WorldWideScience

Sample records for nitrile oxide cycloadditions

  1. Isoxazolodihydropyridinones: 1,3-dipolar cycloaddition of nitrile oxides onto 2,4-dioxopiperidines

    Science.gov (United States)

    Coffman, Keith C.; Hartley, Timothy P.; Dallas, Jerry L.; Kurth, Mark J.

    2012-01-01

    Practical and efficient methods have been developed for the diversity-oriented synthesis of isoxazolodihydropyridinones via the 1,3-dipolar cycloaddition of nitrile oxides onto 2,4-dioxopiperidines. A select few of these isoxazolodihydropyridinones were further elaborated with triazoles by copper catalyzed azide-alkyne cycloaddition reactions. A total of 70 compounds and intermediates were synthesized and analyzed for drug likeness. Sixty-four of these novel compounds were submitted to the NIH Molecular Libraries Small Molecule Repository for high-throughput biological screening. PMID:22352295

  2. NMR studies on 1,3-dipolar cycloaddition of nitrile oxides to norbornenes

    Energy Technology Data Exchange (ETDEWEB)

    Gucma, Miroslaw; Golebiewski, W. Marek; Krawczyk, Maria, E-mail: golebiewski@ipo.waw.pl [Institute of Industrial Organic Chemistry, Warsaw (Poland)

    2013-05-15

    The 1,3-dipolar cycloaddition reaction of nitrile oxides to norbornenes substituted with an acrylate-derived moiety was examined. Only adducts to norbornene system were formed with a good exo selectivity and complete site-selectivity. Structures of the products were elucidated by an extensive application of electrospray ionization-mass spectrometry (ESI-MS) and 2D {sup 1}H and {sup 13}C nuclear magnetic resonance (NMR). (author)

  3. Ruthenium-catalyzed cycloadditions of 1-haloalkynes with nitrile oxides and organic azides: synthesis of 4-haloisoxazoles and 5-halotriazoles.

    Science.gov (United States)

    Oakdale, James S; Sit, Rakesh K; Fokin, Valery V

    2014-08-25

    (Cyclopentadienyl)(cyclooctadiene) ruthenium(II) chloride [CpRuCl(cod)] catalyzes the reaction between nitrile oxides and electronically deficient 1-choro-, 1-bromo-, and 1-iodoalkynes leading to 4-haloisoxazoles. Organic azides are also suitable 1,3-dipoles, resulting in 5-halo-1,2,3-triazoles. These air-tolerant reactions can be performed at room temperature with 1.25 equivalents of the respective 1,3-dipole relative to the alkyne component. Reactive 1-haloalkynes include propiolic amides, esters, ketones, and phosphonates. Post-functionalization of the halogenated azole products can be accomplished by using palladium-catalyzed cross-coupling reactions and by manipulation of reactive amide groups. The lack of catalysis observed with [Cp*RuCl(cod)] (Cp* = pentamethylcyclopentadienyl) is attributed to steric demands of the Cp* (η(5)-C5Me5) ligand in comparison to the parent Cp (η(5)-C5H5). This hypothesis is supported by the poor reactivity of [(η(5)-C5Me4CF3)RuCl(cod)], which serves as a an isosteric mimic of Cp* and as an isoelectronic analogue of Cp. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Regio- and stereoselective synthesis of pregnane-fused isoxazolines by nitril-oxide/alkene 1,3-dipolar cycloaddition and an evaluation of their cell-growth inhibitory effect in vitro

    Science.gov (United States)

    Mótyán, Gergő; Baji, Ádám; Zupkó, István; Frank, Éva

    2016-04-01

    Efficient syntheses of some pregnane-fused isoxazolines from 16-dehydropregnenolone acetate with different arylnitrile oxides were carried out by 1,3-dipolar cycloadditions. The intermolecular ring-closures occurred in a highly regio- and stereoselective manner permitting the formation of a single 16α,17α-condensed diastereomer in which the O terminus of the nitrile oxide dipole is attached to C-17 of the sterane core. The conversions were found to be affected significantly by the electronic character of the substituents on the aromatic moiety of the 1,3-dipoles. Deacetylation of the primary products resulted in the corresponding 3β-OH analogs. All of the synthesized compounds were subjected to in vitro pharmacological studies for the determination of their antiproliferative effects on four breast cancer cell lines (MCF7, T47D, MDA-MB-231 and MDA-MB-361).

  5. Ruthenium-Catalyzed Cycloaddition of 1-Haloalkynes with Nitrile Oxides and Organic Azides; Synthesis of 4-Halo Isoxazoles and 5-Halo Triazoles

    Science.gov (United States)

    Oakdale, James S.; Sit, Rakesh K.

    2015-01-01

    (Cyclopentadienyl)(cyclooctadiene) ruthenium(II) chloride [CpRuCl(cod)] catalyzes the reaction between nitrile oxides and electronically deficient 1-choro-, 1-bromo- and 1-iodoalkynes leading to 4-haloisoxazoles. Organic azides are also suitable 1,3-dipoles, resulting in 5-halo-1,2,3-triazoles. These air tolerant reactions can be performed at room temperature with 1.25 equiv of the respective 1,3-dipole relative to the alkyne component. Reactive 1-haloalkynes include propiolic amides, esters, ketones and phosphonates. Post-functionalization of the halogenated azole products can be accomplished using palladium-catalyzed cross-coupling reactions as well as via manipulation of reactive amide groups. The lack of catalysis observed with Cp*RuCl(cod) is attributed to steric demands of the Cp* (η5-C5Me5) ligand in comparison to the parent Cp (η5-C5H5). This hypothesis is supported by the poor reactivity of (η5-C5Me4CF3)RuCl(cod), which serves as a an isosteric mimic of Cp* and as an isoelectronic analog of Cp. PMID:25059647

  6. [3 + 2]-Cycloadditions of nitrile ylides after photoactivation of vinyl azides under flow conditions

    Directory of Open Access Journals (Sweden)

    Stephan Cludius-Brandt

    2013-08-01

    Full Text Available The photodenitrogenation of vinyl azides to 2H-azirines by using a photoflow reactor is reported and compared with thermal formation of 2H-azirines. Photochemically, the ring of the 2H-azirines was opened to yield the nitrile ylides, which underwent a [3 + 2]-cycloaddition with 1,3-dipolarophiles. When diisopropyl azodicarboxylate serves as the dipolarophile, 1,3,4-triazoles become directly accessible starting from the corresponding vinyl azide.

  7. Macromolecular surface design: photopatterning of functional stable nitrile oxides.

    Science.gov (United States)

    Altintas, Ozcan; Glassner, Mathias; Rodriguez-Emmenegger, Cesar; Welle, Alexander; Trouillet, Vanessa; Barner-Kowollik, Christopher

    2015-05-04

    The efficient trapping of photogenerated thioaldehydes with functional shelf-stable nitrile oxides in a 1,3-dipolar cycloaddition is a novel and versatile photochemical strategy for polymer end-group functionalization and surface modification under mild and equimolar conditions. The modular ligation in solution was followed in detail by electrospray ionization mass spectrometry (ESI-MS). X-ray photoelectron spectroscopy (XPS) was employed to analyze the functionalized surfaces, whereas time-of-flight secondary-ion mass spectrometry (ToF-SIMS) confirmed the spatial control of the surface functionalization using a micropatterned shadow mask. Polymer brushes were grown from the surface in a spatially confined regime by surface-initiated atom transfer radical polymerization (SI-ATRP) as confirmed by TOF-SIMS, XPS as well as ellipsometry. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Improved Synthesis of 5-Substituted 1H-Tetrazoles via the [3+2] Cycloaddition of Nitriles and Sodium Azide Catalyzed by Silica Sulfuric Acid

    Science.gov (United States)

    Du, Zhenting; Si, Changmei; Li, Youqiang; Wang, Yin; Lu, Jing

    2012-01-01

    A silica supported sulfuric acid catalyzed [3+2] cycloaddition of nitriles and sodium azide to form 5-substituted 1H-tetrazoles is described. The protocol can provide a series of 5-substituted 1H-tetrazoles using silica sulfuric acid from nitriles and sodium azide in DMF in 72%–95% yield. PMID:22606004

  9. 1,3-Dipolar cycloadditions of ethoxycarbonyl-nitrile benzylimine and synthesis of ß-amino acids. Synthesis and reactions of ethyl 2-chloro-2-ethoxyacetate and 2-chloro-2-ethoxyacetylchloride

    DEFF Research Database (Denmark)

    Bach, K.K.; El-Seedi, H.R.; Jensen, H.M.

    1994-01-01

    The principles of 1,2-cyano-hydroxylation of olefins were applied to the preparation of 1,2-cyano-amines. The dipole component of this cycloaddition was nitrile imines, which formed pyrazolines with olefins. Ring cleavage was accomplished by thermolysis of 3-carboxypyrazolines, which gave 1,2-cyano...

  10. Ruthenium-catalyzed aerobic oxidative decarboxylation of amino acids: a green, zero-waste route to biobased nitriles.

    Science.gov (United States)

    Claes, Laurens; Verduyckt, Jasper; Stassen, Ivo; Lagrain, Bert; De Vos, Dirk E

    2015-04-18

    Oxidative decarboxylation of amino acids into nitriles was performed using molecular oxygen as terminal oxidant and a heterogeneous ruthenium hydroxide-based catalyst. A range of amino acids was oxidized in very good yield, using water as the solvent.

  11. Exploring strain-promoted 1,3-dipolar cycloadditions of end functionalized polymers

    NARCIS (Netherlands)

    Ledin, Petr A; Kolishetti, Nagesh; Hudlikar, Manish S; Boons, Geert-Jan

    2014-01-01

    Strain-promoted 1,3-dipolar cycloaddition of cyclooctynes with 1,3-dipoles such as azides, nitrones, and nitrile oxides, are of interest for the functionalization of polymers. In this study, we have explored the use of a 4-dibenzocyclooctynol (DIBO)-containing chain transfer agent in reversible

  12. 1,3-Dipolar Cycloadditions of Benzonitrile Oxide with Various Dipolarophiles in Aqueous Solutions. A Kinetic Study

    NARCIS (Netherlands)

    Mersbergen, Dick van; Wijnen, Jan W.; Engberts, Jan B.F.N.

    1998-01-01

    The second-order rate constants for the 1,3-dipolar cycloaddition of benzonitrile oxide (1) with various dipolarophiles (2a-e) were determined in aqueous media and in organic solvents to gain more insight into the influence of an aqueous medium on pericyclic reactions. 1,3-Dipolar cycloadditions

  13. Kinetic solvent effects on 1,3-dipolar cycloadditions of benzonitrile oxide

    NARCIS (Netherlands)

    Rispens, T; Engberts, JBFN

    The kinetics of 1,3-dipolar cycloadditions of benzonitrile oxide with a series of N-substituted maleimides and with cyclopentene are reported for water, a wide range of organic solvents and binary solvent mixtures. The results indicate the importance of both solvent polarity and specific

  14. [3 + 2]-Cycloaddition of in Situ Generated Nitrile Imines and Acetylene for Assembling of 1,3-Disubstituted Pyrazoles with Quantitative Deuterium Labeling.

    Science.gov (United States)

    Voronin, Vladimir V; Ledovskaya, Maria S; Gordeev, Evgeniy G; Rodygin, Konstantin S; Ananikov, Valentine P

    2018-04-06

    A novel synthetic methodology for the preparation of 1,3-disubstituted pyrazoles from in situ generated nitrile imines and acetylene is reported. The reactions are performed in a simple two-chamber reactor. One part of the reactor is loaded with hydrazonoyl chloride precursors of active nitrile imine species and a base. The other part is used to generate acetylene from CaC 2 and water. Partitioning of the reactants improves the yields of desired pyrazoles up to 99% and simplifies their isolation to a simple procedure of solvent evaporation. The approach requires no complex equipment and utilizes inexpensive, safe, and easy to handle calcium carbide as a starting material. A model deuterium incorporation is carried out according to the developed methodology, producing a series of novel 4,5-dideuteropyrazoles with excellent deuterium enrichment. Theoretical calculations on reaction mechanism and characterization of possible intermediate structures were performed.

  15. Biomimetic Syntheses of Callistrilones A-E via an Oxidative [3 + 2] Cycloaddition.

    Science.gov (United States)

    Guo, Yonghong; Zhang, Yuhan; Xiao, Mingxing; Xie, Zhixiang

    2018-04-16

    Concise total syntheses of callistrilones A-E have been achieved from 7 and commercially available α-phellandrene (8). The synthetic strategy, which was primarily inspired by the biogenetic hypothesis, was enabled by an oxidative [3 + 2] cycloaddition followed by a Michael addition and an intramolecular nucleophilic addition to construct the target molecules. Moreover, viminalin I was also synthesized, and its absolute configuration was unambiguously confirmed.

  16. Light-induced oxidation of iron atoms in a photosensitive nitrile hydratase

    International Nuclear Information System (INIS)

    Honda, Jun; Sasabe, Hiroyuki; Teratani, Yoshitaka; Hirata, Akira; Kobayashi, Yoshio; Ambe, Fumitoshi; Nagamune, Teruyuki; Endo, Isao

    1992-01-01

    The photoactivation process of a photosensitive nitrile hydratase (NHase) from Rhodococcus sp. N-771 has been investigated by 57 Fe Moessbauer spectroscopy and magnetic susceptibility measurements in order to clarify the behavior of iron atoms in the enzyme. Moessbauer spectra of inactive NHase gave two symmetric-doublet components indicating the presence of two iron species, while that of the active NHase gave a single symmetric doublet indicating the presence of a single iron species. Magnetic susceptibility measurements of the inactive and active NHase both showed small effective magnetic moments. These results led to the conclusion that one of the two iron atoms incorporated in the NHase is oxidized during photoactivation, namely from a low spin ferrous to a low spin ferric state. This is the first observation of an intramolecular photooxidation phenomena involving iron in a single protein molecule. (author). 11 refs.; 3 figs.; 3 tabs

  17. Myeloperoxidase-mediated protein lysine oxidation generates 2-aminoadipic acid and lysine nitrile in vivo.

    Science.gov (United States)

    Lin, Hongqiao; Levison, Bruce S; Buffa, Jennifer A; Huang, Ying; Fu, Xiaoming; Wang, Zeneng; Gogonea, Valentin; DiDonato, Joseph A; Hazen, Stanley L

    2017-03-01

    Recent studies reveal 2-aminoadipic acid (2-AAA) is both elevated in subjects at risk for diabetes and mechanistically linked to glucose homeostasis. Prior studies also suggest enrichment of protein-bound 2-AAA as an oxidative post-translational modification of lysyl residues in tissues associated with degenerative diseases of aging. While in vitro studies suggest redox active transition metals or myeloperoxidase (MPO) generated hypochlorous acid (HOCl) may produce protein-bound 2-AAA, the mechanism(s) responsible for generation of 2-AAA during inflammatory diseases are unknown. In initial studies we observed that traditional acid- or base-catalyzed protein hydrolysis methods previously employed to measure tissue 2-AAA can artificially generate protein-bound 2-AAA from an alternative potential lysine oxidative product, lysine nitrile (LysCN). Using a validated protease-based digestion method coupled with stable isotope dilution LC/MS/MS, we now report protein bound 2-AAA and LysCN are both formed by hypochlorous acid (HOCl) and the MPO/H 2 O 2 /Cl - system of leukocytes. At low molar ratio of oxidant to target protein N ε -lysine moiety, 2-AAA is formed via an initial N ε -monochloramine intermediate, which ultimately produces the more stable 2-AAA end-product via sequential generation of transient imine and semialdehyde intermediates. At higher oxidant to target protein N ε -lysine amine ratios, protein-bound LysCN is formed via initial generation of a lysine N ε -dichloramine intermediate. In studies employing MPO knockout mice and an acute inflammation model, we show that both free and protein-bound 2-AAA, and in lower yield, protein-bound LysCN, are formed by MPO in vivo during inflammation. Finally, both 2-AAA and to lesser extent LysCN are shown to be enriched in human aortic atherosclerotic plaque, a tissue known to harbor multiple MPO-catalyzed protein oxidation products. Collectively, these results show that MPO-mediated oxidation of protein lysyl

  18. Oxidative removal of quinclorac by permanganate through a rate-limiting [3 + 2] cycloaddition reaction.

    Science.gov (United States)

    Song, Dean; Cheng, Hanyang; Jiang, Xiaohua; Sun, Huiqing; Kong, Fanyu; Liang, Rongning; Qiang, Zhimin; Liu, Huijuan; Qu, Jiuhui

    2018-04-05

    Quinclorac, a widely used herbicide in agriculture, has been recognized as an emerging environmental pollutant owing to its long persistence and potential risk to humans. However, no related information is available on the degradation of quinclorac by employing oxidants. Herein, the reactivity of quinclorac with permanganate was systematically investigated in water by combining experimental and computational approaches. The reaction followed overall second-order kinetics pointing to a bimolecular rate-limiting step. The second-order rate constant was found to be 3.47 × 10-3 M-1 s-1 at 25 °C, which was independent of pH over the range from 5 to 9 and was dependent on temperature over the range from 19 to 35 °C. The initial product was identified by UPLC-Q-TOF-MS to be mono-hydroxylated quinclorac, which was more susceptible to further oxidation. The result could be supported by the complete simulation of the reaction process in DFT calculations, indicating the [3 + 2] cycloaddition oxidation of the benzene ring in the rate-limiting step. The plausible mechanism was then proposed, accompanied by the analysis of the HOMO indicating the hydroxylation position and of the ESP suggesting a more electron-rich moiety. Considering the high effectiveness and low toxicity, permanganate oxidation was considered to be a very promising technique for removing quinclorac from aquatic environments.

  19. Nucleophile-directed selectivity towards linear carbonates in the niobium pentaethoxide-catalysed cycloaddition of CO2 and propylene oxide

    KAUST Repository

    Dutta, Barnali

    2014-01-01

    Homoleptic Nb-complexes combined with selected organic nucleophiles generate very active catalytic systems for the cycloaddition of propylene oxide and CO2 under ambient conditions. An unprecedented reaction pathway towards an acyclic organic carbonate is observed when extending the study to [Nb(OEt)5] in combination with 4-dimethylamino-pyridine (DMAP) or tetra-n-butylammonium bromide (TBAB). Mechanistic insights of the reaction are provided based on experimental and spectroscopic evidences. This journal is © the Partner Organisations 2014.

  20. cycloaddition reactions

    Indian Academy of Sciences (India)

    Unknown

    ... has shown very severe limitations in predicting the regioselectivity. In comparison,. DFT-based descriptors are better suited to model the regioselectivity of cycloaddition reactions. Acknowledgements. GG thanks the Council of Scientific and Industrial. Research for a fellowship. References. 1. Winkler J D 1996 Chem. Rev.

  1. Isoxazole derivatives as new nitric oxide elicitors in plants

    Directory of Open Access Journals (Sweden)

    Anca Oancea

    2017-04-01

    Full Text Available Several 3,5-disubstituted isoxazoles were obtained in good yields by regiospecific 1,3-dipolar cycloaddition reactions between aromatic nitrile oxides, generated in situ from the corresponding hydroxyimidoyl chlorides, with non-symmetrical activated alkynes in the presence of catalytic amounts of copper(I iodide. Effects of 3,5-disubstituted isoxazoles on nitric oxide and reactive oxygen species generation in Arabidopsis tissues was studied using specific diaminofluoresceine dyes as fluorescence indicators.

  2. Swift and efficient sono-hydrolysis of nitriles to carboxylic acids under basic condition: role of the oxide anion radical in the hydrolysis mechanism.

    Science.gov (United States)

    Lignier, Pascal; Estager, Julien; Kardos, Nathalie; Gravouil, Lydie; Gazza, Julien; Naffrechoux, Emmanuel; Draye, Micheline

    2011-01-01

    Carboxylic acids are promising candidates for new sustainable strategies in organic synthesis. In this paper, we ascertain the potential of ultrasound for the hydrolysis of nitriles into carboxylic acids through the study of key parameters of the reaction: pH, hydrolysis medium, reaction time and activation technique. The positive influence of ultrasound under basic conditions is due to more than mechanical effects of cavitation. Indeed, the rate of hydrolysis is dramatically increased under sonication in NaOH solutions. A radical mechanism involving the oxide anion radical O(*-) is proposed. Copyright © 2010 Elsevier B.V. All rights reserved.

  3. Undergraduate Organic Experiment: Tetrazole Formation by Microwave Heated (3 + 2) Cycloaddition in Aqueous Solution

    Science.gov (United States)

    DeFrancesco, Heather; Dudley, Joshua; Coca, Adiel

    2018-01-01

    An undergraduate experiment for the organic laboratory is described that utilizes microwave heating to prepare 5- substituted 1H-tetrazole derivatives through a (3 + 2) cycloaddition between aryl nitriles and sodium azide. The reaction mixture is analyzed by thin layer chromatography. The products are purified through an acid-base extraction and…

  4. Niobium(v) chloride and imidazolium bromides as efficient dual catalyst systems for the cycloaddition of carbon dioxide and propylene oxide

    KAUST Repository

    Wilhelm, Michael E.

    2014-02-19

    The application of niobium(v) chloride and several imidazolium bromides as catalyst systems for the cycloaddition of propylene oxide (PO) with carbon dioxide to propylene carbonate (PC) is reported. A set of 31 different imidazolium bromides has been synthesized with varying substituents at all five imidazolium ring atoms, of which 17 have not been reported before. The impact of different substitution patterns (steric and electronic changes and solubility in PO) at the imidazolium ring on the catalytic activity was investigated. The optimisation of the catalyst structure allows for the valorisation of carbon dioxide under mild reaction conditions with high reaction rates in very good yield and selectivity for PC. This journal is © the Partner Organisations 2014.

  5. Conversion of actual flue gas CO 2 via cycloaddition to propylene oxide catalyzed by a single-site, recyclable zirconium catalyst

    KAUST Repository

    Kelly, Michael J.

    2017-06-12

    A reusable zirconium-based catalyst for the cycloaddition of CO2 to propylene oxide (PO) was prepared by the surface organometallic chemistry (SOMC) methodology. Accordingly, well-defined amounts of the ZrCl4·(OEt2)2 precursor were grafted on the surface of silica dehydroxylated at 700°C (SiO2-700) and at 200°C (SiO2-200) in order to afford surface coordination compounds with different podality and chemical environment. The identity of the surface complexes was thoroughly investigated by FT-IR, elemental microanalysis and solid state NMR and applied as a recoverable and reusable heterogeneous catalyst for the title reaction using pure CO2 and flue gas samples from a cement factory. The observed catalytic activity for the isolated zirconium complexes is rationalized by means of systematic DFT calculations.

  6. A Straightforward Route to Enantiopure Pyrrolizidines and Indolizidines by Cycloaddition to Pyrroline N-Oxides Derived from the Chiral Pool

    Directory of Open Access Journals (Sweden)

    Alberto Brandi

    1998-12-01

    Full Text Available Enantiomerically pure, five membered cyclic nitrones, easily obtained in large amounts from protected hydroxyacids and aminoacids such as D- and L-tartaric, L-malic, and L-aspartic acids, give cycloaddition reactions with a good diastereocontrol. The adducts of L-malic and L-aspartic acids derived from addition of nitrones to dimethyl maleate and g-crotonolactone were easily converted into enantiopure pyrrolizidinones, which can be transformed into polyhydroxypyrrolidines or polyhydroxypyrrolizidines, both interesting compounds as potential glycosidase inhibitors. The method is suitable for natural products synthesis as exemplified by a straightforward and convenient access to the pyrrolizidine alkaloid necine base (–-hastanecine, as well as to indolizidine alkaloids, i.e. (+- lentiginosine.

  7. Nitrile biotransformation by Aspergillus niger

    Czech Academy of Sciences Publication Activity Database

    Šnajdrová, Radka; Kristová, Veronika; Crestia, D.; Nikolaou, K.; Kuzma, Marek; Lemaire, M.; Gallienne, E.; Bolte, J.; Bezouška, K.; Křen, Vladimír; Martínková, Ludmila

    2004-01-01

    Roč. 29, - (2004), s. 227-232 ISSN 1381-1177 R&D Projects: GA MŠk OC D25.002; GA AV ČR IAA4020213 Institutional research plan: CEZ:AV0Z5020903 Keywords : aspergillus niger * nitrile-converting enzymes * nitrile hydratase Subject RIV: EE - Microbiology, Virology Impact factor: 1.547, year: 2004

  8. Aerobic Oxidative Cycloaddition of α-Chlorotosylhydrazones with Arylamines: General Chemoselective Construction of 1,4-Disubstituted and 1,5-Disubstituted 1,2,3-Triazoles under Metal-Free and Azide-Free Conditions.

