    NARCIS (Netherlands)

    Chowdhury, Abhishek Dutta; Houben, Klaartje; Whiting, Gareth T.; Chung, Sangho; Baldus, Marc; Weckhuysen, Bert M.

    2018-01-01

    The synthesis of many industrial bulk and fine chemicals frequently involves electrophilic aromatic substitution (SEAr) reactions. The most widely practiced example of the SEAr mechanism is the zeolite-catalysed ethylation of benzene, using ethylene as an alkylating agent. However, the current

  2. Computational Methods to Predict the Regioselectivity of Electrophilic Aromatic Substitution Reactions of Heteroaromatic Systems

    DEFF Research Database (Denmark)

    Kruszyk, Monika; Jessing, Mikkel; Kristensen, Jesper L

    2016-01-01

    The validity of calculated NMR shifts to predict the outcome of electrophilic aromatic substitution reactions on different heterocyclic compounds has been examined. Based on an analysis of >130 literature examples it was found that the lowest calculated 13C and/or 1H chemical shift of a heterocycle...... correlates qualitatively with the regiochemical outcome of halogenation reactions in >80% of the investigated cases. In the remaining cases, the site of electrophilic aromatic substitution can be explained by the calculated HOMO orbitals obtained using density functional theory. Using a combination...

  3. Reactivity and selectivity of the electrophile aromatic substitution in the gas phase by positive 80Br and 125I decay ions

    International Nuclear Information System (INIS)

    Knust, E.J.

    1975-02-01

    The nuclear isomeric transition sup(80m)Br(IT) 80 Br or the electron capture decay 125 Xe(EC) 125 I in the presence of high concentrations of a noble gas such as Ar or Xe are suitable for the study of the electrophilic substitution of bromium or iodonium ions in the gas phase. By using this nuclear method, which, unlike physical methods, also allows the determination of the isomer distribution, the electrophilic aromatic bromation and iodation of mono-substituted benzene compounds through unsolvated positive bromine or iodine ions could be investigated for the first time using radio-gas chromatographic techniques. (orig./LH) [de

  4. Reaction of bromine and chlorine with phenolic compounds and natural organic matter extracts--Electrophilic aromatic substitution and oxidation.

    Science.gov (United States)

    Criquet, Justine; Rodriguez, Eva M; Allard, Sebastien; Wellauer, Sven; Salhi, Elisabeth; Joll, Cynthia A; von Gunten, Urs

    2015-11-15

    Phenolic compounds are known structural moieties of natural organic matter (NOM), and their reactivity is a key parameter for understanding the reactivity of NOM and the disinfection by-product formation during oxidative water treatment. In this study, species-specific and/or apparent second order rate constants and mechanisms for the reactions of bromine and chlorine have been determined for various phenolic compounds (phenol, resorcinol, catechol, hydroquinone, phloroglucinol, bisphenol A, p-hydroxybenzoic acid, gallic acid, hesperetin and tannic acid) and flavone. The reactivity of bromine with phenolic compounds is very high, with apparent second order rate constants at pH 7 in the range of 10(4) to 10(7) M(-1) s(-1). The highest value was recorded for the reaction between HOBr and the fully deprotonated resorcinol (k = 2.1 × 10(9) M(-1) s(-1)). The reactivity of phenolic compounds is enhanced by the activating character of the phenolic substituents, e.g. further hydroxyl groups. With the data set from this study, the ratio between the species-specific rate constants for the reactions of chlorine versus bromine with phenolic compounds was confirmed to be about 3000. Phenolic compounds react with bromine or chlorine either by oxidation (electron transfer, ET) or electrophilic aromatic substitution (EAS) processes. The dominant process mainly depends on the relative position of the hydroxyl substituents and the possibility of quinone formation. While phenol, p-hydroxybenzoic acid and bisphenol A undergo EAS, hydroquinone, catechol, gallic acid and tannic acid, with hydroxyl substituents in ortho or para positions, react with bromine by ET leading to quantitative formation of the corresponding quinones. Some compounds (e.g. phloroglucinol) show both partial oxidation and partial electrophilic aromatic substitution and the ratio observed for the pathways depends on the pH. For the reaction of six NOM extracts with bromine, electrophilic aromatic substitution

  5. Computational Study of Chemical Reactivity Using Information-Theoretic Quantities from Density Functional Reactivity Theory for Electrophilic Aromatic Substitution Reactions.

    Science.gov (United States)

    Wu, Wenjie; Wu, Zemin; Rong, Chunying; Lu, Tian; Huang, Ying; Liu, Shubin

    2015-07-23

    The electrophilic aromatic substitution for nitration, halogenation, sulfonation, and acylation is a vastly important category of chemical transformation. Its reactivity and regioselectivity is predominantly determined by nucleophilicity of carbon atoms on the aromatic ring, which in return is immensely influenced by the group that is attached to the aromatic ring a priori. In this work, taking advantage of recent developments in quantifying nucleophilicity (electrophilicity) with descriptors from the information-theoretic approach in density functional reactivity theory, we examine the reactivity properties of this reaction system from three perspectives. These include scaling patterns of information-theoretic quantities such as Shannon entropy, Fisher information, Ghosh-Berkowitz-Parr entropy and information gain at both molecular and atomic levels, quantitative predictions of the barrier height with both Hirshfeld charge and information gain, and energetic decomposition analyses of the barrier height for the reactions. To that end, we focused in this work on the identity reaction of the monosubstituted-benzene molecule reacting with hydrogen fluoride using boron trifluoride as the catalyst in the gas phase. We also considered 19 substituting groups, 9 of which are ortho/para directing and the other 9 meta directing, besides the case of R = -H. Similar scaling patterns for these information-theoretic quantities found for stable species elsewhere were disclosed for these reactions systems. We also unveiled novel scaling patterns for information gain at the atomic level. The barrier height of the reactions can reliably be predicted by using both the Hirshfeld charge and information gain at the regioselective carbon atom. The energy decomposition analysis ensued yields an unambiguous picture about the origin of the barrier height, where we showed that it is the electrostatic interaction that plays the dominant role, while the roles played by exchange-correlation and

  6. Palladium-catalysed electrophilic aromatic C-H fluorination

    Science.gov (United States)

    Yamamoto, Kumiko; Li, Jiakun; Garber, Jeffrey A. O.; Rolfes, Julian D.; Boursalian, Gregory B.; Borghs, Jannik C.; Genicot, Christophe; Jacq, Jérôme; van Gastel, Maurice; Neese, Frank; Ritter, Tobias

    2018-02-01

    Aryl fluorides are widely used in the pharmaceutical and agrochemical industries, and recent advances have enabled their synthesis through the conversion of various functional groups. However, there is a lack of general methods for direct aromatic carbon-hydrogen (C-H) fluorination. Conventional methods require the use of either strong fluorinating reagents, which are often unselective and difficult to handle, such as elemental fluorine, or less reactive reagents that attack only the most activated arenes, which reduces the substrate scope. A method for the direct fluorination of aromatic C-H bonds could facilitate access to fluorinated derivatives of functional molecules that would otherwise be difficult to produce. For example, drug candidates with improved properties, such as increased metabolic stability or better blood-brain-barrier penetration, may become available. Here we describe an approach to catalysis and the resulting development of an undirected, palladium-catalysed method for aromatic C-H fluorination using mild electrophilic fluorinating reagents. The reaction involves a mode of catalysis that is unusual in aromatic C-H functionalization because no organometallic intermediate is formed; instead, a reactive transition-metal-fluoride electrophile is generated catalytically for the fluorination of arenes that do not otherwise react with mild fluorinating reagents. The scope and functional-group tolerance of this reaction could provide access to functional fluorinated molecules in pharmaceutical and agrochemical development that would otherwise not be readily accessible.

  7. The pi Complex of the Hydronium Ion Frozen on the Pathway of Electrophilic Aromatic Substitution

    Czech Academy of Sciences Publication Activity Database

    Růžičková, Z.; Holub, Josef; Melichar, Petr; Moncol, J.; Wann, D. A.; Fanfrlík, Jindřich; Růžička, A.; Hnyk, Drahomír

    2016-01-01

    Roč. 2016, č. 26 (2016), s. 4473-4475 ISSN 1434-193X R&D Projects: GA ČR(CZ) GBP208/12/G016 Institutional support: RVO:61388980 ; RVO:61388963 Keywords : Anions * Pi complexes * Electrophilic substitution * Quantum mechanics * Structure elucidation Subject RIV: CA - Inorganic Chemistry; CF - Physical ; Theoretical Chemistry (UOCHB-X) Impact factor: 2.834, year: 2016

  8. Synthesis of Fluoroalkoxy Substituted Arylboronic Esters by Iridium-Catalyzed Aromatic C–H Borylation

    KAUST Repository

    Batool, Farhat

    2015-08-17

    The preparation of fluoroalkoxy arylboronic esters by iridium-catalyzed aromatic C–H borylation is described. The fluoroalkoxy groups employed include trifluoromethoxy, difluoromethoxy, 1,1,2,2-tetrafluoroethoxy, and 2,2-difluoro-1,3-benzodioxole. The borylation reactions were carried out neat without the use of a glovebox or Schlenk line. The regioselectivities available through the iridium-catalyzed C–H borylation are complementary to those obtained by the electrophilic aromatic substitution reactions of fluoroalkoxy arenes. Fluoroalkoxy arylboronic esters can serve as versatile building blocks.

  9. Synthesis of Fluoroalkoxy Substituted Arylboronic Esters by Iridium-Catalyzed Aromatic C–H Borylation

    KAUST Repository

    Batool, Farhat; Parveen, Shehla; Emwas, Abdul-Hamid M.; Sioud, Salim; Gao, Xin; Munawar, Munawar A.; Chotana, Ghayoor A.

    2015-01-01

    The preparation of fluoroalkoxy arylboronic esters by iridium-catalyzed aromatic C–H borylation is described. The fluoroalkoxy groups employed include trifluoromethoxy, difluoromethoxy, 1,1,2,2-tetrafluoroethoxy, and 2,2-difluoro-1,3-benzodioxole. The borylation reactions were carried out neat without the use of a glovebox or Schlenk line. The regioselectivities available through the iridium-catalyzed C–H borylation are complementary to those obtained by the electrophilic aromatic substitution reactions of fluoroalkoxy arenes. Fluoroalkoxy arylboronic esters can serve as versatile building blocks.

  10. Synthesis of substituted tetrahydroisoquinolines by lithiation then electrophilic quench.

    Science.gov (United States)

    Talk, Ruaa A; Duperray, Alexia; Li, Xiabing; Coldham, Iain

    2016-06-07

    Substituted N-tert-butoxycarbonyl (Boc)-1,2,3,4-tetrahydroisoquinolines were prepared and treated with n-butyllithium in THF at -50 °C to test the scope of the metallation and electrophilic quench. The lithiation was optimised by using in situ ReactIR spectroscopy and the rate of rotation of the carbamate was determined. The 1-lithiated intermediates could be trapped with a variety of electrophiles to give good yields of 1-substituted tetrahydroisoquinoline products. Treatment with acid or reduction with LiAlH4 allows conversion to the N-H or N-Me compound. The chemistry was applied to the efficient total syntheses of the alkaloids (±)-crispine A and (±)-dysoxyline.

  11. Dramatic Influence of Ionic Liquid and Ultrasound Irradiation on the Electrophilic Sulfinylation of Aromatic Compounds by Sulfinic Esters

    DEFF Research Database (Denmark)

    Nguyen, Ngoc-Lan Thi; Vo, Hong-Thom; Duus, Fritz

    2017-01-01

    The sulfinylation reaction of aromatic and hetero-aromatic compounds with sulfinic esters as electrophiles has been investigated in different ionic liquids and by means of different Lewis acid salts in order to get moderate to good yields of asymmetrical sulfoxides. Mixtures of 1-butyl-3-methylim......The sulfinylation reaction of aromatic and hetero-aromatic compounds with sulfinic esters as electrophiles has been investigated in different ionic liquids and by means of different Lewis acid salts in order to get moderate to good yields of asymmetrical sulfoxides. Mixtures of 1-butyl-3...

  12. Crystal Structure, Conformational Analysis, and Charge Density Distribution for Eng-Epifisetinidol: An Explanation for Regiospecific Aromatic Substitution of 5-Deoxyflavan

    Science.gov (United States)

    Fred L. Tobiason; Frank R. Fronczek; Jan P. Steynberg; Elizabeth C. Steynberg; Richard W. Hemingway; Wayne L. Mattice

    1993-01-01

    Molecular modeling and molecular orbital analyses of ent-epifisetinidol gave &ood predictions of the approximate "reverse half-chair" conformation found for the crystal structure. MNDO and AM1 analyses of HOMO electron densities provided an explanation for the stereospecific electrophilic aromatic substitution at C(6) in 5-deoxy-flavans...

  13. Effects of Bentonite on p-Methoxybenzyl Acetate: A Theoretical Model for Oligomerization via an Electrophilic-Substitution Mechanism

    Directory of Open Access Journals (Sweden)

    Manuel Salmón

    2011-02-01

    Full Text Available Tonsil Actisil FF, a commercial bentonitic clay, promotes the formation of a series of electrophilic-aromatic-substitution products from para-methoxybenzyl acetate in carbon disulfide. The molecules obtained correspond to linear isomeric dimers, trimers, tetramers and a pentamer, according to their spectroscopic data. A clear indication of the title mechanistic pathway for the oligomerization growth was obtained from the analysis of a set of computational-chemistry calculations using the density-functional-theory level B3LYP/6-311++G(d,p. The corresponding conclusions were based on the computed dipole moments, the HOMO/LUMO distributions, and a natural-populations analysis of the studied molecules.

  14. Utilizing the σ-complex stability for quantifying reactivity in nucleophilic substitution of aromatic fluorides

    Directory of Open Access Journals (Sweden)

    Magnus Liljenberg

    2013-04-01

    Full Text Available A computational approach using density functional theory to compute the energies of the possible σ-complex reaction intermediates, the “σ-complex approach”, has been shown to be very useful in predicting regioselectivity, in electrophilic as well as nucleophilic aromatic substitution. In this article we give a short overview of the background for these investigations and the general requirements for predictive reactivity models for the pharmaceutical industry. We also present new results regarding the reaction rates and regioselectivities in nucleophilic substitution of fluorinated aromatics. They were rationalized by investigating linear correlations between experimental rate constants (k from the literature with a theoretical quantity, which we call the sigma stability (SS. The SS is the energy change associated with formation of the intermediate σ-complex by attachment of the nucleophile to the aromatic ring. The correlations, which include both neutral (NH3 and anionic (MeO− nucleophiles are quite satisfactory (r = 0.93 to r = 0.99, and SS is thus useful for quantifying both global (substrate and local (positional reactivity in SNAr reactions of fluorinated aromatic substrates. A mechanistic analysis shows that the geometric structure of the σ-complex resembles the rate-limiting transition state and that this provides a rationale for the observed correlations between the SS and the reaction rate.

  15. Development of selective colorimetric probes for hydrogen sulfide based on nucleophilic aromatic substitution.

    Science.gov (United States)

    Montoya, Leticia A; Pearce, Taylor F; Hansen, Ryan J; Zakharov, Lev N; Pluth, Michael D

    2013-07-05

    Hydrogen sulfide is an important biological signaling molecule and an important environmental target for detection. A major challenge in developing H2S detection methods is separating the often similar reactivity of thiols and other nucleophiles from H2S. To address this need, the nucleophilic aromatic substitution (SNAr) reaction of H2S with electron-poor aromatic electrophiles was developed as a strategy to separate H2S and thiol reactivity. Treatment of aqueous solutions of nitrobenzofurazan (7-nitro-1,2,3-benzoxadiazole, NBD) thioethers with H2S resulted in thiol extrusion and formation of nitrobenzofurazan thiol (λmax = 534 nm). This reactivity allows for unwanted thioether products to be converted to the desired nitrobenzofurazan thiol upon reaction with H2S. The scope of the reaction was investigated using a Hammett linear free energy relationship study, and the determined ρ = +0.34 is consistent with the proposed SN2Ar reaction mechanism. The efficacy of the developed probes was demonstrated in buffer and in serum with associated submicromolar detection limits as low as 190 nM (buffer) and 380 nM (serum). Furthermore, the sigmoidal response of nitrobenzofurazan electrophiles with H2S can be fit to accurately quantify H2S. The developed detection strategy offers a manifold for H2S detection that we foresee being applied in various future applications.

  16. Reactivity of polychlorinated biphenyls in nucleophilic and electrophilic substitutions

    Energy Technology Data Exchange (ETDEWEB)

    Gorbunova, Tatyana I., E-mail: gorbunova@ios.uran.ru [I. Ya. Postovskii Institute of Organic Synthesis, Ural Branch, Russian Academy of Sciences, Kovalevskoy St., 22, Ekaterinburg 620990 (Russian Federation); Subbotina, Julia O. [Ural Federal University named after the first President of Russia B.N. Yeltsin, Mira St., 19, Ekaterinburg 620002 (Russian Federation); Saloutin, Viktor I.; Chupakhin, Oleg N. [I. Ya. Postovskii Institute of Organic Synthesis, Ural Branch, Russian Academy of Sciences, Kovalevskoy St., 22, Ekaterinburg 620990 (Russian Federation)

    2014-08-15

    Graphical abstract: - Highlights: • Quantum chemical calculations were carried out for PCBs congeners. • Calculated descriptors were used to explain the PCBs reactivity in S{sub N} and S{sub E} substitutions. • Obtained data were used to estimate the PCBs reactivity in the S{sub N} reactions. • Calculated descriptors were insufficient to explain the PCBs reactivity in the S{sub E} reactions. • New neutralization methods of the large-capacity PCBs were discussed. - Abstract: To explain the chemical reactivity of polychlorinated biphenyls in nucleophilic (S{sub N}) and electrophilic (S{sub E}) substitutions, quantum chemical calculations were carried out at the B3LYP/6-31G(d) level of the Density Functional Theory in gas phase. Carbon atomic charges in biphenyl structure were calculated by the Atoms-in-Molecules method. Chemical hardness and global electrophilicity index parameters were determined for congeners. A comparison of calculated descriptors and experimental data for congener reactivity in the S{sub N} and S{sub E} reactions was made. It is shown that interactions in the S{sub N} mechanism are reactions of the hard acid–hard base type, these are the most effective in case of highly chlorinated substrates. To explain the congener reactivity in the S{sub E} reactions, correct descriptors were not established. The obtained results can be used to carry out chemical transformations of the polychlorinated biphenyls in order to prepare them for microbiological destruction or preservation.

  17. A Multistep Synthesis Incorporating a Green Bromination of an Aromatic Ring

    Science.gov (United States)

    Cardinal, Pascal; Greer, Brandon; Luong, Horace; Tyagunova, Yevgeniya

    2012-01-01

    Electrophilic aromatic substitution is a fundamental topic taught in the undergraduate organic chemistry curriculum. A multistep synthesis that includes a safer and greener method for the bromination of an aromatic ring than traditional bromination methods is described. This experiment is multifaceted and can be used to teach students about…

  18. The future role of aromatics in refining and petrochemistry. Proceedings of the DGMK-Conference (Authors' manuscripts)

    Energy Technology Data Exchange (ETDEWEB)

    Emig, G.; Rupp, M.; Weitkamp, J. [eds.

    1999-07-01

    Topic of this conference has been the furure role of aromatics in the refinign industry. The articles deal with the following topics: Refining; legal aspects in the aromatics market; transportation fuels; dearomatization; catalytic reforming and aromatics; separation processes for aromatics; oxidation and ammoxidation of aromatics; electrophilic substitution of aromatics; hydrogenation of benzene; zeolites. (orig./sr)

  19. Kinetics of electrophilic substitution of neodymium(III) by ytterbium(III) in aqueous solutions of ethylenediamintetraacetate and cyclohexanediaminetetraacetate

    International Nuclear Information System (INIS)

    Nikitenko, S.I.; Martynenko, L.I.; Pechurova, N.I.; Spitsyn, V.I.

    1982-01-01

    The kinetics of electrophilic substitution in systems containing rare earth element ions (REE) and Komplexon [tetrasodium ethylenediaminetetraacetate] have been studied little. At the same time, information about the mechanism of exchange is not only of theoretical interest but is important for the optimization of processes for separating and purifying REE. Least studied of all has been the mutual exchange in Komplexonate ions of light and heavy REE, although it is precisely the kinetics of exchange of different kinds of REE ions that primarily determines the effectiveness of the separation of their mixtures. We have studied electrophilic substitution in the case of the replacement of neodymium(III) by ytterbium(III) in solutions containing NdL - and Yb 3 + , where L 4 - and D 4 -

  20. Dramatic Influence of Ionic Liquid and Ultrasound Irradiation on the Electrophilic Sulfinylation of Aromatic Compounds by Sulfinic Esters

    Directory of Open Access Journals (Sweden)

    Ngoc-Lan Thi Nguyen

    2017-09-01

    Full Text Available The sulfinylation reaction of aromatic and hetero-aromatic compounds with sulfinic esters as electrophiles has been investigated in different ionic liquids and by means of different Lewis acid salts in order to get moderate to good yields of asymmetrical sulfoxides. Mixtures of 1-butyl-3-methylimidazolium chloride and aluminum chloride were found to be the most efficient and recyclable reaction framework. Ultrasound sonication appeared to be the most useful and green activation method to afford the sulfoxides in yields better than or equivalent to those obtained under the longer-lasting conventional stirring conditions.

  1. Cation Radical Accelerated Nucleophilic Aromatic Substitution via Organic Photoredox Catalysis.

    Science.gov (United States)

    Tay, Nicholas E S; Nicewicz, David A

    2017-11-15

    Nucleophilic aromatic substitution (S N Ar) is a direct method for arene functionalization; however, it can be hampered by low reactivity of arene substrates and their availability. Herein we describe a cation radical-accelerated nucleophilic aromatic substitution using methoxy- and benzyloxy-groups as nucleofuges. In particular, lignin-derived aromatics containing guaiacol and veratrole motifs were competent substrates for functionalization. We also demonstrate an example of site-selective substitutive oxygenation with trifluoroethanol to afford the desired trifluoromethylaryl ether.

  2. Photoinduced intramolecular substitution reaction of aryl halide with carbonyl oxygen of amide group

    CERN Document Server

    Park, Y T; Kim, M S; Kwon, J H

    2002-01-01

    Photoreaction of N-(o-halophenyl)acetamide in basic acetonitrile produces an intramolecular substituted product, 2-methylbenzoxazole in addition to reduced product, acetanilide, whereas photoreaction of N-(o-halobenzyl)acetamide affords a reduced product, N-benzylacetamide only. On the basis of preparative reaction, kinetics, and UV/vis absorption behavior, an electrophilic aromatic substitution of aryl halide with oxygen of its amide bond are proposed.

  3. Photoinduced intramolecular substitution reaction of aryl halide with carbonyl oxygen of amide group

    Energy Technology Data Exchange (ETDEWEB)

    Park, Yong Tae; Song, Myong Geun; Kim, Moon Sub; Kwon, Jeong Hee [Kyungpook National Univ., Daegu (Korea, Republic of)

    2002-09-01

    Photoreaction of N-(o-halophenyl)acetamide in basic acetonitrile produces an intramolecular substituted product, 2-methylbenzoxazole in addition to reduced product, acetanilide, whereas photoreaction of N-(o-halobenzyl)acetamide affords a reduced product, N-benzylacetamide only. On the basis of preparative reaction, kinetics, and UV/vis absorption behavior, an electrophilic aromatic substitution of aryl halide with oxygen of its amide bond are proposed.

  4. Photoinduced intramolecular substitution reaction of aryl halide with carbonyl oxygen of amide group

    International Nuclear Information System (INIS)

    Park, Yong Tae; Song, Myong Geun; Kim, Moon Sub; Kwon, Jeong Hee

    2002-01-01

    Photoreaction of N-(o-halophenyl)acetamide in basic acetonitrile produces an intramolecular substituted product, 2-methylbenzoxazole in addition to reduced product, acetanilide, whereas photoreaction of N-(o-halobenzyl)acetamide affords a reduced product, N-benzylacetamide only. On the basis of preparative reaction, kinetics, and UV/vis absorption behavior, an electrophilic aromatic substitution of aryl halide with oxygen of its amide bond are proposed

  5. Kinetics of electrophilic substitution of neodymium(3) by ytterbium(3) in aqueous solution of ethylenediaminetetraacetate solution of ethylenediaminetetraacetate and cyclohexanediaminetetraacetate

    Energy Technology Data Exchange (ETDEWEB)

    Nikitenko, S.I.; Martynenko, L.I.; Pechurova, N.I.; Spitsyn, V.I. (Moskovskij Gosudarstvennyj Univ. (USSR))

    1981-01-01

    The process of electrophilic substitution is studied spectrophotometrically taking as an example neodymium (3) substitution for ytterbium (3) in solutions, containing NdL/sup -/ and Yb/sup 3 +/, where L/sup 4 -/ = A/sup 4 -/ and D/sup 4 -/ (ethylenediaminetetraacetate- and cyclohexanediaminetetraacetate). The study of the exchange kinetics is carried out in pH range of 4-6. For the system with L=A in pH range 4.0-4.8 the exchange is realized by the way of acidic dissociation, at pH 5.5-6.0 - by the way of the direct attack. In the system with L=D in pH range 3.5-4.0 the way of acid dissociation prevails, at the same time, the rate constant of acidic dissociation for NdD/sup -/ is two order lower the constant for NdA/sup -/. However, at pH 4.7 the machanism of spontaneous dissociation prevails in the system. Thus, the structure of the complex has considerable effect on the mechanism of electrophilic substitution in rare earth complexes.

  6. Kinetics of electrophilic substitution of neodymium(3) by ytterbium(3) in aqueous solution of ethylenediaminetetraacetate solution of ethylenediaminetetraacetate and cyclohexanediaminetetraacetate

    International Nuclear Information System (INIS)

    Nikitenko, S.I.; Martynenko, L.I.; Pechurova, N.I.; Spitsyn, V.I.

    1981-01-01

    The process of electrophilic substitution is studied spectrophotometrically taking as an example neodymium (3) substitution for ytterbium (3) in solutions, containing NdL - and Yb 3+ , where L 4- = A 4- and D 4- (ethylenediaminetetraacetate- and cyclohexanediaminetetraacetate). The study of the exchange kinetics is carried out in pH range of 4-6. For the system with L=A in pH range 4.0-4.8 the exchange is realized by the way of acidic dissociation, at pH 5.5-6.0 - by the way of the direct attack. In the system with L=D in pH range 3.5-4.0 the way of acid dissociation prevails, at the same time, the rate constant of acidic dissociation for NdD - is two order lower the constant for NdA - . However, at pH 4.7 the machanism of spontaneous dissociation prevails in the system. Thus, the structure of the complex has considerable effect on the mechanism of electrophilic substitution in rare earth complexes [ru

  7. Continuous Flow Nucleophilic Aromatic Substitution with Dimethylamine Generated in Situ by Decomposition of DMF

    DEFF Research Database (Denmark)

    Petersen, Trine P; Larsen, Anders Foller; Ritzén, Andreas

    2013-01-01

    A safe, practical, and scalable continuous flow protocol for the in situ generation of dimethylamine from DMF followed by nucleophilic aromatic substitution of a broad range of aromatic and heteroaromatic halides is reported.......A safe, practical, and scalable continuous flow protocol for the in situ generation of dimethylamine from DMF followed by nucleophilic aromatic substitution of a broad range of aromatic and heteroaromatic halides is reported....

  8. Chiral 2-Aminobenzimidazole as Bifunctional Catalyst in the Asymmetric Electrophilic Amination of Unprotected 3-Substituted Oxindoles

    Directory of Open Access Journals (Sweden)

    Llorenç Benavent

    2018-06-01

    Full Text Available The use of readily available chiral trans-cyclohexanediamine-benzimidazole derivatives as bifunctional organocatalysts in the asymmetric electrophilic amination of unprotected 3-substituted oxindoles is presented. Different organocatalysts were evaluated; the most successful one contained a dimethylamino moiety (5. With this catalyst under optimized conditions, different oxindoles containing a wide variety of substituents at the 3-position were aminated in good yields and with good to excellent enantioselectivities using di-tert-butylazodicarboxylate as the aminating agent. The procedure proved to be also efficient for the amination of 3-substituted benzofuranones, although with moderate results. A bifunctional role of the catalyst, acting as Brønsted base and hydrogen bond donor, is proposed according to the experimental results observed.

  9. Hydroxylation of p-substituted phenols by tyrosinase: Further insight into the mechanism of tyrosinase activity

    International Nuclear Information System (INIS)

    Muñoz-Muñoz, Jose Luis; Berna, Jose; García-Molina, María del Mar; Garcia-Molina, Francisco; Garcia-Ruiz, Pedro Antonio; Varon, Ramon

    2012-01-01

    Highlights: ► The action the copper complexes and tyrosinase on phenols is equivalent. ► Isotope effect showed that nucleophilic attack to copper atom may be the slower step. ► The value of ρ (Hammett constant) supports an electrophilic aromatic substitution. ► Data obtained in steady state pH 7 conditions support the mechanism of Scheme 1SM. -- Abstract: A study of the monophenolase activity of tyrosinase by measuring the steady state rate with a group of p-substituted monophenols provides the following kinetic information: k cat m and the Michaelis constant, K M m . Analysis of these data taking into account chemical shifts of the carbon atom supporting the hydroxyl group (δ) and σ p + , enables a mechanism to be proposed for the transformation of monophenols into o-diphenols, in which the first step is a nucleophilic attack on the copper atom on the form E ox (attack of the oxygen of the hydroxyl group of C-1 on the copper atom) followed by an electrophilic attack (attack of the hydroperoxide group on the ortho position with respect to the hydroxyl group of the benzene ring, electrophilic aromatic substitution with a reaction constant ρ of −1.75). These steps show the same dependency on the electronic effect of the substituent groups in C-4. Furthermore, a study of a solvent deuterium isotope effect on the oxidation of monophenols by tyrosinase points to an appreciable isotopic effect. In a proton inventory study with a series of p-substituted phenols, the representation of k cat f n /k cat f 0 against n (atom fractions of deuterium), where k cat f n is the catalytic constant for a molar fraction of deuterium (n) and k cat f 0 is the corresponding kinetic parameter in a water solution, was linear for all substrates. These results indicate that only one of the proton transfer processes from the hydroxyl groups involved the catalytic cycle is responsible for the isotope effects. We suggest that this step is the proton transfer from the hydroxyl group

  10. Substituted Phthalic Anhydrides from Biobased Furanics : A New Approach to Renewable Aromatics

    NARCIS (Netherlands)

    Thiyagarajan, Shanmugam; Genuino, Homer C.|info:eu-repo/dai/nl/371571685; Sliwa, Michal; van der Waal, Jan C.; de Jong, Ed; van Haveren, Jacco; Weckhuysen, Bert M.|info:eu-repo/dai/nl/285484397; Bruijnincx, Pieter C. A.|info:eu-repo/dai/nl/33799529X; van Es, Daan S.

    2015-01-01

    A novel route for the production of renewable aromatic chemicals, particularly substituted phthalic acid anhydrides, is presented. The classical two-step approach to furanics-derived aromatics via Diels-Alder (DA) aromatization has been modified into a three-step procedure to address the general

  11. Effect of substituent structure on pyrimidine electrophilic substitution

    CSIR Research Space (South Africa)

    Van der Westhuyzen, CW

    2007-01-01

    Full Text Available In an investigation into the electrophilic nitrosation reactions of a series of 4,6-disubstituted pyrimidine derivatives, a subtle interplay between the electronic nature of the C-4 and C-6 substituents and reactivity was found where these were...

  12. Evidence for an Intermediate in the Methylation of CB11H12- with Methyl Triflate: Comparison of Electrophilic Substitution in Cage Boranes and in Arenes

    Czech Academy of Sciences Publication Activity Database

    Kaleta, Jiří; Akdag, Akin; Crespo, R.; Piqueras, M. C.; Michl, Josef

    2013-01-01

    Roč. 78, č. 9 (2013), s. 1174-1183 ISSN 2192-6506 Institutional support: RVO:61388963 Keywords : alkylation * boranes * carboranes * electrophilic substitution * hydrogen scrambling Subject RIV: CC - Organic Chemistry Impact factor: 3.242, year: 2013

  13. Alkyne Benzannulation Reactions for the Synthesis of Novel Aromatic Architectures.

    Science.gov (United States)

    Hein, Samuel J; Lehnherr, Dan; Arslan, Hasan; J Uribe-Romo, Fernando; Dichtel, William R

    2017-11-21

    Aromatic compounds and polymers are integrated into organic field effect transistors, light-emitting diodes, photovoltaic devices, and redox-flow batteries. These compounds and materials feature increasingly complex designs, and substituents influence energy levels, bandgaps, solution conformation, and crystal packing, all of which impact performance. However, many polycyclic aromatic hydrocarbons of interest are difficult to prepare because their substitution patterns lie outside the scope of current synthetic methods, as strategies for functionalizing benzene are often unselective when applied to naphthalene or larger systems. For example, cross-coupling and nucleophilic aromatic substitution reactions rely on prefunctionalized arenes, and even directed metalation methods most often modify positions near Lewis basic sites. Similarly, electrophilic aromatic substitutions access single regioisomers under substrate control. Cycloadditions provide a convergent route to densely functionalized aromatic compounds that compliment the above methods. After surveying cycloaddition reactions that might be used to modify the conjugated backbone of poly(phenylene ethynylene)s, we discovered that the Asao-Yamamoto benzannulation reaction is notably efficient. Although this reaction had been reported a decade earlier, its scope and usefulness for synthesizing complex aromatic systems had been under-recognized. This benzannulation reaction combines substituted 2-(phenylethynyl)benzaldehydes and substituted alkynes to form 2,3-substituted naphthalenes. The reaction tolerates a variety of sterically congested alkynes, making it well-suited for accessing poly- and oligo(ortho-arylene)s and contorted hexabenzocoronenes. In many cases in which asymmetric benzaldehyde and alkyne cycloaddition partners are used, the reaction is regiospecific based on the electronic character of the alkyne substrate. Recognizing these desirable features, we broadened the substrate scope to include silyl

  14. Adsorption of polar, nonpolar, and substituted aromatics to colloidal graphene oxide nanoparticles

    NARCIS (Netherlands)

    Wang, Fang; Haftka, Joris J H; Sinnige, Theo L.; Hermens, Joop L M; Chen, Wei

    2014-01-01

    We conducted batch adsorption experiments to understand the adsorptive properties of colloidal graphene oxide nanoparticles (GONPs) for a range of environmentally relevant aromatics and substituted aromatics, including model nonpolar compounds (pyrene, phenanthrene, naphthalene, and

  15. Hydroxylation of p-substituted phenols by tyrosinase: Further insight into the mechanism of tyrosinase activity

    Energy Technology Data Exchange (ETDEWEB)

    Munoz-Munoz, Jose Luis [GENZ - Grupo de Investigacion Enzimologia, Departamento de Bioquimica y Biologia Molecular-A, Facultad de Biologia, Campus Internacional de Excelencia Campus Mare Nostrum, Universidad de Murcia, E-30100 Espinardo, Murcia (Spain); Berna, Jose [Grupo de Quimica Organica Sintetica, Departamento de Quimica Organica, Facultad de Quimica Campus Internacional de Excelencia Campus Mare Nostrum, Universidad de Murcia (Spain); Garcia-Molina, Maria del Mar; Garcia-Molina, Francisco [GENZ - Grupo de Investigacion Enzimologia, Departamento de Bioquimica y Biologia Molecular-A, Facultad de Biologia, Campus Internacional de Excelencia Campus Mare Nostrum, Universidad de Murcia, E-30100 Espinardo, Murcia (Spain); Garcia-Ruiz, Pedro Antonio [QCPAI - Grupo de Quimica de Carbohidratos, Polimeros y Aditivos Industriales, Departamento de Quimica Organica, Facultad de Quimica Campus Internacional de Excelencia Campus Mare Nostrum, Universidad de Murcia (Spain); Varon, Ramon [Departamento de Quimica-Fisica, Escuela de Ingenieros Industriales de Albacete, Universidad de Castilla la Mancha, Avda. Espana s/n. Campus Universitario, E-02071 Albacete (Spain); and others

    2012-07-27

    Highlights: Black-Right-Pointing-Pointer The action the copper complexes and tyrosinase on phenols is equivalent. Black-Right-Pointing-Pointer Isotope effect showed that nucleophilic attack to copper atom may be the slower step. Black-Right-Pointing-Pointer The value of {rho} (Hammett constant) supports an electrophilic aromatic substitution. Black-Right-Pointing-Pointer Data obtained in steady state pH 7 conditions support the mechanism of Scheme 1SM. -- Abstract: A study of the monophenolase activity of tyrosinase by measuring the steady state rate with a group of p-substituted monophenols provides the following kinetic information: k{sub cat}{sup m} and the Michaelis constant, K{sub M}{sup m}. Analysis of these data taking into account chemical shifts of the carbon atom supporting the hydroxyl group ({delta}) and {sigma}{sub p}{sup +}, enables a mechanism to be proposed for the transformation of monophenols into o-diphenols, in which the first step is a nucleophilic attack on the copper atom on the form E{sub ox} (attack of the oxygen of the hydroxyl group of C-1 on the copper atom) followed by an electrophilic attack (attack of the hydroperoxide group on the ortho position with respect to the hydroxyl group of the benzene ring, electrophilic aromatic substitution with a reaction constant {rho} of -1.75). These steps show the same dependency on the electronic effect of the substituent groups in C-4. Furthermore, a study of a solvent deuterium isotope effect on the oxidation of monophenols by tyrosinase points to an appreciable isotopic effect. In a proton inventory study with a series of p-substituted phenols, the representation of k{sub cat}{sup f{sub n}}/k{sub cat}{sup f{sub 0}} against n (atom fractions of deuterium), where k{sub cat}{sup f{sub n}} is the catalytic constant for a molar fraction of deuterium (n) and k{sub cat}{sup f{sub 0}} is the corresponding kinetic parameter in a water solution, was linear for all substrates. These results indicate that

  16. Experimental Determination of Activation Energy of Nucleophilic Aromatic Substitution on Porphyrins

    Science.gov (United States)

    Rizvi, Waqar; Khwaja, Emaad; Siddiqui, Saim; Bhupathiraju, N. V. S. Dinesh K.; Drain, Charles Michael

    2018-01-01

    A physical organic chemistry experiment is described for second-year college students. Students performed nucleophilic aromatic substitution (NAS) reactions on 5,10,15,20-tetrakis(2,3,4,5,6-pentafluorophenyl)porphyrin (TPPF[subscript 20]) using three different nucleophiles. Substitution occurs preferentially at the 4-position ("para")…

  17. Kinetics of electrophilic substitution of erbium (3) for ytterbium (3) in aqueous solution of ethylenediaminetetraacetate

    Energy Technology Data Exchange (ETDEWEB)

    Nikitenko, S.I.; Martynenko, L.I.; Pechurova, N.I.; Spitsyn, V.I. (Moskovskij Gosudarstvennyj Univ. (USSR))

    1983-08-01

    The results obtained while studing the exchange kinetics in the ErA/sup -/ - Yb/sup 3 +/ system are compared with the kinetic regularities found for the NdA/sup -/ - Yb/sup 3 +/ system. Electrophilic substitution in ethylenediamine tetraacetates of rare earths (3) independently of the nature of a departing cation is realized through two competitive mechanisms: acid dissociation and associative mechanisms. Exchange through the acid dissociation mechanisms is catalized by protons while, depending on the medium acidity, mono- and biprotonated intermediate complexes are formed. The associative mechanism predominates in less acid media and is realized through the formation of intermediate binuclear complexes. The limiting exchange stage is a break in the metal-nitrogen bond formed by the departing cation and ligand in the intermediate binuclear complex.

  18. Kinetics of electrophilic substitution of erbium (3) for ytterbium (3) in aqueous solution of ethylenediaminetetraacetate

    International Nuclear Information System (INIS)

    Nikitenko, S.I.; Martynenko, L.I.; Pechurova, N.I.; Spitsyn, V.I.

    1983-01-01

    The results obtained while stUdying the exchange kinetics in the ErA - - Yb 3+ system are compared with the kinetic regularities found for the NdA - - Yb 3+ system. Electrophilic substitution in ethylenediamine tetraacetates of rare earths (3) independently of the nature of a departing cation is realized through two competitive mechanisms: acid dissociation and associatiVe mechanisms. Exchange through the acid dissociation mechanisms is catalized by protons while, depending on the medium acidity, mono- and biprotonated intermediate complexes are formed. The associative mechanism predominates in less acid media and is realized through the formation of intermediate binOclear compleXes. The limiting exchange stage is a break in the metal-nitrogen bond formed by the departing cation and ligand in the intermediate binUclear complex

  19. Quantum-chemical investigation of the 1,2-proton shift in protonated five-membered aromatic heterocycles

    International Nuclear Information System (INIS)

    Abronin, I.A.; Gorb, L.G.; Litvinov, V.P.

    1985-01-01

    Calculations of the energetics of the 1,2-proton shift in protonated five-membered aromatic heterocycles - pyrrole, furan, and thiophene - have been carried out by the SCF MO LCAO method in the MINDO/3 approximation and nonempirically on the OST-3GF (OST-3GF) basis. The general features of this process, and also the influence of solvation and of taking into account the vacant d-AOs of the sulfur atom in the protonated form of thiophene on the results of the calculation are considered. The results obtained have been used for a discussion of the activity and selectivity of the heterocycles considered in aromatic electrophilic substitution reactions

  20. Potentiometric titrations of para and nitro substituted aromatic acids and their mixtures in methylethyl ketone

    International Nuclear Information System (INIS)

    Ozeroglu, C.; Karahan, M.

    2011-01-01

    In this study, it was the purpose to examine the potentiometric titrations of para and nitro substituted aromatic acids in methylethyl ketone (MEK) as a non-aqueous solvent. Good analytical results were obtained in determining the amount of each acid and the amounts of acids in their ternary mixtures by using 0.0964 N tetrabuthylammoniumhydroxyde (TBAH) as a standard titrant. Methylethyl ketone (MEK) which is a good solvent for many organic compounds and has a convenient liquid range of -86 to 80 deg. C was used for titration of the para and nitro substituted aromatic acids. A linear relationship has been found between pKa values of the para and nitro substituted aromatic acids in water and the half neutralization potential (HNP) values determined by potentiometric titration curves of the same acids in MEK. (author)

  1. Aromatic C-nitrosation of a bioactive molecule. Nitrosation of minoxidil.

    Science.gov (United States)

    González-Jiménez, Mario; Arenas-Valgañón, Jorge; Calle, Emilio; Casado, Julio

    2011-10-26

    Minoxidil (2,4-diamino-6-(piperidin-1'-yl)pyrimidine N(3)-oxide; CASRN 38304-91-5) is a bioactive molecule with several nitrosatable groups widely used as an antihypertensive and antialopecia agent. Here the nitrosation of minoxidil was investigated. The conclusions drawn are as follows: (i) In the pH = 2.3-5.0 range, the minoxidil molecule undergoes aromatic C-nitrosation by nitrite. The dominant reaction was C-5 nitrosation through a mechanism that appears to consist of an electrophilic attack on the nitrosatable substrate by H(2)NO(2)(+)/NO(+), followed by a slow proton transfer; (ii) the reactivity of minoxidil as a C-nitrosatable substrate proved to be 7-fold greater than that of phenol, this being attributed to the preferred para- and ortho-orientations of the two -NH(2) groups at positions 2 and 4 of the minoxidil molecule, which activate electrophilic substitution in the C-5 position through their mesomeric effect. The N-nitrosominoxidil resulting from the nitrosation could be potentially harmful to the minoxidil users.

  2. Reactivity Of Radiolytically-Produced Nitrogen Oxide Radicals Toward Aromatic Compounds

    International Nuclear Information System (INIS)

    Elias, Gracy

    2010-01-01

    radiolysis of the modifier (Cs-7SB), which solvates both metal complexes, is responsible for this change. These reactions presumably occur due to reactions with radiolytically-produced nitrogen-centered radicals like (sm b ullet)NO, (sm b ullet)NO 2 and (sm b ullet)NO 3 . Anisole (C 6 H 5 -OCH 3 ) was used in this study as a surrogate for Cs-7SB, since both are aryl ethers. Toluene was used as a surrogate for Cs-7SB because of the alkyl group on the benzene ring in both molecules. Anisole, highly reactive in acids, is a small molecule compared to Cs-7SB and the nitration products are easier to identify compared to those for the larger Cs-7SB molecule. Toluene is less reactive than anisole. Therefore, the highly reactive anisole and the less reactive toluene were considered in this study as model compounds to compare the reaction mechanisms and the nitrated products in acidic media under irradiation. Experiments were designed to elucidate the mechanism of the nitration of aromatic rings in γ-irradiated aqueous nitric acid. Since a suite of radical and ionic reactive species are produced in this condensed-phase system, solutions of nitric acid, neutral nitrate and neutral nitrite were irradiated in separate experiments to isolate selected reactive species. Product nitration species were assessed by high performance liquid chromatography (HPLC) with a reversed phase C-18 column and photodiode array detector. The nitrated anisole product distributions were the same with and without radiation in acidic solution, although more products were formed with radiation. In the irradiated acidic condensed phase, radiation-enhanced nitrous acid-catalyzed nitrosonium ion electrophilic aromatic substitution followed by oxidation reactions dominated over radical addition reactions. In contrast, the distribution of nitrated derivatives for toluene showed nitronium ion electrophilic substitution in the unirradiated acidic medium as a result of thermal nitration only at elevated temperatures

  3. Synthesis and nucleophilic aromatic substitution of 3-fluoro-5-nitro-1-(pentafluorosulfanyl)benzene

    Czech Academy of Sciences Publication Activity Database

    Ajenjo, Javier; Greenhall, M.; Zarantonello, C.; Beier, Petr

    2016-01-01

    Roč. 12, Feb 3 (2016), s. 192-197 ISSN 1860-5397 EU Projects: European Commission(XE) 607787 - FLUOR21 Institutional support: RVO:61388963 Keywords : direct fluorination * fluorine * nucleophilic aromatic substitution * pentafluorosulfanyl group * vicarious nucleophilic substitution Subject RIV: CC - Organic Chemistry Impact factor: 2.337, year: 2016 http://www.beilstein-journals.org/bjoc/single/articleFullText.htm?publicId=1860-5397-12-21

  4. Catalytic Ketone Hydrodeoxygenation Mediated by Highly Electrophilic Phosphonium Cations.

    Science.gov (United States)

    Mehta, Meera; Holthausen, Michael H; Mallov, Ian; Pérez, Manuel; Qu, Zheng-Wang; Grimme, Stefan; Stephan, Douglas W

    2015-07-06

    Ketones are efficiently deoxygenated in the presence of silane using highly electrophilic phosphonium cation (EPC) salts as catalysts, thus affording the corresponding alkane and siloxane. The influence of distinct substitution patterns on the catalytic effectiveness of several EPCs was evaluated. The deoxygenation mechanism was probed by DFT methods. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Facile on-site detection of substituted aromatic pollutants in water using thin layer chromatography combined with surface-enhanced Raman spectroscopy.

    Science.gov (United States)

    Li, Dawei; Qu, Lulu; Zhai, Wenlei; Xue, Jinqun; Fossey, John S; Long, Yitao

    2011-05-01

    A novel facile method for on-site detection of substituted aromatic pollutants in water using thin layer chromatography (TLC) combined with surface-enhanced Raman spectroscopy (SERS) was explored. Various substituted aromatics in polluted water were separated by a convenient TLC protocol and then detected using a portable Raman spectrometer with the prepared silver colloids serving as SERS-active substrates. The effects of operating conditions on detection efficacy were evaluated, and the application of TLC-SERS to on-site detection of artificial and real-life samples of aromatics/polluted water was systematically investigated. It was shown that commercially available Si 60-F(254) TLC plates were suitable for separation and displayed low SERS background and good separation efficiency, 2 mM silver colloids, 20 mM NaCl (working as aggregating agent), 40 mW laser power, and 50 s intergration time were appropriate for the detection regime. Furthermore, qualitative and quantitative detection of most of substituted aromatic pollutants was found to be readily accomplished using the developed TLC-SERS technique, which compared well with GC-MS in terms of identification ability and detection accuracy, and a limit of detection (LOD) less than 0.2 ppm (even at ppb level for some analytes) could be achieved under optimal conditions. The results reveal that the presented convenient method could be used for the effective separation and detection of the substituted aromatic pollutants of water on site, thus reducing possible influences of sample transportation and contamination while shortening the overall analysis time for emergency and routine monitoring of the substituted aromatics/polluted water.

  6. Titanocene(III)-Catalyzed Three-Component Reaction of Secondary Amides, Aldehydes, and Electrophilic Alkenes.

    Science.gov (United States)

    Zheng, Xiao; He, Jiang; Li, Heng-Hui; Wang, Ao; Dai, Xi-Jie; Wang, Ai-E; Huang, Pei-Qiang

    2015-11-09

    An umpolung Mannich-type reaction of secondary amides, aliphatic aldehydes, and electrophilic alkenes has been disclosed. This reaction features the one-pot formation of C-N and C-C bonds by a titanocene-catalyzed radical coupling of the condensation products, from secondary amides and aldehydes, with electrophilic alkenes. N-substituted γ-amido-acid derivatives and γ-amido ketones can be efficiently prepared by the current method. Extension to the reaction between ketoamides and electrophilic alkenes allows rapid assembly of piperidine skeletons with α-amino quaternary carbon centers. Its synthetic utility has been demonstrated by a facile construction of the tricyclic core of marine alkaloids such as cylindricine C and polycitorol A. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Theoretical and conceptual density functional theory (DFT) study on selectivity of 4-hydroxyquinazoline electrophilic aromatic nitration

    Science.gov (United States)

    Makhloufi, A.; Belhadad, O.; Ghemit, R.; Baitiche, M.; Merbah, M.; Benachour, DJ.

    2018-01-01

    In common with other aza-heterocycles, 4-hydroxyquinazoline and their derivatives are important pharmacophores and versatile lead molecule used in several specific biological activities. The potency of these compounds depends on the nature and/or position of their substituents. In this paper, we report a theoretical study of the most probable nitration reaction centers of 4-hydroxyquinazoline for electrophilic attack, the mono and di-nitration was also discussed. In parallel, a computational study has been performed in gas by using the B3LYP/6311 G(d) level. The stability of the four nitro isomers is rationalized by means of the global index and local reactivity indices. Their molecular electrostatic potential (MEP) and Milliken charge were explored. Molecular geometries and NMR H spectra was examined. In addition, stationary points of reactant, transition state and intermediate were optimized in water condensed phase at the same level. The relative energies of the regioisomeric δ-complexes confirm that the substitution at C6 (6-nitro σ-complexes) is favored in these conditions, what was in agreement with our others calculating results (in gas).

  8. A Theoretical Study of the Relationship between the Electrophilicity ω Index and Hammett Constant σp in [3+2] Cycloaddition Reactions of Aryl Azide/Alkyne Derivatives

    Directory of Open Access Journals (Sweden)

    Hicham Ben El Ayouchia

    2016-10-01

    Full Text Available The relationship between the electrophilicity ω index and the Hammett constant σp has been studied for the [2+3] cycloaddition reactions of a series of para-substituted phenyl azides towards para-substituted phenyl alkynes. The electrophilicity ω index—a reactivity density functional theory (DFT descriptor evaluated at the ground state of the molecules—shows a good linear relationship with the Hammett substituent constants σp. The theoretical scale of reactivity correctly explains the electrophilic activation/deactivation effects promoted by electron-withdrawing and electron-releasing substituents in both azide and alkyne components.

  9. One-pot synthesis of phthalazines and pyridazino-aromatics: a novel strategy for substituted naphthalenes.

    Science.gov (United States)

    Kessler, Simon N; Wegner, Hermann A

    2012-07-06

    A new one-pot strategy for the synthesis of phthalazines and pyridazino-aromatics starting from aromatic aldehydes has been developed. A variety of substituents ranging from electron withdrawing to donating is tolerated furnishing the desired 1,2-diazine in good to excellent yields. The products have been applied to the bidentate Lewis acid catalyzed inverse electron-demand Diels-Alder (IEDDA) reaction opening a novel two-step entry into substituted naphthalenes, such as Naproxen.

  10. LOW TEMPERATURE FORMATION OF NITROGEN-SUBSTITUTED POLYCYCLIC AROMATIC HYDROCARBONS (PANHs)—BARRIERLESS ROUTES TO DIHYDRO(iso)QUINOLINES

    Energy Technology Data Exchange (ETDEWEB)

    Parker, Dorian S. N.; Yang, Tao; Dangi, Beni B.; Kaiser, Ralf I. [Department of Chemistry, University of Hawaii at Manoa, Honolulu, HI 96822 (United States); Bera, Partha P.; Lee, Timothy J., E-mail: ralfk@hawaii.edu, E-mail: Timothy.J.Lee@nasa.gov [Space Science and Astrobiology Division, NASA Ames Research Center, Moffett Field, Mountain View, CA 94035 (United States)

    2015-12-20

    Meteorites contain bio-relevant molecules such as vitamins and nucleobases, which consist of aromatic structures with embedded nitrogen atoms. Questions remain over the chemical mechanisms responsible for the formation of nitrogen-substituted polycyclic aromatic hydrocarbons (PANHs) in extraterrestrial environments. By exploiting single collision conditions, we show that a radical mediated bimolecular collision between pyridyl radicals and 1,3-butadiene in the gas phase forms nitrogen-substituted polycyclic aromatic hydrocarbons (PANHs) 1,4-dihydroquinoline and to a minor amount 1,4-dihydroisoquinoline. The reaction proceeds through the formation of a van der Waals complex, which circumnavigates the entrance barrier implying it can operate at very low kinetic energy and therefore at low temperatures of 10 K as present in cold molecular clouds such as TMC-1. The discovery of facile de facto barrierless exoergic reaction mechanisms leading to PANH formation could play an important role in providing a population of aromatic structures upon which further photo-processing of ice condensates could occur to form nucleobases.

  11. Diverse Reactions of Thiophenes, Selenophenes, and Tellurophenes with Strongly Oxidizing I(III) PhI(L)2 Reagents.

    Science.gov (United States)

    Egalahewa, Sathsara; Albayer, Mohammad; Aprile, Antonino; Dutton, Jason L

    2017-02-06

    We report the outcomes of the reactions of aromatic group 16 thiophene, selenophene, and tellurophene rings with the I(III) oxidants PhI(OAc)(OTf) and [PhI(Pyr) 2 ][OTf] 2 (Pyr = pyridine). In all reactions, oxidative processes take place, with generation of PhI as the reduction product. However, with the exception of tellurophene with PhI(OAc)(OTf), +4 oxidation state complexes are not observed, but rather a variety of other processes occur. In general, where a C-H unit is available on the 5-membered ring, an electrophilic aromatic substitution reaction of either -IPh or pyridine onto the ring occurs. When all positions are blocked, reactions with PhI(OAc)(OTf) give acetic and triflic anhydride as the identifiable oxidative byproducts, while [PhI(Pyr) 2 ][OTf] 2 gives pyridine electrophilic aromatic substitution onto the peripheral rings. Qualitative mechanistic studies indicate that the presence of the oxidizable heteroatom is required for pyridine to act as an electrophile in a substantial manner.

  12. Nitrogen-Containing Coronenes: Theoretical Evaluation of the Influence of Aza-substitution on their Aromaticity

    Science.gov (United States)

    Pop, Raluca; van Staden, Jacobus; Diudea, Mircea

    2015-03-01

    The aromaticity of coronene derivatives where two C atoms of each outer six-membered ring are replaced by N have been investigated. Three types of substitution, namely 1,2-, 1,3-, and 1,4- are proposed. Computations of the geometric (HOMA index), energetic (HOMO-LUMO gap), and magnetic indices (NICS(0) and NICS(1)) were performed, and the results compared to the ones obtained for the all-carbon species. The results outline that the aza-derivatives have aromatic character comparable to the all-carbon species and an enlarged HOMO-LUMO gap.

  13. Infrared Spectroscopy of Matrix-Isolated Polycyclic Aromatic Compounds and Their Ions. 7; Phenazine, a Dual Substituted Polycyclic Aromatic Nitrogen Heterocycle

    Science.gov (United States)

    Mattioda, A. L.; Hudgins, D. M.; Bauschlicher, C. W., Jr.; Allamandola, L. J.

    2004-01-01

    The matrix-isolation technique has been employed to measure the mid-infrared spectra of phenazine (C12H8N2), a dual substituted Polycyclic Aromatic Nitrogen Heterocycle (PANH), in the neutral, cationic and anionic forms. The experimentally measured band frequencies and intensities are tabulated and compared with their calculated values as well as those of the non-substituted parent molecule, anthracene. The theoretical band positions and intensities were calculated using both the 3-31 G as well as the larger 6-3lG* Basis Sets. A comparison of the results can be found in the tables. The spectroscopic properties of phenazine and its cation are similar to those observed in mono-substituted PANHs, with one exception. The presence of a second nitrogen atom results in an additional enhancement of the cation's total integrated intensity, for the 1500-1000 cm(sup -1) (6.7 to 10 micron) region, over that observed for a mono-substituted PANH cation. The significance of this enhancement and the astrobiological implications of these results are discussed.

  14. Precision Electrophile Tagging in Caenorhabditis elegans.

    Science.gov (United States)

    Long, Marcus J C; Urul, Daniel A; Chawla, Shivansh; Lin, Hong-Yu; Zhao, Yi; Haegele, Joseph A; Wang, Yiran; Aye, Yimon

    2018-01-16

    Adduction of an electrophile to privileged sensor proteins and the resulting phenotypically dominant responses are increasingly appreciated as being essential for metazoan health. Functional similarities between the biological electrophiles and electrophilic pharmacophores commonly found in covalent drugs further fortify the translational relevance of these small-molecule signals. Genetically encodable or small-molecule-based fluorescent reporters and redox proteomics have revolutionized the observation and profiling of cellular redox states and electrophile-sensor proteins, respectively. However, precision mapping between specific redox-modified targets and specific responses has only recently begun to be addressed, and systems tractable to both genetic manipulation and on-target redox signaling in vivo remain largely limited. Here we engineer transgenic Caenorhabditis elegans expressing functional HaloTagged fusion proteins and use this system to develop a generalizable light-controlled approach to tagging a prototypical electrophile-sensor protein with native electrophiles in vivo. The method circumvents issues associated with low uptake/distribution and toxicity/promiscuity. Given the validated success of C. elegans in aging studies, this optimized platform offers a new lens with which to scrutinize how on-target electrophile signaling influences redox-dependent life span regulation.

  15. Uncatalyzed hydroamination of electrophilic organometallic alkynes: fundamental, theoretical, and applied aspects.

    Science.gov (United States)

    Wang, Yanlan; Latouche, Camille; Rapakousiou, Amalia; Lopez, Colin; Ledoux-Rak, Isabelle; Ruiz, Jaime; Saillard, Jean-Yves; Astruc, Didier

    2014-06-23

    Simple reactions of the most used functional groups allowing two molecular fragments to link under mild, sustainable conditions are among the crucial tools of molecular chemistry with multiple applications in materials science, nanomedicine, and organic synthesis as already exemplified by peptide synthesis and "click" chemistry. We are concerned with redox organometallic compounds that can potentially be used as biosensors and redox catalysts and report an uncatalyzed reaction between primary and secondary amines with organometallic electrophilic alkynes that is free of side products and fully "green". A strategy is first proposed to synthesize alkynyl organometallic precursors upon addition of electrophilic aromatic ligands of cationic complexes followed by endo hydride abstraction. Electrophilic alkynylated cyclopentadienyl or arene ligands of Fe, Ru, and Co complexes subsequently react with amines to yield trans-enamines that are conjugated with the organometallic group. The difference in reactivities of the various complexes is rationalized from the two-step reaction mechanism that was elucidated through DFT calculations. Applications are illustrated by the facile reaction of ethynylcobalticenium hexafluorophosphate with aminated silica nanoparticles. Spectroscopic, nonlinear-optical and electrochemical data, as well as DFT and TDDFT calculations, indicate a strong push-pull conjugation in these cobalticenium- and Fe- and Ru-arene-enamine complexes due to planarity or near-planarity between the organometallic and trans-enamine groups involving fulvalene iminium and cyclohexadienylidene iminium mesomeric forms. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Synthesis of a Fluorescent Acridone Using a Grignard Addition, Oxidation, and Nucleophilic Aromatic Substitution Reaction Sequence

    Science.gov (United States)

    Goodrich, Samuel; Patel, Miloni; Woydziak, Zachary R.

    2015-01-01

    A three-pot synthesis oriented for an undergraduate organic chemistry laboratory was developed to construct a fluorescent acridone molecule. This laboratory experiment utilizes Grignard addition to an aldehyde, alcohol oxidation, and iterative nucleophilic aromatic substitution steps to produce the final product. Each of the intermediates and the…

  17. Direct no-carrier-added 18F-labelling of arenes via nucleophilic substitution on aryl(2-thienyl)iodonium salts

    International Nuclear Information System (INIS)

    Ross, T.L.

    2006-01-01

    For in vivo imaging of molecular processes via positron emission tomography (PET) radiotracers of high specific activity are demanded. In case of the most commonly used positron emitter fluorine-18, this is only achievable with no-carrier-added [ 18 F]fluoride, which implies nucleophilic methods of 18 F-substitution. Whereas electron deficient aromatic groups can be labelled in one step using no-carrier-added [ 18 F]fluoride, electron rich 18 F-labelled aromatic molecules are only available by multi-step radiosyntheses or carrier-added electrophilic reactions. Here, diaryliodonium salts represent an alternative, since they have been proven as potent precursor for a direct nucleophilic 18 F-introduction into aromatic molecules. Furthermore, as known from non-radioactive studies, the highly electron rich 2-thienyliodonium leaving group leads to a high regioselectivity in nucleophilic substitution reactions. Consequently, a direct nucleophilic no-carrier-added 18 F-labelling of electron rich arenes via aryl(2-thienyl)iodonium precursors was developed in this work. The applicability of direct nucleophilic 18 F-labelling was examined in a systematic study on eighteen aryl(2-thienyl)iodonium salts. As electron rich precursors the ortho-, meta- and para-methoxyphenyl(2-thienyl)iodonium bromides, iodides, tosylates and triflates were synthesised. In addition, para-substituted (R=BnO, CH 3 , H, Cl, Br, I) aryl(2-thienyl)iodonium bromides were prepared as precursors with a systematically varying electron density. As first approach, the general reaction conditions of the nucleophilic 18 F-substitution procedure were optimised. The best conditions for direct nucleophilic no-carrier-added 18 F-labelling via aryl(2-thienyl)iodonium salts were found with dimethylformamide as solvent, a reaction temperature of 130±3 C and 25 mmol/l as concentration of the precursor. (orig.)

  18. Nitration of naphthalene and remarks on the mechanism of electrophilic aromatic nitration*

    Science.gov (United States)

    Olah, George A.; Narang, Subhash C.; Olah, Judith A.

    1981-01-01

    Naphthalene was nitrated with a variety of nitrating agents. Comparison of data with Perrin's electrochemical nitration [Perrin, C. L. (1977) J. Am. Chem. Soc. 99, 5516-5518] shows that nitration of naphthalene gives an α-nitronaphthalene to β-nitronaphthalene ratio that varies between 9 and 29 and is thus not constant. Perrin's data, therefore, are considered to be inconclusive evidence for the proposed one-electron transfer mechanism for the nitration of naphthalene and other reactive aromatics. Moodie and Schoefield [Hoggett, J. G., Moodie, R. B., Penton, J. R. & Schoefield, K. (1971) Nitration and Aromatic Reactivity (Cambridge Univ. Press, London)], as well as Perrin, independently concluded that, in the general scheme of nitration of reactive aromatics, there is the necessity to introduce into the classical Ingold mechanism an additional step involving a distinct intermediate preceding the formation of the Wheland intermediate (σ complexes). This view coincides with our two-step mechanistic picture [Kuhn, S. J. & Olah, G. A. (1961) J. Am. Chem. Soc. 83, 4564-4571] of the nitronium salt nitration of aromatic hydrocarbons (including benzene and toluene), in which low substrate selectivity but high positional selectivity was found, indicating the independence of substrate from positional selectivity. PMID:16593026

  19. Nitration of naphthalene and remarks on the mechanism of electrophilic aromatic nitration.

    Science.gov (United States)

    Olah, G A; Narang, S C; Olah, J A

    1981-06-01

    Naphthalene was nitrated with a variety of nitrating agents. Comparison of data with Perrin's electrochemical nitration [Perrin, C. L. (1977) J. Am. Chem. Soc. 99, 5516-5518] shows that nitration of naphthalene gives an alpha-nitronaphthalene to beta-nitronaphthalene ratio that varies between 9 and 29 and is thus not constant. Perrin's data, therefore, are considered to be inconclusive evidence for the proposed one-electron transfer mechanism for the nitration of naphthalene and other reactive aromatics. Moodie and Schoefield [Hoggett, J. G., Moodie, R. B., Penton, J. R. & Schoefield, K. (1971) Nitration and Aromatic Reactivity (Cambridge Univ. Press, London)], as well as Perrin, independently concluded that, in the general scheme of nitration of reactive aromatics, there is the necessity to introduce into the classical Ingold mechanism an additional step involving a distinct intermediate preceding the formation of the Wheland intermediate (sigma complexes). This view coincides with our two-step mechanistic picture [Kuhn, S. J. & Olah, G. A. (1961) J. Am. Chem. Soc. 83, 4564-4571] of the nitronium salt nitration of aromatic hydrocarbons (including benzene and toluene), in which low substrate selectivity but high positional selectivity was found, indicating the independence of substrate from positional selectivity.

  20. Catalytic stereoselective synthesis of highly substituted indanones via tandem Nazarov cyclization and electrophilic fluorination trapping.

    Science.gov (United States)

    Nie, Jing; Zhu, Hong-Wei; Cui, Han-Feng; Hua, Ming-Qing; Ma, Jun-An

    2007-08-02

    A new catalytic stereoselective tandem transformation via Nazarov cyclization/electrophilic fluorination has been accomplished. This sequence is efficiently catalyzed by a Cu(II) complex to afford fluorine-containing 1-indanone derivatives with two new stereocenters with high diastereoselectivity (trans/cis up to 49/1). Three examples of catalytic enantioselective tandem transformation are presented.

  1. Direct no-carrier-added {sup 18}F-labelling of arenes via nucleophilic substitution on aryl(2-thienyl)iodonium salts

    Energy Technology Data Exchange (ETDEWEB)

    Ross, T L

    2006-01-15

    For in vivo imaging of molecular processes via positron emission tomography (PET) radiotracers of high specific activity are demanded. In case of the most commonly used positron emitter fluorine-18, this is only achievable with no-carrier-added [{sup 18}F]fluoride, which implies nucleophilic methods of {sup 18}F-substitution. Whereas electron deficient aromatic groups can be labelled in one step using no-carrier-added [{sup 18}F]fluoride, electron rich {sup 18}F-labelled aromatic molecules are only available by multi-step radiosyntheses or carrier-added electrophilic reactions. Here, diaryliodonium salts represent an alternative, since they have been proven as potent precursor for a direct nucleophilic {sup 18}F-introduction into aromatic molecules. Furthermore, as known from non-radioactive studies, the highly electron rich 2-thienyliodonium leaving group leads to a high regioselectivity in nucleophilic substitution reactions. Consequently, a direct nucleophilic no-carrier-added {sup 18}F-labelling of electron rich arenes via aryl(2-thienyl)iodonium precursors was developed in this work. The applicability of direct nucleophilic {sup 18}F-labelling was examined in a systematic study on eighteen aryl(2-thienyl)iodonium salts. As electron rich precursors the ortho-, meta- and para-methoxyphenyl(2-thienyl)iodonium bromides, iodides, tosylates and triflates were synthesised. In addition, para-substituted (R=BnO, CH{sub 3}, H, Cl, Br, I) aryl(2-thienyl)iodonium bromides were prepared as precursors with a systematically varying electron density. As first approach, the general reaction conditions of the nucleophilic {sup 18}F-substitution procedure were optimised. The best conditions for direct nucleophilic no-carrier-added {sup 18}F-labelling via aryl(2-thienyl)iodonium salts were found with dimethylformamide as solvent, a reaction temperature of 130{+-}3 C and 25 mmol/l as concentration of the precursor. (orig.)

  2. An efficient method for synthesis of bis(indolylmethane and di-bis(indolylmethane derivatives in environmentally benign conditions using TBAHS

    Directory of Open Access Journals (Sweden)

    Seyed Hossein Siyadatifard

    2016-05-01

    Full Text Available An efficient procedure for the synthesis of bisindolylmethanes (BIMs from condensation of indole and aromatic aldehydes or ketones is described. The aromatic electrophilic substitution reactions of indole with aromatic aldehydes and ketones are achieved in the presence of tetrabutylammonium hydrogen sulfate (TBAHS as a mild and efficient solid acid catalyst. This methodology offers several advantages such as good yields, simple procedure, mild and environmentally benign conditions.

  3. Development and optimization of methods for the radiofluorination of aromatic compounds with specific, high fluorine-18 activity

    International Nuclear Information System (INIS)

    Franken, K.

    1987-06-01

    The positron emitter fluorine-18 (T 1/2 = 110 min) is an ideal radionuclide for analogue tracers in positron emission tomography (PET). In this study the production of the electrophilic species [ 18 F]-F 2 , [ 18 F]-CH 3 CO 2 F and to some extent [ 18 F]-XeF 2 has been optimized with respect to yield and specific activity. Selectivity and reactivity of these species have been studied in simple aromatic model compounds. Fluorine was produced via the 20 Ne(d,α) 18 F reaction. The effect of target material, dimensions, amount of carrier (F 2 ), pressure, beam current and irradiation time was studied. Reactivity of [ 18 F]-F 2 and [ 18 F]-CH 3 CO 2 F with respect to hydrogen subsitution was systematically studied in a series of benzene derivatives (C 6 H 5 X, X = CF 3 , I, Br, CL, F, H, CH 3 , OCH 3 , OH) in various solvents (CHCl 3 , CFCl 3 , CH 3 CN, CH 3 OH, CF 3 COOH). The radiochemical yield of 18 F-for-H-substitution in the aromatic ring increased with increasing acceptor number (AN) of the solvent. The electrophilic nature of both fluorination agents was confirmed by a Hammett plot. As expected, [ 18 F]-CH 3 CO 2 F showed a higher selectivity than [ 18 F]-F 2 . Direct radiofluorination with [ 18 F]-F 2 and [ 18 F]-CH 3 CO 2 F was successfully applied to the biomolecules phenylalanine, tyrosine and DOPA. As potential methods for no-carrier-added (n.c.a.) radiofluorination some less common dediazoniation reactions were also studied. (orig./RB) [de

  4. The synthesis of no-carrier-added DL-4-[18F]fluorodeprenyl via the nucleophilic aromatic substitution reaction

    International Nuclear Information System (INIS)

    Plenevaux, Alain; Guillaume, Marcel

    1991-01-01

    No-carrier-added DL-α-methyl-β-4-[ 18 F]fluorophenyl-N-methyl-N-propynylethylamine (DL-4-[ 18 F]fluorodeprenyl) was synthesized via a 3-step procedure. The overall yield was 11%, the synthesis time was 90 min and the specific activity >0.57 Ci/μmol (end of synthesis). This synthesis approach, the conversion of an aromatic aldehyde to a homologous methyl ketone, extends the flexibility of the nucleophilic aromatic substitution reaction by applying it to the synthesis of radiotracers which do not bear electron-withdrawing activating groups on the aromatic ring. The tissue distribution of DL-4-[ 18 F]fluorodeprenyl in mice at 1, 10 and 50 min was also measured and showed that metabolic defluorination was not significant. Clearance or radioactivity from brain after injection of DL-4-[ 18 F]fluorodeprenyl was more rapid than that previously observed for [ 11 C]L-deprenyl. (author)

  5. NCA nucleophilic radiofluorination on substituted benzaldehydes for the preparation of [18F]fluorinated aromatic amino acids

    International Nuclear Information System (INIS)

    Wadsak, Wolfgang; Wirl-Sagadin, Barbara; Mitterhauser, Markus; Mien, Leonhard-Key; Ettlinger, Dagmar E.; Keppler, Bernhard K.; Dudczak, Robert; Kletter, Kurt

    2006-01-01

    Nucleophilic aromatic substitution is a challenging task in radiochemistry. Therefore, a thorough evaluation and optimisation of this step is needed to provide a satisfactory tool for the routine preparation of [ 18 F]fluorinated aromatic amino acids. Two methods, already proposed elsewhere, were evaluated and improved. The yields for the radiofluorination were increased whereas activity loss during solid phase extraction was observed. Radiochemical yields for the two methods were 92.7±5.5% (method 1) and 92.1±12.3% (method 2) for conversion and 11.1±2.8% (method 1) and 34.8±0.6% (method 2) for purification, respectively. In total, we demonstrate an optimised method for the preparation of this important class of [ 18 F]fluorinated synthons for PET

  6. Relationship between electrophilicity index, Hammett constant and ...

    Indian Academy of Sciences (India)

    Unknown

    Inter-relationships between the electrophilicity index (ω), Hammett constant (óp) and nucleus- independent chemical ... cess of DFT is that it provides simple working equa- tions to elucidate ... compasses both the ability of an electrophile to ac-.

  7. Transformations of diaziridines and their fused analogues induced by electrophilic reagents

    International Nuclear Information System (INIS)

    Makhova, Nina N; Shevtsov, Alexander V; Petukhova, Vera Yu

    2011-01-01

    The review deals with transformations of mono- and bicyclic diaziridine derivatives with different types of substitution induced by electrophilic reagents (protic acids, Lewis acids, alkylating and acylating agents, carbonyl compounds, heterocumulenes, activated alkenes and alkynes and transition metal salts). The characteristic features of the reactions are considered as functions of the structures of the starting diaziridines and the nature of the reaction medium (organic solvents, ionic liquids). Prospects of the use of diaziridine derivatives as readily available precursors for the synthesis of various nitrogen-containing heterocyclic systems based on the diaziridine ring expansion reactions are considered. The bibliography includes 136 references.

  8. Green Synthesis of a Fluorescent Natural Product

    Science.gov (United States)

    Young, Douglas M.; Welker, Jacob J. C.; Doxsee, Kenneth M.

    2011-01-01

    Synthesis of 4-methylumbelliferone via the acid-catalyzed Pechmann condensation introduces students to several types of organic reactions: transesterification, electrophilic aromatic substitution, and alcohol dehydration. Performed with a recyclable, solid catalyst and under solvent-free conditions, the experiment illustrates many of the…

  9. Single base substitution causing the fragrant phenotype and development of a type-specific marker in aromatic coconut (Cocos nucifera).