    Science.gov (United States)

    Bai, Hui-Wen; Cai, Zhong-Jian; Wang, Shun-Yi; Ji, Shun-Jun

    2015-06-19

    A novel synthetic approach toward 1,4-disubstituted 1,2,3-triazoles and 1,5-disubstituted 1,2,3-triazoles by aerobic oxidative cycloaddition of α-chlorotosylhydrazone with primary aryl amine has been developed. Significantly, the reaction proceeds smoothly to afford 1,4-disubstituted 1,2,3-triazoles and 1,5-disubstituted 1,2,3-triazoles under catalyst-free, metal-free, azide-free, and peroxide-free conditions.

  9. Ruthenium on chitosan: A recyclable heterogeneous catalyst for aqueous hydration of nitriles to amides

    Science.gov (United States)

    Ruthenium has been immobilized over chitosan by simply stirring an aqueous suspension of chitosan in water with ruthenium chloride and has been utilized for the oxidation of nitriles to amides; the hydration of nitriles occurs in high yield and excellent selectivity, which procee...

  10. Platinum-Catalyzed Selective Hydration of Hindered Nitriles and Nitriles with Acid- or Base-Sensitive Groups

    NARCIS (Netherlands)

    Jiang, Xiao-bin; Minnaard, Adriaan J.; Vries, Johannes G. de; Feringa, Bernard

    2004-01-01

    Hindered tertiary nitriles can be hydrolyzed under neutral and mild conditions to the corresponding amides using platinum(II) catalysts with dimethylphosphine oxide or other secondary phosphine oxides (SPOs, phosphinous acids) as ligands. We have found that this procedure also works well for

  11. A molecular electron density theory study of the chemo- and regioselective [3 + 2] cycloaddition reactions between trifluoroacetonitrile N-oxide and thioketones

    Science.gov (United States)

    Emamian, Saeedreza; Lu, Tian; Domingo, Luis. R.; Heidarpoor Saremi, Leily; Ríos-Gutiérrez, Mar

    2018-02-01

    The [3 + 2] cycloaddition (32CA) reaction between trifluoroacetonitrile N-oxide (NO 7) and 2,2,4,4-tetramethyl-3-thioxocyclobutan-1-one (THK 12) as well as the self-dimerization of NO 7 as a competitive pathway were studied within the Molecular Electron Density Theory (MEDT) using several DFT functionals together with def2-TZVP basis set. Taking CCSD(T)/TZVP activation energies as reference, among the employed functionals, just the B2PLYP-D3(BJ) one is able to portray complete predominance of 32CA reaction over self-dimerization process in excellent agreement with the experimental outcomes. Analysis of the global reactivity indices permits to characterize NO 7 and THK 12 as a strong electrophile and a strong nucleophile, respectively, while analysis of the Parr functions allows explaining the chemo- and regioselectivity observed experimentally. The electron localization function (ELF) analysis of several points along the IRC profile associated with the energetically most favorable reaction channel permits to establish a non-concerted two-stage one-step molecular mechanism for this polar pmr-type 32CA reaction.

  12. Cycloaddition Reactions of Deoxyribosylpropynoates

    Czech Academy of Sciences Publication Activity Database

    Hessler, F.; Kulhavá, L.; Císařová, I.; Otmar, Miroslav; Kotora, Martin

    2014-01-01

    Roč. 44, č. 9 (2014), s. 1232-1239 ISSN 0039-7911 Grant - others:AV ČR(CZ) IAA401110805 Institutional support: RVO:61388963 Keywords : Dewar benzenes * C-aryldeoxyribosides * unnatural nucleosides * cyclotrimerization * cycloaddition Subject RIV: CC - Organic Chemistry Impact factor: 0.929, year: 2014

  13. Asymmetric Organocatalytic Cycloadditions

    DEFF Research Database (Denmark)

    Mose, Rasmus

    2016-01-01

    has gained broad recognition as it has found several applications in academia and industry. The [4+2] cycloaddition has also been performed in an enantioselective aminocatalytic fashion which allows the generation of optically active products. In this thesis it is demonstrated how trienamines can...

  14. Investigation of surface halide modification of nitrile butadiene rubber

    Science.gov (United States)

    Sukhareva, K. V.; Mikhailov, I. A.; Andriasyan, Yu O.; Mastalygina, E. E.; Popov, A. A.

    2017-12-01

    The investigation is devoted to the novel technology of surface halide modification of rubber samples based on nitrile butadiene rubber (NBR). 1,1,2-trifluoro-1,2,2-trichlorethane was used as halide modifier. The developed technology is characterized by production stages reduction to one by means of treating the rubber compound with a halide modifier. The surface halide modification of compounds based on nitrile butadiene rubber (NBR) was determined to result in increase of resistance to thermal oxidation and aggressive media. The conducted research revealed the influence of modification time on chemical resistance and physical-mechanical properties of rubbers under investigation.

  15. (4+2)-cycloaddition of nitroalkenes with ynamines; formation of a 4H-1,2-oxazine 2-oxide derivative

    NARCIS (Netherlands)

    Pennings, M.L.M.; Reinhoudt, David

    1980-01-01

    The formation of a thermally unstable (4+2)-cycloadduct, a 4H-1,2-oxazine 2-oxide derivative ( ), from the reaction of 1-nitrocyclopentene with 1-phenyl-2-(1-pyrrolidinyl)acetylene has been proven by the structure elucidation of isoxazole derivative which results from thermal rearrangement and by

  16. Cu-free 1,3-dipolar cycloaddition click reactions to form isoxazole linkers in chelating ligands for fac-[M(I)(CO)3]+ centers (M = Re, 99mTc).

    Science.gov (United States)

    Bottorff, Shalina C; Kasten, Benjamin B; Stojakovic, Jelena; Moore, Adam L; MacGillivray, Leonard R; Benny, Paul D

    2014-02-17

    Isoxazole ring formation was examined as a potential Cu-free alternative click reaction to Cu(I)-catalyzed alkyne/azide cycloaddition. The isoxazole reaction was explored at macroscopic and radiotracer concentrations with the fac-[M(I)(CO)3](+) (M = Re, (99m)Tc) core for use as a noncoordinating linker strategy between covalently linked molecules. Two click assembly methods (click, then chelate and chelate, then click) were examined to determine the feasibility of isoxazole ring formation with either alkyne-functionalized tridentate chelates or their respective fac-[M(I)(CO)3](+) complexes with a model nitrile oxide generator. Macroscale experiments, alkyne-functionalized chelates, or Re complexes indicate facile formation of the isoxazole ring. (99m)Tc experiments demonstrate efficient radiolabeling with click, then chelate; however, the chelate, then click approach led to faster product formation, but lower yields compared to the Re analogues.

  17. Alkylation and 1,3-Dipolar Cycloaddition of 6-Styryl-4,5-dihydro-2H-pyridazin-3-one: Synthesis of Novel N-Substituted Pyridazinones and Triazolo[4,3-b]pyridazinones

    Directory of Open Access Journals (Sweden)

    Souad Mojahidi

    2013-01-01

    Full Text Available Some new N-substituted pyridazinones and triazolo[4,3-b]pyridazinones were synthesized, respectively, by simple alkylation and 1,3-dipolar cycloaddition of pyridazin-3-one with nitrile imines. The regioselectivity of the reactions was ascertained by 1H, 13C NMR spectroscopy and X-ray diffraction of the synthesized compounds.

  18. Enantioselective biotransformations of nitriles in organic synthesis.

    Science.gov (United States)

    Wang, Mei-Xiang

    2015-03-17

    The hydration and hydrolysis of nitriles are valuable synthetic methods used to prepare carboxamides and carboxylic acids. However, chemical hydration and hydrolysis of nitriles involve harsh reaction conditions, have low selectivity, and generate large amounts of waste. Therefore, researchers have confined the scope of these reactions to simple nitrile substrates. However, biological transformations of nitriles are highly efficient, chemoselective, and environmentally benign, which has led synthetic organic chemists and biotechologists to study these reactions in detail over the last two decades. In nature, biological systems degrade nitriles via two distinct pathways: nitrilases catalyze the direct hydrolysis of nitriles to afford carboxylic acids with release of ammonia, and nitrile hydratases catalyze the conversion of nitriles into carboxamides, which then furnish carboxylic acids via hydrolysis in the presence of amidases. Researchers have subsequently developed biocatalytic methods into useful industrial processes for the manufacture of commodity chemicals, including acrylamide. Since the late 1990s, research by my group and others has led to enormous progress in the understanding and application of enantioselective biotransformations of nitriles in organic synthesis. In this Account, I summarize the important advances in enantioselective biotransformations of nitriles and amides, with a primary focus on research from my laboratory. I describe microbial whole-cell-catalyzed kinetic resolution of various functionalized nitriles, amino- and hydroxynitriles, and nitriles that contain small rings and the desymmetrization of prochiral and meso dinitriles and diamides. I also demonstrate how we can apply the biocatalytic protocol to synthesize natural products and bioactive compounds. These nitrile biotransformations offer an attractive and unique protocol for the enantioselective synthesis of polyfunctionalized organic compounds that are not readily obtainable by

  19. Nitrile Metabolizing Enzymes in Biocatalysis and Biotransformation.

    Science.gov (United States)

    Bhalla, Tek Chand; Kumar, Vijay; Kumar, Virender; Thakur, Neerja; Savitri

    2018-01-30

    Nitrile metabolizing enzymes, i.e., aldoxime dehydratase, hydroxynitrile lyase, nitrilase, nitrile hydratase, and amidase, are the key catalysts in carbon nitrogen triple bond anabolism and catabolism. Over the past several years, these enzymes have drawn considerable attention as prominent biocatalysts in academia and industries because of their wide applications. Research on various aspects of these biocatalysts, i.e., sources, screening, function, purification, molecular cloning, structure, and mechanisms, has been conducted, and bioprocesses at various scales have been designed for the synthesis of myriads of useful compounds. This review is focused on the potential of nitrile metabolizing enzymes in the production of commercially important fine chemicals such as nitriles, carboxylic acids, and amides. A number of opportunities and challenges of nitrile metabolizing enzymes in bioprocess development for the production of bulk and fine chemicals are discussed.

  20. Wavelength Dependence of Light-Induced Cycloadditions.

    Science.gov (United States)

    Menzel, Jan P; Noble, Benjamin B; Lauer, Andrea; Coote, Michelle L; Blinco, James P; Barner-Kowollik, Christopher

    2017-11-08

    The wavelength-dependent conversion of two rapid photoinduced ligation reactions, i.e., the light activation of o-methylbenzaldehydes, leading to the formation of reactive o-quinodimethanes (photoenols), and the photolysis of 2,5-diphenyltetrazoles, affording highly reactive nitrile imines, is probed via a monochromatic wavelength scan at constant photon count. The transient species are trapped by cycloaddition with N-ethylmaleimide, and the reactions are traced by high resolution mass spectrometry and nuclear magnetic resonance spectroscopy. The resulting action plots are assessed in the context of Beer-Lambert's law and provide combined with time-dependent density functional theory and multireference calculations an in-depth understanding of the underpinning mechanistic processes, including conical intersections. The π → π* transition of the carbonyl group of the o-methylbenzaldehyde correlates with a highly efficient conversion to the cycloadduct, showing no significant wavelength dependence, while conversion following the n → π* transition proceeds markedly less efficient at longer wavelengths. The influence of absorbance and reactivity has critical consequences for an effective reaction design: At high concentrations of o-methylbenzaldehydes (c = 8 mmol L -1 ), photoligations with N-ethylmaleimide (possible for λ ≤ 390 nm) are ideally performed at 330 nm, whereas at high light penetration regimes at lower concentrations (c = 0.3 mmol L -1 ), 315 nm irradiation leads to the highest conversion. Activation and trapping of 2,5-diphenyltetrazoles (possible for λ ≤ 322 nm) proceeds best at a wavelength shorter than 295 nm, irrespective of concentration.

  1. Nitrile Polymerisation and Heterocyclic Synthesis Using Iminyls.

    Science.gov (United States)

    1977-03-31

    methoxyamine in acidic ethanol solution the corresponding ethyl acecal was formed. In an alternative approach to the keto—nitrile (7; X—CN) the lactone (9) was... unsaturated nitrile. In this way the keto—nitrile (15) was ~~~ (i5~) (“) (1 7) LI produced but only in Low yield .7 The main products, the 2:1 adduc ts...2H , s , Cl!2), 7.23—7.68 (50, is , ArH); (b) the lactone of ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ --- —— - .5---- -- . . 5 - — - - . -~~~~ -- --.5

  2. Thermodynamic and kinetic study of cleavage of the N-O bond of N-oxides by a vanadium(III) complex: enhanced oxygen atom transfer reaction rates for adducts of nitrous oxide and mesityl nitrile oxide.

    Science.gov (United States)

    Palluccio, Taryn D; Rybak-Akimova, Elena V; Majumdar, Subhojit; Cai, Xiaochen; Chui, Megan; Temprado, Manuel; Silvia, Jared S; Cozzolino, Anthony F; Tofan, Daniel; Velian, Alexandra; Cummins, Christopher C; Captain, Burjor; Hoff, Carl D

    2013-07-31

    Thermodynamic, kinetic, and computational studies are reported for oxygen atom transfer (OAT) to the complex V(N[t-Bu]Ar)3 (Ar = 3,5-C6H3Me2, 1) from compounds containing N-O bonds with a range of BDEs spanning nearly 100 kcal mol(-1): PhNO (108) > SIPr/MesCNO (75) > PyO (63) > IPr/N2O (62) > MesCNO (53) > N2O (40) > dbabhNO (10) (Mes = mesityl; SIPr = 1,3-bis(diisopropyl)phenylimidazolin-2-ylidene; Py = pyridine; IPr = 1,3-bis(diisopropyl)phenylimidazol-2-ylidene; dbabh = 2,3:5,6-dibenzo-7-azabicyclo[2.2.1]hepta-2,5-diene). Stopped flow kinetic studies of the OAT reactions show a range of kinetic behavior influenced by both the mode and strength of coordination of the O donor and its ease of atom transfer. Four categories of kinetic behavior are observed depending upon the magnitudes of the rate constants involved: (I) dinuclear OAT following an overall third order rate law (N2O); (II) formation of stable oxidant-bound complexes followed by OAT in a separate step (PyO and PhNO); (III) transient formation and decay of metastable oxidant-bound intermediates on the same time scale as OAT (SIPr/MesCNO and IPr/N2O); (IV) steady-state kinetics in which no detectable intermediates are observed (dbabhNO and MesCNO). Thermochemical studies of OAT to 1 show that the V-O bond in O≡V(N[t-Bu]Ar)3 is strong (BDE = 154 ± 3 kcal mol(-1)) compared with all the N-O bonds cleaved. In contrast, measurement of the N-O bond in dbabhNO show it to be especially weak (BDE = 10 ± 3 kcal mol(-1)) and that dissociation of dbabhNO to anthracene, N2, and a (3)O atom is thermodynamically favorable at room temperature. Comparison of the OAT of adducts of N2O and MesCNO to the bulky complex 1 show a faster rate than in the case of free N2O or MesCNO despite increased steric hindrance of the adducts.

  3. Regio and stereoselectivity in ionic cycloadditions

    Indian Academy of Sciences (India)

    WINTEC

    Though the reactions have both electrostatic control and frontier orbital control the former dominates in the initial stages of the reaction. Keywords. Stereoselectivity; ionic cycloaddition; density functional theory; acridizinium ion; methyl vinyl ether; 2,3-dimethylisoquinolinium ion. 1. Introduction. In polar or ionic cycloadditions ...

  4. Dynamics of the NbCl5-catalyzed cycloaddition of propylene oxide and CO2: Assessing the dual role of the nucleophilic co-catalysts

    KAUST Repository

    D'Elia, Valerio

    2014-07-23

    A mechanistic study on the synthesis of propylene carbonate (PC) from CO2 and propylene oxide (PO) catalyzed by NbCl5 and organic nucleophiles such as 4-dimethylaminopyridine (DMAP) or tetra-n-butylammonium bromide (NBu4Br) is reported. A combination of in situ spectroscopic techniques and kinetic studies has been used to provide detailed insight into the reaction mechanism, the formation of intermediates, and interactions between the reaction partners. The results of DFT calculations support the experimental observations and allow us to propose a mechanism for this reaction. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. A kinetic study of 1,3-dipolar cycloadditions in micellar media

    NARCIS (Netherlands)

    Rispens, T; Engberts, JBFN

    2003-01-01

    The kinetics of the 1,3-dipolar cycloadditions (DC) of benzonitrile oxide with a series of N-substituted maleimides in micellar media have been investigated. Surfactants studied include anionic sodium dodecyl sulfate, cationic cetyltrimethylammonium bromide, and a series of nonionic alkyl

  6. Biotransformation of nitriles to hydroxamic acids via a nitrile hydratase–amidase cascade reaction

    Czech Academy of Sciences Publication Activity Database

    Vejvoda, Vojtěch; Martínková, Ludmila; Veselá, Alicja Barbara; Kaplan, Ondřej; Lutz-Wahl, S.; Fischer, L.; Uhnáková, Bronislava

    2011-01-01

    Roč. 71, 1-2 (2011), s. 51-55 ISSN 1381-1177 R&D Projects: GA MŠk(CZ) LC06010; GA MŠk OC09046 Institutional research plan: CEZ:AV0Z50200510 Keywords : Nitrile hydratase * Rhodococcus erythropolis * Amidase Subject RIV: EE - Microbiology, Virology Impact factor: 2.735, year: 2011

  7. Manganese Catalyzed α-Olefination of Nitriles by Primary Alcohols.

    Science.gov (United States)

    Chakraborty, Subrata; Das, Uttam Kumar; Ben-David, Yehoshoa; Milstein, David

    2017-08-30

    Catalytic α-olefination of nitriles using primary alcohols, via dehydrogenative coupling of alcohols with nitriles, is presented. The reaction is catalyzed by a pincer complex of an earth-abundant metal (manganese), in the absence of any additives, base, or hydrogen acceptor, liberating dihydrogen and water as the only byproducts.

  8. The Application of Nitrile Hydratases in Organic Synthesis

    NARCIS (Netherlands)

    Van Pelt, S.

    2010-01-01

    Nitrile hydratases (NHases, E.C. 4.2.1.84) catalyse the transformation of nitriles into the corresponding amides and were first discovered 30 years ago in studies on the microbial degradation of toxic cyano-group-containing compounds. The use of NHases in synthetic chemistry is especially

  9. Formation and nitrile hydrogenation performance of Ru nanoparticles on a K-doped Al2O3 surface.

    Science.gov (United States)

    Muratsugu, Satoshi; Kityakarn, Sutasinee; Wang, Fei; Ishiguro, Nozomu; Kamachi, Takashi; Yoshizawa, Kazunari; Sekizawa, Oki; Uruga, Tomoya; Tada, Mizuki

    2015-10-14

    Decarbonylation-promoted Ru nanoparticle formation from Ru3(CO)12 on a basic K-doped Al2O3 surface was investigated by in situ FT-IR and in situ XAFS. Supported Ru3(CO)12 clusters on K-doped Al2O3 were converted stepwise to Ru nanoparticles, which catalyzed the selective hydrogenation of nitriles to the corresponding primary amines via initial decarbonylation, the nucleation of the Ru cluster core, and the growth of metallic Ru nanoparticles on the surface. As a result, small Ru nanoparticles, with an average diameter of less than 2 nm, were formed on the support and acted as efficient catalysts for nitrile hydrogenation at 343 K under hydrogen at atmospheric pressure. The structure and catalytic performance of Ru catalysts depended strongly on the type of oxide support, and the K-doped Al2O3 support acted as a good oxide for the selective nitrile hydrogenation without basic additives like ammonia. The activation of nitriles on the modelled Ru catalyst was also investigated by DFT calculations, and the adsorption structure of a nitrene-like intermediate, which was favourable for high primary amine selectivity, was the most stable structure on Ru compared with other intermediate structures.

  10. Biotransformation of nitriles to amides using soluble and immobilized nitrile hydratase from Rhodococcus erythropolis A4

    Czech Academy of Sciences Publication Activity Database

    Kubáč, David; Kaplan, Ondřej; Elišáková, Veronika; Pátek, Miroslav; Vejvoda, Vojtěch; Slámová, Kristýna; Tóthová, A.; Lemaire, M.; Gallienne, E.; Lutz-Wahl, S.; Fischer, L.; Kuzma, Marek; Pelantová, Helena; van Pelt, S.; Bolte, J.; Křen, Vladimír; Martínková, Ludmila

    2008-01-01

    Roč. 50, 2-4 (2008), s. 107-113 ISSN 1381-1177 R&D Projects: GA ČR GA203/05/2267; GA MŠk(CZ) LC06010; GA MŠk OC 171 Grant - others:XE(XE) ESF COST D25/0002/02; CZ(CZ) D10-CZ25/06-07; CZ(CZ) D-25 Institutional research plan: CEZ:AV0Z50200510 Keywords : rhodococcus erythropolis * nitrile hydratase * amidase Subject RIV: EE - Microbiology, Virology Impact factor: 2.015, year: 2008

  11. Preliminary Study on Effect of Chemical Composition Alteration on Elastic Recovery and Stress Recovery of Nitrile Gloves

    Directory of Open Access Journals (Sweden)

    Tan Kai Yang

    2018-01-01

    Full Text Available Nitrile gloves are widely used in the medical and automobile field due to its superiority in hypo-allergic component and chemical resistance over natural latex gloves. However, poor elastic recovery of nitrile glove to compressive force also creates an aesthetic issue for customers with high levels of wrinkling after removing from glove box. This paper demonstrates the preliminary study on the varies chemical composition such as crosslinking agents, sulphur and zinc oxide, the accelerator agent added during curing process, and the rubber filler Titanium Dioxide, on the elastic recovery and stress relaxation in nitrile gloves manufacturing. These chemical were studied at different concentration level comparing the high and low level versus the normal production range. Due to the inconsistency in the analysis technique on the surface imaging, the elastic recovery result was unable to be quantified and was not conclusive at this point. The cross linking agents, sulphur and zinc oxide, and the accelerator agent, played a significant role in the mechanical strength of the gloves. Increment of these chemicals result in higher tensile strength, but a reduction in the elasticity of the materials in which causes a lesser elongation at break percentage for the gloves. Both cross-linkers demonstrate different behaviour where higher sulphur content, provide higher stress relaxation (SR% yet zinc oxide shows otherwise.

  12. Nitrile functionalized halloysite nanotubes/poly(arylene ether nitrile) nanocomposites: Interface control, characterization, and improved properties

    Energy Technology Data Exchange (ETDEWEB)

    Wan, Xinyi [School of Chemistry and Chemical Engineering, Southwest Petroleum University, 8 Xindu Avenue, Chengdu, Sichuan, 610500 (China); Zhan, Yingqing, E-mail: 201599010032@swpu.edu.cn [School of Chemistry and Chemical Engineering, Southwest Petroleum University, 8 Xindu Avenue, Chengdu, Sichuan, 610500 (China); Oil & Gas Field Applied Chemistry Key Laboratory of Sichuan Province, Southwest Petroleum University, Chengdu, Sichuan, China, 610500 (China); Zeng, Guangyong [School of Chemistry and Chemical Engineering, Southwest Petroleum University, 8 Xindu Avenue, Chengdu, Sichuan, 610500 (China); He, Yi, E-mail: heyi007@163.com [School of Chemistry and Chemical Engineering, Southwest Petroleum University, 8 Xindu Avenue, Chengdu, Sichuan, 610500 (China); Oil & Gas Field Applied Chemistry Key Laboratory of Sichuan Province, Southwest Petroleum University, Chengdu, Sichuan, China, 610500 (China); State Key Lab of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, 8Xindu Avenue, Chengdu, Sichuan, 610500 (China)

    2017-01-30

    Highlights: • Novel nitrile functionalized HNTs were realized through the covalent bonding. • Then modified HNTs showed good dispersion and interfacial adhesion with PEN. • The modified HNTs exhibited excellent reinforcement effect on PEN. • The chemical crosslinking between HNTs and PEN further enhanced the performance of nanocomposites. - Abstract: To develop high-performance halloysite nanotube (HNT)-based nanocomposites, the two key issues need to be considered: precise interface control and the dispersal of HNTs. This study presents an efficient way to functionalize halloysite nanotubes with 3-aminophenoxy-phthalonitrile, followed by compounding with poly(arylene ether nitrile) (PEN), to prepare functional nanocomposite films. The surface functionalization of HNTs was characterized and confirmed by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). Compared with neat PEN, the tensile strength and modulus of the resulting PEN nanocomposites with 3 wt% functionalized HNTs were found to increase by 25.7% and 20.7%, respectively. The good dispersion and high capacitance of the dielectric layer resulted in PEN/HNTs nancomposites with enhanced dielectric permittivity and relatively low dielectric loss. Moreover, the addition of functional HNTs greatly improved the thermal stability of PEN, which could be further enhanced through the chemical cross-linking reaction between the functional HNTs and the PEN matrix. This work provides a new path toward obtaining advanced polymer-based nanocomposites with functional properties.