    Science.gov (United States)

    Vongvanrungruang, A; Mongkolsiriwatana, C; Boonkaew, T; Sawatdichaikul, O; Srikulnath, K; Peyachoknagul, S

    2016-09-19

    The fragrance gene, betaine aldehyde dehydrogenase 2 (Badh2), has been well studied in many plant species. The objectives of this study were to clone Badh2 and compare the sequences between aromatic and non-aromatic coconuts. The complete coding region was cloned from cDNA of both aromatic and non-aromatic coconuts. The nucleotide sequences were highly homologous to Badh2 genes of other plants. Badh2 consisted of a 1512-bp open reading frame encoding 503 amino acids. A single nucleotide difference between aromatic and non-aromatic coconuts resulted in the conversion of alanine (non-aromatic) to proline (aromatic) at position 442, which was the substrate binding site of BADH2. The ring side chain of proline could destabilize the structure leading to a non-functional enzyme. Badh2 genomic DNA was cloned from exon 1 to 4, and from exon 5 to 15 from the two coconut types, except for intron 4 that was very long. The intron sequences of the two coconut groups were highly homologous. No differences in Badh2 expression were found among the tissues of aromatic coconut or between aromatic and non-aromatic coconuts. The amino acid sequences of BADH2 from coconut and other plants were compared and the genetic relationship was analyzed using MEGA 7.0. The phylogenetic tree reconstructed by the Bayesian information criterion consisted of two distinct groups of monocots and dicots. Among the monocots, coconut (Cocos nucifera) and oil palm (Elaeis guineensis) were the most closely related species. A marker for coconut differentiation was developed from one-base substitution site and could be successfully used.

  10. An atom counting and electrophilicity based QSTR approach

    Indian Academy of Sciences (India)

    WINTEC

    QSTR models with two parameters result when global electrophilicity is used as the second descriptor. In ... Atom counting; QSTR; electrophilicity; conceptual DFT; Tetrahymena pyriformis. ... theoretical background whereas the computational.

  11. Privileged Electrophile Sensors: A Resource for Covalent Drug Development.

    Science.gov (United States)

    Long, Marcus John Curtis; Aye, Yimon

    2017-07-20

    This Perspective delineates how redox signaling affects the activity of specific enzyme isoforms and how this property may be harnessed for rational drug design. Covalent drugs have resurged in recent years and several reports have extolled the general virtues of developing irreversible inhibitors. Indeed, many modern pharmaceuticals contain electrophilic appendages. Several invoke a warhead that hijacks active-site nucleophiles whereas others take advantage of spectator nucleophilic side chains that do not participate in enzymatic chemistry, but are poised to bind/react with electrophiles. The latest data suggest that innate electrophile sensing-which enables rapid reaction with an endogenous signaling electrophile-is a quintessential resource for the development of covalent drugs. For instance, based on recent work documenting isoform-specific electrophile sensing, isozyme non-specific drugs may be converted to isozyme-specific analogs by hijacking privileged first-responder electrophile-sensing cysteines. Because this approach targets functionally relevant cysteines, we can simultaneously harness previously untapped moonlighting roles of enzymes linked to redox sensing. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Orthogonal 4,10 and 6,12 substitution of dibenzo[def,mno]chrysene polycyclic aromatic small molecules

    KAUST Repository

    Koldemir, Unsal; Tinkham, Jonathan S.; Johnson, Robert; Lim, Bogyu; Yemam, Henok A.; Gagnon, Kevin J.; Parkin, Sean; Sellinger, Alan

    2017-01-01

    A series of new polycyclic aromatic hydrocarbon compounds based on (4,10-disubstituted-dibenzo[def,mno]chrysene-6,12-dione) and 4,10 di-substituted 6,12-bis(triisopropylsilylethynyl)dibenzo[def,mno]chrysene are reported with tunable electronic properties through varied molecular architecture. Starting with an inexpensive commercially available textile dye known as Vat Orange #3, (4,10-dibromo-dibenzo[def,mno] chrysene-6,12-dione) we extended the conjugation at the 4- and 10-positions by the attachment of both electron rich and deficient hexylvinylphthalimide, thiophene, hexylthiophene, triphenylamine, and hexylbithiophene aromatic groups, and studied the resultant optoelectronic properties. By applying various synthetic metal-catalyzed reactions, soluble dibenzo[def,mno]chrysene and dibenzo[def,mno]chrysene-6,12-dione derivatives were achieved with optical edge band gaps between 2.30 eV and 1.65 eV.

  13. Orthogonal 4,10 and 6,12 substitution of dibenzo[def,mno]chrysene polycyclic aromatic small molecules

    KAUST Repository

    Koldemir, Unsal

    2017-07-14

    A series of new polycyclic aromatic hydrocarbon compounds based on (4,10-disubstituted-dibenzo[def,mno]chrysene-6,12-dione) and 4,10 di-substituted 6,12-bis(triisopropylsilylethynyl)dibenzo[def,mno]chrysene are reported with tunable electronic properties through varied molecular architecture. Starting with an inexpensive commercially available textile dye known as Vat Orange #3, (4,10-dibromo-dibenzo[def,mno] chrysene-6,12-dione) we extended the conjugation at the 4- and 10-positions by the attachment of both electron rich and deficient hexylvinylphthalimide, thiophene, hexylthiophene, triphenylamine, and hexylbithiophene aromatic groups, and studied the resultant optoelectronic properties. By applying various synthetic metal-catalyzed reactions, soluble dibenzo[def,mno]chrysene and dibenzo[def,mno]chrysene-6,12-dione derivatives were achieved with optical edge band gaps between 2.30 eV and 1.65 eV.

  14. Synthesis of Bisphenol Z: An Organic Chemistry Experiment

    Science.gov (United States)

    Gregor, Richard W.

    2012-01-01

    A student achievable synthesis of bisphenol Z, 4,4'-(cyclohexane-1,1-diyl)diphenol, from the acid-catalyzed reaction of phenol with cyclohexanone is presented. The experiment exemplifies all the usual pedagogy for the standard topic of electrophilic aromatic substitution present in the undergraduate organic chemistry curriculum, while providing…

  15. Asymmetric syntheses of 3,4-disubstituted tetrahydroquinoline derivatives using (+)- sparteine-mediated electrophilic substitution

    International Nuclear Information System (INIS)

    Choi, Yun Soo; Kang, Kyoung Hee; Park, Yong Sun

    2015-01-01

    Tetrahydroquinolines bearing substituents are frequently found as a substructure in a number of alkaloids and natural products. Since their individual stereoisomers displays different biological activities, it is desirable to develop a highly stereoselective synthetic method for tetrahydroquinolines. While some progress has recently been made toward the development of asymmetric synthetic methods for tetrahydroquinolines, it is still a challenging topic in organic synthesis. In order to investigate the source of diastereoselection attained in the substitution reaction with a racemic epoxide, we examined the substitution of 2 with an excess amount of racemic p-chlorophenyl-substituted oxirane. We have developed a novel method for the asymmetric synthesis of trans-3,4-diaryl-substituted tetrahy- droquinolines from ortho-substituted N-pivaloyl anilines. The enantioselective process includes (+)-sparteine-mediated stereoselective lithiati on, kinetic resolution of epoxides in substitution, and stereospecific Mitsu nobu cyclization as the key reactions. The simple protocol can provide highly functionalized tetrahydroqu inoline rings and would allow their further functionalization to access more complex target molecules

  16. Asymmetric syntheses of 3,4-disubstituted tetrahydroquinoline derivatives using (+)- sparteine-mediated electrophilic substitution

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Yun Soo; Kang, Kyoung Hee; Park, Yong Sun [Dept. of Chemistry, Konkuk University, Seoul (Korea, Republic of)

    2015-05-15

    Tetrahydroquinolines bearing substituents are frequently found as a substructure in a number of alkaloids and natural products. Since their individual stereoisomers displays different biological activities, it is desirable to develop a highly stereoselective synthetic method for tetrahydroquinolines. While some progress has recently been made toward the development of asymmetric synthetic methods for tetrahydroquinolines, it is still a challenging topic in organic synthesis. In order to investigate the source of diastereoselection attained in the substitution reaction with a racemic epoxide, we examined the substitution of 2 with an excess amount of racemic p-chlorophenyl-substituted oxirane. We have developed a novel method for the asymmetric synthesis of trans-3,4-diaryl-substituted tetrahy- droquinolines from ortho-substituted N-pivaloyl anilines. The enantioselective process includes (+)-sparteine-mediated stereoselective lithiati on, kinetic resolution of epoxides in substitution, and stereospecific Mitsu nobu cyclization as the key reactions. The simple protocol can provide highly functionalized tetrahydroqu inoline rings and would allow their further functionalization to access more complex target molecules.

  17. Quantum mechanical design of efficient second-order nonlinear optical materials based on heteroaromatic imido-substituted hexamolybdates: first theoretical framework of POM-based heterocyclic aromatic rings.

    Science.gov (United States)

    Janjua, Muhammad Ramzan Saeed Ashraf

    2012-11-05

    This work was inspired by a previous report (Janjua et al. J. Phys. Chem. A 2009, 113, 3576-3587) in which the nonlinear-optical (NLO) response strikingly improved with an increase in the conjugation path of the ligand and the nature of hexamolybdates (polyoxometalates, POMs) was changed into a donor by altering the direction of charge transfer with a second aromatic ring. Herein, the first theoretical framework of POM-based heteroaromatic rings is found to be another class of excellent NLO materials having double heteroaromatic rings. First hyperpolarizabilities of a large number of push-pull-substituted conjugated systems with heteroaromatic rings have been calculated. The β components were computed at the density functional theory (DFT) level (BP86 geometry optimizations and LB94 time-dependent DFT). The largest β values are obtained with a donor (hexamolybdates) on the benzene ring and an acceptor (-NO(2)) on pyrrole, thiophene, and furan rings. The pyrrole imido-substituted hexamolybdate (system 1c) has a considerably large first hyperpolarizability, 339.00 × 10(-30) esu, and it is larger than that of (arylimido)hexamolybdate, calculated as 0.302 × 10(-30) esu (reference system 1), because of the double aromatic rings in the heteroaromatic imido-substituted hexamolybdates. The heteroaromatic rings act as a conjugation bridge between the electron acceptor (-NO(2)) and donor (polyanion). The introduction of an electron donor into heteroaromatic rings significantly enhances the first hyperpolarizabilities because the electron-donating ability is substantially enhanced when the electron donor is attached to the heterocyclic aromatic rings. Interposing five-membered auxiliary fragments between strong donor (polyanion) or acceptor (-NO(2)) groups results in a large computed second-order NLO response. The present investigation provides important insight into the NLO properties of (heteroaromatic) imido-substituted hexamolybdate derivatives because these compounds

  18. Dual Studies on a Hydrogen-Deuterium Exchange of Resorcinol and the Subsequent Kinetic Isotope Effect

    Science.gov (United States)

    Giles, Richard; Kim, Iris; Chao, Weyjuin Eric; Moore, Jennifer; Jung, Kyung Woon

    2014-01-01

    An efficient laboratory experiment has been developed for undergraduate students to conduct hydrogen-deuterium (H-D) exchange of resorcinol by electrophilic aromatic substitution using D[subscript 2]O and a catalytic amount of H[subscript 2]SO[subscript 4]. The resulting labeled product is characterized by [superscript 1]H NMR. Students also…

  19. Novel and simple synthesis of brominated 1,10-phenanthrolines

    Czech Academy of Sciences Publication Activity Database

    Výprachtický, Drahomír; Kaňková, Dana; Pokorná, Veronika; Kmínek, Ivan; Dzhabarov, Vagif; Cimrová, Věra

    2014-01-01

    Roč. 67, č. 6 (2014), s. 915-921 ISSN 0004-9425 R&D Projects: GA ČR GAP106/12/0827; GA ČR(CZ) GA13-26542S Institutional support: RVO:61389013 Keywords : 1,10-phenanthroline * electrophilic aromatic substitution * bromination Subject RIV: CD - Macromolecular Chemistry Impact factor: 1.558, year: 2014

  20. Organic astatine compounds, their preparation and properties

    Energy Technology Data Exchange (ETDEWEB)

    Vasaros, L; Berei, K

    1985-01-01

    Aromatic astatine compounds of possible medical application were prepared by high energy substitutions, by astatine-halogen, and by electrophil astatine-hydrogen substitutions at the Joint Institute of Nuclear Researches, Dubna. Physico-chemical properties of organic astatine compounds such as boiling point and evaporation heat, and the refraction and dissociation energy of carbon-astatine bonds were determined experimentally by gas chromatography. The results are compared with extrapolated data. (V.N.). 41 refs.; 7 figs.; 5 tables.

  1. Multiplexed Thiol Reactivity Profiling for Target Discovery of Electrophilic Natural Products.

    Science.gov (United States)

    Tian, Caiping; Sun, Rui; Liu, Keke; Fu, Ling; Liu, Xiaoyu; Zhou, Wanqi; Yang, Yong; Yang, Jing

    2017-11-16

    Electrophilic groups, such as Michael acceptors, expoxides, are common motifs in natural products (NPs). Electrophilic NPs can act through covalent modification of cysteinyl thiols on functional proteins, and exhibit potent cytotoxicity and anti-inflammatory/cancer activities. Here we describe a new chemoproteomic strategy, termed multiplexed thiol reactivity profiling (MTRP), and its use in target discovery of electrophilic NPs. We demonstrate the utility of MTRP by identifying cellular targets of gambogic acid, an electrophilic NP that is currently under evaluation in clinical trials as anticancer agent. Moreover, MTRP enables simultaneous comparison of seven structurally diversified α,β-unsaturated γ-lactones, which provides insights into the relative proteomic reactivity and target preference of diverse structural scaffolds coupled to a common electrophilic motif and reveals various potential druggable targets with liganded cysteines. We anticipate that this new method for thiol reactivity profiling in a multiplexed manner will find broad application in redox biology and drug discovery. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Modeling of Toxicity-Relevant Electrophilic Reactivity for Guanine with Epoxides: Estimating the Hard and Soft Acids and Bases (HSAB) Parameter as a Predictor.

    Science.gov (United States)

    Zhang, Jing; Wang, Chenchen; Ji, Li; Liu, Weiping

    2016-05-16

    According to the electrophilic theory in toxicology, many chemical carcinogens in the environment and/or their active metabolites are electrophiles that exert their effects by forming covalent bonds with nucleophilic DNA centers. The theory of hard and soft acids and bases (HSAB), which states that a toxic electrophile reacts preferentially with a biological macromolecule that has a similar hardness or softness, clarifies the underlying chemistry involved in this critical event. Epoxides are hard electrophiles that are produced endogenously by the enzymatic oxidation of parent chemicals (e.g., alkenes and PAHs). Epoxide ring opening proceeds through a SN2-type mechanism with hard nucleophile DNA sites as the major facilitators of toxic effects. Thus, the quantitative prediction of chemical reactivity would enable a predictive assessment of the molecular potential to exert electrophile-mediated toxicity. In this study, we calculated the activation energies for reactions between epoxides and the guanine N7 site for a diverse set of epoxides, including aliphatic epoxides, substituted styrene oxides, and PAH epoxides, using a state-of-the-art density functional theory (DFT) method. It is worth noting that these activation energies for diverse epoxides can be further predicted by quantum chemically calculated nucleophilic indices from HSAB theory, which is a less computationally demanding method than the exacting procedure for locating the transition state. More importantly, the good qualitative/quantitative correlations between the chemical reactivity of epoxides and their bioactivity suggest that the developed model based on HSAB theory may aid in the predictive hazard evaluation of epoxides, enabling the early identification of mutagenicity/carcinogenicity-relevant SN2 reactivity.

  3. Normal-phase liquid chromatography retention behavior of polycyclic aromatic sulfur heterocycles and alkyl-substituted polycyclic aromatic sulfur heterocycle isomers on an aminopropyl stationary phase.

    Science.gov (United States)

    Wilson, Walter B; Hayes, Hugh V; Sander, Lane C; Campiglia, Andres D; Wise, Stephen A

    2018-02-01

    Retention indices for 67 polycyclic aromatic sulfur heterocycles (PASHs) and 80 alkyl-substituted PASHs were determined using normal-phase liquid chromatography (NPLC) on an aminopropyl (NH 2 ) stationary phase. The retention behavior of PASH on the NH 2 phase is correlated with the number of aromatic carbon atoms and two structural characteristics have a significant influence on their retention: non-planarity (thickness, T) and the position of the sulfur atom in the bay-region of the structure. Correlations between solute retention on the NH 2 phase and T of PASHs were investigated for three cata-condensed (cata-) PASH isomer groups: (a) 13 four-ring molecular mass (MM) 234 Da cata-PASHs, (b) 20 five-ring MM 284 Da cata-PASHs, and (c) 12 six-ring MM 334 Da cata-PASHs. Correlation coefficients ranged from r = -0.49 (MM 234 Da) to r = -0.65 (MM 334 Da), which were significantly lower than structurally similar PAH isomer groups (r = -0.70 to r = -0.99). The NPLC retention behavior of the PASHs are compared to similar results for PAHs.

  4. Computational study of the rate constants and free energies of intramolecular radical addition to substituted anilines

    Directory of Open Access Journals (Sweden)

    Andreas Gansäuer

    2013-08-01

    Full Text Available The intramolecular radical addition to aniline derivatives was investigated by DFT calculations. The computational methods were benchmarked by comparing the calculated values of the rate constant for the 5-exo cyclization of the hexenyl radical with the experimental values. The dispersion-corrected PW6B95-D3 functional provided very good results with deviations for the free activation barrier compared to the experimental values of only about 0.5 kcal mol−1 and was therefore employed in further calculations. Corrections for intramolecular London dispersion and solvation effects in the quantum chemical treatment are essential to obtain consistent and accurate theoretical data. For the investigated radical addition reaction it turned out that the polarity of the molecules is important and that a combination of electrophilic radicals with preferably nucleophilic arenes results in the highest rate constants. This is opposite to the Minisci reaction where the radical acts as nucleophile and the arene as electrophile. The substitution at the N-atom of the aniline is crucial. Methyl substitution leads to slower addition than phenyl substitution. Carbamates as substituents are suitable only when the radical center is not too electrophilic. No correlations between free reaction barriers and energies (ΔG‡ and ΔGR are found. Addition reactions leading to indanes or dihydrobenzofurans are too slow to be useful synthetically.

  5. The Die Is Cast: Precision Electrophilic Modifications Contribute to Cellular Decision Making.

    Science.gov (United States)

    Long, Marcus J C; Aye, Yimon

    2016-10-02

    This perspective sets out to critically evaluate the scope of reactive electrophilic small molecules as unique chemical signal carriers in biological information transfer cascades. We consider these electrophilic cues as a new volatile cellular currency and compare them to canonical signaling circulation such as phosphate in terms of chemical properties, biological specificity, sufficiency, and necessity. The fact that nonenzymatic redox sensing properties are found in proteins undertaking varied cellular tasks suggests that electrophile signaling is a moonlighting phenomenon manifested within a privileged set of sensor proteins. The latest interrogations into these on-target electrophilic responses set forth a new horizon in the molecular mechanism of redox signal propagation wherein direct low-occupancy electrophilic modifications on a single sensor target are biologically sufficient to drive functional redox responses with precision timing. We detail how the various mechanisms through which redox signals function could contribute to their interesting phenotypic responses, including hormesis.

  6. ELECTROPHILIC CYCLIZATION OF DITERPENOIDS

    Directory of Open Access Journals (Sweden)

    Veaceslav Kulciţki

    2006-06-01

    Full Text Available A review of diterpenoid cyclization initiated by electrophilic reagents is provided. Conventional protonic and Lewis acids are examined along with superacids as initiators of cyclization cascade. An emphasis is placed on the use of cyclization reactions as a tool for the synthesis of compounds with potential practical utility. The review contains 74 references.

  7. Alkylation damage by lipid electrophiles targets functional protein systems.

    Science.gov (United States)

    Codreanu, Simona G; Ullery, Jody C; Zhu, Jing; Tallman, Keri A; Beavers, William N; Porter, Ned A; Marnett, Lawrence J; Zhang, Bing; Liebler, Daniel C

    2014-03-01

    Protein alkylation by reactive electrophiles contributes to chemical toxicities and oxidative stress, but the functional impact of alkylation damage across proteomes is poorly understood. We used Click chemistry and shotgun proteomics to profile the accumulation of proteome damage in human cells treated with lipid electrophile probes. Protein target profiles revealed three damage susceptibility classes, as well as proteins that were highly resistant to alkylation. Damage occurred selectively across functional protein interaction networks, with the most highly alkylation-susceptible proteins mapping to networks involved in cytoskeletal regulation. Proteins with lower damage susceptibility mapped to networks involved in protein synthesis and turnover and were alkylated only at electrophile concentrations that caused significant toxicity. Hierarchical susceptibility of proteome systems to alkylation may allow cells to survive sublethal damage while protecting critical cell functions.

  8. Alkylation Damage by Lipid Electrophiles Targets Functional Protein Systems*

    Science.gov (United States)

    Codreanu, Simona G.; Ullery, Jody C.; Zhu, Jing; Tallman, Keri A.; Beavers, William N.; Porter, Ned A.; Marnett, Lawrence J.; Zhang, Bing; Liebler, Daniel C.

    2014-01-01

    Protein alkylation by reactive electrophiles contributes to chemical toxicities and oxidative stress, but the functional impact of alkylation damage across proteomes is poorly understood. We used Click chemistry and shotgun proteomics to profile the accumulation of proteome damage in human cells treated with lipid electrophile probes. Protein target profiles revealed three damage susceptibility classes, as well as proteins that were highly resistant to alkylation. Damage occurred selectively across functional protein interaction networks, with the most highly alkylation-susceptible proteins mapping to networks involved in cytoskeletal regulation. Proteins with lower damage susceptibility mapped to networks involved in protein synthesis and turnover and were alkylated only at electrophile concentrations that caused significant toxicity. Hierarchical susceptibility of proteome systems to alkylation may allow cells to survive sublethal damage while protecting critical cell functions. PMID:24429493

  9. Synthesis of Heteroaromatic Compounds by Oxidative Aromatization Using an Activated Carbon/Molecular Oxygen System

    Directory of Open Access Journals (Sweden)

    Masahiko Hayashi

    2009-08-01

    Full Text Available A variety of heteroaromatic compounds, such as substituted pyridines, pyrazoles, indoles, 2-substituted imidazoles, 2-substituted imidazoles, 2-arylbenzazoles and pyrimidin-2(1H-ones are synthesized by oxidative aromatization using the activated carbon and molecular oxygen system. Mechanistic study focused on the role of activated carbon in the synthesis of 2-arylbenzazoles is also discussed. In the final section, we will disclose the efficient synthesis of substituted 9,10-anthracenes via oxidative aromatization.

  10. Normal-phase liquid chromatography retention behavior of polycyclic aromatic hydrocarbon and their methyl-substituted derivatives on an aminopropyl stationary phase.

    Science.gov (United States)

    Wilson, Walter B; Hayes, Hugh V; Sander, Lane C; Campiglia, Andres D; Wise, Stephen A

    2017-09-01

    Retention indices for 124 polycyclic aromatic hydrocarbons (PAHs) and 62 methyl-substituted (Me-) PAHs were determined using normal-phase liquid chromatography (NPLC) on a aminopropyl (NH 2 ) stationary phase. PAH retention behavior on the NH 2 phase is correlated to the total number of aromatic carbons in the PAH structure. Within an isomer group, non-planar isomers generally elute earlier than planar isomers. MePAHs generally elute slightly later but in the same region as the parent PAHs. Correlations between PAH retention behavior on the NH 2 phase and PAH thickness (T) values were investigated to determine the influence of non-planarity for isomeric PAHs with four to seven aromatic rings. Correlation coefficients ranged from r = 0.19 (five-ring peri-condensed molecular mass (MM) 252 Da) to r = -0.99 (five-ring cata-condensed MM 278 Da). In the case of the smaller PAHs (MM ≤ 252 Da), most of the PAHs had a planar structure and provided a low correlation. In the case of larger PAHs (MM ≥ 278 Da), nonplanarity had a significant influence on the retention behavior and good correlation between retention and T was obtained for the MM 278 Da, MM 302 Da, MM 328 Da, and MM 378 Da isomer sets. Graphical abstract NPLC separation of the three-, four-, five-, and six-ring PAH isomers with different number of aromatic carbon atoms and degrees of non-planarity (Thickness, T). The inserted figure plots the number of aromatic carbon atoms vs. the log I value for the 124 parent PAHs.

  11. On the electrophilic character of molecules through its relation with electronegativity and chemical hardness.

    Science.gov (United States)

    Islam, Nazmul; Ghosh, Dulal C

    2012-01-01

    Electrophilicity is an intrinsic property of atoms and molecules. It probably originates logistically with the involvement in the physical process of electrostatics of soaked charge in electronic shells and the screened nuclear charge of atoms. Motivated by the existing view of conceptual density functional theory that similar to electronegativity and hardness equalization, there should be a physical process of equalization of electrophilicity during the chemical process of formation of hetero nuclear molecules, we have developed a new theoretical scheme and formula for evaluating the electrophilicity of hetero nuclear molecules. A comparative study with available bench marking reveals that the hypothesis of electrophilicity and equalization, and the present method of evaluating equalized electrophilicity, are scientifically promising.

  12. On the Electrophilic Character of Molecules Through Its Relation with Electronegativity and Chemical Hardness

    Directory of Open Access Journals (Sweden)

    Dulal C. Ghosh

    2012-02-01

    Full Text Available Electrophilicity is an intrinsic property of atoms and molecules. It probably originates logistically with the involvement in the physical process of electrostatics of soaked charge in electronic shells and the screened nuclear charge of atoms. Motivated by the existing view of conceptual density functional theory that similar to electronegativity and hardness equalization, there should be a physical process of equalization of electrophilicity during the chemical process of formation of hetero nuclear molecules, we have developed a new theoretical scheme and formula for evaluating the electrophilicity of hetero nuclear molecules. A comparative study with available bench marking reveals that the hypothesis of electrophilicity and equalization, and the present method of evaluating equalized electrophilicity, are scientifically promising.

  13. Stereoselective synthesis of organosulfur compounds incorporating N-aromatic heterocyclic motifs and quaternary carbon centers via a sulfa-Michael triggered tandem reaction.

    Science.gov (United States)

    Qin, Tianyou; Cheng, Lu; Zhang, Sean Xiao-An; Liao, Weiwei

    2015-06-14

    A novel sulfa-Michael addition (SMA)-triggered tandem reaction was developed by combining a SMA reaction with a simultaneous rearomatization process utilizing a less reactive carbonyl group as an intramolecular electrophile partner, which provided a unique synthetic route to access various organosulfur compounds incorporating an N-aromatic heterocyclic motif and quaternary carbon centers.

  14. Fragmentation pathways of O-alkyl methylphosphonothionocyanidates in the gas phase: toward unambiguous structural characterization of chemicals in the Chemical Weapons Convention framework.

    Science.gov (United States)

    Saeidian, Hamid; Babri, Mehran; Ashrafi, Davood; Sarabadani, Mansour; Naseri, Mohammad Taghi

    2013-08-01

    The electron-impact (EI) mass spectra of a series of O-alkyl methylphosphonothionocyanidates were studied for Chemical Weapons Convention (CWC) purposes. General EI fragmentation pathways were constructed and discussed, and collision-induced dissociation studies of the major EI ions were performed to confirm proposed fragment structures by analyzing fragment ions of deuterated analogs and by use of density functional theory (DFT) calculations. Thiono-thiolo rearrangement, McLafferty-type rearrangement, and a previously unknown intramolecular electrophilic aromatic substitution reaction were observed and confirmed. The study also focused on differentiation of isomeric compounds. Retention indices for all compounds, and an electrophilicity index for several compounds, are reported and interpreted.

  15. Reversible targeting of noncatalytic cysteines with chemically tuned electrophiles

    DEFF Research Database (Denmark)

    Serafimova, Iana M; Pufall, Miles A; Krishnan, Shyam

    2012-01-01

    Targeting noncatalytic cysteine residues with irreversible acrylamide-based inhibitors is a powerful approach for enhancing pharmacological potency and selectivity. Nevertheless, concerns about off-target modification motivate the development of reversible cysteine-targeting strategies. Here we...... of these electrophiles into a noncovalent kinase-recognition scaffold produced slowly dissociating, covalent inhibitors of the p90 ribosomal protein S6 kinase RSK2. A cocrystal structure revealed specific noncovalent interactions that stabilize the complex by positioning the electrophilic carbon near the targeted...

  16. Arylazoindazole Photoswitches : Facile Synthesis and Functionalization via SNAr Substitution

    NARCIS (Netherlands)

    Travieso-Puente, Raquel; Budzak, Simon; Chen, Juan; Stacko, Peter; Jastrzebski, Johann T B H; Jacquemin, Denis; Otten, Edwin

    2017-01-01

    A straightforward synthetic route to arylazoindazoles via nucleophilic aromatic substitution is presented. Upon deprotonation of the NH group, a C6F5-substituted formazan undergoes facile cyclization as a result of intermolecular nucleophilic substitution (SNAr). This new class of azo photoswitches

  17. Advances towards aromatic oligoamide foldamers

    DEFF Research Database (Denmark)

    Hjelmgaard, Thomas; Plesner, Malene; Dissing, Mette Marie

    2014-01-01

    We have efficiently synthesized 36 arylopeptoid dimers with ortho-, meta-, and para-substituted aromatic backbones and tert-butyl or phenyl side chains. The dimers were synthesized by using a "submonomer method" on solid phase, by applying a simplified common set of reaction conditions. X......-ray crystallographic analysis of two of these dimers disclosed that the tert-butyl side chain invokes a cis amide conformation with a comparatively more closely packed structure of the surrounding aromatic backbone while the phenyl side chain results in a trans amide conformation with a more open, extended structure...... of the surrounding aromatic backbone. Investigation of the X-ray structures of two arylopeptoid dimers disclosed that the tert-butyl side chain invokes a cis amide conformation with a closely packed structure of the surrounding aromatic backbone while the phenyl side chain results in a trans amide conformation...

  18. Electrophilic trifluoromethyl-thiolation reaction and synthesis of radioligand for medicinal PET imaging of l'α-synuclein

    International Nuclear Information System (INIS)

    Alazet, Sebastien

    2015-01-01

    Part 1: More and more applications for fluorinated molecules are being found in various fields, from materials to life sciences. In recent years, a growing interest has emerged in the association of the trifluoromethyl group with heteroatoms such as CF3O or CF3S. The CF3S moiety is of particular interest, because of its high hydrophobicity parameter (π=1.44). Consequently compounds bearing this group are important targets for various applications, in particular in medicinal chemistry and agrochemistry. However, the majority of previous methods described in the literature use toxic reagents under harsh conditions. Trifluoromethane-sulfenamides (1. and 2. generation) have demonstrated their potential in the electrophilic trifluoromethyl-thiolations. Because of their interesting reactivity, these two generations of shelf-stable reagents are now in the toolbox of organic chemists for the trifluoromethyl-thiolation of molecules, providing a convenient method to pursue less toxic pathways. Part 2: α-synuclein aggregation is a neuro-pathological hallmark of many neuro-degenerative diseases including Parkinson's disease (PD) and dementia with Lewy bodies (DLB), collectively termed synucleinopathies. PET imaging can reflect the amount and distribution of alpha-synuclein aggregates in the brain and would be advantageous to use for specific diagnosis of synucleinopathies in pre-symptomatic stages of disease. We focused our interest onto benzimidazole derivatives as small, planar and π-delocalized compounds to design radiotracers of synuclein aggregates. Compounds based on the association of benzimidazole moiety, rigid linker (alkyne and triazole) and another aromatic part have been designed. The radiolabeling could be performed by nucleophilic substitution with K18F during the last step. With this convergent strategy, we could have access to a large series of molecules to be evaluated. (author)

  19. Spectroscopic and theoretical studies on the aromaticity of pyrrol-2-yl-carbonyl conformers

    Science.gov (United States)

    Dubis, Alina T.; Wojtulewski, Sławomir; Filipkowski, Karol

    2013-06-01

    The aromaticity of s-cis and s-trans pyrrol-2-yl carbonyl conformers was studied by FT-IR, 1H NMR spectroscopy and DFT calculations at the B3LYP/6-311++G(d,p) level of theory. The Harmonic Oscillator Model of Aromaticity (HOMA) and Nucleus Independent Chemical Shift (NICS) indices were calculated to estimate π-electron delocalization in the pyrrole ring. The usefulness of infrared spectroscopy in the evaluation of the aromaticity of the homogeneous set of pyrroles is discussed. The influence of 2-substitution on different aspects of aromaticity and stability of the pyrrol-2-yl carbonyl conformers is also discussed. It is concluded that the substitution effect of the title pyrrole derivatives can be explained on the basis of theoretical and experimental measurements of π-electron delocalization, including IR data.

  20. Copper(II)-catalyzed electrophilic amination of quinoline N-oxides with O-benzoyl hydroxylamines.

    Science.gov (United States)

    Li, Gang; Jia, Chunqi; Sun, Kai; Lv, Yunhe; Zhao, Feng; Zhou, Kexiao; Wu, Hankui

    2015-03-21

    Copper acetate-catalyzed C-H bond functionalization amination of quinoline N-oxides was achieved using O-benzoyl hydroxylamine as an electrophilic amination reagent, thereby affording the desired products in moderate to excellent yields. Electrophilic amination can also be performed in good yield on a gram scale.

  1. Story of skeletally substituted benzenes

    Indian Academy of Sciences (India)

    Unknown

    values are extensively used to define aromaticity quantitatively.3 In a recent study on ... studies were directed to unravel the subtle ways in which the stability, reactivity, and ..... The singlet–triplet gaps of all the skeletally substituted benzenes ...

  2. Recent advances in the ruthenium(ii)-catalyzed chelation-assisted C-H olefination of substituted aromatics, alkenes and heteroaromatics with alkenes via the deprotonation pathway.

    Science.gov (United States)

    Manikandan, Rajendran; Jeganmohan, Masilamani

    2017-08-08

    The transition-metal-catalyzed chelation-assisted alkenylation at the inert C-H bond of aromatics with alkenes is one of the efficient methods to synthesize substituted vinylarenes in a highly regio- and stereoselective manner. Palladium, rhodium and ruthenium complexes are frequently used as catalysts for this type of transformation. The present review describes the recent advances in the ruthenium-catalyzed chelation-assisted alkenylation at the C-H bond of aromatics, alkenes and heteroaromatics with alkenes via the deprotonation pathway. Several directing groups including 2-pyridyl, carbonyl, amidine, amide, amine, imidate, sulphonic acid, triazole, cyano, oxazolidinone and hydontoin are widely used in the reaction. The scope, limitation and mechanistic investigation of the alkenylation reactions are discussed elaborately. This feature article includes all the reported ruthenium-catalyzed alkenylation reactions via the deprotonation pathway until the end of March 2017.

  3. Transformations of Aromatic Compounds by Nitrosomonas europaea

    OpenAIRE

    Keener, William K.; Arp, Daniel J.

    1994-01-01

    Benzene and a variety of substituted benzenes inhibited ammonia oxidation by intact cells of Nitrosomonas europaea. In most cases, the inhibition was accompanied by transformation of the aromatic compound to a more oxidized product or products. All products detected were aromatic, and substituents were often oxidized but were not separated from the benzene ring. Most transformations were enhanced by (NH4)2SO4 (12.5 mM) and were prevented by C2H2, a mechanism-based inactivator of ammonia monoo...

  4. Arene-mercury complexes stabilized by gallium chloride: relative rates of H/D and arene exchange.

    Science.gov (United States)

    Branch, Catherine S; Barron, Andrew R

    2002-11-27

    We have previously proposed that the Hg(arene)(2)(GaCl(4))(2) catalyzed H/D exchange reaction of C(6)D(6) with arenes occurs via an electrophilic aromatic substitution reaction in which the coordinated arene protonates the C(6)D(6). To investigate this mechanism, the kinetics of the Hg(C(6)H(5)Me)(2)(GaCl(4))(2) catalyzed H/D exchange reaction of C(6)D(6) with naphthalene has been studied. Separate second-order rate constants were determined for the 1- and 2-positions on naphthalene; that is, the initial rate of H/D exchange = k(1i)[Hg][C-H(1)] + k(2i)[Hg][C-H(2)]. The ratio of k(1i)/k(2i) ranges from 11 to 2.5 over the temperature range studied, commensurate with the proposed electrophilic aromatic substitution reaction. Observation of the reactions over an extended time period shows that the rates change with time, until they again reach a new and constant second-order kinetics regime. The overall form of the rate equation is unchanged: final rate = k(1f)[Hg][C-H(1)] + k(2f)[Hg][C-H(2)]. This change in the H/D exchange is accompanied by ligand exchange between Hg(C(6)D(6))(2)(GaCl(4))(2) and naphthalene to give Hg(C(10)H(8))(2)(GaCl(4))(2,) that has been characterized by (13)C CPMAS NMR and UV-visible spectroscopy. The activation parameters for the ligand exchange may be determined and are indicative of a dissociative reaction and are consistent with our previously calculated bond dissociation for Hg(C(6)H(6))(2)(AlCl(4))(2). The initial Hg(arene)(2)(GaCl(4))(2) catalyzed reaction of naphthalene with C(6)D(6) involves the deuteration of naphthalene by coordinated C(6)D(6); however, as ligand exchange progresses, the pathway for H/D exchange changes to where the protonation of C(6)D(6) by coordinated naphthalene dominates. The site selectivity for the H/D exchange is initially due to the electrophilic aromatic substitution of naphthalene. As ligand exchange occurs, this selectivity is controlled by the activation of the naphthalene C-H bonds by mercury.

  5. Organic chemistry experiment

    International Nuclear Information System (INIS)

    Mun, Seok Sik

    2005-02-01

    This book deals with organic chemistry experiments, it is divided five chapters, which have introduction, the way to write the experiment report and safety in the laboratory, basic experiment technic like recrystallization and extraction, a lot of organic chemistry experiments such as fischer esterification, ester hydrolysis, electrophilic aromatic substitution, aldol reaction, benzoin condensation, wittig reaction grignard reaction, epoxidation reaction and selective reduction. The last chapter introduces chemistry site on the internet and way to find out reference on chemistry.

  6. A generalizable platform for interrogating target- and signal-specific consequences of electrophilic modifications in redox-dependent cell signaling.

    Science.gov (United States)

    Lin, Hong-Yu; Haegele, Joseph A; Disare, Michael T; Lin, Qishan; Aye, Yimon

    2015-05-20

    Despite the known propensity of small-molecule electrophiles to react with numerous cysteine-active proteins, biological actions of individual signal inducers have emerged to be chemotype-specific. To pinpoint and quantify the impacts of modifying one target out of the whole proteome, we develop a target-protein-personalized "electrophile toolbox" with which specific intracellular targets can be selectively modified at a precise time by specific reactive signals. This general methodology, T-REX (targetable reactive electrophiles and oxidants), is established by (1) constructing a platform that can deliver a range of electronic and sterically different bioactive lipid-derived signaling electrophiles to specific proteins in cells; (2) probing the kinetics of targeted delivery concept, which revealed that targeting efficiency in cells is largely driven by initial on-rate of alkylation; and (3) evaluating the consequences of protein-target- and small-molecule-signal-specific modifications on the strength of downstream signaling. These data show that T-REX allows quantitative interrogations into the extent to which the Nrf2 transcription factor-dependent antioxidant response element (ARE) signaling is activated by selective electrophilic modifications on Keap1 protein, one of several redox-sensitive regulators of the Nrf2-ARE axis. The results document Keap1 as a promiscuous electrophile-responsive sensor able to respond with similar efficiencies to discrete electrophilic signals, promoting comparable strength of Nrf2-ARE induction. T-REX is also able to elicit cell activation in cases in which whole-cell electrophile flooding fails to stimulate ARE induction prior to causing cytotoxicity. The platform presents a previously unavailable opportunity to elucidate the functional consequences of small-molecule-signal- and protein-target-specific electrophilic modifications in an otherwise unaffected cellular background.

  7. Accessing 2-substituted piperidine iminosugars by organometallic addition/intramolecular reductive amination: aldehyde vs. nitrone route.

    Science.gov (United States)

    Mirabella, S; Fibbi, G; Matassini, C; Faggi, C; Goti, A; Cardona, F

    2017-11-07

    A dual synthetic strategy to afford 2-substituted trihydroxypiperidines is disclosed. The procedure involved Grignard addition either to a carbohydrate-derived aldehyde or to a nitrone derived thereof, and took advantage of an efficient ring-closure reductive amination strategy in the final cyclization step. An opposite diastereofacial preference was demonstrated in the nucleophilic attack to the two electrophiles, which would finally produce the same piperidine diastereoisomer as the major product. However, use of a suitable Lewis acid in the Grignard addition to the nitrone allowed reversing the selectivity, giving access to 2-substituted piperidines with the opposite configuration at C-2.

  8. Organic superalkalis with closed-shell structure and aromaticity

    Science.gov (United States)

    Srivastava, Ambrish Kumar

    2018-06-01

    Benzene (C6H6) and polycyclic hydrocarbons such as naphthalene (C10H8), anthracene (C14H10) and coronene (C24H12) are well known aromatic organic compounds. We study the substitution of Li replacing all H-atoms in these hydrocarbons using density functional method. The vertical ionisation energy of such lithiated species, i.e. C6Li6, C10Li8, C14Li10 and C24Li12 ranges 4.24-4.50 eV, which is lower than the ionisation energy (IE) of Li atom. Thus, these species may behave as superalkalis due to their lower IE than alkali metal. However, these lithiated species possess planar and closed-shell structure, unlike typical superalkalis. Furthermore, all Li-substituted species are aromatic although their degree of aromaticity is reduced as compared to corresponding hydrocarbon analogues. We have further explored the structure of C6Li6 as star-like, unlike its inorganic analogue B3N3Li6, which appears as fan-like structure. We have also demonstrated that the interaction of C6Li6 with a superhalogen (such as BF4) is similar to that of a typical superalkali (such as OLi3). This may further suggest that the proposed lithiated species may form a new class of closed-shell organic superalkalis with aromaticity.

  9. Interaction of nitriles with electrophilic reagents

    International Nuclear Information System (INIS)

    Gridnev, I.D.; Gridneva, N.A.

    1995-01-01

    Reactions of organic nitriles with various electrophiles, Lewis acids (BF 3 , BCl 3 , RuCl 2 , NbCl 5 , ReCl 4 , etc.) in particular, were analysed. Features of nitriles coordination with transition metals (Mo, Ru, Re, Pt, etc.) were considered. It is shown that numerous processes observed in these reactions exhibit rather similar features and are mainly controlled by the nucleophilic properties of a nitrile. REfs, 99, tabs. 8

  10. Electronic forces as descriptors of nucleophilic and electrophilic regioselectivity and stereoselectivity.

    Science.gov (United States)

    Liu, Shubin; Rong, Chunying; Lu, Tian

    2017-01-04

    One of the main tasks of theoretical chemistry is to rationalize computational results with chemical insights. Key concepts of such nature include nucleophilicity, electrophilicity, regioselectivity, and stereoselectivity. While computational tools are available to predict barrier heights and other reactivity properties with acceptable accuracy, a conceptual framework to appreciate above quantities is still lacking. In this work, we introduce the electronic force as the fundamental driving force of chemical processes to understand and predict molecular reactivity. It has three components but only two are independent. These forces, electrostatic and steric, can be employed as reliable descriptors for nucleophilic and electrophilic regioselectivity and stereoselectivity. The advantages of using these forces to evaluate molecular reactivity are that electrophilic and nucleophilic attacks are featured by distinct characteristics in the electrostatic force and no knowledge of quantum effects included in the kinetic and exchange-correlation energies is required. Examples are provided to highlight the validity and general applicability of these reactivity descriptors. Possible applications in ambident reactivity, σ and π holes, frustrated Lewis pairs, and stereoselective reactions are also included in this work.

  11. Complexes of metal chlorides with proton donors — promising polyfunctional catalysts for electrophilic processes

    Science.gov (United States)

    Minsker, Karl S.; Ivanova, S. R.; Biglova, Raisa Z.

    1995-05-01

    The Bronsted acids formed as a result of the interaction of aluminium chlorides with Group I and II metal chlorides in the presence of proton-donating compounds are promising polyfunctional catalysts for electrophilic processes (polymerisation, depolymerisation and degradation of macromolecules, alkylation, desulfurisation, and hydrogenation). The factor determing the electrophilic activity and selectivity of the action of the catalysts is their acidity. This makes it possible to predict the direction of the changes in the activity and selectivity of the catalyst in specific chemical processes in conformity with the opposite variation rule: with increase in the acidity of the electrophilic catalyst, their activity increases but the selectivity of their action diminishes. The bibliography includes 72 references.

  12. Directed ortho metalation-based methodology. Halo-, nitroso-, and boro-induced ipso-desilylation. Link to an in situ Suzuki reaction.

    Science.gov (United States)

    Zhao, Zhongdong; Snieckus, Victor

    2005-06-23

    [reaction: see text] Treatment of DoM-derived silylated aromatics 2-4 under standard electrophilic halogenation conditions cleanly affords ipso-desilyation products 5-7, while nitration of methoxy-substituted analogues 8, 9 leads to non-ipso isomers 10, 12 and 11, 13, controlled by a silicon steric effect. Sequential ipso-borodesilylation of 2a, 3a, and 20 followed by treatment with aryl halides under Pd-catalyzed conditions constitutes an in situ Suzuki-Miyaura cross-coupling protocol to biaryls and heterobiaryls 23.

  13. Infrared Spectroscopy of Matrix-Isolated Polycyclic Aromatic Nitrogen Heterocycles (PANHs)

    Science.gov (United States)

    Mattioda, A. L.; Hudgins, D. M.; Bauschlicher, C. W.; Allamandola, L. J.; Biemesderfer, C. D.; Rosi, M.

    2002-01-01

    The mid-infrared spectra of the nitrogen-containing heterocyclic polycyclic aromatic compounds 1-azabenz[a]-anthracene; 2-azabenz[a]anthracene; 1-azachrysene; 2-azachrysene; 4-azachrysene; 2-azapyrene, and 7,8 benzoquinoline in their neutral and cation forms were investigated. The spectra of these species isolated in an argon matrix have been measured. Band frequencies and intensities were tabulated and these data compared with spectra computed using density functional theory at the B3LYP level. The overall agreement between experiment and theory is quite good, in keeping with earlier results on homonuclear polycyclic aromatic hydrocarbons. The differences between the spectral properties of nitrogen bearing aromatics and non-substituted, neutral polycyclic aromatic hydrocarbons will be discussed.

  14. Monohalogenated acetamide-induced cellular stress and genotoxicity are related to electrophilic softness and thiol/thiolate reactivity.

    Science.gov (United States)

    Pals, Justin A; Wagner, Elizabeth D; Plewa, Michael J; Xia, Menghang; Attene-Ramos, Matias S

    2017-08-01

    Haloacetamides (HAMs) are cytotoxic, genotoxic, and mutagenic byproducts of drinking water disinfection. They are soft electrophilic compounds that form covalent bonds with the free thiol/thiolate in cysteine residues through an S N 2 reaction mechanism. Toxicity of the monohalogenated HAMs (iodoacetamide, IAM; bromoacetamide, BAM; or chloroacetamide, CAM) varied depending on the halogen substituent. The aim of this research was to investigate how the halogen atom affects the reactivity and toxicological properties of HAMs, measured as induction of oxidative/electrophilic stress response and genotoxicity. Additionally, we wanted to determine how well in silico estimates of electrophilic softness matched thiol/thiolate reactivity and in vitro toxicological endpoints. Each of the HAMs significantly induced nuclear Rad51 accumulation and ARE signaling activity compared to a negative control. The rank order of effect was IAM>BAM>CAM for Rad51, and BAM≈IAM>CAM for ARE. In general, electrophilic softness and in chemico thiol/thiolate reactivity provided a qualitative indicator of toxicity, as the softer electrophiles IAM and BAM were more thiol/thiolate reactive and were more toxic than CAM. Copyright © 2017. Published by Elsevier B.V.

  15. Hydrogen-bond-driven electrophilic activation for selectivity control: scope and limitations of fluorous alcohol-promoted selective formation of 1,2-disubstituted benzimidazoles and mechanistic insight for rationale of selectivity.

    Science.gov (United States)

    Chebolu, Rajesh; Kommi, Damodara N; Kumar, Dinesh; Bollineni, Narendra; Chakraborti, Asit K

    2012-11-16

    Hydrogen-bond-driven electrophilic activation for selectivity control during competitive formation of 1,2-disubstituted and 2-substituted benzimidazoles from o-phenylenediamine and aldehydes is reported. The fluorous alcohols trifluoroethanol and hexafluoro-2-propanol efficiently promote the cyclocondensation of o-phenylenediamine with aldehydes to afford selectively the 1,2-disubstituted benzimidazoles at rt in short times. A mechanistic insight is invoked by NMR, mass spectrometry, and chemical studies to rationalize the selectivity. The ability of the fluorous alcohols in promoting the reaction and controlling the selectivity can be envisaged from their better hydrogen bond donor (HBD) abilities compared to that of the other organic solvents as well as of water. Due to the better HBD values, the fluorous alcohols efficiently promote the initial bisimine formation by electrophilic activation of the aldehyde carbonyl. Subsequently the hydrogen-bond-mediated activation of the in situ-formed bisimine triggers the rearrangement via 1,3-hydride shift to form the 1,2-disubstituted benzimidazoles.

  16. Rhodium(I)-catalyzed cycloisomerization of benzylallene-alkynes through C-H activation.

    Science.gov (United States)

    Kawaguchi, Yasuaki; Yasuda, Shigeo; Kaneko, Akira; Oura, Yuki; Mukai, Chisato

    2014-07-14

    The efficient Rh(I)-catalyzed cycloisomerization of benzylallene-alkynes produced the tricyclo[9.4.0.0(3,8)]pentadecapentaene skeleton through a C(sp2)-H bond activation in good yields. A plausible reaction mechanism proceeds via oxidative addition of the acetylenic C-H bond to Rh(I), an ene-type cyclization to the vinylidenecarbene-Rh(I) intermediate, and an electrophilic aromatic substitution with the vinylidenecarbene species. It was proposed based on deuteration and competition experiments. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Synthesis of D-fructose-derived spirocyclic 2-substituted-2-oxazoline ribosides

    Directory of Open Access Journals (Sweden)

    Madhuri Vangala

    2015-11-01

    Full Text Available The TMSOTf-mediated synthesis of β-configured spirocyclic 2-substituted-2-oxazoline ribosides was achieved using a “Ritter-like” reaction in toluene through nucleophilic addition of electron-rich nitriles to the oxacarbenium ion intermediate of 1,2;3,4-di-O-isopropylidene-β-D-psicofuranose derivatives with concomitant intramolecular trapping of the C2 hydroxymethyl group on the electrophilic nitrilium carbon. These carbohydrate-derived spirooxazolines are stable and were obtained in good yield with high stereoselectivity due to the conformational rigidity imparted by the 3,4-isopropylidene group.

  18. Metabolic activation of polycyclic and heterocyclic aromatic hydrocarbons and DNA damage: A review

    International Nuclear Information System (INIS)

    Xue Weiling; Warshawsky, David

    2005-01-01

    Polycyclic aromatic hydrocarbons (PAHs) and heterocyclic aromatic compounds (HACs) constitute a major class of chemical carcinogens present in the environment. These compounds require activation to electrophilic metabolites to exert their mutagenic or carcinogenic effects. There are three principal pathways currently proposed for metabolic activation of PAH and HAC: the pathway via bay region dihydrodiol epoxide by cytochrome P450 enzymes (CYPs), the pathway via radical cation by one-electron oxidation, and the ortho-quinone pathway by dihydrodiol dehydrogenase (DD). In addition to these major pathways, a brief description of a minor metabolic activation pathway, sulfonation, for PAHs that contain a primary benzylic alcoholic group or secondary hydroxyl group(s) is included in this review. The DNA damages caused through the reactive metabolites of PAH/HAC are described involving the DNA covalent binding to form stable or depurinating adducts, the formation of apurinic sites, and the oxidative damage. The review emphasizes the chemical/biochemical reactions involved in the metabolic processes and the chemical structures of metabolites and DNA adducts

  19. Chemoproteomic profiling of targets of lipid-derived electrophiles by bioorthogonal aminooxy probe

    Directory of Open Access Journals (Sweden)

    Ying Chen

    2017-08-01

    Full Text Available Redox imbalance in cells induces lipid peroxidation and generates a class of highly reactive metabolites known as lipid-derived electrophiles (LDEs that can modify proteins and affects their functions. Identifying targets of LDEs is critical to understand how such modifications are functionally implicated in oxidative-stress associated diseases. Here we report a quantitative chemoproteomic method to globally profile protein targets and sites modified by LDEs. In this strategy, we designed and synthesized an alkyne-functionalized aminooxy probe to react with LDE-modified proteins for imaging and proteomic profiling. Using this probe, we successfully quantified >4000 proteins modified by 4-hydroxy-2-nonenal (HNE of high confidence in mammalian cell lysate and combined with a tandem-orthogonal proteolysis activity-based protein profiling (TOP-ABPP strategy, we identified ~400 residue sites targeted by HNE including reactive cysteines in peroxiredoxins, an important family of enzymes with anti-oxidant roles. Our method expands the toolbox to quantitatively profile protein targets of endogenous electrophiles and the enlarged inventory of LDE-modified proteins and sites will contribute to functional elucidation of cellular pathways affected by oxidative stress. Keywords: Lipid-derived electrophile, 4-hydroxy-2-nonenal, Chemoproteomics, Aminooxy probe, Activity-based protein profiling

  20. α- and α'-Lithiation-Electrophile Trapping of N-Thiopivaloyl and N-tert-Butoxythiocarbonyl α-Substituted Azetidines: Rationalization of the Regiodivergence Using NMR and Computation.

    Science.gov (United States)

    Jackson, Kelvin E; Mortimer, Claire L; Odell, Barbara; McKenna, Jeffrey M; Claridge, Timothy D W; Paton, Robert S; Hodgson, David M

    2015-10-16

    (1)H NMR and computational analyses provide insight into the regiodivergent (α- and α'-) lithiation-electrophile trapping of N-thiopivaloyl- and N-(tert-butoxythiocarbonyl)-α-alkylazetidines. The magnitudes of the rotation barriers in these azetidines indicate that rotamer interconversions do not occur at the temperature and on the time scale of the lithiations. The NMR and computational studies support the origin of regioselectivity as being thiocarbonyl-directed lithiation from the lowest energy amide-like rotameric forms (cis for N-thiopivaloyl and trans for N-tert-butoxythiocarbonyl).

  1. Nucleophilic Aromatic Substitution Between Halogenated Benzene Dopants and Nucleophiles in Atmospheric Pressure Photoionization.

    Science.gov (United States)

    Kauppila, Tiina J; Haack, Alexander; Kroll, Kai; Kersten, Hendrik; Benter, Thorsten

    2016-03-01

    In a preceding work with dopant assisted-atmospheric pressure photoionization (DA-APPI), an abundant ion at [M + 77](+) was observed in the spectra of pyridine and quinoline with chlorobenzene dopant. This contribution aims to reveal the identity and route of formation of this species, and to systematically investigate structurally related analytes and dopants. Compounds containing N-, O-, and S-lone pairs were investigated with APPI in the presence of fluoro-, chloro-, bromo-, and iodobenzene dopants. Computational calculations on a density functional theory (DFT) level were carried out to study the reaction mechanism for pyridine and the different halobenzenes. The experimental and computational results indicated that the [M + 77](+) ion was formed by nucleophilic aromatic ipso-substitution between the halobenzene radical cation and nucleophilic analytes. The reaction was most efficient for N-heteroaromatic compounds, and it was weakened by sterical effects and enhanced by resonance stabilization. The reaction was most efficient with chloro-, bromo-, and iodobenzenes, whereas with fluorobenzene the reaction was scarcely observed. The calculated Gibbs free energies for the reaction between pyridine and the halobenzenes were shown to increase in the order I < Br < Cl < F. The reaction was found endergonic for fluorobenzene due to the strong C-F bonding, and exergonic for the other halobenzenes. For fluoro- and chlorobenzenes the reaction was shown to proceed through an intermediate state corresponding to [M + dopant](+), which was highly stable for fluorobenzene. For the bulkier bromine and iodine, this intermediate did not exist, but the halogens were shown to detach already during the approach by the nucleophile.

  2. Addition of electrophilic lipids to actin alters filament structure

    International Nuclear Information System (INIS)

    Gayarre, Javier; Sanchez, David; Sanchez-Gomez, Francisco J.; Terron, Maria C.; Llorca, Oscar; Perez-Sala, Dolores

    2006-01-01

    Pathophysiological processes associated with oxidative stress lead to the generation of reactive lipid species. Among them, lipids bearing unsaturated aldehyde or ketone moieties can form covalent adducts with cysteine residues and modulate protein function. Through proteomic techniques we have identified actin as a target for the addition of biotinylated analogs of the cyclopentenone prostaglandins 15-deoxy-Δ 12,14 -PGJ 2 (15d-PGJ 2 ) and PGA 1 in NIH-3T3 fibroblasts. This modification could take place in vitro and mapped to the protein C-terminal end. Other electrophilic lipids, like the isoprostane 8-iso-PGA 1 and 4-hydroxy-2-nonenal, also bound to actin. The C-terminal region of actin is important for monomer-monomer interactions and polymerization. Electron microscopy showed that actin treated with 15d-PGJ 2 or 4-hydroxy-2-nonenal formed filaments which were less abundant and displayed shorter length and altered structure. Streptavidin-gold staining allowed mapping of biotinylated 15d-PGJ 2 at sites of filament disruption. These results shed light on the structural implications of actin modification by lipid electrophiles

  3. Chemometric characterization of the hydrogen bonding complexes of secondary amides and aromatic hydrocarbons

    OpenAIRE

    Jović, Branislav; Nikolić, Aleksandar; Petrović, Slobodan

    2012-01-01

    The paper reports the results of the study of hydrogen bonding complexes between secondary amides and various aromatic hydrocarbons. The possibility of using chemometric methods was investigated in order to characterize N-H•••π hydrogen bonded complexes. Hierarchical clustering and Principal Component Analysis (PCA) have been applied on infrared spectroscopic and Taft parameters of 43 N-substituted amide complexes with different aromatic hydrocarbons. Results obtained in this report are...

  4. Recent advances in the ruthenium-catalyzed hydroarylation of alkynes with aromatics: synthesis of trisubstituted alkenes.

    Science.gov (United States)

    Manikandan, Rajendran; Jeganmohan, Masilamani

    2015-11-14

    The hydroarylation of alkynes with substituted aromatics in the presence of a metal catalyst via chelation-assisted C-H bond activation is a powerful method to synthesize trisubstituted alkenes. Chelation-assisted C-H bond activation can be done by two ways: (a) an oxidative addition pathway and (b) a deprotonation pathway. Generally, a mixture of cis and trans stereoisomeric as well as regioisomeric trisubstituted alkenes was observed in an oxidative addition pathway. In the deprotonation pathway, the hydroarylation reaction can be done in a highly regio- and stereoselective manner, and enables preparation of the expected trisubstituted alkenes in a highly selective manner. Generally, ruthenium, rhodium and cobalt complexes are used as catalysts in the reaction. In this review, a ruthenium-catalyzed hydroarylation of alkynes with substituted aromatics is covered completely. The hydroarylation reaction of alkynes with amide, azole, carbamate, phosphine oxide, amine, acetyl, sulfoxide and sulphur directed aromatics is discussed.

  5. Aromatic products from reaction of lignin model compounds with UV-alkaline peroxide

    International Nuclear Information System (INIS)

    Sun, Y.P.; Wallis, A.F.A.; Nguyen, K.L.

    1997-01-01

    A series of guaiacyl and syringyl lignin model compounds and their methylated analogues were reacted with alkaline hydrogen peroxide while irradiating with UV light at 254 nm. The aromatic products obtained were investigated by gas chromatography-mass spectrometry (GC-MS). Guaiacol, syringol and veratrol gave no detectable aromatic products. However, syringol methyl ether gave small amounts of aromatic products, resulting from ring substitution and methoxyl displacement by hydroxyl radicals. Reaction of vanillin and syringaldehyde gave the Dakin reaction products, methoxy-1,4-hydroquinones, while reaction of their methyl ethers yielded benzoic acids. Acetoguaiacone, acetosyringone and their methyl ethers afforded several hydroxylated aromatic products, but no aromatic products were identified in the reaction mixtures from guaiacylpropane and syringylpropane. In contrast, veratrylpropane gave a mixture from which 17 aromatic hydroxylated compounds were identified. It is concluded that for phenolic lignin model compounds, particularly those possessing electrondonating aromatic ring substituents, ring-cleavage reactions involving superoxide radical anions are dominant, whereas for non-phenolic lignin models, hydroxylation reactions through attack of hydroxyl radicals prevail

  6. The effect of varying the anion of an ionic liquid on the solvent effects on a nucleophilic aromatic substitution reaction.

    Science.gov (United States)

    Hawker, Rebecca R; Haines, Ronald S; Harper, Jason B

    2018-05-09

    A variety of ionic liquids, each containing the same cation but a different anion, were examined as solvents for a nucleophilic aromatic substitution reaction. Varying the proportion of ionic liquid was found to increase the rate constant as the mole fraction of ionic liquid increased demonstrating that the reaction outcome could be controlled through varying the ionic liquid. The solvent effects were correlated with the hydrogen bond accepting ability (β) of the ionic liquid anion allowing for qualitative prediction of the effect of changing this component of the solute. To determine the microscopic origins of the solvent effects, activation parameters were determined through temperature-dependent kinetic analyses and shown to be consistent with previous studies. With the knowledge of the microscopic interactions in solution, an ionic liquid was rationally chosen to maximise rate enhancement demonstrating that an ionic solvent can be selected to control reaction outcome for this reaction type.

  7. Bio-Based Aromatic Epoxy Monomers for Thermoset Materials

    Directory of Open Access Journals (Sweden)

    Feifei Ng

    2017-01-01

    Full Text Available The synthesis of polymers from renewable resources is a burning issue that is actively investigated. Polyepoxide networks constitute a major class of thermosetting polymers and are extensively used as coatings, electronic materials, adhesives. Owing to their outstanding mechanical and electrical properties, chemical resistance, adhesion, and minimal shrinkage after curing, they are used in structural applications as well. Most of these thermosets are industrially manufactured from bisphenol A (BPA, a substance that was initially synthesized as a chemical estrogen. The awareness on BPA toxicity combined with the limited availability and volatile cost of fossil resources and the non-recyclability of thermosets implies necessary changes in the field of epoxy networks. Thus, substitution of BPA has witnessed an increasing number of studies both from the academic and industrial sides. This review proposes to give an overview of the reported aromatic multifunctional epoxide building blocks synthesized from biomass or from molecules that could be obtained from transformed biomass. After a reminder of the main glycidylation routes and mechanisms and the recent knowledge on BPA toxicity and legal issues, this review will provide a brief description of the main natural sources of aromatic molecules. The different epoxy prepolymers will then be organized from simple, mono-aromatic di-epoxy, to mono-aromatic poly-epoxy, to di-aromatic di-epoxy compounds, and finally to derivatives possessing numerous aromatic rings and epoxy groups.

  8. Akt3 is a privileged first responder in isozyme-specific electrophile response.

    Science.gov (United States)

    Long, Marcus J C; Parvez, Saba; Zhao, Yi; Surya, Sanjna L; Wang, Yiran; Zhang, Sheng; Aye, Yimon

    2017-03-01

    Isozyme-specific post-translational regulation fine tunes signaling events. However, redundancy in sequence or activity renders links between isozyme-specific modifications and downstream functions uncertain. Methods to study this phenomenon are underdeveloped. Here we use a redox-targeting screen to reveal that Akt3 is a first-responding isozyme sensing native electrophilic lipids. Electrophile modification of Akt3 modulated downstream pathway responses in cells and Danio rerio (zebrafish) and markedly differed from Akt2-specific oxidative regulation. Digest MS sequencing identified Akt3 C119 as the privileged cysteine that senses 4-hydroxynonenal. A C119S Akt3 mutant was hypomorphic for all downstream phenotypes shown by wild-type Akt3. This study documents isozyme-specific and chemical redox signal-personalized physiological responses.

  9. The proton transfer reaction in malonaldehyde derivatives: Substituent effects and quasi-aromaticity of the proton bridge

    International Nuclear Information System (INIS)

    Palusiak, Marcin; Simon, Silvia; Sola, Miquel

    2007-01-01

    The proton transfer in malonaldehyde and in some of its derivatives have been considered in order to study the interrelation between the reaction barrier and the π-delocalization in the quasi-ring. A set of simple and mostly common substituents having different properties in resonance effect according to values of substituents constants were chosen in order to simulate the influence of substitution in position 2 or in position 1 (or 3) of malonaldehyde on the quasi-aromaticity and H-bonding. The following substituents have been taken into consideration: NO, NO 2 , CN, CHO, F, H, CH 3 , OCH 3 , OH, and NH 2 . Our results show that when the substituent is attached at position 2 of the quasi-ring, the resonance effect predominates over the field/inductive effect which leads to changes in H-bonding and quasi-aromaticity of the ring motif, while in the case of 1(3) substitution the field/inductive effect is significantly more effective influencing the HB strength, and thus, the proton transfer barrier. Somehow counterintuitively, for the 1(3) substituted systems, the most stable isomer is the one having the weakest HB and lower aromaticity. The reason for this surprising behaviour is discussed

  10. Electrophilic nitro-fatty acids suppress allergic contact dermatitis in mice.

    Science.gov (United States)

    Mathers, A R; Carey, C D; Killeen, M E; Diaz-Perez, J A; Salvatore, S R; Schopfer, F J; Freeman, B A; Falo, L D

    2017-04-01

    Reactions between nitric oxide (NO), nitrite (NO2-), and unsaturated fatty acids give rise to electrophilic nitro-fatty acids (NO 2 -FAs), such as nitro oleic acid (OA-NO 2 ) and nitro linoleic acid (LNO 2 ). Endogenous electrophilic fatty acids (EFAs) mediate anti-inflammatory responses by modulating metabolic and inflammatory signal transduction reactions. Hence, there is considerable interest in employing NO 2 -FAs and other EFAs for the prevention and treatment of inflammatory disorders. Thus, we sought to determine whether OA-NO 2 , an exemplary nitro-fatty acid, has the capacity to inhibit cutaneous inflammation. We evaluated the effect of OA-NO 2 on allergic contact dermatitis (ACD) using an established model of contact hypersensitivity in C57Bl/6 mice utilizing 2,4-dinitrofluorobenzene as the hapten. We found that subcutaneous (SC) OA-NO 2 injections administered 18 h prior to sensitization and elicitation suppresses ACD in both preventative and therapeutic models. In vivo SC OA-NO 2 significantly inhibits pathways that lead to inflammatory cell infiltration and the production of inflammatory cytokines in the skin. Moreover, OA-NO 2 is capable of enhancing regulatory T-cell activity. Thus, OA-NO 2 treatment results in anti-inflammatory effects capable of inhibiting ACD by inducing immunosuppressive responses. Overall, these results support the development of OA-NO 2 as a promising therapeutic for ACD and provides new insights into the role of electrophilic fatty acids in the control of cutaneous immune responses potentially relevant to a broad range of allergic and inflammatory skin diseases. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  11. New approaches to organocatalysis based on C–H and C–X bonding for electrophilic substrate activation

    Directory of Open Access Journals (Sweden)

    Pavel Nagorny

    2016-12-01

    Full Text Available Hydrogen bond donor catalysis represents a rapidly growing subfield of organocatalysis. While traditional hydrogen bond donors containing N–H and O–H moieties have been effectively used for electrophile activation, activation based on other types of non-covalent interactions is less common. This mini review highlights recent progress in developing and exploring new organic catalysts for electrophile activation through the formation of C–H hydrogen bonds and C–X halogen bonds.

  12. Photochemical studies on aromatic γ,δ-epoxy ketones: efficient synthesis of benzocyclobutanones and indanones.

    Science.gov (United States)

    Shao, Yutian; Yang, Chao; Gui, Weijun; Liu, Yang; Xia, Wujiong

    2012-04-11

    Irradiation of terminal aromatic γ,δ-epoxy ketones with a 450 W UV lamp led to Norrish type II cyclization/semi-pinacol rearrangement cascade reaction which formed the benzocyclobutanones containing a full-carbon quaternary center, whereas irradiation of substituted aromatic γ,δ-epoxy ketones led to the indanones through a photochemical epoxy rearrangement and 1,5-biradicals cyclization tandem reaction. This journal is © The Royal Society of Chemistry 2012

  13. Fluorine-18-labelled molecules: synthesis and application in medical imaging

    International Nuclear Information System (INIS)

    Dolle, F.; Perrio, C.; Barre, L.; Lasne, M.C.; Le Bars, D.

    2006-01-01

    Positron emission tomography (PET) is one of the more powerful available techniques for medical imaging. It relies on the use of molecules labelled with a positron emitter (β + ). Among those emitters, fluorine-18, available from a cyclotron, is a radionuclide of choice because of its relatively long-half-life (109.8 min) and the relatively low energy of the emitted-positron. The electrophilic form of fluorine-18 ([ 18 F]F 2 or reagents derived from [ 18 F]F 2 ) is mainly used for hydrogen or metal substitutions on aromatic or vinylic carbons. The presence of the stable isotope (fluorine-19) in the radiotracers limits their use in medical imaging. The nucleophilic form of fluorine-18 (alkaline mono-fluoride, K[ 18 F]F, the most used), obtained from irradiation of enriched water, is widely used in aliphatic and (hetero)aromatic substitutions for the synthesis of radiotracers with high specific radioactivity. Some examples of radio-fluorinated tracers used in PET are presented, as well as some of their in vivo applications in human. (authors)

  14. Communication: Remarkable electrophilicity of the oxalic acid monomer: An anion photoelectron spectroscopy and theoretical study

    International Nuclear Information System (INIS)

    Buonaugurio, Angela; Graham, Jacob; Buytendyk, Allyson; Bowen, Kit H.; Ryder, Matthew R.; Gutowski, Maciej; Keolopile, Zibo G.; Haranczyk, Maciej

    2014-01-01

    Our experimental and computational results demonstrate an unusual electrophilicity of oxalic acid, the simplest dicarboxylic acid. The monomer is characterized by an adiabatic electron affinity and electron vertical detachment energy of 0.72 and 1.08 eV (±0.05 eV), respectively. The electrophilicity results primarily from the bonding carbon-carbon interaction in the singly occupied molecular orbital of the anion, but it is further enhanced by intramolecular hydrogen bonds. The well-resolved structure in the photoelectron spectrum is reproduced theoretically, based on Franck-Condon factors for the vibronic anion → neutral transitions

  15. Metallation of N-allenylpyrroles by superbase reagents. Synthesis of new N-substituted pyrroles

    International Nuclear Information System (INIS)

    Tarasova, O.A.; Brandsma, L.; Verkrajsse, Kh.D.; Mal'kina, A.G.; Trofimov, B.A.

    1996-01-01

    Metallation of N-allenylpyrrole by BuLi-Et 2 O (THP), BuLi-t-BuOK-THP superbases and reactions of carbanions formed with different electrophilic agents have been studied. Fundamental data on mutual influence of allene group and pyrrole ring have been obtained. Alpha-proton features the highest acidity and it is the first one to be replaced by metal. In BuLi excess (more than 3-fold) in ether or in BuLi-t-BuOK-THP system a through metallation of allene group occurs. New pyrroles functionally substituted in allene chain have been prepared. 19 refs.; 3 tabs

  16. Synthesis and biological evaluation of 2-substituted benzimidazole derivatives

    Directory of Open Access Journals (Sweden)

    Gurusamy Mariappan

    2015-09-01

    Full Text Available A novel series of 2-substituted benzimidazole derivatives (3a–3j were synthesized by the reaction of 2-chloro methyl benzimidazole with substituted primary aromatic amines. All the compounds were characterized by UV, IR, 1H NMR, mass spectral data and CHN elemental analysis. The synthesized derivatives were screened for analgesic and anti-inflammatory activities. All the compounds showed significant effect at 100 mg/kg p.o. and the experimental data are statistically significant at p < 0.01 level.

  17. Synthesis of 2-azetidinones substituted quinoline derivative

    Directory of Open Access Journals (Sweden)

    Mashelkar Uday C.

    2013-01-01

    Full Text Available Acetanilide is converted into 2-chloro-3-formyl quinoline by reacting with DMF-POCl3 at 80-90ºC and then condensed with aromatic primary amines to give Schiff bases (3a-3c. These Schiff bases are then reacted with acid chlorides in the presence of base in toluene to give 1, 3, 4-substituted 2-azetidinones.

  18. Oxidation kinetics of polycyclic aromatic hydrocarbons by permanganate

    Energy Technology Data Exchange (ETDEWEB)

    Forsey, S.P.; Thomson, N.R.; Barker, J.F. [University of Waterloo, Waterloo, ON (Canada). Dept. of Civil & Environmental Engineering

    2010-04-15

    The reactivity of permanganate towards polycyclic aromatics hydrocarbons (PAHs) is well known but little kinetic information is available. This study investigated the oxidation kinetics of a selected group of coal tar creosote compounds and alkylbenzenes in water using permanganate, and the correlation between compound reactivity and physical/chemical properties. The oxidation of naphthalene, phenanthrene, chrysene, 1-methylnaphthalene, 2-methylnaphthalene, acenaphthene, fluorene, carbazole isopropylbenzene, ethylbenzene and methylbenzene closely followed pseudo first-order reaction kinetics. The oxidation of pyrene was initially very rapid and did not follow pseudo first-order kinetics at early times. Fluoranthene was only partially oxidized and the oxidation of anthracene was too fast to be captured. Biphenyl, dibenzofuran, benzene and tert-butylbenzene were non-reactive under the study conditions. The oxidation rate was shown to increase with increasing number of polycyclic rings because less energy is required to overcome the aromatic character of a polycyclic ring than is required for benzene. Thus the rate of oxidation increased in the series naphthalene < phenanthrene < pyrene. The rate of side chain reactivity is controlled by the C-H bond strength. For the alkyl substituted benzenes an excellent correlation was observed between the reaction rate coefficients and bond dissociation energies, but for the substituted PAHs the relationship was poor. A trend was found between the reaction rate coefficients and the calculated heats of complexation indicating that significant ring oxidation occurred in addition to side chain oxidation. Clar's aromatic sextet theory was used to predict the relative stability of arenes towards ring oxidation by permanganate.

  19. Synthesis of deuterium-labeled analogs of the lipid hydroperoxide-derived bifunctional electrophile 4-oxo-2(E)-nonenal

    OpenAIRE

    Arora, Jasbir S.; Oe, Tomoyuki; Blair, Ian A.

    2011-01-01

    Lipid hydroperoxides undergo homolytic decomposition into the bifunctional 4-hydroxy-2(E)-nonenal and 4-oxo-2(E)-nonenal (ONE). These bifunctional electrophiles are highly reactive and can readily modify intracellular molecules including glutathione (GSH), deoxyribonucleic acid (DNA) and proteins. Lipid hydroperoxide-derived bifunctional electrophiles are thought to contribute to the pathogenesis of a number of diseases. ONE is an α,β-unsaturated aldehyde that can react in multiple ways and w...