  13. Mechanism and regioselectivity of 1,3-dipolar cycloaddition ...

    Indian Academy of Sciences (India)

    The present analysis reveals that the cycloaddition reactions under study can be ... 1,3-Dipolar cycloaddition; sulphur-centred 1,3-dipoles; regioselectivity; DFT reactivity indices;. FMO theory. 1. Introduction. Five-membered heterocyclic compounds can be gene- rated by addition of a 1,3-dipole to a dipolarophile under.

  14. Spectrometric Study of the Nitrile-Ketenimine Tautomerism

    Directory of Open Access Journals (Sweden)

    Hebe Saraví Cisneros

    2009-01-01

    Full Text Available Mass spectrometry is used to evaluate the occurrence of the nitrile-ketenimine tautomerism. Mass spectra of two differently substituted nitriles, ethyl-4,4-dicyano-3-methyl-3-butenoate and diethyl-2-cyano-3-methyl-2-pentenodiate are examined looking for common mass spectral behaviors. Ion fragmentation assignments for specific tautomers allow to predict the presence of the corresponding structures. Additionally, the mass spectrum and nuclear magnetic resonance spectra of ethyl-4,4-dicyano-2,2-diethyl-3-methyl-3-butenoate and that of the corresponding amination product support the occurrence of the ketenimine tautomer in the equilibrium.

  15. Hydrolysis of nitriles by soil bacteria: variation with soil origin

    CSIR Research Space (South Africa)

    Rapheeha, OKL

    2017-03-01

    Full Text Available . To achieve this, we needed to compare the efficiency of isolation methods and determine the influence of land use and geographical origin of the soil sample. Nitrile-utilizing bacteria were isolated from various soil environments across a 1000 km long...

  16. The Reduction of Nitriles to Aldehydes: Applications of Raney Nickel ...

    African Journals Online (AJOL)

    NJD

    The three title reductant systems have significant advantages in generating aldehydes from nitriles. These include: the utilization of convenient hydrogen sources, namely, sodium hypophosphite monohydrate and formic acid, respectively, and of the relatively inexpensive Raney nickel and Raney (Ni/Al) alloy; the ...

  17. Straightforward uranium-catalyzed dehydration of primary amides to nitriles

    International Nuclear Information System (INIS)

    Enthaler, Stephan

    2011-01-01

    The efficient uranium-catalyzed dehydration of a variety of primary amides, using N-methyl-N-(trimethylsilyl)trifluoroacetamide (MSTFA) as a dehydration reagent, to the corresponding nitriles has been investigated. With this catalyst system, extraordinary catalyst activities and selectivities were feasible. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  18. Sulfonated poly(fluorenyl ether ketone nitrile) electrolyte membrane with high proton conductivity and low water uptake

    Energy Technology Data Exchange (ETDEWEB)

    Tian, S.H.; Wang, S.J.; Xiao, M.; Meng, Y.Z. [State Key Laboratory of Optoelectronic Materials and Technologies/Institute of Optoelectronic and Functional Composite Materials, Sun Yat-sen University, Guangzhou 510275 (China); Shu, D. [School of Chemistry and Environmental, South China Normal University, Guangzhou 510006 (China)

    2010-01-01

    High molecular weight sulfonated poly(fluorenyl ether ketone nitrile)s with different equivalent weight (EW) from 681 to 369 g mequiv.{sup -1} are synthesized by the nucleophilic substitution polycondensation of various amounts of sulfonated difluorobenzophenone (SDFBP) and 2,6-difluorobenzonitrile (DFBN) with bisphenol fluorene (BPF). The synthesized copolymers are characterized by {sup 1}H NMR, FT-IR, TGA, and DSC techniques. The membranes cast from the corresponding copolymers exhibit superior thermal stability, good oxidative stability and high proton conductivity, but low water uptake due to the strong nitrile dipole interchain interactions that combine to limit swelling. Among all the membranes, the membrane with EW of 441 g mequiv.{sup -1} shows optimum properties of both high proton conductivity of 41.9 mS cm{sup -1} and low water uptake of 42.6%. Accordingly, That membrane is fabricated into a membrane electrode assembly (MEA) and evaluated in a single proton exchange membrane fuel cell (PEMFC). The experimental results indicate its similar cell performance as that of Nafion {sup registered} 117 at 70 C, but much better cell performance at higher temperatures. At the potential of 0.6 V, the current density of fuel cell using the prepared membrane and Nafion {sup registered} 117 is 0.46 and 0.25 A cm{sup -2}, respectively. The highest current density of the former reaches as high as 1.25 A cm{sup -2}. (author)

  19. Bio-Inspired Nitrile Hydration by Peptidic Ligands Based on L-Cysteine, L-Methionine or L-Penicillamine and Pyridine-2,6-dicarboxylic Acid

    Directory of Open Access Journals (Sweden)

    Cillian Byrne

    2014-12-01

    Full Text Available Nitrile hydratase (NHase, EC 4.2.1.84 is a metalloenzyme which catalyses the conversion of nitriles to amides. The high efficiency and broad substrate range of NHase have led to the successful application of this enzyme as a biocatalyst in the industrial syntheses of acrylamide and nicotinamide and in the bioremediation of nitrile waste. Crystal structures of both cobalt(III- and iron(III-dependent NHases reveal an unusual metal binding motif made up from six sequential amino acids and comprising two amide nitrogens from the peptide backbone and three cysteine-derived sulfur ligands, each at a different oxidation state (thiolate, sulfenate and sulfinate. Based on the active site geometry revealed by these crystal structures, we have designed a series of small-molecule ligands which integrate essential features of the NHase metal binding motif into a readily accessible peptide environment. We report the synthesis of ligands based on a pyridine-2,6-dicarboxylic acid scaffold and L-cysteine, L-S-methylcysteine, L-methionine or L-penicillamine. These ligands have been combined with cobalt(III and iron(III and tested as catalysts for biomimetic nitrile hydration. The highest levels of activity are observed with the L-penicillamine ligand which, in combination with cobalt(III, converts acetonitrile to acetamide at 1.25 turnovers and benzonitrile to benzamide at 1.20 turnovers.

  20. Macromolecular surface design: photopatterning of functional stable nitrile oxides

    Czech Academy of Sciences Publication Activity Database

    Altintas, O.; Glassner, M.; Rodriguez-Emmenegger, Cesar; Welle, A.; Trouillet, V.; Barner-Kowollik, C.

    2015-01-01

    Roč. 54, č. 19 (2015), s. 5777-5783 ISSN 1433-7851 R&D Projects: GA ČR(CZ) GBP205/12/G118 Institutional support: RVO:61389013 Keywords : modular ligation * nitrogen heterocycles * polymerization Subject RIV: BO - Biophysics Impact factor: 11.709, year: 2015

  1. Switchable regioselectivity in amine-catalysed asymmetric cycloadditions

    Science.gov (United States)

    Zhou, Zhi; Wang, Zhou-Xiang; Zhou, Yuan-Chun; Xiao, Wei; Ouyang, Qin; Du, Wei; Chen, Ying-Chun

    2017-06-01

    Building small-molecule libraries with structural and stereogenic diversity plays an important role in drug discovery. The development of switchable intermolecular cycloaddition reactions from identical substrates in different regioselective fashions would provide an attractive protocol. However, this also represents a challenge in organic chemistry, because it is difficult to control regioselectivity to afford the products exclusively and at the same time achieve high levels of stereoselectivity. Here, we report the diversified cycloadditions of α‧-alkylidene-2-cyclopentenones catalysed by cinchona-derived primary amines. An asymmetric γ,β‧-regioselective intermolecular [6+2] cycloaddition reaction with 3-olefinic (7-aza)oxindoles is realized through the in situ generation of formal 4-aminofulvenes, while a different β,γ-regioselective [2+2] cycloaddition reaction with maleimides to access fused cyclobutanes is disclosed. In contrast, an intriguing α,γ-regioselective [4+2] cycloaddition reaction is uncovered with the same set of substrates, by employing an unprecedented dual small-molecule catalysis of amines and thiols. All of the cycloaddition reactions exhibit excellent regio- and stereoselectivity, producing a broad spectrum of chiral architectures with high structural diversity and molecular complexity.

  2. Catalytic Synthesis of Nitriles in Continuous Flow

    DEFF Research Database (Denmark)

    Nordvang, Emily Catherine

    , alternative path to acetonitrile from ethanol via the oxidative dehydrogenation of ethylamine. The catalytic activity and product ratios of the batch and continuous flow reactions are compared and the effect of reaction conditions on the reaction is investigated. The effects of ammonia in the reaction...... dehydrogenation of ethylamine and post-reaction purging.Chapter 4 outlines the application of RuO2/Al2O3 catalysts to the oxidative dehydrogenation of benzylamine in air, utilizing a new reaction setup. Again, batch and continuous flow reactions are compared and the effects of reaction conditions, ammonia...

  3. Permeation of aromatic solvent mixtures through nitrile protective gloves.

    Science.gov (United States)

    Chao, Keh-Ping; Hsu, Ya-Ping; Chen, Su-Yi

    2008-05-30

    The permeation of binary and ternary mixtures of benzene, toluene, ethyl benzene and p-xylene through nitrile gloves were investigated using the ASTM F739 test cell. The more slowly permeating component of a mixture was accelerated to have a shorter breakthrough time than its pure form. The larger differences in solubility parameter between a solvent mixture and glove resulted in a lower permeation rate. Solubility parameter theory provides a potential approach to interpret the changes of permeation properties for BTEX mixtures through nitrile gloves. Using a one-dimensional diffusion model based on Fick's law, the permeation concentrations of ASTM F739 experiments were appropriately simulated by the estimated diffusion coefficient and solubility. This study will be a fundamental work for the risk assessment of the potential dermal exposure of workers wearing protective gloves.

  4. Selection and screening for enzymes of nitrile metabolism

    Czech Academy of Sciences Publication Activity Database

    Martínková, Ludmila; Vejvoda, Vojtěch; Křen, Vladimír

    2008-01-01

    Roč. 133, č. 3 (2008), s. 318-326 ISSN 0168-1656 R&D Projects: GA AV ČR IAA500200708; GA ČR GA203/05/2267; GA MŠk(CZ) LC06010; GA MŠk OC 171 Institutional research plan: CEZ:AV0Z50200510 Keywords : nitrilase * nitrile hydratase * amidase Subject RIV: CE - Biochemistry Impact factor: 2.748, year: 2008

  5. Group 4 metallocene complexes with pendant nitrile groups

    Czech Academy of Sciences Publication Activity Database

    Pinkas, Jiří; Gyepes, R.; Kubišta, Jiří; Horáček, Michal; Lamač, Martin

    2011-01-01

    Roč. 696, 11-12 (2011), s. 2364-2372 ISSN 0022-328X R&D Projects: GA ČR GPP207/10/P200; GA MŠk(CZ) LC06070 Institutional research plan: CEZ:AV0Z40400503 Keywords : metallocene * group 4 elements * nitrile Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.384, year: 2011

  6. Synthesis and microbial transformation of Beta-amino nitriles

    Czech Academy of Sciences Publication Activity Database

    Winkler, M.; Martínková, Ludmila; Knall, A. C.; Krahulec, S.; Klempier, N.

    2005-01-01

    Roč. 61, - (2005), s. 4249-4260 ISSN 0040-4020 R&D Projects: GA ČR GA203/05/2267; GA MŠk OC D25.001 Grant - others:COST D25/0002/02 Institutional research plan: CEZ:AV0Z50200510 Keywords : microbial nitrile hydrolysis * enantioselectivity Subject RIV: EE - Microbiology, Virology Impact factor: 2.610, year: 2005

  7. Permeation of Military Fuels Through Nitrile-Coated Fabrics Used for Collapsible Fuel Storage Containers

    Science.gov (United States)

    2014-03-01

    materials when challenged with three separate military fuels. ..................................................................8 Figure 6. Effect of...three separate military fuels. The permeation rates for the ASTM Ref Fuel B were significantly larger for six of the nine fabrics. The Bell Avon...the Compatibility of Nitrile Rubber with Brazilian Biodiesel , Energy 2013, 49, 102. 6. Seil, D.; Wolf, F. Nitrile and Polyacrylic Rubbers, Rubber

  8. Nitrile-converting enzymes: an eco-friendly tool for industrial biocatalysis.

    Science.gov (United States)

    Ramteke, Pramod W; Maurice, Navodita G; Joseph, Babu; Wadher, Bharat J

    2013-01-01

    Nitriles are organic compounds bearing a − C ≡ N group; they are frequently known to occur naturally in both fauna and flora and are also synthesized chemically. They have wide applicability in the fields of medicine, industry, and environmental monitoring. However, the majority of nitrile compounds are considered to be lethal, mutagenic, and carcinogenic in nature and are known to cause potential health problems such as nausea, bronchial irritation, respiratory distress, convulsions, coma, and skeletal deformities in humans. Nitrile-converting enzymes, which are extracted from microorganisms, are commonly termed nitrilases and have drawn the attention of researchers all over the world to combat the toxicity of nitrile compounds. The present review focuses on the utility of nitrile-converting enzymes, sources, classification, structure, properties, and applications, as well as the future perspective on nitrilases. © 2013 International Union of Biochemistry and Molecular Biology, Inc.

  9. MOF-Derived Cu@Cu2O Nanocatalyst for Oxygen Reduction Reaction and Cycloaddition Reaction

    Directory of Open Access Journals (Sweden)

    Aram Kim

    2018-02-01

    Full Text Available Research on the synthesis of nanomaterials using metal-organic frameworks (MOFs, which are characterized by multi-functionality and porosity, as precursors have been accomplished through various synthetic approaches. In this study, copper and copper oxide nanoparticles were fabricated within 30 min by a simple and rapid method involving the reduction of a copper(II-containing MOF with sodium borohydride solution at room temperature. The obtained nanoparticles consist of a copper core and a copper oxide shell exhibited catalytic activity in the oxygen reduction reaction. The as-synthesized Cu@Cu2O core-shell nanocatalyst exhibited an enhanced limit current density as well as onset potential in the electrocatalytic oxygen reduction reaction (ORR. Moreover, the nanoparticles exhibited good catalytic activity in the Huisgen cycloaddition of various substituted azides and alkynes under mild reaction conditions.

  10. Solid-state Photochemical [2+ 2] Cycloaddition Reaction of ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 129; Issue 2. Solid-state Photochemical [2+2] Cycloaddition Reaction of Hydrogen-Bonded Zn(II) Metal Complex Containing Several Parallel C=C Bonds. ABDUL MALIK P PEEDIKAKKAL. Regular Article Volume 129 Issue 2 February 2017 pp 239-247 ...

  11. Cycloaddition Reaction of Hydrogen-Bonded Zn(II)

    Indian Academy of Sciences (India)

    J. Chem. Sci. Vol. 129, No. 2, February 2017, pp. 239–247. c Indian Academy of Sciences. DOI 10.1007/s12039-016-1218-6. REGULAR ARTICLE. Solid-state Photochemical [2+2] Cycloaddition Reaction of. Hydrogen-Bonded Zn(II) Metal Complex Containing Several Parallel. C=C Bonds. ABDUL MALIK P PEEDIKAKKAL.

  12. cyclo-addition reaction of triplet carbonyl compounds to substituted ...

    Indian Academy of Sciences (India)

    Abstract. Regioselectivity of the photochemical [2 + 2] cyclo-addition of triplet carbonyl compounds with a series of ground state electron-rich and electron-poor alkenes, the Paterno-Büchi reaction, is studied. Activation barriers for the first step of the triplet reaction are computed in the case of the O-attack. Next, the observed ...

  13. Recent developments in gold-catalyzed cycloaddition reactions

    Directory of Open Access Journals (Sweden)

    Fernando López

    2011-08-01

    Full Text Available In the last years there have been extraordinary advances in the development of gold-catalyzed cycloaddition processes. In this review we will summarize some of the most remarkable examples, and present the mechanistic rational underlying the transformations.

  14. Nitrile O-ring Cracking: A Case of Vacuum Flange O-ring Failures

    Energy Technology Data Exchange (ETDEWEB)

    Dees, Craig

    2016-07-01

    A review of recent nitrile O-ring failures in ISO-KF vacuum flange connections in glovebox applications is presented. An investigation of a single “isolated” o-ring failure leads to the discovery of cracked nitrile o-rings in a glovebox atmospheric control unit. The initial cause of the o-ring failure is attributed to ozone degradation. However, additional investigation reveals nitrile o-ring cracking on multiple gloveboxes and general purpose piping, roughly 85% of the nitrile o-rings removed for inspection show evidence of visible cracking after being in service for 18 months or less. The results of material testing and ambient air testing is presented, elevated ozone levels are not found. The contributing factors of o-ring failure, including nitrile air sensitivity, inadequate storage practices, and poor installation techniques, are discussed. A discussion of nitrile o-ring material properties, the benefits and limitations, and alternate materials are discussed. Considerations for o-ring material selection, purchasing, storage, and installation are presented in the context of lessons learned from the nitrile o-ring cracking investigation. This paper can be presented in 20 minutes and does not require special accommodations or special audio visual devices.

  15. Ionic elastomers based on carboxylated nitrile rubber (XNBR and magnesium aluminum layered double hydroxide (hydrotalcite

    Directory of Open Access Journals (Sweden)

    A. Laskowska

    2014-06-01

    Full Text Available The presence of carboxyl groups in carboxylated nitrile butadiene rubber (XNBR allows it to be cured with different agents. This study considers the effect of crosslinking of XNBR by magnesium aluminum layered double hydroxide (MgAl-LDH, known also as hydrotalcite (HT, on rheometric, mechano-dynamical and barrier properties. Results of XNBR/HT composites containing various HT loadings without conventional curatives are compared with XNBR compound crosslinked with commonly used zinc oxide. Hydrotalcite acts as an effective crosslinking agent for XNBR, as is particularly evident from rheometric and Fourier transform infrared spectroscopy (FTIR studies. The existence of ionic crosslinks was also detected by dynamic mechanical analysis (DMA of the resulting composites. DMA studies revealed that the XNBR/HT composites exhibited two transitions – one occurring at low temperature is associated to the Tg of elastomer and the second at high temperature corresponds to the ionic transition temperature Ti. Simultaneous application of HT as a curing agent and a filler may deliver not only environmentally friendly, zinc oxide-free rubber product but also ionic elastomer composite with excellent mechanical, barrier and transparent properties.

  16. Integrity of Disposable Nitrile Exam Gloves Exposed to Simulated Movement

    Science.gov (United States)

    Phalen, Robert N.; Wong, Weng Kee

    2011-01-01

    Every year, millions of health care, first responder, and industry workers are exposed to chemical and biological hazards. Disposable nitrile gloves are a common choice as both a chemical and physical barrier to these hazards, especially as an alternative to natural latex gloves. However, glove selection is complicated by the availability of several types or formulations of nitrile gloves, such as low-modulus, medical-grade, low-filler, and cleanroom products. This study evaluated the influence of simulated movement on the physical integrity (i.e., holes) of different nitrile exam glove brands and types. Thirty glove products were evaluated out-of-box and after exposure to simulated whole-glove movement for 2 hr. In lieu of the traditional 1-L water-leak test, a modified water-leak test, standardized to detect a 0.15 ± 0.05 mm hole in different regions of the glove, was developed. A specialized air inflation method simulated bidirectional stretching and whole-glove movement. A worst-case scenario with maximum stretching was evaluated. On average, movement did not have a significant effect on glove integrity (chi-square; p=0.068). The average effect was less than 1% between no movement (1.5%) and movement (2.1%) exposures. However, there was significant variability in glove integrity between different glove types (p ≤ 0.05). Cleanroom gloves, on average, had the highest percentage of leaks, and 50% failed the water-leak test. Low-modulus and medical-grade gloves had the lowest percentages of leaks, and no products failed the water-leak test. Variability in polymer formulation was suspected to account for the observed discrepancies, as well as the inability of the traditional 1-L water-leak test to detect holes in finger/thumb regions. Unexpectedly, greater than 80% of the glove defects were observed in the finger and thumb regions. It is recommended that existing water-leak tests be re-evaluated and standardized to account for product variability. PMID:21476169

  17. Base induced chemical conversion of 3-carbamoyl-2-isoxazolines.

    Science.gov (United States)

    Nishiwaki, Nagatoshi; Maki, Asaka; Ariga, Masahiro

    2009-01-01

    3-Carbamoyl-2-isoxazolines, prepared by cycloaddition of functionalized nitrile oxide, serve as masked 3-unsubstituted isoxazolines to afford 2-isoxazoline-3-carboxylic acid, beta-cyanoalcohol, alpha,beta-unsaturated nitrile, and alpha,beta-unsaturated amide upon heating in the alkaline solution. The present reaction is also applicable to synthesis of 3,4-difunctionalized isoxazoles and beta-hydroxy-gamma-lactone.

  18. Carboxylated nitrile butadiene rubber/hybrid filler composites

    Directory of Open Access Journals (Sweden)

    Ahmad Mousa

    2012-08-01

    Full Text Available The surface properties of the OSW and NLS are measured with the dynamic contact-angle technique. The x-ray photoelectron spectroscopy (XPS of the OSW reveals that the OSW possesses various reactive functional groups namely hydroxyl groups (OH. Hybrid filler from NLS and OSW were incorporated into carboxylated nitrile rubber (XNBR to produce XNBR hybrid composites. The reaction of OH groups from the OSW with COOH of the XNBR is checked by attenuated total reflectance spectra (ATR-IR of the composites. The degree of curing ΔM (maximum torque-minimum torque as a function of hybrid filler as derived from moving die rheometer (MDR is reported. The stress-strain behavior of the hybrid composites as well as the dynamic mechanical thermal analysis (DMTA is studied. Bonding quality and dispersion of the hybrid filler with and in XNBR are examined using scanning-transmission electron microscopy (STEM in SEM.

  19. Nitrilases in nitrile biocatalysis: recent progress and forthcoming research

    Science.gov (United States)

    2012-01-01

    Over the past decades, nitrilases have drawn considerable attention because of their application in nitrile degradation as prominent biocatalysts. Nitrilases are derived from bacteria, filamentous fungi, yeasts, and plants. In-depth investigations on their natural sources function mechanisms, enzyme structure, screening pathways, and biocatalytic properties have been conducted. Moreover, the immobilization, purification, gene cloning and modifications of nitrilase have been dwelt upon. Some nitrilases are used commercially as biofactories for carboxylic acids production, waste treatment, and surface modification. This critical review summarizes the current status of nitrilase research, and discusses a number of challenges and significant attempts in its further development. Nitrilase is a significant and promising biocatalyst for catalytic applications. PMID:23106943

  20. Nitrilases in nitrile biocatalysis: recent progress and forthcoming research

    Directory of Open Access Journals (Sweden)

    Gong Jin-Song

    2012-10-01

    Full Text Available Abstract Over the past decades, nitrilases have drawn considerable attention because of their application in nitrile degradation as prominent biocatalysts. Nitrilases are derived from bacteria, filamentous fungi, yeasts, and plants. In-depth investigations on their natural sources function mechanisms, enzyme structure, screening pathways, and biocatalytic properties have been conducted. Moreover, the immobilization, purification, gene cloning and modifications of nitrilase have been dwelt upon. Some nitrilases are used commercially as biofactories for carboxylic acids production, waste treatment, and surface modification. This critical review summarizes the current status of nitrilase research, and discusses a number of challenges and significant attempts in its further development. Nitrilase is a significant and promising biocatalyst for catalytic applications.