  20. Energetics of aminomethylpyrimidines: An examination of the aromaticity of nitrogen heteromonocyclic derivatives

    International Nuclear Information System (INIS)

    Galvão, Tiago L.P.; Ribeiro da Silva, Maria D.M.C.; Ribeiro da Silva, Manuel A.V.

    2013-01-01

    Highlights: • Vapour pressure study of three aminomethylpyrimidines by Knudsen effusion technique. • Enthalpies of formation of three aminomethylpyrimidines by combustion calorimetry. • NICS, HOMA, Shannon analysis used as aromaticity criteria for three aminomethylpyrimidines. • QTAIMs properties, HOMO–LUMO gap, hardness, Kekulé mode and UV–Vis spectra are analyzed. • Benzene, pyridine and pyrimidine are taken as references for the aromaticity analysis. -- Abstract: The standard (p o = 0.1 MPa) molar enthalpies of formation, in the gaseous phase, at the reference temperature of 298.15 K, of 2-amino-4-methylpyrimidine ((98.1 ± 1.6) kJ · mol −1 ), 2-amino-4,6-dimethylpyrimidine ((55.9 ± 1.8) kJ · mol −1 ) and 4-amino-2,6-dimethylpyrimidine ((60.1 ± 1.8) kJ · mol −1 ) were calculated from the enthalpies of formation, in the crystalline phase, and enthalpies of sublimation, derived, respectively, from static bomb combustion calorimetry and Knudsen effusion technique results. In order to quantify the resonance effects arising from the substitution on the pyrimidine ring, hypothetical isodesmic reactions were used to analyze the experimental gaseous-phase enthalpies of formation. The aromaticity of benzene, pyridine, pyrimidine and the substituted pyrimidines was investigated in terms of magnetic (NICS), geometric (HOMA), electronic (Shannon aromaticity, QTAIMs ring critical point properties and HOMO–LUMO gap), reactive (hardness), vibrational (Kekulé mode) and spectroscopic (UV–Vis) properties

  1. Co-Aromatization of Methane with Olefins: The Role of Inner Pore and External Surface Catalytic Sites

    Energy Technology Data Exchange (ETDEWEB)

    Yung, Matthew M [National Renewable Energy Laboratory (NREL), Golden, CO (United States); He, Peng [University of Calgary; Jarvis, Jack [University of Calgary; Meng, Shijun [University of Calgary; Wang, Aiguo [University of Calgary; Kou, Shiyu [University of Calgary; Gatip, Richard [University of Calgary; Liu, Lijia [Soochow University; Song, Hua [University of Calgary

    2018-04-22

    The co-aromatization of methane with olefins is investigated using Ag-Ga/HZSM-5 as the catalyst at 400 degrees C. The presence of methane has a pronounced effect on the product distribution in terms of increased average carbon number and substitution index and decreased aromatic carbon fraction compared with its N2 environment counterpart. The participation of methane during the co-aromatization over the Ag-Ga/HZSM-5 catalyst diminishes as the co-fed olefin feedstock molecule becomes larger, from 1-hexene to 1-octene and 1-decene, in diameter. The effect of suppressed methane participation with larger olefinic molecules is not as significant when Ag-Ga/HY is employed as the catalyst, which might be attributed to the larger pore size of HY that gives more room to hold olefin and methane molecules within the inner pores and reduces the diffusion limitation of olefin molecules. The effect of olefin feedstock on the methane participation during the co-aromatization over Ag-Ga/HZSM-5 is experimentally evidenced by 13C and 2D NMR. The incorporation of the methane carbon atoms into the phenyl ring of product molecules is reduced significantly with larger co-fed olefins, whereas its incorporation into the substitution groups of the formed aromatic molecules is not notably affected, suggesting that the methane participation in the phenyl ring formation might preferably occur within inner pores, while its incorporation into substitution groups may mainly take place on external catalytic sites. This hypothesis is well supported by the product selectivity obtained over Ag-Ga/HZSM-5 catalysts prepared using conventional ZSM-5, ZSM-5 with the external catalytic sites deactivated, nanosize ZSM-5, ZSM-5 with a micro/meso pore structure and ZSM-5 with the inner pores blocked, and further confirmed by the isotopic labeling studies.

  2. Conformationally restrained aromatic analogues of fosmidomycin and FR900098.

    Science.gov (United States)

    Kurz, Thomas; Schlüter, Katrin; Pein, Miriam; Behrendt, Christoph; Bergmann, Bärbel; Walter, Rolf D

    2007-07-01

    The synthesis and in-vitro antimalarial activity of conformationally restrained bis(pivaloyloxymethyl) ester analogues of the natural product fosmidomycin is presented. In contrast to alpha-aryl-substituted analogues, conformationally restrained aromatic analogues exhibit only moderate in-vitro antimalarial activity against the chloroquine-sensitive strain 3D7 of Plasmodium falciparum. The most active derivative displays an IC(50) value of 47 microM.

  3. Chemometric characterization of the hydrogen bonding complexes of secondary amides and aromatic hydrocarbons

    Directory of Open Access Journals (Sweden)

    Jović Branislav

    2012-01-01

    Full Text Available The paper reports the results of the study of hydrogen bonding complexes between secondary amides and various aromatic hydrocarbons. The possibility of using chemometric methods was investigated in order to characterize N-H•••π hydrogen bonded complexes. Hierarchical clustering and Principal Component Analysis (PCA have been applied on infrared spectroscopic and Taft parameters of 43 N-substituted amide complexes with different aromatic hydrocarbons. Results obtained in this report are in good agreement with conclusions of other spectroscopic and thermodynamic analysis.

  4. Hepatic stellate cells lack AP-1 responsiveness to electrophiles and phorbol 12-myristate-13-acetate

    International Nuclear Information System (INIS)

    Reichard, John F.; Petersen, Dennis R.

    2004-01-01

    Stellate cell profibrotic gene induction and transdifferentiation are central events in liver fibrosis. Oxidative stress has been implicated as an activator of the transcription factors Nrf2 and AP-1 through shared kinase signaling pathways that also purportedly contribute to stellate cell activation. The present study examined the role of oxidative stress in ARE- and TRE-regulated gene induction in isolated hepatic stellate cells. Using a portion of the human Nqo1 promoter consisting of an ARE imbedded TRE, it was demonstrated that while the ARE was responsible for mediating inducible gene expression in response to the electrophiles 4-HNE and tBHQ, the TRE was refractory to induction by either electrophiles or PMA. It was demonstrated that stellate cells possess nuclear TRE-binding proteins that were identified as JunB, JunD, Fra1, and Fra2, which were unaffected by either electrophiles or PMA treatment. This report demonstrates that, in contrast to the ARE, the TRE and its binding cognate AP-1 did not mediate independent gene induction in hepatic stellate cells. This observation is significant given the presumed importance attributed to AP-1 in mediating profibrogenic gene expression

  5. Degradation of aromatic compounds in plants grown under aseptic conditions

    Energy Technology Data Exchange (ETDEWEB)

    Mithaishvili, T.; Ugrekhelidze, D.; Tsereteli, B.; Sadunishvili, T.; Kvesitadze, G. [Durmishidze Inst. of Biochemistry and Biotechnology, Academy of Sciences of Georgia, Tbilisi (Georgia); Scalla, R. [Lab. des Xenobiotiques, INRA, Toulouse (France)

    2005-02-01

    The aim of the work is to investigate the ability of higher plants to absorb and detoxify environmental pollutants - aromatic compounds via aromatic ring cleavage. Transformation of {sup 14}C specifically labelled benzene derivatives, [1-6-{sup 14}C]-nitrobenzene, [1-6-{sup 14}C]-aniline, [1-{sup 14}C]- and [7-{sup 14}C]-benzoic acid, in axenic seedlings of maize (Zea mays L.), kidney bean (Phaseolus vulgaris L.), pea (Pisum sativum L.) and pumpkin (Cucurbita pepo L.) were studied. After penetration in plants, the above xenobiotics are transformed by oxidative or reductive reactions, conjugation with cell endogenous compounds, and binding to biopolymers. The initial stage of oxidative degradation consists in hydroxylation reactions. The aromatic ring can then be cleaved and degraded into organic acids of the Krebs cycle. Ring cleavage is accompanied by {sup 14}CO{sub 2} evolution. Aromatic ring cleavage in plants has thus been demonstrated for different xenobiotics carrying different substitutions on their benzene ring. Conjugation with low molecular peptides is the main pathway of aromatic xenobiotics detoxification. Peptide conjugates are formed both by the initial xenobiotics (except nitrobenzene) and by intermediate transformation products. The chemical nature of the radioactive fragment and the amino acid composition of peptides participating in conjugation were identified. (orig.)

  6. Polycyclic aromatic hydrocarbons (PAHs) in a coal tar standard reference material - SRM 1597a updated

    Energy Technology Data Exchange (ETDEWEB)

    Wise, Stephen A.; Poster, Dianne L.; Rimmer, Catherine A.; Schubert, Patricia; Sander, Lane C.; Schantz, Michele M. [National Institute of Standards and Technology (NIST), Analytical Chemistry Division, Gaithersburg, MD (United States); Leigh, Stefan D. [National Institute of Standards and Technology (NIST), Statistical Engineering Division, Gaithersburg, MD (United States); Moessner, Stephanie [National Institute of Standards and Technology (NIST), Analytical Chemistry Division, Gaithersburg, MD (United States); GMP/Comparator Labs, Werthenstein Chemie AG, Industrie Nord, Schachen (Switzerland)

    2010-09-15

    SRM 1597 Complex Mixture of Polycyclic Aromatic Hydrocarbons from Coal Tar, originally issued in 1987, was recently reanalyzed and reissued as SRM 1597a with 34 certified, 46 reference, and 12 information concentrations (as mass fractions) for polycyclic aromatic hydrocarbons (PAHs) and polycyclic aromatic sulfur heterocycles (PASHs) including methyl-substituted PAHs and PASHs. The certified and reference concentrations (as mass fractions) were based on results of analyses of the coal tar material using multiple analytical techniques including gas chromatography/mass spectrometry on four different stationary phases and reversed-phase liquid chromatography. SRM 1597a is currently the most extensively characterized SRM for PAHs and PASHs. (orig.)

  7. Dendrimer encapsulated Silver nanoparticles as novel catalysts for reduction of aromatic nitro compounds

    Science.gov (United States)

    Asharani, I. V.; Thirumalai, D.; Sivakumar, A.

    2017-11-01

    Polyethylene glycol (PEG) core dendrimer encapsulated silver nanoparticles (AgNPs) were synthesized through normal chemical reduction method, where dendrimer acts as reducing and stabilizing agent. The encapsulated AgNPs were well characterized using TEM, DLS and XPS techniques. The synthesized AgNPs showed excellent catalytic activity towards the reduction of aromatic nitro compounds with sodium borohydride as reducing agent and the results substantiate that dendrimer encapsulated AgNPs can be an effective catalyst for the substituted nitro aromatic reduction reactions. Also the kinetics of different nitro compounds reductions was studied and presented.

  8. Synthesis of some fenchyl-substituted alkenes and enol-ethers containing 3-oxyphenyl substituents by the Barton-Kellogg reaction

    International Nuclear Information System (INIS)

    Ciscato, Luiz Francisco M.L.; Bartoloni, Fernando H.; Baader, Wilhelm Josef; Bastos, Erick L.; Guenther, Wolfgang; Weiss, Dieter; Beckert, Rainer

    2010-01-01

    The synthesis of one fenchyl-substituted alkene and two enol-ethers, containing 3-oxyphenyl substituents by the Barton-Kellogg reaction is described. The tri-substituted aromatic fenchylalkene 1a was prepared in 53% yield from thiofenchone and a diazoanisole; whereas enol-ethers 1b and 1c were obtained (95 and 75% yield, respectively) using an inverse approach based on diazofenchone and aromatic thionoesters. A mixture of Z and E isomers was obtained in all cases; isomer attribution and quantification has been carried out by analysis of NMR spectroscopic data assisted by theoretical calculations (E/Z ratio: 1a = 0.72, 1b = 2.2, 1c = 1.8). Reaction proceeds with low stereoselectivity leading to the preferential formation of diastereoisomeric olefins and enol-ethers where the aromatic substituent resides at the side of the two fenchyl methyl groups. (author)

  9. Synthesis of some fenchyl-substituted alkenes and enol-ethers containing 3-oxyphenyl substituents by the Barton-Kellogg reaction

    Energy Technology Data Exchange (ETDEWEB)

    Ciscato, Luiz Francisco M.L.; Bartoloni, Fernando H.; Baader, Wilhelm Josef, E-mail: wjbaader@iq.usp.b [Universidade de Sao Paulo (USP), SP (Brazil). Inst. de Quimica. Dept. de Quimica Fundamental; Bastos, Erick L. [Universidade Federal do ABC (UFABC), Santo Andre, SP (Brazil). Centro de Ciencias Naturais e Humanas; Guenther, Wolfgang; Weiss, Dieter; Beckert, Rainer [Friedrich-Schiller Universitaet Jena (Germany). Institut fuer Organische Chemie und Makromolekulare Chemie

    2010-07-01

    The synthesis of one fenchyl-substituted alkene and two enol-ethers, containing 3-oxyphenyl substituents by the Barton-Kellogg reaction is described. The tri-substituted aromatic fenchylalkene 1a was prepared in 53% yield from thiofenchone and a diazoanisole; whereas enol-ethers 1b and 1c were obtained (95 and 75% yield, respectively) using an inverse approach based on diazofenchone and aromatic thionoesters. A mixture of Z and E isomers was obtained in all cases; isomer attribution and quantification has been carried out by analysis of NMR spectroscopic data assisted by theoretical calculations (E/Z ratio: 1a = 0.72, 1b = 2.2, 1c = 1.8). Reaction proceeds with low stereoselectivity leading to the preferential formation of diastereoisomeric olefins and enol-ethers where the aromatic substituent resides at the side of the two fenchyl methyl groups. (author)

  10. Electrophilic dark matter with dark photon: From DAMPE to direct detection

    Science.gov (United States)

    Gu, Pei-Hong; He, Xiao-Gang

    2018-03-01

    The electron-positron excess reported by the DAMPE collaboration recently may be explained by an electrophilic dark matter (DM). A standard model singlet fermion may play the role of such a DM when it is stabilized by some symmetries, such as a dark U(1)X gauge symmetry, and dominantly annihilates into the electron-positron pairs through the exchange of a scalar mediator. The model, with appropriate Yukawa couplings, can well interpret the DAMPE excess. Naively one expects that in this type of models the DM-nucleon cross section should be small since there is no tree-level DM-quark interactions. We however find that at one-loop level, a testable DM-nucleon cross section can be induced for providing ways to test the electrophilic model. We also find that a U (1) kinetic mixing can generate a sizable DM-nucleon cross section although the U(1)X dark photon only has a negligible contribution to the DM annihilation. Depending on the signs of the mixing parameter, the dark photon can enhance/reduce the one-loop induced DM-nucleon cross section.

  11. Synthesis of geranylhydroquinone derivatives with potential cytotoxic activity

    Energy Technology Data Exchange (ETDEWEB)

    Baeza, Evelyn; Catalan, Karen; Pena-Cortes, Hugo; Espinoza, Luis, E-mail: luis.espinozac@usm.cl [Departamento de Quimica, Universidad Tecnica Federico Santa Maria, Valparaiso (Chile); Villena, Joan [Facultad de Medicina, Universidad de Valparaiso, Centro Regional de Estudios en Alimentos Saludables, Valparaiso (Chile); Carrasco, Hector [Departamento de Ciencias Quimicas, Universidad Andres Bello, Campus Vina del Mar (Chile)

    2012-07-01

    Natural geranylhydroquinone 1 and geranyl-p-methoxyphenol 2 were prepared by Electrophilic Aromatic Substitution (EAS) reactions between geraniol and 1,4-hydroquinone or p-methoxyphenol respectively, using BF{sub 3} {center_dot}Et{sub 2}O as a catalyst. Furthermore, natural geranylquinone 3, geranyl-1,4-dimethoxyquinone 4 and the new geranyl-4-methoxyphenyl acetate 5 were obtained by chemical transformations of 1 and 2. The compounds were evaluated for their in vitro cytotoxicity activities against cultured human cancer cells of PC-3 human prostate cancer, MCF-7 and MDA-MB-231 breast carcinoma, and Dermal Human ibroblasts DHF. IC{sub 50} values were in the {mu}M range. (author)

  12. Topical electrophilic nitro-fatty acids potentiate cutaneous inflammation.

    Science.gov (United States)

    Mathers, Alicia R; Carey, Cara D; Killeen, Meaghan E; Salvatore, Sonia R; Ferris, Laura K; Freeman, Bruce A; Schopfer, Francisco J; Falo, Louis D

    2018-02-01

    Endogenous electrophilic fatty acids mediate anti-inflammatory responses by modulating metabolic and inflammatory signal transduction and gene expression. Nitro-fatty acids and other electrophilic fatty acids may thus be useful for the prevention and treatment of immune-mediated diseases, including inflammatory skin disorders. In this regard, subcutaneous (SC) injections of nitro oleic acid (OA-NO 2 ), an exemplary nitro-fatty acid, inhibit skin inflammation in a model of allergic contact dermatitis (ACD). Given the nitration of unsaturated fatty acids during metabolic and inflammatory processes and the growing use of fatty acids in topical formulations, we sought to further study the effect of nitro-fatty acids on cutaneous inflammation. To accomplish this, the effect of topically applied OA-NO 2 on skin inflammation was evaluated using established murine models of contact hypersensitivity (CHS). In contrast to the effects of subcutaneously injected OA-NO 2 , topical OA-NO 2 potentiated hapten-dependent inflammation inducing a sustained neutrophil-dependent inflammatory response characterized by psoriasiform histological features, increased angiogenesis, and an inflammatory infiltrate that included neutrophils, inflammatory monocytes, and γδ T cells. Consistent with these results, HPLC-MS/MS analysis of skin from psoriasis patients displayed a 56% increase in nitro-conjugated linoleic acid (CLA-NO 2 ) levels in lesional skin compared to non-lesional skin. These results suggest that nitro-fatty acids in the skin microenvironment are products of cutaneous inflammatory responses and, in high local concentrations, may exacerbate inflammatory skin diseases. Copyright © 2017 Elsevier Inc. All rights reserved.

  13. Effect of aromatization of the ring on intramolecular H-bond in 3-hydroxy-4-formylo derivatives of fulvene

    Science.gov (United States)

    Oziminski, Wojciech P.; Krygowski, Tadeusz M.

    2011-06-01

    DFT optimization of H-bonded 3-hydroxy-4-formylo derivatives of fulvene aromatized by amino substitution at C6 or by complexation with Li atom was performed using the B3LYP functional together with 6-311+G(d,p) basis set. Several aromaticity indicators (HOMA, NICS, pEDA and Shannon aromaticity) confirm an increase of aromaticity in the sequence: fulvene, 6-aminofulvene, Li-complex with fulvene and in the case of H-bonded 3-hydroxy-4-formylo derivatives, exhibited in the same sequence an increase of H-bond strength estimated by direct comparison of energy for H-bonded and open conformations, as well as by using AIM based electron densities at bond critical point.

  14. Copper-Catalyzed Electrophilic Amination of Organoaluminum Nucleophiles with O-Benzoyl Hydroxylamines.

    Science.gov (United States)

    Zhou, Shuangliu; Yang, Zhiyong; Chen, Xu; Li, Yimei; Zhang, Lijun; Fang, Hong; Wang, Wei; Zhu, Xiancui; Wang, Shaowu

    2015-06-19

    A copper-catalyzed electrophilic amination of aryl and heteroaryl aluminums with N,N-dialkyl-O-benzoyl hydroxylamines that affords the corresponding anilines in good yields has been developed. The catalytic reaction proceeds very smoothly under mild conditions and exhibits good substrate scope. Moreover, the developed catalytic system is also well suited for heteroaryl aluminum nucleophiles, providing facile access to heteroaryl amines.

  15. Electrophilic properties of patulin. Adduct structures and reaction pathways with 4-bromothiophenol and other model nucleophiles.

    Science.gov (United States)

    Fliege, R; Metzler, M

    2000-05-01

    The mycotoxin patulin (PAT) is believed to exert its cytotoxic and chromosome-damaging effects by forming covalent adducts with essential cellular thiols. Since the chemical structures of such adducts are unknown to date, we have studied the reaction of PAT and its O-acetylated derivative with the monofunctional thiol model compound 4-bromothiophenol (BTP), which was chosen due to analytical advantages. By means of analytical and preparative high-performance liquid chromatography, 16 adducts of PAT and 3 adducts of acetyl-PAT were isolated and their chemical structures elucidated by (1)H and (13)C NMR, IR, and UV spectroscopy. Time course studies and analysis of daughter product formation from isolated intermediate adducts led to a detailed scheme for the reaction of PAT with BTP. The structures of adducts of PAT formed with other model nucleophiles, e. g., the aliphatic thiol 2-mercaptoethanol and the aromatic amine 4-bromoaniline, were also elucidated and found to corroborate the reaction scheme. In addition, one further reaction pathway was observed with 2-mercaptoethanol, which appears to be independent from those found for BTP. Our study with model nucleophiles provides insights into the electrophilic reactivity of PAT and proved to be useful for the structure elucidation of PAT adducts with biological nucleophiles of toxicological relevance, as will be reported by Fliege and Metzler [(2000) Chem. Res. Toxicol. 13, 373-381].

  16. Polar Diels-Alder reactions using electrophilic nitrobenzothiophenes. A combined experimental and DFT study

    Science.gov (United States)

    Della Rosa, Claudia D.; Mancini, Pedro M. E.; Kneeteman, Maria N.; Lopez Baena, Anna F.; Suligoy, Melisa A.; Domingo, Luis R.

    2015-01-01

    The reactions between 2- and 3-nitrobenzothiophenes with three dienes of different nucleophilicity, 1-methoxy-3-trimethylsilyloxy-1,3-butadiene, 1-trimethylsilyloxy-1,3-butadiene and isoprene developed in anhydrous benzene and alternative under microwave irradiation with molecular solvents or in free solvent conditions, respectively, for produce dibenzothiophenes permit to conclude that both nitroheterocycles act as electrophile with the cited dienes. In the cases of the dienes 1-methoxy-3-trimethylsilyloxy-1,3-butadiene and 1-trimethylsilyloxy-1,3-butadiene which posses major nucleophilicity the observed product is the normal cycloaddition one. However when the diene is isoprene the product with both electrophiles follow the hetero Diels-Alder way. These reactions are considered polar cycloaddition reactions and the yields are reasonables. Moreover the polar Diels-Alder reactions of nitrobenzothiophenes with electron rich dienes 1-trimethylsilyloxy-1,3-butadiene have been theoretically studied using DFT methods.

  17. Journal of Chemical Sciences | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    The electrophilic behaviour of metal-bound nitrosyl has been proved in one case by reacting with a bicyclic ketone, camphor, containing an active methylene group and an arylhydrazone with an active methine group. Diazotization of primary aromatic amines with strongly electrophilic mononitrosyl complexes in acetonotrile ...

  18. Polycyclic aromatic hydrocarbon metabolism in mullets, Chelon labrosus, treated by polychlorinated biphenyls

    International Nuclear Information System (INIS)

    Narbonne, J.F.; Suteau, P.; Daubeze, M.; Audy, C.

    1987-01-01

    Contamination of the ocean by hydrocarbons has become a major environmental problem. Consequently, it is not surprising that residues of potentially toxic xenobiotics, such as benzo(a)pyrene (B(a)P), are present in marine species used as human food. The oxidative metabolism of aromatic hydrocarbons proceeds via intermediate arene oxides. Some of these metabolites are very reactive electrophiles and may interact with cellular macromolecules such as proteins, DNA and RNA. Thus, the ability of an organism to further metabolize arene oxides can be an important protective mechanism against the possible toxic effect of these molecules. The existence of hepatic cytochrome P-450 dependent monooxygenase activities in fish is now well established. The exposure of fish to polychlorinated biphenyls (PCB) increases both the monooxygenase activities and the total amount of cytochrome P-450 in the microsomal fractions of fish liver. The purpose of this study was to compare the toxication-detoxication balance in both control and PCB induced estuarine fish (Grey mullets)

  19. Rational synthesis of AB-type N-substituted core-functionalized naphthalene diimides (cNDIs).

    Science.gov (United States)

    Berezin, Andrey A; Sciutto, Andrea; Demitri, Nicola; Bonifazi, Davide

    2015-04-17

    Acid-mediated transformation of tetraethyl 2,6-diethoxynaphthalene-1,4,5,8-tetracarboxylate selectively affords the core-substituted naphthalene-anhydride-ester (cNAE) in quantitative yield. This anhydride can be selectively converted into hetero-N-substituted core-functionalized naphthalene diimides (cNDIs) through sequential condensation reactions in the presence of the precursor amine with very high isolated yields over four steps. The approach can be applied to prepare a large variety of heterocyclic, aromatic, and aliphatic heterodiimides.

  20. Olives and olive oil are sources of electrophilic fatty acid nitroalkenes.

    Directory of Open Access Journals (Sweden)

    Marco Fazzari

    Full Text Available Extra virgin olive oil (EVOO and olives, key sources of unsaturated fatty acids in the Mediterranean diet, provide health benefits to humans. Nitric oxide (•NO and nitrite (NO2 (--dependent reactions of unsaturated fatty acids yield electrophilic nitroalkene derivatives (NO2-FA that manifest salutary pleiotropic cell signaling responses in mammals. Herein, the endogenous presence of NO2-FA in both EVOO and fresh olives was demonstrated by mass spectrometry. The electrophilic nature of these species was affirmed by the detection of significant levels of protein cysteine adducts of nitro-oleic acid (NO2-OA-cysteine in fresh olives, especially in the peel. Further nitration of EVOO by NO2 (- under acidic gastric digestive conditions revealed that human consumption of olive lipids will produce additional nitro-conjugated linoleic acid (NO2-cLA and nitro-oleic acid (NO2-OA. The presence of free and protein-adducted NO2-FA in both mammalian and plant lipids further affirm a role for these species as signaling mediators. Since NO2-FA instigate adaptive anti-inflammatory gene expression and metabolic responses, these redox-derived metabolites may contribute to the cardiovascular benefits associated with the Mediterranean diet.

  1. The labelling of 2-oxoquazepam with electrophilic 18F

    International Nuclear Information System (INIS)

    Duelfer, T.; Johnstroem, P.; Stone-Elander, S.

    1991-01-01

    2-Oxoquazepam, 7-chloro-1-(2,2,2-trifluoroethyl)-1,3-dihydro-5-(2-fluorophenyl)-2H-1,4-benzo-diazepine-2-one, is a benzodiazepine agonist. It has been shown to bind in vitro with a higher affinity to benzodiazepine type 1 receptors than to type 2 receptors. Here we report the synthesis of a trimethylin precursor and demonstrate the feasibility of using it for radiolabelling acid- and base-sensitive benzodiazepine structures such as 2-oxoquazepam. Conversions of the electrophilic fluorine to [ 18 F]-2-oxoquazepam on the order 20-25% were obtained. (author)

  2. Kinetics of exchange reaction between neodymium(3) transcyclohexanediaminetetraacetate and europium(3)- and holmium(3) aquo-ions in the H/sub 2/O and D/sub 2/O solutions

    Energy Technology Data Exchange (ETDEWEB)

    Nikitenko, S.I.; Martynenko, L.I.; Pechurova, N.I.; Spitsyn, V.I. (Moskovskij Gosudarstvennyj Univ. (USSR))

    1983-10-01

    The exchange reaction between central ions in the NdD/sup -/Ln'/sup 3 +/ systems, where Ln'/sup 3 +/ is a substituting cation (Eu/sup 3 +/ and Ho/sup 3 +/, D/sup 4/=cyclohexanediaminetetraacetate) is studied and the electrophilic substitution mechanism is considered. To study the kinetic isotope effects, the reagents have been solved in heavy water containing 99.9% D/sub 2/O. The electrophilic substitution in the indicated systems proceeds through the dissociative mechanism catalyzed by protons and via the spontaneous dissociation mechanism. The exchange via the acid-catalyzed mechanism is limited by the intermediate protonated complex decay. The associative mechanism of the electrophilic exchange in the studied systems is not realized.

  3. 2-Diazo-1-phenyl-2-((trifluoromethyl)sulfonyl)ethan-1-one: Another Utility for Electrophilic Trifluoromethylthiolation Reactions.

    Science.gov (United States)

    Huang, Zhongyan; Okuyama, Kenta; Wang, Chen; Tokunaga, Etsuko; Li, Xiaorui; Shibata, Norio

    2016-06-01

    2-Diazo-1-phenyl-2-((trifluoromethyl)sulfonyl)ethan-1-one (diazo-triflone) ( 2 ) is not only a building block but also a reagent. In this study, diazo-triflone, which was originally used for the synthesis of β-lactam triflones as a trifluoromethanesulfonyl (SO 2 CF 3 ) building block under catalyst-free thermal conditions, is redisclosed as an effective electrophilic trifluoromethylthiolation reagent under copper catalysis. A broad set of enamines, indoles, β-keto esters, pyrroles, and anilines were nicely transformed into corresponding trifluoromethylthio (SCF 3 ) compounds in good to high yields by diazo-triflone under copper catalysis via an electrophilic-type reaction. A coupling-type trifluoromethylthiolation reaction of aryl iodides was also realized by diazo-triflone in acceptable yields.

  4. Rate constants for some electrophilic reactions of benzyl, benzhydryl, and trityl cations in solution

    International Nuclear Information System (INIS)

    Ujdak, R.J.; Jones, R.L.; Dorfman, L.M.

    1976-01-01

    Absolute rate constants have been determined by the pulse radiolysis technique for several electrophilic reactions of the benzyl, the benzhydryl, and the trityl cation in 1,2-dichloroethane solution. The rate constants for the reactions of these carbonium ions with chloride ion, with bromide ion, and with iodide ion are all very nearly the same, namely 6 x 10 10 M -1 s -1 at 24 0 C. The values very likely represent the diffusion controlled limit for the ion combination reactions. The rate constants for the reactions with triethylamine, tri-n-propylamine, and tri-n-butylamine range from 2.0 x 10 9 to 7 x 10 6 M -1 s -1 at 24 0 C. With increasing phenyl substitution, the decreasing trend in the magnitude of the rate constant is consistent with the combined electronic and steric effects. With increasing size of the amine, the decrease in the value of the rate constant seems to indicate that the steric effect predominates. The values of the rate constants for reactions of benzyl and benzhydryl cation with methanol, ethanol, and 2-propanol indicate the following. The rate constant is higher for reaction with the alcohol dimer in solution than with alcohol monomer. The rate constants for reaction with alcohol monomer have values of 1 x 10 8 M -1 s -1 or lower

  5. Tetrakis(4-tert-butylphenyl) substituted and fused quinoidal porphyrins

    KAUST Repository

    Zeng, Wangdong

    2012-01-01

    4-tert-Butylphenyl-substituted and fused quinoidal porphyrins 1 and 2 are prepared for the first time. They show (1) intense one-photon absorption in the far-red/near-infrared region, (2) enhanced two-photon absorption compared with aromatic porphyrin monomers, and (3) amphoteric redox behavior. Their geometry and electronic structure are studied by DFT calculations. This journal is © 2012 The Royal Society of Chemistry.

  6. Influence of the physicochemical and aromatic properties on the chemical reactivity and its relation with carcinogenic and anticoagulant effect of 17β-aminoestrogens

    Energy Technology Data Exchange (ETDEWEB)

    Soriano-Correa, Catalina, E-mail: socc@puma2.zaragoza.unam.mx [Química Computacional, FES-Zaragoza, Universidad Nacional Autónoma de México (UNAM), Iztapalapa, Mexico City (Mexico); Raya, Angélica [Unidad Profesional Interdisciplinaria de Ingeniería Campus Guanajuato, Instituto Politécnico Nacional (IPN), Silao de la Victoria, Guanajuato (Mexico); Barrientos-Salcedo, Carolina [Laboratorio de Química Médica y Quimiogenómica, Facultad de Bioanálisis Campus Veracruz - Boca del Río, Universidad Veracruzana, Veracruz (Mexico); Esquivel, Rodolfo O. [Departamento de Química, Universidad Autónoma Metropolitana-Iztapalapa (UAM-Iztapalapa), Mexico City (Mexico)

    2014-06-25

    Highlights: • The aromatic A-ring of 17β-aminoestrogens contribute to its anticoagulant effect. • The electron-donor substituent groups favored the basicity of 17β-aminoestrogens. • The physicochemical properties are important in the carcinogenic effect of anticoagulant molecules. - Abstract: Activity of steroid hormones is dependent upon a number of factors, as solubility, transport and metabolism. The functional differences caused by structural modifications could exert an influence on the chemical reactivity and biological effect. The goal of this work is to study the influence of the physicochemical and aromatic properties on the chemical reactivity and its relation with the carcinogenic risk that can associate with the anticoagulant effect of 17β-aminoestrogens using quantum-chemical descriptors at the DFT-B3LYP, BH and HLYP and M06-2X levels. The relative acidity of (H1) of the hydroxyl group increases with electron-withdrawing groups. Electron-donor groups favor the basicity. The steric hindrance of the substituents decreases the aromatic character and consequently diminution the carcinogenic effect. Density descriptors: hardness, electrophilic index, atomic charges, molecular orbitals, electrostatic potential and their geometric parameters permit analyses of the chemical reactivity and physicochemical features and to identify some reactive sites of 17β-aminoestrogens.

  7. Finite temperature grand canonical ensemble study of the minimum electrophilicity principle.

    Science.gov (United States)

    Miranda-Quintana, Ramón Alain; Chattaraj, Pratim K; Ayers, Paul W

    2017-09-28

    We analyze the minimum electrophilicity principle of conceptual density functional theory using the framework of the finite temperature grand canonical ensemble. We provide support for this principle, both for the cases of systems evolving from a non-equilibrium to an equilibrium state and for the change from one equilibrium state to another. In doing so, we clearly delineate the cases where this principle can, or cannot, be used.

  8. Nitrated Fatty Acids Reverse Cigarette Smoke-Induced Alveolar Macrophage Activation and Inhibit Protease Activity via Electrophilic S-Alkylation.

    Science.gov (United States)

    Reddy, Aravind T; Lakshmi, Sowmya P; Muchumarri, Ramamohan R; Reddy, Raju C

    2016-01-01

    Nitrated fatty acids (NFAs), endogenous products of nonenzymatic reactions of NO-derived reactive nitrogen species with unsaturated fatty acids, exhibit substantial anti-inflammatory activities. They are both reversible electrophiles and peroxisome proliferator-activated receptor γ (PPARγ) agonists, but the physiological implications of their electrophilic activity are poorly understood. We tested their effects on inflammatory and emphysema-related biomarkers in alveolar macrophages (AMs) of smoke-exposed mice. NFA (10-nitro-oleic acid or 12-nitrolinoleic acid) treatment downregulated expression and activity of the inflammatory transcription factor NF-κB while upregulating those of PPARγ. It also downregulated production of inflammatory cytokines and chemokines and of the protease cathepsin S (Cat S), a key mediator of emphysematous septal destruction. Cat S downregulation was accompanied by decreased AM elastolytic activity, a major mechanism of septal destruction. NFAs downregulated both Cat S expression and activity in AMs of wild-type mice, but only inhibited its activity in AMs of PPARγ knockout mice, pointing to a PPARγ-independent mechanism of enzyme inhibition. We hypothesized that this mechanism was electrophilic S-alkylation of target Cat S cysteines, and found that NFAs bind directly to Cat S following treatment of intact AMs and, as suggested by in silico modeling and calculation of relevant parameters, elicit S-alkylation of Cys25 when incubated with purified Cat S. These results demonstrate that NFAs' electrophilic activity, in addition to their role as PPARγ agonists, underlies their protective effects in chronic obstructive pulmonary disease (COPD) and support their therapeutic potential in this disease.

  9. Assessment of benzophenone-4 reactivity with free chlorine by liquid chromatography quadrupole time-of-flight mass spectrometry.

    Science.gov (United States)

    Negreira, N; Rodríguez, I; Rodil, R; Cela, R

    2012-09-19

    The stability of the UV filter benzophenone-4 (BP-4) in free chlorine-containing water was investigated, for the first time, by liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QqTOF-MS). High mass accuracy and resolution capabilities of this hybrid mass spectrometer were used for the reliable assignation of empirical formulae and chemical structures of BP-4 derivatives. Time-course profiles of the parent compound and its by-products were simultaneously recorded by direct injection of sample aliquots, after quenching the excess of chlorine, in the LC-QqTOF-MS system. At neutral pHs, in excess of chlorine, BP-4 showed a limited stability fitting a pseudo-first-order degradation kinetics. A noticeable reduction in the half-lives of BP-4 was observed when increasing the sample pH between 6 and 8 units and also in presence of bromide traces. The reaction pathway of this UV filter involved a first electrophilic substitution of hydrogen per chlorine (or bromide) in the phenolic ring, followed by oxidation of the carbonyl moiety to an ester group, which induced a further electrophilic substitution in the same aromatic ring. Above reactions were also noticed when mixing a BP-4 containing personal care product with chlorinated tap water and in chlorinated swimming pool and sewage water, previously spiked with a BP-4 standard. Copyright © 2012 Elsevier B.V. All rights reserved.

  10. Evaluation of the Aromaticity of a Non-Planar Carbon Nano-Structure by Nucleus-Independent Chemical Shift Criterion: Aromaticity of the Nitrogen- Doped Corannulene

    Directory of Open Access Journals (Sweden)

    A. Reisi-Vanani

    2014-04-01

    Full Text Available Substitution of two or four carbon atoms by nitrogen in the corannulene molecule as a carbon nanostructure was done and the obtained structures were optimized at MP2/6-31G(d level of theory. Calculations of the nucleus-independent chemical shift (NICS were performed to analyze the aromaticity of the corannulene rings and its derivatives upon doping with N at B3LYP/6-31G(d level of theory. Results showed NICS values in six-membered and five-membered rings of two and four N atoms doped corannulene are different and very dependent to number and position of the N atoms. The values of the mean NICS of all N-doped structures are more positive than intact corannulene that show insertion of N atom to the structures causes to decreasing aromaticity of them.

  11. Characterizing Chemical Similarity with Vibrational Spectroscopy: New Insights into the Substituent Effects in Monosubstituted Benzenes.

    Science.gov (United States)

    Tao, Yunwen; Zou, Wenli; Cremer, Dieter; Kraka, Elfi

    2017-10-26

    A novel approach is presented to assess chemical similarity based the local vibrational mode analysis developed by Konkoli and Cremer. The local mode frequency shifts are introduced as similarity descriptors that are sensitive to any electronic structure change. In this work, 59 different monosubstituted benzenes are compared. For a subset of 43 compounds, for which experimental data was available, the ortho-/para- and meta-directing effect in electrophilic aromatic substitution reactions could be correctly reproduced, proving the robustness of the new similarity index. For the remaining 16 compounds, the directing effect was predicted. The new approach is broadly applicable to all compounds for which either experimental or calculated vibrational frequency information is available.

  12. DISSOCIATIVE PHOTOIONIZATION OF POLYCYCLIC AROMATIC HYDROCARBON MOLECULES CARRYING AN ETHYNYL GROUP

    Energy Technology Data Exchange (ETDEWEB)

    Rouillé, G.; Krasnokutski, S. A.; Fulvio, D.; Jäger, C. [Laboratory Astrophysics Group of the Max Planck Institute for Astronomy at the Friedrich Schiller University Jena, Institute of Solid State Physics, Helmholtzweg 3, D-07743 Jena (Germany); Henning, Th. [Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Garcia, G. A.; Tang, X.-F.; Nahon, L., E-mail: cornelia.jaeger@uni-jena.de [Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin BP 48, F-91192 Gif-sur-Yvette Cedex (France)

    2015-09-10

    The life cycle of the population of interstellar polycyclic aromatic hydrocarbon (PAH) molecules depends partly on the photostability of the individual species. We have studied the dissociative photoionization of two ethynyl-substituted PAH species, namely, 9-ethynylphenanthrene and 1-ethynylpyrene. Their adiabatic ionization energy and the appearance energy of fragment ions have been measured with the photoelectron photoion coincidence spectroscopy technique. The adiabatic ionization energy has been found at 7.84 ± 0.02 eV for 9-ethynylphenanthrene and at 7.41 ± 0.02 eV for 1-ethynylpyrene. These values are similar to those determined for the corresponding non-substituted PAH molecules phenanthrene and pyrene. The appearance energy of the fragment ion indicative of the loss of a H atom following photoionization is also similar for either ethynyl-substituted PAH molecule and its non-substituted counterpart. The measurements are used to estimate the critical energy for the loss of a H atom by the PAH cations and the stability of ethynyl-substituted PAH molecules upon photoionization. We conclude that these PAH derivatives are as photostable as the non-substituted species in H i regions. If present in the interstellar medium, they may play an important role in the growth of interstellar PAH molecules.

  13. Activity relationships for aromatic crown ethers

    International Nuclear Information System (INIS)

    Wilson, Mark James

    1998-01-01

    This thesis involves an investigation of aromatic crown ethers and a study of their binding constants for alkali metals. The study was motivated by the current needs of the semiconductor industry to improve the scavenging of mobile ions from fabricated circuits. A number of aromatic crown ethers have been sulphonated in an attempt to improve their water solubility and cation binding activity. These materials have been extensively studied and their binding activity determined. In collaboration with a molecular modelling study, the effect of ionisable sulphonate groups on the macrocycles' behaviour has been investigated. The broader issue of the effect of substituents in aromatic crown ethers has also been studied with the preparation of a wide range of substituted crown ethers. The cation binding activity of these materials has been found to bear a simple relationship to the electron withdrawing nature of the aromatic substituents. This relationship can be accurately monitored using electronic charge densities from molecular modelling and this rational has been applied to the study of proton ionisable and lariating crown ethers. The incorporation of crown ethers into polyamic acid and polyimide frameworks has also been investigated, where the resulting materials have been found to exhibit unusual cation binding and uptake properties. These results imply that the combination of the crown ethers' macrocycle and adjacent carboxylic acid residues, from the polyamic acids, are conducive to effective cationic binding. NMR measurements, in conjunction with molecular modelling, have been used to explore the geometry changes encountered as the crown ether goes from it's uncomplexed to its complexed state. The energy requirement for these geometry changes has subsequently been used to examine the cation selectivity of these materials. The electronic charge changes associated with the complexation have also been investigated and correlated with the theoretical results. (author)

  14. Rapid Microwave-Assisted Copper-Catalyzed Nitration of Aromatic Halides with Nitrite Salts

    Energy Technology Data Exchange (ETDEWEB)

    Paik, Seung Uk; Jung, Myoung Geun [Keimyung University, Daegu (Korea, Republic of)

    2012-02-15

    A rapid and efficient copper-catalyzed nitration of aryl halides has been established under microwave irradiation. The catalytic systems were found to be the most effective with 4-substituted aryl iodides leading to nearly complete conversions. Nitration of aromatic compounds is one of the important industrial processes as underlying intermediates in the manufacture of a wide range of chemicals such as dyes, pharmaceuticals, agrochemicals and explosives. General methods for the nitration of aromatic compounds utilize strongly acidic conditions employing nitric acid or a mixture of nitric and sulfuric acids, sometimes leading to problems with poor regioselectivity, overnitration, oxidized byproducts and excess acid waste in many cases of functionalized aromatic compounds. Several other nitrating agents or methods avoiding harsh reaction conditions have been explored using metal nitrates, nitrite salts, and ionic liquid-mediated or microwave-assisted nitrations. Recently, copper or palladium compounds have been successfully used as efficient catalysts for the arylation of amines with aryl halides under mild conditions.

  15. Rapid Microwave-Assisted Copper-Catalyzed Nitration of Aromatic Halides with Nitrite Salts

    International Nuclear Information System (INIS)

    Paik, Seung Uk; Jung, Myoung Geun

    2012-01-01

    A rapid and efficient copper-catalyzed nitration of aryl halides has been established under microwave irradiation. The catalytic systems were found to be the most effective with 4-substituted aryl iodides leading to nearly complete conversions. Nitration of aromatic compounds is one of the important industrial processes as underlying intermediates in the manufacture of a wide range of chemicals such as dyes, pharmaceuticals, agrochemicals and explosives. General methods for the nitration of aromatic compounds utilize strongly acidic conditions employing nitric acid or a mixture of nitric and sulfuric acids, sometimes leading to problems with poor regioselectivity, overnitration, oxidized byproducts and excess acid waste in many cases of functionalized aromatic compounds. Several other nitrating agents or methods avoiding harsh reaction conditions have been explored using metal nitrates, nitrite salts, and ionic liquid-mediated or microwave-assisted nitrations. Recently, copper or palladium compounds have been successfully used as efficient catalysts for the arylation of amines with aryl halides under mild conditions

  16. Extreme halophilic alcohol dehydrogenase mediated highly efficient syntheses of enantiopure aromatic alcohols.

    Science.gov (United States)

    Alsafadi, Diya; Alsalman, Safaa; Paradisi, Francesca

    2017-11-07

    Enzymatic synthesis of enantiopure aromatic secondary alcohols (including substituted, hetero-aromatic and bicyclic structures) was carried out using halophilic alcohol dehydrogenase ADH2 from Haloferax volcanii (HvADH2). This enzyme showed an unprecedented substrate scope and absolute enatioselectivity. The cofactor NADPH was used catalytically and regenerated in situ by the biocatalyst, in the presence of 5% ethanol. The efficiency of HvADH2 for the conversion of aromatic ketones was markedly influenced by the steric and electronic factors as well as the solubility of ketones in the reaction medium. Furthermore, carbonyl stretching band frequencies ν (C[double bond, length as m-dash]O) have been measured for different ketones to understand the effect of electron withdrawing or donating properties of the ketone substituents on the reaction rate catalyzed by HvADH2. Good correlation was observed between ν (C[double bond, length as m-dash]O) of methyl aryl-ketones and the reaction rate catalyzed by HvADH2. The enzyme catalyzed the reductions of ketone substrates on the preparative scale, demonstrating that HvADH2 would be a valuable biocatalyst for the preparation of chiral aromatic alcohols of pharmaceutical interest.

  17. Organic Chemistry Students' Ideas about Nucleophiles and Electrophiles: The Role of Charges and Mechanisms

    Science.gov (United States)

    Anzovino, Mary E.; Bretz, Stacey Lowery

    2015-01-01

    Organic chemistry students struggle with reaction mechanisms and the electron-pushing formalism (EPF) used by practicing organic chemists. Faculty have identified an understanding of nucleophiles and electrophiles as one conceptual prerequisite to mastery of the EPF, but little is known about organic chemistry students' knowledge of nucleophiles…

  18. Peroxide Activation for Electrophilic Reactivity by the Binuclear Non-heme Iron Enzyme AurF

    International Nuclear Information System (INIS)

    Park, Kiyoung; Li, Ning; Kwak, Yeonju; Srnec, Martin

    2017-01-01

    Binuclear non-heme iron enzymes activate O 2 for diverse chemistries that include oxygenation of organic substrates and hydrogen atom abstraction. This process often involves the formation of peroxo-bridged biferric intermediates, only some of which can perform electrophilic reactions. To elucidate the geometric and electronic structural requirements to activate peroxo reactivity, the active peroxo intermediate in 4-aminobenzoate N-oxygenase (AurF) has been characterized spectroscopically and computationally. A magnetic circular dichroism study of reduced AurF shows that its electronic and geometric structures are poised to react rapidly with O 2 . Nuclear resonance vibrational spectroscopic definition of the peroxo intermediate formed in this reaction shows that the active intermediate has a protonated peroxo bridge. Density functional theory computations on the structure established here show that the protonation activates peroxide for electrophilic/single-electron-transfer reactivity. As a result, this activation of peroxide by protonation is likely also relevant to the reactive peroxo intermediates in other binuclear non-heme iron enzymes.

  19. Asymmetric Reduction of Substituted 2-Tetralones by Thermoanaerobacter pseudoethanolicus Secondary Alcohol Dehydrogenase

    KAUST Repository

    Bsharat, Odey; Musa, Musa M.; Vieille, Claire; Oladepo, Sulayman; Takahashi, Masateru; Hamdan, Samir

    2017-01-01

    Ketones bearing two bulky substituents, named bulky-bulky ketones, were successfully reduced to their corresponding optically enriched alcohols by using various mutants of Thermoanaerobacter pseudoethanolicus secondary alcohol dehydrogenase (TeSADH). Substituted 2-tetralones, in particular, were reduced to 2-tetralols with high conversion and high enantioselectivity. The pharmacological importance of substituted 2-tetralols as key drug-building blocks makes our biocatalytic reduction method a highly essential tool. We showed that changing the position of the substituent on the aromatic ring of 2-tetralones impacts their binding affinity and the reaction maximum catalytic rate. Docking studies with several TeSADH mutants explain how the position of the substituent on the tetralone influences the binding orientation of substituted 2-tetralones and their reaction stereoselectivity.

  20. Asymmetric Reduction of Substituted 2-Tetralones by Thermoanaerobacter pseudoethanolicus Secondary Alcohol Dehydrogenase

    KAUST Repository

    Bsharat, Odey

    2017-01-30

    Ketones bearing two bulky substituents, named bulky-bulky ketones, were successfully reduced to their corresponding optically enriched alcohols by using various mutants of Thermoanaerobacter pseudoethanolicus secondary alcohol dehydrogenase (TeSADH). Substituted 2-tetralones, in particular, were reduced to 2-tetralols with high conversion and high enantioselectivity. The pharmacological importance of substituted 2-tetralols as key drug-building blocks makes our biocatalytic reduction method a highly essential tool. We showed that changing the position of the substituent on the aromatic ring of 2-tetralones impacts their binding affinity and the reaction maximum catalytic rate. Docking studies with several TeSADH mutants explain how the position of the substituent on the tetralone influences the binding orientation of substituted 2-tetralones and their reaction stereoselectivity.

  1. Unprecedented Spectroscopic and Computational Evidence for Allenyl and Propargyl Titanocene(IV) Complexes: Electrophilic Quenching of Their Metallotropic Equilibrium.

    Science.gov (United States)

    Ruiz-Muelle, Ana Belén; Oña-Burgos, Pascual; Ortuño, Manuel A; Oltra, J Enrique; Rodríguez-García, Ignacio; Fernández, Ignacio

    2016-02-12

    The synthesis and structural characterization of allenyl titanocene(IV) [TiClCp2 (CH=C=CH2 )] 3 and propargyl titanocene(IV) [TiClCp2 (CH2 -C≡C-(CH2 )4 CH3 )] 9 have been described for the first time. Advanced NMR methods including diffusion NMR methods (diffusion pulsed field gradient stimulated spin echo (PFG-STE) and DOSY) have been applied and established that these organometallics are monomers in THF solution with hydrodynamic radii (from the Stokes-Einstein equation) of 3.5 and 4.1 Å for 3 and 9, respectively. Full (1) H, (13) C, Δ(1) H, and Δ(13) C NMR data are given, and through the analysis of the Ramsey equation, the first electronic insights into these derivatives are provided. In solution, they are involved in their respective metallotropic allenyl-propargyl equilibria that, after quenching experiments with aromatic and aliphatic aldehydes, ketones, and protonating agents, always give the propargyl products P (when carbonyls are employed), or allenyl products A (when a proton source is added) as the major isomers. In all the cases assayed, the ratio of products suggests that the metallotropic equilibrium should be faster than the reactions of 3 and 9 with electrophiles. Indeed, DFT calculations predict lower Gibbs energy barriers for the metallotropic equilibrium, thus confirming dynamic kinetic resolution. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Oxidative nucleophilic substitution of hydrogen in nitro(pentafluorosulfanyl)benzenes with alkyl Grignard and lithium reagents

    Czech Academy of Sciences Publication Activity Database

    Vida, Norbert; Beier, Petr

    2012-01-01

    Roč. 143, SI (2012), s. 130-134 ISSN 0022-1139 R&D Projects: GA ČR GAP207/12/0072 Institutional support: RVO:61388963 Keywords : pentafluorosulfanyl group * nucleophilic aromatic substitutions * oxidations Subject RIV: CC - Organic Chemistry Impact factor: 1.939, year: 2012

  3. Effects of methyl group on aromatic hydrocarbons on the nanostructures and oxidative reactivity of combustion-generated soot

    KAUST Repository

    Guerrero Peñ a, Gerardo D.J.; Alrefaai, Mhd Maher; Yang, Seung Yeon; Raj, Abhijeet; Brito, Joaquin L.; Stephen, Samuel; Anjana, Tharalekshmy; Pillai, Vinu; Al Shoaibi, Ahmed; Chung, Suk-Ho

    2016-01-01

    The substituted and unsubstituted aromatic hydrocarbons, present in transportation fuels such as gasoline and diesel, are thought to be responsible for most of the soot particles produced during their combustion. However, the effects of the substituted alkyl groups on the aromatic hydrocarbons on their sooting tendencies, and on the physical and chemical properties of soot produced from them are not well understood. In this work, the effect of the presence of methyl groups on aromatic hydrocarbons on their sooting propensity, and on the oxidative reactivity, morphology, and chemical composition of soot generated from them in diffusion flames is studied using benzene, toluene, and m-xylene as fuels. Several experimental techniques including high resolution transmission electron microscopy and X-ray diffraction are used to identify the morphological changes in soot, whereas the elemental and thermo-gravimetric analyses, electron energy loss spectroscopy, and Fourier transform infrared spectroscopy are used to study the changes in its chemical properties and reactivity. The activation energies for soot oxidation are calculated at different conversion levels, and a trend in the reactivity of soots from benzene, toluene and m-xylene is reported. It is observed that the sizes of primary particles and graphene-like sheets, and the concentrations of aliphatics and oxygenated groups in soot particles decreased with the addition of methyl group(s) on the aromatic ring. The physicochemical changes in soot are found to support the oxidative reactivity trends. © 2016 The Combustion Institute

  4. Effects of methyl group on aromatic hydrocarbons on the nanostructures and oxidative reactivity of combustion-generated soot

    KAUST Repository

    Guerrero Peña, Gerardo D.J.

    2016-07-23

    The substituted and unsubstituted aromatic hydrocarbons, present in transportation fuels such as gasoline and diesel, are thought to be responsible for most of the soot particles produced during their combustion. However, the effects of the substituted alkyl groups on the aromatic hydrocarbons on their sooting tendencies, and on the physical and chemical properties of soot produced from them are not well understood. In this work, the effect of the presence of methyl groups on aromatic hydrocarbons on their sooting propensity, and on the oxidative reactivity, morphology, and chemical composition of soot generated from them in diffusion flames is studied using benzene, toluene, and m-xylene as fuels. Several experimental techniques including high resolution transmission electron microscopy and X-ray diffraction are used to identify the morphological changes in soot, whereas the elemental and thermo-gravimetric analyses, electron energy loss spectroscopy, and Fourier transform infrared spectroscopy are used to study the changes in its chemical properties and reactivity. The activation energies for soot oxidation are calculated at different conversion levels, and a trend in the reactivity of soots from benzene, toluene and m-xylene is reported. It is observed that the sizes of primary particles and graphene-like sheets, and the concentrations of aliphatics and oxygenated groups in soot particles decreased with the addition of methyl group(s) on the aromatic ring. The physicochemical changes in soot are found to support the oxidative reactivity trends. © 2016 The Combustion Institute

  5. Structural and functional characterization of solute binding proteins for aromatic compounds derived from lignin: p-coumaric acid and related aromatic acids.

    Science.gov (United States)

    Tan, Kemin; Chang, Changsoo; Cuff, Marianne; Osipiuk, Jerzy; Landorf, Elizabeth; Mack, Jamey C; Zerbs, Sarah; Joachimiak, Andrzej; Collart, Frank R

    2013-10-01

    Lignin comprises 15-25% of plant biomass and represents a major environmental carbon source for utilization by soil microorganisms. Access to this energy resource requires the action of fungal and bacterial enzymes to break down the lignin polymer into a complex assortment of aromatic compounds that can be transported into the cells. To improve our understanding of the utilization of lignin by microorganisms, we characterized the molecular properties of solute binding proteins of ATP-binding cassette transporter proteins that interact with these compounds. A combination of functional screens and structural studies characterized the binding specificity of the solute binding proteins for aromatic compounds derived from lignin such as p-coumarate, 3-phenylpropionic acid and compounds with more complex ring substitutions. A ligand screen based on thermal stabilization identified several binding protein clusters that exhibit preferences based on the size or number of aromatic ring substituents. Multiple X-ray crystal structures of protein-ligand complexes for these clusters identified the molecular basis of the binding specificity for the lignin-derived aromatic compounds. The screens and structural data provide new functional assignments for these solute-binding proteins which can be used to infer their transport specificity. This knowledge of the functional roles and molecular binding specificity of these proteins will support the identification of the specific enzymes and regulatory proteins of peripheral pathways that funnel these compounds to central metabolic pathways and will improve the predictive power of sequence-based functional annotation methods for this family of proteins. Copyright © 2013 Wiley Periodicals, Inc.

  6. Facile and Selective Synthesis of 2-Substituted Benzimidazoles Catalyzed by FeCl3/ Al2O3

    Directory of Open Access Journals (Sweden)

    Guo-Feng Chen

    2012-01-01

    Full Text Available 2-Substituted benzimidazoles were synthesized in a single pot from aromatic aldehydes and o-phenylenediamine catalyzed by FeCl3/ Al2O3 in DMF at ambient temperature attained good yields and high selectivity.

  7. Rearrangement of the distal pocket accompanying E7 His → Gln substitution in elephant carbonmonoxy- and oxymyoglobin: 1H NMR identification of a new aromatic residue in the heme pocket

    International Nuclear Information System (INIS)

    Yu, L.P.; La Mar, G.N.; Mizukami, H.

    1990-01-01

    Two-dimensional 1 H NMR methods have been used to assign side-chain resonances for the residues in the distal heme pocket of elephant carbonmonoxymyoglobin (MbCO) and oxymyoglobin (MbO 2 ). It is shown that, while the other residues in the heme pocket are minimally perturbed, the Phe CD4 residue in elephant MbCO and MbO 2 resonates considerably upfield compared to the corresponding residue in sperm whale MbCO. The new NOE connectivities to Val E11 and heme-induced ring current calculations indicate that Phe CD4 has been inserted into the distal heme pocket by reorienting the aromatic side chain and moving the CD corner closer to the heme. The CζH proton of the Phe CD4 was found to move toward the iron of the heme by ∼4 angstrom relative to the position in sperm whale MbCO, requiring minimally a 3-angstrom movement of the CD helical backbone. The significantly altered distal conformation in elephant myoglobin, rather than the single distal E7 substitution, forms a plausible basis for its altered functional properties of lower autoxidation rate, higher redox potential, and increased affinity for CO ligand. These results demonstrate that one-to-one interpretation of amino acid residue substitution (E7 His → Gln) is oversimplified and that conformational changes of substituted proteins which are not readily predicted have to be considered for interpretation of their functional properties

  8. A Computational Study of Structure and Reactivity of N-Substitued-4-Piperidones Curcumin Analogues and Their Radical Anions

    Directory of Open Access Journals (Sweden)

    Maximiliano Martínez-Cifuentes

    2016-12-01

    Full Text Available In this work, a computational study of a series of N-substitued-4-piperidones curcumin analogues is presented. The molecular structure of the neutral molecules and their radical anions, as well as their reactivity, are investigated. N-substituents include methyl and benzyl groups, while substituents on the aromatic rings cover electron-donor and electron-acceptor groups. Substitutions at the nitrogen atom do not significantly affect the geometry and frontier molecular orbitals (FMO energies of these molecules. On the other hand, substituents on the aromatic rings modify the distribution of FMO. In addition, they influence the capability of these molecules to attach an additional electron, which was studied through adiabatic (AEA and vertical electron affinities (VEA, as well as vertical detachment energy (VDE. To study electrophilic properties of these structures, local reactivity indices, such as Fukui (f+ and Parr (P+ functions, were calculated, and show the influence of the aromatic rings substituents on the reactivity of α,β-unsaturated ketones towards nucleophilic attack. This study has potential implications for the design of curcumin analogues based on a 4-piperidone core with desired reactivity.

  9. Covalent Allosteric Inactivation of Protein Tyrosine Phosphatase 1B (PTP1B) by an Inhibitor-Electrophile Conjugate.

    Science.gov (United States)

    Punthasee, Puminan; Laciak, Adrian R; Cummings, Andrea H; Ruddraraju, Kasi Viswanatharaju; Lewis, Sarah M; Hillebrand, Roman; Singh, Harkewal; Tanner, John J; Gates, Kent S

    2017-04-11

    Protein tyrosine phosphatase 1B (PTP1B) is a validated drug target, but it has proven difficult to develop medicinally useful, reversible inhibitors of this enzyme. Here we explored covalent strategies for the inactivation of PTP1B using a conjugate composed of an active site-directed 5-aryl-1,2,5-thiadiazolidin-3-one 1,1-dioxide inhibitor connected via a short linker to an electrophilic α-bromoacetamide moiety. Inhibitor-electrophile conjugate 5a caused time-dependent loss of PTP1B activity consistent with a covalent inactivation mechanism. The inactivation occurred with a second-order rate constant of (1.7 ± 0.3) × 10 2 M -1 min -1 . Mass spectrometric analysis of the inactivated enzyme indicated that the primary site of modification was C121, a residue distant from the active site. Previous work provided evidence that covalent modification of the allosteric residue C121 can cause inactivation of PTP1B [Hansen, S. K., Cancilla, M. T., Shiau, T. P., Kung, J., Chen, T., and Erlanson, D. A. (2005) Biochemistry 44, 7704-7712]. Overall, our results are consistent with an unusual enzyme inactivation process in which noncovalent binding of the inhibitor-electrophile conjugate to the active site of PTP1B protects the nucleophilic catalytic C215 residue from covalent modification, thus allowing inactivation of the enzyme via selective modification of allosteric residue C121.

  10. Nrf2 the rescue: Effects of the antioxidative/electrophilic response on the liver

    International Nuclear Information System (INIS)

    Klaassen, Curtis D.; Reisman, Scott A.

    2010-01-01

    Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor that positively regulates the basal and inducible expression of a large battery of cytoprotective genes. These gene products include proteins that catalyze reduction reactions (NAD(P)H:quinone oxidoreductase 1, Nqo1), conjugation reactions (glutathione-S-transferases, Gsts and UDP-glucuronosyltransferases, Ugts), as well as the efflux of potentially toxic xenobiotics and xenobiotic conjugates (multidrug resistance-associated proteins, Mrps). The significance of Nrf2 in the liver has been established, as livers of Nrf2-null mice are more susceptible to various oxidative/electrophilic stress-induced pathologies than wild-type mice. In contrast, both pharmacological and genetic models of hepatic Nrf2 activation are protective against oxidative/electrophilic stress. Furthermore, because certain Nrf2-target genes in the liver could affect the distribution, metabolism, and excretion of xenobiotics, the effects of Nrf2 on the kinetics of drugs and other xenobiotics should also be considered, with a special emphasis on metabolism and excretion. Therefore, this review highlights the research that has contributed to the understanding of the importance of Nrf2 in toxicodynamics and toxicokinetics, especially that which pertains to the liver.

  11. One-pot regioselective synthesis of nitrophenyloxazolinyl styrene oxides by the Darzens reaction of vicarious nucleophilic substitution-formed carbanions of 2-dichloromethyl-4,4-dimethyloxazoline.

    Science.gov (United States)

    Florio, Saverio; Lorusso, Patrizia; Granito, Catia; Luisi, Renzo; Troisi, Luigino

    2004-07-23

    The vicarious nucleophilic substitution reaction of dichloromethyloxazoline 2 with nitrobenzene has been investigated. Treatment of 2 with t-BuOK followed by the addition of nitrobenzene leads to benzylic carbanions 4 or 9 depending upon the solvent used (DMSO, DMF, or THF). Subsequent treatment of 4 or 9 with aldehydes, in a Darzens-like reaction, furnishes very good yields of nitrophenyl oxazolinyloxiranes 8 and 11. 1,2-Dioxazolinyl-1,2-dinitrophenylethene 7 forms quantitatively when carbanion 4 is allowed to warm to room temperature in the absence of external electrophiles.

  12. Kinetics of exchange reaction between neodymium(3) transcyclohexanediaminetetraacetate and europium(3)- and holmium(3) aquo-ions in the H2O and D2O solutions

    International Nuclear Information System (INIS)

    Nikitenko, S.I.; Martynenko, L.I.; Pechurova, N.I.; Spitsyn, V.I.

    1983-01-01

    The exchange reaction between central ions in the NdD - Ln' 3+ systems, where Ln' 3+ is a substituting cation (Eu 3+ and Ho 3+ , D 4 =cyclohexanediaminetetraacetate) is studied and the electrophilic suhstitution mechanism is considered. To study the kinetic isotope effects, the reagents have been solVed in heavy water containing 99.9% D 2 O. The electrophilic substitution in the indicated systems proceeds through the dissociative mechanism catalyzed by protons and via the spontaneous dissociation mechanism. The exchange via the acid-catalyzed mechanism is limited by the intermediate protonated complex decay. The associative mechanism of the electrophilic exchange in the studied systems is not realized

  13. Five-membered heterocycles. Part II. Crystal structures and HOMA index calculations for selected 1,3,4-thiadiazole derivatives

    Science.gov (United States)

    Mrozek, A.; Karolak-Wojciechowska, J.; Amiel, P.; Barbe, J.

    2000-06-01

    Crystal structures of four bisubstituted 1,3,4-thiadiazole derivatives were determined. Detailed description of the five-membered heteroring geometry is enabled thorough analysis of ring aromaticity. For this purpose the HOMA index was used as a quantitative measure of aromaticity. The calculated HOMA indices evidenced the role of substituents. In particular, increase in the substituent electrophilicity brings about increase in aromaticity.

  14. Self-Consistent Study of Conjugated Aromatic Molecular Transistors

    International Nuclear Information System (INIS)

    Jing, Wang; Yun-Ye, Liang; Hao, Chen; Peng, Wang; Note, R.; Mizuseki, H.; Kawazoe, Y.

    2010-01-01

    We study the current through conjugated aromatic molecular transistors modulated by a transverse field. The self-consistent calculation is realized with density function theory through the standard quantum chemistry software Gaussian03 and the non-equilibrium Green's function formalism. The calculated I – V curves controlled by the transverse field present the characteristics of different organic molecular transistors, the transverse field effect of which is improved by the substitutions of nitrogen atoms or fluorine atoms. On the other hand, the asymmetry of molecular configurations to the axis connecting two sulfur atoms is in favor of realizing the transverse field modulation. Suitably designed conjugated aromatic molecular transistors possess different I – V characteristics, some of them are similar to those of metal-oxide-semiconductor field-effect transistors (MOSFET). Some of the calculated molecular devices may work as elements in graphene electronics. Our results present the richness and flexibility of molecular transistors, which describe the colorful prospect of next generation devices. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  15. Preparation of magnetic latexes functionalized with chloromethyl groups via emulsifier-free miniemulsion polymerization

    International Nuclear Information System (INIS)

    Faridi-Majidi, Reza; Sharifi-Sanjani, Naser

    2007-01-01

    Functionalized crosslinked polystyrene-co-divinylbenzene-co-chloromethylstyrene magnetic latex particles were prepared via emulsifier-free miniemulsion polymerization using 2, 2' azobis (2-amidinopropane) dihydrochloride (V-50) as an initiator and in the presence of magnetite nanoparticles in the monomers. Transmission electron microscopy (TEM) proved the presence of magnetite nanoparticles in polymer particles. Differential scanning calorimetery (DSC) analysis of the product showed an exothermic signal due to crosslinking of chains through electrophilic aromatic substitution of phenyl groups with chloromethyl groups in the presence of the dispersed Fe 3 O 4 as Lewis acid. This was proven by thermogravimetric analysis (TGA) via the loss of gaseous HCl. The results were also compared with those of magnetite-free miniemulsion polymerization using V-50

  16. Preparation of magnetic latexes functionalized with chloromethyl groups via emulsifier-free miniemulsion polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Faridi-Majidi, Reza [School of Chemistry, University College of Science, Tehran University, Tehran (Iran, Islamic Republic of)]. E-mail: refaridi@khayam.ut.ac.ir; Sharifi-Sanjani, Naser [School of Chemistry, University College of Science, Tehran University, Tehran (Iran, Islamic Republic of)

    2007-04-15

    Functionalized crosslinked polystyrene-co-divinylbenzene-co-chloromethylstyrene magnetic latex particles were prepared via emulsifier-free miniemulsion polymerization using 2, 2' azobis (2-amidinopropane) dihydrochloride (V-50) as an initiator and in the presence of magnetite nanoparticles in the monomers. Transmission electron microscopy (TEM) proved the presence of magnetite nanoparticles in polymer particles. Differential scanning calorimetery (DSC) analysis of the product showed an exothermic signal due to crosslinking of chains through electrophilic aromatic substitution of phenyl groups with chloromethyl groups in the presence of the dispersed Fe{sub 3}O{sub 4} as Lewis acid. This was proven by thermogravimetric analysis (TGA) via the loss of gaseous HCl. The results were also compared with those of magnetite-free miniemulsion polymerization using V-50.

  17. Improving the Stability of Organic Semiconductors: Distortion Energy versus Aromaticity in Substituted Bistetracene

    KAUST Repository

    Thomas, Simil

    2016-11-15

    Polycyclic aromatic hydrocarbons (PAHs) have been widely explored as molecular semiconductors in organic electronic devices such as field-effect transistors or solar cells. However, their tendency to undergo photooxidation is a primary limitation to their practical applications. Bistetracene derivatives have recently been demonstrated to possess much larger photo oxidation stability than the widely investigated pentacene and rubrene, while maintaining high charge-carrier mobilities. Here, using several levels of density functional theory, we identify the origin of the increased stability of bistetracene with respect to molecular oxygen by systematically investigating the [4 + 2] cycloaddition (Diels Alder) photooxidation reaction mechanism. Importantly, our computational results indicate that endoperoxide formation in bis(2-(trimethylsilyl)ethynyl) bistetracene (BT) occurs not on the ring with least aromaticity, but rather on the ring with smallest distortion energy. This feature was subsequently confirmed by experimental NMR analyses. The oxidation activation barriers of bistetracene, pentacene, and rubrene are found to be 17.7, 13.6, and 14.4 kcal/mol, respectively, in agreement with the observed order of stability of these molecules with respect to oxidation reactions in solution. In the cases of BT and pentacene, the rates of electron transfer to create charged species (PAH(+) and O-2) are at least two orders of magnitude lower than that of the charge recombination process (back to PAH and O-2); for rubrene, both of these processes are calculated to be of the same order of magnitude, in agreement with experimental electron paramagnetic resonance spectroscopy observations.

  18. Effect of B-ring substitution pattern on binding mode of propionamide selective androgen receptor modulators.

    Science.gov (United States)

    Bohl, Casey E; Wu, Zengru; Chen, Jiyun; Mohler, Michael L; Yang, Jun; Hwang, Dong Jin; Mustafa, Suni; Miller, Duane D; Bell, Charles E; Dalton, James T

    2008-10-15

    Selective androgen receptor modulators (SARMs) are essentially prostate sparing androgens, which provide therapeutic potential in osteoporosis, male hormone replacement, and muscle wasting. Herein we report crystal structures of the androgen receptor (AR) ligand-binding domain (LBD) complexed to a series of potent synthetic nonsteroidal SARMs with a substituted pendant arene referred to as the B-ring. We found that hydrophilic B-ring para-substituted analogs exhibit an additional region of hydrogen bonding not seen with steroidal compounds and that multiple halogen substitutions affect the B-ring conformation and aromatic interactions with Trp741. This information elucidates interactions important for high AR binding affinity and provides new insight for structure-based drug design.

  19. Self-assembled electrical materials from contorted aromatics

    Science.gov (United States)

    Xiao, Shengxiong

    This thesis describes the design, synthesis, self-assembly and electrical properties of new types of contorted polycyclic aromatic hydrocarbons. These topologically interesting contorted aromatics show promising transistor characteristics as new building blocks for organic field-effect transistors (OFETs) at different length scales. In chapter 2, a class of pentacenes that are substituted along their long edges with aromatic rings were synthesized. Their solid-state assemblies were studied by X-ray crystallography. Their performance as thin film transistors (TFTs) and single crystal field effect transistors (SCFETs) were systematically evaluated. A structure-property relationship between these highly phenylated pentacenes was found. Chapter 3 explores the new concept of whether a non-planar aromatic core could yield efficacious electronic materials, as the ultimate success in the organic electronics will require a holistic approach to creating new building blocks. Synthesis, functionalization and assembly of a new type of contorted hexabenzocoronene (HBC) whose aromatic core is heavily distorted away from planarity due to the steric congestion around its proximal carbons were discussed. Structural studies by X-ray crystallography showed that these HBC molecules stack into columnar structures in the solid state, which are ideal for conduction. Chapter 4 describes that microscale liquid crystalline thin film OFETs of tetradodecyloxy HBC showed the best transistor properties of all discotic columnar materials. Chapter 5 details the fabrication and characterization of nanoscale single crystalline fiber OFETs of octadodecyloxyl HBC. In Chapter 6 we show that a molecular scale monolayer of HBC acid chlorides could be self-assembled on SiO2 insulating layer and could be organized laterally between the ends of 2 nm carbon nanotube gaps to form high quality FETs that act as environmental and chemical sensors. Chapter 7 details the enforced one-dimensional photoconductivity

  20. Tandem electrophilic cyclization-[3+2] cycloaddition-rearrangement reactions of 2-alkynylbenzaldoxime, DMAD, and Br2.

    Science.gov (United States)

    Ding, Qiuping; Wang, Zhiyong; Wu, Jie

    2009-01-16

    Tandem electrophilic cyclization-[3+2] cycloaddition-rearrangement reactions of 2-alkynylbenzaldoximes, DMAD, and bromine are described, which afford the unexpected isoquinoline-based azomethine ylides in good to excellent yields. The products could be further elaborated via palladium-catalyzed cross-coupling reactions to generate highly functionalized isoquinoline-based stable azomethine ylides.

  1. Combinations of Aromatic and Aliphatic Radiolysis.

    Science.gov (United States)

    LaVerne, Jay A; Dowling-Medley, Jennifer

    2015-10-08

    The production of H(2) in the radiolysis of benzene, methylbenzene (toluene), ethylbenzene, butylbenzene, and hexylbenzene with γ-rays, 2-10 MeV protons, 5-20 MeV helium ions, and 10-30 MeV carbon ions is used as a probe of the overall radiation sensitivity and to determine the relative contributions of aromatic and aliphatic entities in mixed hydrocarbons. The addition of an aliphatic side chain with progressively from one to six carbon lengths to benzene increases the H(2) yield with γ-rays, but the yield seems to reach a plateau far below that found from a simple aliphatic such as cyclohexane. There is a large increase in H(2) with LET (linear energy transfer) for all of the substituted benzenes, which indicates that the main process for H(2) formation is a second-order process and dominated by the aromatic entity. The addition of a small amount of benzene to cyclohexane can lower the H(2) yield from the value expected from a simple mixture law. A 50:50% volume mixture of benzene-cyclohexane has essentially the same H(2) yield as cyclohexylbenzene at a wide variation in LET, suggesting that intermolecular energy transfer is as efficient as intramolecular energy transfer.

  2. Photochemically induced oscillations of aromatic pentazadienes

    Energy Technology Data Exchange (ETDEWEB)

    Kunz, T; Hahn, C; Wokaun, A [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-06-01

    Aromatic pentazadienes are used to enhance the laser induced ablation of standard polymers with low absorption in the UV. Therefore the photochemistry of substituted 1,5-diaryl-3-alkyl-1,4-pentazadiene monomers was studied with a pulsed excimer laser as irradiation source. The net photochemical reaction proceeds in an overall one-step pathway A{yields}B. Quantum yields for the laser decomposition were determined to be up to 10%. An oscillating behaviour of the absorption was found during the dark period following the irradiation. The temperature dependence of this dark reaction has been studied. An attempt to model this behaviour in terms of a non-linear coupling between heat released, heat transfer, and reaction kinetics will be described. (author) 4 figs., 4 refs.

  3. A tandem Mannich addition–palladium catalyzed ring-closing route toward 4-substituted-3(2H-furanones

    Directory of Open Access Journals (Sweden)

    Jubi John

    2014-06-01

    Full Text Available A facile route towards highly functionalized 3(2H-furanones via a sequential Mannich addition–palladium catalyzed ring closing has been elaborated. The reaction of 4-chloroacetoacetate esters with imines derived from aliphatic and aromatic aldehydes under palladium catalysis afforded 4-substituted furanones in good to excellent yields. 4-Hydrazino-3(2H-furanones could also be synthesized from diazo esters in excellent yields by utilising the developed strategy. We could also efficiently transform the substituted furanones to aza-prostaglandin analogues.

  4. Formation of electrophilic oxidation products from mitochondrial cardiolipin in vitro and in vivo in the context of apoptosis and atherosclerosis

    Directory of Open Access Journals (Sweden)

    Huiqin Zhong

    2014-01-01

    Full Text Available Emerging evidence indicates that mitochondrial cardiolipins (CL are prone to free radical oxidation and this process appears to be intimately associated with multiple biological functions of mitochondria. Our previous work demonstrated that a significant amount of potent lipid electrophiles including 4-hydroxy-nonenal (4-HNE was generated from CL oxidation through a novel chemical mechanism. Here we provide further evidence that a characteristic class of CL oxidation products, epoxyalcohol-aldehyde-CL (EAA-CL, is formed through this novel mechanism in isolated mice liver mitochondria when treated with the pro-apoptotic protein t-Bid to induce cyt c release. Generation of these oxidation products are dose-dependently attenuated by a peroxidase inhibitor acetaminophen (ApAP. Using a mouse model of atherosclerosis, we detected significant amount of these CL oxidation products in liver tissue of low density lipoprotein receptor knockout (LDLR −/− mice after Western diet feeding. Our studies highlight the importance of lipid electrophiles formation from CL oxidation in the settings of apoptosis and atherosclerosis as inhibition of CL oxidation and lipid electrophiles formation may have potential therapeutic value in diseases linked to oxidant stress and mitochondrial dysfunctions.

  5. Aromatic hydrocarbons

    International Nuclear Information System (INIS)

    Roder, M.

    1985-01-01

    Papers dealing with radiolysis of aromatic hydrocarbons of different composition (from benzene to terphenyls and hydrocarbons with condensed rings) as well as their mixtures (with alkanes, alkenes, other aromatic hydrocarbons) are reviewed. High radiation stability of aromatic hydrocarbons in condensed phases associated with peculiarities of molecular structure of compounds is underlined. Mechanisms of radiolytic processes, vaues of product yields are considered

  6. Assessment of the radiation resistance of some aromatic polyesters

    International Nuclear Information System (INIS)

    Choi, E.J.; Hill, D.J.T.; Kim, K.Y.

    1998-01-01

    Full text: For many applications, polyesters have more useful properties than vinyl polymers, and they can be degraded to their monomer components and recycled. In addition, aromatic polyesters are known to display a resistance to high temperatures and high-energy ionizing radiation. Recently, we have reported the γ-radiolysis for some aromatic polyesters at low radiation dose; The G-values of radical formation at 77 K were determined to be in the range 0.38∼0.46 for the polyesters of bisphenol A with fluorine substitution at isopropylidene units and in the range 0.71∼1.18 for the polyesters of halogenated bisphenol A with decamethylene segments. While the radiation sensitivities of the latter polymers were dependent on the position and content of halogen substitution, those of the former polymers were slightly dependent on these factors as assessed by the G-values at 77 K. We also have studied the radiolysis of the commercial aromatic polyesters (UP) and polycarbonate (PC). UP has been found to be more radiation stable than PC with respect to the total yield of radicals formed. The G-values for radical formation at 77K was determined to be 0.31 and 0.5 for UP and PC, respectively. In this work, we have prepared poly(ethylene-, butylene- or decalene-terephthalate)s (PET, PBT or PDT) and poly(ethylene-, buthylene- or decalene-2,6-naphthalenedicarboxylate)s (PEN, PBN or PDN) by standard melt polymerization methods, and have examined their γ-radiolysis at 77 K or room temperature, and in vacuum or air, through the applications of ESR spectroscopy and thermal analysis. Inherent viscosities of the polyesters used for the radiation studies were in the range of 0.16∼0.69 dL/g. The values of G(R) indicates that PEN-related polymers have more radiation stable than PET-related polymers and the E, B and D order is one of decreasing stability as one might expect. The significant decrease in the G(R)-values of the polyester being in the range of 0.1∼0.41 at 77 K by

  7. New Horizons in C-F Activation by Main Group Electrophiles

    Energy Technology Data Exchange (ETDEWEB)

    Ozerov, Oleg V. [Texas A & M Univ., College Station, TX (United States). Dept. of Chemistry

    2016-02-13

    This technical report describes progress on the DOE sponsored project "New Horizons in C-F Activation by Main Group Electrophiles" during the period of 09/15/2010 – 08/31/2015. The main goal of this project was to develop improved catalysts for conversion of carbon-fluorine bonds in potentially harmful compounds. The approach involved combining of a highly reactive positively charged main-group compound with a highly unreactive negatively charged species (anions) as a way to access potent catalysts for carbon-fluorine bond activation. This report details progress made in improving synthetic pathways to a variety of new anions with improved properties and analysis of their potential in catalysis.

  8. Rac1 modification by an electrophilic 15-deoxy Δ12,14-prostaglandin J2 analog

    Directory of Open Access Journals (Sweden)

    S.B. Wall

    2015-04-01

    Full Text Available Vascular endothelial cells (ECs are important for maintaining vascular homeostasis. Dysfunction of ECs contributes to cardiovascular diseases, including atherosclerosis, and can impair the healing process during vascular injury. An important mediator of EC response to stress is the GTPase Rac1. Rac1 responds to extracellular signals and is involved in cytoskeletal rearrangement, reactive oxygen species generation and cell cycle progression. Rac1 interacts with effector proteins to elicit EC spreading and formation of cell-to-cell junctions. Rac1 activity has recently been shown to be modulated by glutathiolation or S-nitrosation via an active site cysteine residue. However, it is not known whether other redox signaling compounds can modulate Rac1 activity. An important redox signaling mediator is the electrophilic lipid, 15-deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2. This compound is a downstream product of cyclooxygenase and forms covalent adducts with specific cysteine residues, and induces cellular signaling in a pleiotropic manner. In this study, we demonstrate that a biotin-tagged analog of 15d-PGJ2 (bt-15d-PGJ2 forms an adduct with Rac1 in vitro at the C157 residue, and an additional adduct was detected on the tryptic peptide associated with C178. Rac1 modification in addition to modulation of Rac1 activity by bt-15d-PGJ2 was observed in cultured ECs. In addition, decreased EC migration and cell spreading were observed in response to the electrophile. These results demonstrate for the first time that Rac1 is a target for 15d-PGJ2 in ECs, and suggest that Rac1 modification by electrophiles such as 15d-PGJ2 may alter redox signaling and EC function.

  9. The Synthesis of Novel 3-Substituted Poly(pyrroles) Bearing Crown-ether Moieties and a Study of their Electrochemical Properties

    DEFF Research Database (Denmark)

    Guernion, Nicolas J.L.; Blencowe, A.; Hayes, Wayne

    2006-01-01

    A series of fourteen novel pyrrole monomers substituted at the 3-position with aliphatic and aromatic crown-ether moieties have been synthesised in good yield and characterised extensively. Several of those compounds were electropolymerised successfully in acetonitrile, using both potentiostatic ...

  10. Cu(OAc)2/TFA-promoted formal [3 + 3] cycloaddition/oxidation of enamines and enones for synthesis of multisubstituted aromatic amines.

    Science.gov (United States)

    Li, Liang; Zhao, Mi-Na; Ren, Zhi-Hui; Li, Jian-Li; Guan, Zheng-Hui

    2012-07-06

    New strategies for the oxidative cycloaddition of enones with enamines are developed. These cycloaddition reactions directly afford substituted aromatic amines, which are important in organic chemistry, in moderate to good yield. Cu(OAc)(2)/TFA is shown to be essential to achieve high reaction efficiency.

  11. Liquid-liquid extraction and separation of VIII group elements, especially ruthenium, by synergic combinations or aromatic polyimines and micellar cationic exchangers

    International Nuclear Information System (INIS)

    Vitart, X.

    1991-01-01

    This thesis aims to characterize and to quantify the chemical equilibria involved in d-elements liquid-liquid extraction systems, especially elements belonging to the VIII group (Fe, Ni, Co, Ru, Rh, Pd, Pt). These systems are composed of synergic combination of aromatic polyimines and micellar cationic exchangers. Substitutions are first performed in aqueous acidic media by aromatic polyimines; then extractions are operated using micellic canionic exchangers. Chemical equilibria, selectivity effects, especially those due to ion-pair formations, kinetics, extractant behaviour are analysed and quantified [fr

  12. Synthesis of aryl-substituted 5-[18F]fluoroalkylbenzamides: High affinity ligands for dopamine D-2 studies

    International Nuclear Information System (INIS)

    Mathis, C.A.; Bishop, J.E.; Gerdes, J.M.; Faggin, B.; Mailman, R.

    1990-01-01

    Recent studies of the structure-activity relationship of benzamides have shown that the 2,3-dimethoxy substitution pattern of (S)-N-[(1-ethyl-2-pyrrolidinyl)methyl]-2,3-dimethoxy-5-iodobenzamide (PDB) resulted in a potent D-2 antagonist. Based upon these results and the concept that the potency of receptor ligands can be preserved when aromatic halogen substituents are replaced by fluoroalkyl functional groups, the authors synthesized a series of aryl-substituted fluoroalkyl PDBs and salicylamides. Synthetic pathways and an in vivo study in rats are outlined

  13. Identification of ortho-Substituted Benzoic Acid/Ester Derivatives via the Gas-Phase Neighboring Group Participation Effect in (+)-ESI High Resolution Mass Spectrometry.

    Science.gov (United States)

    Blincoe, William D; Rodriguez-Granillo, Agustina; Saurí, Josep; Pierson, Nicholas A; Joyce, Leo A; Mangion, Ian; Sheng, Huaming

    2018-04-01

    Benzoic acid/ester/amide derivatives are common moieties in pharmaceutical compounds and present a challenge in positional isomer identification by traditional tandem mass spectrometric analysis. A method is presented for exploiting the gas-phase neighboring group participation (NGP) effect to differentiate ortho-substituted benzoic acid/ester derivatives with high resolution mass spectrometry (HRMS 1 ). Significant water/alcohol loss (>30% abundance in MS 1 spectra) was observed for ortho-substituted nucleophilic groups; these fragment peaks are not observable for the corresponding para and meta-substituted analogs. Experiments were also extended to the analysis of two intermediates in the synthesis of suvorexant (Belsomra) with additional analysis conducted with nuclear magnetic resonance (NMR), density functional theory (DFT), and ion mobility spectrometry-mass spectrometry (IMS-MS) studies. Significant water/alcohol loss was also observed for 1-substituted 1, 2, 3-triazoles but not for the isomeric 2-substituted 1, 2, 3-triazole analogs. IMS-MS, NMR, and DFT studies were conducted to show that the preferred orientation of the 2-substituted triazole rotamer was away from the electrophilic center of the reaction, whereas the 1-subtituted triazole was oriented in close proximity to the center. Abundance of NGP product was determined to be a product of three factors: (1) proton affinity of the nucleophilic group; (2) steric impact of the nucleophile; and (3) proximity of the nucleophile to carboxylic acid/ester functional groups. Graphical Abstract ᅟ.

  14. Microwave-induced electrophilic addition of single-walled carbon nanotubes with alkylhalides

    Energy Technology Data Exchange (ETDEWEB)

    Xu Yang [Faculty of Materials Science and Engineering, Hubei University, Wuhan 430062 (China); Wang Xianbao [Faculty of Materials Science and Engineering, Hubei University, Wuhan 430062 (China); Ministry-of-Education, Key Laboratory for the Synthesis and Application of Organic Functional Molecules, Hubei University, Wuhan 430062 (China)], E-mail: wxb@hubu.edu.cn; Tian Rong; Li Shaoqing; Wan Li; Li Mingjian; You Haijun; Li Qin [Faculty of Materials Science and Engineering, Hubei University, Wuhan 430062 (China); Wang Shimin [Faculty of Materials Science and Engineering, Hubei University, Wuhan 430062 (China); Ministry-of-Education, Key Laboratory for the Synthesis and Application of Organic Functional Molecules, Hubei University, Wuhan 430062 (China)

    2008-02-15

    We report the microwave-induced electrophilic addition of single-walled carbon nanotubes (SWNTs) with alkylhalides using Lewis acid as a catalyst followed by hydrolysis. The reaction results in the attachment of alkyl and hydroxyl groups to the surface of the nanotubes. This rapid and high-energy microwave radiation is found to be highly efficient for this reaction, which only needs as low as several minutes. The resulting nanotubes were characterized with FTIR, UV-vis-NIR, Raman, TGA, TEM and AFM. It demonstrates that iodo-alkanes show higher reaction activity with SWNTs than chloro- and bromo-alkanes.

  15. Influence of methoxy- and nitro-substitutions in the aromatic ring on proton donation ability in hydrogen bond and on the amino group parameters of free and H-bonded molecules of 2-aminopyrimidine

    Science.gov (United States)

    Borisenko, V. E.; Krekov, S. A.; Fomenko, M. Yu.; Koll, A.; Lipkovski, P.

    2008-06-01

    Amino- and imino- forms of pyrimidine are widely presented as part of antibiotics, corrective medications for heart failures and metabolic stimulators. Hydrogen bonding is one of the fundamental interactions between biologically active molecules. This type of interactions provides flexibility, speed and variety of the biochemical processes. Proton donation properties of aminopyrimidines significantly depend on the position, number and kind of the substituent in its aromatic ring. In present work we studied the influence of the methoxy- and nitro-substitutions in the phenyl radical of pyridine and pyrimidine cycles on the proton donation ability of the amino group in hydrogen bonds as well as on its geometrical, force, electro-optical and thermodynamical characteristics in free and H-bonded (1:1 and 1:2, with various proton acceptors) molecules of primary aromatic amines. Acetonitrile, dioxane, tetrahydrofourane, dimethylformamide, dimethylsulfoxide and hexamethylphosphoramide (whose proton accepting properties vary within a wide range) were used as proton acceptors in our research. In the region of the amino group stretching and deformation vibrations the IR spectra of free and H-bonded (1:1) molecules of 2-amino-4,6-dimethoxy- and 2-amino-5-nitropyrimidine were studied in complexes with proton acceptors in CCl 4 within the temperature range 288-328 K. The spectra of 1:2 complexes were studied in undiluted aprotic solvents. The following spectral characteristics of absorption bands in amino group stretching vibrations were determined: M(0) (zero spectral moment, integrated intensity B); M(1) (first spectral moment, band "centre of gravity"); effective half width, related to the second central moment (Δ ν1/2) eff = 2( M(2)) 1/2, frequencies of the deformation vibrations δ(HNH) of free and H-bonded molecules. It was shown that changes of the absorption band spectral characteristics of the amino group stretching and deformation vibrations in the analyzed

  16. Modified solution calorimetry approach for determination of vaporization and sublimation enthalpies of branched-chain aliphatic and alkyl aromatic compounds at T = 298.15 K

    International Nuclear Information System (INIS)

    Varfolomeev, Mikhail A.; Novikov, Vladimir B.; Nagrimanov, Ruslan N.; Solomonov, Boris N.

    2015-01-01

    Highlights: • Solution enthalpies of 18 branching-chain alkyl aromatic and aliphatic compounds in cyclohexane were measured. • Group contributions to the enthalpy of solvation due to branching and substitution in carbon chain were evaluated. • Modified solution calorimetry based approach for determination of vaporization/sublimation enthalpies was proposed. • This approach provides vaporization/sublimation enthalpies directly at T = 298.15 K. • Vaporization/sublimation enthalpies of 35 branched-chain alkyl aromatic and aliphatic compounds were determined. - Abstract: The enthalpies of solution, solvation and vaporization/sublimation are interrelated values combined in the simplest thermodynamic circle. Hence, experimental determination of vaporization/sublimation enthalpy can be substituted by experimentally simpler determination of solution enthalpy when solvation enthalpy is known. Previously it was found that solvation enthalpies of a wide range of unbranched aliphatic and aromatic solutes in saturated hydrocarbons are in good linear correlation with their molar refraction values. This allows to estimate the vaporization/sublimation enthalpy of any unbranched organic compound from its solution enthalpy in saturated hydrocarbon and molar refraction. In the present work this approach was modified for determination of vaporization/sublimation enthalpy of branched-chain alkyl aromatic and aliphatic compounds. Group contributions to the enthalpy of solvation due to the branching of carbon chain were evaluated. Enthalpies of solution at infinite dilution of 18 branched-chain aliphatic and alkyl aromatic compounds were measured at T = 298.15 K. Vaporization/sublimation enthalpies for 35 branched aliphatic and alkyl aromatic compounds were determined by using modified solution calorimetry approach. These values are in good agreement with available literature data on vaporization/sublimation enthalpies obtained by conventional methods.

  17. A theoretical quantum study on the distribution of electrophilic and nucleophilic active sites on Cu(100) surfaces modeled as finite clusters

    International Nuclear Information System (INIS)

    Rios R, C.H.; Romero R, M.; Ponce R, A.; Mendoza H, L.H.

    2008-01-01

    In this work, it is shown a theoretical quantum study of the active sites distribution on a monocrystalline surface of Cu(100). The copper surface was modeled as finite clusters of 14, 23, 38 and 53 atoms. We performed Hartree-Fock and Density Functional Theory (B3LYP) ab initio calculations employing the pseudopotentials of Hay and Wadt (LANLlMB y LANL2DZ). From calculations, we found a work function value of 4.1 eV. The mapping of the HOMO and LUMO in the frozen core approximation, allowed us finding the electrophilic and nucleophilic active sites distribution, respectively. The results indicated that electrophilic sites on the Cu(100) surface were located on hollow position and its numerical density was 8.6 x 10 16 sites cm -2 . From the nucleophilic local softness study, it was found that the nucleophilic sites were formed by a group of atoms and it had a numerical density of 2.4x 10 16 sitescm -2 . Last results indicated that adsorptions with 2 x 2 and 3 x 3 distributions can be favored onto a Cu(100) surface for the electrophilic and nucleophilic cases, respectively. (Author)

  18. Spectroscopic Diagnosis of Excited-State Aromaticity: Capturing Electronic Structures and Conformations upon Aromaticity Reversal.

    Science.gov (United States)

    Oh, Juwon; Sung, Young Mo; Hong, Yongseok; Kim, Dongho

    2018-03-06

    Aromaticity, the special energetic stability derived from cyclic [4 n + 2]π-conjugated electronic structures, has been the topic of intense interest in chemistry because it plays a critical role in rationalizing molecular stability, reactivity, and physical/chemical properties. Recently, the pioneering work by Colin Baird on aromaticity reversal, postulating that aromatic (antiaromatic) character in the ground state reverses to antiaromatic (aromatic) character in the lowest excited triplet state, has attracted much scientific attention. The completely reversed aromaticity in the excited state provides direct insight into understanding the photophysical/chemical properties of photoactive materials. In turn, the application of aromatic molecules to photoactive materials has led to numerous studies revealing this aromaticity reversal. However, most studies of excited-state aromaticity have been based on the theoretical point of view. The experimental evaluation of aromaticity in the excited state is still challenging and strenuous because the assessment of (anti)aromaticity with conventional magnetic, energetic, and geometric indices is difficult in the excited state, which practically restricts the extension and application of the concept of excited-state aromaticity. Time-resolved optical spectroscopies can provide a new and alternative avenue to evaluate excited-state aromaticity experimentally while observing changes in the molecular features in the excited states. Time-resolved optical spectroscopies take advantage of ultrafast laser pulses to achieve high time resolution, making them suitable for monitoring ultrafast changes in the excited states of molecular systems. This can provide valuable information for understanding the aromaticity reversal. This Account presents recent breakthroughs in the experimental assessment of excited-state aromaticity and the verification of aromaticity reversal with time-resolved optical spectroscopic measurements. To

  19. Synthesis and Fungicidal activity of some sulphide derivatives of O-Ethyl-N-substituted phenylcarbamates

    International Nuclear Information System (INIS)

    Imeokparia, F.A.

    2006-01-01

    Monosulphides of O-ethyl-N-substituted phenylcarbamates were prepared by the reaction between O-ethyl-N-substituted phenylcarbamates and sulphur dichloride, while the corresponding disulphides were prepared by the reaction between O-ethyl-N-substituted phenylcarbamates and sulphur monochloride. The synthesized compounds were characterized by elemental analysis, thin layer chromatography (TLC), Fourier-transform infrared, and /sup 1/H and /sup 13/C nuclear magnetic resonance spectroscopic techniques. In vitro fungicidal assay of these sulphides against Fusarium oxysporum, Aspergillus niger, Aspergillus flavus and Rhizopus stolonifer showed that they had Greater fungicidal activity than their parent carbamates. The synthesized sulphides were more active towards A. Niger and A. flavus. Unlike the parent carbamates, the type of substituents attached to the aromatic nucleus of these sulphides had little or no effect on their fungicidal activity as there was insignificant variation in the fungicidal activity of the monosulphide and the disulphide derivatives of O-ethyl-N-substituted phenylcarbamates. (author)

  20. Formation of Polycyclic Aromatic Hydrocarbons and Nitrogen Containing Polycyclic Aromatic Compounds in Titan's Atmosphere, the Interstellar Medium and Combustion

    Science.gov (United States)

    Landera, Alexander

    2013-12-01

    Several different mechanisms leading to the formation of (substituted) naphthalene and azanaphthalenes were examined using theoretical quantum chemical calculations. As a result, a series of novel synthetic routes to Polycyclic Aromatic Hydrocarbons (PAHs) and Nitrogen Containing Polycyclic Aromatic Compounds (N-PACs) have been proposed. On Earth, these aromatic compounds originate from incomplete combustion and are released into our environment, where they are known to be major pollutants, often with carcinogenic properties. In the atmosphere of a Saturn's moon Titan, these PAH and N-PACs are believed to play a critical role in organic haze formation, as well as acting as chemical precursors to biologically relevant molecules. The theoretical calculations were performed by employing the ab initio G3(MP2,CC)/B3LYP/6-311G** method to effectively probe the Potential Energy Surfaces (PES) relevant to the PAH and N-PAC formation. Following the construction of the PES, Rice-Ramsperger-Kassel-Markus (RRKM) theory was used to evaluate all unimolecular rate constants as a function of collision energy under single-collision conditions. Branching ratios were then evaluated by solving phenomenological rate expressions for the various product concentrations. The most viable pathways to PAH and N-PAC formation were found to be those where the initial attack by the ethynyl (C2H) or cyano (CN) radical toward a unsaturated hydrocarbon molecule led to the formation of an intermediate which could not effectively lose a hydrogen atom. It is not until ring cyclization has occurred, that hydrogen elimination leads to a closed shell product. By quenching the possibility of the initial hydrogen atom elimination, one of the most competitive processes preventing the PAH or N-PAC formation was avoided, and the PAH or N-PAC formation was allowed to proceed. It is concluded that these considerations should be taken into account when attempting to explore any other potential routes towards

  1. Structural and spectral comparisons between isomeric benzisothiazole and benzothiazole based aromatic heterocyclic dyes

    Science.gov (United States)

    Wang, Yin-Ge; Wang, Yue-Hua; Tao, Tao; Qian, Hui-Fen; Huang, Wei

    2015-09-01

    A pair of isomeric heterocyclic compounds, namely 3-amino-5-nitro-[2,1]-benzisothiazole and 2-amino-6-nitrobenzothiazole, are used as the diazonium components to couple with two N-substituted 4-aminobenzene derivatives. As a result, two pairs of isomeric aromatic heterocyclic azo dyes have been produced and they are structurally and spectrally characterized and compared including single-crystal structures, electronic spectra, solvatochromism and reversible acid-base discoloration, thermal stability and theoretically calculations. It is concluded that both benzisothiazole and benzothiazole based dyes show planar molecular structures and offset π-π stacking interactions, solvatochromism and reversible acid-base discoloration. Furthermore, benzisothiazole based aromatic heterocyclic dyes exhibit higher thermal stability, larger solvatochromic effects and maximum absorption wavelengths than corresponding benzothiazole based ones, which can be explained successfully by the differences of their calculated isomerization energy, dipole moment and molecular band gaps.

  2. A fluorescence high throughput screening method for the detection of reactive electrophiles as potential skin sensitizers

    Energy Technology Data Exchange (ETDEWEB)

    Avonto, Cristina; Chittiboyina, Amar G. [National Center for Natural Products Research, Research Institute of Pharmaceutical Sciences, School of Pharmacy, The University of Mississippi, University, MS 38677 (United States); Rua, Diego [The Center for Food Safety and Applied Nutrition, US Food and Drug Administration, College Park, MD 20740 (United States); Khan, Ikhlas A., E-mail: ikhan@olemiss.edu [National Center for Natural Products Research, Research Institute of Pharmaceutical Sciences, School of Pharmacy, The University of Mississippi, University, MS 38677 (United States); Division of Pharmacognosy, Department of BioMolecular Sciences, School of Pharmacy, The University of Mississippi, University, MS 38677 (United States)

    2015-12-01

    Skin sensitization is an important toxicological end-point in the risk assessment of chemical allergens. Because of the complexity of the biological mechanisms associated with skin sensitization, integrated approaches combining different chemical, biological and in silico methods are recommended to replace conventional animal tests. Chemical methods are intended to characterize the potential of a sensitizer to induce earlier molecular initiating events. The presence of an electrophilic mechanistic domain is considered one of the essential chemical features to covalently bind to the biological target and induce further haptenation processes. Current in chemico assays rely on the quantification of unreacted model nucleophiles after incubation with the candidate sensitizer. In the current study, a new fluorescence-based method, ‘HTS-DCYA assay’, is proposed. The assay aims at the identification of reactive electrophiles based on their chemical reactivity toward a model fluorescent thiol. The reaction workflow enabled the development of a High Throughput Screening (HTS) method to directly quantify the reaction adducts. The reaction conditions have been optimized to minimize solubility issues, oxidative side reactions and increase the throughput of the assay while minimizing the reaction time, which are common issues with existing methods. Thirty-six chemicals previously classified with LLNA, DPRA or KeratinoSens™ were tested as a proof of concept. Preliminary results gave an estimated 82% accuracy, 78% sensitivity, 90% specificity, comparable to other in chemico methods such as Cys-DPRA. In addition to validated chemicals, six natural products were analyzed and a prediction of their sensitization potential is presented for the first time. - Highlights: • A novel fluorescence-based method to detect electrophilic sensitizers is proposed. • A model fluorescent thiol was used to directly quantify the reaction products. • A discussion of the reaction workflow

  3. A fluorescence high throughput screening method for the detection of reactive electrophiles as potential skin sensitizers

    International Nuclear Information System (INIS)

    Avonto, Cristina; Chittiboyina, Amar G.; Rua, Diego; Khan, Ikhlas A.

    2015-01-01

    Skin sensitization is an important toxicological end-point in the risk assessment of chemical allergens. Because of the complexity of the biological mechanisms associated with skin sensitization, integrated approaches combining different chemical, biological and in silico methods are recommended to replace conventional animal tests. Chemical methods are intended to characterize the potential of a sensitizer to induce earlier molecular initiating events. The presence of an electrophilic mechanistic domain is considered one of the essential chemical features to covalently bind to the biological target and induce further haptenation processes. Current in chemico assays rely on the quantification of unreacted model nucleophiles after incubation with the candidate sensitizer. In the current study, a new fluorescence-based method, ‘HTS-DCYA assay’, is proposed. The assay aims at the identification of reactive electrophiles based on their chemical reactivity toward a model fluorescent thiol. The reaction workflow enabled the development of a High Throughput Screening (HTS) method to directly quantify the reaction adducts. The reaction conditions have been optimized to minimize solubility issues, oxidative side reactions and increase the throughput of the assay while minimizing the reaction time, which are common issues with existing methods. Thirty-six chemicals previously classified with LLNA, DPRA or KeratinoSens™ were tested as a proof of concept. Preliminary results gave an estimated 82% accuracy, 78% sensitivity, 90% specificity, comparable to other in chemico methods such as Cys-DPRA. In addition to validated chemicals, six natural products were analyzed and a prediction of their sensitization potential is presented for the first time. - Highlights: • A novel fluorescence-based method to detect electrophilic sensitizers is proposed. • A model fluorescent thiol was used to directly quantify the reaction products. • A discussion of the reaction workflow

  4. Chlorination of tramadol: Reaction kinetics, mechanism and genotoxicity evaluation.

    Science.gov (United States)

    Cheng, Hanyang; Song, Dean; Chang, Yangyang; Liu, Huijuan; Qu, Jiuhui

    2015-12-01

    Tramadol (TRA) is one of the most detected analgesics in environmental matrices, and it is of high significance to study the reactivity of TRA during chlorination considering its potential toxicity to the environment. The chlorine/TRA reaction is first order with respect to the TRA concentration, and a combination of first-order and second-order with respect to chlorine concentration. The pH dependence of the observed rate constants (kobs) showed that the TRA oxidation reactivity increased with increasing pH. kobs can be quantitatively described by considering all active species including Cl2, Cl2O and HOCl, and the individual rate constants of HOCl/TRA(0), HOCl/TRAH(+), Cl2/TRA and Cl2O/TRA reactions were calculated to be (2.61±0.29)×10(3)M(-1)s(-1), 14.73±4.17M(-1)s(-1), (3.93±0.34)×10(5)M(-1)s(-1) and (5.66±1.83)×10(6)M(-1)s(-1), respectively. Eleven degradation products were detected with UPLC-Q-TOF-MS, and the corresponding structures of eight products found under various pH conditions were proposed. The amine group was proposed to be the initial attack site under alkaline pH conditions, where reaction of the deprotonated amine group with HOCl is favorable. Under acidic and neutral pH conditions, however, two possible reaction pathways were proposed. One is an electrophilic substitution on the aromatic ring, and another is an electrophilic substitution on the nitrogen, leading to an N-chlorinated intermediate, which can be further oxidized. Finally, the SOS/umu test showed that the genotoxicity of TRA chlorination products increased with increasing dosage of chlorine, which was mostly attributed to the formation of some chlorine substitution products. Copyright © 2015 Elsevier Ltd. All rights reserved.

  5. Development of Copper-Catalyzed Electrophilic Trifluoromethylation and Exploiting Cu/Cu2O Nanowires with Novel Catalytic Reactivity

    KAUST Repository

    Li, Huaifeng

    2014-06-01

    This thesis is based on research in Cu-catalyzed electrophilic trifluoromethylation and exploiting Cu/Cu2O nanowires with novel catalytic reactivity for developing of catalytic and greener synthetic methods. A large number of biological active pharmaceuticals and agrochemicals contain fluorine substituents (-F) or trifluoromethyl groups (-CF3) because these moieties often result in profound changes of their physical, chemical, and biological properties, such as metabolic stability and lipophilicity. For this reason, the introduction of fluorine or trifluoromethyl groups into organic molecules has attracted intensive attention. Among them, transition metal-catalyzed trifluoromethylation reactions has proved to be an efficient and reliable strategy to construct carbon-fluorine (C-F) and carbontrifluoromethyl (C-CF3) bond. We have developed a catalytic process for the first time for trifluoromethylation of terminal alkynes with Togni’s reagent, affording trifluoromethylated acetylenes in good to excellent yields. The reaction is conducted at room temperature and exhibits tolerance to a range of functional groups. Derived from this discovery, the extension of work of copper catalyzed electrophilic trifluoromethylation were investigated which include the electrophilic trifluoromethylation of arylsulfinate salts and electrophilic trifluoromethylation of organotrifluoroborates. Because of growing environmental concern, the development of greener synthetic methods has drawn much attention. Nano-sized catalysts are environment-friendly and an attractive green alternative to the conventional homogeneous catalysts. The nano-sized catalysts can be easily separated from the reaction mixture due to their insolubility and thus they can be used recycled. Notably, because of the high reactivities of nano-sized metal catalysts, the use of ligands can be avoided and the catalysts loadings can be reduced greatly. Moreover, the nano-sized catalysts can increase the exposed surface

  6. Transforming plastic surfaces with electrophilic backbones from hydrophobic to hydrophilic.

    Science.gov (United States)

    Kim, Samuel; Bowen, Raffick A R; Zare, Richard N

    2015-01-28

    We demonstrate a simple nonaqueous reaction scheme for transforming the surface of plastics from hydrophobic to hydrophilic. The chemical modification is achieved by base-catalyzed trans-esterification with polyols. It is permanent, does not release contaminants, and causes no optical or mechanical distortion of the plastic. We present contact angle measurements to show successful modification of several types of plastics including poly(ethylene terephthalate) (PET) and polycarbonate (PC). Its applicability to blood analysis is explored using chemically modified PET blood collection tubes and found to be quite satisfactory. We expect this approach will reduce the cost of manufacturing plastic devices with optimized wettability and can be generalized to other types of plastic materials having an electrophilic linkage as its backbone.

  7. Distribution and geochemical application of aromatic hydrocarbons in crude oils

    International Nuclear Information System (INIS)

    Asif, M.; Tahira, F.

    2007-01-01

    Distribution of aromatic hydrocarbons was studied in a set of crude oils, five from northern Indus basin of potwar area and two from southern Indus basin. Diaromatic and triaromatic hydrocarbons were separated from highly complex mixture of sedimentary organic matter by using liquid chromatography techniques such as column chromatography, TLC and GC-FID. These classes of compounds were identified to alkylated isomers of naphthalenes and phenanthrenes by using reference chromatograms and literature data. High concentration of di-,tri- and tetra-methyl naphthalenes was observed in all crude oils except Kal. The relative increase in concentration of alkyl naphthalenes was found as moved to higher methyl substituted isomers. This suggests that they are the product of sedimentary alkylation reactions during catagensis and metagensis. The significant concentration of methyl phenanthrenes indicated source of organic matter. High levels of both 1-MP and 9-MP showed marine and terrestrial source of organic matter except Umer crude oil which is most likely to have terrestrial origin. The ratios of beta-substituted to the alpha-substituted isomers of both alkyl naphthalenes and alkyl phenanthrene were used to assess the thermal maturity of sedimentary organic matter, which revealed high maturity level of Dhurnal, Pindori, Badin and Toot crude oils. (author)

  8. Synthesis, characterization and pharmacological evaluation of substituted phenoxy acetamide derivatives

    Directory of Open Access Journals (Sweden)

    Rani Priyanka

    2015-01-01

    Full Text Available A novel series of 2-(substituted phenoxy-N-(1,7,7-trimethylbicyclo[2.2.1]heptan-2-ylacetamide and N-(2-bromocyclohexyl-2-(substituted phenoxyacetamide derivatives having cyclohexyl nucleus as common in both types were synthesized and assessed for their anti-inflammatory activity by a carrageenan induced rat paw oedema method, analgesic activity by Eddy’s hot plate method and antipyretic activity by brewer’s yeast induced pyrexia method. All the novel derivatives have been synthesized by the reaction of camphor and similar ketone having cyclohexane nucleus (e.g. 2-bromocyclohexanone with ammonium carbonate and formic acid resulting in the formation of aromatic amines (1a-b. These amines on further chloroacetylation with chloroacetylchloride give compounds (2a-b. Compounds (2a-b are converted to 2-(substituted phenoxy-N-(1,7,7-trimethylbicyclo[2.2.1]heptan-2-yl acetamide and N-(2-bromocyclohexyl-2-(substituted phenoxyacetamide derivatives on treatment with substituted phenol. Among the series 3a-f, 3i, 3k, 3l compounds showed significant anti-inflammatory activity as compared to the standard drug diclofenac sodium and also compound 3a-f, 3h, 3j, 3k exhibit significant analgesic activity as compared to the standard drug. Compounds 3a-f and 3k showed antipyretic activity nearly to the standard drug indomethacin. Compounds 3a-f and 3k possess anti-inflammatory, analgesic and antipyretic activities near to the standard.

  9. Electrophilic acid gas-reactive fluid, proppant, and process for enhanced fracturing and recovery of energy producing materials

    Science.gov (United States)

    Fernandez, Carlos A.; Heldebrant, David J.; Bonneville, Alain; Jung, Hun Bok; Carroll, Kenneth C.

    2018-01-23

    An electrophilic acid gas-reactive fracturing fluid, proppant, and process are detailed. The fluid expands in volume to provide rapid and controlled increases in pressure that enhances fracturing in subterranean bedrock for recovery of energy-producing materials. The proppant stabilizes fracture openings in the bedrock to enhance recovery of energy-producing materials.

  10. Chameleonic reactivity of vicinal diazonium salt of acetylenyl-9,10-anthraquinones: synthetic application toward two heterocyclic targets.

    Science.gov (United States)

    Stepanov, A A; Gornostaev, L M; Vasilevsky, S F; Arnold, E V; Mamatyuk, V I; Fadeev, D S; Gold, B; Alabugin, I V

    2011-11-04

    The nature of products in the diazotization of 1-amino-2-acetylenyl-9,10-anthraquinones strongly depends on the nature of substituents at both the alkyne and at the anthraquinone core. Donor substitution (NHAr, OH) at the fourth position stabilizes the diazonium salt at C1, decelerating electrophilic cyclization at the arylethynyl substituent at C2. This effect allows the replacement of the diazonium with azide group and subsequent closure into isoxazole ring with preservation of the alkyne. In contrast, electrophilic 5-exo-dig cyclizations to condensed pyrazoles is observed for the combination of donor substituents at the aryl alkyne moiety and an OAc substituent at C4. The latter process provides a new synthetic route to 3-ethynyl-[1,9-cd]isoxazol-6-ones that are difficult to access otherwise. DFT calculations suggest that donor substituents have only a minor effect on alkyne and diazonium polarization in the reactant but provide specific transition state stabilization by stabilizing the incipient vinyl cation. This analysis provides the first computational data on electrophilic 5-exo-dig cyclization in its parent form and the nucleophile-promoted version. This cyclization is a relatively fast but endothermic process that is rendered thermodynamically feasible by the enol-keto tautomerization with concomitant aromatization in the five-membered heteroaromatic ring. Computations suggest that the importance of nucleophilic assistance in the transition state for a relatively weak nucleophile such as water is minor because the energy gain due to the Lewis base coordination to the carbocationic center is more than compensated for by the unfavorable entropic term for the bimolecular proces.

  11. Synthesis and ATRP of novel fluorinated aromatic monomer with pendant sulfonate group

    DEFF Research Database (Denmark)

    Dimitrov, Ivaylo; Jankova Atanasova, Katja; Hvilsted, Søren

    2013-01-01

    Novel, fluorinated monomer with pendant sulfonate group was synthesized utilizing a two-step derivatization of 2,3,4,5,6-pentafluorostyrene (FS). The first step was a nucleophilic substitution of the fluorine atom in para position by hydroxyl group followed by sulfopropylation. The monomer...... was polymerized under aqueous ATRP conditions to yield phenyl-fluorinated aromatic homopolymer bearing pendant sulfonates on each repeating unit. Furthermore, this polymer was used as macroinitiator for the ATRP of poly(ethylene glycol) methacrylate. The polymers were characterized by 1H NMR, SEC and FTIR...

  12. Aromatic chemical feedstocks from coal

    Energy Technology Data Exchange (ETDEWEB)

    Collin, G

    1982-06-01

    Liquid byproducts of coal carbonization meet some 25% of the world demand for aromatic chemicals, currently at approx. 30 million t/a, in particular 15% of the demand for benzene and over 95% of the demand for condensed aromatics and heteroaromatics. Industrial processing of the aromatic byproducts of coal pressure gasification is carried out to only a minor extent. Other methods that may be employed in future to obtain carbochemical aromatic compounds are solvolysis and supercritical gas extraction, the catalytic liquid-phase hydrogenation and hydropyrolysis of coal, which also permit recovery of benzene and homologues, phenols, and condensed and partially hydrogenated aromatics, and the synthesis of aromatics using methanol as the key compound. As with the present means of obtaining aromatic chemicals from coal, the processes that may in the future be applied on an industrial scale to obtain pure aromatics will only be economically feasible if linked with the manufacture of other mass products and combined with the present production of carbochemical aromatics.

  13. Aromatic raw materials from coal

    Energy Technology Data Exchange (ETDEWEB)

    Collin, G

    1982-06-01

    Liquid byproducts of coal carbonization meet some 25% of the world demand for aromatic chemicals, currently at approx. 30 million t/a, in particular 15% of the demand for benzene and over 95% of the demand for condensed aromatics and heteroaromatics. Industrial processing of the aromatic byproducts of coal pressure gasification is carried out to only a minor extent. Other methods that may be employed in future to obtain carbochemical aromatic compounds are solvolysis and supercritical gas extraction, the catalytic liquid-phase hydrogenation and hydropyrolysis of coal, which also permit recovery of benzene and homologues, phenols, and condensed and partially hydrogenated aromatics, and the synthesis of aromatics using methanol as the key compound. As with the present means of obtaining aromatic chemicals from coal, the processes that may in future be applied on an industrial scale to obtain pure aromatics will only be economically feasible if linked with the manufacture of other mass products and combined with the present production of carbochemical aromatics. (In German)

  14. Synthesis and Preliminary Characterization of a PPE-Type Polymer Containing Substituted Fullerenes and Transition Metal Ligation Sites

    Directory of Open Access Journals (Sweden)

    Corinne A. Basinger

    2015-01-01

    Full Text Available A substituted fullerene was incorporated into a PPE-conjugated polymer repeat unit. This subunit was then polymerized via Sonogashira coupling with other repeat units to create polymeric systems approaching 50 repeat units (based on GPC characterization. Bipyridine ligands were incorporated into some of these repeat units to provide sites for transition metal coordination. Photophysical characterization of the absorption and emission properties of these systems shows excited states located on both the fullerene and aromatic backbone of the polymers that exist in a thermally controlled equilibrium. Future work will explore other substituted polyaromatic systems using similar methodologies.

  15. Getting the Message? Native Reactive Electrophiles Pass Two Out of Three Thresholds to be Bona Fide Signaling Mediators.

    Science.gov (United States)

    Poganik, Jesse R; Long, Marcus J C; Aye, Yimon

    2018-05-01

    Precision cell signaling activities of reactive electrophilic species (RES) are arguably among the most poorly-understood means to transmit biological messages. Latest research implicates native RES to be a chemically-distinct subset of endogenous redox signals that influence cell decision making through non-enzyme-assisted modifications of specific proteins. Yet, fundamental questions remain regarding the role of RES as bona fide second messengers. Here, we lay out three sets of criteria we feel need to be met for RES to be considered as true cellular signals that directly mediate information transfer by modifying "first-responding" sensor proteins. We critically assess the available evidence and define the extent to which each criterion has been fulfilled. Finally, we offer some ideas on the future trajectories of the electrophile signaling field taking inspiration from work that has been done to understand canonical signaling mediators. Also see the video abstract here: https://youtu.be/rG7o0clVP0c. © 2018 WILEY Periodicals, Inc.

  16. N-Chloro and N-bromosaccharins: valuable reagents for halogenation of electron rich aromatics and cohalogenation of alkenes

    Directory of Open Access Journals (Sweden)

    Souza Soraia P. L. de

    2003-01-01

    Full Text Available N-Chloro- and N-bromosaccharins react with electron rich aromatic compounds (anisole, acetanilide, N,N-dimethylaniline producing halogenated compounds. The reaction with N-bromosaccharin gives para- substituted compounds only, whereas N-chlorosaccharin produces orto and para mixtures (para isomer predominantly, ca. 4-5 : 1. The reactions of the N-halosaccharins with alkenes (cyclohexene, styrene, a-methylstyrene, and 1-hexene give the corresponding halohydrins.

  17. Prenatal exposure to polycyclic aromatic hydrocarbons/aromatics, BDNF and child development

    International Nuclear Information System (INIS)

    Perera, Frederica; Phillips, David H.; Wang, Ya; Roen, Emily; Herbstman, Julie; Rauh, Virginia; Wang, Shuang; Tang, Deliang

    2015-01-01

    Objectives: Within a New York City (NYC) birth cohort, we assessed the associations between polycyclic aromatic hydrocarbon (PAH) and other aromatic DNA adducts and brain derived neurotrophic factor (BDNF) concentrations in umbilical cord blood, and neurodevelopment at age 2 years and whether BDNF is a mediator of the associations between PAH/aromatic-DNA adducts and neurodevelopment. Methods: PAH/aromatic-DNA adduct concentrations in cord blood were measured in 505 children born to nonsmoking African-American and Dominican women residing in NYC, and a subset was assessed for neurodevelopment at 2 years using the Bayley Scales of Infant Development Mental Development Index (MDI). A spectrum of PAH/aromatic-DNA adducts was measured using the 32 P-postlabeling assay; DNA adducts formed by benzo[a]pyrene (B[a]P), a representative PAH, were measured by High Performance Liquid Chromatography (HPLC)/fluorescence. BDNF mature protein in cord blood plasma was quantified by an ELISA. Multivariate regression analysis, adjusting for potential confounders, was conducted. Results: PAH/aromatic-DNA adduct concentration measured by postlabeling was inversely associated with BDNF concentration (p=0.02) and with MDI scores at 2 years (p=0.04). BDNF level was positively associated with MDI scores (p=0.003). Restricting to subjects having all three measures (PAH/aromatic-DNA adducts by postlabeling, MDI, and BDNF), results were similar but attenuated (p=0.13, p=0.05, p=0.01, respectively). Associations between B[a]P-DNA adducts and BDNF and B[a]P-DNA adducts and MDI at age 2 years were not significant. At age 3 years, the positive association of BDNF with MDI was not observed. Conclusions: The results at age 2 suggest that prenatal exposure to a spectrum of PAH/aromatic pollutants may adversely affect early neurodevelopment, in part by reducing BDNF levels during the fetal period. However, the same relationship was not seen at age 3. - Highlights: • Cord blood Polycyclic Aromatic

  18. Prenatal exposure to polycyclic aromatic hydrocarbons/aromatics, BDNF and child development

    Energy Technology Data Exchange (ETDEWEB)

    Perera, Frederica, E-mail: fpp1@columbia.edu [Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, 722 W. 168th St., New York, NY 10032 (United States); Columbia Center for Children' s Environmental Health, Columbia University, 722 W. 168th St., New York, NY 10032 (United States); Phillips, David H. [Analytical and Environmental Sciences Division, MRC-PHE Centre for Environment and Health, King' s College London, Franklin-Wilkins Building, London SE1 9NH (United Kingdom); Wang, Ya [Columbia Center for Children' s Environmental Health, Columbia University, 722 W. 168th St., New York, NY 10032 (United States); Department of Biostatistics, Mailman School of Public Health, Columbia University, 722 W. 168th St., New York, NY 10032 (United States); Roen, Emily; Herbstman, Julie [Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, 722 W. 168th St., New York, NY 10032 (United States); Columbia Center for Children' s Environmental Health, Columbia University, 722 W. 168th St., New York, NY 10032 (United States); Rauh, Virginia [Columbia Center for Children' s Environmental Health, Columbia University, 722 W. 168th St., New York, NY 10032 (United States); The Heilbrunn Department of Population and Family Health, Columbia University, 60 Haven Avenue, New York, NY 10032 (United States); Wang, Shuang [Columbia Center for Children' s Environmental Health, Columbia University, 722 W. 168th St., New York, NY 10032 (United States); Department of Biostatistics, Mailman School of Public Health, Columbia University, 722 W. 168th St., New York, NY 10032 (United States); Tang, Deliang [Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, 722 W. 168th St., New York, NY 10032 (United States); Columbia Center for Children' s Environmental Health, Columbia University, 722 W. 168th St., New York, NY 10032 (United States)

    2015-10-15

    Objectives: Within a New York City (NYC) birth cohort, we assessed the associations between polycyclic aromatic hydrocarbon (PAH) and other aromatic DNA adducts and brain derived neurotrophic factor (BDNF) concentrations in umbilical cord blood, and neurodevelopment at age 2 years and whether BDNF is a mediator of the associations between PAH/aromatic-DNA adducts and neurodevelopment. Methods: PAH/aromatic-DNA adduct concentrations in cord blood were measured in 505 children born to nonsmoking African-American and Dominican women residing in NYC, and a subset was assessed for neurodevelopment at 2 years using the Bayley Scales of Infant Development Mental Development Index (MDI). A spectrum of PAH/aromatic-DNA adducts was measured using the {sup 32}P-postlabeling assay; DNA adducts formed by benzo[a]pyrene (B[a]P), a representative PAH, were measured by High Performance Liquid Chromatography (HPLC)/fluorescence. BDNF mature protein in cord blood plasma was quantified by an ELISA. Multivariate regression analysis, adjusting for potential confounders, was conducted. Results: PAH/aromatic-DNA adduct concentration measured by postlabeling was inversely associated with BDNF concentration (p=0.02) and with MDI scores at 2 years (p=0.04). BDNF level was positively associated with MDI scores (p=0.003). Restricting to subjects having all three measures (PAH/aromatic-DNA adducts by postlabeling, MDI, and BDNF), results were similar but attenuated (p=0.13, p=0.05, p=0.01, respectively). Associations between B[a]P-DNA adducts and BDNF and B[a]P-DNA adducts and MDI at age 2 years were not significant. At age 3 years, the positive association of BDNF with MDI was not observed. Conclusions: The results at age 2 suggest that prenatal exposure to a spectrum of PAH/aromatic pollutants may adversely affect early neurodevelopment, in part by reducing BDNF levels during the fetal period. However, the same relationship was not seen at age 3. - Highlights: • Cord blood Polycyclic

  19. Substrate specific hydrolysis of aromatic and aromatic-aliphatic esters in orchid tissue cultures

    Directory of Open Access Journals (Sweden)

    Agnieszka Mironowicz

    2014-01-01

    Full Text Available We found that tissue cultures of higher plants were able, similarly as microorganisms, to transform low-molecular-weight chemical compounds. In tissue cultures of orchids (Cymbidium 'Saint Pierre' and Dendrobium phalaenopsis acetates of phenols and aromatic-aliphatic alcohols were hydrolyzed, whereas methyl esters of aromatic and aromatic-aliphatic acids did not undergo this reaction. Acetates of racemic aromatic-aliphatic alcohols were hydrolyzed with distinct enantiospecificity.

  20. New and Improved Methods of Production of Energy Rich Materials

    Science.gov (United States)

    1990-11-01

    The first two steps involve the acid catalysed formation of the nitroniun ion , the reactive electrophile, from nitric acid. The nitronium ion then...present in its molecular form (with some N2 03 also present). In acid solutions above 60-65% concentration it is present as nitrosonium ions . In an excess...Electrophilic Aromatic Nitration b~y the Nitronium Ion 1.2 Effect of Nitrous Acid 1.3 Nitration of Carbazoic. 1.4 Nitration of Dibenzothiophene -1.5

  1. General synthesis of C-glycosyl amino acids via proline-catalyzed direct electrophilic alpha-amination of C-glycosylalkyl aldehydes.

    Science.gov (United States)

    Nuzzi, Andrea; Massi, Alessandro; Dondoni, Alessandro

    2008-10-16

    Non-natural axially and equatorially linked C-glycosyl alpha-amino acids (glycines, alanines, and CH2-serine isosteres) with either S or R alpha-configuration were prepared by D- and L-proline-catalyzed (de >95%) alpha-amination of C-glycosylalkyl aldehydes using dibenzyl azodicarboxylate as the electrophilic reagent.

  2. Organic Chemistry Students' Fragmented Ideas about the Structure and Function of Nucleophiles and Electrophiles: A Concept Map Analysis

    Science.gov (United States)

    Anzovino, Mary E.; Bretz, Stacey Lowery

    2016-01-01

    Organic chemistry students struggle with multiple aspects of reaction mechanisms and the curved arrow notation used by organic chemists. Many faculty believe that an understanding of nucleophiles and electrophiles, among other concepts, is required before students can develop fluency with the electronpushing formalism (EPF). An expert concept map…

  3. Kinetics of electrophilic exchange of lanthanide(3) and copper(2) ions in aqueous solutions of ethylenediaminetetraacetates

    International Nuclear Information System (INIS)

    Nikitenko, S.I.; Martynenko, L.I.; Pechurova, N.I.; Spitsyn, V.I.

    1984-01-01

    Electrophilic exchange in the MA - - Cu 2+ (M 3+ =La 3+ , P 2 3+ , Nd 3+ , Eu 3+ , Gd 3+ , Tb 3+ , Er 3+ , Yb 3+ , A 4- =ethylenediaminetetraacetate) systems is studied. Copper is chosen as a constituent cation, because the stability of the CuA 2+ - complex is higher than that of the MA - complex, besides the CuA 2- , is characterized by a high extinction coefficient E 280 =3200. Electrophilic exchange in the systems is shown to be realized through the acid dissociation mechanism and through the association mechanism. Consideration of the acid dissociation mechanism assumes that the exchange is limited by a break in the metal-oxygen bond in the intermediate protonated complex. In case of the association mechanism it is limited by a break in the metal-nitrogen bond in the intermediate binuclear complex. Rate constants of the limiting stage are calculated. Dependences of the rate constants of exchange on the stability of the complexes, the order number of the element, acidity of medium, Cu 2+ concentration are given. Differences are shown to exist between the exchange mechanisms in the studied: systems for the REE of cerium and yttrium subgroups

  4. Vanadium-substituted heteropolyacids immobilized on amine- functionalized mesoporous MCM-41: A recyclable catalyst for selective oxidation of alcohols with H2O2

    International Nuclear Information System (INIS)

    Dong, Xinbo; Wang, Danjun; Li, Kebin; Zhen, Yanzhong; Hu, Huaiming; Xue, Ganglin

    2014-01-01

    Graphical abstract: Vanadium-substituted phosphotungstic acids are immobilized on amine- functionalized mesoporous MCM-41 and the hybrid catalyst is proved to be a highly efficient solid catalyst for the oxidation of aromatic alcohols to the corresponding carbonyl compounds with H 2 O 2 , featured by the high conversion and selectivity, easy recovery, and quite steady reuse. - Highlights: • Vanadium-substituted phosphotungstic acid immobilized on amine-functionalized mesoporous MCM-41 are prepared. • HPAs were fixed on the inner surface of mesoporous MCM-41 by chemical bonding to aminosilane groups. • The hybrid catalyst showed much higher catalytic activity than the pure HPAs. • The hybrid catalyst is a highly efficient recyclable solid catalyst for the selective oxidation of aromatic alcohols. - Abstract: New hybrid materials of vanadium-substituted phosphotungstic acids (VHPW) immobilized on amine-functionalized mesoporous MCM-41 (VHPW/MCM-41/NH 2 ) are prepared and characterized by FT-IR, XRD, N 2 adsorption, elemental analysis, SEM and TEM for their structural integrity and physicochemical properties. It is found that the structure of the heteropolyacids is retained upon immobilization over mesoporous materials. The catalytic activities of these hybrid materials are tested in the selective oxidation of alcohols to the carbonyl products with 30% aqueous H 2 O 2 as oxidant in toluene. The catalytic activities of different number of vanadium-substituted phosphotungstic acid are investigated, and among the catalysts, H 5 [PV 2 W 10 O 40 ] immobilized on amine-functionalized MCM-41 exhibits the highest activity with 97% conversion and 99% selectivity in the oxidation of benzyl alcohol to benzaldehyde. The hybrid catalyst is proved to be a highly efficient recyclable solid catalyst for the selective oxidation of aromatic alcohols to the corresponding aldehydes with H 2 O 2

  5. Parsing of the free energy of aromatic-aromatic stacking interactions in solution

    Energy Technology Data Exchange (ETDEWEB)

    Kostjukov, Viktor V.; Khomytova, Nina M. [Department of Physics, Sevastopol National Technical University, Sevastopol 99053, Crimea (Ukraine); Hernandez Santiago, Adrian A.; Tavera, Anna-Maria Cervantes; Alvarado, Julieta Salas [Faculty of Chemical Sciences, Autonomous University of Puebla, Puebla (Mexico); Evstigneev, Maxim P., E-mail: max_evstigneev@mail.ru [Department of Physics, Sevastopol National Technical University, Sevastopol 99053, Crimea (Ukraine)

    2011-10-15

    Graphical abstract: Highlights: > A protocol for decomposition of the free energy of aromatic stacking is developed. > The factors stabilizing/destabilizing stacking of aromatic molecules are defined. > Hydrophobic contribution is found to be dominant. - Abstract: We report an analysis of the energetics of aromatic-aromatic stacking interactions for 39 non-covalent reactions of self- and hetero-association of 12 aromatic molecules with different structures and charge states. A protocol for computation of the contributions to the total energy from various energetic terms has been developed and the results are consistent with experiment in 92% of all the systems studied. It is found that the contributions from hydrogen bonds and entropic factors are always unfavorable, whereas contributions from van-der-Waals, electrostatic and/or hydrophobic effects may lead to stabilizing or destabilizing factors depending on the system studied. The analysis carried out in this work provides an answer to the questions 'What forces stabilize/destabilize the stacking of aromatic molecules in aqueous-salt solution and what are their relative importance?'

  6. Parsing of the free energy of aromatic-aromatic stacking interactions in solution

    International Nuclear Information System (INIS)

    Kostjukov, Viktor V.; Khomytova, Nina M.; Hernandez Santiago, Adrian A.; Tavera, Anna-Maria Cervantes; Alvarado, Julieta Salas; Evstigneev, Maxim P.

    2011-01-01

    Graphical abstract: Highlights: → A protocol for decomposition of the free energy of aromatic stacking is developed. → The factors stabilizing/destabilizing stacking of aromatic molecules are defined. → Hydrophobic contribution is found to be dominant. - Abstract: We report an analysis of the energetics of aromatic-aromatic stacking interactions for 39 non-covalent reactions of self- and hetero-association of 12 aromatic molecules with different structures and charge states. A protocol for computation of the contributions to the total energy from various energetic terms has been developed and the results are consistent with experiment in 92% of all the systems studied. It is found that the contributions from hydrogen bonds and entropic factors are always unfavorable, whereas contributions from van-der-Waals, electrostatic and/or hydrophobic effects may lead to stabilizing or destabilizing factors depending on the system studied. The analysis carried out in this work provides an answer to the questions 'What forces stabilize/destabilize the stacking of aromatic molecules in aqueous-salt solution and what are their relative importance?'

  7. Catalytic aromatization of methane.

    Science.gov (United States)

    Spivey, James J; Hutchings, Graham

    2014-02-07

    Recent developments in natural gas production technology have led to lower prices for methane and renewed interest in converting methane to higher value products. Processes such as those based on syngas from methane reforming are being investigated. Another option is methane aromatization, which produces benzene and hydrogen: 6CH4(g) → C6H6(g) + 9H2(g) ΔG°(r) = +433 kJ mol(-1) ΔH°(r) = +531 kJ mol(-1). Thermodynamic calculations for this reaction show that benzene formation is insignificant below ∼600 °C, and that the formation of solid carbon [C(s)] is thermodynamically favored at temperatures above ∼300 °C. Benzene formation is insignificant at all temperatures up to 1000 °C when C(s) is included in the calculation of equilibrium composition. Interestingly, the thermodynamic limitation on benzene formation can be minimized by the addition of alkanes/alkenes to the methane feed. By far the most widely studied catalysts for this reaction are Mo/HZSM-5 and Mo/MCM-22. Benzene selectivities are generally between 60 and 80% at methane conversions of ∼10%, corresponding to net benzene yields of less than 10%. Major byproducts include lower molecular weight hydrocarbons and higher molecular weight substituted aromatics. However, carbon formation is inevitable, but the experimental findings show this can be kinetically limited by the use of H2 or oxidants in the feed, including CO2 or steam. A number of reactor configurations involving regeneration of the carbon-containing catalyst have been developed with the goal of minimizing the cost of regeneration of the catalyst once deactivated by carbon deposition. In this tutorial review we discuss the thermodynamics of this process, the catalysts used and the potential reactor configurations that can be applied.

  8. Engineering Aromatic-Aromatic Interactions To Nucleate Folding in Intrinsically Disordered Regions of Proteins.

    Science.gov (United States)

    Balakrishnan, Swati; Sarma, Siddhartha P

    2017-08-22

    Aromatic interactions are an important force in protein folding as they combine the stability of a hydrophobic interaction with the selectivity of a hydrogen bond. Much of our understanding of aromatic interactions comes from "bioinformatics" based analyses of protein structures and from the contribution of these interactions to stabilizing secondary structure motifs in model peptides. In this study, the structural consequences of aromatic interactions on protein folding have been explored in engineered mutants of the molten globule protein apo-cytochrome b 5 . Structural changes from disorder to order due to aromatic interactions in two variants of the protein, viz., WF-cytb5 and FF-cytb5, result in significant long-range secondary and tertiary structure. The results show that 54 and 52% of the residues in WF-cytb5 and FF-cytb5, respectively, occupy ordered regions versus 26% in apo-cytochrome b 5 . The interactions between the aromatic groups are offset-stacked and edge-to-face for the Trp-Phe and Phe-Phe mutants, respectively. Urea denaturation studies indicate that both mutants have a C m higher than that of apo-cytochrome b 5 and are more stable to chaotropic agents than apo-cytochrome b 5 . The introduction of these aromatic residues also results in "trimer" interactions with existing aromatic groups, reaffirming the selectivity of the aromatic interactions. These studies provide insights into the aromatic interactions that drive disorder-to-order transitions in intrinsically disordered regions of proteins and will aid in de novo protein design beyond small peptide scaffolds.

  9. Asymmetric functional contributions of acidic and aromatic side chains in sodium channel voltage-sensor domains

    DEFF Research Database (Denmark)

    Pless, Stephan Alexander; Elstone, Fisal D; Niciforovic, Ana P

    2014-01-01

    largely enigmatic. To this end, natural and unnatural side chain substitutions were made in the S2 hydrophobic core (HC), the extracellular negative charge cluster (ENC), and the intracellular negative charge cluster (INC) of the four VSDs of the skeletal muscle sodium channel isoform (NaV1......Voltage-gated sodium (NaV) channels mediate electrical excitability in animals. Despite strong sequence conservation among the voltage-sensor domains (VSDs) of closely related voltage-gated potassium (KV) and NaV channels, the functional contributions of individual side chains in Nav VSDs remain.......4). The results show that the highly conserved aromatic side chain constituting the S2 HC makes distinct functional contributions in each of the four NaV domains. No obvious cation-pi interaction exists with nearby S4 charges in any domain, and natural and unnatural mutations at these aromatic sites produce...

  10. Pro-aromatic and anti-aromatic π-conjugated molecules: an irresistible wish to be diradicals

    KAUST Repository

    Zeng, Zebing

    2015-01-01

    © 2015 The Royal Society of Chemistry. Aromaticity is an important concept to understand the stability and physical properties of π-conjugated molecules. Recent studies on pro-aromatic and anti-aromatic molecules revealed their irresistible tendency to become diradicals in the ground state. Diradical character thus becomes another very important concept and it is fundamentally correlated to the physical (optical, electronic and magnetic) properties and chemical reactivity of most of the organic optoelectronic materials. Molecules with distinctive diradical character show unique properties which are very different from those of traditional closed-shell π-conjugated systems, and thus they have many potential applications in organic electronics, spintronics, non-linear optics and energy storage. This critical review first introduces the fundamental electronic structure of Kekulé diradicals within the concepts of anti-aromaticity and pro-aromaticity in the context of Hückel aromaticity and diradical character. Then recent research studies on various stable/persistent diradicaloids based on pro-aromatic and anti-aromatic compounds are summarized and discussed with regard to their synthetic chemistry, physical properties, structure-property relationships and potential material applications. A summary and personal perspective is given at the end.

  11. 40 CFR 721.981 - Substituted naphtholoazo-substituted naphthalenyl-substituted azonaphthol chromium complex.

    Science.gov (United States)

    2010-07-01

    ... naphthalenyl-substituted azonaphthol chromium complex. 721.981 Section 721.981 Protection of Environment...-substituted naphthalenyl-substituted azonaphthol chromium complex. (a) Chemical substance and significant new... naphtholoazo-substituted naphthalenyl-substituted azonaphthol chromium complex (PMN P-93-1631) is subject to...

  12. XVIII Mendeleev congress on general and applied chemistry. Summaries of reports in five volumes. Volume 5. IV Russian-French symposium Supramolecular systems in chemistry and biology. II Russian-Indian symposium on organic chemistry. International symposium on present-day radiochemistry Radiochemistry: progress and prospects. International symposium Green chemistry, stable evolution and social responsibility of chemists. Symposium Nucleophilic hydrogen substitution in aromatic systems and related reactions

    International Nuclear Information System (INIS)

    2007-01-01

    The 5 volume of the XVIII Mendeleev congress on general and applied chemistry includes summaries of reports on the subjects of sypramolecular systems in chemistry and biology, organic chemistry, modern radiochemistry, green chemistry - development and social responsibility of chemists, nucleophilic hydrogen substitution in aromatic systems and related chemical reactions [ru

  13. Acrolein and thiol-reactive electrophiles suppress allergen-induced innate airway epithelial responses by inhibition of DUOX1 and EGFR.

    Science.gov (United States)

    Danyal, Karamatullah; de Jong, Willem; O'Brien, Edmund; Bauer, Robert A; Heppner, David E; Little, Andrew C; Hristova, Milena; Habibovic, Aida; van der Vliet, Albert

    2016-11-01

    Acrolein is a major thiol-reactive component of cigarette smoke (CS) that is thought to contribute to increased asthma incidence associated with smoking. Here, we explored the effects of acute acrolein exposure on innate airway responses to two common airborne allergens, house dust mite and Alternaria alternata, and observed that acrolein exposure of C57BL/6 mice (5 ppm, 4 h) dramatically inhibited innate airway responses to subsequent allergen challenge, demonstrated by attenuated release of the epithelial-derived cytokines IL-33, IL-25, and IL-1α. Acrolein and other anti-inflammatory thiol-reactive electrophiles, cinnamaldehyde, curcumin, and sulforaphane, similarly inhibited allergen-induced production of these cytokines from human or murine airway epithelial cells in vitro. Based on our previous observations indicating the importance of Ca 2+ -dependent signaling, activation of the NADPH oxidase DUOX1, and Src/EGFR-dependent signaling in allergen-induced epithelial secretion of these cytokines, we explored the impact of acrolein on these pathways. Acrolein and other thiol-reactive electrophiles were found to dramatically prevent allergen-induced activation of DUOX1 as well as EGFR, and acrolein was capable of inhibiting EGFR tyrosine kinase activity via modification of C797. Biotin-labeling strategies indicated increased cysteine modification and carbonylation of Src, EGFR, as well as DUOX1, in response to acrolein exposure in vitro and in vivo, suggesting that direct alkylation of these proteins on accessible cysteine residues may be responsible for their inhibition. Collectively, our findings indicate a novel anti-inflammatory mechanism of CS-derived acrolein and other thiol-reactive electrophiles, by directly inhibiting DUOX1- and EGFR-mediated airway epithelial responses to airborne allergens. Copyright © 2016 the American Physiological Society.

  14. Tether-directed synthesis of highly substituted oxasilacycles via an intramolecular allylation employing allylsilanes

    Directory of Open Access Journals (Sweden)

    Cox Liam R

    2007-02-01

    Full Text Available Abstract Background Using a silyl tether to unite an aldehyde electrophile and allylsilane nucleophile into a single molecule allows a subsequent Lewis-acid-mediated allylation to proceed in an intramolecular sense and therefore receive all the benefits associated with such processes. However, with the ability to cleave the tether post allylation, a product that is the result of a net intermolecular reaction can be obtained. In the present study, four diastereoisomeric β-silyloxy-α-methyl aldehydes, which contain an allylsilane tethered through the β-carbinol centre, have been prepared, in order to probe how the relative configuration of the two stereogenic centres affects the efficiency and selectivity of the intramolecular allylation. Results Syn-aldehydes, syn-4a and syn-4b, both react poorly, affording all four possible diastereoisomeric oxasilacycle products. In contrast, the anti aldehydes anti-4a and anti-4b react analogously to substrates that lack substitution at the α-site, affording only two of the four possible allylation products. Conclusion The outcome of the reaction with anti-aldehydes is in accord with reaction proceeding through a chair-like transition state (T.S.. In these systems, the sense of 1,3-stereoinduction can be rationalised by the aldehyde electrophile adopting a pseudoaxial orientation, which will minimise dipole-dipole interactions in the T.S. The 1,4-stereoinduction in these substrates is modest and seems to be modulated by the R substituent in the starting material. In the case of the syn-substrates, cyclisation through a chair T.S. is unlikely as this would require the methyl substituent α to the reacting carbonyl group to adopt an unfavourable pseudoaxial position. It is therefore proposed that these substrates react through poorly-defined T.S.s and consequently exhibit essentially no stereoselectivity.

  15. Vanadium-substituted heteropolyacids immobilized on amine- functionalized mesoporous MCM-41: A recyclable catalyst for selective oxidation of alcohols with H{sub 2}O{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Xinbo [Key Laboratory of Synthetic and Natural Functional Molecule Chemistry, Department of Chemistry (Ministry of Education), Northwest University, Xi' an 710069 (China); Wang, Danjun [Key Laboratory of Synthetic and Natural Functional Molecule Chemistry, Department of Chemistry (Ministry of Education), Northwest University, Xi' an 710069 (China); College of Chemistry Chemical Engineering, Yanan University, Shaanxi Key Laboratory of Chemical Reaction Engineering, Yan' an 716000 (China); Li, Kebin [Key Laboratory of Synthetic and Natural Functional Molecule Chemistry, Department of Chemistry (Ministry of Education), Northwest University, Xi' an 710069 (China); Zhen, Yanzhong [Key Laboratory of Synthetic and Natural Functional Molecule Chemistry, Department of Chemistry (Ministry of Education), Northwest University, Xi' an 710069 (China); College of Chemistry Chemical Engineering, Yanan University, Shaanxi Key Laboratory of Chemical Reaction Engineering, Yan' an 716000 (China); Hu, Huaiming [Key Laboratory of Synthetic and Natural Functional Molecule Chemistry, Department of Chemistry (Ministry of Education), Northwest University, Xi' an 710069 (China); Xue, Ganglin, E-mail: xglin707@163.com [Key Laboratory of Synthetic and Natural Functional Molecule Chemistry, Department of Chemistry (Ministry of Education), Northwest University, Xi' an 710069 (China)

    2014-09-15

    Graphical abstract: Vanadium-substituted phosphotungstic acids are immobilized on amine- functionalized mesoporous MCM-41 and the hybrid catalyst is proved to be a highly efficient solid catalyst for the oxidation of aromatic alcohols to the corresponding carbonyl compounds with H{sub 2}O{sub 2}, featured by the high conversion and selectivity, easy recovery, and quite steady reuse. - Highlights: • Vanadium-substituted phosphotungstic acid immobilized on amine-functionalized mesoporous MCM-41 are prepared. • HPAs were fixed on the inner surface of mesoporous MCM-41 by chemical bonding to aminosilane groups. • The hybrid catalyst showed much higher catalytic activity than the pure HPAs. • The hybrid catalyst is a highly efficient recyclable solid catalyst for the selective oxidation of aromatic alcohols. - Abstract: New hybrid materials of vanadium-substituted phosphotungstic acids (VHPW) immobilized on amine-functionalized mesoporous MCM-41 (VHPW/MCM-41/NH{sub 2}) are prepared and characterized by FT-IR, XRD, N{sub 2} adsorption, elemental analysis, SEM and TEM for their structural integrity and physicochemical properties. It is found that the structure of the heteropolyacids is retained upon immobilization over mesoporous materials. The catalytic activities of these hybrid materials are tested in the selective oxidation of alcohols to the carbonyl products with 30% aqueous H{sub 2}O{sub 2} as oxidant in toluene. The catalytic activities of different number of vanadium-substituted phosphotungstic acid are investigated, and among the catalysts, H{sub 5}[PV{sub 2}W{sub 10}O{sub 40}] immobilized on amine-functionalized MCM-41 exhibits the highest activity with 97% conversion and 99% selectivity in the oxidation of benzyl alcohol to benzaldehyde. The hybrid catalyst is proved to be a highly efficient recyclable solid catalyst for the selective oxidation of aromatic alcohols to the corresponding aldehydes with H{sub 2}O{sub 2}.

  16. Bacterial degradation of monocyclic aromatic amines

    Directory of Open Access Journals (Sweden)

    Pankaj Kumar Arora

    2015-08-01

    Full Text Available Aromatic amines are an important group of industrial chemicals, which are widely used for manufacturing of dyes, pesticides, drugs, pigments, and other industrial products. These compounds have been considered highly toxic to human beings due to their carcinogenic nature. Three groups of aromatic amines have been recognized: monocyclic, polycyclic and heterocyclic aromatic amines. Bacterial degradation of several monocyclic aromatic compounds has been studied in a variety of bacteria, which utilizes monocyclic aromatic amines as their sole source of carbon and energy. Several degradation pathways have been proposed and the related enzymes and genes have also been characterized. Many reviews have been reviewed toxicity of monocyclic aromatic amines; however, there is lack of review on biodegradation of monocyclic aromatic amines. The aim of this review is to summarize bacterial degradation of monocyclic aromatic amines. This review will increase our current understanding of biochemical and molecular basis of bacterial degradation of monocyclic aromatic amines.