  1. Cure and mechanical properties of carboxylated nitrile rubber (XNBR) vulcanized by alkaline earth metal compounds

    Science.gov (United States)

    Tulyapitak, Tulyapong

    Compounds of carboxylated nitrile rubber (XNBR) with alkaline metal oxides and hydroxide were prepared, and their cure and mechanical properties were investigated. Magnesium oxide (MgO) with different specific surface areas (45, 65, and 140 m2/g) was used. Increased specific surface area and concentration of MgO resulted in higher cure rate. Optimum stiffness, tensile strength, and ultimate strain required an equimolar amount of acidity and MgO. The effect of specific surface area on tensile properties was not significant. Crosslink density of XNBR-MgO vulcanizates increased with increased amounts of MgO. ATR-IR spectroscopy showed that neutralization occurs in two steps: (1) During mixing and storage, MgO reacts with carboxyl groups (RCOOH) to give RCOOMgOH. (2) Upon curing, these react bimolecularly to form RCOOMgOOCR and Mg(OH)2. Dynamic mechanical thermal analysis revealed an ionic transition at higher temperature, in addition to the glass transition. The ionic transition shifts to higher temperature with increasing MgO concentration. Like MgO-XNBR systems, cure rates of XNBR-calcium hydroxide (Ca(OH)2) and XNBR-barium oxide (BaO) compounds increased with increased content of curing agents. Curing by these two agents resulted in ionic crosslinks. To ensure optimum tensile properties, equimolar amounts of carboxyl groups and curing agents were required. Dynamic mechanical analysis revealed the ionic transition in these two systems. It shifted to higher temperature with increased amounts of curing agents. In contrast to MgO, Ca(OH)2, and BaO, calcium oxide (CaO) gave results similar to those for thermally cured samples. No ionic transition was observed in XNBR-CaO systems. Tensile strength of XNBR depended on the strength of ionic crosslinks, which was dependent on the size of the alkaline metal ions.

  2. Chemical Resistance of Disposable Nitrile Gloves Exposed to Simulated Movement

    Science.gov (United States)

    Phalen, Robert N.; Wong, Weng Kee

    2012-01-01

    Large discrepancies between laboratory permeation testing and field exposures have been reported, with indications that hand movement could account for a portion of these differences. This study evaluated the influence of simulated movement on chemical permeation of 30 different disposable nitrile glove products. Products were investigated out-of-box and with exposure to simulated whole-glove movement. Permeation testing was conducted using ethanol as a surrogate test chemical. A previously designed pneumatic system was used to simulate hand movement. No movement and movement tests were matched-paired to control for environmental conditions, as were statistical analyses. Permeation data were collected for a 30-min exposure period or until a breakthrough time (BT) and steady-state permeation rate (SSPR) could be determined. A third parameter, area under the curve at 30 min (AUC-30), was used to estimate potential worker exposure. With movement, a significant decrease in BT (p ≤ 0.05), ranging from 6–33%, was observed for 28 products. The average decrease in BT was 18% (p ≤ 0.001). With movement, a significant increase in SSPR (p ≤ 0.05), ranging from 1–78%, was observed with 25 products. The average increase in SSPR was 18% (p ≤ 0.001). Significant increases in AUC-30 (p ≤ 0.05), ranging from 23–277%, were also observed for all products where it could be calculated. On average, there was a 58% increase (p ≤ 0.001). The overall effect of movement on permeation through disposable nitrile gloves was significant. Simulated movement significantly shortened the BT, increased the SSPR, and increased the cumulative 30-min exposure up to three times. Product variability also accounted for large differences, up to 40 times, in permeation and cumulative exposure. Glove selection must take these factors into account. It cannot be assumed that all products will perform in a similar manner. PMID:23009187

  3. Characterisation of the nitrile biocatalytic activity of rhodococcus rhodochrous ATCC BAA-870

    CSIR Research Space (South Africa)

    Frederick, J

    2006-10-01

    Full Text Available -hydrolysing enzymes include the production of amides and acids such as acrylamide, nicotinic acid and lactic acid from their corresponding nitriles, and the conversion of a–aminonitriles to optically active aminoacids...

  4. Rhodium-Catalyzed Transannulation of 1,2,3-Triazoles with Nitriles

    Science.gov (United States)

    Horneff, Tony; Chuprakov, Stepan; Chernyak, Natalia

    2009-01-01

    Stable and readily available 1-sulfonyl triazoles are converted to the corresponding imidazoles in good to excellent yields via a rhodium(II)-catalyzed reaction with nitriles. Rhodium iminocarbenoids are proposed intermediates. PMID:18855475

  5. Changes in chemical permeation of disposable latex, nitrile, and vinyl gloves exposed to simulated movement.

    Science.gov (United States)

    Phalen, Robert N; Le, Thi; Wong, Weng Kee

    2014-01-01

    Glove movement can affect chemical permeation of organic compounds through polymer glove products. However, conflicting reports make it difficult to compare the effects of movement on chemical permeation through commonly available glove types. The aim of this study was to evaluate the effect of movement on chemical permeation of an organic solvent through disposable latex, nitrile, and vinyl gloves. Simulated whole-glove permeation testing was conducted using ethyl alcohol and a previously designed permeation test system. With exposure to movement, a significant decrease (p ≤ 0.001) in breakthrough time (BT) was observed for the latex (-23%) and nitrile gloves (-31%). With exposure to movement, only the nitrile glove exhibited a significant increase (p ≤ 0.001) in steady-state permeation rate (+47%) and cumulative permeation at 30 min (+111%). Even though the nitrile glove provided optimum chemical resistance against ethyl alcohol, it was most affected by movement. With exposure to movement, the latex glove was an equivalent option for overall worker protection, because it was less affected by movement and the permeation rate was lower than that of the nitrile glove. In contrast, the vinyl glove was the least affected by movement, but did not provide adequate chemical resistance to ethyl alcohol in comparison with the nitrile and latex gloves. Glove selection should take movement and polymer type into account. Some glove polymer types are less affected by movement, most notably the latex glove in this test. With nitrile gloves, at least a factor of three should be used when attempting to assign a protection factor when repetitive hand motions are anticipated. Ultimately, the latex gloves outperformed nitrile and vinyl in these tests, which evaluated the effect of movement on chemical permeation. Future research should aim to resolve some of the observed discrepancies in test results with latex and vinyl gloves.

  6. Selective Hydrogenation of Nitriles to Primary Amines by using a Cobalt Phosphine Catalyst.

    Science.gov (United States)

    Adam, Rosa; Bheeter, Charles Beromeo; Cabrero-Antonino, Jose R; Junge, Kathrin; Jackstell, Ralf; Beller, Matthias

    2017-03-09

    A general procedure for the catalytic hydrogenation of nitriles to primary amines by using a non-noble metal-based system is presented. Co(acac) 3 in combination with tris[2-(dicyclohexylphosphino)ethyl]phosphine efficiently catalyzes the selective hydrogenation of a wide range of (hetero)aromatic and aliphatic nitriles to give the corresponding amines. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Biotransformation of nitriles by Rhodococcus equi A4 immobilized in LentiKats

    Czech Academy of Sciences Publication Activity Database

    Kubáč, David; Čejková, A.; Masák, J.; Jirků, V.; Lemaire, M.; Gallienne, E.; Bolte, J.; Stloukal, R.; Martínková, Ludmila

    2006-01-01

    Roč. 39, - (2006), s. 59-61 ISSN 1381-1177 R&D Projects: GA ČR GA203/05/2267; GA MŠk OC D25.001; GA AV ČR IAA4020213 Institutional research plan: CEZ:AV0Z50200510 Keywords : nitrile hydratase * amidase * nitriles Subject RIV: EE - Microbiology, Virology Impact factor: 2.149, year: 2006

  8. Competitive adsorptions of nitrile hydratase and amidase on polyacrylonitrile and its effect on surface modification.

    Science.gov (United States)

    Babu, Vikash; Choudhury, Bijan

    2012-01-01

    In this study, enzymatic surface modification of polyacrylonitrile was studied using nitrile metabolizing enzyme of Amycolatopsis sp. IITR 215. During enzymatic treatment of polyacrylonitrile at pH of 5.8 and 7, it was observed that the conversion of cyano group to carboxylic acid at pH 5.8 was three times higher than at pH 7. This difference in enzymatic treatment efficiency was explained by studying the differences in adsorption profiles of nitrile hydratase and amidase on polyacrylonitrile at pH of 5.8 and 7. Adsorption profiles were determined by monitoring the unbound activities of these two enzymes in the supernatant. From the specific activity profiles of bound nitrile hydratase and amidase it was concluded that more specific binding of nitrile hydratase was observed at pH 5.8 as compared to pH 7. In case of amidase, optimum adsorption was obtained at pH 5.8 within 5h whereas in case of pH 7 it was obtained within 20 h. Thus at pH 7, sequential adsorption of nitrile hydratase and amidase was observed and this adsorption profile was similar to the Vroman effect reported during plasma protein adsorption at solid-liquid interface. Ideally, specific nitrile hydratase adsorption followed by sequential adsorption of amidase may enhance higher conversion of cyano group to carboxylic acid. Copyright © 2011 Elsevier B.V. All rights reserved.

  9. A Single Mutation Increases the Activity and Stability of Pectobacterium carotovorum Nitrile Reductase.

    Science.gov (United States)

    Zhou, Zheng; Li, Min; Xu, Jian-He; Zhang, Zhi-Jun

    2018-03-02

    Nitrile reductases are considered to be promising and environmentally benign nitrile-reducing biocatalysts to replace traditional metal catalysts. Unfortunately, the catalytic efficiencies of the nitrile reductases reported so far are very low. To date, all attempts to increase the catalytic activity of nitrile reductases by protein engineering have failed. In this work, we successfully increased the specific activity of a nitrile reductase from Pectobacterium carotovorum from 354 to 526 U g prot -1 by engineering the substrate binding pocket; moreover, the thermostability was also improved (≈2-fold), showing half-lives of 140 and 32 h at 30 and 40 °C, respectively. In the bioreduction of 2-amino-5-cyanopyrrolo[2,3-d]pyrimidin-4-one (preQ 0 ) to 2-amino-5-aminomethylpyrrolo[2,3-d]pyrimidin-4-one (preQ 1 ), the variant was advantageous over the wild-type enzyme with a higher reaction rate and complete conversion of the substrate within a shorter period. Homology modeling and docking analysis revealed some possible origins of the increased activity and stability. These results establish a solid basis for future engineering of nitrile reductases to increase the catalytic efficiency further, which is a prerequisite for applying these novel biocatalysts in synthetic chemistry. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Formation of nitrile species on Ag nanostructures supported on a-Al2O3: a new corrosion route for silver exposed to the atmosphere

    Science.gov (United States)

    Peláez, R. J.; Espinós, J. P.; Afonso, C. N.

    2017-04-01

    The aging of supported Ag nanostructures upon storage in ambient conditions (air and room temperature) for 20 months has been studied. The samples are produced on glass substrates by pulsed laser deposition (PLD); first a 15 nm thick buffer layer of amorphous aluminum oxide (a-Al2O3) is deposited, followed by PLD of Ag. The amount of deposited Ag ranges from that leading to a discontinuous layer up to an almost-percolated layer with a thickness of oxidized faster, the smaller the amount of Ag. The corrosion leads to the formation of nitrile species due to the reaction between NO x species from the atmosphere adsorbed at the surface of Ag, and hydrocarbons adsorbed in defects at the surface of the a-Al2O3 layer during the deposition of the Ag nanostructures by PLD that migrate to the surface of the metal with time. The nitrile formation thus results in the main oxidation mechanism and inhibits almost completely the formation of sulphate/sulphide. Finally, the optical changes upon aging offer an easy-to-use tool for following the aging process. They are dominated by an enhanced absorption in the UV side of the spectrum and a blue-shift of the surface plasmon resonance that are, respectively, related to the formation of a dielectric overlayer on the Ag nanostructure and changes in the dimensions/features of the nanostructures, both due to the oxidation process.

  11. Nitrogen heteroaromatic cations by [2+2+2] cycloaddition

    Czech Academy of Sciences Publication Activity Database

    Čížková, Martina; Kolivoška, Viliam; Císařová, I.; Šaman, David; Pospíšil, Lubomír; Teplý, Filip

    2011-01-01

    Roč. 9, č. 2 (2011), s. 450-462 ISSN 1477-0520 R&D Projects: GA ČR GA203/09/1614; GA ČR GA203/09/0705; GA MŠk OC 140 Institutional research plan: CEZ:AV0Z40550506; CEZ:AV0Z40400503 Keywords : modular synthesis * N-heteroaromatic cation * [2+2+2] cycloaddition Subject RIV: CC - Organic Chemistry Impact factor: 3.696, year: 2011

  12. Criss-cross Cycloadditions on Ketazines Derived from Alicyclic Ketones

    Directory of Open Access Journals (Sweden)

    Milan Potacek

    2006-01-01

    Full Text Available The reactivity of alicyclic ketazines in criss-cross cycloadditions was investigated. They react with potassium cyanate and ammonium thiocyanate in the presence of acetic acid to form spirocyclic perhydro[1,2,4]triazolo[1,2-a][1,2,4]triazole-1,5-diones and perhydro[1,2,4]triazolo[1,2-a][1,2,4]triazole-1,5-dithiones, respectively, in relatively high yields.

  13. Reactions of uranium (III) and (IV) compounds with ketones, nitriles and acid chlorides. Towards a use of uranium complexes in organic synthesis

    International Nuclear Information System (INIS)

    Adam, Raymond

    1993-01-01

    In this research thesis, the author shows that various organic molecules can be interestingly transformed into uranium complexes with degrees of oxidation of +3 or +4. In a first part, the author describes reactions of carbonyl compounds with the UCl 4 -Na(Hg) reducing system. Then, he addresses reductions of ketones, nitriles and acid chlorides by a uranium (III) complex: Cp 3 U(THF). The third part reports a detailed study of the reduction of ketones by U(BH 4 ) 4 [fr

  14. Correlating Nitrile IR Frequencies to Local Electrostatics Quantifies Noncovalent Interactions of Peptides and Proteins.

    Science.gov (United States)

    Deb, Pranab; Haldar, Tapas; Kashid, Somnath M; Banerjee, Subhrashis; Chakrabarty, Suman; Bagchi, Sayan

    2016-05-05

    Noncovalent interactions, in particular the hydrogen bonds and nonspecific long-range electrostatic interactions are fundamental to biomolecular functions. A molecular understanding of the local electrostatic environment, consistently for both specific (hydrogen-bonding) and nonspecific electrostatic (local polarity) interactions, is essential for a detailed understanding of these processes. Vibrational Stark Effect (VSE) has proven to be an extremely useful method to measure the local electric field using infrared spectroscopy of carbonyl and nitrile based probes. The nitrile chemical group would be an ideal choice because of its absorption in an infrared spectral window transparent to biomolecules, ease of site-specific incorporation into proteins, and common occurrence as a substituent in various drug molecules. However, the inability of VSE to describe the dependence of IR frequency on electric field for hydrogen-bonded nitriles to date has severely limited nitrile's utility to probe the noncovalent interactions. In this work, using infrared spectroscopy and atomistic molecular dynamics simulations, we have reported for the first time a linear correlation between nitrile frequencies and electric fields in a wide range of hydrogen-bonding environments that may bridge the existing gap between VSE and H-bonding interactions. We have demonstrated the robustness of this field-frequency correlation for both aromatic nitriles and sulfur-based nitriles in a wide range of molecules of varying size and compactness, including small molecules in complex solvation environments, an amino acid, disordered peptides, and structured proteins. This correlation, when coupled to VSE, can be used to quantify noncovalent interactions, specific or nonspecific, in a consistent manner.

  15. Relaxation dynamics of carboxylated nitrile rubber filled with organomodified nanoclay

    Directory of Open Access Journals (Sweden)

    2008-05-01

    Full Text Available In order to improve the physical properties of elastomers and to get more insight into the polymer dynamics close to filler interphases a carboxylated nitrile rubber (XNBR was filled with up to 10 phr of layered silicate and investigated by dielectric and dynamic-mechanical analysis as well as by IR spectroscopy. Three relaxation processes have been detected beside the electrode polarization effect obtained in dielectric measurements. The relaxation process at low temperatures can be assigned to the β-process due to the rotational motion of side groups. Its temperature dependence follows an Arrhenius-like behaviour and there is no significant change in the shape of this process with the incorporation of filler. The glass transition at medium temperature shows a Vogel-Fulcher-dependence but seems to be independent of filler as well. At higher temperatures a new relaxation process was detected which is probably due to the formation of zinc-carboxyl-clusters. In dielectric and dynamic-mechanical measurements this process increases with increasing loading of organoclay and is shifted to higher temperature.

  16. Reactions of diiron m-aminocarbyne complexes containing nitrile ligands

    Directory of Open Access Journals (Sweden)

    Busetto Luigi

    2003-01-01

    Full Text Available The acetonitrile ligand in the mu-aminocarbyne complexes [Fe2{mu-CN(MeR}(mu-CO(CO(NCMe(Cp2][SO 3CF3] (R = Me, 2a, CH2Ph, 2b, Xyl, 2c (Xyl = 2,6-Me2C6H3 is readily displaced by halides and cyanide anions affording the corresponding neutral species [Fe2{mu-CN(MeR}(mu-CO(CO(X(Cp2 ] (X = Br, I, CN. Complexes 2 undergo deprotonation and rearrangement of the coordinated MeCN upon treatment with organolithium reagents. Trimethylacetonitrile, that does not contain acidic alpha hydrogens has been used in place of MeCN to form the complexes [Fe2{mu-CN(MeR}(mu-CO(CO(NCCMe3 (Cp2][SO3CF3] (7a-c. Attempts to replace the nitrile ligand in 3 with carbon nucleophiles (by reaction with RLi failed, resulting in decomposition products. However the reaction of 7c with LiCºCTol (Tol = C6H4Me, followed by treatment with HSO3CF3, yielded the imino complex [Fe2{mu-CN(MeXyl}(mu-CO(CO {N(HC(CºCC6H4Me-4CMe3}(Cp 2][SO3CF3 ] (8, obtained via acetilyde addition at the coordinated NCCMe3.

  17. Mechanism-Based Fluorogenic trans-Cyclooctene-Tetrazine Cycloaddition

    Czech Academy of Sciences Publication Activity Database

    Vázquez, Arcadio; Dzijak, Rastislav; Dračínský, Martin; Rampmaier, Robert; Siegl, Sebastian J.; Vrábel, Milan

    2017-01-01

    Roč. 56, č. 5 (2017), s. 1334-1337 ISSN 1433-7851 R&D Projects: GA ČR GJ15-06020Y; GA ČR GA15-11223S EU Projects: European Commission(XE) 677465 - SWEETOOLS Institutional support: RVO:61388963 Keywords : bioorthogonal chemistry * cycloaddition * click reactions * heterocycles * imaging agents Subject RIV: CC - Organic Chemistry OBOR OECD: Organic chemistry Impact factor: 11.994, year: 2016 http://onlinelibrary.wiley.com/doi/10.1002/anie.201610491/full

  18. Chemistry of nitrile anions in the interstellar medium

    Energy Technology Data Exchange (ETDEWEB)

    Carles, S.; Le Garrec, J.-L.; Biennier, L. [Institut de Physique de Rennes, Département de Physique Moléculaire, Astrophysique de Laboratoire, UMR CNRS 6251, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex (France); Guillemin, J.-C. [Institut des Sciences Chimiques de Rennes, Ecole Nationale Supérieure de Chimie de Rennes, CNRS, UMR 6226, 11 Allée de Beaulieu, CS 50837,35708 Rennes Cedex 7 (France)

    2015-12-31

    Despite the extreme conditions of temperature (down to 10K) and density (down to 100 molecules/cm{sup 3}), the giant molecular clouds and the circumstellar envelopes present a rich and complex chemistry. To date, more than 180 molecules have been detected in the InterStellar Medium (ISM) with a large abundance of nitriles (RC≡N). In addition, several anions have been recently observed in this medium: C{sub 4}H{sup ¯}, C{sub 6}H{sup ¯}, C{sub 8}H{sup ¯}, CN{sup ¯}, C{sub 3}N{sup ¯} and C{sub 5}N{sup ¯}. These last species should play a key role in the molecular growth towards complexity. To explore this hypothesis, their reactivity must be studied in the laboratory. The FALP-MS and the CRESU experimental apparatuses of the Rennes University are able to measure absolute rate coefficient of various chemical reactions, including the ion – molecule reactions, in gas phase at low temperature (from 300K for the FALP-MS down to 15K for the CRESU). Therefore, these experimental tools are particularly adapted to the kinetic studies of reactions potentially involved in the Interstellar Medium. One of the difficulties encountered in experiments with anions is their generation. We describe here the formation of the CN{sup ¯} and C{sub 3}N{sup ¯} anions by dissociative electron attachment on the molecular precursors BrCN and BrC{sub 3}N.

  19. VACUUM ULTRAVIOLET PHOTOABSORPTION SPECTRA OF NITRILE ICES FOR THEIR IDENTIFICATION ON PLUTO

    Energy Technology Data Exchange (ETDEWEB)

    Sivaraman, B.; Pavithraa, S. [Atomic Molecular and Optical Physics Division, Physical Research Laboratory, Ahmedabad, 380 009 (India); Lo, J.-I.; Cheng, B.-M. [National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan (China); Sekhar, B. N. Raja [Atomic and Molecular Physics Division, BARC at RRCAT, Indore, 452 013 (India); Hill, H. [International Space University, F-67400 Illkirch (France); Mason, N. J., E-mail: bhala@prl.res.in [Department of Physical Sciences, The Open University, Milton Keynes, MK7 6AA (United Kingdom)

    2016-07-10

    Icy bodies, such as Pluto, are known to harbor simple and complex molecules. The recent New Horizons flyby of Pluto has revealed a complex surface composed of bright and dark ice surfaces, indicating a rich chemistry based on nitrogen (N{sub 2}), methane (CH{sub 4}), and carbon monoxide (CO). Nitrile (CN) containing molecules such as acetonitrile (CH{sub 3}CN), propionitrile (CH{sub 3}CH{sub 2}CN), butyronitrile (CH{sub 3}CH{sub 2}CH{sub 2}CN), and isobutyronitrile ((CH{sub 3}){sub 2}CHCN) are some of the nitrile molecules that are known to be synthesized by radiative processing of such simple ices. Through the provision of a spectral atlas for such compounds we propose that such nitriles may be identified from the ALICE payload on board New Horizons .

  20. Ammoniation-dehydration of fatty acids into nitriles: heterogeneous or homogeneous catalysis?

    Science.gov (United States)

    Mekki-Berrada, Adrien; Bennici, Simona; Gillet, Jean-Philippe; Couturier, Jean-Luc; Dubois, Jean-Luc; Auroux, Aline

    2013-08-01

    Fatty nitriles have lately become of interest in the framework of biofuels and for the valorization of the oil part of biomass to form fine chemicals or polymers. The production of long-chain fatty nitriles by the direct reaction of acids with NH3 has not been extensively studied, although several catalysts have been developed and published as patents. The characterization of this reaction with and without catalyst is, to the best of our knowledge, performed for the first time in this study. Several catalysts with various acid-base features were tested, and the best catalysts at 250 °C (Zn- and In-based catalysts) were further studied. Catalytically active forms and models are proposed for the Zn- and In-based catalysts, and the kinetic parameters for the amide to nitrile reaction are evaluated. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Functionalized MIL-101 with imidazolium-based ionic liquids for the cycloaddition of CO2 and epoxides under mild condition

    Science.gov (United States)

    Liu, Dan; Li, Gang; Liu, Haiou

    2018-01-01

    A kind of multi-functional sites metal-organic framework (MOF) composite (MIL-101-IMBr) was successfully prepared by post-synthesis modification of MIL-101 with imidazolium-based ionic liquids. The ionic liquids not only functionalize as basic sites but also provide halide anions, which serve as a nucleophile in cycloaddition reaction. The prepared functional MOF materials were characterized by X-ray diffraction, fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, N2 adsorption-desorption and CO2 temperature programmed desorption. The results of fourier transform infrared spectroscopy and energy dispersive spectroscopy show that the MIL-101-IMBr composite was successfully synthesized. The N2 adsorption-desorption results clearly demonstrated that the modified composites still preserve high BET surface area and total pore volume. The composite exhibits high catalytic activity for the cycloaddition of CO2 with epoxides under mild and co-catalyst free conditions. The conversion of propylene oxide was 95.8% and the selectivity of cyclic carbonate was 97.6% under 0.8 MPa at 80 °C for 4 h. Moreover, the catalyst can be used for at least five times.