  17. Atmospheric chlorinated polycyclic aromatic hydrocarbons in East Asia.

    Science.gov (United States)

    Kakimoto, Kensaku; Nagayoshi, Haruna; Konishi, Yoshimasa; Kajimura, Keiji; Ohura, Takeshi; Hayakawa, Kazuichi; Toriba, Akira

    2014-09-01

    This study estimates atmospheric concentrations of chlorinated polycyclic aromatic hydrocarbons (ClPAHs) and polycyclic aromatic hydrocarbons (PAHs) in East Asia using a Gas Chromatograph with High Resolution Mass Spectrometer (GC-HRMS). ClPAHs are ubiquitously generated from PAHs through substitution, and some ClPAHs show higher aryl hydrocarbon receptor (AhR)-mediated activities than their parent PAHs. Atmospheric particles were collected using a high-volume air sampler equipped with a quartz-fiber filter. We determined the ClPAH concentrations of atmospheric particles collected in Japan (Sapporo, Sagamihara, Kanazawa, and Kitakyushu), Korea (Busan), and China (Beijing). The concentrations of ClPAHs were highest in the winter Beijing sample, where the total mean concentration was approximately 15-70 times higher than in the winter samples from Japan and Korea. The concentrations of Σ19ClPAHs and Σ9PAHs were significantly correlated in the Kanazawa and the Busan samples. This indicates that within those cities ClPAHs and PAHs share the same origin, implying direct chlorination of parent PAHs. Toxic equivalent concentrations (TEQs) of the total ClPAHs and PAHs were lowest in Kanazawa in the summer, reaching 1.18 and 2610fg-TEQm(-3) respectively, and highest in Beijing in the winter, reaching 627 and 4240000fg-TEQm(-3) respectively. Copyright © 2014 Elsevier Ltd. All rights reserved.

  18. Selenium-mediated synthesis of biaryls through rearrangement.

    Science.gov (United States)

    Shahzad, Sohail A; Vivant, Clotilde; Wirth, Thomas

    2010-03-19

    A new cyclization of beta-keto ester substituted stilbene derivatives using selenium electrophiles in the presence of Lewis acids is described. Substituted naphthols are obtained through cyclization and subsequent 1,2-rearrangement of aryl groups under very mild reaction conditions.

  19. 2?Diazo?1?phenyl?2?((trifluoromethyl)sulfonyl)ethan?1?one: Another Utility for Electrophilic Trifluoromethylthiolation Reactions

    OpenAIRE

    Huang, Zhongyan; Okuyama, Kenta; Wang, Chen; Tokunaga, Etsuko; Li, Xiaorui; Shibata, Norio

    2016-01-01

    Abstract 2?Diazo?1?phenyl?2?((trifluoromethyl)sulfonyl)ethan?1?one (diazo?triflone) (2) is not only a building block but also a reagent. In this study, diazo?triflone, which was originally used for the synthesis of ??lactam triflones as a trifluoromethanesulfonyl (SO2CF3) building block under catalyst?free thermal conditions, is redisclosed as an effective electrophilic trifluoromethylthiolation reagent under copper catalysis. A broad set of enamines, indoles, ??keto esters, pyrroles, and ani...

  20. Structure, function and carcinogenicity of metabolites of methylated and non-methylated polycyclic aromatic hydrocarbons: a comprehensive review.

    Science.gov (United States)

    Flesher, James W; Lehner, Andreas F

    2016-01-01

    The Unified Theory of PAH Carcinogenicity accommodates the activities of methylated and non-methylated polycyclic aromatic hydrocarbons (PAHs) and states that substitution of methyl groups on meso-methyl substituted PAHs with hydroxy, acetoxy, chloride, bromide or sulfuric acid ester groups imparts potent cancer producing properties. It incorporates specific predictions from past researchers on the mechanism of carcinogenesis by methyl-substituted hydrocarbons, including (1) requirement for metabolism to an ArCH2X type structure where X is a good leaving group and (2) biological substitution of a meso-methyl group at the most reactive center in non-methylated hydrocarbons. The Theory incorporates strong inferences of Fieser: (1) The mechanism of carcinogenesis involves a specific metabolic substitution of a hydrocarbon at its most reactive center and (2) Metabolic elimination of a carcinogen is a detoxifying process competitive with that of carcinogenesis and occurring by a different mechanism. According to this outlook, chemical or biochemical substitution of a methyl group at the reactive meso-position of non-methylated hydrocarbons is the first step in the mechanism of carcinogenesis for most, if not all, PAHs and the most potent metabolites of PAHs are to be found among the meso methyl-substituted hydrocarbons. Some PAHs and their known or potential metabolites and closely related compounds have been tested in rats for production of sarcomas at the site of subcutaneous injection and the results strongly support the specific predictions of the Unified Theory.

  1. The Role of Human Aldo-Keto Reductases in the Metabolic Activation and Detoxication of Polycyclic Aromatic Hydrocarbons: Interconversion of PAH Catechols and PAH o-Quinones

    Science.gov (United States)

    Zhang, Li; Jin, Yi; Huang, Meng; Penning, Trevor M.

    2012-01-01

    Polycyclic aromatic hydrocarbons (PAH) are ubiquitous environmental pollutants. They are procarcinogens requiring metabolic activation to elicit their deleterious effects. Aldo-keto reductases (AKR) catalyze the oxidation of proximate carcinogenic PAH trans-dihydrodiols to yield electrophilic and redox-active PAH o-quinones. AKRs are also found to be capable of reducing PAH o-quinones to form PAH catechols. The interconversion of o-quinones and catechols results in the redox-cycling of PAH o-quinones to give rise to the generation of reactive oxygen species and subsequent oxidative DNA damage. On the other hand, PAH catechols can be intercepted through phase II metabolism by which PAH o-quinones could be detoxified and eliminated. The aim of the present review is to summarize the role of human AKRs in the metabolic activation/detoxication of PAH and the relevance of phase II conjugation reactions to human lung carcinogenesis. PMID:23162467

  2. Variations in the Peak Position of the 6.2 micron Interstellar Emission Feature: A Tracer of N in the Interstellar Polycyclic Aromatic Hydrocarbon Population

    Science.gov (United States)

    Hudgins, Douglas M.; Bauschlicher, Charles W.; Allamandola, L. J.

    2005-01-01

    This paper presents the results of an investigation of the molecular characteristics that underlie the observed peak position and profile of the nominal 6.2 micron interstellar emission band generally attributed to the CC stretching vibrations of polycyclic aromatic hydrocarbons (PAHs). It begins with a summary of recent experimental and theoretical studies ofthe spectroscopic properties of large (>30 carbon atoms) PAH cations as they relate to this aspect of the astrophysical problem. It then continues with an examination of the spectroscopic properties of a number of PAH variants within the context of the interstellar 6.2 micron emission, beginning with a class of compounds known as polycyclic aromatic nitrogen heterocycles (PANHs; PAHs with one or more nitrogen atoms substituted into their carbon skeleton). In this regard, we summarize the results of recent relevant experimental studies involving a limited set of small PANHs and their cations and then report the results of a comprehensive computational study that extends that work to larger PANH cations including many nitrogen-substituted variants of coronene(+) (C24H12(+)), ovalene(+) (C32H14(+)), circumcoronene(+) (C54H18(+)), and circum-circumcoronene(+) (C96H24(+)). Finally, we report the results of more focused computational studies of selected representatives from a number of other classes of PAH variants that share one or more of the key attributes of the PANH species studied. These alternative classes of PAH variants include (1) oxygen- and silicon-substituted PAH cations; (2) PAH-metal ion complexes (metallocenes) involving the cosmically abundant elements magnesium and iron; and (3) large, asymmetric PAH cations. Overall, the studies reported here demonstrate that increasing PAH size alone is insuEcient to account for the position of the shortest wavelength interstellar 6.2 micron emission bands, as had been suggested by earlier studies. On the other hand, this work reveals that substitution of one or

  3. Transformation of aromatic hydrocarbons over isomorphously substituted UTL: Comparison with large and medium pore zeolites

    Czech Academy of Sciences Publication Activity Database

    Žilková, Naděžda; Shamzhy, Mariya; Shvets, O. V.; Čejka, Jiří

    2013-01-01

    Roč. 204, APR 2013 (2013), s. 22-29 ISSN 0920-5861 R&D Projects: GA ČR(CZ) GAP106/12/0189 Institutional support: RVO:61388955 Keywords : UTL zeolite * Iso morphous substitution * Toluene alkylation with iso propyl alcohol Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.309, year: 2013

  4. Structure-activity relationships for novel drug precursor N-substituted-6-acylbenzothiazolon derivatives: A theoretical approach

    Science.gov (United States)

    Sıdır, Yadigar Gülseven; Sıdır, İsa

    2013-08-01

    In this study, the twelve new modeled N-substituted-6-acylbenzothiazolon derivatives having analgesic analog structure have been investigated by quantum chemical methods using a lot of electronic parameters and structure-activity properties; such as molecular polarizability (α), dipole moment (μ), EHOMO, ELUMO, q-, qH+, molecular volume (Vm), ionization potential (IP), electron affinity (EA), electronegativity (χ), molecular hardness (η), molecular softness (S), electrophilic index (ω), heat of formation (HOF), molar refractivity (MR), octanol-water partition coefficient (log P), thermochemical properties (entropy (S), capacity of heat (Cv)); as to investigate activity relationships with molecular structure. The correlations of log P with Vm, MR, ω, EA, EHOMO - ELUMO (ΔE), HOF in aqueous phase, χ, μ, S, η parameters, respectively are obtained, while the linear relation of log P with IP, Cv, HOF in gas phase are not observed. The log P parameter is obtained to be depending on different properties of compounds due to their complexity.

  5. Theoretical studies of the structures and local aromaticity of conjugated polycyclic hydrocarbons using three aromatic indices

    Science.gov (United States)

    Sakai, Shogo; Kita, Yuki

    2013-07-01

    The structures and local aromaticity of some conjugated polycyclic hydrocarbons (from the butadienoid, acene, and phenylene series) are studied using ab initio MO and density functional methods. The aromaticities of the molecules are estimated using three indices: the nucleus-independent chemical shift (NICS), the harmonic oscillator model of aromaticity (HOMA), and the index of deviation from aromaticity (IDA). Assessment of the relationships between the structures and the aromatic indices shows that the IDA values correspond best to the characteristics of the conjugated polycyclic hydrocarbon structures.

  6. Reações de ortometalacão em piridinas

    Directory of Open Access Journals (Sweden)

    Souza Marcus .V. N. de

    2002-01-01

    Full Text Available In this paper we describe a powerful methodology for the regiospecific construction of polysubstituted aromatic and heteroaromatic compounds. The DoM reaction (direct ortho-metalation comprises the deprotonation in position ortho of a aromatic or heteroaromatic containing DMG (directed metalation group by strong bases, normally an alkyllithium reagent, leading to an ortho-lithiated species. These species, upon treatment with electrophilic reagents, gives 1,2 disubstituted products.

  7. Cyano-containing ionic liquids for the extraction of aromatic hydrocarbons from an aromatic/aliphatic mixture

    NARCIS (Netherlands)

    Meindersma, G.W.; Haan, de A.B.

    2012-01-01

    Ionic liquids can replace conventional solvents in aromatic/aliphatic extractions, if they have higher aromatic distribution coefficients and higher or similar aromatic/aliphatic selectivities. Also physical properties, such as density and viscosity, must be taken into account if a solvent is

  8. Tissue sensitivity of the rat upper and lower extrapulmonary airways to the inhaled electrophilic air pollutants diacetyl and acrolein.

    Science.gov (United States)

    Cichocki, Joseph A; Smith, Gregory J; Morris, John B

    2014-11-01

    The target site for inhaled vapor-induced injury often differs in mouth-breathing humans compared with nose-breathing rats, thus complicating the use of rat inhalation toxicity data for assessment of human risk. We sought to examine sensitivity of respiratory/transitional nasal (RTM) and tracheobronchial (TBM) mucosa to two electrophilic irritant vapors: diacetyl and acrolein. Computational fluid dynamic physiologically based pharmacokinetic modeling was coupled with biomarker assessment to establish delivered dose-response relationships in RTM and TBM in male F344 rats following 6 h exposure to diacetyl or acrolein. Biomarkers included glutathione status, proinflammatory and antioxidant gene mRNA levels, and nuclear translocation of nuclear factor (erythroid-derived 2)-like 2 (Nrf2). Modeling revealed that 0.0094-0.1653 μg acrolein/min-cm(2) and 3.9-21.6 μg diacetyl/min-cm(2) were deposited into RTM/TBM. Results indicate RTM and TBM were generally of similar sensitivity to diacetyl and acrolein. For instance, both tissues displayed induction of antioxidant and proinflammatory genes, and nuclear accumulation of Nrf2 after electrophile exposure. Hierarchical cellular response patterns were similar in RTM and TBM but differed between vapors. Specifically, diacetyl exposure induced proinflammatory and antioxidant genes concomitantly at low exposure levels, whereas acrolein induced antioxidant genes at much lower exposure levels than that required to induce proinflammatory genes. Generally, diacetyl was less potent than acrolein, as measured by maximal induction of transcripts. In conclusion, the upper and lower extrapulmonary airways are of similar sensitivity to inhaled electrophilic vapors. Dosimetrically based extrapolation of nasal responses in nose-breathing rodents may provide an approach to predict risk to the lower airways of humans during mouth-breathing. © The Author 2014. Published by Oxford University Press on behalf of the Society of Toxicology. All

  9. The Role of Human Aldo-Keto Reductases (AKRs in the Metabolic Activation and Detoxication of Polycyclic Aromatic Hydrocarbons: Interconversion of PAH-catechols and PAH o-Quinones

    Directory of Open Access Journals (Sweden)

    Li eZhang

    2012-11-01

    Full Text Available Polycyclic aromatic hydrocarbons (PAH are ubiquitous environmental pollutants. They are procarcinogens requiring metabolic activation to elicit their deleterious effects. Aldo-keto reductases (AKR catalyze the oxidation of proximate carcinogenic PAH trans-dihydrodiols to yield electrophilic and redox-active PAH o-quiniones. AKRs are also found to be capable of reducing PAH o-quinones to form PAH catechols. The interconversion of o-quinones and catechols results in the redox cycling of PAH o-quinones to give rise to the generation of reactive oxygen species and subsequent oxidative DNA damage. On the other hand, PAH catechols can be intercepted through phase II metabolism by which PAH o-quinones could be detoxified and eliminated. The aim of the present review is to summarize the role of human AKRs in the metabolic activation/detoxication of PAH and the relevance of phase II conjugation reactions to human lung carcinogenesis.

  10. Development of a extensor oil with low content of polycyclic aromatic; Desenvolvimento de oleo extensor com baixo teor de policiclicos aromaticos

    Energy Technology Data Exchange (ETDEWEB)

    Lima, Anie Daniela M.; Fontes, Anita Eleonora F.; Figueiredo, Joao Baptista [PETROBRAS, Rio de Janeiro, RJ (Brazil)] (and others)

    2008-07-01

    This paper presents the development of a substitute product for the aromatic oil used in rubber tires. The new oil must be in according to The European Community Directive 2005/69/EC, which has the start date in January first of 2010. The directive sets limits for specific levels of polyaromatics content in the oils for rubber tires because of the mutagenic and harmful to the reproduction characteristic of some of these substances. The process of aromatics extraction was conducted on several kinds of feedstocks to obtain a product with kinematic viscosity at 100 deg C in the 40-50 cSt range and polycyclics aromatics content until 3% in mass. It is important to know that the current oils have 20% in mass of polyaromatics content. The product developed is in according with the Directive specifications and contributes to the production of tires more suitable to the environment and human health. (author)

  11. Bacterial Degradation of Aromatic Compounds

    Directory of Open Access Journals (Sweden)

    Qing X. Li

    2009-01-01

    Full Text Available Aromatic compounds are among the most prevalent and persistent pollutants in the environment. Petroleum-contaminated soil and sediment commonly contain a mixture of polycyclic aromatic hydrocarbons (PAHs and heterocyclic aromatics. Aromatics derived from industrial activities often have functional groups such as alkyls, halogens and nitro groups. Biodegradation is a major mechanism of removal of organic pollutants from a contaminated site. This review focuses on bacterial degradation pathways of selected aromatic compounds. Catabolic pathways of naphthalene, fluorene, phenanthrene, fluoranthene, pyrene, and benzo[a]pyrene are described in detail. Bacterial catabolism of the heterocycles dibenzofuran, carbazole, dibenzothiophene, and dibenzodioxin is discussed. Bacterial catabolism of alkylated PAHs is summarized, followed by a brief discussion of proteomics and metabolomics as powerful tools for elucidation of biodegradation mechanisms.

  12. Aromater i drikkevand

    DEFF Research Database (Denmark)

    Nyeland, B. A.; Hansen, A. B.

    DMU har den 10. Juni 1997 afholdt en præstationsprøvning: Aromater i drikkevand. Der deltog 21 laboratorier i præstationsprøvningen. Prøvningen omfattede 6 vandige prøver og 6 ampuller indeholdende 6 aromater. Laboratorierne spikede de tilsendte vandprøver med indholdet fra ampullerne...

  13. Fluorescence method for enzyme analysis which couples aromatic amines with aromatic aldehydes

    Science.gov (United States)

    Smith, R.E.; Dolbeare, F.A.

    1980-10-21

    Analysis of proteinases is accomplished using conventional amino acid containing aromatic amine substrates. Aromatic amines such as 4-methoxy-2-naphthylamine (4M2NA), 2-naphthylamine, aminoisophthalic acid dimethyl ester, p-nitroaniline, 4-methoxy-1-aminofluorene and coumarin derivatives resulting from enzymatic hydrolysis of the substrate couples with aromatic aldehydes such as 5-nitrosalicylaldehyde (5-NSA), benzaldehyde and p-nitrobenzaldehyde to produce Schiff-base complexes which are water insoluble. Certain Schiff-base complexes produce a shift from blue to orange-red (visible) fluorescence. Such complexes are useful in the assay of enzymes. No Drawings

  14. A unifying paradigm for naphthoquinone-based meroterpenoid (bio)synthesis

    Science.gov (United States)

    Miles, Zachary D.; Diethelm, Stefan; Pepper, Henry P.; Huang, David M.; George, Jonathan H.; Moore, Bradley S.

    2017-12-01

    Bacterial meroterpenoids constitute an important class of natural products with diverse biological properties and therapeutic potential. The biosynthetic logic for their production is unknown and defies explanation via classical biochemical paradigms. A large subgroup of naphthoquinone-based meroterpenoids exhibits a substitution pattern of the polyketide-derived aromatic core that seemingly contradicts the established reactivity pattern of polyketide phenol nucleophiles and terpene diphosphate electrophiles. We report the discovery of a hitherto unprecedented enzyme-promoted α-hydroxyketone rearrangement catalysed by vanadium-dependent haloperoxidases to account for these discrepancies in the merochlorin and napyradiomycin class of meroterpenoid antibiotics, and we demonstrate that the α-hydroxyketone rearrangement is potentially a conserved biosynthetic reaction in this molecular class. The biosynthetic α-hydroxyketone rearrangement was applied in a concise total synthesis of naphthomevalin, a prominent member of the napyradiomycin meroterpenes, and sheds further light on the mechanism of this unifying enzymatic transformation.

  15. Catalytic hydrodeoxygenation of methyl-substituted phenols: correlations of kinetic parameters with molecular properties.

    Science.gov (United States)

    Massoth, F E; Politzer, P; Concha, M C; Murray, J S; Jakowski, J; Simons, Jack

    2006-07-27

    The hydrodeoxygenation of methyl-substituted phenols was carried out in a flow microreactor at 300 degrees C and 2.85 MPa hydrogen pressure over a sulfided CoMo/Al(2)O(3) catalyst. The primary reaction products were methyl-substituted benzene, cyclohexene, cyclohexane, and H(2)O. Analysis of the results suggests that two independent reaction paths are operative, one leading to aromatics and the other to partially or completely hydrogenated cyclohexanes. The reaction data were analyzed using Langmuir-Hinshelwood kinetics to extract the values of the reactant-to-catalyst adsorption constant and of the rate constants characterizing the two reaction paths. The adsorption constant was found to be the same for both reactions, suggesting that a single catalytic site center is operative in both reactions. Ab initio electronic structure calculations were used to evaluate the electrostatic potentials and valence orbital ionization potentials for all of the substituted phenol reactants. Correlations were observed between (a) the adsorption constant and the two reaction rate constants measured for various methyl-substitutions and (b) certain moments of the electrostatic potentials and certain orbitals' ionization potentials of the isolated phenol molecules. On the basis of these correlations to intrinsic reactant-molecule properties, a reaction mechanism is proposed for each pathway, and it is suggested that the dependencies of adsorption and reaction rates upon methyl-group substitution are a result of the substituents' effects on the electrostatic potential and orbitals rather than geometric (steric) effects.

  16. Porphyrins Fused with Unactivated Polycyclic Aromatic Hydrocarbons

    KAUST Repository

    Diev, Vyacheslav V.; Schlenker, Cody W.; Hanson, Kenneth; Zhong, Qiwen; Zimmerman, Jeramy D.; Forrest, Stephen R.; Thompson, Mark E.

    2012-01-01

    A systematic study of the preparation of porphyrins with extended conjugation by meso,β-fusion with polycyclic aromatic hydrocarbons (PAHs) is reported. The meso-positions of 5,15-unsubstituted porphyrins were readily functionalized with PAHs. Ring fusion using standard Scholl reaction conditions (FeCl 3, dichloromethane) occurs for perylene-substituted porphyrins to give a porphyrin β,meso annulated with perylene rings (0.7:1 ratio of syn and anti isomers). The naphthalene, pyrene, and coronene derivatives do not react under Scholl conditions but are fused using thermal cyclodehydrogenation at high temperatures, giving mixtures of syn and anti isomers of the meso,β-fused porphyrins. For pyrenyl-substituted porphyrins, a thermal method gives synthetically acceptable yields (>30%). Absorption spectra of the fused porphyrins undergo a progressive bathochromic shift in a series of naphthyl (λ max = 730 nm), coronenyl (λ max = 780 nm), pyrenyl (λ max = 815 nm), and perylenyl (λ max = 900 nm) annulated porphyrins. Despite being conjugated with unsubstituted fused PAHs, the β,meso-fused porphyrins are more soluble and processable than the parent nonfused precursors. Pyrenyl-fused porphyrins exhibit strong fluorescence in the near-infrared (NIR) spectral region, with a progressive improvement in luminescent efficiency (up to 13% with λ max = 829 nm) with increasing degree of fusion. Fused pyrenyl-porphyrins have been used as broadband absorption donor materials in photovoltaic cells, leading to devices that show comparatively high photovoltaic efficiencies. © 2011 American Chemical Society.

  17. Porphyrins Fused with Unactivated Polycyclic Aromatic Hydrocarbons

    KAUST Repository

    Diev, Vyacheslav V.

    2012-01-06

    A systematic study of the preparation of porphyrins with extended conjugation by meso,β-fusion with polycyclic aromatic hydrocarbons (PAHs) is reported. The meso-positions of 5,15-unsubstituted porphyrins were readily functionalized with PAHs. Ring fusion using standard Scholl reaction conditions (FeCl 3, dichloromethane) occurs for perylene-substituted porphyrins to give a porphyrin β,meso annulated with perylene rings (0.7:1 ratio of syn and anti isomers). The naphthalene, pyrene, and coronene derivatives do not react under Scholl conditions but are fused using thermal cyclodehydrogenation at high temperatures, giving mixtures of syn and anti isomers of the meso,β-fused porphyrins. For pyrenyl-substituted porphyrins, a thermal method gives synthetically acceptable yields (>30%). Absorption spectra of the fused porphyrins undergo a progressive bathochromic shift in a series of naphthyl (λ max = 730 nm), coronenyl (λ max = 780 nm), pyrenyl (λ max = 815 nm), and perylenyl (λ max = 900 nm) annulated porphyrins. Despite being conjugated with unsubstituted fused PAHs, the β,meso-fused porphyrins are more soluble and processable than the parent nonfused precursors. Pyrenyl-fused porphyrins exhibit strong fluorescence in the near-infrared (NIR) spectral region, with a progressive improvement in luminescent efficiency (up to 13% with λ max = 829 nm) with increasing degree of fusion. Fused pyrenyl-porphyrins have been used as broadband absorption donor materials in photovoltaic cells, leading to devices that show comparatively high photovoltaic efficiencies. © 2011 American Chemical Society.

  18. Hydroamination reactions of alkynes with ortho-substituted anilines in ball mills: synthesis of benzannulated N-heterocycles by a cascade reaction.

    Science.gov (United States)

    Weiße, Maik; Zille, Markus; Jacob, Katharina; Schmidt, Robert; Stolle, Achim

    2015-04-20

    It was demonstrated that ortho-substituted anilines are prone to undergo hydroamination reactions with diethyl acetylenedicarboxylate in a planetary ball mill. A sequential coupling of the intermolecular hydroamination reaction with intramolecular ring closure was utilized for the syntheses of benzooxazines, quinoxalines, and benzothiazines from readily available building blocks, that is, electrophilic alkynes and anilines with OH, NH, or SH groups in the ortho position. For the heterocycle formation, it was shown that several stress conditions were able to initiate the reaction in the solid state. Processing in a ball mill seemed to be advantageous over comminution with mortar and pestle with respect to process control. In the latter case, significant postreaction modification occurred during solid-state analysis. Cryogenic milling proved to have an adverse effect on the molecular transformation of the reagents. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Synthesis, Leishmanicidal Activity and Theoretical Evaluations of a Series of Substituted bis-2-Hydroxy-1,4-Naphthoquinones

    Directory of Open Access Journals (Sweden)

    Morgana V. de Araújo

    2014-09-01

    Full Text Available A series of eight substituted bis-2-hydroxy-1,4-naphthoquinone derivatives was synthesized through lawsone condensation with various aromatic and aliphatic aldehydes under mild acidic conditions. The title compounds were evaluated for antileishmanial activity in vitro against Leishmania amazonensis and Leishmania braziliensis promastigotes; six compounds showed good activity without significant toxic effects. The compound with the highest activity was used for an in vivo assay with Leishmania amazonensis.

  20. Noncomparative scaling of aromaticity through electron itinerancy

    International Nuclear Information System (INIS)

    Paul, Satadal; Goswami, Tamal; Misra, Anirban

    2015-01-01

    Aromaticity is a multidimensional concept and not a directly observable. These facts have always stood in the way of developing an appropriate theoretical framework for scaling of aromaticity. In the present work, a quantitative account of aromaticity is developed on the basis of cyclic delocalization of π-electrons, which is the phenomenon leading to unique features of aromatic molecules. The stabilization in molecular energy, caused by delocalization of π-electrons is obtained as a second order perturbation energy for archetypal aromatic systems. The final expression parameterizes the aromatic stabilization energy in terms of atom to atom charge transfer integral, onsite repulsion energy and the population of spin orbitals at each site in the delocalized π-electrons. An appropriate computational platform is framed to compute each and individual parameter in the derived equation. The numerical values of aromatic stabilization energies obtained for various aromatic molecules are found to be in close agreement with available theoretical and experimental reports. Thus the reliable estimate of aromaticity through the proposed formalism renders it as a useful tool for the direct assessment of aromaticity, which has been a long standing problem in chemistry

  1. Three-dimensional aromatic networks.

    Science.gov (United States)

    Toyota, Shinji; Iwanaga, Tetsuo

    2014-01-01

    Three-dimensional (3D) networks consisting of aromatic units and linkers are reviewed from various aspects. To understand principles for the construction of such compounds, we generalize the roles of building units, the synthetic approaches, and the classification of networks. As fundamental compounds, cyclophanes with large aromatic units and aromatic macrocycles with linear acetylene linkers are highlighted in terms of transannular interactions between aromatic units, conformational preference, and resolution of chiral derivatives. Polycyclic cage compounds are constructed from building units by linkages via covalent bonds, metal-coordination bonds, or hydrogen bonds. Large cage networks often include a wide range of guest species in their cavity to afford novel inclusion compounds. Topological isomers consisting of two or more macrocycles are formed by cyclization of preorganized species. Some complicated topological networks are constructed by self-assembly of simple building units.

  2. Vapor pressures and sublimation enthalpies of seven heteroatomic aromatic hydrocarbons measured using the Knudsen effusion technique

    International Nuclear Information System (INIS)

    Goldfarb, Jillian L.; Suuberg, Eric M.

    2010-01-01

    The vapor pressures of seven heteroatom-containing cyclic aromatic hydrocarbons, ranging in molecular weight from (168.19 to 208.21) g . mol -1 were measured over the temperature range of (301 to 486) K using the isothermal Knudsen effusion technique. The compounds measured include: anthraquinone, 9-fluorenone, 9-fluorenone oxime, phenoxazine, phenoxathiin, and 9H-pyrido[3,4-b]indole. These solid-state sublimation measurements provided values that are compared to vapor pressures of parent aromatic compounds (anthracene and fluorene) and to others with substituent groups in order to examine the effects of alcohol, ketone, pyridine, and pyrrole functionality on this property. The enthalpies and entropies of sublimation for each compound were determined from the Clausius-Clapeyron equation. Though there is no consistent trend in terms of the effects of substitutions on changes in the enthalpy or entropy of sublimation, we note that the prevalence of enthalpic or entropic driving forces on vapor pressure depend on molecule-specific factors and not merely molecular weight of the substituents.

  3. Sulfonate activation of the electrophilic reactivity of chlorine and alkyl hypochlorides by the insertion of sulfur trioxide at the C1-C1 and O-C1 bonds. Addition of chlorine chloro- and ethoxysulfate to olefins

    International Nuclear Information System (INIS)

    Zefirov, N.S.; Koz'min, A.S.; Sorokin, V.D.; Zhdankin, V.V.

    1986-01-01

    At low temperatures (-40 to -80 0 C) sulfur trioxide enters the chlorine molecule (with the formation of chlorine chlorosulfate) and the ethyl hypochlorite molecule (giving chlorine ethoxysulfate). Both new compounds are highly reactive electrophilic chlorinating reagents and add to ethylene, activated alkenes (1-hexene and cyclohexene), and deactivated olefins (methyl methacrylate, tri- and tetrachloroethylene) in methylene chloride solution at low temperatures. The addition of chlorine chlorosulfate leads to the formation of β-chloroalkyl chlorosulfates with yields of 24-85%, and the addition of chlorine ethoxysulfate leads to β-chloroalkyl ethylsulfates with yields of 65-85%. The reactions with unsymmetrical olefins lead to mixtures of the regioisomers with a preference for the products from addition according to the Markovnikov rule; the addition to cyclohexene is trans-stereospecific. The investigated processes represent a new simple approach to the production of sulfate-activated chlorinating reagents and extend the possibilities for functional substitution of olefins

  4. A facile synthesis of substituted 2-alkylquinolines through [3+3] annulation between 3-ethoxycyclobutanones and aromatic amines at room temperature.

    Science.gov (United States)

    Shan, Gang; Sun, Xiuyun; Xia, Qian; Rao, Yu

    2011-11-04

    An efficient single-step approach toward the synthesis of 2-alkylquinolines is described. Through a Lewis acid mediated [3+3] annulation reaction between 3-ethoxycyclobutanones and aromatic amines, a variety of multisubstituted 2-alkylquinoline derivatives were prepared regioselectively at room temperature. © 2011 American Chemical Society

  5. Superoxide radical-mediated photocatalytic oxidation of phenolic compounds over Ag"+/TiO_2: Influence of electron donating and withdrawing substituents

    International Nuclear Information System (INIS)

    Xiao, Jiadong; Xie, Yongbing; Han, Qingzhen; Cao, Hongbin; Wang, Yujiao; Nawaz, Faheem; Duan, Feng

    2016-01-01

    Highlights: • A weak EWG benefited photocatalytic oxidation of phenols the most. • Phenolic compounds were dominantly oxidized by ·O_2"−, rather than ·OH, "1O_2 or h"+. • ·O_2"− preferred to nucleophilically attack EDG substituted phenols. • ·O_2"− more likely electrophilically attacked EWG substituted phenols. • ·O_2"− simultaneously nucleophilically and electrophilically assaulted p-chlorophenol. - Abstract: A comparative study was constructed to correlate the electronic property of the substituents with the degradation rates of phenolic compounds and their oxidation pathways under UV with Ag"+/TiO_2 suspensions. It was verified that a weak electron withdrawing substituent benefited photocatalytic oxidation the most, while an adverse impact appeared when a substituent was present with stronger electron donating or withdrawing ability. The addition of p-benzoquinone dramatically blocked the degradation, confirming superoxide radicals (·O_2"−) as the dominant photooxidant, rather than hydroxyl radicals, singlet oxygen or positive holes, which was also independent of the substituent. Hammett relationship was established based on pseudo-first-order reaction kinetics, and it revealed two disparate reaction patterns between ·O_2"− and phenolic compounds, which was further verified by the quantum chemical computation on the frontier molecular orbitals and Mulliken charge distributions of ·O_2"− and phenolic compounds. It was found that electron donating group (EDG) substituted phenols were more likely nucleophilically attacked by ·O_2"−, while ·O_2"− preferred to electrophilically assault electron withdrawing group (EWG) substituted phenols. Exceptionally, electrophilic and nucleophilic attack by ·O_2"− could simultaneously occur in p-chlorophenol degradation, consequently leading to its highest rate constant. Possible reactive positions on the phenolic compounds were also detailedly uncovered.

  6. Rotationally cooled laser induced fluorescence determination of polycyclic aromatic hydrocarbons

    International Nuclear Information System (INIS)

    Warren, J.A.; Hayes, J.M.; Small, G.J.

    1982-01-01

    In recent years the development of new highly selective and sensitive methods for the characterization and determination of polycyclic aromatic hydrocarbons (PAHs) and their derivatives in complex mixtures has received considerable attention. High selectivity is associated here with the ability to distinguish between substitutional isomers of PAHs. Attainment of this selectivity with capillary column-gas chromatography-mass spectrometry for complex mixtures is very difficult and time-consuming. Alternative approaches are, therefore, required. Given that the majority of PAHs fluoresce with reasonable quantum yields and that high sensitivities are afforded by fluorescence detection, the possibility of developing high-resolution fluorescence based techniques is attractive. This is all the more so if the technique's selectivity does not rely on physical separation, e.g., chromatography. In this paper discussion is limited to such techniques

  7. Basic deuteroexchange in transition metal complexes with nitrogen-containing aromatic heterocycles

    International Nuclear Information System (INIS)

    Tupitsyn, I.F.

    1986-01-01

    Kinetics of deuteroexchange in the methyl group of nitrate complexes of a metal - nickel (2) - with different methyl-substituted aromatic heterocycles and isostructural complexes of a ligand - 2 - methyl quinoline - with different central metal atoms (Mn(2), Ni(2), Cu(2), Zn(2)) is studied. Series for influence of ligand structure on deuteroexchange rate in complexes doesn't correspond qualitatively to series for deuteroexchange rate increase in noncoordinated ligands. Deuteroexchange rate is weakly subjected to influence of exchange in metal-complexing agent. Deuteroexchange mechanism is suggested and discussed. According to this mechanism the structure developed in the course of the exchange process with electron density transfer from the heterocyclic ligand to a metal ion is a transition state of the reaction

  8. Regioselective aromatic substitution reactions of cyclometalated Ir(III) complexes: synthesis and photochemical properties of substituted Ir(III) complexes that exhibit blue, green, and red color luminescence emission.

    Science.gov (United States)

    Aoki, Shin; Matsuo, Yasuki; Ogura, Shiori; Ohwada, Hiroki; Hisamatsu, Yosuke; Moromizato, Shinsuke; Shiro, Motoo; Kitamura, Masanori

    2011-02-07

    In this manuscript, the regioselective halogenation, nitration, formylation, and acylation of Ir(tpy)(3) and Ir(ppy)(3) (tpy = 2-(4'-tolyl)pyridine and ppy = 2-phenylpyridine) and the subsequent conversions are described. During attempted bromination of the three methyl groups in fac-Ir(tpy)(3) using N-bromosuccinimide (NBS) and benzoyl peroxide (BPO), three protons at the 5'-position (p-position with respect to the C-Ir bond) of phenyl rings in tpy units were substituted by Br, as confirmed by (1)H NMR spectra, mass spectra, and X-ray crystal structure analysis. It is suggested that such substitution reactions of Ir complexes proceed via an ionic mechanism rather than a radical mechanism. UV-vis and luminescence spectra of the substituted Ir(III) complexes are reported. The introduction of electron-withdrawing groups such as CN and CHO groups at the 5'-position of tpy induces a blue shift of luminescence emission to about 480 nm, and the introduction of electron-donating groups such as an amino group results in a red shift to about 600 nm. A reversible change of emission for the 5'-amino derivative of Ir(tpy)(3), Ir(atpy)(3), between red and green occurs upon protonation and deprotonation.

  9. Synthesis of deuterium-labeled analogs of the lipid hydroperoxide-derived bifunctional electrophile 4-oxo-2(E)-nonenal.

    Science.gov (United States)

    Arora, Jasbir S; Oe, Tomoyuki; Blair, Ian A

    2011-05-15

    Lipid hydroperoxides undergo homolytic decomposition into the bifunctional 4-hydroxy-2( E )-nonenal and 4-oxo-2( E )-nonenal (ONE). These bifunctional electrophiles are highly reactive and can readily modify intracellular molecules including glutathione (GSH), deoxyribonucleic acid (DNA) and proteins. Lipid hydroperoxide-derived bifunctional electrophiles are thought to contribute to the pathogenesis of a number of diseases. ONE is an α , β -unsaturated aldehyde that can react in multiple ways and with glutathione, proteins and DNA. Heavy isotope-labeled analogs of ONE are not readily available for conducting mechanistic studies or for use as internal standards in mass spectrometry (MS)-based assays. An efficient onestep cost-effective method has been developed for the preparation of C-9 deuterium-labeled ONE. In addition, a method for specific deuterium labeling of ONE at C-2, C-3 or both C-2 and C-3 has been developed. This latter method involved the selective reduction of an intermediate alkyne either by lithium aluminum hydride or lithium aluminum deuteride and quenching with water or deuterium oxide. The availability of these heavy isotope analogs will be useful as internal standards for quantitative studies employing MS and for conducting mechanistic studies of complex interactions between ONE and DNA bases as well as between ONE and proximal amino acid residues in peptides and proteins.

  10. Regularities of synthesis and mechanism of polycondensation of aromatic amines

    International Nuclear Information System (INIS)

    Matnishyan, Hagob

    2002-01-01

    Full text.Aniline polymers and its derivatives are widely used in modern electronics, electrical engineering and manufacturing of various appliances. They are used for production of electrical power sources, probes and sensors, composite materials absorbing high frequency radiations, anticorrosion coatings, nonlinear optical devices-such as lasers, cathode ray tubes, photodiodes etc. Such a wide usage of aromatic amine polymers brings up new demands to their structure and properties, which is dependent on conditions of synthesis and forming of the hard phase. The presented article describes regularities and mechanisms of oxidative polycondensation of aromatic amines. Several types of polymers have been synthesized by chemical and electrochemical oxidation of aniline and its chlor-, brom-, iodo-, nitro-, p-substituted derivatives; diphenylamine, benzidine and phenylenediamines in nonwater media. On the basis of kinetic and electrochemical studies and literature analysis we suggested a mechanism of polycondensation of aromatic amines. According to it, oxidation of amines starts with the electron transfer with cation-radical formation on the first stage, which stabilizes in acid environments due to complex formation with initial amine. Dimer formation and further growth of chain takes place upon another electron transfer from formed complex, which results in forming of macromolecules. We also suggested a scheme for obtaining of structures defect in media assisting in deprotonizing of cation radicals and formation of arylamine radical centers. Those processes lead to formation of azo- and diphenyl fragments in the main chain of the polymer and predetermine the possibility of chain disruption. We also considered reactions leading to formation of branched polymers and cyclic structures, such as phenazine in particular. The peculiarity of electrochemical process lies in regulation of concentration of active centres on the positive electrode surface

  11. Tailoring highly conductive graphene nanoribbons from small polycyclic aromatic hydrocarbons: a computational study.

    Science.gov (United States)

    Bilić, A; Sanvito, S

    2013-07-10

    Pyrene, the smallest two-dimensional mesh of aromatic rings, with various terminal thiol substitutions, has been considered as a potential molecular interconnect. Charge transport through two terminal devices has been modeled using density functional theory (with and without self interaction correction) and the non-equilibrium Green's function method. A tetra-substituted pyrene, with dual thiol terminal groups at opposite ends, has been identified as an excellent candidate, owing to its high conductance, virtually independent of bias voltage. The two possible extensions of its motif generate two series of graphene nanoribbons, with zigzag and armchair edges and with semimetallic and semiconducting electron band structure, respectively. The effects related to the wire length and the bias voltage on the charge transport have been investigated for both sets. The conductance of the nanoribbons with a zigzag edge does not show either length or voltage dependence, owing to an almost perfect electron transmission with a continuum of conducting channels. In contrast, for the armchair nanoribbons a slow exponential attenuation of the conductance with the length has been found, due to their semiconducting nature.

  12. Pyridine-substituted thiazolylphenol derivatives: Synthesis, modeling studies, aromatase inhibition, and antiproliferative activity evaluation.

    Science.gov (United States)

    Ertas, Merve; Sahin, Zafer; Berk, Barkin; Yurttas, Leyla; Biltekin, Sevde N; Demirayak, Seref

    2018-04-01

    Drugs used in breast cancer treatments target the suppression of estrogen biosynthesis. During this suppression, the main goal is to inhibit the aromatase enzyme that is responsible for the cyclization and structuring of estrogens either with steroid or non-steroidal-type inhibitors. Non-steroidal derivatives generally have a planar aromatic structure attached to the triazole ring system in their structures, which inhibits hydroxylation reactions during aromatization by coordinating the heme group. Bioisosteric replacement of the triazole ring system and development of aromatic/cyclic structures of the side chain can increase the selectivity for aromatase enzyme inhibition. In this study, pyridine-substituted thiazolylphenol derivatives, which are non-steroidal triazole bioisosteres, were synthesized using the Hantzsch method, and physical analysis and structural determination studies were performed. The IC 50 values of the compounds were determined by a fluorescence-based aromatase inhibition assay. Then, their antiproliferative activities on the MCF7 and HEK 293 cell lines were evaluated with the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Furthermore, the crystal structure of human placental aromatase was subjected to a series of docking experiments to identify the possible interactions between the most active structure and the active site. Lastly, an in silico technique was performed to analyze and predict the drug-likeness, molecular and ADME properties of the synthesized molecules. © 2018 Deutsche Pharmazeutische Gesellschaft.

  13. Strong CH/O interactions between polycyclic aromatic hydrocarbons and water: Influence of aromatic system size.

    Science.gov (United States)

    Veljković, Dušan Ž

    2018-03-01

    Energies of CH/O interactions between water molecule and polycyclic aromatic hydrocarbons with a different number of aromatic rings were calculated using ab initio calculations at MP2/cc-PVTZ level. Results show that an additional aromatic ring in structure of polycyclic aromatic hydrocarbons significantly strengthens CH/O interactions. Calculated interaction energies in optimized structures of the most stable tetracene/water complex is -2.27 kcal/mol, anthracene/water is -2.13 kcal/mol and naphthalene/water is -1.97 kcal/mol. These interactions are stronger than CH/O contacts in benzene/water complex (-1.44 kcal/mol) while CH/O contacts in tetracene/water complex are even stronger than CH/O contacts in pyridine/water complexes (-2.21 kcal/mol). Electrostatic potential maps for different polycyclic aromatic hydrocarbons were calculated and used to explain trends in the energies of interactions. Copyright © 2017 Elsevier Inc. All rights reserved.

  14. Newly constructed stable reporter cell lines for mechanistic studies on electrophile-responsive element-mediated gene expression reveal a role for flavonoid planarity.

    NARCIS (Netherlands)

    Boerboom, A.M.A.; Vermeulen, M.; Woude, H. van der; Bremer, B.I.; Lee-Hilz, Y.Y.; Kampman, E.; Bladeren, P.J. van; Rietjens, I.M.C.M.; Aarts, J.

    2006-01-01

    The electrophile-responsive element (EpRE) is a transcriptional enhancer involved in cancer-chemoprotective gene expression modulation by certain food components. Two stably transfected luciferase reporter cell lines were developed, EpRE(hNQO1)-LUX and EpRE(mGST-Ya)-LUX, based on EpRE sequences from

  15. Newly constructed stable reporter cell lines for mechanistic studies on electrophile-responsive element-mediated gene expression reveal a role for flavonoid planarity

    NARCIS (Netherlands)

    Boerboom, A.M.J.F.; Vermeulen, M.; Woude, H. van der; Bremer, B.I.; Lee-Hilz, Y.Y.; Kampman, E.; Bladeren, P.J. van; Rietjens, I.M.C.M.; Aarts, J.M.M.J.G.

    2006-01-01

    The electrophile-responsive element (EpRE) is a transcriptional enhancer involved in cancer-chemoprotective gene expression modulation by certain food components. Two stably transfected luciferase reporter cell lines were developed, EpRE(hNQO1)-LUX and EpRE(mGST-Ya)-LUX, based on EpRE sequences from

  16. Aromatic substitution in the gas phase. Alkylation of arenes by gaseous C4H9+ cations

    International Nuclear Information System (INIS)

    Cacace, F.; Ciranni, G.; Giacomello, P.

    1981-01-01

    Butyl cations, obtained in the dilute gas state from the radiolysis of butane in the pressure range from 70 to 750 torr, have been allowed to react with benzene, toluene, and their mixtures or with trace amounts of o-xylene in the gaseous system. The gas-phase butylation yields invariably sec-butylarenes, remarkably free of isomeric byproducts, namely n- and tert-butylarenes. Other alkylation experiments, where gaseous butyl cations from the reaction of butane with radiolytically formed H 3 + ions were used as reagent, confirmed the exclusive formation of sec-butylarenes. The butylation process displays the positional and substrate selectivity and the dependence of orientation on the pressure of the system, typical of other gas-phase ionic substitutions. At high pressures, orth-para orientation predominates in the sec-butylation of toluene, with a ortho:meta:para ratio of 43:30:27 at 715 torr. As the pressure is reduced, a gradual shift in favor of the thermodynamically most stable meta-substituted arenium ion is observed, leading to a ortho:meta:para ratio of 31:48:21 at 70 torr

  17. Synthesis and antiproliferative activity of novel limonene derivatives with a substituted thiourea moiety

    International Nuclear Information System (INIS)

    Figueiredo, Isis M.; Santos, Luciane V. dos; Costa, Willian F. da; Silva, Cleuza C. da; Sarragiotto, Maria H.; Carvalho, Joao E. de; Sacoman, Juliana L.; Kohn, Luciana K.

    2006-01-01

    A series of R-(+)-limonene derivatives bearing a substituted thiourea moiety (3-13) and five S-methyl analogs (14-18) were synthesized and evaluated for their in vitro antiproliferative activity against human cancer cell lines. Compounds bearing aromatic substituents (3-6) exhibit cytostatic activity in the full panel of cell lines tested, with GI 50 values in the range of 2.5 to 24 μmol L -1 . Compounds 3, 10, 12 and 16 were the most active with GI 5 )0 values in the range of 0.41 to 3.0 μmol L -1 , against different cell lines. (author)

  18. Combined Experimental and Theoretical Investigations on Optical Activities of Möbius Aromatic and Möbius Antiaromatic Hexaphyrin Phosphorus Complexes.

    Science.gov (United States)

    Mori, Tadashi; Tanaka, Takayuki; Higashino, Tomohiro; Yoshida, Kota; Osuka, Atsuhiro

    2016-06-23

    Intrinsically chiral Möbius aromatic [28]hexaphyrin monophosphorus(V) and Möbius antiaromatic [30]hexaphyrin bisphosphorus(V) complexes have been optically resolved and their absolute configurations (ACs) were determined by combined experimental and theoretical investigations on their circular dichroisms (CDs). First elutes in chiral HPLC exhibited strong positive Cotton effects (CEs) at the B-band, characteristic for the ML configurations in their Möbius strips. Weak CEs at the Q-band, if attainable, complemented their AC assignment. The whole CD pattern and intensity were well reproduced by time-dependent approximate coupled cluster theory using model systems that omit five outward meso-aryl substituents (inward-meso-retained model), providing a solid basis for AC assignment. The cost efficient TD-DFT method with appropriate functionals for fully substituted (nontruncated) complexes well reproduced CEs around the B-band (but less satisfactory at the Q-band), also allows the rapid AC estimation for their Möbius strips. Observed difference in CDs between aromatic and antiaromatic hexaphyrins were better interpreted by their shifts in energy levels and altered interactions of relevant molecular orbitals, rather than small differences in Möbius geometries nor aromatic/antiaromatic character, despite the correlations recently claimed in planar π-systems.

  19. Carbon-14 kinetic isotope effects and mechanisms of addition of 2,4-dinitrobenzenesulfenyl chloride to substituted styrenes-1-14C and styrenes-2-14C

    International Nuclear Information System (INIS)

    Kanska, M.; Fry, A.

    1983-01-01

    As the first reported examples of carbon isotope effects in simple electrophilic addition reactions we have measured the carbon-14 kinetic isotope effects in the addition of 2,4-dinitrobenzenesulfenyl chloride to a series of para-substituted α and β-labeled styrenes in acetic acid at 30.1 0 C: for para substituents Cl, H, and CH 3 the k/ 14 K values for α labeling are 1.027, 1.022, and 1.004, and the k/ 14 k values for β labeling are 1.035, 1.032, and 1.037, all +/-approx.0.004. The kinetics of the reaction were measured for the p-CH 3 O,p-CH 3 , unsubstituted, p-Cl, and m-NO 2 styrenes; electron-donating groups strongly accelerate the reaction, and electron-withdrawing groups retard it. The Hammett plot is curved with p + values ranging from about -4.6 at the electron-donating group (EDG) end to about -1.8 at the electron-withdrawing group (EWG) end. Both the isotope effect and kinetic data, and related data from the literature, are interpreted in terms of a changing mechanism, with the activated complexes of the rate-determining steps having much open carbenium ion (ion pair) character for EDG-substituted styrenes and much cyclic thiiranium io (ion par) character for EWG-substituted styrenes. 1 figure, 2 tables

  20. Genotoxicity risk assessment of diversely substituted quinolines using the SOS chromotest.

    Science.gov (United States)

    Duran, Leidy Tatiana Díaz; Rincón, Nathalia Olivar; Galvis, Carlos Eduardo Puerto; Kouznetsov, Vladimir V; Lorenzo, Jorge Luis Fuentes

    2015-03-01

    Quinolines are aromatic nitrogen compounds with wide therapeutic potential to treat parasitic and microbial diseases. In this study, the genotoxicity of quinoline, 4-methylquinoline, 4-nitroquinoline-1-oxide (4-NQO), and diversely functionalized quinoline derivatives and the influence of the substituents (functional groups and/or atoms) on their genotoxicity were tested using the SOS chromotest. Quinoline derivatives that induce genotoxicity by the formation of an enamine epoxide structure did not induce the SOS response in Escherichia coli PQ37 cells, with the exception of 4-methylquinoline that was weakly genotoxic. The chemical nature of the substitution (C-5 to C-8: hydroxyl, nitro, methyl, isopropyl, chlorine, fluorine, and iodine atoms; C-2: phenyl and 3,4-methylenedioxyphenyl rings) of quinoline skeleton did not significantly modify compound genotoxicities; however, C-2 substitution with α-, β-, or γ-pyridinyl groups removed 4-methylquinoline genotoxicity. On the other hand, 4-NQO derivatives whose genotoxic mechanism involves reduction of the C-4 nitro group were strong inducers of the SOS response. Methyl and nitrophenyl substituents at C-2 of 4-NQO core affected the genotoxic potency of this molecule. The relevance of these results is discussed in relation to the potential use of the substituted quinolines. The work showed the sensitivity of SOS chromotest for studying structure-genotoxicity relationships and bioassay-guided quinoline synthesis. © 2013 Wiley Periodicals, Inc.

  1. Introduction of a Simple Experiment for the Undergraduate Organic Chemistry Laboratory Demonstrating the Lewis Acid and Shape-Selective Properties of Zeolite Na-Y

    Science.gov (United States)

    Maloney, Vincent; Szczepanski, Zach

    2017-01-01

    A simple, inexpensive, discovery-based experiment for undergraduate organic laboratories has been developed that demonstrates the Lewis acid and shape-selective properties of zeolites. Calcined zeolite Na-Y promotes the electrophilic aromatic bromination of toluene with a significantly higher para/ortho ratio than observed under conventional…

  2. Converting homogeneous to heterogeneous in electrophilic catalysis using monodisperse metal nanoparticles.

    Science.gov (United States)

    Witham, Cole A; Huang, Wenyu; Tsung, Chia-Kuang; Kuhn, John N; Somorjai, Gabor A; Toste, F Dean

    2010-01-01

    A continuing goal in catalysis is to unite the advantages of homogeneous and heterogeneous catalytic processes. To this end, nanoparticles represent a new frontier in heterogeneous catalysis, where this unification can also be supplemented by the ability to obtain new or divergent reactivity and selectivity. We report a novel method for applying heterogeneous catalysts to known homogeneous catalytic reactions through the design and synthesis of electrophilic platinum nanoparticles. These nanoparticles are selectively oxidized by the hypervalent iodine species PhICl(2), and catalyse a range of π-bond activation reactions previously only catalysed through homogeneous processes. Multiple experimental methods are used to unambiguously verify the heterogeneity of the catalytic process. The discovery of treatments for nanoparticles that induce the desired homogeneous catalytic activity should lead to the further development of reactions previously inaccessible in heterogeneous catalysis. Furthermore, a size and capping agent study revealed that Pt PAMAM dendrimer-capped nanoparticles demonstrate superior activity and recyclability compared with larger, polymer-capped analogues.

  3. Converting Homogeneous to Heterogeneous in Electrophilic Catalysis using Monodisperse Metal Nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Witham, Cole A.; Huang, Wenyu; Tsung, Chia-Kuang; Kuhn, John N.; Somorjai, Gabor A.; Toste, F. Dean

    2009-10-15

    A continuing goal in catalysis is the transformation of processes from homogeneous to heterogeneous. To this end, nanoparticles represent a new frontier in heterogeneous catalysis, where this conversion is supplemented by the ability to obtain new or divergent reactivity and selectivity. We report a novel method for applying heterogeneous catalysts to known homogeneous catalytic reactions through the design and synthesis of electrophilic platinum nanoparticles. These nanoparticles are selectively oxidized by the hypervalent iodine species PhICl{sub 2}, and catalyze a range of {pi}-bond activation reactions previously only homogeneously catalyzed. Multiple experimental methods are utilized to unambiguously verify the heterogeneity of the catalytic process. The discovery of treatments for nanoparticles that induce the desired homogeneous catalytic activity should lead to the further development of reactions previously inaccessible in heterogeneous catalysis. Furthermore, our size and capping agent study revealed that Pt PAMAM dendrimer-capped nanoparticles demonstrate superior activity and recyclability compared to larger, polymer-capped analogues.

  4. Pulse shape discrimination in non-aromatic plastics

    Energy Technology Data Exchange (ETDEWEB)

    Paul Martinez, H.; Pawelczak, Iwona; Glenn, Andrew M.; Leslie Carman, M.; Zaitseva, Natalia; Payne, Stephen

    2015-01-21

    Recently it has been demonstrated that plastic scintillators have the ability to distinguish neutrons from gamma rays by way of pulse shape discrimination (PSD). This discovery has lead to new materials and new capabilities. Here we report our work with the effects of aromatic, non-aromatic, and mixed aromatic/non-aromatic matrices have on the performance of PSD plastic scintillators.

  5. Malaria parasite carbonic anhydrase: inhibition of aromatic/heterocyclic sulfonamides and its therapeutic potential

    Science.gov (United States)

    Krungkrai, Sudaratana R; Krungkrai, Jerapan

    2011-01-01

    Plasmodium falciparum (P. falciparum) is responsible for the majority of life-threatening cases of human malaria, causing 1.5-2.7 million annual deaths. The global emergence of drug-resistant malaria parasites necessitates identification and characterization of novel drug targets and their potential inhibitors. We identified the carbonic anhydrase (CA) genes in P. falciparum. The pfCA gene encodes anα-carbonic anhydrase, a Zn2+-metalloenzme, possessing catalytic properties distinct from that of the human host CA enzyme. The amino acid sequence of the pfCA enzyme is different from the analogous protozoan and human enzymes. A library of aromatic/heterocyclic sulfonamides possessing a large diversity of scaffolds were found to be very good inhibitors for the malarial enzyme at moderate-low micromolar and submicromolar inhibitions. The structure of the groups substituting the aromatic-ureido- or aromatic-azomethine fragment of the molecule and the length of the parent sulfonamide were critical parameters for the inhibitory properties of the sulfonamides. One derivative, that is, 4- (3, 4-dichlorophenylureido)thioureido-benzenesulfonamide (compound 10) was the most effective in vitro Plasmodium falciparum CA inhibitor, and was also the most effective antimalarial compound on the in vitro P. falciparum growth inhibition. The compound 10 was also effective in vivo antimalarial agent in mice infected with Plasmodium berghei, an animal model of drug testing for human malaria infection. It is therefore concluded that the sulphonamide inhibitors targeting the parasite CA may have potential for the development of novel therapies against human malaria. PMID:23569766

  6. Density functional theory studies on electronic properties of thiophene s oxides as aromatic dienophiles for reactivity prediction in diels-alder reactions

    International Nuclear Information System (INIS)

    Banjo, S.

    2013-01-01

    The reactivity of thiophene S-oxides was discussed with special emphasis on the use of thiophene S-oxides as dienophiles in Diels-Alder type reactions. The omega values obtained for thiophene S-oxide (TO) with electron-donating group (-CH/sub 3/) increased the nucleophilicity power whereas substitution with electron-withdrawing groups (such as -NO/sub 2/ and -CO/sub 2/CH/sub 2/CH/sub 3/) increased the electrophilicity power, indicating an increase of reactivity towards a nucleophiles. The higher the value of delta omega the more favourable the D-A process, therefore apart from (4+2) addition reactions of these TO as diene with the typical dienophiles like 1,2-dicyanoethene and 1,2-dicyanoethene, it could be possible for TO with strong electron withdrawing substituents to serve as dienophile, e.g. heterocycles Ie and If. Also, from the value of delta omega heterocycle 1d could involve in (4+2) addition reactions with heterocyles 1e and If. (author)

  7. Aromatic-Aromatic Interactions in Biological System: Structure Activity Relationships

    International Nuclear Information System (INIS)

    Rajagopal, Appavu; Deepa, Mohan; Govindaraju, Munisamy

    2016-01-01

    While, intramolecular hydrogen bonds have attracted the greatest attention in studies of peptide conformations, the recognition that several other weakly polar interactions may be important determinants of folded structure has been growing. Burley and Petsko provided a comprehensive overview of the importance of weakly polar interactions, in shaping protein structures. The interactions between aromatic rings, which are spatially approximate, have attracted special attention. A survey of the proximal aromatic residue pairs in proteins, allowed Burley and Petsko to suggest that, “phenyl ring centroids are separated by a preferential distance of between 4.5 and 7 Å, and dihedral angles approximately 90° are most common”

  8. Aromatic-Aromatic Interactions in Biological System: Structure Activity Relationships

    Energy Technology Data Exchange (ETDEWEB)

    Rajagopal, Appavu; Deepa, Mohan [Molecular Biophysics Unit, Indian Institute of Sciences-Bangalore, Karnataka (India); Govindaraju, Munisamy [Bio-Spatial Technology Research Unit, Department of Environmental Biotechnology, School of Environmental Sciences, Bharathidasan University, Tiruchirappalli, Tamil Nadu (India)

    2016-02-26

    While, intramolecular hydrogen bonds have attracted the greatest attention in studies of peptide conformations, the recognition that several other weakly polar interactions may be important determinants of folded structure has been growing. Burley and Petsko provided a comprehensive overview of the importance of weakly polar interactions, in shaping protein structures. The interactions between aromatic rings, which are spatially approximate, have attracted special attention. A survey of the proximal aromatic residue pairs in proteins, allowed Burley and Petsko to suggest that, “phenyl ring centroids are separated by a preferential distance of between 4.5 and 7 Å, and dihedral angles approximately 90° are most common”.

  9. Direct catalytic trifluoromethylthiolation of boronic acids and alkynes employing electrophilic shelf-stable N-(trifluoromethylthio)phthalimide.

    Science.gov (United States)

    Pluta, Roman; Nikolaienko, Pavlo; Rueping, Magnus

    2014-02-03

    A new and safe method for the synthesis of N-(trifluoromethylthio)phthalimide, a convenient and shelf-stable reagent for the direct trifluoromethylthiolation, has been developed. N-(Trifluoromethylthio)phthalimide can be used as an electrophilic source of F3 CS(+) and reacts readily with boronic acids and alkynes under copper catalysis. The utility of CF3 S-containing molecules as biologically active agents, the mild reaction conditions employed, and the high tolerance of functional groups demonstrate the potential of this new methodology to be widely applied in organic synthesis as well as industrial pharmaceutical and agrochemical research and development. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Evaluation of the phototoxicity of unsubstituted and alkylated polycyclic aromatic hydrocarbons to mysid shrimp (Americamysis bahia): Validation of predictive models.

    Science.gov (United States)

    Finch, Bryson E; Marzooghi, Solmaz; Di Toro, Dominic M; Stubblefield, William A

    2017-08-01

    Crude oils are composed of an assortment of hydrocarbons, some of which are polycyclic aromatic hydrocarbons (PAHs). Polycyclic aromatic hydrocarbons are of particular interest due to their narcotic and potential phototoxic effects. Several studies have examined the phototoxicity of individual PAHs and fresh and weathered crude oils, and several models have been developed to predict PAH toxicity. Fingerprint analyses of oils have shown that PAHs in crude oils are predominantly alkylated. However, current models for estimating PAH phototoxicity assume toxic equivalence between unsubstituted (i.e., parent) and alkyl-substituted compounds. This approach may be incorrect if substantial differences in toxic potency exist between unsubstituted and substituted PAHs. The objective of the present study was to examine the narcotic and photo-enhanced toxicity of commercially available unsubstituted and alkylated PAHs to mysid shrimp (Americamysis bahia). Data were used to validate predictive models of phototoxicity based on the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gap approach and to develop relative effect potencies. Results demonstrated that photo-enhanced toxicity increased with increasing methylation and that phototoxic PAH potencies vary significantly among unsubstituted compounds. Overall, predictive models based on the HOMO-LUMO gap were relatively accurate in predicting phototoxicity for unsubstituted PAHs but are limited to qualitative assessments. Environ Toxicol Chem 2017;36:2043-2049. © 2017 SETAC. © 2017 SETAC.

  11. Synergistic dual activation catalysis by palladium nanoparticles for epoxide ring opening with phenols.

    Science.gov (United States)

    Seth, Kapileswar; Roy, Sudipta Raha; Pipaliya, Bhavin V; Chakraborti, Asit K

    2013-07-04

    Synergistic dual activation catalysis has been devised for epoxide phenolysis wherein palladium nanoparticles induce electrophilic activation via coordination with the epoxide oxygen followed by nucleophilic activation through anion-π interaction with the aromatic ring of the phenol, and water (reaction medium) also renders assistance through 'epoxide-phenol' dual activation.

  12. Formation of radical cations in a model for the metabolism of aromatic hydrocarbons

    International Nuclear Information System (INIS)

    Lehner, Andreas F.; Horn, Jamie; Flesher, James W.

    2004-01-01

    To test the hypothesis that electrophilic radical cations are the major ultimate electrophilic and carcinogenic forms of benz[a]anthracene (BA), dibenz[a,h]anthracene (DBA), and benzo[a]pyrene (BP), we have focused on a chemical model of metabolism which parallels and duplicates known or potential metabolites of some polycyclic hydrocarbons formed in cells. Studies of this model system show that radical cations are hardly formed, if at all, in the case of BA or DBA but are definitely formed in the cases of the carcinogen BP as well as the non-carcinogenic hydrocarbons, pyrene and perylene. We conclude that the carcinogenicities of BA, DBA, BP, pyrene, and perylene are independent of one-electron oxidation to radical cation intermediates

  13. Catalytic Oxidation of Lignins into the Aromatic Aldehydes: General Process Trends and Development Prospects

    Science.gov (United States)

    Tarabanko, Valery E.; Tarabanko, Nikolay

    2017-01-01

    This review discusses principal patterns that govern the processes of lignins’ catalytic oxidation into vanillin (3-methoxy-4-hydroxybenzaldehyde) and syringaldehyde (3,5-dimethoxy-4-hydroxybenzaldehyde). It examines the influence of lignin and oxidant nature, temperature, mass transfer, and of other factors on the yield of the aldehydes and the process selectivity. The review reveals that properly organized processes of catalytic oxidation of various lignins are only insignificantly (10–15%) inferior to oxidation by nitrobenzene in terms of yield and selectivity in vanillin and syringaldehyde. Very high consumption of oxygen (and consequentially, of alkali) in the process—over 10 mol per mol of obtained vanillin—is highlighted as an unresolved and unexplored problem: scientific literature reveals almost no studies devoted to the possibilities of decreasing the consumption of oxygen and alkali. Different hypotheses about the mechanism of lignin oxidation into the aromatic aldehydes are discussed, and the mechanism comprising the steps of single-electron oxidation of phenolate anions, and ending with retroaldol reaction of a substituted coniferyl aldehyde was pointed out as the most convincing one. The possibility and development prospects of single-stage oxidative processing of wood into the aromatic aldehydes and cellulose are analyzed. PMID:29140301

  14. Vapor pressures and sublimation enthalpies of seven heteroatomic aromatic hydrocarbons measured using the Knudsen effusion technique

    Energy Technology Data Exchange (ETDEWEB)

    Goldfarb, Jillian L., E-mail: JillianLGoldfarb@gmail.co [Division of Engineering, Brown University, Providence, RI 02912 (United States); Suuberg, Eric M., E-mail: Eric_Suuberg@brown.ed [Division of Engineering, Brown University, Providence, RI 02912 (United States)

    2010-06-15

    The vapor pressures of seven heteroatom-containing cyclic aromatic hydrocarbons, ranging in molecular weight from (168.19 to 208.21) g . mol{sup -1} were measured over the temperature range of (301 to 486) K using the isothermal Knudsen effusion technique. The compounds measured include: anthraquinone, 9-fluorenone, 9-fluorenone oxime, phenoxazine, phenoxathiin, and 9H-pyrido[3,4-b]indole. These solid-state sublimation measurements provided values that are compared to vapor pressures of parent aromatic compounds (anthracene and fluorene) and to others with substituent groups in order to examine the effects of alcohol, ketone, pyridine, and pyrrole functionality on this property. The enthalpies and entropies of sublimation for each compound were determined from the Clausius-Clapeyron equation. Though there is no consistent trend in terms of the effects of substitutions on changes in the enthalpy or entropy of sublimation, we note that the prevalence of enthalpic or entropic driving forces on vapor pressure depend on molecule-specific factors and not merely molecular weight of the substituents.

  15. The Diels-Alder Cycloaddition Reaction of Substituted Hemifullerenes with 1,3-Butadiene: Effect of Electron-Donating and Electron-Withdrawing Substituents.

    Science.gov (United States)

    Mojica, Martha; Méndez, Francisco; Alonso, Julio A

    2016-02-12

    The Diels-Alder (DA) reaction provides an attractive route to increase the number of six member rings in substituted Polycyclic Aromatic Hydrocarbons (PAHs). The density functional theory (DFT) B3LYP method has been used in this work to inquire if the substitution of H over the edge of triindenetriphenylene (pristine hemifullerene 1) and pentacyclopentacorannulene (pristine hemifullerene 2), could improve the DA cycloaddition reaction with 1,3-butadiene. The substituents tested include electron-donating (NH₂, OMe, OH, Me, i-Pr) and electron-withdrawing groups (F, COOH, CF₃, CHO, CN, NO₂). The electronic, kinetic and thermodynamic parameters of the DA reactions of the substituted hemifullerenes with 1,3-butadiene have been analyzed. The most promising results were obtained for the NO₂ substituent; the activation energy barriers for reactions using this substituent were lower than the barriers for the pristine hemifullerenes. This leads us to expect that the cycloadditions to a starting fullerene fragment will be possible.

  16. Petroleum geochemistry of the Potwar Basin, Pakistan: II – Oil classification based on heterocyclic and polycyclic aromatic hydrocarbons

    International Nuclear Information System (INIS)

    Asif, Muhammad; Fazeelat, Tahira

    2012-01-01

    In a previous study, oils in the Potwar Basin (Upper Indus) of Pakistan were correlated based on the dissimilarity of source and depositional environment of organic matter (OM) using biomarkers and bulk stable isotopes. This study is aimed at supporting the classification of Potwar Basin oils into three groups (A, B and C) using the distribution of alkylnaphthalenes, alkylphenanthrenes, alkyldibenzothiophenes, alkyldibenzofurans, alkylfluorenes, alkylbiphenyls, triaromatic steroids, methyl triaromatic steroids, retene, methyl retenes and cadalene. The higher relative abundance of specific methyl isomers of naphthalene and phenanthrene and the presence of diagnostic aromatic biomarkers clearly indicate the terrigenous and oxic depositional environment of OM for group A oil. Group B and C oils are of marine origin and the aforementioned heterocyclic and polycyclic aromatic hydrocarbons (HCs) differentiate them clearly into two different groups. The relative percentages of heterocyclic aromatic HCs reveal that the distribution of these compounds is controlled by the depositional environment of the OM. Sulfur-containing heterocyclic aromatic HCs are higher in crude oils generated from source rocks deposited in suboxic depositional environments, while oxygen-containing heterocyclic aromatic HCs in combination with alkylfluorenes are higher in marine oxic and deltaic oils. Biomarker and aromatic HC parameters do not indicate significant differences in the thermal maturity of Potwar Basin oils. Triaromatic and methyl triaromatic steroids support the division of Potwar Basin oils into the three groups and their relative abundances are related to source OM rather than thermal maturity. Significantly higher amounts of C 20 and C 21 triaromtic steroids and the presence or absence of long chain triaromatic steroids (C 25 , C 26 , C 27 , and C 28 ) indicates that these compounds are probably formed from different biological precursors in each group. Different isomers of methyl

  17. Photolysis of aromatic pollutants in clean and dirty ice

    Science.gov (United States)

    Kahan, T.; Malley, P.; Stathis, A.

    2015-12-01

    Anthropogenic aromatic pollutants such as polycyclic aromatic hydrocarbons (PAHs) and substituted benzenes often become more toxic following atmospheric oxidation. Photolysis of these pollutants in ice can be much faster than that in aqueous solution, which might lead to higher carcinogenic loadings in snow-covered regions. In this work we investigate two things. First, we investigate whether toluene, which has been detected at very elevated concentrations near hydraulic fracturing operations, can undergo photolysis at ice surfaces. Toluene in aqueous solution does not absorb sunlight, so photolysis has not been considered a potential atmospheric fate. However, benzene was recently demonstrated to undergo a significant red shift in its absorbance at ice surfaces, leading to photolysis under environmentally-relevant conditions. Here we show that toluene also undergoes photolysis at ice surfaces. In a second set of experiments, we have investigated the effects of organic matter on the photolysis kinetics ofPAHs in ice and at ice surfaces. We found that very small loadings of hydrophobic organics such as octanol can significantly suppress PAH photolysis kinetics in ice, but that the primary effect of the more soluble fulvic acid is competitive photon absorption. Our results show that photochemistry of anthropogenic pollutants can follow very different mechanisms and kinetics in ice than in aqueous solution, and that the photochemical fate of these pollutants depends strongly on the composition of the snow. These results have implications for pollutant fate and human health in a wide range of snow-covered environments including remote areas, cities, and regions near gas and oil extraction operations.

  18. Converting lignin to aromatics: step by step

    NARCIS (Netherlands)

    Strassberger, Z.I.

    2014-01-01

    Lignin, the glue that holds trees together, is the most abundant natural resource of aromatics. In that respect, it is a far more advanced resource than crude oil. This is because lignin already contains the aromatic functional groups. Thus, catalytic conversion of lignin to high-value aromatics is

  19. Tailoring highly conductive graphene nanoribbons from small polycyclic aromatic hydrocarbons: a computational study

    KAUST Repository

    Bilić, A

    2013-06-14

    Pyrene, the smallest two-dimensional mesh of aromatic rings, with various terminal thiol substitutions, has been considered as a potential molecular interconnect. Charge transport through two terminal devices has been modeled using density functional theory (with and without self interaction correction) and the non-equilibrium Green\\'s function method. A tetra-substituted pyrene, with dual thiol terminal groups at opposite ends, has been identified as an excellent candidate, owing to its high conductance, virtually independent of bias voltage. The two possible extensions of its motif generate two series of graphene nanoribbons, with zigzag and armchair edges and with semimetallic and semiconducting electron band structure, respectively. The effects related to the wire length and the bias voltage on the charge transport have been investigated for both sets. The conductance of the nanoribbons with a zigzag edge does not show either length or voltage dependence, owing to an almost perfect electron transmission with a continuum of conducting channels. In contrast, for the armchair nanoribbons a slow exponential attenuation of the conductance with the length has been found, due to their semiconducting nature. © 2013 IOP Publishing Ltd.

  20. Synthesis and solid-state characterisation of 4-substituted methylidene oxindoles

    Science.gov (United States)

    2013-01-01

    Background 4-substituted methylidene oxindoles are pharmacologically important. Detailed analysis and comparison of all the interactions present in crystal structures is necessary to understand how these structures arise. The XPac procedure allows comparison of complete crystal structures of related families of compounds to identify assemblies that are mainly the result of close-packing as well as networks of directed interactions. Results Five 4-substituted methylidene oxindoles have been synthesized by the Knoevenagel condensation of oxindole with para-substituted aromatic aldehydes and were characterized in the solid state by x-ray crystallography. Hence, the structures of (3E)-3-(4-Bromobenzylidene)-1,3-dihydro-2H-indol-2-one, 3a, (3E)-3-(4-Chlorobenzylidene)-1,3-dihydro-2H-indol-2-one, 3b, (3E)-3-(4-Methoxybenzylidene)-1,3-dihydro-2H-indol-2-one, 3c, (3E)-3-(4-Methylbenzylidene)-1,3-dihydro-2H-indol-2-one, 3d and (3E)-3-(4-Nitrobenzylidene)-1,3-dihydro-2H-indol-2-one, 3e, were elucidated using single crystal X-ray crystallography. Conclusions A hydrogen bonded dimer molecular assembly or supramolecular construct was identified in all the crystal structures examined along with a further four 1D supramolecular constructs which were common to at least two of the family of structures studied. The 1D supramolecular constructs indicate that once the obvious strong interaction is satisfied to form hydrogen bonded dimer it is the conventionally weaker interactions, such as steric bulk and edge-to-face interactions which compete to influence the final structure formation. PMID:24517531

  1. An aromatic sensor with aversion to damaged strands confers versatility to DNA repair.

    Directory of Open Access Journals (Sweden)

    Olivier Maillard

    2007-04-01

    Full Text Available It was not known how xeroderma pigmentosum group C (XPC protein, the primary initiator of global nucleotide excision repair, achieves its outstanding substrate versatility. Here, we analyzed the molecular pathology of a unique Trp690Ser substitution, which is the only reported missense mutation in xeroderma patients mapping to the evolutionary conserved region of XPC protein. The function of this critical residue and neighboring conserved aromatics was tested by site-directed mutagenesis followed by screening for excision activity and DNA binding. This comparison demonstrated that Trp690 and Phe733 drive the preferential recruitment of XPC protein to repair substrates by mediating an exquisite affinity for single-stranded sites. Such a dual deployment of aromatic side chains is the distinctive feature of functional oligonucleotide/oligosaccharide-binding folds and, indeed, sequence homologies with replication protein A and breast cancer susceptibility 2 protein indicate that XPC displays a monomeric variant of this recurrent interaction motif. An aversion to associate with damaged oligonucleotides implies that XPC protein avoids direct contacts with base adducts. These results reveal for the first time, to our knowledge, an entirely inverted mechanism of substrate recognition that relies on the detection of single-stranded configurations in the undamaged complementary sequence of the double helix.