  2. Cobalt-Catalyzed [2π + 2π] Cycloadditions of Alkenes: Scope, Mechanism, and Elucidation of Electronic Structure of Catalytic Intermediates

    Science.gov (United States)

    2015-01-01

    Aryl-substituted bis(imino)pyridine cobalt dinitrogen compounds, (RPDI)CoN2, are effective precatalysts for the intramolecular [2π + 2π] cycloaddition of α,ω-dienes to yield the corresponding bicyclo[3.2.0]heptane derivatives. The reactions proceed under mild thermal conditions with unactivated alkenes, tolerating both amine and ether functional groups. The overall second order rate law for the reaction, first order with respect to both the cobalt precatalyst and the substrate, in combination with electron paramagnetic resonance (EPR) spectroscopic studies established the catalyst resting state as dependent on the identity of the precatalyst and diene substrate. Planar S =1/2 κ3-bis(imino)pyridine cobalt alkene and tetrahedral κ2-bis(imino)pyridine cobalt diene complexes were observed by EPR spectroscopy and in the latter case structurally characterized. The hemilabile chelate facilitates conversion of a principally ligand-based singly occupied molecular orbital (SOMO) in the cobalt dinitrogen and alkene compounds to a metal-based SOMO in the diene intermediates, promoting C–C bond-forming oxidative cyclization. Structure–activity relationships on bis(imino)pyridine substitution were also established with 2,4,6-tricyclopentyl-substituted aryl groups, resulting in optimized catalytic [2π + 2π] cycloaddition. The cyclopentyl groups provide a sufficiently open metal coordination sphere that encourages substrate coordination while remaining large enough to promote a challenging, turnover-limiting C(sp3)–C(sp3) reductive elimination. PMID:26030841

  3. Pengaruh Penggunaan Nitril Butadiene Rubber Dan Pale Crepe Pada Pembuatan Sol Karet Untuk Sepatu Pengaman

    OpenAIRE

    Yuniari, Arum

    2010-01-01

    Rubber sole for safety shoes was different on physical specification with general sole, especially on abrasion resistance and oil resistance. The objective of the study was to determine the effect of nitril butadiene rubber and pale crepe on physical properties of vulcanized rubber sole for safety shoes. Rubber sole for safety shoes was produced by blending pale crepe and nitril butadiene rubber with ratio of : 50/50; 60/40; 70/30 and 80/20 phr, respectively. Carbon black as filler was also v...

  4. Pengaruh penggunaan nitril butadiene rubber dan pale crepe pada pembuatan sol karet untuk sepatu pengaman

    OpenAIRE

    Arum Yuniari

    2010-01-01

    Abstract Rubber sole for safety shoes was different on physical specification with general sole, especially on abrasion resistance and oil resistance. The objective of the study was to determine the effect of nitril butadiene rubber and pale crepe on physical properties of vulcanized rubber sole for safety shoes. Rubber sole for safety shoes was produced by blending pale crepe and nitril butadiene rubber with ratio of : 50/50; 60/40; 70/30 and 80/20 phr, respectively. Carbon black as fill...

  5. Phenolphthalein-based Poly(arylene ether sulfone nitrile)s Multiblock Copolymers As Anion Exchange Membranes for Alkaline Fuel Cells.

    Science.gov (United States)

    Lai, Ao Nan; Wang, Li Sha; Lin, Chen Xiao; Zhuo, Yi Zhi; Zhang, Qiu Gen; Zhu, Ai Mei; Liu, Qing Lin

    2015-04-22

    A series of phenolphthalein-based poly(arylene ether sulfone nitrile)s (PESN) multiblock copolymers containing 1-methylimidazole groups (ImPESN) were synthesized to prepare anion exchange membranes (AEMs) for alkaline fuel cells. The ion groups were introduced selectively and densely on the unit of phenolphthalein as the hydrophilic segments, allowing for the formation of ion clusters. Strong polar nitrile groups were introduced into the hydrophobic segments with the intention of improving the dimensional stability of the AEMs. A well-controlled multiblock structure was responsible for the well-defined hydrophobic/hydrophilic phase separation and interconnected ion-transport channels, as confirmed by atomic force microscopy and small angle X-ray scattering. The ImPESN membranes with low swelling showed a relatively high water uptake, high hydroxide ion conductivity together with good mechanical, thermal and alkaline stability. The ionic conductivity of the membranes was in the range of 3.85-14.67×10(-2) S·cm(-1) from 30 to 80 °C. Moreover, a single H2/O2 fuel cell with the ImPESN membrane showed an open circuit voltage of 0.92 V and a maximum power density of 66.4 mW cm(-2) at 60 °C.

  6. An aeroplysinin-1 specific nitrile hydratase isolated from the marine sponge Aplysina cavernicola.

    Science.gov (United States)

    Lipowicz, Bartosz; Hanekop, Nils; Schmitt, Lutz; Proksch, Peter

    2013-08-21

    A nitrile hydratase (NHase) that specifically accepts the nitrile aeroplysinin-1 (1) as a substrate and converts it into the dienone amide verongiaquinol (7) was isolated, partially purified and characterized from the Mediterranean sponge Aplysina cavernicola; although it is currently not known whether the enzyme is of sponge origin or produced by its symbiotic microorganisms. The formation of aeroplysinin-1 and of the corresponding dienone amide is part of the chemical defence system of A. cavernicola. The latter two compounds that show strong antibiotic activity originate from brominated isoxazoline alkaloids that are thought to protect the sponges from invasion of bacterial pathogens. The sponge was shown to contain at least two NHases as two excised protein bands from a non denaturating Blue Native gel showed nitrile hydratase activity, which was not observed for control samples. The enzymes were shown to be manganese dependent, although cobalt and nickel ions were also able to recover the activity of the nitrile hydratases. The temperature and pH optimum of the studied enzymes were found at 41 °C and pH 7.8. The enzymes showed high substrate specificity towards the physiological substrate aeroplysinin-1 (1) since none of the substrate analogues that were prepared either by partial or by total synthesis were converted in an in vitro assay. Moreover de-novo sequencing by mass spectrometry was employed to obtain information about the primary structure of the studied NHases, which did not reveal any homology to known NHases.

  7. A high-throughput screening assay for distinguishing nitrile hydratases from nitrilases

    Directory of Open Access Journals (Sweden)

    Leticia Mara Lima Angelini

    2015-03-01

    Full Text Available A modified colorimetric high-throughput screen based on pH changes combined with an amidase inhibitor capable of distinguishing between nitrilases and nitrile hydratases. This enzymatic screening is based on a binary response and is suitable for the first step of hierarchical screening projects.

  8. Zr mesoporous molecular sieves as novel solid acid catalysts in synthesizing nitrile and caprolactam.

    Science.gov (United States)

    Nedumaran, D; Pandurangan, A

    2014-04-01

    Zr mesoporous materials with different Si/Zr ratio were synthesized by the surfactant-templated method involving cetyl trimethyl ammonium bromide (CTAB) as template and tetraethyl ortho silicate (TEOS) as organic source of silicon. The synthesized materials were labeled as SiZrMx (where x is Si/Zr = 10, 20 and 30). The BET analysis showed bimodal distribution of pores in SiZrMx structure. An attempt was made to generate super acidity on SiZrM20 by sulfation using sulfuric acid and ammonium sulfate (wt% = 4, 8 and 12). The NH3-TPD results revealed the presence of strong acidity in sulfated Zr-MCM-41. To understand the nature of acidity in Sulfated Zr-MCM-41, the efficiency of the materials is investigated in dehydration of Oximes. The industrially important materials caprolactam and intermediate nitrile were synthesized from their oximes in liquid phase system. Due to strong acidity in sulfated Zr-MCM-41, fast deactivation was observed during the synthesis of caprolactam but, the catalyst showed 96% nitrile selectivity. The strong acidity and medium strong acidity favoured the formation of nitrile and caprolactam respectively. This study revealed the molecular sieves were effective and eco-friendly solid acid catalysts for synthesizing caprolactam and nitrile.

  9. Selective biotransformation of substituted alicyclic nitriles by Rhodococcus equi A4

    Czech Academy of Sciences Publication Activity Database

    Martínková, Ludmila; Klempier, N.; Preiml, M.; Ovesná, Mária; Kuzma, Marek; Mylerová, Veronika; Křen, Vladimír

    2002-01-01

    Roč. 80, - (2002), s. 724-727 ISSN 0008-4042 R&D Projects: GA ČR GA524/00/1275; GA AV ČR IAA4020802 Keywords : nitrile hydratase * substituted cyclohexanecarbonitriles * cyclopentanecarbonitriles Subject RIV: EE - Microbiology, Virology Impact factor: 1.260, year: 2002

  10. Biotransformation of benzonitrile herbicides via the nitrile hydratase-amidase pathway in rhodococci

    Czech Academy of Sciences Publication Activity Database

    Veselá, Alicja Barbara; Pelantová, Helena; Šulc, Miroslav; Macková, M.; Lovecká, P.; Thimová, P.; Pasquarelli, F.; Pičmanová, Martina; Pátek, Miroslav; Bhalla, T. C.; Martínková, Ludmila

    2012-01-01

    Roč. 39, č. 12 (2012), s. 1811-1819 ISSN 1367-5435 R&D Projects: GA MŠk OC09046; GA ČR(CZ) GAP504/11/0394; GA ČR GD305/09/H008 Keywords : Nitrile hydratase * Amidase * Benzonitrile herbicides Subject RIV: EE - Microbiology, Virology Impact factor: 2.321, year: 2012

  11. An Aeroplysinin-1 Specific Nitrile Hydratase Isolated from the Marine Sponge Aplysina cavernicola

    Directory of Open Access Journals (Sweden)

    Peter Proksch

    2013-08-01

    Full Text Available A nitrile hydratase (NHase that specifically accepts the nitrile aeroplysinin-1 (1 as a substrate and converts it into the dienone amide verongiaquinol (7 was isolated, partially purified and characterized from the Mediterranean sponge Aplysina cavernicola; although it is currently not known whether the enzyme is of sponge origin or produced by its symbiotic microorganisms. The formation of aeroplysinin-1 and of the corresponding dienone amide is part of the chemical defence system of A. cavernicola. The latter two compounds that show strong antibiotic activity originate from brominated isoxazoline alkaloids that are thought to protect the sponges from invasion of bacterial pathogens. The sponge was shown to contain at least two NHases as two excised protein bands from a non denaturating Blue Native gel showed nitrile hydratase activity, which was not observed for control samples. The enzymes were shown to be manganese dependent, although cobalt and nickel ions were also able to recover the activity of the nitrile hydratases. The temperature and pH optimum of the studied enzymes were found at 41 °C and pH 7.8. The enzymes showed high substrate specificity towards the physiological substrate aeroplysinin-1 (1 since none of the substrate analogues that were prepared either by partial or by total synthesis were converted in an in vitro assay. Moreover de-novo sequencing by mass spectrometry was employed to obtain information about the primary structure of the studied NHases, which did not reveal any homology to known NHases.

  12. Host-guest complexation of pillar[6]arenes towards neutral nitrile guests.

    Science.gov (United States)

    Yuan, Mao-Sen; Chen, Huanqing; Du, Xianchao; Li, Jian; Wang, Jinyi; Jia, Xueshun; Li, Chunju

    2015-11-25

    The selective binding behavior of a series of nitrile derivatives by ethylated pillar[6]arene (EtP6A) is described. This work represents the first example of complexation of neutral guests by pillar[6]arenes, although those for pillar[5]arenes have been well documented.

  13. Biocatalytic Synthesis of Nitriles through Dehydration of Aldoximes: The Substrate Scope of Aldoxime Dehydratases.

    Science.gov (United States)

    Betke, Tobias; Higuchi, Jun; Rommelmann, Philipp; Oike, Keiko; Nomura, Taiji; Kato, Yasuo; Asano, Yasuhisa; Gröger, Harald

    2018-04-16

    Nitriles, which are mostly needed and produced by the chemical industry, play a major role in various industry segments, ranging from high-volume, low-price sectors, such as polymers, to low-volume, high-price sectors, such as chiral pharma drugs. A common industrial technology for nitrile production is ammoxidation as a gas-phase reaction at high temperature. Further popular approaches are substitution or addition reactions with hydrogen cyanide or derivatives thereof. A major drawback, however, is the very high toxicity of cyanide. Recently, as a synthetic alternative, a novel enzymatic approach towards nitriles has been developed with aldoxime dehydratases, which are capable of converting an aldoxime in one step through dehydration into nitriles. Because the aldoxime substrates are easily accessible, this route is of high interest for synthetic purposes. However, whenever a novel method is developed for organic synthesis, it raises the question of substrate scope as one of the key criteria for application as a "synthetic platform technology". Thus, the scope of this review is to give an overview of the current state of the substrate scope of this enzymatic method for synthesizing nitriles with aldoxime dehydratases. As a recently emerging enzyme class, a range of substrates has already been studied so far, comprising nonchiral and chiral aldoximes. This enzyme class of aldoxime dehydratases shows a broad substrate tolerance and accepts aliphatic and aromatic aldoximes, as well as arylaliphatic aldoximes. Furthermore, aldoximes with a stereogenic center are also recognized and high enantioselectivities are found for 2-arylpropylaldoximes, in particular. It is further noteworthy that the enantiopreference depends on the E and Z isomers. Thus, opposite enantiomers are accessible from the same racemic aldehyde and the same enzyme. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Computational study of a model system of enzyme-mediated [4+2] cycloaddition reaction.

    Science.gov (United States)

    Gordeev, Evgeniy G; Ananikov, Valentine P

    2015-01-01

    A possible mechanistic pathway related to an enzyme-catalyzed [4+2] cycloaddition reaction was studied by theoretical calculations at density functional (B3LYP, O3LYP, M062X) and semiempirical levels (PM6-DH2, PM6) performed on a model system. The calculations were carried out for the key [4+2] cycloaddition step considering enzyme-catalyzed biosynthesis of Spinosyn A in a model reaction, where a reliable example of a biological Diels-Alder reaction was reported experimentally. In the present study it was demonstrated that the [4+2] cycloaddition reaction may benefit from moving along the energetically balanced reaction coordinate, which enabled the catalytic rate enhancement of the [4+2] cycloaddition pathway involving a single transition state. Modeling of such a system with coordination of three amino acids indicated a reliable decrease of activation energy by ~18.0 kcal/mol as compared to a non-catalytic transformation.

  15. Computational study of a model system of enzyme-mediated [4+2] cycloaddition reaction.

    Directory of Open Access Journals (Sweden)

    Evgeniy G Gordeev

    Full Text Available A possible mechanistic pathway related to an enzyme-catalyzed [4+2] cycloaddition reaction was studied by theoretical calculations at density functional (B3LYP, O3LYP, M062X and semiempirical levels (PM6-DH2, PM6 performed on a model system. The calculations were carried out for the key [4+2] cycloaddition step considering enzyme-catalyzed biosynthesis of Spinosyn A in a model reaction, where a reliable example of a biological Diels-Alder reaction was reported experimentally. In the present study it was demonstrated that the [4+2] cycloaddition reaction may benefit from moving along the energetically balanced reaction coordinate, which enabled the catalytic rate enhancement of the [4+2] cycloaddition pathway involving a single transition state. Modeling of such a system with coordination of three amino acids indicated a reliable decrease of activation energy by ~18.0 kcal/mol as compared to a non-catalytic transformation.

  16. Intramolecular Azide to Alkene Cycloadditions for the Construction of Pyrrolobenzodiazepines and Azetidino-Benzodiazepines

    Czech Academy of Sciences Publication Activity Database

    Hemming, K.; Chambers, Christopher S.; Jamshaid, F.; O´Gorman, Paul A.

    2014-01-01

    Roč. 19, č. 10 (2014), s. 16737-16756 ISSN 1420-3049 Institutional support: RVO:61388971 Keywords : azide * cycloadditions * benzodiazepines Subject RIV: CC - Organic Chemistry Impact factor: 2.416, year: 2014

  17. Direct access to triazole-olefins through catalytic cycloaddition of azides to unsaturated aldehydes.

    Science.gov (United States)

    Li, Wenjun; Jia, Qianfa; Du, Zhiyun; Wang, Jian

    2013-10-03

    In situ formed dienamines as HOMO-raising dipolarophiles react with azides to afford the corresponding triazole-olefins in good to excellent yields via a catalytic inverse-electron-demand 1,3-dipolar cycloaddition process.

  18. Preparation of dispersible graphene through organic functionalization of graphene using a zwitterion intermediate cycloaddition approach

    NARCIS (Netherlands)

    Zhang, Xiaoyan; Browne, Wesley R.; Feringa, Ben L.

    2012-01-01

    Highly functionalized graphene were obtained through a zwitterion intermediate cycloaddition onto exfoliated graphene flakes under new reaction conditions. The functionalized graphene obtained formed stable dispersions in common solvents, including dimethylformamide (DMF), CHCl3 and water. Its

  19. Phase emerging from intramonolayer cycloaddition on micro-patterned monolayer

    Energy Technology Data Exchange (ETDEWEB)

    Tajuddin, Hairul A.; Manning, Robert J.; Leggett, Graham J.; Williams, Nicholas H. [Department of Chemistry, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia and Department of Chemistry, University of Sheffield, Sheffield S3 7HF (United Kingdom); Department of Chemistry, University of Sheffield, Sheffield S3 7HF (United Kingdom)

    2012-11-27

    Cu(I)-catalyzed cycloaddition between azide and acetylene, followed by hydrolysis of ester were performed on micro-patterned self-assembled monolayer to produce smaller features. The reactions were initially performed on mixed monolayers and analysed by water contact angle (CA) and confirmed by X-ray Photoelectron Spectroscopy (XPS). The contact angle measurement has shown a drastic wetting of water on the surface of mixed monolayer indicating that the terminal groups on mixed monolayer has changed into carboxylic acid and hydroxyl terminals. The reactions work in a similar way on micro-patterned SAM and analyzed by using friction force microscope. The emerging of the new lines with high friction force on the border suggested a successful intramonolayer reactions on the border of the patterned SAM.

  20. The cobalt-mediated [2+2+2]cycloaddition of thiophenes and benzofurans to alkynes

    Energy Technology Data Exchange (ETDEWEB)

    Malaska, M.J.

    1991-01-01

    The cobalt-mediated [2+2+2]cycloaddition of thiophenes and benzofurans to alkynes was investigated. The cocyclization of 2-propynyloxymethylthiophenes provided two types of cyclohexadiene complexes. It was found that one of these complexes could be converted to the other by a thermal rearrangement. This novel transformation was investigated by deuterium-labelling and kinetic studies, and a mechanism was proposed. The complexes could be oxidatively demetallated to provide the liberated organic framework. Further reorganization of these dienes were observed during the decomplexation process and in the presence of CpCo(C[sub 2]H[sub 4])[sub 2]. In this manner several new heterocyclic ring systems could be constructed from 2-substituted thiophenes. Following the success of the thiophene cyclizations, the cocyclization of the benzofuran nucleus was examined. Reagents and conditions were developed that provide an efficient synthesis of alkynols from carboxylic acids; other functional group interconversions of the alkynols were briefly studied. The synthesis and cyclization of 1-[7-methoxy-4-benzofuranyl]-3-butyn-2-ol produced a cobalt complex containing the A,B,C, and D rings of the morphine skeleton. A synthetic advantage of this methodology would be the ease of substitution at pharmaco-logically relevant C-6 and C-7 positions of the morphine framework. Synthetic routes using a cobalt cyclization strategy were proposed.

  1. A Concomitant Allylic Azide Rearrangement/Intramolecular Azide–Alkyne Cycloaddition Sequence

    Science.gov (United States)

    2015-01-01

    An intramolecular Huisgen cycloaddition of an interconverting set of isomeric allylic azides with alkynes affords substituted triazoles in high yield. The stereoisomeric vinyl-substituted triazoloxazines formed depend on the rate of cycloaddition of the different allylic azide precursors when the reaction is carried out under thermal conditions. In contrast, dimerized macrocyclic products were obtained when the reaction was done using copper(I)-catalyzed conditions, demonstrating the ability to control the reaction products through changing conditions. PMID:24635056

  2. Nitrile-converting enzymes as a tool to improve biocatalysis in organic synthesis: recent insights and promises.

    Science.gov (United States)

    Gong, Jin-Song; Shi, Jin-Song; Lu, Zhen-Ming; Li, Heng; Zhou, Zhe-Min; Xu, Zheng-Hong

    2017-02-01

    Nitrile-converting enzymes, including nitrilase and nitrile hydratase (NHase), have received increasing attention from researchers of industrial biocatalysis because of their critical role as a tool in organic synthesis of carboxylic acids and amides from nitriles. To date, these bioconversion approaches are considered as one of the most potential industrial processes using resting cells or purified enzymes as catalysts for production of food additives, pharmaceutical, and agrochemical precursors. This review focuses on the distribution and catalytic mechanism research of nitrile-converting enzymes in recent years. Molecular biology aspects to improve the biocatalytic performance of microbial nitrilase and NHase are demonstrated. The process developments of microbial nitrilase and NHase for organic synthesis are also discussed.

  3. An Efficient Synthesis of Nitriles from Aldoximes Using Diethyl Phosphorocyanidate under Mild Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Kieseung; An, Hyeonseong; Hwang, Chanyeon [Woosuk Univ.,Wanju (Korea, Republic of)

    2012-10-15

    Nitriles are valuable intermediates in organic synthesis not only because they serve as the appropriate precursors to various functional groups, but also because they are widely used as the key intermediates for pharmaceuticals, agrochemicals and various N-heterocyclic compounds. The cyano group itself is also frequently found in many biologically important molecules. Therefore, a variety of synthetic routes to nitriles from diverse chemical precursors have been developed. Among these routes, nitrile synthesis from aldoximes using an appropriate dehydrating agent has been a general and clean method. For this purpose, numerous reagents such as chlorosulfonyl isocyanate, di-2-pyridyl sulfite, Burgess reagent, [RuCl{sub 2}(p-cymene)]{sub 2}/MS, 4A, BOP, Pd(OAc){sub 2}/PPh{sub 3}, Cu(OAc){sub 2}/ultrasound have been developed. These reagents, however, may have limitations in some respects such as harsh reaction conditions, use of expensive or less readily available reagents, low yields, and lack of generality. Therefore, there is still a need to develop mild and general method for this conversion. Diethyl phosphorocyanidate (DEPC) was initially introduced as an efficient peptide coupling reagent, and has been utilized for useful organic reactions. Previously, we reported that 2-chloro-1-methylpyridinium iodide is an efficient and mild reagent for the dehydration of aldoximes to nitriles under mild conditions. In continuation of our interest in developing mild method for the conversion of aldoximes to nitriles, we herein wish to report the first application of DEPC to the efficient synthesis of nitriles from aldoximes under mild conditions (Scheme 1). In order to obtain the information regarding the optimum reaction conditions, 4-pyridine aldoxime (1a) was reacted with DEPC without base, and in presence of various base in CH{sub 2}Cl{sub 2} at rt for a prolonged reaction time (20 h) (Table 1). CH{sub 2}CI{sub 2} was chosen as reaction medium in this reaction due to the

  4. Characterization of a novel nitrilase, BGC4, from Paraburkholderia graminis showing wide-spectrum substrate specificity, a potential versatile biocatalyst for the degradation of nitriles.

    Science.gov (United States)

    Fan, Haiyang; Chen, Lifeng; Sun, Huihui; Wang, Hualei; Liu, Qinghai; Ren, Yuhong; Wei, Dongzhi

    2017-11-01

    To investigate the biodegradation of nitriles via the nitrilase-mediated pathway. A novel nitrilase, BGC4, was identified from proteobacteria Paraburkholderia graminis CD41M and its potential for use in biodegradation of toxic nitriles in industrial effluents was studied. BGC4 was overexpressed in Escherichia coli BL21 (DE3), the recombinant protein was purified and its enzymatic properties analysed. Maximum activity of BGC4 nitrilase was at 30 °C and pH 7.6. BGC4 has a broad substrate activity towards aliphatic, heterocyclic, and aromatic nitriles, as well as arylacetonitriles. Iminodiacetonitrile, an aliphatic nitrile, was the optimal substrate but comparable activities were also observed with phenylacetonitrile and indole-3-acetonitrile. BGC4-expressing cells degraded industrial nitriles, such as acrylonitrile, adiponitrile, benzonitrile, mandelonitrile, and 3-cyanopyridine, showing good tolerance and conversion rates. BGC4 nitrilase has wide-spectrum substrate specificity and is suitable for efficient biodegradation of toxic nitriles.

  5. Influence of radiation temperature on the crosslinking of nitrile rubber by electron beam irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Vijayabaskar, V. [Leibniz Institute of Polymer Research Dresden, Hohe Str. 6, 01069 Dresden (Germany)], E-mail: vijay.baskar@gmail.com; Stephan, M.; Kalaivani, S.; Volke, S.; Heinrich, G.; Dorschner, H. [Leibniz Institute of Polymer Research Dresden, Hohe Str. 6, 01069 Dresden (Germany); Bhowmick, A.K. [Rubber Technology Centre, Indian Institute of Technology, Kharagpur 721302 (India); Wagenknecht, U. [Leibniz Institute of Polymer Research Dresden, Hohe Str. 6, 01069 Dresden (Germany)

    2008-04-15

    Nitrile rubber with 18% acrylonitrile content in presence and absence of polyfunctional monomers like trimethylolpropane triacrylate (TMPTA), tripropyleneglycol diacrylate (TPGDA), tetramethylolmethane tetraacrylate (TMMT) and m-phenylene bismaleimide was subjected to electron beam irradiations at different temperatures. The structural changes with different doses of radiations were investigated with the help of FTIR spectroscopy (in the ATR mode), dynamic mechanical thermal analysis and sol-gel analysis. There was a decrease in the concentration of olefinic groups for this elastomer on radiation at high temperature as compared to the room temperature. The increase in crosslinking at elevated temperature was also revealed by the increase in % gel content and dynamic storage moduli with radiation dose. The lifetime of spurs, an important criterion for overlapping of spurs, was determined for both grafted and ungrafted nitrile rubber using a mathematical model. The ratio of scissioning to crosslinking for nitrile rubber was determined using Charlesby-Pinner equation. The mechanical properties were studied and the tensile strength was found to increase with grafting of polyfunctional monomers on irradiation at high temperature.

  6. Influence of radiation temperature on the crosslinking of nitrile rubber by electron beam irradiation

    Science.gov (United States)

    Vijayabaskar, V.; Stephan, M.; Kalaivani, S.; Volke, S.; Heinrich, G.; Dorschner, H.; Bhowmick, A. K.; Wagenknecht, U.

    2008-04-01

    Nitrile rubber with 18% acrylonitrile content in presence and absence of polyfunctional monomers like trimethylolpropane triacrylate (TMPTA), tripropyleneglycol diacrylate (TPGDA), tetramethylolmethane tetraacrylate (TMMT) and m-phenylene bismaleimide was subjected to electron beam irradiations at different temperatures. The structural changes with different doses of radiations were investigated with the help of FTIR spectroscopy (in the ATR mode), dynamic mechanical thermal analysis and sol-gel analysis. There was a decrease in the concentration of olefinic groups for this elastomer on radiation at high temperature as compared to the room temperature. The increase in crosslinking at elevated temperature was also revealed by the increase in % gel content and dynamic storage moduli with radiation dose. The lifetime of spurs, an important criterion for overlapping of spurs, was determined for both grafted and ungrafted nitrile rubber using a mathematical model. The ratio of scissioning to crosslinking for nitrile rubber was determined using Charlesby-Pinner equation. The mechanical properties were studied and the tensile strength was found to increase with grafting of polyfunctional monomers on irradiation at high temperature.

  7. Chemical functionalization of graphene via aryne cycloaddition: a theoretical study.

    Science.gov (United States)

    Zhao, Jing-xiang; Wang, Hong-xia; Gao, Bo; Wang, Xiao-guang; Cai, Qing-hai; Wang, Xuan-zhang

    2012-06-01

    Chemical functionalization of graphene provides a promising route to improve its solubility in water and organic solvents as well as modify its electronic properties, thus significantly expanding its potential applications. In this article, by using density functional theory (DFT) methods, we have studied the effects of the chemical functionalization of graphenes via aryne cycloaddition on its properties. We found that the adsorption of an isolated aryne group on the graphene sheet is very weak with the adsorption energy of -0.204 eV, even though two new single C-C interactions are formed between the aryne group and the graphene. However, the interaction of graphene with the aryne group can be greatly strengthened by (i) substituting the H-atoms in aryne group with F-, Cl-, -NO(2) (electron-withdrawing capability), or CH(3)-group (electron-donating capability), and (ii) increasing the coverage of the adsorbed aryne groups on the graphene sheet. As expected, the strongest bonding is found on the graphene edges, in which the adsorbed aryne groups prefer to be far away from each other. Interestingly, chemical functionalization with aryne groups leads to an opening of the band gap of graphene, which is dependent on the coverage of the adsorbed aryne groups. The present work provides an insight into the modifications of graphene with aryne groups in experiment.

  8. Coordinatively unsaturated ruthenium complexes as efficient alkyneazide cycloaddition catalysts

    KAUST Repository

    Lamberti, Marina

    2012-01-23

    The performance of 16-electron ruthenium complexes with the general formula Cp*Ru(L)X (in which L = phosphine or N-heterocyclic carbene ligand; X = Cl or OCH2CF3) was explored in azidealkyne cycloaddition reactions that afford the 1,2,3- triazole products. The scope of the Cp*Ru(PiPr 3)Cl precatalyst was investigated for terminal alkynes leading to new 1,5-disubstituted 1,2,3-triazoles in high yields. Mechanistic studies were conducted and revealed a number of proposed intermediates. Cp*Ru- (PiPr3)(2-HCCPh)Cl was observed and characterized by 1H, 13C, and 31P NMR at temperatures between 273 and 213 K. A rare example of N,N-κ2-phosphazide complex, Cp*Ru(κ2- iPr3PN3Bn)Cl, was fully characterized, and a single-crystal X-ray diffraction structure was obtained. DFT calculations describe a complete map of the catalytic reactivity with phenylacetylene and/or benzylazide. © 2012 American Chemical Society.

  9. From dimerization, to cycloaddition, to atom transfer cyclization: the further chemistry of TMM diradicals.

    Science.gov (United States)

    Maiti, Arup; Gerken, James B; Masjedizadeh, Mohammad R; Mimieux, Yvette S; Little, R Daniel

    2004-12-10

    We describe [a] the first examples of intramolecular cycloaddition of a TMM diyl to a remotely tethered aldehyde, [b] the effect of a Lewis acid upon the course of TMM chemistry, [c] examples of exclusive intramolecular cycloaddition, competitive cycloaddition and ATC, and exclusive ATC, and [d] a set of predictive guidelines with which to assess whether cycloaddition or ATC will be the preferred path, and when the two processes will be competitive. Remarkably, a wide variety of structures can be obtained simply by varying the length of the tether within the diazenes investigated. DFT calculations were used to probe the energy surfaces for both atom transfer and cycloaddition. The transition structure for atom transfer involving the captodative system indicates that it occurs earlier along the reaction coordinate than for a system having only one radical stabilizing group. This is consistent with the existence of an exothermic process leading from the initial diyl to the captodatively stabilized distonic diyl. Gratifyingly, theory agrees with observation and provides substantial insight into the chemistry.

  10. Studies on nitrile rubber degradation in zinc bromide completion fluid and its prevention by surface fluorination

    Science.gov (United States)

    Vega-Cantu, Yadira Itzel

    Poly(acrylonitrile-co-butadiene) or nitrile-butadiene rubber (NBR) is frequently used as an O-ring material in the oil extraction industry due to its excellent chemical properties and resistance to oil. However, degradation of NBR gaskets is known to occur during the well completion and oil extraction process where packers are exposed to completion fluids such as ZnBr2 brine. Under these conditions NBR exhibits accelerated chemical degradation resulting in embrittlement and cracking. Samples of NBR, poly(acrylonitrile) (PAN) and poly(butadiene) (PB) have been exposed to ZnBr2 based completion fluid, and analyzed by ATR and diffuse reflectance IR. Analysis shows the ZnBr2 based completion fluid promotes hydrolysis of the nitrile group to form amides and carboxylic groups. Analysis also shows that carbon-carbon double bonds in NBR are unaffected after short exposure to zinc bromide based completion fluid, but are quickly hydrolyzed in acidic bromide mixtures. Although fluoropolymers have excellent chemical resistance, their strength is less than nitrile rubber and replacing the usual gasket materials with fluoroelastomers is expensive. However, a fluoropolymer surface on a nitrile elastomer can provide the needed chemical resistance while retaining their strength. In this study, we have shown that this can be achieved by direct fluorination, a rather easy and inexpensive process. Samples of NBR O-rings have been fluorinated by exposure to F2 and F2/HF mixtures at various temperatures. Fluorination with F 2 produces the desired fluoropolymer layer; however, fluorination by F2/HF mixtures gave a smoother fluorinated layer at lower temperatures and shorter times. Fluorinated samples were exposed to ZnBr2 drilling fluid and solvents. Elemental analysis shows that the fluorinated layer eliminates ZnBr2 diffusion into the NBR polymeric matrix. It was also found that surface fluorination significantly retards the loss of mechanical properties such as elasticity, tensile

  11. Citrus Peel Additives for One-Pot Triazole Formation by Decarboxylation, Nucleophilic Substitution, and Azide-Alkyne Cycloaddition Reactions

    Science.gov (United States)

    Mendes, Desiree E.; Schoffstall, Allen M.

    2011-01-01

    This undergraduate organic laboratory experiment consists of three different reactions occurring in the same flask: a cycloaddition reaction, preceded by decarboxylation and nucleophilic substitution reactions. The decarboxylation and cycloaddition reactions occur using identical Cu(I) catalyst and conditions. Orange, lemon, and other citrus fruit…

  12. Dimerization of propargyl and homopropargyl 6-azido-6-deoxy-glycosides upon 1,3-dipolar cycloaddition

    Directory of Open Access Journals (Sweden)

    2008-08-01

    Full Text Available Copper-catalyzed, thermal or microwave promoted 1,3-dipolar cycloaddition (Click Reaction of 2-propynyl and 3-butynyl 2,3,4-tri-O-acetyl-6-azido-6-deoxy-glycopyranosides in the D-gluco, D-galacto and D-manno series afford the corresponding dimeric cycloaddition products.

  13. Journal of Chemical Sciences | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    Abstract. We have synthesized a series of novel isoxazolines via 1,3-dipolar cycloaddition reaction. Aromatic aldoximes undergo oxidative-dehydrogenation with chloramine-T to give nitrile oxides, which were reacted with chalcones to afford of 3,4,5-trisubstituted 4,5-dihydroisoxazolines in a good yield.

  14. One-pot synthesis of new series 3, 4, 5-trisubstituted ...

    Indian Academy of Sciences (India)

    Abstract. We have synthesized a series of novel isoxazolines via 1,3-dipolar cycloaddition reaction. Aromatic aldoximes undergo oxidative-dehydrogenation with chloramine-T to give nitrile oxides, which were reacted with chalcones to afford of 3,4,5-trisubstituted 4,5-dihydroisoxazolines in a good yield.

  15. 1,3-Dipolar Cycloadditions of Diazo Compounds in the Presence of Azides.

    Science.gov (United States)

    Aronoff, Matthew R; Gold, Brian; Raines, Ronald T

    2016-04-01

    The diazo group has untapped utility in chemical biology. The tolerance of stabilized diazo groups to cellular metabolism is comparable to that of azido groups. However, chemoselectivity has been elusive, as both groups undergo 1,3-dipolar cycloadditions with strained alkynes. Removing strain and tuning dipolarophile electronics yields diazo group selective 1,3-dipolar cycloadditions that can be performed in the presence of an azido group. For example, diazoacetamide but not its azido congener react with dehydroalanine residues, as in the natural product nisin.

  16. Copper-catalyzed azide alkyne cycloaddition polymer networks

    Science.gov (United States)

    Alzahrani, Abeer Ahmed

    The click reaction concept, introduced in 2001, has since spurred the rapid development and reexamination of efficient, high yield reactions which proceed rapidly under mild conditions. Prior to the discovery of facile copper catalysis in 2002, the thermally activated azide-alkyne or Huisgen cycloaddition reaction was largely ignored following its discovery in large part due to its slow kinetics, requirement for elevated temperature and limited selectivity. Now, arguably, the most prolific and capable of the click reactions, the copper-catalyzed azide alkyne cycloaddition (CuAAC) reaction is extremely efficient and affords exquisite control of the reaction. The orthogonally and chemoselectivity of this reaction enable its wide utility across varied scientific fields. Despite numerous inherent advantages and widespread use for small molecule synthesis and solution-based polymer chemistry, it has only recently and rarely been utilized to form polymer networks. This work focuses on the synthesis, mechanisms, and unique attributes of the CuAAC reaction for the fabrication of functional polymer networks. The photo-reduction of a series of copper(II)/amine complexes via ligand metal charge transfer was examined to determine their relative efficiency and selectivity in catalyzing the CuAAC reaction. The aliphatic amine ligands were used as an electron transfer species to reduce Cu(II) upon irradiation with 365 nm light while also functioning as an accelerating agent and as protecting ligands for the Cu(I) that was formed. Among the aliphatic amines studied, tertiary amines such as triethylamine (TEA), tetramethyldiamine (TMDA), N,N,N',N",N"-pentamethyldiethylenetriamine (PMDTA), and hexamethylenetetramine (HMTETA) were found to be the most effective. The reaction kinetics were accelerated by increasing the PMDETA : Cu(II) ratio with a ratio of ligand to Cu(II) of 4:1 yielding the maximum conversion in the shortest time. The sequential and orthogonal nature of the photo

  17. Synthesis of Isoxazole and 1,2,3-Triazole Isoindole Derivatives via Silver- and Copper-Catalyzed 1,3-Dipolar Cycloaddition Reaction

    Directory of Open Access Journals (Sweden)

    Mohamed Mehdi Rammah

    2016-03-01

    Full Text Available The CuI- or Ag2CO3-catalyzed [3+2] cycloaddition of propargyl-substituted dihydroisoindolin-1-one (3 with arylnitrile oxides 1a–d (Ar = Ph, p-MeC6H4, p-MeOC6H4, p-ClC6H4 produces in good yields novel 3,5-disubstituted isoxazoles 4 of the ethyl-2-benzyl-3-oxo-1-((3-arylisoxazol-5ylmethyl-2,3-dihydro-1H-isoindole-1-carboxylate type. With aryl azides 2a–d (Ar = Ph, p-MeC6H4, p-OMeC6H4, p-ClC6H4, a series of 1,4-disubstituted 1,2,3-triazoles 6 (ethyl-2-benzyl-3-oxo-1-((1-aryl-1H-1,2,3-triazol-4-ylmethyl-2,3-dihydro-1H-isoindole-1-carboxylates was obtained. The reactions proceed in a regioselective manner affording exclusively racemic adducts 4 and 6. Compared to the uncatalyzed cycloaddition, the yields are significantly improved in the presence of CuI as catalyst, without alteration of the selectivity. The regio- and stereochemistry of the cycloadducts has been corroborated by an X-ray diffraction study of 4a, and in the case of 6a by XH-correlation and HMBC spectra.

  18. Lateral extension of π conjugation along the bay regions of bisanthene through a diels-alder cycloaddition reaction

    KAUST Repository

    Li, Jinling

    2011-11-14

    Diels-Alder cycloaddition reactions at the bay regions of bisanthene (1) with dienophiles such as 1,4-naphthoquinone have been investigated. The products were submitted to nucleophilic addition followed by reductive aromatization reactions to afford the laterally extended bisanthene derivatives 2 and 3. Attempted synthesis of a larger expanded bisanthene 4 revealed an unexpected hydrogenation reaction at the last reductive aromatization step. Unusual Michael addition was observed on quinone 14, which was obtained by Diels-Alder reaction between 1 and 1,4-anthraquinone. Compounds 1-3 exhibited near-infrared (NIR) absorption and emission with high-to-moderate fluorescent quantum yields. Their structures and absorption spectra were studied by density function theory and non-planar twisted structures were calculated for 2 and 3. All compounds showed amphoteric redox behavior with multiple oxidation/reduction waves. Oxidative titration with SbCl 5 gave stable radical cations, and the process was followed by UV/Vis/NIR spectroscopic measurements. Their photostability was measured and correlated to their different geometries and electronic structures. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Review of organic nitrile incineration at the Toxic Substances Control Act Incinerator

    International Nuclear Information System (INIS)

    1997-10-01

    Lockheed Martin Energy Systems, Inc. (LMES) operates the East Tennessee Technology Park (ETTP), formerly called the Oak Ridge K-25 Site, where uranium was enriched under contract with the US Department of Energy (DOE). Currently, ETTP missions include environmental management, waste management (WM), and the development of new technologies. As part of its WM mission, ETTP operates the TSCA (Toxic Substances Control Act) Incinerator (TSCAI) for treatment of hazardous waste and polychlorinated biphenyls (PCBs) contaminated with low-level radioactivity. Beginning in the autumn of 1995, employees from diverse ETTP buildings and departments reported experiencing headaches, fatigue, depression, muscle aches, sleeplessness, and muscle tremors. These symptoms were judged by a physician in the ETTP Health Services Department to be consistent with chronic exposures to hydrogen cyanide (HCN). The National Institute for Occupational Safety and Health (NIOSH) was called in to perform a health hazard evaluation to ascertain whether the employees' illnesses were in fact caused by occupational exposure to HCN. The NIOSH evaluation found no patterns for employees' reported symptoms with respect to work location or department. NIOSH also conducted a comprehensive air sampling study, which did not detect airborne cyanides at the ETTP. Employees, however, expressed concerns that the burning of nitrile-bearing wastes at the TSCAI might have produced HCN as a combustion product. Therefore, LMES and DOE established a multidisciplinary team (TSCAI Technical Review Team) to make a more detailed review of the possibility that combustion of nitrile-bearing wastes at the TSCAI might have either released nitriles or created HCN as a product of incomplete combustion (PIC)

  20. Biotransformation of β-keto nitriles to chiral (S)-β-amino acids using nitrilase and ω-transaminase.

    Science.gov (United States)

    Mathew, Sam; Nadarajan, Saravanan Prabhu; Sundaramoorthy, Uthayasuriya; Jeon, Hyunwoo; Chung, Taeowan; Yun, Hyungdon

    2017-04-01

    To enzymatically synthesize enantiomerically pure β-amino acids from β-keto nitriles using nitrilase and ω-transaminase. An enzyme cascade system was designed where in β-keto nitriles are initially hydrolyzed to β-keto acids using nitrilase from Bradyrhizobium japonicum and subsequently β-keto acids were converted to β-amino acids using ω-transaminases. Five different ω-transaminases were tested for this cascade reaction, To enhance the yields of β-amino acids, the concentrations of nitrilase and amino donor were optimized. Using this enzymatic reaction, enantiomerically pure (S)-β-amino acids (ee > 99%) were generated. As nitrilase is the bottleneck in this reaction, molecular docking analysis was carried out to depict the poor affinity of nitrilase towards β-keto acids. A novel enzymatic route to generate enantiomerically pure aromatic (S)-β-amino acids from β-keto nitriles is demonstrated for the first time.

  1. Hydrolysis of ibuprofen nitrile and ibuprofen amide and deracemisation of ibuprofen using Nocardia corallina B-276.

    Science.gov (United States)

    Lievano, Ricardo; Pérez, Herminia Inés; Manjarrez, Norberto; Solís, Aida; Solís-Oba, Myrna

    2012-03-12

    A novel application of whole cells of Nocardia corallina B-276 for the deracemisation of ibuprofen is reported. This microorganism successfully hydrolysed ibuprofen nitrile to ibuprofen amide, and ibuprofen amide to ibuprofen, using a suspension of cells in a potassium phosphate buffer solution (0.1 M, pH = 7.0). These results can be explained by the presence of NHase and amidase enzymes, but the reactions are not enantioselective and low ee values were obtained. However, (R)-ibuprofen was isolated with > 99% ee by a deracemisation process catalysed by N. corallina B-276. This is the first report of this kind of catalysis with this microorganism.

  2. Hydrolysis of Ibuprofen Nitrile and Ibuprofen Amide and Deracemisation of Ibuprofen Using Nocardia corallina B-276

    Directory of Open Access Journals (Sweden)

    Myrna Solís-Oba

    2012-03-01

    Full Text Available A novel application of whole cells of Nocardia corallina B-276 for the deracemisation of ibuprofen is reported. This microorganism successfully hydrolysed ibuprofen nitrile to ibuprofen amide, and ibuprofen amide to ibuprofen, using a suspension of cells in a potassium phosphate buffer solution (0.1 M, pH = 7.0. These results can be explained by the presence of NHase and amidase enzymes, but the reactions are not enantioselective and low ee values were obtained. However, (R-ibuprofen was isolated with >99% ee by a deracemisation process catalysed by N. corallina B-276. This is the first report of this kind of catalysis with this microorganism.

  3. Improvement of Some Physical Properties of Loaded Nitrile Rubber Vulcanized by Ionizing Radiation

    International Nuclear Information System (INIS)

    Abdel-Aziz, M.M.; Basfar, A.A.; Mofti, S.

    2000-01-01

    The effect of four-selected polyfunctional compounds namely, tri methylacrylic ester, trimethylol propane trimethacrylate, zinc diacrylate and modified pentaerthritol triacrylate, as crosslinking agents, on the mechanical properties of radiation vulcanized nitrile rubber was studied. The effect of incorporation of either HAF-carbon black or fumed silica, as filler and reinforcing agents, on its mechanical properties was also studied. The co agent namely, tri methylacrylic ester, was found to produce a set of optimum mechanical properties, i.e. moderate crosslink density, good tensile strength and elasticity at low irradiation doses, i.e.40 kGy

  4. Carbohydrates as efficient catalysts for the hydration of α-amino nitriles.

    Science.gov (United States)

    Chitale, Sampada; Derasp, Joshua S; Hussain, Bashir; Tanveer, Kashif; Beauchemin, André M

    2016-11-01

    Directed hydration of α-amino nitriles was achieved under mild conditions using simple carbohydrates as catalysts exploiting temporary intramolecularity. A broadly applicable procedure using both formaldehyde and NaOH as catalysts efficiently hydrated a variety of primary and secondary susbtrates, and allowed the hydration of enantiopure substrates to proceed without racemization. This work also provides a rare comparison of the catalytic activity of carbohydrates, and shows that the simple aldehydes at the basis of chemical evolution are efficient organocatalysts mimicking the function of hydratase enzymes. Optimal catalytic efficiency was observed with destabilized aldehydes, and with difficult substrates only simple carbohydrates such as formaldehyde and glycolaldehyde proved reliable.

  5. Cyclic compounds of tetracoordinated boron from 5-amino-1,2,4-triazole and aromatic nitriles

    International Nuclear Information System (INIS)

    Dorokhov, V.A.; Amamchyan, A.R.; Bochkareva, M.N.; Teslya, I.A.; Starikova, Z.A.

    1987-01-01

    New cyclic compounds of tetracoordinated boron - dialkylboryl-[(1,2,4-triazole-5-yl)-amidinate] from 5-amino-1,2,4-triazole, aromatic nitriles and trialkylborane have been synthesized. It is shown that in dialkylboryl derivatives of 5-amino-1,2,4-triazole forming crystalline dimers, R 2 B (R=Pr, Bu) groups are bonded to circular nitrogen atoms. The X-ray diffraction method was used to determine crystalline and molecular structures of dipropylboryl-[(1,2,4-triazole-5-yl)benzamidinate

  6. Hydrolysis of Ibuprofen Nitrile and Ibuprofen Amide and Deracemisation of Ibuprofen Using Nocardia corallina B-276

    OpenAIRE

    Myrna Solís-Oba; Norberto Manjarrez; Aida Solís; Ricardo Lievano; Herminia Inés Pérez

    2012-01-01

    A novel application of whole cells of Nocardia corallina B-276 for the deracemisation of ibuprofen is reported. This microorganism successfully hydrolysed ibuprofen nitrile to ibuprofen amide, and ibuprofen amide to ibuprofen, using a suspension of cells in a potassium phosphate buffer solution (0.1 M, pH = 7.0). These results can be explained by the presence of NHase and amidase enzymes, but the reactions are not enantioselective and low ee values were obtained. However, (R)-ibuprofen was is...