  2. An organic cosmo-barometer: Distinct pressure and temperature effects for methyl substituted polycyclic aromatic hydrocarbons

    International Nuclear Information System (INIS)

    Montgomery, Wren; Watson, Jonathan S.; Sephton, Mark A.

    2014-01-01

    There are a number of key structures that can be used to reveal the formation and modification history of organic matter in the cosmos. For instance, the susceptibility of organic matter to heat is well documented and the relative thermal stabilities of different isomers can be used as cosmothermometers. Yet despite being an important variable, no previously recognized organic marker of pressure exists. The absence of a pressure marker is unfortunate considering our ability to effectively recognize extraterrestrial organic structures both remotely and in the laboratory. There are a wide variety of pressures in cosmic settings that could potentially be reflected by organic structures. Therefore, to develop an organic cosmic pressure marker, we have used state-of-the-art diamond anvil cell (DAC) and synchrotron-source Fourier transform infrared (FTIR) spectroscopy to reveal the effects of pressure on the substitution patterns for representatives of the commonly encountered methyl substituted naphthalenes, specifically the dimethylnaphthalenes. Interestingly, although temperature and pressure effects are concordant for many isomers, pressure appears to have the opposite effect to heat on the final molecular architecture of the 1,5-dimethylnaphthalene isomer. Our data suggest the possibility of the first pressure parameter or 'cosmo-barometer' (1,5-dimethylnaphthalene/total dimethylnaphthalenes) that can distinguish pressure from thermal effects. Information can be obtained from the new pressure marker either remotely by instrumentation on landers or rovers or directly by laboratory measurement, and its use has relevance for all cases where organic matter, temperature, and pressure interplay in the cosmos.

  3. High atmosphere–ocean exchange of semivolatile aromatic hydrocarbons

    KAUST Repository

    González-Gaya, Belén

    2016-05-16

    Polycyclic aromatic hydrocarbons, and other semivolatile aromatic-like compounds, are an important and ubiquitous fraction of organic matter in the environment. The occurrence of semivolatile aromatic hydrocarbons is due to anthropogenic sources such as incomplete combustion of fossil fuels or oil spills, and other biogenic sources. However, their global transport, fate and relevance for the carbon cycle have been poorly assessed, especially in terms of fluxes. Here we report a global assessment of the occurrence and atmosphere-ocean fluxes of 64 polycyclic aromatic hydrocarbons analysed in paired atmospheric and seawater samples from the tropical and subtropical Atlantic, Pacific and Indian oceans. The global atmospheric input of polycyclic aromatic hydrocarbons to the global ocean is estimated at 0.09 Tg per month, four times greater than the input from the Deepwater Horizon spill. Moreover, the environmental concentrations of total semivolatile aromatic-like compounds were 10 2 -10 3 times higher than those of the targeted polycyclic aromatic hydrocarbons, with a relevant contribution of an aromatic unresolved complex mixture. These concentrations drive a large global deposition of carbon, estimated at 400 Tg C yr -1, around 15% of the oceanic CO2 uptake. © 2016 Macmillan Publishers Limited.

  4. Ubiquitin C-terminal electrophiles are activity-based probes for identification and mechanistic study of ubiquitin conjugating machinery.

    Science.gov (United States)

    Love, Kerry Routenberg; Pandya, Renuka K; Spooner, Eric; Ploegh, Hidde L

    2009-04-17

    Protein modification by ubiquitin (Ub) and ubiquitin-like modifiers (Ubl) requires the action of activating (E1), conjugating (E2), and ligating (E3) enzymes and is a key step in the specific destruction of proteins. Deubiquitinating enzymes (DUBs) deconjugate substrates modified with Ub/Ubl's and recycle Ub inside the cell. Genome mining based on sequence homology to proteins with known function has assigned many enzymes to this pathway without confirmation of either conjugating or DUB activity. Function-dependent methodologies are still the most useful for rapid identification or assessment of biological activity of expressed proteins from cells. Activity-based protein profiling uses chemical probes that are active-site-directed for the classification of protein activities in complex mixtures. Here we show that the design and use of an expanded set of Ub-based electrophilic probes allowed us to recover and identify members of each enzyme class in the ubiquitin-proteasome system, including E3 ligases and DUBs with previously unverified activity. We show that epitope-tagged Ub-electrophilic probes can be used as activity-based probes for E3 ligase identification by in vitro labeling and activity studies of purified enzymes identified from complex mixtures in cell lysate. Furthermore, the reactivity of our probe with the HECT domain of the E3 Ub ligase ARF-BP1 suggests that multiple cysteines may be in the vicinity of the E2-binding site and are capable of the transfer of Ub to self or to a substrate protein.

  5. Arginine-aromatic interactions and their effects on arginine-induced solubilization of aromatic solutes and suppression of protein aggregation

    KAUST Repository

    Shah, Dhawal

    2011-09-21

    We examine the interaction of aromatic residues of proteins with arginine, an additive commonly used to suppress protein aggregation, using experiments and molecular dynamics simulations. An aromatic-rich peptide, FFYTP (a segment of insulin), and lysozyme and insulin are used as model systems. Mass spectrometry shows that arginine increases the solubility of FFYTP by binding to the peptide, with the simulations revealing the predominant association of arginine to be with the aromatic residues. The calculations further show a positive preferential interaction coefficient, Γ XP, contrary to conventional thinking that positive Γ XP\\'s indicate aggregation rather than suppression of aggregation. Simulations with lysozyme and insulin also show arginine\\'s preference for aromatic residues, in addition to acidic residues. We use these observations and earlier results reported by us and others to discuss the possible implications of arginine\\'s interactions with aromatic residues on the solubilization of aromatic moieties and proteins. Our results also highlight the fact that explanations based purely on Γ XP, which measures average affinity of an additive to a protein, could obscure or misinterpret the underlying molecular mechanisms behind additive-induced suppression of protein aggregation. © 2011 American Institute of Chemical Engineers (AIChE).

  6. Arginine-aromatic interactions and their effects on arginine-induced solubilization of aromatic solutes and suppression of protein aggregation

    KAUST Repository

    Shah, Dhawal; Li, Jianguo; Shaikh, Abdul Rajjak; Rajagopalan, Raj

    2011-01-01

    We examine the interaction of aromatic residues of proteins with arginine, an additive commonly used to suppress protein aggregation, using experiments and molecular dynamics simulations. An aromatic-rich peptide, FFYTP (a segment of insulin), and lysozyme and insulin are used as model systems. Mass spectrometry shows that arginine increases the solubility of FFYTP by binding to the peptide, with the simulations revealing the predominant association of arginine to be with the aromatic residues. The calculations further show a positive preferential interaction coefficient, Γ XP, contrary to conventional thinking that positive Γ XP's indicate aggregation rather than suppression of aggregation. Simulations with lysozyme and insulin also show arginine's preference for aromatic residues, in addition to acidic residues. We use these observations and earlier results reported by us and others to discuss the possible implications of arginine's interactions with aromatic residues on the solubilization of aromatic moieties and proteins. Our results also highlight the fact that explanations based purely on Γ XP, which measures average affinity of an additive to a protein, could obscure or misinterpret the underlying molecular mechanisms behind additive-induced suppression of protein aggregation. © 2011 American Institute of Chemical Engineers (AIChE).

  7. Effect of the Polyketone Aromatic Pendent Groups on the Electrical Conductivity of the Derived MWCNTs-Based Nanocomposites

    Directory of Open Access Journals (Sweden)

    Nicola Migliore

    2018-06-01

    Full Text Available Electrically conductive plastics with a stable electric response within a wide temperature range are promising substitutes of conventional inorganic conductive materials. This study examines the preparation of thermoplastic polyketones (PK30 functionalized by the Paal–Knorr process with phenyl (PEA, thiophene (TMA, and pyrene (PMA pendent groups with the aim of optimizing the non-covalent functionalization of multiwalled carbon nanotubes (MWCNTs through π–π interactions. Among all the aromatic functionalities grafted to the PK30 backbone, the extended aromatic nuclei of PMA were found to be particularly effective in preparing well exfoliated and undamaged MWCNTs dispersions with a well-defined conductive percolative network above the 2 wt % of loading and in freshly prepared nanocomposites as well. The efficient and superior π–π interactions between PK30PMA and MWCNTs consistently supported the formation of nanocomposites with a highly stable electrical response after thermal solicitations such as temperature annealing at the softening point, IR radiation exposure, as well as several heating/cooling cycles from room temperature to 75 °C.

  8. PLS-based quantitative structure-activity relationship for substituted benzamides of clebopride type. Application of experimental design in drug design.

    Science.gov (United States)

    Norinder, U; Högberg, T

    1992-04-01

    The advantageous approach of using an experimentally designed training set as the basis for establishing a quantitative structure-activity relationship with good predictive capability is described. The training set was selected from a fractional factorial design scheme based on a principal component description of physico-chemical parameters of aromatic substituents. The derived model successfully predicts the activities of additional substituted benzamides of 6-methoxy-N-(4-piperidyl)salicylamide type. The major influence on activity of the 3-substituent is demonstrated.

  9. Pulse gas chromatographic study of adsorption of substituted aromatics and heterocyclic molecules on MIL-47 at zero coverage.

    Science.gov (United States)

    Duerinck, Tim; Couck, Sarah; Vermoortele, Frederik; De Vos, Dirk E; Baron, Gino V; Denayer, Joeri F M

    2012-10-02

    The low coverage adsorptive properties of the MIL-47 metal organic framework toward aromatic and heterocyclic molecules are reported in this paper. The effect of molecular functionality and size on Henry adsorption constants and adsorption enthalpies of alkyl and heteroatom functionalized benzene derivates and heterocyclic molecules was studied using pulse gas chromatography. By means of statistical analysis, experimental data was analyzed and modeled using principal component analysis and partial least-squares regression. Structure-property relationships were established, revealing and confirming several trends. Among the molecular properties governing the adsorption process, vapor pressure, mean polarizability, and dipole moment play a determining role.

  10. Anaerobic biotransformation of roxarsone and related N-substituted phenylarsonic acids

    Science.gov (United States)

    Cortinas, I.; Field, J.A.; Kopplin, M.; Garbarino, J.R.; Gandolfi, A.J.; Sierra-Alvarez, R.

    2006-01-01

    Large quantities of arsenic are introduced into the environment through land application of poultry litter containing the organoarsenical feed additive roxarsone (3-nitro-4-hydroxyphenylarsonic acid). The objective of this study was to evaluate the bioconversion of roxarsone and related N-substituted phenylarsonic acid derivatives under anaerobic conditions. The results demonstrate that roxarsone is rapidly transformed in the absence of oxygen to the corresponding aromatic amine, 4-hydroxy-3-aminophenylarsonic acid (HAPA). The formation of HAPA is attributable to the facile reduction of the nitro group. Electron-donating substrates, such as hydrogen gas, glucose, and lactate, stimulated the rate of nitro group reduction, indicating a microbial role. During long-term incubations, HAPA and the closely related 4-aminophenylarsonic acid (4-APA) were slowly biologically eliminated by up to 99% under methanogenic and sulfate-reducing conditions, whereas little or no removal occurred in heat-killed inoculum controls. Arsenite and, to a lesser extent, arsenate were observed as products of the degradation. Freely soluble forms of the inorganic arsenical species accounted for 19-28% of the amino-substituted phenylarsonic acids removed. This constitutes the first report of a biologically catalyzed rupture of the phenylarsonic group under anaerobic conditions. ?? 2006 American Chemical Society.

  11. Human bronchus-mediated mutagenesis of mammalian cells by carcinogenic polycyclic aromatic hydrocarbon

    DEFF Research Database (Denmark)

    Hsu, Ih Chang; Stoner, Gary D.; Autrup, Herman

    1978-01-01

    Cultured human bronchial explants activated benzo[alpha]pyrene (BzaP) into electrophilic metabolites that bind to DNA in bronchial epithelial cells. Promutagenic and mutagenic metabolites of BzaP were also released into the culture medium. An increase in mutation frequency for ouabain resistance ...

  12. A quantitative approach to nucleophilic organocatalysis

    Directory of Open Access Journals (Sweden)

    Herbert Mayr

    2012-09-01

    Full Text Available The key steps in most organocatalytic cyclizations are the reactions of electrophiles with nucleophiles. Their rates can be calculated by the linear free-energy relationship log k(20 °C = sN(E + N, where electrophiles are characterized by one parameter (E and nucleophiles are characterized by the solvent-dependent nucleophilicity (N and sensitivity (sN parameters.Electrophilicity parameters in the range –10 E N N parameters of enamines derived from phenylacetaldehyde and MacMillan’s imidazolidinones one can rationalize why only strong electrophiles, such as stabilized carbenium ions (–8 E E = –6.75, are suitable electrophiles for enamine activated reactions with imidazolidinones. Several mechanistic controversies concerning iminium and enamine activated reactions could thus be settled by studying the reactivities of independently synthesized intermediates.Kinetic investigations of the reactions of N-heterocyclic carbenes (NHCs with benzhydrylium ions showed that they have similar nucleophilicities to common organocatalysts (e.g., PPh3, DMAP, DABCO but are much stronger (100–200 kJ mol–1 Lewis bases. While structurally analogous imidazolylidenes and imidazolidinylidenes have comparable nucleophilicities and Lewis basicities, the corresponding deoxy Breslow intermediates differ dramatically in reactivity. The thousand-fold higher nucleophilicity of 2-benzylidene-imidazoline relative to 2-benzylidene-imidazolidine is explained by the gain of aromaticity during electrophilic additions to the imidazoline derivatives. O-Methylated Breslow intermediates are a hundred-fold less nucleophilic than deoxy Breslow intermediates.

  13. Superoxide radical-mediated photocatalytic oxidation of phenolic compounds over Ag{sup +}/TiO{sub 2}: Influence of electron donating and withdrawing substituents

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Jiadong [National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology, Beijing Engineering Research Center of Process Pollution Control, Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Xie, Yongbing, E-mail: ybxie@ipe.ac.cn [National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology, Beijing Engineering Research Center of Process Pollution Control, Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190 (China); Han, Qingzhen [State Key Laboratory of Multi-phase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190 (China); Cao, Hongbin [National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology, Beijing Engineering Research Center of Process Pollution Control, Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190 (China); Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300072 (China); Wang, Yujiao [Department of Chemical and Biomedical Engineering, University of Science and Technology Beijing (China); Nawaz, Faheem; Duan, Feng [National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology, Beijing Engineering Research Center of Process Pollution Control, Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190 (China); University of Chinese Academy of Sciences, Beijing 100049 (China)

    2016-03-05

    Highlights: • A weak EWG benefited photocatalytic oxidation of phenols the most. • Phenolic compounds were dominantly oxidized by ·O{sub 2}{sup −}, rather than ·OH, {sup 1}O{sub 2} or h{sup +}. • ·O{sub 2}{sup −} preferred to nucleophilically attack EDG substituted phenols. • ·O{sub 2}{sup −} more likely electrophilically attacked EWG substituted phenols. • ·O{sub 2}{sup −} simultaneously nucleophilically and electrophilically assaulted p-chlorophenol. - Abstract: A comparative study was constructed to correlate the electronic property of the substituents with the degradation rates of phenolic compounds and their oxidation pathways under UV with Ag{sup +}/TiO{sub 2} suspensions. It was verified that a weak electron withdrawing substituent benefited photocatalytic oxidation the most, while an adverse impact appeared when a substituent was present with stronger electron donating or withdrawing ability. The addition of p-benzoquinone dramatically blocked the degradation, confirming superoxide radicals (·O{sub 2}{sup −}) as the dominant photooxidant, rather than hydroxyl radicals, singlet oxygen or positive holes, which was also independent of the substituent. Hammett relationship was established based on pseudo-first-order reaction kinetics, and it revealed two disparate reaction patterns between ·O{sub 2}{sup −} and phenolic compounds, which was further verified by the quantum chemical computation on the frontier molecular orbitals and Mulliken charge distributions of ·O{sub 2}{sup −} and phenolic compounds. It was found that electron donating group (EDG) substituted phenols were more likely nucleophilically attacked by ·O{sub 2}{sup −}, while ·O{sub 2}{sup −} preferred to electrophilically assault electron withdrawing group (EWG) substituted phenols. Exceptionally, electrophilic and nucleophilic attack by ·O{sub 2}{sup −} could simultaneously occur in p-chlorophenol degradation, consequently leading to its highest rate

  14. Benzo-thia-fused [n]Thienoacenequinodimethanes with Small to Moderate Diradical Characters: The Role of Pro-aromaticity versus Anti-aromaticity

    KAUST Repository

    Shi, Xueliang

    2016-01-19

    Open-shell singlet diradicaloids recently have received much attention due to their unique optical, electronic and magnetic properties and promising applications in materials science. Among various diradicaloids, quinoidal π-conjugated molecules have become the prevailing designs. However, there still lacks fundamental understanding on how the fusion mode and pro-aromaticity/anti-aromaticity affect their diradical character and physical properties. In this work, a series of pro-aromatic benzo-thia-fused [n]thienoacenequinodimethanes (Thn-TIPS (n=1-3) and BDTh-TIPS) were synthesized and compared with the previously reported anti-aromatic bisindeno-[n]thienoacenes (Sn-TIPS, n=1-4). The ground-state geometric and electronic structures of these new quinoidal molecules were systematically investigated by X-ray crystallographic analysis, variable temperature NMR, ESR, SQUID, Raman, and electronic absorption spectroscopy, assisted by DFT calculations. It was found that the diradical character index (y0) increased from nearly zero for Th1-TIPS to 2.4% for Th2-TIPS, 18.2% for Th3-TIPS, and 38.2% for BDTh-TIPS, due to the enhanced aromatic stabilization. Consequently, with the extension of molecular size, the one-photon absorption spectra are gradually red-shifted, the two-photon absorption (TPA) cross section values increase, and the singlet excited state lifetimes decrease. By comparison with the corresponding anti-aromatic analogues Sn-TIPS (n=1-3), the pro-aromatic Thn-TIPS (n=1-3) exhibit larger diradical character, longer singlet excited state lifetime and larger TPA cross section value. At the same time, they display distinctively different electronic absorption spectra and improved electrochemical amphotericity. Spectroelectrochemical studies revealed a good linear relationship between the optical energy gaps and the molecular length in the neutral, radical cationic and dicationic forms. Our research work disclosed the significant difference between the pro-aromatic

  15. Benzo-thia-fused [n]Thienoacenequinodimethanes with Small to Moderate Diradical Characters: The Role of Pro-aromaticity versus Anti-aromaticity

    KAUST Repository

    Shi, Xueliang; Quintero, EstefanÍ a; Lee, Sangsu; Jing, Linzhi; Herng, Tun Seng; Zheng, Bin; Huang, Kuo-Wei; Ló pez Navarrete, Juan T.; Ding, Jun; Kim, Dongho; Casado, Juan; Chi, Chunyan

    2016-01-01

    Open-shell singlet diradicaloids recently have received much attention due to their unique optical, electronic and magnetic properties and promising applications in materials science. Among various diradicaloids, quinoidal π-conjugated molecules have become the prevailing designs. However, there still lacks fundamental understanding on how the fusion mode and pro-aromaticity/anti-aromaticity affect their diradical character and physical properties. In this work, a series of pro-aromatic benzo-thia-fused [n]thienoacenequinodimethanes (Thn-TIPS (n=1-3) and BDTh-TIPS) were synthesized and compared with the previously reported anti-aromatic bisindeno-[n]thienoacenes (Sn-TIPS, n=1-4). The ground-state geometric and electronic structures of these new quinoidal molecules were systematically investigated by X-ray crystallographic analysis, variable temperature NMR, ESR, SQUID, Raman, and electronic absorption spectroscopy, assisted by DFT calculations. It was found that the diradical character index (y0) increased from nearly zero for Th1-TIPS to 2.4% for Th2-TIPS, 18.2% for Th3-TIPS, and 38.2% for BDTh-TIPS, due to the enhanced aromatic stabilization. Consequently, with the extension of molecular size, the one-photon absorption spectra are gradually red-shifted, the two-photon absorption (TPA) cross section values increase, and the singlet excited state lifetimes decrease. By comparison with the corresponding anti-aromatic analogues Sn-TIPS (n=1-3), the pro-aromatic Thn-TIPS (n=1-3) exhibit larger diradical character, longer singlet excited state lifetime and larger TPA cross section value. At the same time, they display distinctively different electronic absorption spectra and improved electrochemical amphotericity. Spectroelectrochemical studies revealed a good linear relationship between the optical energy gaps and the molecular length in the neutral, radical cationic and dicationic forms. Our research work disclosed the significant difference between the pro-aromatic

  16. Survey of benzene and aromatics in Canadian Gasoline - 1994

    International Nuclear Information System (INIS)

    Tushingham, M.

    1996-01-01

    A comprehensive database of the benzene and aromatics levels of gasoline produced in or imported into Canada during 1994, was presented. Environment Canada conducted a survey that requested refineries and importers to report quarterly on benzene and aromatics levels in gasoline. Benzene, which has been declared toxic by the Canadian Environmental Protection Act, is found in gasoline and is formed during the combustion of the aromatic components of gasoline. It was shown that benzene and aromatics levels differ regionally and seasonally. There are also variations in benzene levels between batches of gasoline produced at any one refinery. This report listed the responses to the benzene/aromatics survey. It also described the analytical procedures used to measure benzene and aromatics levels in gasoline, and provided guidelines for reporting gasoline benzene and total aromatics data. 7 tabs., 21 figs

  17. Aromatic residues located close to the active center are essential for the catalytic reaction of flap endonuclease-1 from hyperthermophilic archaeon Pyrococcus horikoshii.

    Science.gov (United States)

    Matsui, Eriko; Abe, Junko; Yokoyama, Hideshi; Matsui, Ikuo

    2004-04-16

    Flap endonuclease-1 (FEN-1) possessing 5'-flap endonuclease and 5'-->3' exonuclease activity plays important roles in DNA replication and repair. In this study, the kinetic parameters of mutants at highly conserved aromatic residues, Tyr33, Phe35, Phe79, and Phe278-Phe279, in the vicinity of the catalytic centers of FEN-1 were examined. The substitution of these aromatic residues with alanine led to a large reduction in kcat values, although these mutants retained Km values similar to that of the wild-type enzyme. Notably, the kcat of Y33A and F79A decreased 333-fold and 71-fold, respectively, compared with that of the wild-type enzyme. The aromatic residues Tyr33 and Phe79, and the aromatic cluster Phe278-Phe279 mainly contributed to the recognition of the substrates without the 3' projection of the upstream strand (the nick, 5'-recess-end, single-flap, and pseudo-Y substrates) for the both exo- and endo-activities, but played minor roles in recognizing the substrates with the 3' projection (the double flap substrate and the nick substrate with the 3' projection). The replacement of Tyr33, Phe79, and Phe278-Phe279, with non-charged aromatic residues, but not with aliphatic hydrophobic residues, recovered the kcat values almost fully for the substrates without the 3' projection of the upstream strand, suggesting that the aromatic groups of Tyr33, Phe79, and Phe278-Phe279 might be involved in the catalytic reaction, probably via multiple stacking interactions with nucleotide bases. The stacking interactions of Tyr33 and Phe79 might play important roles in fixing the template strand and the downstream strand, respectively, in close proximity to the active center to achieve the productive transient state leading to the hydrolysis.

  18. Energy of Intramolecular Hydrogen Bonding in ortho-Hydroxybenzaldehydes, Phenones and Quinones. Transfer of Aromaticity from ipso-Benzene Ring to the Enol System(s

    Directory of Open Access Journals (Sweden)

    Danuta Rusinska-Roszak

    2017-03-01

    Full Text Available Intramolecular hydrogen bonding (HB is one of the most studied noncovalent interactions of molecules. Many physical, spectral, and topological properties of compounds are under the influence of HB, and there are many parameters used to notice and to describe these changes. Hitherto, no general method of measurement of the energy of intramolecular hydrogen bond (EHB has been put into effect. We propose the molecular tailoring approach (MTA for EHB calculation, modified to apply it to Ar-O-H∙∙∙O=C systems. The method, based on quantum calculations, was checked earlier for hydroxycarbonyl-saturated compounds, and for structures with resonance-assisted hydrogen bonding (RAHB. For phenolic compounds, the accuracy, repeatability, and applicability of the method is now confirmed for nearly 140 structures. For each structure its aromaticity HOMA indices were calculated for the central (ipso ring and for the quasiaromatic rings given by intramolecular HB. The comparison of calculated HB energies and values of estimated aromaticity indices allowed us to observe, in some substituted phenols and quinones, the phenomenon of transfer of aromaticity from the ipso-ring to the H-bonded ring via the effect of electron delocalization.

  19. Catalytic Oxidation of Lignins into the Aromatic Aldehydes: General Process Trends and Development Prospects

    Directory of Open Access Journals (Sweden)

    Valery E. Tarabanko

    2017-11-01

    Full Text Available This review discusses principal patterns that govern the processes of lignins’ catalytic oxidation into vanillin (3-methoxy-4-hydroxybenzaldehyde and syringaldehyde (3,5-dimethoxy-4-hydroxybenzaldehyde. It examines the influence of lignin and oxidant nature, temperature, mass transfer, and of other factors on the yield of the aldehydes and the process selectivity. The review reveals that properly organized processes of catalytic oxidation of various lignins are only insignificantly (10–15% inferior to oxidation by nitrobenzene in terms of yield and selectivity in vanillin and syringaldehyde. Very high consumption of oxygen (and consequentially, of alkali in the process—over 10 mol per mol of obtained vanillin—is highlighted as an unresolved and unexplored problem: scientific literature reveals almost no studies devoted to the possibilities of decreasing the consumption of oxygen and alkali. Different hypotheses about the mechanism of lignin oxidation into the aromatic aldehydes are discussed, and the mechanism comprising the steps of single-electron oxidation of phenolate anions, and ending with retroaldol reaction of a substituted coniferyl aldehyde was pointed out as the most convincing one. The possibility and development prospects of single-stage oxidative processing of wood into the aromatic aldehydes and cellulose are analyzed.

  20. Identification of reaction products from reactions of free chlorine with the lipid-regulator gemfibrozil.

    Science.gov (United States)

    Krkošek, Wendy H; Koziar, Stephen A; White, Robert L; Gagnon, Graham A

    2011-01-01

    High global consumption rates have led to the occurrence of pharmaceutically active compounds (PhACs) in wastewater. The use of chlorine to disinfect wastewater prior to release into the environment may convert PhACs into uncharacterized chlorinated by-products. In this investigation, chlorination of a common pharmaceutical, the antihyperlipidemic agent gemfibrozil, was documented. Gemfibrozil (2,2-dimethyl-5-(2,5-dimethylphenoxy)pentanoic acid) was reacted with sodium hypochlorite and product formation was monitored by gas chromatography-mass spectrometry (GC-MS). The incorporation of one, two or three chlorine atoms into the aromatic region of gemfibrozil was demonstrated using negative-ion electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometry (ESI-MS/MS). Further analysis using (1)H nuclear magnetic resonance (NMR) spectroscopy identified the reaction products as 4'-ClGem (5-(4-chloro-2,5-dimethylphenoxy)-2,2-dimethylpentanoic acid) 4',6'-diClGem (5-(4,6-dichloro-2,5-dimethylphenoxy)-2,2-dimethylpentanoic acid), and 3',4',6'-triClGem (5-(3,4,6-trichloro-2,5-dimethylphenoxy)-2,2-dimethylpentanoic acid), products consistent with electrophilic aromatic substitution reactions. The rapid reaction of gemfibrozil with free chlorine at pH conditions relevant to water treatment indicates that a mixture of chlorinated gemfibrozils is likely to be found in wastewater disinfected with chlorine. Copyright © 2010 Elsevier Ltd. All rights reserved.

  1. Bicyclic Baird-type aromaticity

    Science.gov (United States)

    Cha, Won-Young; Kim, Taeyeon; Ghosh, Arindam; Zhang, Zhan; Ke, Xian-Sheng; Ali, Rashid; Lynch, Vincent M.; Jung, Jieun; Kim, Woojae; Lee, Sangsu; Fukuzumi, Shunichi; Park, Jung Su; Sessler, Jonathan L.; Chandrashekar, Tavarekere K.; Kim, Dongho

    2017-12-01

    Classic formulations of aromaticity have long been associated with topologically planar conjugated macrocyclic systems. The theoretical possibility of so-called bicycloaromaticity was noted early on. However, it has yet to be demonstrated by experiment in a simple synthetic organic molecule. Conjugated organic systems are attractive for studying the effect of structure on electronic features. This is because, in principle, they can be modified readily through dedicated synthesis. As such, they can provide useful frameworks for testing by experiment with fundamental insights provided by theory. Here we detail the synthesis and characterization of two purely organic non-planar dithienothiophene-bridged [34]octaphyrins that permit access to two different aromatic forms as a function of the oxidation state. In their neutral forms, these congeneric systems contain competing 26 and 34 π-electronic circuits. When subject to two-electron oxidation, electronically mixed [4n+1]/[4n+1] triplet biradical species in the ground state are obtained that display global aromaticity in accord with Baird's rule.

  2. Volatilisation of aromatic hydrocarbons from soil

    DEFF Research Database (Denmark)

    Lindhardt, B.; Christensen, T.H.

    1996-01-01

    The non-steady-state fluxes of aromatic hydrocarbons were measured in the laboratory from the surface of soils contaminated with coal tar Four soil samples from a former gasworks site were used for the experiments. The fluxes were quantified for 11 selected compounds, 4 mono- and 7 polycyclic...... aromatic hydrocarbons, for a period of up to 8 or 16 days. The concentrations of the selected compounds in the soils were between 0.2 and 3,100 mu g/g. The study included the experimental determination of the distribution coefficient of the aromatic hydrocarbons between the sorbed phase and the water under...... saturated conditions. The determined distribution coefficients showed that the aromatic hydrocarbons were more strongly sorbed to the total organic carbon including the coal tar pitch - by a factor of 8 to 25 - than expected for natural organic matter. The fluxes were also estimated using an analytical...

  3. Novel molecular-level evidence of iodine binding to natural organic matter from Fourier transform ion cyclotron resonance mass spectrometry

    International Nuclear Information System (INIS)

    Xu, Chen; Chen, Hongmei; Sugiyama, Yuko; Zhang, Saijin; Li, Hsiu-Ping; Ho, Yi-Fang; Chuang, Chia-ying; Schwehr, Kathleen A.; Kaplan, Daniel I.; Yeager, Chris; Roberts, Kimberly A.; Hatcher, Patrick G.; Santschi, Peter H.

    2013-01-01

    Major fractions of radioiodine ( 129 I) are associated with natural organic matter (NOM) in the groundwater and surface soils of the Savannah River Site (SRS). Electrospray ionization coupled to Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS) was applied to elucidate the interactions between inorganic iodine species (iodide and iodate) and a fulvic acid (FA) extracted from a SRS surface soil. Iodate is likely reduced to reactive iodine species by the lignin- and tannin-like compounds or the carboxylic-rich alicyclic molecules (CRAM), during which condensed aromatics and lignin-like compounds were generated. Iodide is catalytically oxidized into reactive iodine species by peroxides, while FA is oxidized by peroxides into more aliphatic and less aromatic compounds. Only 9% of the total identified organo-iodine compounds derived from molecules originally present in the FA, whereas most were iodine binding to newly-produced compounds. The resulting iodinated molecules were distributed in three regions in the van Krevelen diagrams, denoting unsaturated hydrocarbons, lignin and protein. Moreover, characteristics of these organo-iodine compounds, such as their relatively low O/C ratios ( 2 or -HNCOR groups and a ring-activating functionality to favor the electrophilic substitution. The ESI-FTICR-MS technique provides novel evidence to better understand the reactivity and scavenging properties of NOM towards radioiodine and possible influence of NOM on 129 I migration. Highlights: ► IO 3 − reduced by lignin-, tannin-like compounds/carboxylic-rich alicyclic molecules ► Condensed aromatic and lignin-like compounds generated after iodate-iodination ► Aliphatic and less aromatic compounds formed after iodide-iodination ► Organo-iodine identified as unsaturated hydrocarbons, lignin and protein ► Organo-iodine with low O/C ratios imply less environmental mobility

  4. SYNTHESIS AND EVALUATION OF NEW PHTHALAZINE SUBSTITUTED β-LACTAM DERIVATIVES AS CARBONIC ANHYDRASE INHIBITORS.

    Science.gov (United States)

    Berber, Nurcan; Arslan, Mustafa; Bilen, Çiğdem; Sackes, Zübeyde; Gençer, Nahit; Arslan, Oktay

    2015-01-01

    A new series of phthalazine substituted β-lactam derivatives were synthesized and their inhibitory effects on the activity of purified human carbonic anhydrase (hCA I and II) were evaluated. 2H-Indazolo[2,1-b]phthala- zine-trione derivative was prepared with 4-nitrobenzaldehyde, dimedone, and phthalhydrazide in the presence of TFA in DMF, and the nitro group was reduced to 13-(4-aminophenyl)-3,3-dimethyl-3,4-dihydro- 2H-indazolo[1,2-b]phthalazine-1,6,11(13H)-trione with SnCl2 · 2H2O. The reduced compound was re- acted with different aromatic aldehydes, and phthalazine substituted imines were synthesized. The imine compounds undergo (2+2) cycloaddition reactions with ketenes to produce 2H-indazolo[2,1-b]phthala-zine-trione substituted β-lactam derivatives. The β-lactam compounds were tested as inhibitors of the CA isoenzyme activity. The results showed that all the synthesized compounds inhibited the CA isoenzyme activity. 1-(4-(3,3-dimethyl- 1,6,1 1-trioxo-2,3,4,6,11,13-hexahydro-1H-indazolo[1,2-b]phthalazin-13- yl)phenyl)-2-oxo-4-p-tolylazetidin-3-yl acetate (IC50 = 6.97 µM for hCA I and 8.48 µM for hCA II) had the most inhibitory effect.

  5. Basic deuteroexchange in complexes of transition metals with nitrogen-containing aromatic heterocycles

    International Nuclear Information System (INIS)

    Tupitsyn, I.F.

    1986-01-01

    A study was made of the kinetics of deuteroexchange in the methyl group in complexes of one metal [nickel(II)] with different methyl-substituted aromatic heterocycles and in isostructural complexes of one ligand (2-methylquinoline) with different central metal atoms (Mn 2+ , Ni 2+ , Cu 2+ , Zn 2+ ). The order in which the structures of the ligands influence the rate of deuteroexchange in the complexes does not correspond qualitatively with the order of increase in the rate of deuteroexchange in the noncoordinated ligands. The rate of deuteroexchange is only weakly influenced by change in the identity of the metal complex former. A deuteroexchange mechanism is proposed and discussed. A structure arising in the course of the exchange process with transfer of electron density from the heterocyclic ligand to the metal ion forms the transition state of the reaction

  6. Tandem ring-closing metathesis/isomerization reactions for the total synthesis of violacein

    DEFF Research Database (Denmark)

    Petersen, Mette Terp; Nielsen, Thomas Eiland

    2013-01-01

    A series of 5-substituted 2-pyrrolidinones was synthesized through a one-pot ruthenium alkylidene-catalyzed tandem RCM/isomerization/nucleophilic addition sequence. The intermediates resulting from RCM/isomerization showed reactivity toward electrophiles in aldol condensation reactions which...

  7. Bioassay of polycyclic aromatic hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Van Kirk, E.A.

    1980-08-01

    A positive relationship was found between the photodynamic activity of 24 polycyclic aromatic hydrocarbons versus published results on the mutagenicity, carcinogenicity, and initiation of unscheduled DNA synthesis. Metabolic activation of benzo(a)pyrene resulted in detection of increased mutagenesis in Paramecium tetraurelia as found also in the Ames Salmonella assay. The utility of P. tetraurelia as a biological detector of hazardous polycyclic aromatic hydrocarbons is discussed.

  8. How non-conventional feedstocks will affect aromatics technologies

    Energy Technology Data Exchange (ETDEWEB)

    Koehler, E. [Clariant Produkte (Deutschland) GmbH, Muenchen (Germany)

    2013-11-01

    The abundance of non-conventional feedstocks such as coal and shale gas has begun to affect the availability of traditional base chemicals such as propylene and BTX aromatics. Although this trend is primarily fueled by the fast growing shale gas economy in the US and the abundance of coal in China, it will cause the global supply and demand situation to equilibrate across the regions. Lower demand for gasoline and consequently less aromatics rich reformate from refineries will further tighten the aromatics markets that are expected to grow at healthy rates, however. Refiners can benefit from this trend by abandoning their traditional fuel-oriented business model and becoming producers of petrochemical intermediates, with special focus on paraxylene (PX). Cheap gas from coal (via gasification) or shale reserves is an advantaged feedstock that offers a great platform to make aromatics in a cost-competitive manner, especially in regions where naphtha is in short supply. Gas condensates (LPG and naphtha) are good feedstocks for paraffin aromatization, and methanol from coal or (shale) gas can be directly converted to BTX aromatics (MTA) or alkylated with benzene or toluene to make paraxylene. Most of today's technologies for the production and upgrading of BTX aromatics and their derivatives make use of the unique properties of zeolites. (orig.)

  9. Batch and Flow Photochemical Benzannulations Based on the Reaction of Ynamides and Diazo Ketones. Application to the Synthesis of Polycyclic Aromatic and Heteroaromatic Compounds

    Science.gov (United States)

    Willumstad, Thomas P.; Haze, Olesya; Mak, Xiao Yin; Lam, Tin Yiu; Wang, Yu-Pu; Danheiser*, Rick L.

    2013-01-01

    Highly substituted polycyclic aromatic and heteroaromatic compounds are produced via a two-stage tandem benzannulation/cyclization strategy. The initial benzannulation step proceeds via a pericyclic cascade mechanism triggered by thermal or photochemical Wolff rearrangement of a diazo ketone. The photochemical process can be performed using a continuous flow reactor which facilitates carrying out reactions on a large scale and minimizes the time required for photolysis. Carbomethoxy ynamides as well as more ketenophilic bissilyl ynamines and N-sulfonyl and N-phosphoryl ynamides serve as the reaction partner in the benzannulation step. In the second stage of the strategy, RCM generates benzofused nitrogen heterocycles, and various heterocyclization processes furnish highly substituted and polycyclic indoles of types that were not available by using the previous cyclobutenone-based version of the tandem strategy. PMID:24116731

  10. Metabolism and Biomarkers of Heterocyclic Aromatic Amines in Molecular Epidemiology Studies: Lessons Learned from Aromatic Amines

    Science.gov (United States)

    2011-01-01

    Aromatic amines and heterocyclic aromatic amines (HAAs) are structurally related classes of carcinogens that are formed during the combustion of tobacco or during the high-temperature cooking of meats. Both classes of procarcinogens undergo metabolic activation by N-hydroxylation of the exocyclic amine group, to produce a common proposed intermediate, the arylnitrenium ion, which is the critical metabolite implicated in toxicity and DNA damage. However, the biochemistry and chemical properties of these compounds are distinct and different biomarkers of aromatic amines and HAAs have been developed for human biomonitoring studies. Hemoglobin adducts have been extensively used as biomarkers to monitor occupational and environmental exposures to a number of aromatic amines; however, HAAs do not form hemoglobin adducts at appreciable levels and other biomarkers have been sought. A number of epidemiologic studies that have investigated dietary consumption of well-done meat in relation to various tumor sites reported a positive association between cancer risk and well-done meat consumption, although some studies have shown no associations between well-done meat and cancer risk. A major limiting factor in most epidemiological studies is the uncertainty in quantitative estimates of chronic exposure to HAAs and, thus, the association of HAAs formed in cooked meat and cancer risk has been difficult to establish. There is a critical need to establish long-term biomarkers of HAAs that can be implemented in molecular epidemioIogy studies. In this review article, we highlight and contrast the biochemistry of several prototypical carcinogenic aromatic amines and HAAs to which humans are chronically exposed. The biochemical properties and the impact of polymorphisms of the major xenobiotic-metabolizing enzymes on the biological effects of these chemicals are examined. Lastly, the analytical approaches that have been successfully employed to biomonitor aromatic amines and HAAs, and

  11. Analysis of polycyclic aromatic hydrocarbons using desorption atmospheric pressure chemical ionization coupled to a portable mass spectrometer.

    Science.gov (United States)

    Jjunju, Fred P M; Maher, Simon; Li, Anyin; Badu-Tawiah, Abraham K; Taylor, Stephen; Cooks, R Graham

    2015-02-01

    Desorption atmospheric pressure chemical ionization (DAPCI) is implemented on a portable mass spectrometer and applied to the direct detection of polycyclic aromatic hydrocarbons (PAHs) and alkyl substituted benzenes. The presence of these compounds in the environment poses a significant threat to the health of both humans and wildlife because of their carcinogenic, toxic, and mutagenic properties. As such, instant detection outside of the laboratory is of particular importance to allow in-situ measurement at the source. Using a rapid, high throughput, miniature, handheld mass spectrometer, several alkyl substituted benzenes and PAHs (i.e., 1,2,3,5-tetramethylbenzene, pentamethylbenzene, hexamethylbenzene, fluoranthene, anthracene, benzo[k]fluoranthene, dibenz[a,h]anthracene, acenaphthene, indeno[1,2,3-c,d]pyrene, 9-ethylfluorene, and 1-benzyl-3-methyl-naphthalene) were identified and characterized using tandem mass spectrometry (MS/MS) from ambient surfaces, in the open air. This method can provide almost instantaneous information while minimizing sample preparation, which is advantageous in terms of both cost and simplicity of analysis. This MS-based technique is applicable to a wide range of environmental organic molecules.

  12. Aromatization of n-octane over Pd/C catalysts

    KAUST Repository

    Yin, Mengchen; Natelson, Robert H.; Campos, Andrew A.; Kolar, Praveen; Roberts, William L.

    2013-01-01

    Gas-phase aromatization of n-octane was investigated using Pd/C catalyst. The objectives were to: (1) determine the effects of temperature (400-600 °C), weight hourly space velocity (WHSV) (0.8-∞), and hydrogen to hydrocarbon molar ratio (MR) (0-6) on conversion, selectivity, and yield (2) compare the activity of Pd/C with Pt/C and Pt/KL catalysts and (3) test the suitability of Pd/C for aromatization of different alkanes including n-hexane, n-heptane, and n-octane. Pd/C exhibited the best aromatization performance, including 54.4% conversion and 31.5% aromatics yield at 500 °C, WHSV = 2 h-1, and a MR of 2. The Pd/C catalyst had higher selectivity towards the preferred aromatics including ethylbenzene and xylenes, whereas Pt/KL had higher selectivity towards benzene and toluene. The results were somewhat consistent with adsorbed n-octane cyclization proceeding mainly through the six-membered ring closure mechanism. In addition, Pd/C was also capable of catalyzing aromatization of n-hexane and n-heptane. © 2012 Elsevier Ltd. All rights reserved.

  13. Proximate Composition, Mineral Content and Fatty Acids Analyses of Aromatic and Non-Aromatic Indian Rice

    Directory of Open Access Journals (Sweden)

    Deepak Kumar Verma

    2017-01-01

    Full Text Available Awareness on nutritive value and health benefits of rice is of vital importance in order to increase the consumption of rice in daily diet of the human beings. In this study, a total of six aromatic and two non-aromatic rice accessions grown in India were analysed for their nutritional quality attributes including proximate composition, mineral contents and fatty acids. Data with three replications were used to measure Pearson's simple correlation co-efficient in order to establish the relationship among various nutritional quality attributes. The result on proximate composition showed that Govind Bhog had the highest moisture (13.57% and fat (0.92% content, which signifies its tasty attribute. Badshah Bhog exhibited the highest fibre content (0.85%, carbohydrate content (82.70% and food energy (365.23 kCal per 100 g. Among the minerals, the higher Ca (98.75 mg/kg, Zn (17.00 mg/kg and Fe (31.50 mg/kg were in Gopal Bhog, whereas the highest Na (68.85 mg/kg was in Badshah Bhog, the highest K (500.00 mg/kg was in Swetganga, Khushboo and Sarbati. The highest contents of unsaturated fatty acids viz. oleic acid (49.14%, linoleic acid (46.99% and linolenic acid (1.27% were found in Sarbati, whereas the highest content of saturated fatty acids viz. myristic acid (4.60% and palmitic acid (31.91% were found in Govind Bhog and stearic acid (6.47% in Todal. The identified aromatic rice accessions Gopal Bhog, Govind Bhog and Badshah Bhog and non-aromatic rice accession Sarbati were found nutritionally superior among all eight tested accessions. The nutritional quality oriented attributes in this study were competent with recognized prominent aromatic and non-aromatic rice accessions as an index of their nutritional worth and recommend to farmers and consumers which may be graded as export quality rice with good unique nutritional values in international market.

  14. Simple, heart-smart substitutions

    Science.gov (United States)

    Coronary artery disease - heart smart substitutions; Atherosclerosis - heart smart substitutions; Cholesterol - heart smart substitutions; Coronary heart disease - heart smart substitutions; Healthy diet - heart ...

  15. Photoelectron spectra and electronic structure of nitrogen analogues of boron β-diketonates with aromatic substituents

    Energy Technology Data Exchange (ETDEWEB)

    Tikhonov, Sergey A., E-mail: allser@bk.ru [Far Eastern Federal University, 8 Sukhanova St., Vladivostok, 690950 (Russian Federation); Vovna, Vitaliy I. [Far Eastern Federal University, 8 Sukhanova St., Vladivostok, 690950 (Russian Federation); Borisenko, Aleksandr V. [Vladivostok Branch of Russian Customs Academy, 16v Strelkovaya St., Vladivostok, 690034 (Russian Federation)

    2016-11-15

    Highlights: • The electronic structures of three nitrogen analogues of boron β-diketonates have been investigated. • UV photoelectron spectra have been interpreted. • The structure of the UV photoelectron spectra is in good agreement with the energies and compositions of Kohn-Sham orbitals. - Abstract: The electronic structure of three nitrogen analogoues of boron β-diketonates containing aromatic substituents was studied by the ultraviolet photoelectron spectroscopy and within the density functional theory. In order to determine effects of heteroatom substitution in the chelate ligand, a comparative analysis was carried out for the electronic structure of three model compounds. In a range of model compounds, the HOMO's nature was revealed to be the same. The HOMO-1 orbital of nitrogen containing compounds is determined by the presence of lone electron pairs of nitrogen. In a range of the complexes under study, the influence of aromatic substituents on the electronic structure was defined. In the imidoylamidinate complex, in contrast to formazanates and β-diketonates, it was found the absence of any noticeable mixing of π-orbitals of the chelate and benzene rings. It was shown that within energy range to 11 eV, the calculated results reproduce well the energy differences between the ionized states of complexes.

  16. AN AROMATIC INVENTORY OF THE LOCAL VOLUME

    International Nuclear Information System (INIS)

    Marble, A. R.; Engelbracht, C. W.; Block, M.; Van Zee, L.; Dale, D. A.; Cohen, S. A.; Schuster, M. D.; Smith, J. D. T.; Gordon, K. D.; Wu, Y.; Lee, J. C.; Kennicutt, R. C.; Skillman, E. D.; Johnson, L. C.; Calzetti, D.; Lee, H.

    2010-01-01

    Using infrared photometry from the Spitzer Space Telescope, we perform the first inventory of aromatic feature emission (also commonly referred to as polycyclic aromatic hydrocarbon emission) for a statistically complete sample of star-forming galaxies in the local volume. The photometric methodology involved is calibrated and demonstrated to recover the aromatic fraction of the Infrared Array Camera 8 μm flux with a standard deviation of 6% for a training set of 40 SINGS galaxies (ranging from stellar to dust dominated) with both suitable mid-infrared Spitzer Infrared Spectrograph spectra and equivalent photometry. A potential factor of 2 improvement could be realized with suitable 5.5 μm and 10 μm photometry, such as what may be provided in the future by the James Webb Space Telescope. The resulting technique is then applied to mid-infrared photometry for the 258 galaxies from the Local Volume Legacy (LVL) survey, a large sample dominated in number by low-luminosity dwarf galaxies for which obtaining comparable mid-infrared spectroscopy is not feasible. We find the total LVL luminosity due to five strong aromatic features in the 8 μm complex to be 2.47 x 10 10 L sun with a mean volume density of 8.8 x 10 6 L sun Mpc -3 . Twenty-four of the LVL galaxies, corresponding to a luminosity cut at M B = -18.22, account for 90% of the aromatic luminosity. Using oxygen abundances compiled from the literature for 129 of the 258 LVL galaxies, we find a correlation between metallicity and the aromatic-to-total infrared emission ratio but not the aromatic-to-total 8 μm dust emission ratio. A possible explanation is that metallicity plays a role in the abundance of aromatic molecules relative to the total dust content, but other factors, such as star formation and/or the local radiation field, affect the excitation of those molecules.

  17. The leguminous species Anthyllis vulneraria as a Zn-hyperaccumulator and eco-Zn catalyst resources.

    Science.gov (United States)

    Grison, Claire M; Mazel, Marine; Sellini, Amandine; Escande, Vincent; Biton, Jacques; Grison, Claude

    2015-04-01

    Anthyllis vulneraria was highlighted here as a Zn-hyperaccumulator for the development of a pilot phytoextraction process in the mine site of Les Avinières in the district of Saint-Laurent-Le-Minier. A. vulneraria appeared to hyperaccumulate the highest concentration of Zn in shoots with a better metal selectivity relative to Cd and Pb than the reference Zn-hyperaccumulator Noccea caerulescens. A bigger biomass production associated to a higher Zn concentration conducted A. vulneraria to the highest total zinc gain per hectare per year. As a legume, A. vulneraria was infected by rhizobia symbionts. Inoculation of A. vulneraria seeds showed a positive impact on Zn hyperaccumulation. A large-scale culture process of symbiotic rhizobia of A. vulneraria was investigated and optimized to allow large-scale inoculation process. Contaminated shoots of A. vulneraria were not considered as wastes and were recovered as Eco-Zn catalyst in particular, examples of organic synthesis, electrophilic aromatic substitution. Eco-Zn catalyst was much more efficient than conventional catalysts and allowed greener chemical processes.

  18. 1,2-HOIQO--A highly versatile 1,2-HOPO analog

    Energy Technology Data Exchange (ETDEWEB)

    Seitz, Michael; Pluth, Michael D.; Raymond, Kenneth N.

    2006-08-07

    A cyclic, bidentate hydroxamic acid binding unit based on an isoquinoline scaffold has been utilized for the synthesis of a hexadentate tripodal ligand based on the TREN backbone. This prototype for a new class of multidentate chelators forms mononuclear iron(III) complexes and one-dimensional coordination polymers with lanthanide(III) cations. The latter has been determined by single crystal X-ray analysis of the cerium species. The solid state structure in the monoclinic space group P2{sub 1}/c (C{sub 36}H{sub 34}CeN{sub 7}O{sub 11}, a = 12.341(2){angstrom}, b = 26.649(4){angstrom}, c = 10.621(2){angstrom}, {alpha} = {gamma} = 90{sup o}, {beta} = 96.753(3){sup o}, V = 3468.6(9) {angstrom}{sup 3}, Z = 4) exhibits a trigonal-dodecahedral environment around the cerium cation. The proof of concept for the versatility of the new scaffold has been shown by the modification of the crucial precursor 3-carboxyiso-coumarin through electrophilic aromatic substitutions to yield the corresponding chlorosulfonated and nitrated analogs.

  19. Radioiodination of humic substances

    Energy Technology Data Exchange (ETDEWEB)

    Franke, K.; Kupsch, H. [Inst. of Interdisciplinary Isotope Research, Leipzig (Germany)

    2010-07-01

    The known IODO-GEN trademark -method was adapted for radiolabeling of humic and fulvic acids with {sup 131}I. The water insoluble oxidizing agent 1,3,4,6tetrachloro-3{alpha},6{alpha}-diphenylglycoluril (IODO-GEN trademark) forms an iodous ion species (I{sup +}), which undergoes an electrophilic I/H-substitution on aromatic moieties of the humic and fulvic acids. This method offers mild conditions with a lesser extent of oxidative alterations of the target molecule, accompanied by an easy handling due to the virtual water-insolubility of the oxidizing agent. The method was optimized and different techniques were tested for the purification of the radioiodinated humic material. The yield of the labeling procedure varies between 45 and 75% depending on the provenance of the humic material and the applied purification method. A specific activity up to 40 MBq/mg was achieved. Furthermore, the known inherent photo-susceptibility of the iodinated humic substance and the influence of reducing agents were verified. An additional release of {sup 131}I up to 20% and up to 35%, respectively were observed. (orig.)

  20. New radioiodinated carboxylic and hydroxamic matrix metalloproteinase inhibitor tracers as potential tumor imaging agents

    Energy Technology Data Exchange (ETDEWEB)

    Oltenfreiter, Ruth E-mail: ruth.oltenfreiter@rug.ac.be; Staelens, Ludovicus; Lejeune, Annabelle; Dumont, Filip; Frankenne, Francis; Foidart, Jean-Michel; Slegers, Guido

    2004-05-01

    Several studies have demonstrated a positive correlation between tumor progression and expression of extracellular proteinases such as matrix metalloproteinases (MMPs). MMP-2 and MMP-9 have become attractive targets for cancer research because of their increased expression in human malignant tumor tissues of various organs, providing a target for medical imaging techniques. Radioiodinated carboxylic and hydroxamic MMP inhibitors 2-(4'-[{sup 123}I]iodo-biphenyl-4-sulfonylamino)-3-(1H-indol-3-yl)-propionic acid (9) and 2-(4'-[{sup 123}I]iodo-biphenyl-4-sulfonylamino)-3-(1H-indol-3-yl)-propionamide (11) were synthesized by electrophilic aromatic substitution of the tributylstannyl derivatives and resulted in radiochemical yields of 60% {+-} 5% (n = 3) and 70% {+-} 5% (n = 6), respectively. In vitro zymography and enzyme assays showed high inhibition capacities of the inhibitors on gelatinases. In vivo biodistribution showed no long-term accumulation in organs and the possibility to accumulate in the tumor. These results warrant further studies of radioiodinated carboxylic and hydroxamic MMP inhibitor tracers as potential SPECT tumor imaging agents.

  1. New radioiodinated carboxylic and hydroxamic matrix metalloproteinase inhibitor tracers as potential tumor imaging agents

    International Nuclear Information System (INIS)

    Oltenfreiter, Ruth; Staelens, Ludovicus; Lejeune, Annabelle; Dumont, Filip; Frankenne, Francis; Foidart, Jean-Michel; Slegers, Guido

    2004-01-01

    Several studies have demonstrated a positive correlation between tumor progression and expression of extracellular proteinases such as matrix metalloproteinases (MMPs). MMP-2 and MMP-9 have become attractive targets for cancer research because of their increased expression in human malignant tumor tissues of various organs, providing a target for medical imaging techniques. Radioiodinated carboxylic and hydroxamic MMP inhibitors 2-(4'-[ 123 I]iodo-biphenyl-4-sulfonylamino)-3-(1H-indol-3-yl)-propionic acid (9) and 2-(4'-[ 123 I]iodo-biphenyl-4-sulfonylamino)-3-(1H-indol-3-yl)-propionamide (11) were synthesized by electrophilic aromatic substitution of the tributylstannyl derivatives and resulted in radiochemical yields of 60% ± 5% (n = 3) and 70% ± 5% (n = 6), respectively. In vitro zymography and enzyme assays showed high inhibition capacities of the inhibitors on gelatinases. In vivo biodistribution showed no long-term accumulation in organs and the possibility to accumulate in the tumor. These results warrant further studies of radioiodinated carboxylic and hydroxamic MMP inhibitor tracers as potential SPECT tumor imaging agents

  2. Synthesis and Characterization of C-Cinnamal Calix [4] Resorsinarena from Cinnamon Oil Waste West Sumatra

    Science.gov (United States)

    Etika, S. B.; Nasra, E.; Rilaztika, I.

    2018-04-01

    Synthesis and characterization of compound C-Cinnamal Calix [4] Resorsinarena (CCCR) of cinnamon oil waste have been done. This study was aimed to synthesis and characterize C-Cinnamal Calix [4] Resorsinarena from cinnamaldehyde violated cinnamon oil waste. C-Cinnamal Calix [4] Resorsinarena was synthesized by electrophilic substitution reaction of cinnamaldehyde isolated by the acid and resorcinol at 77oC temperature for 2 hour. The data analysis spectrum UV-VIS and FT-IR showed that the compound isolated cinnamaldehyde same as pure cinnamaldehyde compound. The characterization of C-Cinnamal Calix [4] Resorsinarena in the form of reddish-colored solids with melting point 3580C by using UV-VIS showed the presence of double bond, FT-IR showed the absorption at the wave number 3323,94 cm-1 indicating the ‑OH group, the wave number 1610,94 cm-1 showed the vibration C=C, the strong region absorption of 1500,86 cm-1 indicating the presence of an aromatic ring, the at 1442,88 cm-1 wave number indicating the presence of CH3.

  3. Friedel-Crafts Crosslinked Highly Sulfonated Polyether Ether Ketone (SPEEK) Membranes for a Vanadium/Air Redox Flow Battery.

    Science.gov (United States)

    Merle, Géraldine; Ioana, Filipoi Carmen; Demco, Dan Eugen; Saakes, Michel; Hosseiny, Seyed Schwan

    2013-12-30

    Highly conductive and low vanadium permeable crosslinked sulfonated poly(ether ether ketone) (cSPEEK) membranes were prepared by electrophilic aromatic substitution for a Vanadium/Air Redox Flow Battery (Vanadium/Air-RFB) application. Membranes were synthesized from ethanol solution and crosslinked under different temperatures with 1,4-benzenedimethanol and ZnCl2 via the Friedel-Crafts crosslinking route. The crosslinking mechanism under different temperatures indicated two crosslinking pathways: (a) crosslinking on the sulfonic acid groups; and (b) crosslinking on the backbone. It was observed that membranes crosslinked at a temperature of 150 °C lead to low proton conductive membranes, whereas an increase in crosslinking temperature and time would lead to high proton conductive membranes. High temperature crosslinking also resulted in an increase in anisotropy and water diffusion. Furthermore, the membranes were investigated for a Vanadium/Air Redox Flow Battery application. Membranes crosslinked at 200 °C for 30 min with a molar ratio between 2:1 (mol repeat unit:mol benzenedimethanol) showed a proton conductivity of 27.9 mS/cm and a 100 times lower VO2+ crossover compared to Nafion.

  4. Synthesis of 4-Methylene-2-cyclohexenones and Their Aromatization Reaction toward para-Methoxylmethyl Anisole Derivatives

    International Nuclear Information System (INIS)

    Lee, Jeong Mi; Lee, Ka Young; Kim, Jae Nyoung

    2004-01-01

    We and other groups have reported the selective introduction of nucleophiles at the secondary benzylic position of the Baylis-Hillman acetates via the corresponding DABCO salts. Thus, we envisioned that we could prepare 4-methylene- 2-cyclohexenone skeleton and para-methoxymethyl anisoles by combining the DABCO salt concept and the aromatization reaction with iodine in methanol. Suitably substituted anisoles are useful as the starting materials for the fragrances, dyes and pesticides, as antioxidants in oils and fats, or as stabilizers of plastics. Moreover, paramethoxymethyl anisoles have been used for the kinetic acetalization of diol or amino alcohol systems in the presence of DDQ5 during the synthesis of (+)-FR900482, taxotere side chain,5c cyclopropyl lactone oxylipins, and erythromycin A.

  5. Fused aromatic thienopyrazines: structure, properties and function

    KAUST Repository

    Mondal, Rajib; Ko, Sangwon; Bao, Zhenan

    2010-01-01

    Recent development of a fused aromatic thieno[3.4-b]pyrazine system and their application in optoelectronic devices are reviewed. Introduction of a fused aromatic unit followed by side chain engineering, dramatically enhanced the charge carrier

  6. A method of refining aromatic hydrocarbons from coal chemical production

    Energy Technology Data Exchange (ETDEWEB)

    Zieborak, K.; Koprowski, A.; Ratajczak, W.

    1979-10-01

    A method is disclosed for refining aromatic hydrocarbons of coal chemical production by contact of liquid aromatic hydrocarbons and their mixtures with a strongly acid macroporous sulfocationite in the H-form at atmospheric pressure and high temperature. The method is distinguished in that the aromatic hydrocarbons and their mixtures, from which alkali compounds have already been removed, are supplied for refinement with the sulfocationite with simultaneous addition of olefin derivatives of aromatic hydrocarbons, followed by separation of pure hydrocarbons by rectification. Styrene or alpha-methylstyrene is used as the olefin derivatives of the aromatic hydrocarbons. The method is performed in several stages with addition of olefin derivatives of aromatic hydrocarbons at each stage.

  7. Design, synthesis and evaluation of aromatic heterocyclic derivatives as potent antifungal agents.

    Science.gov (United States)

    Zhao, Shizhen; Zhang, Xiangqian; Wei, Peng; Su, Xin; Zhao, Liyu; Wu, Mengya; Hao, Chenzhou; Liu, Chunchi; Zhao, Dongmei; Cheng, Maosheng

    2017-09-08

    To further enhance the anti-Aspergillus efficacy of our previously discovered antifungal lead compounds (1), a series of aromatic heterocyclic derivatives were designed, synthesized and evaluated for in vitro antifungal activity. Many of the target compounds showed good inhibitory activity against Candida albicans and Cryptococcus neoformans. In particular, the isoxazole nuclei were more suited for improving the activity against Aspergillus spp. Among these compounds, 2-F substituted analogues 23g and 23h displayed the most remarkable in vitro activity against Candida spp., C. neoformans, A. fumigatus and fluconazole-resistant C.alb. strains, which is superior or comparable to the activity of the reference drugs fluconazole and voriconazole. Notably, the compounds 23g and 23h exhibited low inhibition profiles for various isoforms of human cytochrome P450 and excellent blood plasma stability. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

  8. International congress on aromatic and medicinal plants

    International Nuclear Information System (INIS)

    2009-01-01

    Full Text : In Morocco, medicinal and aromatic plants occupy an important place in the traditional care system of a large number of local people. They are also economically strong potential, but unfortunately they are not valued enough. Indeed, Morocco by its privileged geographical position in the Mediterranean basin and its floristic diversity (with a total of over 4,200 species and subspecies of which over 500 are recognized as medicinal and aromatic plants), is a leading provider of traditional global market. In this context and given the back label of the natural global, group research and studies on Aromatic and Medicinal Plants (GREPAM), the Faculty of Semlalia and University Cadi Ayyad, organize: the International Congress on Medicinal and Aromatic Plants CIPAM 2009. The organization of this conference is part of scientific research developed by the GREPAM. [fr

  9. Hexacoordinate bonding and aromaticity in silicon phthalocyanine.

    Science.gov (United States)

    Yang, Yang

    2010-12-23

    Si-E bondings in hexacoordinate silicon phthalocyanine were analyzed using bond order (BO), energy partition, atoms in molecules (AIM), electron localization function (ELF), and localized orbital locator (LOL). Bond models were proposed to explain differences between hexacoordinate and tetracoordinate Si-E bondings. Aromaticity of silicon phthalocyanine was investigated using nucleus-independent chemical shift (NICS), harmonic oscillator model of aromaticity (HOMA), conceptual density functional theory (DFT), ring critical point (RCP) descriptors, and delocalization index (DI). Structure, energy, bonding, and aromaticity of tetracoordinate silicon phthalocyanine were studied and compared with hexacoordinate one.

  10. 40 CFR 721.5762 - Aromatic aldehyde phenolic resin (generic).

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Aromatic aldehyde phenolic resin... Specific Chemical Substances § 721.5762 Aromatic aldehyde phenolic resin (generic). (a) Chemical substance... aromatic aldehyde phenolic resin (PMN P-01-573) is subject to reporting under this section for the...

  11. Literature Survey and Further Studies on the 3-Alkylation of N-Unprotected 3-Monosubstituted Oxindoles. Practical Synthesis of N-Unprotected 3,3-Disubstituted Oxindoles and Subsequent Transformations on the Aromatic Ring.

    Science.gov (United States)

    Kókai, Eszter; Simig, Gyula; Volk, Balázs

    2016-12-26

    The paper provides a comprehensive review of the base-catalysed C3-alkylation of N-unprotected-3-monosubstituted oxindoles. Based on a few, non-systematic studies described in the literature using butyllithium as the deprotonating agent, an optimized method has now been elaborated, via the corresponding lithium salt, for the selective C3-alkylation of this family of compounds. The optimal excess of butyllithium and alkylating agent, and the role of the halogen atom in the latter (alkyl bromides vs. iodides) were also studied. The alkylation protocol has also been extended to some derivatives substituted at the aromatic ring. Finally, various substituents were introduced into the aromatic ring of the N-unprotected 3,3-dialkyloxindoles obtained by this optimized method.

  12. Literature Survey and Further Studies on the 3-Alkylation of N-Unprotected 3-Monosubstituted Oxindoles. Practical Synthesis of N-Unprotected 3,3-Disubstituted Oxindoles and Subsequent Transformations on the Aromatic Ring

    Directory of Open Access Journals (Sweden)

    Eszter Kókai

    2016-12-01

    Full Text Available The paper provides a comprehensive review of the base-catalysed C3-alkylation of N-unprotected-3-monosubstituted oxindoles. Based on a few, non-systematic studies described in the literature using butyllithium as the deprotonating agent, an optimized method has now been elaborated, via the corresponding lithium salt, for the selective C3-alkylation of this family of compounds. The optimal excess of butyllithium and alkylating agent, and the role of the halogen atom in the latter (alkyl bromides vs. iodides were also studied. The alkylation protocol has also been extended to some derivatives substituted at the aromatic ring. Finally, various substituents were introduced into the aromatic ring of the N-unprotected 3,3-dialkyloxindoles obtained by this optimized method.

  13. Aromatic VOCs global influence in the ozone production

    Science.gov (United States)

    Cabrera-Perez, David; Pozzer, Andrea

    2016-04-01

    Aromatic hydrocarbons are a subgroup of Volatile Organic Compounds (VOCs) of special interest in the atmosphere of urban and semi-urban areas. Aromatics form a high fraction of VOCs, are highly reactive and upon oxidation they are an important source of ozone. These group of VOCs are released to the atmosphere by processes related to biomass burning and fossil fuel consumption, while they are removed from the atmosphere primarily by OH reaction and by dry deposition. In addition, a branch of aromatics (ortho-nitrophenols) produce HONO upon photolysis, which is responsible of certain amount of the OH recycling. Despite their importance in the atmosphere in anthropogenic polluted areas, the influence of aromatics in the ozone production remains largely unknown. This is of particular relevance, being ozone a pollutant with severe side effects on air quality, health and climate. In this work the atmospheric impacts at global scale of the most emitted aromatic VOCs in the gas phase (benzene, toluene, xylenes, ethylbenzene, styrene, phenol, benzaldehyde and trimethylbenzenes) are analysed and assessed. Specifically, the impact on ozone due to aromatic oxidation is estimated, as this is of great interest in large urban areas and can be helpful for developing air pollution control strategies. Further targets are the quantification of the NOx loss and the OH recycling due to aromatic oxidation. In order to investigate these processes, two simulations were performed with the numerical chemistry and climate simulation ECHAM/MESSy Atmospheric Chemistry (EMAC) model. The simulations compare two cases, one with ozone concentrations when aromatics are present or the second one when they are missing. Finally, model simulated ozone is compared against a global set of observations in order to better constrain the model accuracy.

  14. Recent Advances in Microbial Production of Aromatic Chemicals and Derivatives.

    Science.gov (United States)

    Noda, Shuhei; Kondo, Akihiko

    2017-08-01

    Along with the development of metabolic engineering and synthetic biology tools, various microbes are being used to produce aromatic chemicals. In microbes, aromatics are mainly produced via a common important precursor, chorismate, in the shikimate pathway. Natural or non-natural aromatics have been produced by engineering metabolic pathways involving chorismate. In the past decade, novel approaches have appeared to produce various aromatics or to increase their productivity, whereas previously, the targets were mainly aromatic amino acids and the strategy was deregulating feedback inhibition. In this review, we summarize recent studies of microbial production of aromatics based on metabolic engineering approaches. In addition, future perspectives and challenges in this research area are discussed. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Irreversible endo-Selective Diels–Alder Reactions of Substituted Alkoxyfurans: A General Synthesis of endo-Cantharimides

    Science.gov (United States)

    Foster, Robert W; Benhamou, Laure; Porter, Michael J; Bučar, Dejan-Krešimir; Hailes, Helen C; Tame, Christopher J; Sheppard, Tom D

    2015-01-01

    The [4+2] cycloaddition of 3-alkoxyfurans with N-substituted maleimides provides the first general route for preparing endo-cantharimides. Unlike the corresponding reaction with 3H furans, the reaction can tolerate a broad range of 2-substitued furans including alkyl, aromatic, and heteroaromatic groups. The cycloaddition products were converted into a range of cantharimide products with promising lead-like properties for medicinal chemistry programs. Furthermore, the electron-rich furans are shown to react with a variety of alternative dienophiles to generate 7-oxabicyclo[2.2.1]heptane derivatives under mild conditions. DFT calculations have been performed to rationalize the activation effect of the 3-alkoxy group on a furan Diels–Alder reaction. PMID:25756502

  16. Analogs of solid nanoparticles as precursors of aromatic hydrocarbons

    Science.gov (United States)

    Gadallah, K. A. K.; Mutschke, H.; Jäger, C.

    2013-06-01

    Context. Aromatic =CH and C=C vibrational bands have been observed within shocked interstellar regions, indicating the presence of aromatic emission carriers such as PAHs, which may have been created from adjacent molecular cloud material by interaction with a shock front. Aims: We investigate the evolution of the aromatic =CH and C=C vibrational modes at 3.3 and 6.2 μm wavelength in heated HAC materials, PAHs and mixed PAHs and HACs, respectively, aiming at an explanation of the evolution of carbonaceous dust grains in the shocked regions. Methods: Materials used in these analogs (HAC and PAH materials) were prepared by the laser ablation and the laser pyrolysis methods, respectively. The transmission electron microscopy (TEM) in high-resolution mode was used as an analytical technique to characterize the aromatic layers in HACs. Spectroscopic analysis was prformed in the mid-IR range. Results: A remarkable destruction of aliphatic structures in HACs has been observed with the thermal processing, while aromatic structures become dominating by increasing the diameters of the graphene layers. The aromatic bands at 3.3 and 6.2 μm, observed in the laboratory spectra of PAHs and of the combination of the PAHs and HAC materials, are also clearly observed in the spectrum of the heated HACs. These bands agree with those of aromatic bands observed in astronomical observations. Conclusions: Aromatization of HACs could be a pre-stage in the decomposition process of hydrocarbons that form PAH-clusters in such hot interstellar medium.

  17. Synthesis and Antibacterial Activities of Novel 2,5-Diphenylindolo[2,3-e] Pyrazolo[1',5':3",4"]pyrimido[2",1"-c] [1,2,4]triazines

    Directory of Open Access Journals (Sweden)

    Mohamed G. Marei

    2011-12-01

    Full Text Available The formation of (E-3-{2-(2,5-diphenylpyrazolo[1,5-c]pyrimidin-7-ylhydrazono}indolin-2-ones 3 has been achieved by condensation of equimolar amounts of 7-hydrazino-2,5-diphenylpyrazolo[1,5-c]pyrimidine (1 and isatin (or isatin derivatives 2 at room temperature. The (E-products could be isomerized into corresponding the (Z-3 isomers. Reactions of the latter fused heterocyclic hydrazones towards different electro-philic reagents yielded the corresponding 3-substituted derivatives 4–7. Dehydrative cyclisation of the hydrazones 3 using phosphorus oxychloride afforded the 2,5-diphenyl- indolo[2,3-e]pyrazolo[1',5':3",4"]pyrimido[2",1"-c][1,2,4] triazines 13. The polyfused heterocyclic ring system 13 underwent electrophilic substitution reactions at position 4 rather than at position 3. The 3-bromo isomer of 17 was prepared by a sequence of reactions starting from 2,5-diphenylpyrazolo[1,5-c]pyrimidine-7(6H-thione (11. The orientation of the electrophilic attack was supported by spectroscopic and chemical evidence. Some of the synthesized compounds were found to possess slight to moderate activity against the microorganisms Bacillus subtilis, Micrococcus luteus, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa.

  18. Detection of chlorinated aromatic compounds

    Science.gov (United States)

    Ekechukwu, A.A.

    1996-02-06

    A method for making a composition for measuring the concentration of chlorinated aromatic compounds in aqueous fluids, and an optical probe for use with the method are disclosed. The composition comprises a hydrophobic polymer matrix, preferably polyamide, with a fluorescent indicator uniformly dispersed therein. The indicator fluoresces in the presence of the chlorinated aromatic compounds with an intensity dependent on the concentration of these compounds in the fluid of interest, such as 8-amino-2-naphthalene sulfonate. The probe includes a hollow cylindrical housing that contains the composition in its distal end. The probe admits an aqueous fluid to the probe interior for exposure to the composition. An optical fiber transmits excitation light from a remote source to the composition while the indicator reacts with chlorinated aromatic compounds present in the fluid. The resulting fluorescence light signal is reflected to a second optical fiber that transmits the light to a spectrophotometer for analysis. 5 figs.

  19. Toxicological risk at workplace and toxicity as Life Cycle Assessment impact category: Substitution of solvents as an example.

    Science.gov (United States)

    Schupp, Thomas; Georg, Philipp Alexander; Kirstein, Guenter

    2017-01-01

    Substitution of hazardous substances against less hazardous ones is a central requirement of the European Chemical Regulation REACH (European Regulation 1907/2006/EC). Hazardous substances emitted from products may not only affect the worker; drift off and distribution in the environment may finally result in exposure of the general population. This potential threat to health is covered by the impact category "toxicity" in Life Cycle Assessments. In this paper, we present a case of a substitution of volatile organic compounds in a reactive varnish, and compare the "old" formulation with the "new" formulation against health risk to the worker, and concerning the Life Cycle Assessment impact category "toxicity". The "old" formulation contained Naphtha (petroleum), hydrodesulfurized, heavy and Solvent naphtha (petroleum), light, aromatic. In the new formulation, both naphthas were replaced by n-Butylacetate, 1-Ethoxy-2-propyl acetate and Ethyl-3-ethoxy propionate. In the European Union, the naphthas are classified as mutagens and carcinogens category 1, officially. However, if benzene is below 0.1 %, registrants in the EU proposed to omit this classification, and todays naptha products on the market obviously have benzene contents below 0.1 %. On a first glance, the improvement for workplace safety introduced by the substitution, therefore, is comparatively small, as it is for toxicity in Life Cycle Assessment. However, when background knowledge concerning chemical production processes of naphtha is included, benzene below a content of 0.1 % needs to be taken into consideration, and the benefit of substitution is more obvious.