  7. Copper-free 'click' : 1,3-dipolar cycloaddition of azides and arynes

    NARCIS (Netherlands)

    Campbell-Verduyn, Lachlan; Elsinga, Philip H.; Mirfeizi, Leila; Dierckx, Rudi A.; Feringa, Ben L.

    2008-01-01

    Arynes formed through fluoride-promoted ortho-elimination of o-(trimethylsilyl)aryl triflates can undergo [3 + 2] cycloaddition with various azides to form substituted benzotriazoles. The rapid reaction times and mild conditions make this an attractive variation of the classical 'click' reaction of

  8. Biomolecular patterning of glass surfaces via strain-promoted cycloaddition of azides and cyclooctynes

    NARCIS (Netherlands)

    Wijdeven, M.A.; Nicosia, Carlo; Borrmann, A.; Huskens, Jurriaan; van Delft, F.L.

    2014-01-01

    Metal-free, strain-promoted alkyne–azide cycloaddition (SPAAC) is employed as a versatile technology for the modification of glass with biomolecules. Patterning is executed by stamping of a fluorogenic azidocoumarin or a cyclooctyne to the glass surface, to obtain a unique anchor point for

  9. Iridium-catalyzed cycloaddition of azides and 1-bromoalkynes at room temperature.

    Science.gov (United States)

    Rasolofonjatovo, Evelia; Theeramunkong, Sewan; Bouriaud, Alexandra; Kolodych, Sergii; Chaumontet, Manon; Taran, Frédéric

    2013-09-20

    Iridium dimer complexes were found to catalyze the [3 + 2] cycloaddition reaction of azides with bromoalkynes, yielding 1,5-disubstituted 4-bromo-1,2,3-triazoles in reasonable to excellent yields under mild conditions. The reaction offers a direct route to new 1,4,5-trisubstituted triazoles.

  10. Synthesis of Functionalized Aliphatic Polyesters by the ``Click'' Copper-Catalyzed Alkyne—Azide Cycloaddition

    Science.gov (United States)

    Lecomte, Philippe; Riva, Raphael; Jerome, Christine

    The functionalization of aliphatic polyesters by the copper-mediated azide—alkyne Huisgen's cycloaddition is very efficient under mild conditions, which prevents degradation from occurring. The implementation of this reaction requires the synthesis of aliphatic polyesters bearing pendant alkynes and azides, which can be carried out either by polycondensation or by ring-opening polymerization.

  11. Phosphoramidite accelerated copper(I)-catalyzed [3+2] cycloadditions of azides and alkynes

    NARCIS (Netherlands)

    Campbell-Verduyn, Lachlan S.; Mirfeizi, Leila; Dierckx, Rudi A.; Elsinga, Philip H.; Feringa, Ben L.

    2009-01-01

    Monodentate phosphoramidite ligands are used to accelerate the copper(I)-catalyzed 1,3-dipolar cycloaddition of azides and alkynes (CuAAC) rapidly yielding a wide variety of functionalized 1,4-disubstituted-1,2,3-triazoles; Cu(I) and Cu(II) salts both function as the copper source in aqueous

  12. Solvent-free one-pot 1,3-dipolar cycloaddition reactions of ...

    Indian Academy of Sciences (India)

    esting part is 1,3-dipolar cycloaddition, which repre- sents one of the most versatile tools for the construction of five-membered heterocycles. Owing to the labile na- ... (300 MHz, FT NMR) using TMS as internal standard. 13C NMR spectra were recorded on the same instrument at 75MHz. The coupling constants (J) are given ...

  13. One-Pot Functionalization of Graphene with Porphyrin through Cycloaddition Reactions

    NARCIS (Netherlands)

    Zhang, Xiaoyan; Hou, Lili; Cnossen, Arjen; Coleman, Anthony C.; Ivashenko, Oleksii; Rudolf, Petra; Wees, Bart J. van; Browne, Wesley R.; Feringa, Ben L.

    Two types of graphene-based hybrid materials, graphene-TPP (TPP=tetraphenylporphyrin) and graphene-PdTPP (PdTPP=palladium tetraphenylporphyrin), were prepared directly from pristine graphene through one-pot cycloaddition reactions. The hybrid materials were characterized by thermogravimetric

  14. 6-Alkynylpurines bearing electronacceptor substituents: Preparation, reactivity in cycloaddition reactions and cytostatic activity

    Czech Academy of Sciences Publication Activity Database

    Křováček, M.; Dvořáková, H.; Votruba, Ivan; Císařová, I.; Dvořák, D.

    2011-01-01

    Roč. 76, č. 12 (2011), s. 1487-1507 ISSN 0010-0765 Grant - others:GA ČR(CZ) GA203/09/1552; GA MŠk(CZ) LC06070 Program:LC Institutional research plan: CEZ:AV0Z40550506 Keywords : alkynylpurines * cytotoxicity * cycloaddition reactions Subject RIV: CC - Organic Chemistry Impact factor: 1.283, year: 2011

  15. Synthesis and Diels–Alder cycloaddition reaction of norbornadiene and benzonorbornadiene dimers

    Directory of Open Access Journals (Sweden)

    Bilal Nişancı

    2009-08-01

    Full Text Available Dimeric forms of norbornadiene and benzonorbornadiene were synthesized starting with known monobromide derivatives. The Diels–Alder cycloaddition reaction of dimers with TCNE and PTAD was investigated and new norbornenoid polycyclics were obtained. All compounds were characterized properly using NMR spectroscopy.

  16. Cycloadditions to Epoxides Catalyzed by GroupIII-V Transition-Metal Complexes

    KAUST Repository

    D'Elia, Valerio

    2015-05-25

    Complexes of groupIII-V transition metals are gaining increasing importance as Lewis acid catalysts for the cycloaddition of dipolarophiles to epoxides. This review examines the latest reports, including homogeneous and heterogeneous applications. The pivotal step for the cycloaddition reactions is the ring opening of the epoxide following activation by the Lewis acid. Two modes of cleavage (C-C versus C-O) have been identified depending primarily on the substitution pattern of the epoxide, with lesser influence observed from the Lewis acid employed. The widely studied cycloaddition of CO2 to epoxides to afford cyclic carbonates (C-O bond cleavage) has been scrutinized in terms of catalytic efficiency and reaction mechanism, showing that unsophisticated complexes of groupIII-V transition metals are excellent molecular catalysts. These metals have been incorporated, as well, in highly performing, recyclable heterogeneous catalysts. Cycloadditions to epoxides with other dipolarophiles (alkynes, imines, indoles) have been conducted with scandium triflate with remarkable performances (C-C bond cleavage). © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Copper on Chitosan: A Recyclable Heterogeneous Catalyst for Azide-alkyne Cycloaddition Reactions in Water

    Science.gov (United States)

    Copper sulfate is immobilized over chitosan by simply stirring an aqueous suspension of chitosan in water with copper sulfate; the ensuing catalyst has been utilized for the azide-alkyne cycloaddition in aqueous media and it can be recycled and reused many time without loosing it...

  18. A Palladium-Catalyzed Vinylcyclopropane (3 + 2) Cycloaddition Approach to the Melodinus Alkaloids

    KAUST Repository

    Goldberg, Alexander F. G.

    2011-08-19

    A palladium-catalyzed (3+2) cycloaddition of a vinylcyclopropane and a β-nitrostyrene is employed to rapidly assemble the cyclopentane core of the Melodinus alkaloids. The ABCD ring system of the natural product family is prepared in six steps from commercially available materials.

  19. Pressure-accelerated azide-alkyne cycloaddition: micro capillary versus autoclave reactor performance.

    Science.gov (United States)

    Borukhova, Svetlana; Seeger, Andreas D; Noël, Timothy; Wang, Qi; Busch, Markus; Hessel, Volker

    2015-02-01

    Pressure effects on regioselectivity and yield of cycloaddition reactions have been shown to exist. Nevertheless, high pressure synthetic applications with subsequent benefits in the production of natural products are limited by the general availability of the equipment. In addition, the virtues and limitations of microflow equipment under standard conditions are well established. Herein, we apply novel-process-window (NPWs) principles, such as intensification of intrinsic kinetics of a reaction using high temperature, pressure, and concentration, on azide-alkyne cycloaddition towards synthesis of Rufinamide precursor. We applied three main activation methods (i.e., uncatalyzed batch, uncatalyzed flow, and catalyzed flow) on uncatalyzed and catalyzed azide-alkyne cycloaddition. We compare the performance of two reactors, a specialized autoclave batch reactor for high-pressure operation up to 1800 bar and a capillary flow reactor (up to 400 bar). A differentiated and comprehensive picture is given for the two reactors and the three methods of activation. Reaction speedup and consequent increases in space-time yields is achieved, while the process window for favorable operation to selectively produce Rufinamide precursor in good yields is widened. The best conditions thus determined are applied to several azide-alkyne cycloadditions to widen the scope of the presented methodology. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Cycloadditions in mixed aqueous solvents : the role of the water concentration

    NARCIS (Netherlands)

    Rispens, Theo; Engberts, Jan B. F. N.

    We examined the kinetics of a series of cycloaddition reactions in mixtures of water with methanol, acetonitrile and poly(ethylene glycol) (MW 1000). The reactions include the Diels-Alder (DA) reaction between cyclopentadiene and N-n-butylmaleimide or acridizinium bromide, the retro-Diels-Alder

  1. DFT study on the mechanism of InBr3-catalyzed [2+2] cycloaddition ...

    Indian Academy of Sciences (India)

    chemsci

    Abstract. Density functional theory calculations at the M06-2X level were done to study the reaction mech- anism and regioselectivity for the [2+2] cycloaddition of allyltrimethylsilane with alkynones using InBr3 as the catalyst. The solvent effect was described by the single-point calculations with SMD model in 1,2-.

  2. Reactions of carbonyl compounds with α,β-unsaturated nitriles as a convenient pathway to carbo- and heterocycles

    International Nuclear Information System (INIS)

    Sharanin, Yu A; Goncharenko, M P; Litvinov, Victor P

    1998-01-01

    Published data on the methods for synthesis of carbo- and heterocyclic compounds based on reactions of α,β-unsaturated nitriles with carbonyl compounds and activated phenols are surveyed. It is demonstrated that all these reactions occur via nucleophilic addition of the carbanion generated from a carbonyl compound to the double bond of an unsaturated nitrile (the Michael reaction). The main routes of transformation of the adducts into carbo- and heterocyclic compounds are considered. The methods for regioselective preparation of fused 4H-pyrans or 1,4-dihydropyridines by varying conditions of cyclisation of Michael adducts are discussed. The bibliography includes 249 references.

  3. Permeability test and fuzzy orthogonal analysis of hydrogenated nitrile O-ring

    Directory of Open Access Journals (Sweden)

    Qin Hu

    2015-03-01

    Full Text Available In the high temperature, high pressure and high corrosive environment of the oil and gas drilling downhole, the weatherability of rubber sealing material has a great influence on the production safety. In order to study the important degree of every key environmental factor in downhole influencing the sealing performance of rubber sealing material, a new device of simulating downhole environment is designed to test the permeability of O-ring. The sample is hydrogenated nitrile O-ring and orthogonal experiment method is used to do nine tests by getting three levels from temperature, pressure and CO2 volume fraction. Test adopts fuzzy orthogonal method to analyze the main effects and the interaction between two factors, taking tensile strength, diameter variety rate and pH value of indicator as evaluation index. The results show that: the environmental factor influencing the sealing performance of hydrogenated nitrile O-ring from high to low by turns is temperature, pressure and CO2 volume fraction, while the interaction between temperature and pressure is the most significant. It provides a new way to study the influence of downhole complex environment on the performance of rubber sealing material. Moreover, the results have important reference value to further study the failure mechanism of rubber sealing ring in many environmental factors and the rational use in engineering.

  4. Synthetic transformations of a pendant nitrile moiety in group 4 metallocene complexes.

    Science.gov (United States)

    Pinkas, Jiří; Císařová, Ivana; Kubišta, Jiří; Horáček, Michal; Lamač, Martin

    2013-05-21

    Functional group transformations at the group 4 metallocene framework have been demonstrated, which have provided relatively straightforward access to otherwise synthetically challenging derivatives. The pendant nitrile group in Ti and Zr metallocene complexes of the type [(η(5)-C5Me5)(η(5)-C5H4CMe2CH2CN)MCl2] was converted into an intramolecularly bound ketimido moiety by alkylation, which took place not only at the nitrile, but also at the metal centre. The choice of an alkylating reagent (alkyl/aryl lithium, Grignard reagent) was crucial: e.g., 2 equiv. of MeMgBr effected the alkylation only at the metal, yielding selectively complexes [(η(5)-C5Me5)(η(5)-C5H4CMe2CH2CN)MMe2], while the use of PhMgBr, PhLi, or MeLi instead gave selectively the ketimido complexes. Organyl lithium reagents were, however, not compatible with the titanocene derivatives. The metal-bound ketimides were subsequently cleaved off by the reaction with HCl, which afforded metallocene dichlorides with a pendant imino group. These compounds were easily protonated again at the nitrogen atom to produce a cationic iminium moiety. Aqueous hydrolysis of the imine or its respective hydrochloride proved to be viable in the case of Zr and it finally afforded a pendant ketone group attached to the zirconocene framework.

  5. Pengaruh penggunaan nitril butadiene rubber dan pale crepe pada pembuatan sol karet untuk sepatu pengaman

    Directory of Open Access Journals (Sweden)

    Arum Yuniari

    2010-06-01

    Full Text Available Abstract Rubber sole for safety shoes was different on physical specification with general sole, especially on abrasion resistance and oil resistance. The objective of the study was to determine the effect of nitril butadiene rubber and pale crepe on physical properties of vulcanized rubber sole for safety shoes. Rubber sole for safety shoes was produced by blending pale crepe and nitril butadiene rubber with ratio of : 50/50; 60/40; 70/30 and 80/20 phr, respectively. Carbon black as filler was also variated with, 40 ; 50 and 60 phr. Compounding processing used two roll mill machine and vulcanized rubber sole was by using pressed use hydraulic press machine. The results showed that vulcanized rubber sole for safety shoes with good quality consist of pale crepe and NBR 80/20 phr and carbon black 40 phr, which was characterized by tensile strength 16.81 N/mm2, tear strength 11.68 N/mm, density 1.12 g/cm3, abrasion resistance 58.51 mm3, hardness 71.60 shore A, resistance to cut growth 30.000 times was 1.15 mm and oil resistance 65.44%, respectively. The quality parameters was complied with standard quality of SNI 0111 : 2009, for safety shoes from leather and vulcanized rubber sole that fulfill oil reistance parameter.

  6. Phosphine-catalyzed [3 + 2] cycloaddition of Morita-Baylis-Hillman carbonates with sulfamate-derived cyclic imines.

    Science.gov (United States)

    Zhang, Lei; Yu, Hao; Yang, Zhilin; Liu, Honglei; Li, Zhen; Guo, Junhong; Xiao, Yumei; Guo, Hongchao

    2013-12-21

    Phosphine-catalyzed [3 + 2] cycloaddition of Morita-Baylis-Hillman carbonates with sulfamate-derived cyclic imines has been developed, affording sulfamate-fused dihydropyrroles in moderate to good yields.

  7. D-π-A Compounds with Tunable Intramolecular Charge Transfer Achieved by Incorporation of Butenolide Nitriles as Acceptor Moieties

    DEFF Research Database (Denmark)

    Moreno-Yruela, Carlos; Garín, Javier; Orduna, Jesús

    2015-01-01

    Chromophores where a polyenic spacer separates a 4H-pyranylidene or benzothiazolylidene donor and three different butenolide nitriles have been synthesized and characterized. The role of 2(5H)-furanones as acceptor units on the polarization and the second-order nonlinear (NLO) properties has been...

  8. Expression control of nitrile hydratase and amidase genes in Rhodococcus erythropolis and substrate specificities of the enzymes

    Czech Academy of Sciences Publication Activity Database

    Rucká, Lenka; Volkova, Olga; Pavlík, Adam; Kaplan, Ondřej; Kracík, M.; Nešvera, Jan; Martínková, Ludmila; Pátek, Miroslav

    2014-01-01

    Roč. 105, č. 6 (2014), s. 1179-1190 ISSN 0003-6072 R&D Projects: GA MŠk(CZ) LC06010; GA ČR(CZ) GAP504/11/0394 Institutional support: RVO:61388971 Keywords : Rhodococcus erythropolis * Amidase * Nitrile hydratase Subject RIV: EE - Microbiology, Virology Impact factor: 1.806, year: 2014

  9. Purification and characterization of a novel nitrilase of Rhodococcus rhodochrous K22 that acts on aliphatic nitriles.

    Science.gov (United States)

    Kobayashi, M; Yanaka, N; Nagasawa, T; Yamada, H

    1990-01-01

    A novel nitrilase that preferentially catalyzes the hydrolysis of aliphatic nitriles to the corresponding carboxylic acids and ammonia was found in the cells of a facultative crotononitrile-utilizing actinomycete isolated from soil. The strain was taxonomically studied and identified as Rhodococcus rhodochrous. The nitrilase was purified, with 9.08% overall recovery, through five steps from a cell extract of the stain. After the last step, the purified enzyme appeared to be homogeneous, as judged by polyacrylamide gel electrophoresis, analytical centrifugation, and double immunodiffusion in agarose. The relative molecular weight values for the native enzyme, estimated from the ultracentrifugal equilibrium and by high-performance liquid chromatography, were approximately 604,000 +/- 30,000 and 650,000, respectively, and the enzyme consisted of 15 to 16 subunits identical in molecular weight (41,000). The enzyme acted on aliphatic olefinic nitriles such as crotononitrile and acrylonitrile as the most suitable substrates. The apparent Km values for crotononitrile and acrylonitrile were 18.9 and 1.14 mM, respectively. The nitrilase also catalyzed the direct hydrolysis of saturated aliphatic nitriles, such as valeronitrile, 4-chlorobutyronitrile, and glutaronitrile, to the corresponding acids without the formation of amide intermediates. Hence, the R. rhodochrous K22 nitrilase is a new type distinct from all other nitrilases that act on aromatic and related nitriles. Images PMID:2394676

  10. Biotransformation of 3-substituted methyl (R,S)-4-cyanobutanoates with nitrile- and amide-converting biocatalysts

    Czech Academy of Sciences Publication Activity Database

    Martínková, Ludmila; Klempier, N.; Bardakji, J.; Kandelbauer, A.; Ovesná, M.; Podařilová, T.; Kuzma, Marek; Přepechalová, Irena; Griengl, G.; Křen, Vladimír

    2001-01-01

    Roč. 14, - (2001), s. 95-99 ISSN 1381-1177 R&D Projects: GA AV ČR IAA4020802 Institutional research plan: CEZ:AV0Z5020903 Keywords : Rhodococcus equi * nitrile hydratase * amidase Subject RIV: EE - Microbiology, Virology Impact factor: 1.408, year: 2001

  11. High-yield continuous production of nicotinic acid via nitrile hydratase–amidase cascade reactions using cascade CSMRs

    Czech Academy of Sciences Publication Activity Database

    Cantarella, L.; Gallifuoco, A.; Malandra, A.; Martínková, Ludmila; Spera, A.; Cantarella, M.

    2011-01-01

    Roč. 48, 4-5 (2011), 345-350 ISSN 0141-0229 R&D Projects: GA MŠk OC09046 Institutional research plan: CEZ:AV0Z50200510 Keywords : Nitrile hydratase-amidase cascade system * 3-Cyanopyridine bioconversion * Nicotinic acid Subject RIV: EE - Microbiology, Virology Impact factor: 2.367, year: 2011

  12. Stereochemically rich pentaketides from bis(isoxazolines): a general strategy for efficient polyketide synthesis.

    Science.gov (United States)

    Fader, Lee D; Carreira, Erick M

    2004-07-08

    [reaction: see text] A strategy based on diastereoselective dipolar cycloaddition reaction of nitrile oxides and allylic alcoholates has been applied to the synthesis of bis(isoxazolines) that are precursors to polyketide fragments. These intermediates can be elaborated into protected polyols by chemoselective reductive opening of each isoxazoline sequentially or, alternatively, both simultaneously, potentially providing access to all stereoisomers of this carbon skeleton.

  13. Ruthenium(II)-Catalyzed Redox-Free [3 + 2] Cycloaddition of N-Sulfonyl Aromatic Aldimines with Maleimides.

    Science.gov (United States)

    Tamizmani, Masilamani; Ramesh, Balu; Jeganmohan, Masilamani

    2018-03-13

    A ruthenium(II)-catalyzed redox-free cycloaddition of N-sulfonyl aromatic aldimines with maleimides providing 1-aminoindanes in good yields is described. Usually, maleimides reacted with substituted aromatics, affording the Michael-type ortho alkylated aromatics or 1,1-type cyclized spirosuccinimides. In the present reaction, maleimides provided 1,2-type cycloaddition products. The proposed mechanism was strongly supported by the DFT calculations and isolation of a ruthenacycle intermediate.

  14. Expansion of ribosomally produced natural products: a nitrile hydratase- and Nif11-related precursor family

    Directory of Open Access Journals (Sweden)

    Mitchell Douglas A

    2010-05-01

    Full Text Available Abstract Background A new family of natural products has been described in which cysteine, serine and threonine from ribosomally-produced peptides are converted to thiazoles, oxazoles and methyloxazoles, respectively. These metabolites and their biosynthetic gene clusters are now referred to as thiazole/oxazole-modified microcins (TOMM. As exemplified by microcin B17 and streptolysin S, TOMM precursors contain an N-terminal leader sequence and C-terminal core peptide. The leader sequence contains binding sites for the posttranslational modifying enzymes which subsequently act upon the core peptide. TOMM peptides are small and highly variable, frequently missed by gene-finders and occasionally situated far from the thiazole/oxazole forming genes. Thus, locating a substrate for a particular TOMM pathway can be a challenging endeavor. Results Examination of candidate TOMM precursors has revealed a subclass with an uncharacteristically long leader sequence closely related to the enzyme nitrile hydratase. Members of this nitrile hydratase leader peptide (NHLP family lack the metal-binding residues required for catalysis. Instead, NHLP sequences display the classic Gly-Gly cleavage motif and have C-terminal regions rich in heterocyclizable residues. The NHLP family exhibits a correlated species distribution and local clustering with an ABC transport system. This study also provides evidence that a separate family, annotated as Nif11 nitrogen-fixing proteins, can serve as natural product precursors (N11P, but not always of the TOMM variety. Indeed, a number of cyanobacterial genomes show extensive N11P paralogous expansion, such as Nostoc, Prochlorococcus and Cyanothece, which replace the TOMM cluster with lanthionine biosynthetic machinery. Conclusions This study has united numerous TOMM gene clusters with their cognate substrates. These results suggest that two large protein families, the nitrile hydratases and Nif11, have been retailored for

  15. Transfer efficiency of Staphylococcus aureus between nitrile exam gloves and nonporous fomites.

    Science.gov (United States)

    Koenig, David W; Korir-Morrison, Cindy; Hoffman, Douglas R

    2016-02-01

    This report describes fomite transmission of Staphylococcus aureus amongst various surfaces. A contact transfer protocol was completed to evaluate the movement of S aureus between a person wearing nitrile gloves and either: handshaking with another person with gloved hands, touching a plastic cellular telephone back, or touching a stainless steel rod. The data in this preliminary study imply that the highest bacterial transfer is with metal surfaces followed by plastic. Interestingly, glove-to-glove transfer occurred but transfered less bacteria than a plastic or metal surface. The observations from this study point to the need to clearly define hygiene behaviors to reduce the potential of hand- and surface-mediated transmission. Copyright © 2016 Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved.