  20. Novel Cholinesterase Inhibitors Based on O-Aromatic N,N-Disubstituted Carbamates and Thiocarbamates

    Directory of Open Access Journals (Sweden)

    Martin Krátký

    2016-02-01

    Full Text Available Based on the presence of carbamoyl moiety, twenty salicylanilide N,N-disubstituted (thiocarbamates were investigated using Ellman’s method for their ability to inhibit acetylcholinesterase (AChE and butyrylcholinesterase (BChE. O-Aromatic (thiocarbamates exhibited weak to moderate inhibition of both cholinesterases with IC50 values within the range of 1.60 to 311.0 µM. IC50 values for BChE were mostly lower than those obtained for AChE; four derivatives showed distinct selectivity for BChE. All of the (thiocarbamates produced a stronger inhibition of AChE than rivastigmine, and five of them inhibited BChE more effectively than both established drugs rivastigmine and galantamine. In general, 5-chloro-2-hydroxy-N-[4-(trifluoromethyl-phenyl]benzamide, 2-hydroxy-N-phenylbenzamide as well as N-methyl-N-phenyl carbamate derivatives led to the more potent inhibition. O-{4-Chloro-2-[(4-chlorophenylcarbamoyl]phenyl} dimethylcarbamothioate was identified as the most effective AChE inhibitor (IC50 = 38.98 µM, while 2-(phenylcarbamoylphenyl diphenylcarbamate produced the lowest IC50 value for BChE (1.60 µM. Results from molecular docking studies suggest that carbamate compounds, especially N,N-diphenyl substituted representatives with considerable portion of aromatic moieties may work as non-covalent inhibitors displaying many interactions at peripheral anionic sites of both enzymes. Mild cytotoxicity for HepG2 cells and consequent satisfactory calculated selectivity indexes qualify several derivatives for further optimization.

  1. Protonation sites of aromatic compounds in (+) atmospheric pressure photoionization

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sung Hwan; Ahmed, Arif [Dept. of Chemistry, Kyungpoo k National University, Daegu (Korea, Republic of)

    2017-02-15

    Reaction enthalpy of hydrogen transfer reactions of aromatic compounds has been observed to be greatly affected by the exact location of the protonation site. Therefore, to clearly identify the protonation location, each candidate protonation site for 43 aromatic compounds were theoretically determined and their location was compared with that determined based on experimental MS data. Only the basic nitrogen atom is favorable as a protonation site for pyridine-type aromatic compounds, whereas carbon atoms are preferable for the protonation of pyrrole-type compounds. The most favorable protonation sites for aniline or methylated aniline-type aromatic compounds are either the nitrogen atom in the amine group or the carbon atom at the para-position to the amine group. Like pyrrole-type compounds, aromatic compounds with amine groups also favor protonation at the carbon atom instead of at the nitrogen atom. In addition, hydrocarbons having an anthracene structural motif without heteroatoms produced higher or equal percentages of protonated ions compared to that achieved with molecular ions. The results of this study can be used to improve the analyses of aromatic compounds.

  2. Hydroalumination of Ketenimines and Subsequent Reactions with Heterocumulenes: Synthesis of Unsaturated Amide Derivatives and 1,3-Diimines.

    Science.gov (United States)

    Jin, Xing; Willeke, Matthias; Lucchesi, Ralph; Daniliuc, Constantin-Gabriel; Fröhlich, Roland; Wibbeling, Birgit; Uhl, Werner; Würthwein, Ernst-Ulrich

    2015-06-19

    The series of differently substituted ketenimines 1 was hydroluminated using di-iso-butyl aluminum hydride. For the sterically congested ketenimine 1a, preferred hydroalumination of the C═N-bond was proven by X-ray crystallography (compound 5a). In situ treatment of the hydroaluminated ketenimines 5 with various heterocumulenes like carbodiimides, isocycanates, isothiocyanates and ketenimines as electrophiles and subsequent hydrolytic workup resulted in novel enamine derived amide species in case of N-attack (sterically less hindered ketenimines) under formation of a new C-N-bond or in 1,3-diimines by C-C-bond-formation in case of bulky substituents at the ketenimine-nitrogen atom. Furthermore, domino reactions with more than 1 equiv of the electrophile or by subsequent addition of two different electrophiles are possible and lead to polyfunctional amide derivatives of the biuret type which are otherwise not easily accessible.

  3. The mutagenic potential of high flash aromatic naphtha.

    Science.gov (United States)

    Schreiner, C A; Edwards, D A; McKee, R H; Swanson, M; Wong, Z A; Schmitt, S; Beatty, P

    1989-06-01

    Catalytic reforming is a refining process that converts naphthenes to aromatics by dehydrogenation to make higher octane gasoline blending components. A portion of this wide boiling range hydrocarbon stream can be separated by distillation and used for other purposes. One such application is a mixture of predominantly 9-carbon aromatic molecules (C9 aromatics, primarily isomers of ethyltoluene and trimethylbenzene), which is removed and used as a solvent--high-flash aromatic naphtha. A program was initiated to assess the toxicological properties of high-flash aromatic naphtha since there may be human exposure through inhalation or external body contact. The current study was conducted partly to assess the potential for mutagenic activity and also to assist in an assessment of carcinogenic potential. The specific tests utilized included the Salmonella/mammalian microsome mutagenicity assay, the hypoxanthine-guanine phosphoribosyl transferase (HGPRT) forward mutation assay in CHO cells, in vitro chromosome aberration and sister chromatid exchange (SCE) assays in CHO cells, and an in vivo chromosome aberration assay in rat bone marrow.

  4. Effects of halogenated aromatics/aliphatics and nitrogen(N)-heterocyclic aromatics on estimating the persistence of future pharmaceutical compounds using a modified QSAR model.

    Science.gov (United States)

    Lim, Seung Joo; Fox, Peter

    2014-02-01

    The effects of halogenated aromatics/aliphatics and nitrogen(N)-heterocyclic aromatics on estimating the persistence of future pharmaceutical compounds were investigated using a modified half life equation. The potential future pharmaceutical compounds investigated were approximately 2000 pharmaceutical drugs currently undergoing the United States Food and Drug Administration (US FDA) testing. EPI Suite (BIOWIN) model estimates the fates of compounds based on the biodegradability under aerobic conditions. While BIOWIN considered the biodegradability of a compound only, the half life equation used in this study was modified by biodegradability, sorption and cometabolic oxidation. It was possible that the potential future pharmaceutical compounds were more accurately estimated using the modified half life equation. The modified half life equation considered sorption and cometabolic oxidation of halogenated aromatic/aliphatics and nitrogen(N)-heterocyclic aromatics in the sub-surface, while EPI Suite (BIOWIN) did not. Halogenated aliphatics in chemicals were more persistent than halogenated aromatics in the sub-surface. In addition, in the sub-surface environment, the fates of organic chemicals were much more affected by halogenation in chemicals than by nitrogen(N)-heterocyclic aromatics. © 2013.

  5. Deuteration of acetanilides and other substituted aromatics using [Ir(COD)(Cy3P)(Py)]PF6 as catalyst

    International Nuclear Information System (INIS)

    Hesk, D.; Das, P.R.; Evans, B.

    1995-01-01

    Deuterium exchange labelling using [Ir(COD)(Cy 3 P)(Py)]PF 6 as catalyst and deuterium gas was studied on a number of substituted acetanilides. In most cases products containing deuterium ortho to the anilide group were obtained with a high degree of enrichment. With one exception no evidence for meta, para or anilide methyl labelling was seen. The catalyst was also effective in the ortho deuteration of acetophenone, benzophenone and the β-lactam containing compound Sch 48461. (Author)

  6. Polymethylated [Fe(eta(6)-arene)(2)](2+) dications: methyl-group rearrangements and application of the EINS mechanism

    Czech Academy of Sciences Publication Activity Database

    Štíbr, Bohumil; Bakardjiev, Mario; Hájková, Zuzana; Holub, Josef; Padělková, Z.; Růžička, A.; Kennedy, J.D.

    2011-01-01

    Roč. 40, č. 22 (2011), s. 5916-5920 ISSN 1477-9226 R&D Projects: GA MŠk LC523 Institutional research plan: CEZ:AV0Z40320502 Keywords : electrophile-induced nucleophilic substitution Subject RIV: CA - Inorganic Chemistry Impact factor: 3.838, year: 2011

  7. One-pot synthesis of 4′-alkyl-4-cyanobiaryls on the basis of the terephthalonitrile dianion and neutral aromatic nitrile cross-coupling

    Directory of Open Access Journals (Sweden)

    Roman Yu. Peshkov

    2016-07-01

    Full Text Available A convenient one-pot approach to alkylcyanobiaryls is described. The method is based on biaryl cross-coupling between the sodium salt of the terephthalonitrile dianion and a neutral aromatic nitrile in liquid ammonia, and successive alkylation of the long-lived anionic intermediate with alkyl bromides. The reaction is compatible with benzonitriles that contain methyl, methoxy and phenyl groups, fluorine atoms, and a 1-cyanonaphthalene residue. The variety of ω-substituted alkyl bromides, including an extra bromine atom, a double bond, cyano and ester groups, as well as a 1,3-dioxane fragment are suitable as alkylation reagents.

  8. Aromatic Plants as a Source of Bioactive Compounds

    Directory of Open Access Journals (Sweden)

    Panagiota Florou-Paneri

    2012-09-01

    Full Text Available Aromatic plants, also known as herbs and spices, have been used since antiquity as folk medicine and as preservatives in foods. The best known aromatic plants, such as oregano, rosemary, sage, anise, basil, etc., originate from the Mediterranean area. They contain many biologically active compounds, mainly polyphenolics, which have been found to possess antimicrobial, antioxidant, antiparasitic, antiprotozoal, antifungal, and anti-inflammatory properties. Currently, the demand for these plants and their derivatives has increased because they are natural, eco-friendly and generally recognized as safe products. Therefore, aromatic plants and their extracts have the potential to become new generation substances for human and animal nutrition and health. The purpose of this review is to provide an overview of the literature surrounding the in vivo and in vitro use of aromatic plants.

  9. Mechanism of Oxidative Amidation of Nitroalkanes with Oxygen and Amine Nucleophiles by Using Electrophilic Iodine.

    Science.gov (United States)

    Li, Jing; Lear, Martin J; Kwon, Eunsang; Hayashi, Yujiro

    2016-04-11

    Recently, we developed a direct method to oxidatively convert primary nitroalkanes into amides that entailed mixing an iodonium source with an amine, base, and oxygen. Herein, we systematically investigated the mechanism and likely intermediates of such methods. We conclude that an amine-iodonium complex first forms through N-halogen bonding. This complex reacts with aci-nitronates to give both α-iodo- and α,α-diiodonitroalkanes, which can act as alternative sources of electrophilic iodine and also generate an extra equimolar amount of I(+) under O2. In particular, evidence supports α,α-diiodonitroalkane intermediates reacting with molecular oxygen to form a peroxy adduct; alternatively, these tetrahedral intermediates rearrange anaerobically to form a cleavable nitrite ester. In either case, activated esters are proposed to form that eventually reacts with nucleophilic amines in a traditional fashion. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Use of compound-specific stable carbon isotope ratio measurements of asphaltene-bound polycyclic aromatic hydrocarbons (PAHs) as a novel aid to source apportionment of environmental PAHs

    Energy Technology Data Exchange (ETDEWEB)

    C. Sun; C. Snape; M. Cooper; W. Ivwurie [University of Nottingham, Nottingham (United Kingdom). Nottingham Energy & Fuel Centre

    2005-07-01

    In this study, the PAHs from hydropyrolysis of asphaltenes from different primary sources (e.g. crude oil, low and high temperature coal tars) were characterized by their molecular distributions and {sup 13}C/{sup 12}C isotope ratios. It was found that for all oil samples, the molecular and isotopic profiles for their asphaltene-derived PAHs are both similar to those observed for their contained free aromatics, with {sup 13}C-isotopic values varying from -25 to -27{per_thousand} for the Nigerian and -27 to -30{per_thousand} for North Sea oil samples. For low and high temperature coal tar samples, however, similar molecular but different isotopic profiles were observed for their asphaltene-bound PAHs. The free aromatics are significantly isotopically lighter (by nearly -3{per_thousand}) than their asphaltene-derived counterparts having isotopic values typically between -22 and -23{per_thousand} for all coal tar samples examined, and this leads to a larger isotopic difference of up to 7{per_thousand} between the two sources of PAHs than that already observed between their free aromatics (3{per_thousand}). Applying these results to samples previously examined in an area where unambiguous source apportionment could not be conducted for the PAHs due to likely biodegradation, it was found that the bound PAHs released from the asphaltenes recovered from the soil samples in this area are extremely similar to low temperature tar as the source, in terms of their both molecular (highly alkylated) and isotopic profiles. The free PAHs are much less alkyl substituted confirming that the aromatics detected in this area have been subjected to intensiveenvironmental degradation with alkylated aromatic constituents being preferentially removed from their initial matrix.

  11. Synthesis of [11C]cyanoalkyltriphenylphosphoranes via [11C]cyanide substitution on haloalkylphosphonium salts

    International Nuclear Information System (INIS)

    Hoernfeldt, K.

    1994-01-01

    The synthesis of the 11 C-labelled bifunctional precursors 3-[ 11 C]cyanoethyltriphenylphosphonium bromide (1'), 4-[ 11 C]cyanopropyltriphenylphosphonium bromide (2'), 5-[ 11 C]cyanobutyltriphenylphosphonium bromide (3'), 4-[ 11 C]cyanopropyltriphenylphosphonium iodide (4') and 5-[ 11 C]cyanobutyltriphenylphosphonium iodide (5') is presented. The label was introduced using [ 11 C]cyanide in a substitution reaction on the ω-halo-alkyltriphenylphosphonium salt (bromide or iodide salt). The phosphonium salts 1'-5' were formed in 33-99% radiochemical yield in 5-10 min reaction time. After addition of epichlorohydrin as generator of base, the precursors 1-3 were formed. The potential of the intermediates 1-3 in Wittig reactions was shown in model reactions with aromatic and aliphatic aldehydes. The aromatic olefins obtained from 1'-5' were formed in 85-96% radiochemical yield, with Z/E ratios between 67/33-75/25. The aliphatic olefins were obtained in 60-78% radiochemical yield from 4' and 5'. In the reaction with 1' and an aliphatic aldehyde, the yield decreased to 5-10%. The Z/E ratios were 100/0 for the aliphatic olefins. In an experiment starting with 2,7 GBq (73 mCi) hydrogen [ 11 C]cyanide, 451 MBq (12.2 mCi) olefin from 3' and 4-nitrobenzaldehyde was obtained in 44 min from hydrogen [ 11 C]cyanide production, with a 55% decay corrected radiochemical yield, the radiochemical purity was 96%. (Author)

  12. 40 CFR 721.2577 - Copper complex of (substituted sulfonaphthyl azo substituted phenyl) disulfonaphthyl azo, amine...

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Copper complex of (substituted... Copper complex of (substituted sulfonaphthyl azo substituted phenyl) disulfonaphthyl azo, amine salt... substances identified generically as copper complex of (substituted sulfonaphthyl azo substituted phenyl...

  13. The formation of aromatics and PAH's in laminar flames

    International Nuclear Information System (INIS)

    Marinov, N M; Pitz, W J; Westbrook, C K

    1999-01-01

    The formation of aromatics and PAH's is an important problem in combustion. These compounds are believed to contribute to the formation of soot whose emission from diesel engines is regulated widely throughout the industrial world. Additionally, the United States Environmental Protection Agency regulates the emission of many aromatics and PAH species from stationary industrial burners, under the 1990 Clean Air Act Amendments. The above emission regulations have created much interest in understanding how these species are formed in combustion systems. Much previous work has been done on aromatics and PAH's. The work is too extensive to review here, but is reviewed in Reference 1. A few recent developments are highlighted here. McEnally, Pfefferle and coworkers have studied aromatic, PAH and soot formation in a variety of non-premixed flames with hydrocarbon additives[2-4]. They found additives that contain a C5 ring increase the concentration of aromatics and soot[4]. Howard and coworkers have studied the formation of aromatic and PAH's in low pressure, premixed, laminar hydrocarbon flames. They found the cyclopentadienyl radical to be a key species in naphthalene formation in a fuel-rich, benzene/Ar/O2 flame[5

  14. Bifunctional organocatalysts for the asymmetric synthesis of axially chiral benzamides

    Directory of Open Access Journals (Sweden)

    Ryota Miyaji

    2017-08-01

    Full Text Available Bifunctional organocatalysts bearing amino and urea functional groups in a chiral molecular skeleton were applied to the enantioselective synthesis of axially chiral benzamides via aromatic electrophilic bromination. The results demonstrate the versatility of bifunctional organocatalysts for the enantioselective construction of axially chiral compounds. Moderate to good enantioselectivities were afforded with a range of benzamide substrates. Mechanistic investigations were also carried out.

  15. NSAIDs as potential treatment option for preventing amyloid β toxicity in Alzheimer's disease: an investigation by docking, molecular dynamics, and DFT studies.

    Science.gov (United States)

    Azam, Faizul; Alabdullah, Nada Hussin; Ehmedat, Hadeel Mohammed; Abulifa, Abdullah Ramadan; Taban, Ismail; Upadhyayula, Sreedevi

    2018-06-01

    Aggregation of amyloid beta (Aβ) protein considered as one of contributors in development of Alzheimer's disease (AD). Several investigations have identified the importance of non-steroidal anti-inflammatory drugs (NSAIDs) as Aβ aggregation inhibitors. Here, we have examined the binding interactions of 24 NSAIDs belonging to eight different classes, with Aβ fibrils by exploiting docking and molecular dynamics studies. Minimum energy conformation of the docked NSAIDs were further optimized by density functional theory (DFT) employing Becke's three-parameter hybrid model, Lee-Yang-Parr (B3LYP) correlation functional method. DFT-based global reactivity descriptors, such as electron affinity, hardness, softness, chemical potential, electronegativity, and electrophilicity index were calculated to inspect the expediency of these descriptors for understanding the reactive nature and sites of the molecules. Few selected NSAID-Aβ fibrils complexes were subjected to molecular dynamics simulation to illustrate the stability of these complexes and the most prominent interactions during the simulated trajectory. All of the NSAIDs exhibited potential activity against Aβ fibrils in terms of predicted binding affinity. Sulindac was found to be the most active compound underscoring the contribution of indene methylene substitution, whereas acetaminophen was observed as least active NSAID. General structural requirements for interaction of NSAIDs with Aβ fibril include: aryl/heteroaryl aromatic moiety connected through a linker of 1-2 atoms to a distal aromatic group. Considering these structural requirements and electronic features, new potent agents can be designed and developed as potential Aβ fibril inhibitors for the treatment of AD.

  16. Aromatic hydrocarbon concentrations in sediments of Placentia Bay, Newfoundland

    International Nuclear Information System (INIS)

    Kiceniuk, J.W.

    1992-01-01

    A study was conducted to examine the potential for contamination of recent sediments with polycyclic aromatic hydrocarbons due to tanker and refinery activity in Placentia Bay, Newfoundland, an area without large local anthropogenic sources of aromatics. Sediment samples were taken from the vicinity of the Come By Chance refinery, Woody Island, Wild Cove, and Port Royal Arm, all in the north end of the bay. The samples were extracted by two methods, dichloromethane extraction of dried sediment for determination of total aromatic hydrocarbon content and hexane extraction of wet sediment for estimation of the bioavailability of hydrocarbons and determination of more volatile compounds. Class analysis of aromatic hydrocarbons was conducted on a NH 2 column with detection at 255 nm. Total concentrations of di-tricyclic aromatics were highest at the Woody Island site (0.6 μg/g). The sediments from the Come By Chance site, Wild Cove, and Port Royal Arm sediments contained 0.3, 0.1, and 0.2 μg/g respectively. The hexane extracts from Come By Chance were lowest in di-tricyclic aromatics (0.007 μg/g), with the other sites being equal in concentration (0.01 μg/g). It is evident from the study that aromatic hydrocarbon concentrations in Placentia Bay are elevated in some parts of the bay in the absence of local combustion sources, and that the most likely source is petroleum. 12 refs., 5 figs., 2 tabs

  17. Fused aromatic thienopyrazines: structure, properties and function

    KAUST Repository

    Mondal, Rajib

    2010-01-01

    Recent development of a fused aromatic thieno[3.4-b]pyrazine system and their application in optoelectronic devices are reviewed. Introduction of a fused aromatic unit followed by side chain engineering, dramatically enhanced the charge carrier mobility in thin film transistor devices and mobilities up to 0.2 cm2/Vs were achieved. The optoelectronic properties of these fused aromatic thienopyrazine polymers (Eg = 1.3 to 1.6 eV, HOMO = -4.9 to -5.2 V) were tuned by introduction of various fused aromatic rings within thienopyrazine. By balancing the fundamental properties of these polymers, both high charge carrier mobilities and moderate PCEs in solar cells were achieved. Further, effects of copolymerizing units are discussed. Low band gap semiconducting polymer (Eg ∼ 1 eV) with high field effect mobility (0.044 cm2/Vs) was obtained using cyclopentadithiophene as copolymerizing unit. Finally, a molecular design approach to enhance the absorption coefficients is discussed, which resulted in improved power conversion efficiency in bulk heterojunction solar cells. © 2010 The Royal Society of Chemistry.

  18. An ethnopharmacological study of aromatic Uyghur medicinal plants in Xinjiang, China.

    Science.gov (United States)

    Zhao, Lu; Tian, Shuge; Wen, E; Upur, Halmuart

    2017-12-01

    An ethnobotanical survey was completed in a remote village and surrounding country of Xinjiang, where most Uyghur medicinal plants could be collected. This work clarifies and increases ethnobotanical data. We surveyed and organized aromatic medicinal plants that are commonly used in clinical settings to provide a significant reference for studying new medical activities. In the survey, informants who have traditional knowledge on aromatic Uyghur medicinal plants were interviewed between March 2014 and September 2014. Aromatic medicinal plant species and pertinent information were collected. Some therapeutic methods and modes of preparation of traditional aromatic medicinal plants were found. A total of 86 aromatic medicinal plant species belonging to 36 families were included in our study. We identified 34 plant species introduced from different regions such as Europe, India and Mediterranean areas. Fruits and whole plants were the most commonly used parts of plant, and most aromatic medicinal plants could be applied as medicine and food. We assigned the medicinal plants a use value (UV). Knowing the UV of species is useful in determining the use reliability and pharmacological features of related plants. Xinjiang is an area in which indigenous aromatic medicinal plants are diversely used and has therefore established a sound dimensional medical healthcare treatment system. Some aromatic Uyghur medicinal plants are on the verge of extinction. Hence, further strategies for the conservation of these aromatic medicinal plants should be prioritized.

  19. Spectrofluorimetric study of the aromatic carbohydrates of Noriisk petroleum

    Energy Technology Data Exchange (ETDEWEB)

    Alekseeva, T.A.; Lekveishvili, E.G.; Melikadze, L.D.; Teplitskaia, T.A.; Tevdorashvili, M.N.

    1979-01-01

    Investigation was made of the specimens of aromatic hydrocarbons which were produced by photochemical decomposition of the products of photocondensation with maleicanhydride of narrow aromatic fractions separated by a system of methods from a high temperature part of Noriisk petroleum. Use was made of a standard spectrofluorimeter of low resolution. A series of aromatic hydrocarbons, naphthalene, benzofluorene, phenantrene, chrizene, pyrene, tetraphene, and 3,4-benzophenantrene were installed in the machine.

  20. Extraction of aromatics from naphtha with ionic liquids

    NARCIS (Netherlands)

    Meindersma, G.W.

    2005-01-01

    The objective of this study was the development of a separation technology for the selective recovery and purification of aromatic compounds benzene, toluene, ethylbenzene and xylenes (BTEX) from liquid ethylene cracker feeds. Most ethylene cracker feeds contain 10 ¿ 25% of aromatic components,

  1. Critical point measurement of some polycyclic aromatic hydrocarbons

    International Nuclear Information System (INIS)

    Nikitin, Eugene D.; Popov, Alexander P.

    2015-01-01

    Highlights: • Critical properties of five polycyclic aromatic hydrocarbons were measured. • These hydrocarbons decompose at near-critical temperatures. • Pulse-heating method with short residence times was used. - Abstract: The critical temperatures and the critical pressures of five polycyclic aromatic compounds, namely, acenaphthene, fluorene, anthracene, phenanthrene, and pyrene have been measured. All the compounds studied decompose at near-critical temperatures. A pulse-heating technique applicable to measuring the critical properties of thermally unstable compounds has been used. The times from the beginning of a heating pulse to the moment of reaching the critical temperature were from (0.06 to 0.85) ms. The short residence times provide little degradation of the substances in the course of the experiments. The experimental critical parameters of the polycyclic aromatic compounds have been compared with those estimated by five predictive methods. The acentric factors of polycyclic aromatic compounds studied have been calculated

  2. Chemical properties of 2,3-dihydro-1H-1,5-benzodiazepinone-2 derivatives – a review

    Directory of Open Access Journals (Sweden)

    Aleksandr A. Gaponov

    2014-03-01

    Full Text Available Condensed heterocyclic systems with two nitrogen atoms in the seven-membered ring – benzodiazepines and their derivatives – are interesting and important objects from both theoretical and applied point of view. They attract a lot of attention due to their potent and diverse biological activities. These compounds include numerous tranquilizers, sedatives, analgesics, as well as anticonvulsant, anti-inflammatory and anti-tumor agents. The presence of several reactive centers in 1,5-benzodiazepines leads to a variety of reactions with both electrophilic and nucleophilic agents. The first part of this review covers electrophilic substitution of 2,3-dihydro-1H-1,5-benzodiazepin-2-ones (nitration, halogenation, alkylation, acylation, formylation, etc. The data shows that the reaction outcome is determined by the nature of both the substrate and the electrophilic agent, as well as by the reaction conditions: temperature, time, and solvent. 

  3. High performance liquid chromatography of substituted aromatics with the metal-organic framework MIL-100(Fe): Mechanism analysis and model-based prediction.

    Science.gov (United States)

    Qin, Weiwei; Silvestre, Martin Eduardo; Li, Yongli; Franzreb, Matthias

    2016-02-05

    Metal-organic framework (MOF) MIL-100(Fe) with well-defined thickness was homogenously coated onto the outer surface of magnetic microparticles via a liquid-phase epitaxy method. The as-synthesized MIL-100(Fe) was used as stationary phase for high-performance liquid chromatography (HPLC) and separations of two groups of mixed aromatic hydrocarbons (toluene, styrene and p-xylene; acetanilide, 2-nirtoaniline and 1-naphthylamine) using methanol/water as mobile phase were performed to evaluate its performance. Increasing water content of the mobile phase composition can greatly improve the separations on the expense of a longer elution time. Stepwise elution significantly shortens the elution time of acetanilide, 2-nirtoaniline and 1-naphthylamine mixtures, while still achieving a baseline separation. Combining the experimental results and in-depth modeling using a recently developed chromatographic software (ChromX), adsorption equilibrium parameters, including the affinities and maximum capacities, for each analyte toward the MIL-100(Fe) are obtained. In addition, the pore diffusivity of aromatic hydrocarbons within MIL-100(Fe) was determined to be 5×10(-12)m(2)s(-1). While the affinities of MIL-100(Fe) toward the analyte molecules differs much, the maximum capacities of the analytes are in a narrow range with q*MOFmax,toluene=3.55molL(-1), q*MOFmax,styrene or p-xylene=3.53molL(-1), and q*MOFmax,anilines=3.12molL(-1) corresponding to approximately 842 toluene and 838 styrene or p-xylene, and 740 aniline molecules per MIL-100(Fe) unit cell, respectively. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Aggregation of dialkyl-substituted diphosphonic acids and its effect on metal ion extraction.

    Energy Technology Data Exchange (ETDEWEB)

    Chiarizia, R.; Barrans, R. E., Jr.; Ferraro, J. R. Herlinger, A. W.; McAlister, D. R.

    1999-10-22

    Solvent extraction reagents containing the diphosphonic acid group exhibit an extraordinary affinity for tri-, tetra- and hexavalent actinides. Their use has been considered for actinide separation and pre-concentration procedures. Solvent extraction data obtained with P,P{prime}-di(2-ethylhexyl) methane-, ethane- and butanediphosphonic acids exhibit features that are difficult to explain without Knowledge of the aggregation state of the extractants. Information about the aggregation of the dialkyl-substituted diphosphonic acids in aromatic diluents has been obtained using the complementary techniques of vapor pressure osmometry (VPO), small angle neutron scattering (SANS), infrared spectroscopy and molecular mechanics. The results from these techniques provide an understanding of the aggregation behavior of these extractants that is fully compatible with the solvent extraction data. The most important results and their relevance to solvent extraction are reviewed in this paper.

  5. Functionalization of Carbon Nanotubes via Electrophilic Substitution Reaction in Polyphosphoric Acid

    Science.gov (United States)

    2006-07-26

    single fiber. The resulting fiber bundles were chopped, collected, and washed with diluted ammonium hydroxide, and then Soxhlet -extracted with water...quantitative yield . Anal. Calcd. for C14.98H8O2: C, 81.78%; H, 3.67%. Found: C, 80.19%; H, 3.61%. 3. Results and Discussion 3.1 Characterization of MWNT...carbon nanomaterials. Furthermore, Soxhlet extractions of MWNT-g-mPEK and VGCNF- g-mPEK with dichloromethane, which is good solvent for mPEK, were

  6. Functionalization of Carbon Nanotubes via Electrophilic Substitution Reaction in Polyphosphoric Acid

    National Research Council Canada - National Science Library

    Baek, Jong-Beom

    2006-01-01

    .... Furthermore, on the basis of all supportive evidences, this work provides one of the most efficient methods to directly and uniformly grafting the surfaces of carbon nanotubes (CNT) and nanofibers (CNF...

  7. Radical cascades using enantioenriched 7-azabenzonorbornenes and their applications in synthesis

    Directory of Open Access Journals (Sweden)

    2008-10-01

    Full Text Available Tandem deoxygenation–neophyl-type radical rearrangement–electrophile trapping using xanthates from 7-azabenzonorbornadienes gives 3-exo-substituted 2-aza-5,6-benzonorbornenes, which in some cases undergo isomerisation to (aminomethylindenes. The starting xanthates are accessible in good yields and high enantiomeric ratios via asymmetric hydroboration of (aryne/pyrrole-derived 7-azabenzonorbornadienes. Oxidation (using RuO4 and Birch reduction of the 2-aza-5,6-benzonorbornenes provide access to substituted pyrrolidines and tetrahydroindenes, respectively.

  8. Ultrasound-Promoted Greener Synthesis of Novel Trifurcate 3-Substituted-chroman-2,4-dione Derivatives and Their Drug-Likeness Evaluation

    Directory of Open Access Journals (Sweden)

    Yu Xue

    2012-11-01

    Full Text Available An efficient and convenient approach for one-pot synthesis of 3-substituted chroman-2,4-diones via a three-component reaction of aromatic aldehydes, 4-hydroxy- coumarins and diverse pyrazolone derivatives was described. The combinatorial synthesis for this methodology was achieved by applying ultrasound irradiation in the absence of activator while making use of water as green solvent. Additionally, novel chroman-2,4-dione derivatives attached to an edaravone moiety represent an exploitable source of brand new anticancer agents. In comparison with conventional methods, experimental simplicity, good functional group tolerance, excellent yields, short routine, and atom efficiency are prominent features of this sonocatalyzed procedure.

  9. Anaerobic catabolism of aromatic compounds: a genetic and genomic view.

    Science.gov (United States)

    Carmona, Manuel; Zamarro, María Teresa; Blázquez, Blas; Durante-Rodríguez, Gonzalo; Juárez, Javier F; Valderrama, J Andrés; Barragán, María J L; García, José Luis; Díaz, Eduardo

    2009-03-01

    Aromatic compounds belong to one of the most widely distributed classes of organic compounds in nature, and a significant number of xenobiotics belong to this family of compounds. Since many habitats containing large amounts of aromatic compounds are often anoxic, the anaerobic catabolism of aromatic compounds by microorganisms becomes crucial in biogeochemical cycles and in the sustainable development of the biosphere. The mineralization of aromatic compounds by facultative or obligate anaerobic bacteria can be coupled to anaerobic respiration with a variety of electron acceptors as well as to fermentation and anoxygenic photosynthesis. Since the redox potential of the electron-accepting system dictates the degradative strategy, there is wide biochemical diversity among anaerobic aromatic degraders. However, the genetic determinants of all these processes and the mechanisms involved in their regulation are much less studied. This review focuses on the recent findings that standard molecular biology approaches together with new high-throughput technologies (e.g., genome sequencing, transcriptomics, proteomics, and metagenomics) have provided regarding the genetics, regulation, ecophysiology, and evolution of anaerobic aromatic degradation pathways. These studies revealed that the anaerobic catabolism of aromatic compounds is more diverse and widespread than previously thought, and the complex metabolic and stress programs associated with the use of aromatic compounds under anaerobic conditions are starting to be unraveled. Anaerobic biotransformation processes based on unprecedented enzymes and pathways with novel metabolic capabilities, as well as the design of novel regulatory circuits and catabolic networks of great biotechnological potential in synthetic biology, are now feasible to approach.

  10. Pyridoxylamine reactivity kinetics as an amine based nucleophile for screening electrophilic dermal sensitizers

    Science.gov (United States)

    Chipinda, Itai; Mbiya, Wilbes; Adigun, Risikat Ajibola; Morakinyo, Moshood K.; Law, Brandon F.; Simoyi, Reuben H.; Siegel, Paul D.

    2015-01-01

    Chemical allergens bind directly, or after metabolic or abiotic activation, to endogenous proteins to become allergenic. Assessment of this initial binding has been suggested as a target for development of assays to screen chemicals for their allergenic potential. Recently we reported a nitrobenzenethiol (NBT) based method for screening thiol reactive skin sensitizers, however, amine selective sensitizers are not detected by this assay. In the present study we describe an amine (pyridoxylamine (PDA)) based kinetic assay to complement the NBT assay for identification of amine-selective and non-selective skin sensitizers. UV-Vis spectrophotometry and fluorescence were used to measure PDA reactivity for 57 chemicals including anhydrides, aldehydes, and quinones where reaction rates ranged from 116 to 6.2 × 10−6 M−1 s−1 for extreme to weak sensitizers, respectively. No reactivity towards PDA was observed with the thiol-selective sensitizers, non-sensitizers and prohaptens. The PDA rate constants correlated significantly with their respective murine local lymph node assay (LLNA) threshold EC3 values (R2 = 0.76). The use of PDA serves as a simple, inexpensive amine based method that shows promise as a preliminary screening tool for electrophilic, amine-selective skin sensitizers. PMID:24333919

  11. Separation of aromatics by vapor permeation through solvent swollen membrane

    Energy Technology Data Exchange (ETDEWEB)

    Ito, A.; Adachi, K.; Feng, Y. [Niigata University, Niigata (Japan)

    1995-12-20

    A vapor permeation process for aromatics separation from a hydrocarbon mixture was studied by means of the simultaneous permeation of dimethylsulfoxide vapor as an agent for membrane swelling and preferential permeation of aromatics. The separation performance of the process was demonstrated by a polyvinylalcohol membrane for mixed vapors of benzene/cyclohexane, xylene/octane and a model gasoline. The aromatic vapors preferentially permeated from these mixed vapor feeds. The separation factor was over 10. The separation mechanism of the process mainly depends on the relative salability of the vapors between aromatics and other hydrocarbons in dimethylsulfoxide. 14 refs., 9 figs., 1 tab.

  12. Does the concept of Clar's aromatic sextet work for dicationic forms of polycyclic aromatic hydrocarbons?--testing the model against charged systems in singlet and triplet states.

    Science.gov (United States)

    Dominikowska, Justyna; Palusiak, Marcin

    2011-07-07

    The concept of Clar's π-electron aromatic sextet was tested against a set of polycyclic aromatic hydrocarbons in neutral and doubly charged forms. Systems containing different types of rings (in the context of Clar's concept) were chosen, including benzene, naphthalene, anthracene, phenanthrene and triphenylene. In the case of dicationic structures both singlet and triplet states were considered. It was found that for singlet state dicationic structures the concept of aromatic sextet could be applied and the local aromaticity could be discussed in the context of that model, whereas in the case of triplet state dicationic structures Clar's model rather failed. Different aromaticity indices based on various properties of molecular systems were applied for the purpose of the studies. The discussion about the interdependence between the values of different aromaticity indices applied to neutral and charged systems in singlet and triplet states is also included. This journal is © the Owner Societies 2011

  13. Deuteration of benzen derivatives and condensed aromatics

    International Nuclear Information System (INIS)

    Ichikawa, Masaru.

    1970-01-01

    A process for the deuteration of aromatic compounds (benzene derivatives having one or more cyano, halogeno, nitro or other electron attractive groups, and condensed ring aromatics) is provided. The process comprises reducing said aromatic compound with an alkali metal (preferably K, Rb or Cs) in a solvent (dimethoxyethane, tetrahydrofuran, etc.) to provide an electron-acceptor-donor complex, which is followed by introducing gaseous deuterium into the solution. The deuteration takes place selectively at the position of highest electron density in accordance with nature of the substituent, regardless of steric hindrance. The process is applicable to a wide variety of aromatics to give deuterated compounds in high yields. In one example, 5x10 -3 mole of anthracene (An) was reacted with 2g of metallic potassium in 80cc of dimethoxyethane in a N 2 atmosphere. Into the resulting solution of An=2K + was introduced D 2 gas (30 cmHg) at 25 0 C. After decomposition with air and washing with alcohol, the precipitate was recrystallized from benzene. Yield of recovered AN: more than 90%. Yield of deuteration: 100%. Position of deuteration: 9 and 10 (revealed by NMR and mass spectroscopy). (Kaichi, S.)

  14. Synthesis and bioelectrochemical behavior of aromatic amines.

    Science.gov (United States)

    Shabbir, Muhammad; Akhter, Zareen; Ahmad, Iqbal; Ahmed, Safeer; Bolte, Michael; McKee, Vickie

    2017-12-01

    Four aromatic amines 1-amino-4-phenoxybenzene (A 1 ), 4-(4-aminophenyloxy) biphenyl (A 2 ), 1-(4-aminophenoxy) naphthalene (A 3 ) and 2-(4-aminophenoxy) naphthalene (A 4 ) were synthesized and characterized by elemental, spectroscopic (FTIR, NMR), mass spectrometric and single crystal X-ray diffraction methods. The compounds crystallized in monoclinic crystal system with space group P2 1 . Intermolecular hydrogen bonds were observed between the amine group and amine/ether acceptors of neighboring molecules. Electrochemical investigations were done using cyclic voltammetry (CV), square wave voltammetry (SWV) and differential pulse voltammetry (DPV). CV studies showed that oxidation of aromatic amines takes place at about 0.9 V (vs. Ag/AgCl) and the electron transfer (ET) process has irreversible nature. After first scan reactive intermediate were generated electrochemically and some other cathodic and anodic peaks also appeared in the succeeding scans. DPV study revealed that ET process is accompanied by one electron. DNA binding study of aromatic amines was performed by CV and UV-visible spectroscopy. These investigations revealed groove binding mode of interaction of aromatic amines with DNA. Copyright © 2017 Elsevier Inc. All rights reserved.

  15. Oxidative decomposition of aromatic hydrocarbons by electron beam irradiation

    Science.gov (United States)

    Han, Do-Hung; Stuchinskaya, Tatiana; Won, Yang-Soo; Park, Wan-Sik; Lim, Jae-Kyong

    2003-05-01

    Decomposition of aromatic volatile organic compounds (VOCs) under electron beam irradiation was studied in order to examine the kinetics of the process, to characterize the reaction product distribution and to develop a process of waste gas control technology. Toluene, ethylbenzene, o-, m-, p-xylenes and chlorobenzene were used as target materials. The experiments were carried out at doses ranging from 0.5 to 10 kGy, using a flow reactor utilized under electron beam irradiation. Maximum degrees of decomposition carried out at 10 kGy in air environment were 55-65% for “non-chlorinated” aromatic VOC and 85% for chlorobenzene. It was found that a combination of aromatic pollutants with chlorobenzene would considerably increase the degradation value up to nearly 50% compared to the same compounds in the absence of chlorine groups. Based on our experimental observation, the degradation mechanism of the aromatic compounds combined with chloro-compound suggests that a chlorine radical, formed from EB irradiation, induces a chain reaction, resulting in an accelerating oxidative destruction of aromatic VOCs.

  16. Inversion of Configuration at the Phosphorus Nucleophile in the Diastereoselective and Enantioselective Synthesis of P-Stereogenic syn-Phosphiranes from Chiral Epoxides.

    Science.gov (United States)

    Muldoon, Jake A; Varga, Balázs R; Deegan, Meaghan M; Chapp, Timothy W; Eördögh, Ádám M; Hughes, Russell P; Glueck, David S; Moore, Curtis E; Rheingold, Arnold L

    2018-04-23

    Nucleophilic substitution results in inversion of configuration at the electrophilic carbon center (S N 2) or racemization (S N 1). The stereochemistry of the nucleophile is rarely considered, but phosphines, which have a high barrier to pyramidal inversion, attack electrophiles with retention of configuration at P. Surprisingly, cyclization of bifunctional secondary phosphine alkyl tosylates proceeded under mild conditions with inversion of configuration at the nucleophile to yield P-stereogenic syn-phosphiranes. DFT studies suggested that the novel stereochemistry results from acid-promoted tosylate dissociation to yield an intermediate phosphenium-bridged cation, which undergoes syn-selective cyclization. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Microbial degradation of aliphatic and aliphatic-aromatic co-polyesters.

    Science.gov (United States)

    Shah, Aamer Ali; Kato, Satoshi; Shintani, Noboru; Kamini, Numbi Ramudu; Nakajima-Kambe, Toshiaki

    2014-04-01

    Biodegradable plastics (BPs) have attracted much attention since more than a decade because they can easily be degraded by microorganisms in the environment. The development of aliphatic-aromatic co-polyesters has combined excellent mechanical properties with biodegradability and an ideal replacement for the conventional nondegradable thermoplastics. The microorganisms degrading these polyesters are widely distributed in various environments. Although various aliphatic, aromatic, and aliphatic-aromatic co-polyester-degrading microorganisms and their enzymes have been studied and characterized, there are still many groups of microorganisms and enzymes with varying properties awaiting various applications. In this review, we have reported some new microorganisms and their enzymes which could degrade various aliphatic, aromatic, as well as aliphatic-aromatic co-polyesters like poly(butylene succinate) (PBS), poly(butylene succinate)-co-(butylene adipate) (PBSA), poly(ε-caprolactone) (PCL), poly(ethylene succinate) (PES), poly(L-lactic acid) (PLA), poly(3-hydroxybutyrate) and poly(3-hydoxybutyrate-co-3-hydroxyvalterate) (PHB/PHBV), poly(ethylene terephthalate) (PET), poly(butylene terephthalate) (PBT), poly(butylene adipate-co-terephthalate (PBAT), poly(butylene succinate-co-terephthalate) (PBST), and poly(butylene succinate/terephthalate/isophthalate)-co-(lactate) (PBSTIL). The mechanism of degradation of aliphatic as well as aliphatic-aromatic co-polyesters has also been discussed. The degradation ability of microorganisms against various polyesters might be useful for the treatment and recycling of biodegradable wastes or bioremediation of the polyester-contaminated environments.

  18. Cross-Coupling of Sodium Sulfinates with Aryl, Heteroaryl and Vinyl Halides by Nickel/photoredox dual catalysis

    KAUST Repository

    Yue, Huifeng

    2017-12-06

    An efficient photoredox/nickel dual catalyzed sulfonylation reaction of aryl, heteroaryl, and vinyl halides has been achieved for the first time. This newly developed sulfonylation protocol provides a versatile method for the synthesis of diverse aromatic sulfones at room temperature and shows excellent functional group tolerance. The electrophilic coupling partners are not limited to aryl, heteroaryl and vinyl bromides but also less reactive aryl chlorides are suitable substrates for this transformation.

  19. Cross-Coupling of Sodium Sulfinates with Aryl, Heteroaryl and Vinyl Halides by Nickel/photoredox dual catalysis

    KAUST Repository

    Yue, Huifeng; Zhu, Chen; Rueping, Magnus

    2017-01-01

    An efficient photoredox/nickel dual catalyzed sulfonylation reaction of aryl, heteroaryl, and vinyl halides has been achieved for the first time. This newly developed sulfonylation protocol provides a versatile method for the synthesis of diverse aromatic sulfones at room temperature and shows excellent functional group tolerance. The electrophilic coupling partners are not limited to aryl, heteroaryl and vinyl bromides but also less reactive aryl chlorides are suitable substrates for this transformation.

  20. Distributions of Polycyclic Aromatic Hydrocarbons, Aromatic Ketones, Carboxylic Acids, and Trace Metals in Arctic Aerosols: Long-Range Atmospheric Transport, Photochemical Degradation/Production at Polar Sunrise.

    Science.gov (United States)

    Singh, Dharmendra Kumar; Kawamura, Kimitaka; Yanase, Ayako; Barrie, Leonard A

    2017-08-15

    The distributions, correlations, and source apportionment of aromatic acids, aromatic ketones, polycyclic aromatic hydrocarbons (PAHs), and trace metals were studied in Canadian high Arctic aerosols. Nineteen PAHs including minor sulfur-containing heterocyclic PAH (dibenzothiophene) and major 6 carcinogenic PAHs were detected with a high proportion of fluoranthene followed by benzo[k]fluoranthene, pyrene, and chrysene. However, in the sunlit period of spring, their concentrations significantly declined likely due to photochemical decomposition. During the polar sunrise from mid-March to mid-April, benzo[a]pyrene to benzo[e]pyrene ratios significantly dropped, and the ratios diminished further from late April to May onward. These results suggest that PAHs transported over the Arctic are subjected to strong photochemical degradation at polar sunrise. Although aromatic ketones decreased in spring, concentrations of some aromatic acids such as benzoic and phthalic acids increased during the course of polar sunrise, suggesting that aromatic hydrocarbons are oxidized to result in aromatic acids. However, PAHs do not act as the major source for low molecular weight (LMW) diacids such as oxalic acid that are largely formed at polar sunrise in the arctic atmosphere because PAHs are 1 to 2 orders of magnitude less abundant than LMW diacids. Correlations of trace metals with organics, their sources, and the possible role of trace transition metals are explained.

  1. Aromatic graphene

    Energy Technology Data Exchange (ETDEWEB)

    Das, D. K., E-mail: gour.netai@gmail.com [Department of Metallurgical and Material Science Engineering, National Institute of Technology Durgapur-713209, West Bengal (India); Sahoo, S., E-mail: sukadevsahoo@yahoo.com [Department of Physics, National Institute of Technology Durgapur-713209, West Bengal (India)

    2016-04-13

    In recent years graphene attracts the scientific and engineering communities due to its outstanding electronic, thermal, mechanical and optical properties and many potential applications. Recently, Popov et al. [1] have studied the properties of graphene and proved that it is aromatic but without fragrance. In this paper, we present a theory to prepare graphene with fragrance. This can be used as scented pencils, perfumes, room and car fresheners, cosmetics and many other useful household substances.

  2. Aromatic graphene

    International Nuclear Information System (INIS)

    Das, D. K.; Sahoo, S.

    2016-01-01

    In recent years graphene attracts the scientific and engineering communities due to its outstanding electronic, thermal, mechanical and optical properties and many potential applications. Recently, Popov et al. [1] have studied the properties of graphene and proved that it is aromatic but without fragrance. In this paper, we present a theory to prepare graphene with fragrance. This can be used as scented pencils, perfumes, room and car fresheners, cosmetics and many other useful household substances.

  3. [The substitution effect of leadership substitutes for transformational leadership in nursing organization].

    Science.gov (United States)

    Kim, Jeong-Hee

    2006-04-01

    This paper was conducted to examine the effects of transformational leadership behaviors, within the substitutes for leadership model (Kerr & Jermier, 1978). Data was collected from 181 staff nurses in 3 general hospitals, with self-reporting questionnaires (MLQ developed by Bass, rd-SLS developed by Podsakoff, et al., and MSQ developed by Weiss, et al.). Descriptive statistics, factor analysis, Cronbach's alpha and moderated regression analysis were used. 1) The transformational leader behaviors and substitutes for leadership each had correlations with job satisfaction. 2) The total amount of variance accounted for by the substitutes for leadership was substantially greater than by the transformational leadership behaviors. 3) Few of the substitutes variables moderated the relationships between the transformational leader behaviors and job satisfaction in a manner consistent with that specified by Howell, Dorfman, and Kerr (1986). The finding of this study suggest that leaders need to have a better understanding of those contextual variables that influence job satisfaction. Thus future research should focus attention on the moderating effects of substitutes, as well as the things that leaders can do to influence them. In addition, it may be good to examine the effects of substitutes on other criterion variables.

  4. Structure activity correlations in the inhibition of brain synaptosomal 3H-norepinephrine uptake by phenethylamine analogs. The role of α-alkyl side chain and methoxyl ring substitutions

    International Nuclear Information System (INIS)

    Makriyannis, A.; Bowerman, D.; Sze, P.Y.; Fournier, D.; Jong, A.P. de

    1982-01-01

    α-Ethylphenethylamine proved to be a weaker inhibitor of rat brain synaptosomal [ 3 H]norepinephrine ([ 3 H]NE) uptake than amphetamine, while 2-amino-tetralin and 2-amino-1,2-dihydronaphtalene, compounds in which the α-side chain ethyl group is tied to the aromatic ring have a similar inhibiting potency as amphetamine. Hallucinogenic polymethoxy substituted phenethylamine analogs have very low inhibitory potencies indicating that inhibition of NE-reuptake in brain noradrenergic neurons is not associated with the drug-induced hallucinogenic syndrome. (Auth.)

  5. Ultrasound Promoted Synthesis of Bis(substituted pyrazol-4-ylcarbonyl-Substituted Thioureas

    Directory of Open Access Journals (Sweden)

    Li Xiao

    2009-03-01

    Full Text Available A series of novel bis(substituted pyrazol-4-ylcarbonyl-substituted thioureas have been synthesized by the reactions of substituted pyrazol-4-ylcarbonyl isothiocyanates with different diamines under ultrasound irradiation and classical heating method at 20-25 °C. In general, substantial improvement in rates and modest yields increases were observed when reactions were carried out under sonication, compared with the classical heating method. The structures of these compounds have been elucidated by elemental and spectral (IR, 1H-NMR analysis.

  6. Reactivity measurement in estimation of benzoquinone and benzoquinone derivatives’ allergenicity

    International Nuclear Information System (INIS)

    Mbiya, Wilbes; Chipinda, Itai; Simoyi, Reuben H.; Siegel, Paul D.

    2016-01-01

    Benzoquinone (BQ) and benzoquinone derivatives (BQD) are used in the production of dyes and cosmetics. While BQ, an extreme skin sensitizer, is an electrophile known to covalently modify proteins via Michael Addition (MA) reaction whilst halogen substituted BQD undergo nucleophilic vinylic substitution (SNV) mechanism onto amine and thiol moieties on proteins, the allergenic effects of adding substituents on BQ have not been reported. The effects of inserting substituents on the BQ ring has not been studied in animal assays. However, mandated reduction/elimination of animals used in cosmetics testing in Europe has led to an increased need for alternatives for the prediction of skin sensitization potential. Electron withdrawing and electron donating substituents on BQ were assessed for effects on BQ reactivity toward nitrobenzene thiol (NBT). The NBT binding studies demonstrated that addition of EWG to BQ as exemplified by the chlorine substituted BQDs increased reactivity while addition of EDG as in the methyl substituted BQDs reduced reactivity. BQ and BQD skin allerginicity was evaluated in the murine local lymph node assay (LLNA). BQD with electron withdrawing groups had the highest chemical potency followed by unsubstituted BQ and the least potent were the BQD with electron donating groups. The BQD results demonstrate the impact of inductive effects on both BQ reactivity and allergenicity, and suggest the potential utility of chemical reactivity data for electrophilic allergen identification and potency ranking.

  7. Reactivity measurement in estimation of benzoquinone and benzoquinone derivatives’ allergenicity

    Science.gov (United States)

    Mbiya, Wilbes; Chipinda, Itai; Simoyi, Reuben H.; Siegel, Paul D.

    2015-01-01

    Benzoquinone (BQ) and benzoquinone derivatives (BQD) are used in the production of dyes and cosmetics. While BQ, an extreme skin sensitizer, is an electrophile known to covalently modify proteins via Michael Addition (MA) reaction whilst halogen substituted BQD undergo nucleophilic vinylic substitution (SNV) mechanism onto amine and thiol moieties on proteins, the allergenic effects of adding substituents on BQ have not been reported. The effects of inserting substituents on the BQ ring has not been studied in animal assays. However, mandated reduction/elimination of animals used in cosmetics testing in Europe has led to an increased need for alternatives for the prediction of skin sensitization potential. Electron withdrawing and electron donating substituents on BQ were assessed for effects on BQ reactivity toward nitrobenzene thiol (NBT). The NBT binding studies demonstrated that addition of EWG to BQ as exemplified by the chlorine substituted BQDs increased reactivity while addition of EDG as in the methyl substituted BQDs reduced reactivity. BQ and BQD skin allerginicity was evaluated in the murine local lymph node assay (LLNA). BQD with electron withdrawing groups had the highest chemical potency followed by unsubstituted BQ and the least potent were the BQD with electron donating groups. The BQD results demonstrate the impact of inductive effects on both BQ reactivity and allergenicity, and suggest the potential utility of chemical reactivity data for electrophilic allergen identification and potency ranking. PMID:26612505

  8. Global simulation of aromatic volatile organic compounds in the atmosphere

    Science.gov (United States)

    Cabrera Perez, David; Taraborrelli, Domenico; Pozzer, Andrea

    2015-04-01

    Among the large number of chemical compounds in the atmosphere, the organic group plays a key role in the tropospheric chemistry. Specifically the subgroup called aromatics is of great interest. Aromatics are the predominant trace gases in urban areas due to high emissions, primarily by vehicle exhausts and fuel evaporation. They are also present in areas where biofuel is used (i.e residential wood burning). Emissions of aromatic compounds are a substantial fraction of the total emissions of the volatile organic compounds (VOC). Impact of aromatics on human health is very important, as they do not only contribute to the ozone formation in the urban environment, but they are also highly toxic themselves, especially in the case of benzene which is able to trigger a range of illness under long exposure, and of nitro-phenols which cause detrimental for humans and vegetation even at very low concentrations. The aim of this work is to assess the atmospheric impacts of aromatic compounds on the global scale. The main goals are: lifetime and budget estimation, mixing ratios distribution, net effect on ozone production and OH loss for the most emitted aromatic compounds (benzene, toluene, xylenes, ethylbenzene, styrene and trimethylbenzenes). For this purpose, we use the numerical chemistry and climate simulation ECHAM/MESSy Atmospheric Chemistry (EMAC) model to build the global atmospheric budget for the most emitted and predominant aromatic compounds in the atmosphere. A set of emissions was prepared in order to include biomass burning, vegetation and anthropogenic sources of aromatics into the model. A chemical mechanism based on the Master Chemical Mechanism (MCM) was developed to describe the chemical oxidation in the gas phase of these aromatic compounds. MCM have been reduced in terms of number of chemical equation and species in order to make it affordable in a 3D model. Additionally other features have been added, for instance the production of HONO via ortho

  9. Global aromatics supply. Today and tomorrow

    Energy Technology Data Exchange (ETDEWEB)

    Bender, M. [BASF SE, Ludwigshafen (Germany)

    2013-11-01

    Aromatics are the essential building blocks for some of the largest petrochemical products in today's use. To the vast majority they are consumed to produce intermediates for polymer products and, hence, contribute to our modern lifestyle. Their growth rates are expected to be in line with GDP growth in future. This contrasts the significantly lower growth rates of the primary sources for aromatics - fuel processing and steam cracking of naphtha fractions. A supply gap can be expected to open up in future for which creative solutions will be required. (orig.)

  10. Silicone elastomers with aromatic voltage stabilizers

    DEFF Research Database (Denmark)

    A Razak, Aliff Hisyam; Skov, Anne Ladegaard

    of electron-trapping by aromatic compounds grafted to silicone backbones in a crosslinked PDMS is illustrated in Fig. 1. The electrical breakdown strength, the storage modulus and the loss modulus of the elastomer were investigated, as well as the excitation energy from the collision between electron carriers...... and benzene rings in PDMS-PPMS copolymer was measured by UV-vis spectroscopy. The developed elastomers were inherently soft with enhanced electrical breakdown strength due to delocalized pi-electrons of aromatic rings attached to the silicone backbone. The dielectric relative permittivity of PDMS...

  11. Reaction of singlet-excited 2,3-diazabicyclo[2.2.2]oct-2-ene and tert-butoxyl radicals with aryl-substituted benzofuranones.

    Science.gov (United States)

    Lundgren, Cecilia Vannesjö; Koner, Apurba L; Tinkl, Michael; Pischel, Uwe; Nau, Werner M

    2006-03-03

    5,7-Di-tert-butyl-3-aryl-3H-benzofuran-2-ones are lactones with potential antioxidant activity, owing to their abstractable benzylic C-H hydrogens. The fluorescence quenching of the azoalkane 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO), an established probe for the hydrogen-donor propensity of chain-breaking antioxidants, was investigated for 16 aryl-substituted benzofuranone derivatives [m,m-(CF3)2, p-CN, m-CN, p-CF3, p-COOCH3, m-CF3, p-Cl, p-F, H, m-CH3, p-CH3, m,p-(CH3)2, p-OCH3, o-CH3, o-CF3, o,m-(CH3)2]. Analysis of the rate data in terms of a linear free energy relationship yielded a reaction constant of rho = +0.35. This implies that n,pi*-excited DBO acts as nucleophilic species. In contrast, hydrogen abstraction of tert-butoxyl radicals from the benzofuranones was accelerated by electron-donating substituents (rho = -0.23), in conformity with the electrophilic character of oxygen-centered alkoxyl radicals. Possible implications for the optimization of the hydrogen-donor propensity of antioxidants through structural variation are discussed.

  12. New Palladium-Catalyzed Approaches to Heterocycles and Carbocycles

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Qinhua [Iowa State Univ., Ames, IA (United States)

    2004-12-19

    with the idea that these palladium-catalyzed C-H activation reactions parallel electrophilic aromatic substitution. A relatively efficient synthesis of cyclopropanes has been developed using palladium-catalyzed C-H activation chemistry, in which two new carbon-carbon bonds are formed in a single step. This method involves the palladium-catalyzed activation of relatively unreactive C-H bonds, and provides a very efficient way to synthesize cyclopropapyrrolo[1,2-a]indoles, analogues of the mitomycin antibiotics.

  13. Kinetics of electrophilic exchange of lanthanide(3) and copper(2) ions in aqueous solutions of ethylenediaminetetraacetates. [Rare earths: La,Pr,Nd,Eu,Gd,Tb,Er,Yb

    Energy Technology Data Exchange (ETDEWEB)

    Nikitenko, S.I.; Martynenko, L.I.; Pechurova, N.I.; Spitsyn, V.I. (Moskovskij Gosudarstvennyj Univ. (USSR))

    1984-05-01

    Electrophilic exchange in the MA/sup -/ - Cu/sup 2 +/ (M/sup 3 +/=La/sup 3 +/, PUPSILON/sup 3 +/, Nd/sup 3 +/, Eu/sup 3 +/, Gd/sup 3 +/, Tb/sup 3 +/, Er/sup 3 +/, Yb/sup 3 +/, A/sup 4 -/=ethylenediaminetetraacetate) systems is studied. Copper is chosen as a constituent cation, because the stability of the CuA/sup 2 +/- complex is higher than that of the MA/sup -/ complex, besides the CuA/sup 2 -/, is characterized by a high extinction coefficient E/sub 280/=3200. Electrophilic exchange in the systems is shown to be realized through the acid dissociation mechanism and through the association mechanism. Consideration of the acid dissociation mechanism assumes that the exchange is limited by a break in the metal-oxygen bond in the intermediate protonated complex. In case of the association mechanism it is limited by a break in the metal-nitrogen bond in the intermediate binuclear complex. Rate constants of the limiting stage are calculated. Dependences of the rate constants of exchange on the stability of the complexes, the order number of the element, acidity of medium, Cu/sup 2 +/ concentration are given. Differences are shown to exist between the exchange mechanisms in the studied: systems for the REE of cerium and yttrium subgroups.

  14. Substitution determination of Fmoc‐substituted resins at different wavelengths

    Science.gov (United States)

    Kley, Markus; Bächle, Dirk; Loidl, Günther; Meier, Thomas; Samson, Daniel

    2017-01-01

    In solid‐phase peptide synthesis, the nominal batch size is calculated using the starting resin substitution and the mass of the starting resin. The starting resin substitution constitutes the basis for the calculation of a whole set of important process parameters, such as the number of amino acid derivative equivalents. For Fmoc‐substituted resins, substitution determination is often performed by suspending the Fmoc‐protected starting resin in 20% (v/v) piperidine in DMF to generate the dibenzofulvene–piperidine adduct that is quantified by ultraviolet–visible spectroscopy. The spectrometric measurement is performed at the maximum absorption wavelength of the dibenzofulvene–piperidine adduct, that is, at 301.0 nm. The recorded absorption value, the resin weight and the volume are entered into an equation derived from Lambert–Beer's law, together with the substance‐specific molar absorption coefficient at 301.0 nm, in order to calculate the nominal substitution. To our knowledge, molar absorption coefficients between 7100 l mol−1 cm−1 and 8100 l mol−1 cm−1 have been reported for the dibenzofulvene–piperidine adduct at 301.0 nm. Depending on the applied value, the nominal batch size may differ up to 14%. In this publication, a determination of the molar absorption coefficients at 301.0 and 289.8 nm is reported. Furthermore, proof is given that by measuring the absorption at 289.8 nm the impact of wavelength accuracy is reduced. © 2017 The Authors Journal of Peptide Science published by European Peptide Society and John Wiley & Sons Ltd. PMID:28635051

  15. Synthesis, radiosynthesis, in vitro and preliminary in vivo evaluation of biphenyl carboxylic and hydroxamic matrix metalloproteinase (MMP) inhibitors as potential tumor imaging agents

    International Nuclear Information System (INIS)

    Oltenfreiter, Ruth; Staelens, Ludovicus; Hillaert, Ulrik; Heremans, An; Noel, Agnes; Frankenne, Francis; Slegers, Guido

    2005-01-01

    Excess matrix degradation is one of the hallmarks of cancer and is an important factor in the process of tumor progression. It is implicated in invasion, metastasis, growth, angiogenesis and migration. Many characteristics of matrix metalloproteinases (MMPs) make them attractive therapeutic and diagnostic targets. MMP expression is upregulated at the tumor site, with localization of activity in the tumor or the surrounding stroma, providing a target for medical imaging techniques. Radioiodinated carboxylic and hydroxamic MMP inhibitors 2-(4'-[ 123 I] iodo-biphenyl-4-sulfonylamino)-3-methyl-butyric acid (9) and 2-(4'-[ 123 I] iodo-biphenyl-4-sulfonylamino)-3-methyl-butyramide (11), their unlabelled standards and precursors were synthesized. Radioiodination was conducted by electrophilic aromatic substitution of the tributylstannyl precursors and resulted in radiochemical yields of 70+/-5% (n=6) and 60+/-5% (n=4), respectively. In vitro zymography and enzyme assays showed for both hydroxamic acid and carboxylic acid compounds a good inhibition activity and a high selectivity for MMP-2. In vivo biodistribution in NMRI mice showed no long-term accumulation in organs and the possibility to accumulate in the tumor in a later phase of this study

  16. Synthesis, radiosynthesis, in vitro and preliminary in vivo evaluation of biphenyl carboxylic and hydroxamic matrix metalloproteinase (MMP) inhibitors as potential tumor imaging agents

    Energy Technology Data Exchange (ETDEWEB)

    Oltenfreiter, Ruth [Laboratory of Radiopharmacy, Ghent University, Harelbekestraat 72, 9000 Ghent (Belgium)]. E-mail: ruth.oltenfreiter@ugent.be; Staelens, Ludovicus [Laboratory of Radiopharmacy, Ghent University, Harelbekestraat 72, 9000 Ghent (Belgium); Hillaert, Ulrik [Laboratory for Medicinal Chemistry, Ghent University, Harelbekestraat 72, 9000 Ghent (Belgium); Heremans, An; Noel, Agnes [Laboratory of Tumor and Developmental Biology, University of Liege, Sart-Tilman, Liege (Belgium); Frankenne, Francis [Laboratory of Tumor and Developmental Biology, University of Liege, Sart-Tilman, Liege (Belgium); Slegers, Guido [Laboratory of Radiopharmacy, Ghent University, Harelbekestraat 72, 9000 Ghent (Belgium)

    2005-06-01

    Excess matrix degradation is one of the hallmarks of cancer and is an important factor in the process of tumor progression. It is implicated in invasion, metastasis, growth, angiogenesis and migration. Many characteristics of matrix metalloproteinases (MMPs) make them attractive therapeutic and diagnostic targets. MMP expression is upregulated at the tumor site, with localization of activity in the tumor or the surrounding stroma, providing a target for medical imaging techniques. Radioiodinated carboxylic and hydroxamic MMP inhibitors 2-(4'-[{sup 123}I] iodo-biphenyl-4-sulfonylamino)-3-methyl-butyric acid (9) and 2-(4'-[{sup 123}I] iodo-biphenyl-4-sulfonylamino)-3-methyl-butyramide (11), their unlabelled standards and precursors were synthesized. Radioiodination was conducted by electrophilic aromatic substitution of the tributylstannyl precursors and resulted in radiochemical yields of 70+/-5% (n=6) and 60+/-5% (n=4), respectively. In vitro zymography and enzyme assays showed for both hydroxamic acid and carboxylic acid compounds a good inhibition activity and a high selectivity for MMP-2. In vivo biodistribution in NMRI mice showed no long-term accumulation in organs and the possibility to accumulate in the tumor in a later phase of this study.

  17. Friedel–Crafts Crosslinked Highly Sulfonated Polyether Ether Ketone (SPEEK Membranes for a Vanadium/Air Redox Flow Battery

    Directory of Open Access Journals (Sweden)

    Géraldine Merle

    2013-12-01

    Full Text Available Highly conductive and low vanadium permeable crosslinked sulfonated poly(ether ether ketone (cSPEEK membranes were prepared by electrophilic aromatic substitution for a Vanadium/Air Redox Flow Battery (Vanadium/Air-RFB application. Membranes were synthesized from ethanol solution and crosslinked under different temperatures with 1,4-benzenedimethanol and ZnCl2 via the Friedel–Crafts crosslinking route. The crosslinking mechanism under different temperatures indicated two crosslinking pathways: (a crosslinking on the sulfonic acid groups; and (b crosslinking on the backbone. It was observed that membranes crosslinked at a temperature of 150 °C lead to low proton conductive membranes, whereas an increase in crosslinking temperature and time would lead to high proton conductive membranes. High temperature crosslinking also resulted in an increase in anisotropy and water diffusion. Furthermore, the membranes were investigated for a Vanadium/Air Redox Flow Battery application. Membranes crosslinked at 200 °C for 30 min with a molar ratio between 2:1 (mol repeat unit:mol benzenedimethanol showed a proton conductivity of 27.9 mS/cm and a 100 times lower VO2+ crossover compared to Nafion.

  18. Friedel–Crafts Crosslinked Highly Sulfonated Polyether Ether Ketone (SPEEK) Membranes for a Vanadium/Air Redox Flow Battery

    Science.gov (United States)

    Merle, Géraldine; Ioana, Filipoi Carmen; Demco, Dan Eugen; Saakes, Michel; Hosseiny, Seyed Schwan

    2014-01-01

    Highly conductive and low vanadium permeable crosslinked sulfonated poly(ether ether ketone) (cSPEEK) membranes were prepared by electrophilic aromatic substitution for a Vanadium/Air Redox Flow Battery (Vanadium/Air-RFB) application. Membranes were synthesized from ethanol solution and crosslinked under different temperatures with 1,4-benzenedimethanol and ZnCl2 via the Friedel–Crafts crosslinking route. The crosslinking mechanism under different temperatures indicated two crosslinking pathways: (a) crosslinking on the sulfonic acid groups; and (b) crosslinking on the backbone. It was observed that membranes crosslinked at a temperature of 150 °C lead to low proton conductive membranes, whereas an increase in crosslinking temperature and time would lead to high proton conductive membranes. High temperature crosslinking also resulted in an increase in anisotropy and water diffusion. Furthermore, the membranes were investigated for a Vanadium/Air Redox Flow Battery application. Membranes crosslinked at 200 °C for 30 min with a molar ratio between 2:1 (mol repeat unit:mol benzenedimethanol) showed a proton conductivity of 27.9 mS/cm and a 100 times lower VO2+ crossover compared to Nafion. PMID:24957118

  19. Bromination of Phenol

    Science.gov (United States)

    Talbot, Christopher

    2013-01-01

    This "Science note" examines the bromination of phenol, a reaction that is commonly taught at A-level and IB (International Baccalaureate) as an example of electrophilic substitution. Phenol undergoes bromination with bromine or bromine water at room temperature. A white precipitate of 2,4,6-tribromophenol is rapidly formed. This…

  20. Equilibrium studies of the adsorption of aromatic disulfonates by Mg-Al oxide

    Science.gov (United States)

    Kameda, Tomohito; Umetsu, Mami; Kumagai, Shogo; Yoshioka, Toshiaki

    2018-03-01

    The removal of m-benzenedisulfonate (BDS2-) and 2,6-naphthalenedisulfonate (NDS2-) anions by Mg-Al oxide was investigated. Langmuir model best describes the adsorption of both aromatic disulfonate anions, with the maximum amount of uptake higher for BDS2-. Mg-Al oxide reacts easier with the aromatic disulfonate anion with higher charge density, a trend that is the opposite of that observed in aromatic sulfonate anions. After increasing the charge from -1 to -2, the removal of aromatic disulfonates by Mg-Al oxide is controlled by electrostatic interactions, instead of hydrophobic interactions that are dominant for aromatic sulfonate anions.

  1. Synthesis and Utilization of Trialkylammonium-Substituted Cyclodextrins as Water-Soluble Chiral NMR Solvating Agents for Anionic Compounds.

    Science.gov (United States)

    Dowey, Alison E; Puentes, Cira Mollings; Carey-Hatch, Mira; Sandridge, Keyana L; Krishna, Nikhil B; Wenzel, Thomas J

    2016-04-01

    Cationic trialkylammonium-substituted α-, β-, and γ-cyclodextrins containing trimethyl-, triethyl-, and tri-n-propylammonium substituent groups were synthesized and analyzed for utility as water-soluble chiral nuclear magnetic resonance (NMR) solvating agents. Racemic and enantiomerically pure (3-chloro-2-hydroxypropyl)trimethyl-, triethyl-, and tri-n-propyl ammonium chloride were synthesized from the corresponding trialkyl amine hydrochloride and either racemic or enantiomerically pure epichlorohydrin. The ammonium salts were then reacted with α-, β-, and γ-cyclodextrins at basic pH to provide the corresponding randomly substituted cationic cyclodextrins. The (1) H NMR spectra of a range of anionic, aromatic compounds was recorded with the cationic cyclodextrins. Cyclodextrins with a single stereochemistry at the hydroxy group on the (2-hydroxypropyl)trialkylammonium chloride substituent were often but not always more effective than the corresponding cyclodextrin in which the C-2 position was racemic. In several cases, the larger triethyl or tri-n-propyl derivatives were more effective than the corresponding trimethyl derivative at causing enantiomeric differentiation. None of the cyclodextrin derivatives were consistently the most effective for all of the anionic compounds studied. © 2016 Wiley Periodicals, Inc.

  2. Ion beam irradiation effects on aromatic polymers

    International Nuclear Information System (INIS)

    Shukushima, Satoshi; Ueno, Keiji

    1995-01-01

    We studied the optical and thermal properties of aromatic polymer films which had been irradiated with 1 MeV H + , H 2 + and He + ions. The examined aromatic polymers were polyetherether ketone(PEEK), polyetherimide(PEI), polyether sulfon(PES), polysulfon(PSF), and polyphenylene sulfide(PPS). The optical densities at 300nm of PES and PSF greatly increased after the irradiation. The optical densities at 400nm of all the examined polymer lineally increased with the irradiation dose. The PEEK film which had been irradiated with 1 MeV H + was not deformed above melting point. This demonstrates that cross-linking occurs in PEEK films by ion beam irradiation. As for the effects, depending on the mass of the irradiated ions, it was found that the ions with a high mass induced larger effects on the aromatic polymers for the same absorption energy. (author)

  3. Determination of aromatic and PAH (polycyclic aromatic hydrocarbons) content of oily wastewaters

    Energy Technology Data Exchange (ETDEWEB)

    Lysyj, I.; Russell, E.C.

    1978-08-01

    An analytical scheme was developed for determining the total organic content and hydrocarbon concentration from a one-liter portion of a wastewater sample, and determining the volatile, suspended, and water-soluble fractions from a second, two-liter portion. Analyses of untreated and treated bilge wastewater from the U.S. Army Fort Eustis, Va., facility showed 10-300 ppm suspended organics and 10-300 ppm dissolved organics in the untreated bilge, and no suspended matter, but 700-2000 ppm dissolved organics, in the treated bilge wastewaters. Of the dissolved organics in untreated and treated wastewater, 70 and 10%, respectively, were extracted with chloroform; the organics in the treated water were probably biologically derived from petroleum degradation. Gas chromatographic/mass spectroscopic and high-pressure liquid chromatographic analyses of the chloroform extracts showed about equal parts of phenolic compounds and aromatic hydrocarbons, small amounts of heterocyclics, and traces of polycyclic aromatics in the untreated wastewater, and mainly phenolics in the treated water.

  4. SEDIMENT-ASSOCIATED REACTIONS OF AROMATIC AMINES. 2. QSAR DEVELOPMENT

    Science.gov (United States)

    The fate of aromatic amines in soils and sediments is dominated by irreversible binding through nucleophilic addition and oxidative radical coupling. Despite the common occurrence of the aromatic amine functional group in organic chemicals, the molecular properties useful for pr...

  5. A theoretical quantum study on the distribution of electrophilic and nucleophilic active sites on Cu(100) surfaces modeled as finite clusters; Un estudio teorico cuantico sobre la distribucion de sitios activos electrofilicos y nucleofilicos sobre superficies de Cu(100) modeladas como cumulos finitos

    Energy Technology Data Exchange (ETDEWEB)

    Rios R, C.H.; Romero R, M. [Universidad Autonoma Metropolitana-Azcapotzalco, Departamento de Materiales, Av. San Pablo 180, Col. Reynosa Tamaulipas, 02200 Mexico D.F. (Mexico); Ponce R, A.; Mendoza H, L.H. [Universidad Autonoma del Estado de Hidalgo, Centro de Investigaciones Quimicas, Carretera Pachuca-Tulancingo km. 4.5, 42181 Pachuca, Hidalgo (Mexico)]. e-mail: clara_hrr@yahoo.es

    2008-07-01

    In this work, it is shown a theoretical quantum study of the active sites distribution on a monocrystalline surface of Cu(100). The copper surface was modeled as finite clusters of 14, 23, 38 and 53 atoms. We performed Hartree-Fock and Density Functional Theory (B3LYP) ab initio calculations employing the pseudopotentials of Hay and Wadt (LANLlMB y LANL2DZ). From calculations, we found a work function value of 4.1 eV. The mapping of the HOMO and LUMO in the frozen core approximation, allowed us finding the electrophilic and nucleophilic active sites distribution, respectively. The results indicated that electrophilic sites on the Cu(100) surface were located on hollow position and its numerical density was 8.6 x 10{sup 16} sites cm{sup -2}. From the nucleophilic local softness study, it was found that the nucleophilic sites were formed by a group of atoms and it had a numerical density of 2.4x 10{sup 16} sitescm{sup -2} . Last results indicated that adsorptions with 2 x 2 and 3 x 3 distributions can be favored onto a Cu(100) surface for the electrophilic and nucleophilic cases, respectively. (Author)

  6. A Review of Polycyclic Aromatic Hydrocarbons and Heavy Metal ...

    African Journals Online (AJOL)

    A Review of Polycyclic Aromatic Hydrocarbons and Heavy Metal Contamination of Fish from Fish Farms. ... Journal of Applied Sciences and Environmental Management ... Polycyclic aromatic hydrocarbons (PAHs) and heavy metals contribute to pollutants in aquaculture facilities and thus need to be further investigated.

  7. Metal Triflates for the Production of Aromatics from Lignin

    NARCIS (Netherlands)

    Deuss, Peter J.; Lahive, Ciaran W.; Lancefield, Christopher S.; Westwood, Nicholas J.; Kamer, Paul C. J.; Barta, Katalin; de Vries, Johannes G.

    2016-01-01

    The depolymerization of lignin into valuable aromatic chemicals is one of the key goals towards establishing economically viable biorefineries. In this contribution we present a simple approach for converting lignin to aromatic monomers in high yields under mild reaction conditions. The methodology

  8. Reduction of Aromatic and Heterocyclic Aromatic N-Hydroxylamines by Human Cytochrome P450 2S1

    Science.gov (United States)

    Wang, Kai; Guengerich, F. Peter

    2013-01-01

    Many aromatic amines and heterocyclic aromatic amines (HAAs) are known carcinogens for animals and there is also strong evidence for some in human cancer. The activation of these compounds, including some arylamine drugs, involves N-hydroxylation, usually by cytochrome P450 enzymes (P450) in Family 1 (1A2, 1A1, and 1B1). We previously demonstrated that the bioactivation product of the anti-cancer agent 2-(4-amino-3-methylphenyl)-5-fluorobenzothiazole (5F 203), an N-hydroxylamine, can be reduced by P450 2S1 to its amine precursor under anaerobic conditions and, to a lesser extent, under aerobic conditions (Wang, K., and Guengerich, F. P. (2012) Chem. Res. Toxicol. 25, 1740–1751). In the present study, we tested the hypothesis that P450 2S1 is involved in the reductive biotransformation of known carcinogenic aromatic amines and HAAs. The N-hydroxylamines of 4-aminobiphenyl (4-ABP), 2-naphthylamine (2-NA), and 2-aminofluorene (2-AF) were synthesized and found to be reduced by P450 2S1 under both anaerobic and aerobic conditions. The formation of amines due to P450 2S1 reduction also occurred under aerobic conditions but was less apparent because the competitive disproportionation reactions (of the N-hydroxylamines) also yielded amines. Further, some nitroso and nitro derivatives of the arylamines could also be reduced by P450 2S1. None of the amines tested were oxidized by P450 2S1. These results suggest that P450 2S1 may be involved in the reductive detoxication of several of the activated products of carcinogenic aromatic amines and HAAs. PMID:23682735

  9. Modelling charge transport of discotic liquid-crystalline triindoles: the role of peripheral substitution.

    Science.gov (United States)

    Volpi, Riccardo; Camilo, Ana Claudia Santos; Filho, Demetrio A da Silva; Navarrete, Juan T López; Gómez-Lor, Berta; Delgado, M Carmen Ruiz; Linares, Mathieu

    2017-09-13

    We have performed a multiscale approach to study the influence of peripheral substitution in the semiconducting properties of discotic liquid-crystalline triindoles. Charge carrier mobility as high as 1.4 cm 2 V -1 s -1 was experimentally reported for triindoles substituted with alkynyl chains on the periphery (Gómez-Lor et al. Angew. Chem., Int. Ed., 2011, 50, 7399-7402). In this work, our goal is to get a deeper understanding of both the molecular electronic structure and microscopic factors affecting the charge transport properties in triindoles as a function of the spacer group connecting the central cores with the external alkyl chains (i.e., alkyne or phenyl spacers groups). To this end, we first perform Quantum Mechanical (QM) calculations to assess how the peripheral substitution affects the electronic structure and the internal reorganization energy. Secondly, boxes of stacked molecules were built and relaxed through molecular dynamics to obtain realistic structures. Conformational analysis and calculations of transfer integrals for closed neighbours were performed. Our results show that the insertion of ethynyl spacers between the central aromatic core and the flexible peripheral chains results in lower reorganization energies and enhanced intermolecular order within the stacks with a preferred cofacial 60° staggered conformation, which would result in high charge-carrier mobilities in good agreement with the experimental data. This work allows a deeper understanding of charge carrier mobility in columnar phases, linking the structural order at the molecular level to the property of interest, i.e. the charge carrier mobility. We hope that this understanding will improve the design of systems at the supramolecular level aiming at obtaining a more defined conducting channel, higher mobility and smaller fluctuations within the column.

  10. Global atmospheric budget of simple monocyclic aromatic compounds

    Directory of Open Access Journals (Sweden)

    D. Cabrera-Perez

    2016-06-01

    Full Text Available The global atmospheric budget and distribution of monocyclic aromatic compounds is estimated, using an atmospheric chemistry general circulation model. Simulation results are evaluated with an ensemble of surface and aircraft observations with the goal of understanding emission, production and removal of these compounds.Anthropogenic emissions provided by the RCP database represent the largest source of aromatics in the model (≃ 23 TgC year−1 and biomass burning from the GFAS inventory the second largest (≃ 5 TgC year−1. The simulated chemical production of aromatics accounts for  ≃ 5 TgC year−1. The atmospheric burden of aromatics sums up to 0.3 TgC. The main removal process of aromatics is photochemical decomposition (≃ 27 TgC  year−1, while wet and dry deposition are responsible for a removal of  ≃ 4 TgC year−1.Simulated mixing ratios at the surface and elsewhere in the troposphere show good spatial and temporal agreement with the observations for benzene, although the model generally underestimates mixing ratios. Toluene is generally well reproduced by the model at the surface, but mixing ratios in the free troposphere are underestimated. Finally, larger discrepancies are found for xylenes: surface mixing ratios are not only overestimated but also a low temporal correlation is found with respect to in situ observations.

  11. Biodegradation of Various Aromatic Compounds by Enriched Bacterial Cultures: Part A-Monocyclic and Polycyclic Aromatic Hydrocarbons.

    Science.gov (United States)

    Oberoi, Akashdeep Singh; Philip, Ligy; Bhallamudi, S Murty

    2015-08-01

    Present study focused on the screening of bacterial consortium for biodegradation of monocyclic aromatic hydrocarbon (MAH) and polycyclic aromatic hydrocarbons (PAHs). Target compounds in the present study were naphthalene, acenaphthene, phenanthrene (PAHs), and benzene (MAH). Microbial consortia enriched with the above target compounds were used in screening experiments. Naphthalene-enriched consortium was found to be the most efficient consortium, based on its substrate degradation rate and its ability to degrade other aromatic pollutants with significantly high efficiency. Substrate degradation rate with naphthalene-enriched culture followed the order benzene > naphthalene > acenaphthene > phenanthrene. Chryseobacterium and Rhodobacter were discerned as the predominant species in naphthalene-enriched culture. They are closely associated to the type strain Chryseobacterium arthrosphaerae and Rhodobacter maris, respectively. Single substrate biodegradation studies with naphthalene (PAH) and benzene (MAH) were carried out using naphthalene-enriched microbial consortium (NAPH). Phenol and 2-hydroxybenzaldehyde were identified as the predominant intermediates during benzene and naphthalene degradation, respectively. Biodegradation of toluene, ethyl benzene, xylene, phenol, and indole by NAPH was also investigated. Monod inhibition model was able to simulate biodegradation kinetics for benzene, whereas multiple substrate biodegradation model was able to simulate biodegradation kinetics for naphthalene.

  12. Substitution determination of Fmoc-substituted resins at different wavelengths.

    Science.gov (United States)

    Eissler, Stefan; Kley, Markus; Bächle, Dirk; Loidl, Günther; Meier, Thomas; Samson, Daniel

    2017-10-01

    In solid-phase peptide synthesis, the nominal batch size is calculated using the starting resin substitution and the mass of the starting resin. The starting resin substitution constitutes the basis for the calculation of a whole set of important process parameters, such as the number of amino acid derivative equivalents. For Fmoc-substituted resins, substitution determination is often performed by suspending the Fmoc-protected starting resin in 20% (v/v) piperidine in DMF to generate the dibenzofulvene-piperidine adduct that is quantified by ultraviolet-visible spectroscopy. The spectrometric measurement is performed at the maximum absorption wavelength of the dibenzofulvene-piperidine adduct, that is, at 301.0 nm. The recorded absorption value, the resin weight and the volume are entered into an equation derived from Lambert-Beer's law, together with the substance-specific molar absorption coefficient at 301.0 nm, in order to calculate the nominal substitution. To our knowledge, molar absorption coefficients between 7100 l mol -1  cm -1 and 8100 l mol -1  cm -1 have been reported for the dibenzofulvene-piperidine adduct at 301.0 nm. Depending on the applied value, the nominal batch size may differ up to 14%. In this publication, a determination of the molar absorption coefficients at 301.0 and 289.8 nm is reported. Furthermore, proof is given that by measuring the absorption at 289.8 nm the impact of wavelength accuracy is reduced. © 2017 The Authors Journal of Peptide Science published by European Peptide Society and John Wiley & Sons Ltd. © 2017 The Authors Journal of Peptide Science published by European Peptide Society and John Wiley & Sons Ltd.

  13. Electricity/oil substitution

    International Nuclear Information System (INIS)

    Melvin, J.G.

    1980-09-01

    The extent to which electricity could substitute for imported oil in Canada is assessed and it is concluded that the bulk of projected oil imports could be displaced. This substitution of electricity for oil could be largely completed within two decades, with existing technology, using Canadian resources. The substitution of electricity for imported oil would result in relatively low energy costs and would stimulate economic growth. Energy self-sufficiency through the substitution of electricity for oil is uniquely a Canadian option; it is not open to other industrial countries. The option exists because of Canada's resources of oil sands for essential liquid fuels, hydraulic and nuclear electrical potential, and natural gas as an interim source of energy. While other countries face an energy crisis due to declining supplies of oil, Canada faces opportunities. The policies of Federal and Provincial governments, as perceived by individual decision makers, will have a major influence on Canada's ability to realize opportunities. (auth)

  14. Merocyanines: polyene-polymethine transition in donor-acceptor-substituted stilbenes and polyenes

    International Nuclear Information System (INIS)

    Rettig, Wolfgang; Dekhtyar, Marina

    2003-01-01

    Three series of donor-acceptor-substituted conjugated compounds, namely, stilbenes, the open-chain polyenes of equivalent length, and the species of intermediate structure (polyenes terminated with only one phenyl ring) have been studied by the AM1 and HMO methods to elucidate and compare the structural prerequisites of the ideal polymethinic state ('cyanine limit'). The transition from polyenic to polymethinic properties has been traced in terms of bond-length (bond-order) alternation using the variation of terminal donor and acceptor substituents. Stilbenes manifest themselves as notably 'retarded' polyenes since a larger electronic asymmetry is necessary for them to reach the same degree of polymethinic character. The ground and the excited state have been shown to differ much more strongly for stilbenes than for polyenes with respect to the position of the bond equalization point on the scale of donor-acceptor difference. For the compounds containing one phenyl ring, the features revealed are intermediate between stilbenes and polyenes. The large S 0 -S 1 discrepancy in terms of bond alternation is a general property of aromatic ring-terminated chains (stilbenes) and is related to the influence of the aromatic character which can be quantified in this way. In this context, the most relevant definition for the cyanine limit (based on the bond invariance upon excitation) was selected from the existing definitions. The major trends revealed in the polyenic/polymethinic behaviour of the molecules can be interpreted on a topological basis within HMO or even simpler models with some additional influence due to the interelectronic repulsion which is taken into account in the AM1 treatment

  15. Aromatics saturation, opening and cleavage technology for middle distillates

    Energy Technology Data Exchange (ETDEWEB)

    Oballa, M.C.; Simanzhenkov, V.; Kim, G. [NOVA Chemicals Corp., Calgary, AB (Canada)

    2009-07-01

    In order to address environmental concerns, there is a need to develop technologies to reformulate or adjust the quality of transportation fuels. The purpose is to reduce the concentration of the compounds which negatively affect the air that people breathe. One of those targeted is the aromatics content of diesel, because high aromatics content results in low cetane number of diesel, as well as higher emission of particulate matter. Less conventional sources of hydrocarbon feedstock such as oil from oil sands and/or shale oil are being exploited in Alberta. These feeds contain multiple fused aromatic ring compounds. NOVA Chemicals would like to use these potentially abundant liquids as feed, but they must first be transformed into a more user friendly state. This paper discussed the development of a process technology that could saturate the aromatic rings, open up the saturated rings and cleave them to get smaller paraffinic molecules. The products then comprised of lower paraffins are suitable as feed to steam crackers for the production of ethylene and propylene, higher paraffins suitable for blending into gasoline and mono aromatic ring compounds which may be further treated through alkylation of benzene to ethylbenzene and dealkylation to styrene. The paper discussed the process steps and highlighted the catalysts. Research results were also shown. It was concluded that the critical technology gaps, as well as solutions, which would enable overcoming the challenges related to handling of aromatic bitumen feedstock, entail the development of two different catalysts, which are on two different technology platforms. 7 refs., 3 tabs., 5 figs.

  16. Application of aromatization catalyst in synthesis of carbon nanotubes

    Indian Academy of Sciences (India)

    In a typical chemical vapour deposition (CVD) process for synthesizing carbon nanotubes (CNTs), it was found that the aromatization catalysts could promote effectively the formation of CNT. The essence of this phenomenon was attributed to the fact that the aromatization catalyst can accelerate the ...

  17. Alkylation of organic aromatic compounds

    Science.gov (United States)

    Smith, Jr., Lawrence A.

    1989-01-01

    Aromatic compounds are alkylated in a catalytic distillation, wherein the catalyst structure also serves as a distillation component by contacting the aromatic compound with a C.sub.2 to C.sub.10 olefin in the catalyst bed under 0.25 to 50 atmospheres of pressure and at temperatures in the range of 80.degree. C. to 500.degree. C., using as the catalyst a mole sieve characterized as acidic or an acidic cation exchange resin. For example, ethyl benzene is produced by feeding ethylene below the catalyst bed while benzene is conveniently added through the reflux in molar excess to that required to react with ethylene, thereby reacting substantially all of the ethylene and recovering benzene as the principal overhead and ethyl benzene in the bottoms.

  18. Alkylation of organic aromatic compounds

    Science.gov (United States)

    Smith, L.A. Jr.

    1989-07-18

    Aromatic compounds are alkylated in a catalytic distillation, wherein the catalyst structure also serves as a distillation component by contacting the aromatic compound with a C[sub 2] to C[sub 10] olefin in the catalyst bed under 0.25 to 50 atmospheres of pressure and at temperatures in the range of 80 C to 500 C, using as the catalyst a mole sieve characterized as acidic or an acidic cation exchange resin. For example, ethyl benzene is produced by feeding ethylene below the catalyst bed while benzene is conveniently added through the reflux in molar excess to that required to react with ethylene, thereby reacting substantially all of the ethylene and recovering benzene as the principal overhead and ethyl benzene in the bottoms. 1 fig.

  19. Novel molecular-level evidence of iodine binding to natural organic matter from Fourier transform ion cyclotron resonance mass spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Chen, E-mail: xuchen66@tamu.edu [Laboratory for Environmental and Oceanographic Research, Department of Marine Sciences, Texas A and M University, Building 3029, Galveston, TX 77551 (United States); Chen, Hongmei [Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, VA 23529 (United States); Sugiyama, Yuko [Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, VA 23529 (United States); University of Hyogo, 1-1-12, Shinzaike-honcho, Himeji, Hyogo 670-0092 (Japan); Zhang, Saijin; Li, Hsiu-Ping; Ho, Yi-Fang; Chuang, Chia-ying; Schwehr, Kathleen A. [Laboratory for Environmental and Oceanographic Research, Department of Marine Sciences, Texas A and M University, Building 3029, Galveston, TX 77551 (United States); Kaplan, Daniel I. [Savannah River National Laboratory, Aiken, SC 29808 (United States); Yeager, Chris [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Roberts, Kimberly A. [Savannah River National Laboratory, Aiken, SC 29808 (United States); Hatcher, Patrick G. [Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, VA 23529 (United States); Santschi, Peter H. [Laboratory for Environmental and Oceanographic Research, Department of Marine Sciences, Texas A and M University, Building 3029, Galveston, TX 77551 (United States)

    2013-04-01

    Major fractions of radioiodine ({sup 129}I) are associated with natural organic matter (NOM) in the groundwater and surface soils of the Savannah River Site (SRS). Electrospray ionization coupled to Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS) was applied to elucidate the interactions between inorganic iodine species (iodide and iodate) and a fulvic acid (FA) extracted from a SRS surface soil. Iodate is likely reduced to reactive iodine species by the lignin- and tannin-like compounds or the carboxylic-rich alicyclic molecules (CRAM), during which condensed aromatics and lignin-like compounds were generated. Iodide is catalytically oxidized into reactive iodine species by peroxides, while FA is oxidized by peroxides into more aliphatic and less aromatic compounds. Only 9% of the total identified organo-iodine compounds derived from molecules originally present in the FA, whereas most were iodine binding to newly-produced compounds. The resulting iodinated molecules were distributed in three regions in the van Krevelen diagrams, denoting unsaturated hydrocarbons, lignin and protein. Moreover, characteristics of these organo-iodine compounds, such as their relatively low O/C ratios (< 0.2 or < 0.4) and yet some degree of un-saturation close to that of lignin, have multiple important environmental implications concerning possibly less sterically-hindered aromatic ring system for iodine to get access to and a lower hydrophilicity of the molecules thus to retard their migration in the natural aquatic systems. Lastly, ∼ 69% of the identified organo-iodine species contains nitrogen, which is presumably present as -NH{sub 2} or -HNCOR groups and a ring-activating functionality to favor the electrophilic substitution. The ESI-FTICR-MS technique provides novel evidence to better understand the reactivity and scavenging properties of NOM towards radioiodine and possible influence of NOM on {sup 129}I migration. Highlights: ► IO{sub 3}{sup

  20. Catalytic oxidation of o-aminophenols and aromatic amines by mushroom tyrosinase.

    Science.gov (United States)

    Muñoz-Muñoz, Jose Luis; Garcia-Molina, Francisco; Garcia-Ruiz, Pedro Antonio; Varon, Ramon; Tudela, Jose; Rodriguez-Lopez, Jose N; Garcia-Canovas, Francisco

    2011-12-01

    The kinetics of tyrosinase acting on o-aminophenols and aromatic amines as substrates was studied. The catalytic constants of aromatic monoamines and o-diamines were both low, these results are consistent with our previous mechanism in which the slow step is the transfer of a proton by a hydroxyl to the peroxide in oxy-tyrosinase (Fenoll et al., Biochem. J. 380 (2004) 643-650). In the case of o-aminophenols, the hydroxyl group indirectly cooperates in the transfer of the proton and consequently the catalytic constants in the action of tyrosinase on these compounds are higher. In the case of aromatic monoamines, the Michaelis constants are of the same order of magnitude than for monophenols, which suggests that the monophenols bind better (higher binding constant) to the enzyme to facilitate the π-π interactions between the aromatic ring and a possible histidine of the active site. In the case of aromatic o-diamines, both the catalytic and Michaelis constants are low, the values of the catalytic constants being lower than those of the corresponding o-diphenols. The values of the Michaelis constants of the aromatic o-diamines are slightly lower than those of their corresponding o-diphenols, confirming that the aromatic o-diamines bind less well (lower binding constant) to the enzyme. Copyright © 2011 Elsevier B.V. All rights reserved.

  1. A novel aromatic alcohol dehydrogenase in higher plants: molecular cloning and expression.

    Science.gov (United States)

    Goffner, D; Van Doorsselaere, J; Yahiaoui, N; Samaj, J; Grima-Pettenati, J; Boudet, A M

    1998-03-01

    Cinnamyl alcohol dehydrogenase (CAD; EC 1.1.195) catalyses the conversion of p-hydroxy-cinnamaldehydes to the corresponding alcohols and is considered a key enzyme in lignin biosynthesis. In a previous study, an atypical form of CAD (CAD 1) was identified in Eucalyptus gunnii [12]. We report here the molecular cloning and characterization of the corresponding cDNA, CAD 1-5, which encodes this novel aromatic alcohol dehydrogenase. The identity of CAD 1-5 was unambiguously confirmed by sequence comparison of the cDNA with peptide sequences derived from purified CAD 1 protein and by functional expression of CAD 1 recombinant protein in Escherichia coli. Both native and recombinant CAD 1 exhibit high affinity towards lignin precursors including 4-coumaraldehyde and coniferaldehyde, but they do not accept sinapaldehyde. Moreover, recombinant CAD 1 can also utilize a wide range of aromatic substrates including unsubstituted and substituted benzaldehydes. The open reading frame of CAD 1-5 encodes a protein with a calculated molecular mass of 35,790 Da and an isoelectric point of 8.1. Although sequence comparisons with proteins in databases revealed significant similarities with dihydroflavonol-4-reductases (DFR; EC 1.1.1.219) from a wide range of plant species, the most striking similarity was found with cinnamoyl-CoA reductase (CCR; EC 1.2.1.44), the enzyme which directly precedes CAD in the lignin biosynthetic pathway. RNA blot analysis and immunolocalization experiments indicated that CAD 1 is expressed in both lignified and unlignified tissues/cells. Based on the catalytic activity of CAD 1 in vitro and its localization in planta, CAD 1 may function as an 'alternative' enzyme in the lignin biosynthetic pathway. However, additional roles in phenolic metabolism are not excluded.

  2. Extraction of Aromatics from Heavy Naphtha Using Different Solvents

    International Nuclear Information System (INIS)

    EI-Bassuoni, A.A.; Esmael, K.K.

    2004-01-01

    Aromatic hydrocarbons are very important to the petrochemical industry. Among these are benzene, toluene and xylene (BTX), which are basic raw materials for the production of a number of important petrochemicals. There are many processes used to separate aromatic from non aromatic such as fractionation, azeotropic distillation and liquid I liquid extraction, etc. Liquid - liquid extraction is unique, efficiently used for heat sensitive, close boiling components and for separation of components not possible by other unit operations and it could be done at ambient temperature makes it more energy efficient. The choice of solvent depends on the properties and boiling range of the feedstock. Through the years, a lot of selective solvents has been proposed and selected for the physical separation of aromatics in liquid liquid extraction. Among the selection criteria are the stability,. chemical compatibility, availability, environmental hazards and price of the solvent. But the basic solvent properties that make it efficient are selectivity and capacity

  3. Revisiting the definition of local hardness and hardness kernel.

    Science.gov (United States)

    Polanco-Ramírez, Carlos A; Franco-Pérez, Marco; Carmona-Espíndola, Javier; Gázquez, José L; Ayers, Paul W

    2017-05-17

    An analysis of the hardness kernel and local hardness is performed to propose new definitions for these quantities that follow a similar pattern to the one that characterizes the quantities associated with softness, that is, we have derived new definitions for which the integral of the hardness kernel over the whole space of one of the variables leads to local hardness, and the integral of local hardness over the whole space leads to global hardness. A basic aspect of the present approach is that global hardness keeps its identity as the second derivative of energy with respect to the number of electrons. Local hardness thus obtained depends on the first and second derivatives of energy and electron density with respect to the number of electrons. When these derivatives are approximated by a smooth quadratic interpolation of energy, the expression for local hardness reduces to the one intuitively proposed by Meneses, Tiznado, Contreras and Fuentealba. However, when one combines the first directional derivatives with smooth second derivatives one finds additional terms that allow one to differentiate local hardness for electrophilic attack from the one for nucleophilic attack. Numerical results related to electrophilic attacks on substituted pyridines, substituted benzenes and substituted ethenes are presented to show the overall performance of the new definition.

  4. Antioxidant activity of selenenamide-based mimic as a function of the aromatic thiols nucleophilicity, a DFT-SAPE model.

    Science.gov (United States)

    Kheirabadi, Ramesh; Izadyar, Mohammad

    2018-05-18

    The mechanism of action of the selenenamide 1 as a mimic of the glutathione peroxidase (GPx) was investigated by the density functional theory. The solvent-assisted proton exchange procedure was applied to model the catalytic behavior and antioxidant activity of this mimic. To have an insight into the charge transfer effect, different aromatic thiols, including electron donating substituents on the phenyl ring were considered. The catalytic behavior of the selenenamide was modeled in a four-step mechanism, described by the oxidation of the mimic, the reduction of the obtained product, selenoxide, the reduction of the selenenylsulfide and dehydration of selenenic acid. On the basis of the activation parameters, the final step of the proposed mechanism is the rate determining states of the catalytic cycle. Turnover frequency (TOF) analysis showed that the electron donating groups at the para-position of the phenyl ring of the PhSH do not affect the catalytic activity of the selenenamide in contrast to p-methyl thiophenol which indicates the highest nucleophilicity. The evaluation of the electronic contribution of the various donating groups on the phenyl ring of the aromatic thiols shows that the antioxidant activity of the selenenamide sufficiently increases in the presence of the electron-donating substitutions. Finally, the charge transfer process at the rate-determining state was investigated based on the natural bond orbital analysis. Copyright © 2018 Elsevier Ltd. All rights reserved.

  5. Approaches in Substitution of Organic Solvents

    DEFF Research Database (Denmark)

    Jacobsen, Thomas

    2000-01-01

    In substitution of harmful chemicals or products with less harmful or harmless ones, there are different approaches according to the different situations, the technical requirements to the substitutes, and the goals for the substitution. Three different cases are presented. The substitution process...

  6. The direct aromatization of methane

    Energy Technology Data Exchange (ETDEWEB)

    Marcelin, G.; Oukaci, R.; Migone, R.A.; Kazi, A.M. [Altamira Instruments, Pittsburgh, PA (United States)

    1995-12-31

    The thermal decomposition of methane shows significant potential as a process for the production of higher unsaturated and aromatic hydrocarbons when the extent of the reaction is limited. Thermodynamic calculations have shown that when the reaction is limited to the formation of C{sub 2} to C{sub 10} products, yields of aromatics can exceed 40% at temperatures of 1200{degrees}C. Preliminary experiments have shown that when the reaction is limited to the formation of C{sub 2} to C{sub 10} products, yields of aromatics can exceed 40% at temperatures of 1200{degrees}C. Preliminary experiments have shown that cooling the product and reacting gases as the reaction proceeds can significantly reduce or eliminate the formation of solid carbon and heavier (C{sub 10+}) materials. Much work remains to be done in optimizing the quenching process and this is one of the goals of this program. Means to lower the temperature of the reaction are being studied as this result in a more feasible commercial process due to savings realized in energy and material of construction costs. The use of free-radical generators and catalysts will be investigated as a means of lowering the reaction temperature thus allowing faster quenching. It is highly likely that such studies will lead to a successful direct methane to higher hydrocarbon process.

  7. Nitration of toluene with N[sub 2]O[sub 5

    Energy Technology Data Exchange (ETDEWEB)

    Furukawa, Kikuo.; Yoshizawa, Fujiroku.; Akutsu, Yoshiaki.; Arai, Mitsuru.; Tamura, Masamitsu. (The University of Tokyo, Tokyo (Japan). School of Engineering)

    1999-06-30

    In order to clarify the mechanism of aromatic nitration with N[sub 2]O[sub 5], the nitration of toluene with N[sub 2]O[sub 5] in CCl[sub 4] was carried out and was investigated the yields of the products and the isomer distributions. As a result, the reaction should be very rapid and should involve a typical electrophilic substitution. Moreover, in order to investigate the effect of the solvent, the nitration of toluene with N[sub 2]O[sub 5] powder without CCl[sub 4] was also carried out. The nitration of toluene with N[sub 2]O[sub 5]/N[sub 2]O[sub 4] was also carried out, and the dependence of the isomer distribution and the ratio of produced nitrotoluenes on the ratio of N[sub 2]O[sub 5] was showed. As a result, it is suggested that N[sub 2]O[sub 5] should be dissociated homolytically in CCl[sub 4] and that the aromatic nitration with N[sub 2]O[sub 5] in CCl[sub 4] should proceed with NO[sub 3] as the initial attacking species. The thermal decomposition of N[sub 2]O[sub 5] over 25 degree C should produce a large amount of N[sub 2]O[sub 4](2NO[sub 2]), and the attack of NO[sub 2] on the intermediate [Ar(H)(ONO[sub 2])] should form the intermediates [AR(H)(ONO[sub 2])(H)(NO[sub 2])] following the specific isomer distributions. (author)

  8. Nitration of toluene with N{sub 2}O{sub 5}

    Energy Technology Data Exchange (ETDEWEB)

    Furukawa, Kikuo.; Yoshizawa, Fujiroku.; Akutsu, Yoshiaki.; Arai, Mitsuru.; Tamura, Masamitsu. [The University of Tokyo, Tokyo (Japan). School of Engineering

    1999-06-30

    In order to clarify the mechanism of aromatic nitration with N{sub 2}O{sub 5}, the nitration of toluene with N{sub 2}O{sub 5} in CCl{sub 4} was carried out and was investigated the yields of the products and the isomer distributions. As a result, the reaction should be very rapid and should involve a typical electrophilic substitution. Moreover, in order to investigate the effect of the solvent, the nitration of toluene with N{sub 2}O{sub 5} powder without CCl{sub 4} was also carried out. The nitration of toluene with N{sub 2}O{sub 5}/N{sub 2}O{sub 4} was also carried out, and the dependence of the isomer distribution and the ratio of produced nitrotoluenes on the ratio of N{sub 2}O{sub 5} was showed. As a result, it is suggested that N{sub 2}O{sub 5} should be dissociated homolytically in CCl{sub 4} and that the aromatic nitration with N{sub 2}O{sub 5} in CCl{sub 4} should proceed with NO{sub 3} as the initial attacking species. The thermal decomposition of N{sub 2}O{sub 5} over 25 degree C should produce a large amount of N{sub 2}O{sub 4}(2NO{sub 2}), and the attack of NO{sub 2} on the intermediate [Ar(H)(ONO{sub 2})] should form the intermediates [AR(H)(ONO{sub 2})(H)(NO{sub 2})] following the specific isomer distributions. (author)

  9. STUDY OF FACTORS AFFECTING DEVELOPMENT OF FOOD AROMATIZATION

    Directory of Open Access Journals (Sweden)

    Н.Ye. Dubova

    2017-10-01

    Full Text Available The specific understanding of food philosophy according to the facts of development of cooking technologies and growth rate of food range is given. As it has been proven by historical stages of production of flavorings, aroma is one of the important organoleptic ingredients for food developers. A review of food production based on development of nanotechnologies, as well as promising and cautioning publications on nanotechnologies in the food sector is presented. On the basis of the literary analysis, the future impact of nanotechnologies on the evolution of the aromatization process of food products is predicted. It has been determined that the peculiarity of the development mentioned above lies in the use of plant enzymes and / or flavor precursors in the nanoscale range. The example of enzymatic breakdown of polyunsaturated fatty acids of plant cell membranes as one of the ways of creating fresh flavor of many fruits, namely C6-C9 aldehydes and alcohols, is considered. It is noted that green fresh aromatic ingredients are needed to improve the organoleptic profile of foods from heat-treated vegetables, melons and gourds. The following factors affecting the development of food aromatization are defined: the decreased differentiation of principles of healthy nutrition and fast food, repetition of natural processes of aroma formation, application of wild green leafy vegetables, and evolution of medical nutrition. The information on food aromatization by packing with autonomous mixing and their approximate assortment is given. The innovations in food aromatization are aimed at quality nutrition, time saving, recreation and entertainment, meeting specific needs (vegetarian dishes, restrictive diets.

  10. Ambient aromatic hydrocarbon measurements at Welgegund, South Africa

    Science.gov (United States)

    Jaars, K.; Beukes, J. P.; van Zyl, P. G.; Venter, A. D.; Josipovic, M.; Pienaar, J. J.; Vakkari, V.; Aaltonen, H.; Laakso, H.; Kulmala, M.; Tiitta, P.; Guenther, A.; Hellén, H.; Laakso, L.; Hakola, H.

    2014-07-01

    Aromatic hydrocarbons are associated with direct adverse human health effects and can have negative impacts on ecosystems due to their toxicity, as well as indirect negative effects through the formation of tropospheric ozone and secondary organic aerosol, which affect human health, crop production and regional climate. Measurements of aromatic hydrocarbons were conducted at the Welgegund measurement station (South Africa), which is considered to be a regionally representative background site. However, the site is occasionally impacted by plumes from major anthropogenic source regions in the interior of South Africa, which include the western Bushveld Igneous Complex (e.g. platinum, base metal and ferrochrome smelters), the eastern Bushveld Igneous Complex (platinum and ferrochrome smelters), the Johannesburg-Pretoria metropolitan conurbation (> 10 million people), the Vaal Triangle (e.g. petrochemical and pyrometallurgical industries), the Mpumalanga Highveld (e.g. coal-fired power plants and petrochemical industry) and also a region of anticyclonic recirculation of air mass over the interior of South Africa. The aromatic hydrocarbon measurements were conducted with an automated sampler on Tenax-TA and Carbopack-B adsorbent tubes with heated inlet for 1 year. Samples were collected twice a week for 2 h during daytime and 2 h during night-time. A thermal desorption unit, connected to a gas chromatograph and a mass selective detector was used for sample preparation and analysis. Results indicated that the monthly median (mean) total aromatic hydrocarbon concentrations ranged between 0.01 (0.011) and 3.1 (3.2) ppb. Benzene levels did not exceed the local air quality standard limit, i.e. annual mean of 1.6 ppb. Toluene was the most abundant compound, with an annual median (mean) concentration of 0.63 (0.89) ppb. No statistically significant differences in the concentrations measured during daytime and night-time were found, and no distinct seasonal patterns were

  11. Medicineringsfejl ved generisk substitution

    DEFF Research Database (Denmark)

    Rölfing, Jan

    2012-01-01

    Generic substitution is a major cause of medical mistakes in the general population. Danish legislation obligates pharmacies to substitute prescribed medicine with the cheapest equivalent formulation, despite variations in product name, packaging, shape and colour. Consequently, medical mistakes...... occur. Scientific evidence on the consequences of generic substitution is sparse. Call upon fellow health workers to report medical mistakes to the national entities and scientific peers, in order to increase awareness and scientific evidence about the problem....

  12. Applications of electrochemically-modulated liquid chromatography (EMLC): Separations of aromatic amino acids and polycyclic aromatic hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Li [Iowa State Univ., Ames, IA (United States)

    1998-03-27

    The research in this thesis explores the separation capabilities of a new technique termed electrochemically-modulated liquid chromatography (EMLC). The thesis begins with a general introduction section which provides a literature review of this technique as well as a brief background discussion of the two research projects in each of the next two chapters. The two papers which follow investigate the application of EMLC to the separation of a mixture of aromatic amino acids and of a mixture of polycyclic aromatic hydrocarbons (PAHs). The last section presents general conclusions and summarizes the thesis. References are compiled in the reference section of each chapter. The two papers have been removed for separate processing.

  13. X-ray structure determination of new monomers to establish their polymerizability: copolymerization of two tetrasubstituted electrophilic olefins with electron-rich styrenes giving polymers with an average 1.25 functional groups per chain carbon atom

    International Nuclear Information System (INIS)

    Hall, H.K. Jr.; Reineke, K.E.; Ried, J.H.; Sentman, R.C.; Miller, D.

    1982-01-01

    X-ray crystal structure determination for two tetrasubstituted electrophilic olefins, tetramethyl ethylenetetracarboxylate TMET and dimethyl dicyanofumarate DDCF, revealed two fundamentally different molecular structures. TMET is a nonplanar molecule that possesses two opposite ester groups planar and the others above and below the molecular plane. In contrast, DDCF is a molecule for which both ester groups lie in the plane of the double bond and nitrile groups. DDCF underwent thermal spontaneous copolymerization with electron-rich styrenes to give 1:1 alternating copolymers in moderate yields and molecular weights. These copolymers, which result from the first copolymerization of a tetrasubstituted olefin, possess an average functionality of 1.25 per chain carbon atom. Polymerization is made possible by low steric hindrance and the high delocalization in the propagating radical. The yields were limited by competing cycloaddition reaction. The corresponding diethyl ester also copolymerized, but not so well. Neither electrophilic olefin homopolymerized under γ-irradiation. TMET did not copolymerize at all when treated under identical conditions

  14. Key aromatic/hydrophobic amino acids controlling a cross-amyloid peptide interaction versus amyloid self-assembly.

    Science.gov (United States)

    Bakou, Maria; Hille, Kathleen; Kracklauer, Michael; Spanopoulou, Anna; Frost, Christina V; Malideli, Eleni; Yan, Li-Mei; Caporale, Andrea; Zacharias, Martin; Kapurniotu, Aphrodite

    2017-09-01

    The interaction of the intrinsically disordered polypeptide islet amyloid polypeptide (IAPP), which is associated with type 2 diabetes (T2D), with the Alzheimer's disease amyloid-β (Aβ) peptide modulates their self-assembly into amyloid fibrils and may link the pathogeneses of these two cell-degenerative diseases. However, the molecular determinants of this interaction remain elusive. Using a systematic alanine scan approach, fluorescence spectroscopy, and other biophysical methods, including heterocomplex pulldown assays, far-UV CD spectroscopy, the thioflavin T binding assay, transmission EM, and molecular dynamics simulations, here we identified single aromatic/hydrophobic residues within the amyloid core IAPP region as hot spots or key residues of its cross-interaction with Aβ40(42) peptide. Importantly, we also find that none of these residues in isolation plays a key role in IAPP self-assembly, whereas simultaneous substitution of four aromatic/hydrophobic residues with Ala dramatically impairs both IAPP self-assembly and hetero-assembly with Aβ40(42). Furthermore, our experiments yielded several novel IAPP analogs, whose sequences are highly similar to that of IAPP but have distinct amyloid self- or cross-interaction potentials. The identified similarities and major differences controlling IAPP cross-peptide interaction with Aβ40(42) versus its amyloid self-assembly offer a molecular basis for understanding the underlying mechanisms. We propose that these insights will aid in designing intervention strategies and novel IAPP analogs for the management of type 2 diabetes, Alzheimer's disease, or other diseases related to IAPP dysfunction or cross-amyloid interactions. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

  15. A Successful Attempt to Obtain the Linear Dependence Between One-Photon and Two-Photon Spectral Properties and Hammett Parameters of Various Aromatic Substituents in New π-Extended Asymmetric Organic Chromophores.

    Science.gov (United States)

    Hu, Nvdan; Gong, Yulong; Wang, Xinchao; Lu, Yao; Peng, Guangyue; Yang, Long; Zhang, Shengtao; Luo, Ziping; Li, Hongru; Gao, Fang

    2015-11-01

    A series of new asymmetric chromophores containing aromatic substituents and possessing the excellent π-extension in space were prepared through multi-steps routes. One-photon and two-photon spectral properties of these new chromophores could be tuned by these substituents finely and simultaneously. The linear correlation of the wave numbers of the one-photon absorption and emission maxima to Hammett parameters of these substituents was presented. Near infrared two-photon absorption emission integrated areas of the target chromophores were correlated linearly to Hammett constants of these substituted groups.

  16. The in vitro screening of aromatic amides as potential inhibitors of poly (ADP-ribose) polymerase

    International Nuclear Information System (INIS)

    Brown, D.M.; Horsman, M.R.; Lee, W.W.; Brown, J.M.

    1984-01-01

    It is now well established that the chromosomal enzyme poly (ADP-ribose) polymerase (ADPRP) is involved in the repair of DNA damage caused by ionizing radiation and alkylating agents, although the mechanisms involved are still not clear. ADPRP inhibitors include thymidine, nicotinamides, benzamides and methyl xanthines. The authors have demonstrated that these compounds are effective inhibitors of X-ray-induced potentially lethal damage repair (PLDR). More recently, they have shown that the cytotoxicity of the bifunctional alkylating L-phenylalanine mustard (L-PAM) was enhanced in vitro and in vivo by 3-aminobenzamide, nicotinamide and caffeine, although in the latter case pharmacokinetic changes could have contributed to the enhanced killing. The authors have examined a series of substituted carbocyclic and heterocyclic aromatic amides as potential inhibitors of ADPRP. The effect of these compounds on ADPRP activity in vitro as well as their effect on the repair of X-ray and alkylation damage in vitro are presented

  17. Solvent substitution

    International Nuclear Information System (INIS)

    1990-01-01

    The DOE Environmental Restoration and Waste Management Office of Technology Development and the Air Force Engineering and Services Center convened the First Annual International Workshop on Solvent Substitution on December 4--7, 1990. The primary objectives of this joint effort were to share information and ideas among attendees in order to enhance the development and implementation of required new technologies for the elimination of pollutants associated with industrial use of hazardous and toxic solvents; and to aid in accelerating collaborative efforts and technology transfer between government and industry for solvent substitution. There were workshop sessions focusing on Alternative Technologies, Alternative Solvents, Recovery/Recycling, Low VOC Materials and Treatment for Environmentally Safe Disposal. The 35 invited papers presented covered a wide range of solvent substitution activities including: hardware and weapons production and maintenance, paint stripping, coating applications, printed circuit boards, metal cleaning, metal finishing, manufacturing, compliance monitoring and process control monitoring. This publication includes the majority of these presentations. In addition, in order to further facilitate information exchange and technology transfer, the US Air Force and DOE solicited additional papers under a general ''Call for Papers.'' These papers, which underwent review and final selection by a peer review committee, are also included in this combined Proceedings/Compendium. For those involved in handling, using or managing hazardous and toxic solvents, this document should prove to be a valuable resource, providing the most up-to-date information on current technologies and practices in solvent substitution. Individual papers are abstracted separated

  18. Improvement of activity and stability of Chondroitinase ABC I by introducing an aromatic cluster at the surface of protein.

    Science.gov (United States)

    Shahaboddin, Mohammad Esmaeil; Khajeh, Khosro; Maleki, Monireh; Golestani, Abolfazl

    2017-10-01

    Chondroitinase ABC I (ChABC I) has been shown to depolymerize a variety of glycosaminoglycan substrates and promote regeneration of damaged spinal cord. However, to date, intrathecal delivery methods have been suboptimal largely due to enzyme instability which necessitates repeated administration to the injured loci. Among the aromatic amino acids, tyrosine has been shown to be more effective in creation of stable clusters and further stabilize of the proteins. Bioinformatics approaches have been used to examine the effect of an extra aromatic cluster at the surface of ChABC I. In this study two amino acids i.e., Asn 806 and Gln 810 were mutated to tyrosine and to alanine as negative control. In this way, four variants i.e., N806Y/Q810Y, N806A/Q810Y, N806Y/Q810A and N806A/Q810A were created. The results showed that N806Y/Q810Y mutation improved both activity and thermal stability of the enzyme while Ala substitution reduced the enzyme activity and destabilized it. Structural analysis of mutants showed an increase in intrinsic fluorescence intensity and secondary structure content of N806Y/Q810Y mutant when compared to the wild type enzyme indicating a more rigid structure of this variant. Moreover, the N806Y/Q810Y enzyme displayed a remarkable resistance against trypsin degradation with a half-life (t 1/2 ) of 45.0min versus 32.5min of wild-type. In conclusion, the data revealed that structural features and activity of ChABC I can be improved by introducing appropriate aromatic clusters at the surface of the enzyme. Copyright © 2017 Elsevier Inc. All rights reserved.

  19. Volatile Compounds in Dry Dog Foods and Their Influence on Sensory Aromatic Profile

    Directory of Open Access Journals (Sweden)

    Koushik Adhikari

    2013-02-01

    Full Text Available The aim of this study was to determine volatile compounds in dry dog foods and their possible influence on sensory aromatic profile. Grain-free dry dog foods were compared to dry dog foods manufactured with grain, but also with different protein sources for their aromatic volatiles. Solid-phase microextraction/gas chromatography/mass spectrometry was used to determine the aromatic compounds present in the headspace of these samples. Partial Least Squares regression was performed to correlate the instrumental aromatic data with the descriptive aroma analysis data. A total of 54 aromatic compounds were tentatively identified in the dry dog food samples, with aldehydes and ketones being the most represented organic volatiles group. Grain-added products were on the average higher in total volatiles than grain-free products. Partial Least Squares regression analysis indicated possible connections with sensory aromatic profile and grain-added samples, such as rancid aroma and aldehydes, especially hexanal. The results of this study showed that dry dog foods are products with complex odor characteristics and that grain-free products are less aromatic.

  20. The Effect of n vs. iso Isomerization on the Thermophysical Properties of Aromatic and Non-aromatic Ionic Liquids.

    Science.gov (United States)

    Rodrigues, Ana S M C; Almeida, Hugo F D; Freire, Mara G; Lopes-da-Silva, José A; Coutinho, João A P; Santos, Luís M N B F

    2016-09-15

    This work explores the n vs. iso isomerization effects on the physicochemical properties of different families of ionic liquids (ILs) with variable aromaticity and ring size. This study comprises the experimental measurements, in a wide temperature range, of the ILs' thermal behavior, heat capacities, densities, refractive indices, surface tensions, and viscosities. The results here reported show that the presence of the iso -alkyl group leads to an increase of the temperature of the glass transition, T g . The iso- pyrrolidinium (5 atoms ring cation core) and iso -piperidinium (6 atoms ring cation core) ILs present a strong differentiation in the enthalpy and entropy of melting. Non-aromatic ILs have higher molar heat capacities due to the increase of the atomic contribution, whereas it was not found any significant differentiation between the n and iso -alkyl isomers. A small increase of the surface tension was observed for the non-aromatic ILs, which could be related to their higher cohesive energy of the bulk, while the lower surface entropy observed for the iso isomers indicates a structural resemblance between the IL bulk and surface. The significant differentiation between ILs with a 5 and 6 atoms ring cation in the n -alkyl series (where 5 atoms ring cations have higher surface entropy) is an indication of a more efficient arrangement of the non-polar region at the surface in ILs with smaller cation cores. The ILs constituted by non-aromatic piperidinium cation, and iso -alkyl isomers were found to be the most viscous among the studied ILs due to their higher energy barriers for shear stress.

  1. Classification of Malaysia aromatic rice using multivariate statistical analysis

    Energy Technology Data Exchange (ETDEWEB)

    Abdullah, A. H.; Adom, A. H.; Shakaff, A. Y. Md; Masnan, M. J.; Zakaria, A.; Rahim, N. A. [School of Mechatronic Engineering, Universiti Malaysia Perlis, Kampus Pauh Putra, 02600 Arau, Perlis (Malaysia); Omar, O. [Malaysian Agriculture Research and Development Institute (MARDI), Persiaran MARDI-UPM, 43400 Serdang, Selangor (Malaysia)

    2015-05-15

    Aromatic rice (Oryza sativa L.) is considered as the best quality premium rice. The varieties are preferred by consumers because of its preference criteria such as shape, colour, distinctive aroma and flavour. The price of aromatic rice is higher than ordinary rice due to its special needed growth condition for instance specific climate and soil. Presently, the aromatic rice quality is identified by using its key elements and isotopic variables. The rice can also be classified via Gas Chromatography Mass Spectrometry (GC-MS) or human sensory panels. However, the uses of human sensory panels have significant drawbacks such as lengthy training time, and prone to fatigue as the number of sample increased and inconsistent. The GC–MS analysis techniques on the other hand, require detailed procedures, lengthy analysis and quite costly. This paper presents the application of in-house developed Electronic Nose (e-nose) to classify new aromatic rice varieties. The e-nose is used to classify the variety of aromatic rice based on the samples odour. The samples were taken from the variety of rice. The instrument utilizes multivariate statistical data analysis, including Principal Component Analysis (PCA), Linear Discriminant Analysis (LDA) and K-Nearest Neighbours (KNN) to classify the unknown rice samples. The Leave-One-Out (LOO) validation approach is applied to evaluate the ability of KNN to perform recognition and classification of the unspecified samples. The visual observation of the PCA and LDA plots of the rice proves that the instrument was able to separate the samples into different clusters accordingly. The results of LDA and KNN with low misclassification error support the above findings and we may conclude that the e-nose is successfully applied to the classification of the aromatic rice varieties.

  2. Classification of Malaysia aromatic rice using multivariate statistical analysis

    Science.gov (United States)

    Abdullah, A. H.; Adom, A. H.; Shakaff, A. Y. Md; Masnan, M. J.; Zakaria, A.; Rahim, N. A.; Omar, O.

    2015-05-01

    Aromatic rice (Oryza sativa L.) is considered as the best quality premium rice. The varieties are preferred by consumers because of its preference criteria such as shape, colour, distinctive aroma and flavour. The price of aromatic rice is higher than ordinary rice due to its special needed growth condition for instance specific climate and soil. Presently, the aromatic rice quality is identified by using its key elements and isotopic variables. The rice can also be classified via Gas Chromatography Mass Spectrometry (GC-MS) or human sensory panels. However, the uses of human sensory panels have significant drawbacks such as lengthy training time, and prone to fatigue as the number of sample increased and inconsistent. The GC-MS analysis techniques on the other hand, require detailed procedures, lengthy analysis and quite costly. This paper presents the application of in-house developed Electronic Nose (e-nose) to classify new aromatic rice varieties. The e-nose is used to classify the variety of aromatic rice based on the samples odour. The samples were taken from the variety of rice. The instrument utilizes multivariate statistical data analysis, including Principal Component Analysis (PCA), Linear Discriminant Analysis (LDA) and K-Nearest Neighbours (KNN) to classify the unknown rice samples. The Leave-One-Out (LOO) validation approach is applied to evaluate the ability of KNN to perform recognition and classification of the unspecified samples. The visual observation of the PCA and LDA plots of the rice proves that the instrument was able to separate the samples into different clusters accordingly. The results of LDA and KNN with low misclassification error support the above findings and we may conclude that the e-nose is successfully applied to the classification of the aromatic rice varieties.

  3. Classification of Malaysia aromatic rice using multivariate statistical analysis

    International Nuclear Information System (INIS)

    Abdullah, A. H.; Adom, A. H.; Shakaff, A. Y. Md; Masnan, M. J.; Zakaria, A.; Rahim, N. A.; Omar, O.

    2015-01-01

    Aromatic rice (Oryza sativa L.) is considered as the best quality premium rice. The varieties are preferred by consumers because of its preference criteria such as shape, colour, distinctive aroma and flavour. The price of aromatic rice is higher than ordinary rice due to its special needed growth condition for instance specific climate and soil. Presently, the aromatic rice quality is identified by using its key elements and isotopic variables. The rice can also be classified via Gas Chromatography Mass Spectrometry (GC-MS) or human sensory panels. However, the uses of human sensory panels have significant drawbacks such as lengthy training time, and prone to fatigue as the number of sample increased and inconsistent. The GC–MS analysis techniques on the other hand, require detailed procedures, lengthy analysis and quite costly. This paper presents the application of in-house developed Electronic Nose (e-nose) to classify new aromatic rice varieties. The e-nose is used to classify the variety of aromatic rice based on the samples odour. The samples were taken from the variety of rice. The instrument utilizes multivariate statistical data analysis, including Principal Component Analysis (PCA), Linear Discriminant Analysis (LDA) and K-Nearest Neighbours (KNN) to classify the unknown rice samples. The Leave-One-Out (LOO) validation approach is applied to evaluate the ability of KNN to perform recognition and classification of the unspecified samples. The visual observation of the PCA and LDA plots of the rice proves that the instrument was able to separate the samples into different clusters accordingly. The results of LDA and KNN with low misclassification error support the above findings and we may conclude that the e-nose is successfully applied to the classification of the aromatic rice varieties

  4. Development of short and highly potent self-assembling elastin-derived pentapeptide repeats containing aromatic amino acid residues.

    Science.gov (United States)

    Taniguchi, Suguru; Watanabe, Noriko; Nose, Takeru; Maeda, Iori

    2016-01-01

    Tropoelastin is the primary component of elastin, which forms the elastic fibers that make up connective tissues. The hydrophobic domains of tropoelastin are thought to mediate the self-assembly of elastin into fibers, and the temperature-mediated self-assembly (coacervation) of one such repetitive peptide sequence (VPGVG) has been utilized in various bio-applications. To elucidate a mechanism for coacervation activity enhancement and to develop more potent coacervatable elastin-derived peptides, we synthesized two series of peptide analogs containing an aromatic amino acid, Trp or Tyr, in addition to Phe-containing analogs and tested their functional characteristics. Thus, position 1 of the hydrophobic pentapeptide repeat of elastin (X(1)P(2)G(3)V(4)G(5)) was substituted by Trp or Tyr. Eventually, we acquired a novel, short Trp-containing elastin-derived peptide analog (WPGVG)3 with potent coacervation ability. From the results obtained during this process, we determined the importance of aromaticity and hydrophobicity for the coacervation potency of elastin-derived peptide analogs. Generally, however, the production of long-chain synthetic polypeptides in quantities sufficient for commercial use remain cost-prohibitive. Therefore, the identification of (WPGVG)3, which is a 15-mer short peptide consisting simply of five natural amino acids and shows temperature-dependent self-assembly activity, might serve as a foundation for the development of various kinds of biomaterials. Copyright © 2015 European Peptide Society and John Wiley & Sons, Ltd.

  5. Polycyclic Aromatic Hydrocarbons as Plausible Prebiotic Membrane Components

    Science.gov (United States)

    Groen, Joost; Deamer, David W.; Kros, Alexander; Ehrenfreund, Pascale

    2012-08-01

    Aromatic molecules delivered to the young Earth during the heavy bombardment phase in the early history of our solar system were likely to be among the most abundant and stable organic compounds available. The Aromatic World hypothesis suggests that aromatic molecules might function as container elements, energy transduction elements and templating genetic components for early life forms. To investigate the possible role of aromatic molecules as container elements, we incorporated different polycyclic aromatic hydrocarbons (PAH) in the membranes of fatty acid vesicles. The goal was to determine whether PAH could function as a stabilizing agent, similar to the role that cholesterol plays in membranes today. We studied vesicle size distribution, critical vesicle concentration and permeability of the bilayers using C6-C10 fatty acids mixed with amphiphilic PAH derivatives such as 1-hydroxypyrene, 9-anthracene carboxylic acid and 1,4 chrysene quinone. Dynamic Light Scattering (DLS) spectroscopy was used to measure the size distribution of vesicles and incorporation of PAH species was established by phase-contrast and epifluorescence microscopy. We employed conductimetric titration to determine the minimal concentration at which fatty acids could form stable vesicles in the presence of PAHs. We found that oxidized PAH derivatives can be incorporated into decanoic acid (DA) vesicle bilayers in mole ratios up to 1:10 (PAH:DA). Vesicle size distribution and critical vesicle concentration were largely unaffected by PAH incorporation, but 1-hydroxypyrene and 9-anthracene carboxylic acid lowered the permeability of fatty acid bilayers to small solutes up to 4-fold. These data represent the first indication of a cholesterol-like stabilizing effect of oxidized PAH derivatives in a simulated prebiotic membrane.

  6. Aromatic claw: A new fold with high aromatic content that evades structural prediction: Aromatic Claw

    Energy Technology Data Exchange (ETDEWEB)

    Sachleben, Joseph R. [Biomolecular NMR Core Facility, University of Chicago, Chicago Illinois; Adhikari, Aashish N. [Department of Chemistry, University of Chicago, Chicago Illinois; Gawlak, Grzegorz [Department of Biochemistry and Molecular Biology, University of Chicago, Chicago Illinois; Hoey, Robert J. [Department of Biochemistry and Molecular Biology, University of Chicago, Chicago Illinois; Liu, Gaohua [Northeast Structural Genomics Consortium (NESG), Department of Molecular Biology and Biochemistry, School of Arts and Sciences, and Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, and Center for Advanced Biotechnology and Medicine, Rutgers, The State University of New Jersey, Piscataway New Jersey; Joachimiak, Andrzej [Department of Biochemistry and Molecular Biology, University of Chicago, Chicago Illinois; Biological Sciences Division, Argonne National Laboratory, Argonne Illinois; Montelione, Gaetano T. [Northeast Structural Genomics Consortium (NESG), Department of Molecular Biology and Biochemistry, School of Arts and Sciences, and Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, and Center for Advanced Biotechnology and Medicine, Rutgers, The State University of New Jersey, Piscataway New Jersey; Sosnick, Tobin R. [Department of Biochemistry and Molecular Biology, University of Chicago, Chicago Illinois; Koide, Shohei [Department of Biochemistry and Molecular Biology, University of Chicago, Chicago Illinois; Department of Biochemistry and Molecular Pharmacology and the Perlmutter Cancer Center, New York University School of Medicine, New York New York

    2016-11-10

    We determined the NMR structure of a highly aromatic (13%) protein of unknown function, Aq1974 from Aquifex aeolicus (PDB ID: 5SYQ). The unusual sequence of this protein has a tryptophan content five times the normal (six tryptophan residues of 114 or 5.2% while the average tryptophan content is 1.0%) with the tryptophans occurring in a WXW motif. It has no detectable sequence homology with known protein structures. Although its NMR spectrum suggested that the protein was rich in β-sheet, upon resonance assignment and solution structure determination, the protein was found to be primarily α-helical with a small two-stranded β-sheet with a novel fold that we have termed an Aromatic Claw. As this fold was previously unknown and the sequence unique, we submitted the sequence to CASP10 as a target for blind structural prediction. At the end of the competition, the sequence was classified a hard template based model; the structural relationship between the template and the experimental structure was small and the predictions all failed to predict the structure. CSRosetta was found to predict the secondary structure and its packing; however, it was found that there was little correlation between CSRosetta score and the RMSD between the CSRosetta structure and the NMR determined one. This work demonstrates that even in relatively small proteins, we do not yet have the capacity to accurately predict the fold for all primary sequences. The experimental discovery of new folds helps guide the improvement of structural prediction methods.

  7. Metal Triflates for the Production of Aromatics from Lignin.

    Science.gov (United States)

    Deuss, Peter J; Lahive, Ciaran W; Lancefield, Christopher S; Westwood, Nicholas J; Kamer, Paul C J; Barta, Katalin; de Vries, Johannes G

    2016-10-20

    The depolymerization of lignin into valuable aromatic chemicals is one of the key goals towards establishing economically viable biorefineries. In this contribution we present a simple approach for converting lignin to aromatic monomers in high yields under mild reaction conditions. The methodology relies on the use of catalytic amounts of easy-to-handle metal triflates (M(OTf) x ). Initially, we evaluated the reactivity of a broad range of metal triflates using simple lignin model compounds. More advanced lignin model compounds were also used to study the reactivity of different lignin linkages. The product aromatic monomers were either phenolic C2-acetals obtained by stabilization of the aldehyde cleavage products by reaction with ethylene glycol or methyl aromatics obtained by catalytic decarbonylation. Notably, when the method was ultimately tested on lignin, especially Fe(OTf) 3 proved very effective and the phenolic C2-acetal products were obtained in an excellent, 19.3±3.2 wt % yield. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. A neurotoxicity assessment of high flash aromatic naphtha.

    Science.gov (United States)

    Douglas, J F; McKee, R H; Cagen, S Z; Schmitt, S L; Beatty, P W; Swanson, M S; Schreiner, C A; Ulrich, C E; Cockrell, B Y

    1993-01-01

    Catalytic reforming is a refining process that converts naphthenes to aromatics by dehydrogenation to make higher octane gasoline blending components. A portion of this wide-boiling range hydrocarbon stream can be separated by distillation and used for other purposes. One such application is a mixture of predominantly 9-carbon aromatic molecules (C9 Aromatics, primarily isomers of ethyltoluene and trimethylbenzene), which is removed and used as a solvent also known as High Flash Aromatic Naphtha (HFAN). A program was initiated to assess the toxicological properties of HFAN since there may be human exposure, especially in the workplace. The current study was conducted to assess the potential for neurotoxicity in the rat. Adult male Sprague-Dawley rats of approximately 300 grams body weight, in groups of twenty, were exposed by inhalation to HFAN for 90 days at concentrations of 0, 100, 500, and 1500 ppm. During this period the animals were tested monthly for motor activity and in a functional observation battery. After three months of exposure, for 6 hours/day, 5 days/week, 10 animals/group/sex were sacrificed and selected nervous system tissue was examined histopathologically. No signs of neurotoxicity were seen in any of the evaluated parameters, nor was there evidence of pathologic changes in any of the examined tissues.

  9. CO Reduction to CH3OSiMe3: Electrophile-Promoted Hydride Migration at a Single Fe Site.

    Science.gov (United States)

    Deegan, Meaghan M; Peters, Jonas C

    2017-02-22

    One of the major challenges associated with developing molecular Fischer-Tropsch catalysts is the design of systems that promote the formation of C-H bonds from H 2 and CO while also facilitating the release of the resulting CO-derived organic products. To this end, we describe the synthesis of reduced iron-hydride/carbonyl complexes that enable an electrophile-promoted hydride migration process, resulting in the reduction of coordinated CO to a siloxymethyl (L n Fe-CH 2 OSiMe 3 ) group. Intramolecular hydride-to-CO migrations are extremely rare, and to our knowledge the system described herein is the first example where such a process can be accessed from a thermally stable M(CO)(H) complex. Further addition of H 2 to L n Fe-CH 2 OSiMe 3 releases CH 3 OSiMe 3 , demonstrating net four-electron reduction of CO to CH 3 OSiMe 3 at a single Fe site.

  10. Silicone elastomers with covalently incorporated aromatic voltage stabilisers

    DEFF Research Database (Denmark)

    A Razak, Aliff Hisyam; Skov, Anne Ladegaard

    2017-01-01

    to the incorporationof an aromatic voltage stabiliser, were prepared by cross-linking synthesised polydimethylsiloxane–polyphenylmethylsiloxane (PDMS–PPMS) copolymers. PPMS possesses voltage stabilisation capabilitiesbut is immiscible in PDMS, and thus the copolymerisation of the two components was necessary...... forhomogeneity. Concentrations of the voltage stabiliser were varied by changing the molecular weights ofthe PPMS in the copolymer. The developed elastomers were inherently soft with enhanced electricalbreakdown strengths, due to delocalisedp-electrons of the aromatic constituent. An optimumconcentration...

  11. 40 CFR Appendix D to Subpart G of... - Substitutes Subject to Use Restrictions and Unacceptable Substitutes

    Science.gov (United States)

    2010-07-01

    ... the following criteria, derived from Society of Automotive Engineers (SAE) standards and recommended... Substitutes] Application Substitute Decision Conditions Comments Electronics Cleaning w/CFC-113 and MCF HFC... Sector [Acceptable Subject to Narrowed Use Limits] Application Substitute Decision Comments Electronics...

  12. Optimal ordering quantities for substitutable deteriorating items under joint replenishment with cost of substitution

    Science.gov (United States)

    Mishra, Vinod Kumar

    2017-09-01

    In this paper we develop an inventory model, to determine the optimal ordering quantities, for a set of two substitutable deteriorating items. In this inventory model the inventory level of both items depleted due to demands and deterioration and when an item is out of stock, its demands are partially fulfilled by the other item and all unsatisfied demand is lost. Each substituted item incurs a cost of substitution and the demands and deterioration is considered to be deterministic and constant. Items are order jointly in each ordering cycle, to take the advantages of joint replenishment. The problem is formulated and a solution procedure is developed to determine the optimal ordering quantities that minimize the total inventory cost. We provide an extensive numerical and sensitivity analysis to illustrate the effect of different parameter on the model. The key observation on the basis of numerical analysis, there is substantial improvement in the optimal total cost of the inventory model with substitution over without substitution.

  13. pH-dependent equilibrium isotope fractionation associated with the compound specific nitrogen and carbon isotope analysis of substituted anilines by SPME-GC/IRMS.

    Science.gov (United States)

    Skarpeli-Liati, Marita; Turgeon, Aurora; Garr, Ashley N; Arnold, William A; Cramer, Christopher J; Hofstetter, Thomas B

    2011-03-01

    Solid-phase microextraction (SPME) coupled to gas chromatography/isotope ratio mass spectrometry (GC/IRMS) was used to elucidate the effects of N-atom protonation on the analysis of N and C isotope signatures of selected aromatic amines. Precise and accurate isotope ratios were measured using polydimethylsiloxane/divinylbenzene (PDMS/DVB) as the SPME fiber material at solution pH-values that exceeded the pK(a) of the substituted aniline's conjugate acid by two pH-units. Deviations of δ(15)N and δ(13)C-values from reference measurements by elemental analyzer IRMS were small (IRMS. Under these conditions, the detection limits for accurate isotope ratio measurements were between 0.64 and 2.1 mg L(-1) for δ(15)N and between 0.13 and 0.54 mg L(-1) for δ(13)C, respectively. Substantial inverse N isotope fractionation was observed by SPME-GC/IRMS as the fraction of protonated species increased with decreasing pH leading to deviations of -20‰ while the corresponding δ(13)C-values were largely invariant. From isotope ratio analysis at different solution pHs and theoretical calculations by density functional theory, we derived equilibrium isotope effects, EIEs, pertinent to aromatic amine protonation of 0.980 and 1.001 for N and C, respectively, which were very similar for all compounds investigated. Our work shows that N-atom protonation can compromise accurate compound-specific N isotope analysis of aromatic amines.

  14. Asymmetric synthesis of all-carbon benzylic quaternary stereocenters via Cu-catalyzed conjugate addition of dialkylzinc reagents to 5-(1-arylalkylidene) Meldrum's acids.

    Science.gov (United States)

    Fillion, Eric; Wilsily, Ashraf

    2006-03-08

    The asymmetric synthesis of all-carbon benzylic quaternary stereocenters has been successfully achieved through copper-catalyzed addition of dialkylzinc reagents to 5-(1-arylalkylidene) and 5-(dihydroindenylidene) Meldrum's acids in the presence of phosphoramidite ligand. The resulting benzyl-substituted Meldrum's acids and 1,1-disubstituted indanes were obtained in good yields and up to 99% ee. The significance of substituting the position para, meta, and ortho to the electrophilic benzylic center was highlighted. A benzyl Meldrum's acid product was further transformed to a 3,3-disubstituted 1-indanone and a beta,beta-disubstituted pentanoic acid.

  15. Lewis base catalyzed 1,3-dithiane addition to carbonyl and imino compounds using 2-trimethylsilyl-1,3-dithiane.

    Science.gov (United States)

    Michida, Makoto; Mukaiyama, Teruaki

    2008-09-01

    Lewis base-catalyzed 1,3-dithiane addition to electrophiles such as carbonyl compounds and N-substituted aldimines with 2-trimethylsilyl-1,3-dithiane (TMS-dithiane) is described. By the activation of the carbon-silicon bond in the presence of a Lewis base catalyst such as tetrabutylammonium phenoxide (PhONnBu(4)), a 1,3-dithiane addition reaction proceeded smoothly to afford the corresponding adducts in good to high yields under mild conditions. This synthesis is also applied to the reactions of ketones having alpha-protons, and of N-substituted aldimines.

  16. Role of Hydrophobic/Aromatic Residues on the Stability of Double-Wall β-Sheet Structures Formed by a Triblock Peptide.

    Science.gov (United States)

    Ozgur, Beytullah; Sayar, Mehmet

    2017-04-27

    Bioinspired self-assembling peptides serve as powerful building blocks in the manufacturing of nanomaterials with tailored features. Because of their ease of synthesis, biocompatibility, and tunable activity, this emerging branch of biomolecules has become very popular. The triblock peptide architecture designed by the Hartgerink group is a versatile system that allows control over its assembly and has been shown to demonstrate tunable bioactivity. Three main forces, Coulomb repulsion, hydrogen bonding and hydrophobicity act together to guide the triblock peptides' assembly into one-dimensional objects and hydrogels. It was shown previously that both the nanofiber morphology (e.g., intersheet spacing, formation of antiparallel/parallel β-sheets) and hydrogel rheology strictly depend on the choice of the core residue where the triblock peptide fibers with aromatic cores in general form shorter fibers and yield poor hydrogels with respect to the ones with aliphatic cores. However, an elaborate understanding of the molecular reasons behind these changes remained unclear. In this study, by using carefully designed computer based free energy calculations, we analyzed the influence of the core residue on the formation of double-wall fibers and single-wall β-sheets. Our results demonstrate that the aromatic substitution impairs the fiber cores and this impairment is mainly associated with a reduced hydrophobic character of the aromatic side chains. Such weakening is most obvious in tryptophan containing peptides where the fiber core absorbs a significant amount of water. We also show that the ability of tyrosine to form side chain hydrogen bonds plays an indispensable role in the fiber stability. As opposed to the impairment of the fiber cores, single-wall β-sheets with aromatic faces become more stable compared to the ones with aliphatic faces suggesting that the choice of the core residue can also affect the underlying assembly mechanism. We also provide an in

  17. Attenuation of dissolved aromatic hydrocarbons from residual gasoline : source depletion and bioattenuation controls

    Energy Technology Data Exchange (ETDEWEB)

    Freitas, J.; Yang, T.; Barker, J. [Waterloo Univ., ON (Canada). Dept. of Earth and Environmental Sciences; Mocanu, M. [CH2M Hill Engineering Ltd., Santa Ana, CA (United States); Molson, J. [Ecole Polytechnique, Montreal, PQ (Canada). Dept. of Civil, Mining and Geological Engineering

    2008-07-01

    It has become commonplace to add ethanol to normal gasoline because this oxygenate has been touted to reduce greenhouse gas emissions, improve air quality and reduce dependence on non-renewable fossil fuels. It is advantageous from a groundwater quality perspective to substitute ethanol for soluble, toxic and mobile monoaromatics such as benzene, toluene, ethylbenzene and xylenes (BTEX). Ethanol poses minimal direct environmental risk, other than the high biological oxygen demand (BOD) imposed on receiving waters. This paper addressed the misconception that fermentation of ethanol to acetate or methane removes this BOD, thus eliminating ethanol as a competitor with BTEX for electron transfers. A study was conducted in which 50 litres each of normal gasoline and gasoline with 10 per cent ethanol (E10) were placed below the water table in a shallow sand aquifer at Canadian Forces Base (CFB) Borden. Two years of monitoring the downgradient plume revealed that the aromatic hydrocarbon were naturally attenuated. Although the rate of mass depletion in gasoline sources could not be predicted from the core analysis and simple interpretations, the biodegradation rate was well captured. It was concluded that the extent of bioattenuation exceeds that predicted by models considering electron acceptor (oxygen) availability. Ethanol was rapidly biotransformed in the Borden aquifer. It did not seem to impair the biotransformation of benzene when both were derived from E10 gasoline. The study revealed that for homogeneous sand aquifers such as Borden, the heterogeneity of sources will likely be a key cause of heterogeneous pollutant distribution in the downgradient plume. Ongoing research will focus on resolving the issue of insufficient oxygen to account for complete mineralization of ethanol and biotransformed aromatics. 14 refs., 1 tab., 7 figs.

  18. Solvent substitution

    Energy Technology Data Exchange (ETDEWEB)

    1990-01-01

    The DOE Environmental Restoration and Waste Management Office of Technology Development and the Air Force Engineering and Services Center convened the First Annual International Workshop on Solvent Substitution on December 4--7, 1990. The primary objectives of this joint effort were to share information and ideas among attendees in order to enhance the development and implementation of required new technologies for the elimination of pollutants associated with industrial use of hazardous and toxic solvents; and to aid in accelerating collaborative efforts and technology transfer between government and industry for solvent substitution. There were workshop sessions focusing on Alternative Technologies, Alternative Solvents, Recovery/Recycling, Low VOC Materials and Treatment for Environmentally Safe Disposal. The 35 invited papers presented covered a wide range of solvent substitution activities including: hardware and weapons production and maintenance, paint stripping, coating applications, printed circuit boards, metal cleaning, metal finishing, manufacturing, compliance monitoring and process control monitoring. This publication includes the majority of these presentations. In addition, in order to further facilitate information exchange and technology transfer, the US Air Force and DOE solicited additional papers under a general Call for Papers.'' These papers, which underwent review and final selection by a peer review committee, are also included in this combined Proceedings/Compendium. For those involved in handling, using or managing hazardous and toxic solvents, this document should prove to be a valuable resource, providing the most up-to-date information on current technologies and practices in solvent substitution. Individual papers are abstracted separated.

  19. Aliphatic-aromatic separation using deep eutectic solvents as extracting agents

    NARCIS (Netherlands)

    Rodriguez Rodriguez, Nerea; Fernandez Requejo, Patricia; Kroon, Maaike

    2015-01-01

    The separation of aliphatic and aromatic compounds is a great challenge for chemical engineers. There is no efficient separation process for mixtures with compositions lower than 20 wt % in aromatics. In this work, the feasibility of two different deep eutectic solvents (DESs) as novel extracting

  20. Statistical Physics of Complex Substitutive Systems

    Science.gov (United States)

    Jin, Qing

    Diffusion processes are central to human interactions. Despite extensive studies that span multiple disciplines, our knowledge is limited to spreading processes in non-substitutive systems. Yet, a considerable number of ideas, products, and behaviors spread by substitution; to adopt a new one, agents must give up an existing one. This captures the spread of scientific constructs--forcing scientists to choose, for example, a deterministic or probabilistic worldview, as well as the adoption of durable items, such as mobile phones, cars, or homes. In this dissertation, I develop a statistical physics framework to describe, quantify, and understand substitutive systems. By empirically exploring three collected high-resolution datasets pertaining to such systems, I build a mechanistic model describing substitutions, which not only analytically predicts the universal macroscopic phenomenon discovered in the collected datasets, but also accurately captures the trajectories of individual items in a complex substitutive system, demonstrating a high degree of regularity and universality in substitutive systems. I also discuss the origins and insights of the parameters in the substitution model and possible generalization form of the mathematical framework. The systematical study of substitutive systems presented in this dissertation could potentially guide the understanding and prediction of all spreading phenomena driven by substitutions, from electric cars to scientific paradigms, and from renewable energy to new healthy habits.