  16. Surface modification of polyacrylonitrile fibre by nitrile hydratase from Corynebacterium nitrilophilus.

    Science.gov (United States)

    Chen, Sheng; Gao, Huihui; Chen, Jian; Wu, Jing

    2014-11-01

    Previously, nitrile hydratase (NHase) from Corynebacterium nitrilophilus was obtained and showed potential in polyacrylonitrile (PAN) fibre modification. In the present study, the modification conditions of C. nitrilophilus NHase on PAN were investigated. In the optimal conditions, the wettability and dyeability (anionic and reactive dyes) of PAN treated by C. nitrilophilus NHase reached a similar level of those treated by alkali. In addition, the chemical composition and microscopically observable were changed in the PAN surface after NHase treatment. Meanwhile, it revealed that cutinase combined with NHase facilitates the PAN hydrolysis slightly because of the ester existed in PAN as co-monomer was hydrolyzed. All these results demonstrated that C. nitrilophilus NHase can modify PAN efficiently without textile structure damage, and this study provides a foundation for the further application of C. nitrilophilus NHase in PAN modification industry.

  17. Application of protective coatings from ultrahigh-molecular weight polyethylene to butadiene-nitrile rubber

    Science.gov (United States)

    Dyakonov, A. A.; Sokolova, M. D.; Shadrinov, N. V.; Sleptsova, S. A.

    2017-12-01

    The paper presents a method of applying a protective coating from ultrahigh molecular weight polyethylene to rubber products. A distinctive feature of the presented method is the prevulcanization of a rubber compound in order to form it into the desired shape and remove an excess rubber material. The application of an ultrahigh molecular weight polyethylene powder to the prepared surface ensures a uniform coating thickness. To achieve an optimal combination of rubber properties, we study how the scorch time affects its physical and mechanical properties, hardness, corrosion, abrasion and thermal resistance. We find the scorch time range in which a spatial elastomeric network forms that influences the penetration of ultrahigh molecular weight polyethylene into butadiene-nitrile rubber.

  18. The Nitrile-Forming Enzyme 7-Cyano-7-Deazaguanine Synthase from Geobacillus kaustophilus: A Reverse Nitrilase?

    Science.gov (United States)

    Winkler, Margit; Dokulil, Katharina; Weber, Hansjörg; Pavkov-Keller, Tea; Wilding, Birgit

    2015-11-02

    7-Cyano-7-deazaguanine synthase (E.C. 6.3.4.20) is an enzyme that catalyzes the formation of a nitrile from a carboxylic acid and ammonia at the expense of ATP. The protein from G. kaustophilus was heterologously expressed, and its biochemical characteristics were explored by using a newly developed HPLC-MS based assay, (31) P NMR, and a fluorescence-based thermal-shift assay. The protein showed the expected high thermostability, had a pH optimum at pH 9.5, and an apparent temperature optimum at 60 °C. We observed strict substrate specificity of QueC for the natural substrate 7-carboxy-7-deazaguanine, and determined AMP and pyrophosphate as co-products of preQ0. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Menthols as Chiral Auxiliaries for Asymmetric Cycloadditive Oligomerization: Syntheses and Studies of β-Proline Hexamers.

    Science.gov (United States)

    Kudryavtsev, Konstantin V; Ivantcova, Polina M; Muhle-Goll, Claudia; Churakov, Andrei V; Sokolov, Mikhail N; Dyuba, Artem V; Arutyunyan, Alexander M; Howard, Judith A K; Yu, Chia-Chun; Guh, Jih-Hwa; Zefirov, Nikolay S; Bräse, Stefan

    2015-12-18

    To produce a novel class of structurally ordered poly-β-prolines, an emergent method for synthesizing chiral β-peptide molecular frameworks was developed based on 1,3-dipolar cycloaddition chemistry of azomethine ylides. Functionalized short β-peptides with up to six monomeric residues were efficiently synthesized in homochiral forms using a cycloadditive oligomerization approach. X-ray, NMR, and CD structural analyses of the novel β-peptides revealed secondary structure features that were generated primarily by Z/E-β-peptide bond isomerism. Anticancer in cellulo activity of the new β-peptides toward hormone-refractory prostate cancer cells was observed and was dependent on the absolute configuration of the stereogenic centers and the chain length of the β-proline oligomers.

  20. Investigation of the Pyridinium Ylide—Alkyne Cycloaddition as a Fluorogenic Coupling Reaction

    Directory of Open Access Journals (Sweden)

    Simon Bonte

    2016-03-01

    Full Text Available The cycloaddition of pyridinium ylides with alkynes was investigated under mild conditions. A series of 13 pyridinium salts was prepared by alkylation of 4-substituted pyridines. Their reactivity with propiolic ester or amide in various reaction conditions (different temperatures, solvents, added bases was studied, and 11 indolizines, with three points of structural variation, were, thus, isolated and characterized. The highest yields were obtained when electron-withdrawing groups were present on both the pyridinium ylide, generated in situ from the corresponding pyridinium salt, and the alkyne (X, Z = ester, amide, CN, carbonyl, etc.. Electron-withdrawing substituents, lowering the acid dissociation constant (pKa of the pyridinium salts, allow the cycloaddition to proceed at pH 7.5 in aqueous buffers at room temperature.

  1. Spectra, Index of Refraction, and Optical Constants of Nitrile Ices Relevant to Titan's Atmosphere

    Science.gov (United States)

    Moore, Marla; Hudson, Reggie; Ferrante, Robert; Moore, William

    Spectra and optical constants of nitrile ices known or suspected to be in Titan's atmosphere are presented from 2.5 to 200 microns (4000 to 50 cm-1 ). These results are relevant to the ongoing modeling of Cassini CIRS observations of Titan's winter pole. Ices studied include: HCN, hydrogen cyanide; C2 N2 , cyanogen; CH3 CN, acetonitrile; C2 H5 CN, propionitrile; and HC3 N, cyanoacetylene. For each of these molecules we report new measurements of the index of refraction, n, determined in both the amorphous-and crystalline-phase at 670 nm. Spectra were measured and optical constants were calculated for each nitrile at a variety of temperatures including 20, 35, 50, 75, 95, and 110 K, in the amorphous-and crystalline-phase. This laboratory effort uses a dedicated FTIR spectrometer to record transmission spectra of thin-film ice samples. Laser interference is used to measure film thickness during condensation onto a transparent cold window attached to the tail section of a closed-cycle helium cryo-stat. Optical constants, real (n) and imaginary (k) refractive indices, are determined using Kramers-Kronig (K-K) analysis. Our calculation reproduces the complete spectrum, including all interference effects. Index of refraction measurements are made in a separate dedicated FTIR spectrometer where interference deposit fringes are measured using two 670 nm lasers at different angles to the ice substrate. A survey of these new measurements will be presented along with a discussion of their validation, errors, and application to Titan data. We acknowledge Mark Loeffler who recently joined in our refractive index measurements. The authors also acknowledge support from the Cassini Data Analysis Program. RLH and MHM acknowledge additional funding from NASA's PGG and Outer Planets Programs, and the Goddard Center for Astrobiology.

  2. Intramolecular Azide to Alkene Cycloadditions for the Construction of Pyrrolobenzodiazepines and Azetidino-Benzodiazepines

    Directory of Open Access Journals (Sweden)

    Karl Hemming

    2014-10-01

    Full Text Available The coupling of proline- and azetidinone-substituted alkenes to 2-azidobenzoic and 2-azidobenzenesulfonic acid gives precursors that undergo intramolecular azide to alkene 1,3-dipolar cycloadditions to give imine-, triazoline- or aziridine-containing pyrrolo[1,4]benzodiazepines (PBDs, pyrrolo[1,2,5]benzothiadiazepines (PBTDs, and azetidino[1,4]benzodiazepines. The imines and aziridines are formed after loss of nitrogen from a triazoline cycloadduct. The PBDs are a potent class of antitumour antibiotics.

  3. Synthesis of pyrrolizidine alkaloids via 1,3-dipolar cycloaddition involving cyclic nitrones and unsaturated lactones.

    Science.gov (United States)

    Stecko, Sebastian; Jurczak, Margarita; Urbańczyk-Lipkowska, Zofia; Solecka, Jolanta; Chmielewski, Marek

    2008-09-08

    The 1,3-dipolar cycloaddition of cyclic nitrone derived from tartaric acid and (S)-5-hydroxymethyl-2(5H)-furanone leads to a single adduct which was transformed into 2,6-dihydroxyhastanecine via reaction sequence involving reduction of the lactone moiety, glycolic cleavage of the terminal diol, and the N-O hydrogenolysis followed by the intramolecular alkylation of the nitrogen atom.

  4. A facile regioselective synthesis of novel spiroacenaphthene pyrroloisoquinolines through 1,3-dipolar cycloaddition reactions

    Energy Technology Data Exchange (ETDEWEB)

    Sarrafi, Yaghoub; Asghari, Asieh; Sadatshahabi, Marzieh, E-mail: ysarrafi@umz.ac.ir [Department of Organic Chemistry, Faculty of Chemistry, University of Mazandaran (Iran, Islamic Republic of); Hamzehloueian, Mahshid [Department of Chemistry, Jouybar Branch, Islamic Azad University, Jouybar (Iran, Islamic Republic of); Alimohammadi, Kamal [Department of Chemistry, Dr. Shariati Branch, University of Farhangian, Sari (Iran, Islamic Republic of)

    2013-12-01

    An efficient one-pot three-component procedure for the synthesis of novel spiroacenaphthene pyrroloisoquinolines with high regioselectivity is described. These compounds were prepared from 1,3-dipolar cycloaddition of an azomethine ylide generated from acenaphthenequinone and 1,2,3,4-tetrahydroisoquinoline via [1,5]-H shift, with chalcone and nitrostyrene derivatives as dipolarophiles. The structure and stereochemistry of the cycloadducts have been established by single crystal X-ray structure and spectroscopic techniques. (author)

  5. Mechanistic rationalization of unusual sigmoidal kinetic profiles in the Machetti-De Sarlo cycloaddition reaction.

    Science.gov (United States)

    Mower, Matthew P; Blackmond, Donna G

    2015-02-18

    Unusual sigmoidal kinetic profiles in the Machetti-De Sarlo base-catalyzed 1,3-dipolar cycloaddition of acrylamide to N-methylnitroacetamide are rationalized by detailed in situ kinetic analysis. A dual role is uncovered in which a substrate acts as a precursor to catalyze its own reaction. Such kinetic studies provide a general protocol for distinguishing among different mechanistic origins of induction periods in complex organic reactions.

  6. The Use of Nitrone Cycloadditions in the Synthesis of Beta-Amino Aldehydes and Unsaturated Amines.

    Science.gov (United States)

    1986-01-01

    8217-’ OMe 25 26 Me - H NH 2 22 , **o.° 12 prepared by the Mannich reaction or one of its modern variants.’ s However, the Nannich reaction in efficient...product mixtures. The nitrone strategy is clearly advantagous to the Mannich reaction for the prepartion of these systems. More recent results from...with alkenes (dipolarophiles) to produce isoxazolidines (2) in a fashion similar to the (4+2] Diels-Alder reaction .’ The cycloaddition results in

  7. 1,3-Dipolar Cycloaddition Reactions of Substituted Benzyl Azides with Acetylenic Compounds

    Directory of Open Access Journals (Sweden)

    Sultan T. Abu-Orabi

    2002-02-01

    Full Text Available We review in this article some of our work which has been published over the last fifteen years in the area of 1,3-dipolar cycloaddition reactions of substituted benzyl azides with acetylenic compounds to form the corresponding 1,2-3-triazoles. Several triazole derivatives were transformed into triazolopyridazine and triazolo-1,3,4-oxadiazole derivatives upon their reactions with hydrazine.

  8. Unusual differences in the reactivity of glutamic and aspartic acid in oxidative decarboxylation reactions

    NARCIS (Netherlands)

    But, Andrada; Wijst, van der Evie; Notre, le Jerome; Wever, Ron; Sanders, Johan P.M.; Bitter, Johannes H.; Scott, Elinor L.

    2017-01-01

    Amino acids are potential substrates to replace fossil feedstocks for the synthesis of nitriles via oxidative decarboxylation using vanadium chloroperoxidase (VCPO), H2O2 and bromide. Here the conversion of glutamic acid (Glu) and aspartic acid (Asp) was investigated. It was

  9. Experimental Investigation on the Mechanism of Chelation-Assisted, Copper(II) Acetate-Accelerated Azide-Alkyne Cycloaddition

    Science.gov (United States)

    Kuang, Gui-Chao; Guha, Pampa M.; Brotherton, Wendy S.; Simmons, J. Tyler; Stankee, Lisa A.; Nguyen, Brian T.; Clark, Ronald J.; Zhu, Lei

    2011-01-01

    A mechanistic model is formulated to account for the high reactivity of chelating azides (organic azides capable of chelation-assisted metal coordination at the alkylated azido nitrogen position) and copper(II) acetate (Cu(OAc)2) in copper(II)-mediated azide-alkyne cycloaddition (AAC) reactions. Fluorescence and 1H NMR assays are developed for monitoring the reaction progress in two different solvents – methanol and acetonitrile. Solvent kinetic isotopic effect and pre-mixing experiments give credence to the proposed different induction reactions for converting copper(II) to catalytic copper(I) species in methanol (methanol oxidation) and acetonitrile (alkyne oxidative homocoupling), respectively. The kinetic orders of individual components in a chelation-assisted, copper(II)-accelerated AAC reaction are determined in both methanol and acetonitrile. Key conclusions resulting from the kinetic studies include (1) the interaction between copper ion (either in +1 or +2 oxidation state) and a chelating azide occurs in a fast, pre-equilibrium step prior to the formation of the in-cycle copper(I)-acetylide, (2) alkyne deprotonation is involved in several kinetically significant steps, and (3) consistent with prior experimental and computational results by other groups, two copper centers are involved in the catalysis. The X-ray crystal structures of chelating azides with Cu(OAc)2 suggest a mechanistic synergy between alkyne oxidative homocoupling and copper(II)-accelerated AAC reactions, in which both a bimetallic catalytic pathway and a base are involved. The different roles of the two copper centers (a Lewis acid to enhance the electrophilicity of the azido group and a two-electron reducing agent in oxidative metallacycle formation, respectively) in the proposed catalytic cycle suggest that a mixed valency (+2 and +1) dinuclear copper species be a highly efficient catalyst. This proposition is supported by the higher activity of the partially reduced Cu(OAc)2 in

  10. Preparation and characterization of electrospun poly(phthalazinone ether nitrile ketone) membrane with novel thermally stable properties

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Gang; Zhang, Hao; Qian, Bingqing [Carbon Research Laboratory, Liaoning Key Lab for Energy Materials and Chemical Engineering, State Key Lab of Fine Chemicals, Dalian University of Technology, Dalian 116024 (China); Wang, Jinyan, E-mail: wangjinyan@dlut.edu.cn [Department of Polymer Science and Materials, Dalian University of Technology, Dalian 116024 (China); Jian, Xigao [Department of Polymer Science and Materials, Dalian University of Technology, Dalian 116024 (China); Qiu, Jieshan, E-mail: jqiu@dlut.edu.cn [Carbon Research Laboratory, Liaoning Key Lab for Energy Materials and Chemical Engineering, State Key Lab of Fine Chemicals, Dalian University of Technology, Dalian 116024 (China)

    2015-10-01

    Highlights: • Poly (phthalazinone ether nitrile ketone) (PPENK) was used to successfully prepare nanofiber membranes by electrospinning. • Electrospun membrane exhibits a good thermostability. • Electrospun membrane. - Abstract: Electrospun nanofibrous membranes have several applications because of their excellent properties, such as high porosity, small fiber diameter, and large surface area. However, high-temperature resistant electrospun membranes remain a challenge because of the absence of precursors that offer spinnability, scalability, and superior thermal stability. In this study, poly(phthalazinone ether nitrile ketone) (PPENK) was used to successfully prepare nanofiber membranes by electrospinning. Electrospun PPENK membranes were characterized by scanning electron microscopy, differential scanning calorimetry, Fourier transform infrared spectroscopy, and tensile stress–strain tests. Results indicated that the prepared electrospun membranes had a very high glass transition temperature, superior chemical resistance, and excellent mechanical strength. These desirable properties broaden their potential application in membranes and treatment of various hot fluid streams without strict temperature control.

  11. Chiral Cu(II-catalyzed enantioselective β-borylation of α,β-unsaturated nitriles in water

    Directory of Open Access Journals (Sweden)

    Lei Zhu

    2015-10-01

    Full Text Available The promising performance of copper(II complexes was demonstrated for asymmetric boron conjugate addition to α,β-unsaturated nitriles in water. The catalyst system, which consisted of Cu(OAc2 and a chiral 2,2′-bipyridine ligand, enabled β-borylation and chiral induction in water. Subsequent protonation, which was accelerated in aqueous medium, led to high activity of this asymmetric catalysis. Both solid and liquid substrates were suitable despite being insoluble in water.

  12. Biosynthesis of the Nitrile Glucosides Rhodiocyanoside A and D and the Cyanogenic Glucosides Lotaustralin and Linamarin in Lotus japonicus1

    Science.gov (United States)

    Forslund, Karin; Morant, Marc; Jørgensen, Bodil; Olsen, Carl Erik; Asamizu, Erika; Sato, Shusei; Tabata, Satoshi; Bak, Søren

    2004-01-01

    Lotus japonicus was shown to contain the two nitrile glucosides rhodiocyanoside A and rhodiocyanoside D as well as the cyanogenic glucosides linamarin and lotaustralin. The content of cyanogenic and nitrile glucosides in L. japonicus depends on plant developmental stage and tissue. The cyanide potential is highest in young seedlings and in apical leaves of mature plants. Roots and seeds are acyanogenic. Biosynthetic studies using radioisotopes demonstrated that lotaustralin, rhodiocyanoside A, and rhodiocyanoside D are derived from the amino acid l-Ile, whereas linamarin is derived from Val. In silico homology searches identified two cytochromes P450 designated CYP79D3 and CYP79D4 in L. japonicus. The two cytochromes P450 are 94% identical at the amino acid level and both catalyze the conversion of Val and Ile to the corresponding aldoximes in biosynthesis of cyanogenic glucosides and nitrile glucosides in L. japonicus. CYP79D3 and CYP79D4 are differentially expressed. CYP79D3 is exclusively expressed in aerial parts and CYP79D4 in roots. Recombinantly expressed CYP79D3 and CYP79D4 in yeast cells showed higher catalytic efficiency with l-Ile as substrate than with l-Val, in agreement with lotaustralin and rhodiocyanoside A and D being the major cyanogenic and nitrile glucosides in L. japonicus. Ectopic expression of CYP79D2 from cassava (Manihot esculenta Crantz.) in L. japonicus resulted in a 5- to 20-fold increase of linamarin content, whereas the relative amounts of lotaustralin and rhodiocyanoside A/D were unaltered. PMID:15122013

  13. Biosynthesis of the nitrile glucosides rhodiocyanoside A and D and the cyanogenic glucosides lotaustralin and linamarin in Lotus japonicus.

    Science.gov (United States)

    Forslund, Karin; Morant, Marc; Jørgensen, Bodil; Olsen, Carl Erik; Asamizu, Erika; Sato, Shusei; Tabata, Satoshi; Bak, Søren

    2004-05-01

    Lotus japonicus was shown to contain the two nitrile glucosides rhodiocyanoside A and rhodiocyanoside D as well as the cyanogenic glucosides linamarin and lotaustralin. The content of cyanogenic and nitrile glucosides in L. japonicus depends on plant developmental stage and tissue. The cyanide potential is highest in young seedlings and in apical leaves of mature plants. Roots and seeds are acyanogenic. Biosynthetic studies using radioisotopes demonstrated that lotaustralin, rhodiocyanoside A, and rhodiocyanoside D are derived from the amino acid l-Ile, whereas linamarin is derived from Val. In silico homology searches identified two cytochromes P450 designated CYP79D3 and CYP79D4 in L. japonicus. The two cytochromes P450 are 94% identical at the amino acid level and both catalyze the conversion of Val and Ile to the corresponding aldoximes in biosynthesis of cyanogenic glucosides and nitrile glucosides in L. japonicus. CYP79D3 and CYP79D4 are differentially expressed. CYP79D3 is exclusively expressed in aerial parts and CYP79D4 in roots. Recombinantly expressed CYP79D3 and CYP79D4 in yeast cells showed higher catalytic efficiency with l-Ile as substrate than with l-Val, in agreement with lotaustralin and rhodiocyanoside A and D being the major cyanogenic and nitrile glucosides in L. japonicus. Ectopic expression of CYP79D2 from cassava (Manihot esculenta Crantz.) in L. japonicus resulted in a 5- to 20-fold increase of linamarin content, whereas the relative amounts of lotaustralin and rhodiocyanoside A/D were unaltered.

  14. Unsaturated thiolates and their analogs in cycloaddition reactions

    International Nuclear Information System (INIS)

    Lajshev, V.Z.; Petrov, M.L.; Petrov, A.A.

    1981-01-01

    Salts of 2-arylethinyltellurol are prepared by means of alkali metal arylacetylenides interaction with tellurium in the medium of dimethylsulfoxide. The treatment of the salts with ether solution of hydrogen chloride results in 2,4-di(n- R-benzyliden)-1,3-ditelluranes; in the case of water (or oxidation by iodine)-di(2-arylethinyl) tellurides. With carbon sulfide and dimethyl ether of acetylenedicarbonic acid 2-phenylethinyltellurolate of sodium inters in cyclization reaction. In this case, the products of nucleophylic addition are formed. Non-stable N, N-diethylamide of phenylthioacetic acid is the initial product of 2-phenylethinyltellurolate of sodium interaction with diethylamine [ru

  15. Selective N-alkylation of amines using nitriles under hydrogenation conditions: facile synthesis of secondary and tertiary amines.

    Science.gov (United States)

    Ikawa, Takashi; Fujita, Yuki; Mizusaki, Tomoteru; Betsuin, Sae; Takamatsu, Haruki; Maegawa, Tomohiro; Monguchi, Yasunari; Sajiki, Hironao

    2012-01-14

    Nitriles were found to be highly effective alkylating reagents for the selective N-alkylation of amines under catalytic hydrogenation conditions. For the aromatic primary amines, the corresponding secondary amines were selectively obtained under Pd/C-catalyzed hydrogenation conditions. Although the use of electron poor aromatic amines or bulky nitriles showed a lower reactivity toward the reductive alkylation, the addition of NH(4)OAc enhanced the reactivity to give secondary aromatic amines in good to excellent yields. Under the same reaction conditions, aromatic nitro compounds instead of the aromatic primary amines could be directly transformed into secondary amines via a domino reaction involving the one-pot hydrogenation of the nitro group and the reductive alkylation of the amines. While aliphatic amines were effectively converted to the corresponding tertiary amines under Pd/C-catalyzed conditions, Rh/C was a highly effective catalyst for the N-monoalkylation of aliphatic primary amines without over-alkylation to the tertiary amines. Furthermore, the combination of the Rh/C-catalyzed N-monoalkylation of the aliphatic primary amines and additional Pd/C-catalyzed alkylation of the resulting secondary aliphatic amines could selectively prepare aliphatic tertiary amines possessing three different alkyl groups. According to the mechanistic studies, it seems reasonable to conclude that nitriles were reduced to aldimines before the nucleophilic attack of the amine during the first step of the reaction.

  16. Nitrile-functionalized ruthenium nanoparticles: charge delocalization through Ru − N ≡ C interface

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Fengqi; Huang, Lin; Zou, Jiasui [South China University of Technology, New Energy Research Institute, School of Environment and Energy, Guangzhou Higher Education Mega Centre (China); Yan, Jinwu; Zhu, Jiaying [South China University of Technology, School of Bioscience and Bioengineering, Guangzhou Higher Education Mega Centre (China); Kang, Xiongwu, E-mail: esxkang@scut.edu.cn; Chen, Shaowei, E-mail: shaowei@ucsc.edu [South China University of Technology, New Energy Research Institute, School of Environment and Energy, Guangzhou Higher Education Mega Centre (China)

    2017-03-15

    Ruthenium nanoparticles (2.06 ± 0.46 nm in diameter) were stabilized by the self-assembly of nitrile molecules onto the ruthenium colloid surface by virtue of the formation of Ru−N≡C interfacial bonding linkages. Thermogravimetric analysis showed that there were about 63 nitrile ligands per nanoparticle, corresponding to an average molecular footprint of 22.4 Å{sup 2}. Proton nuclear magnetic resonance (NMR) studies suggested an end-on configuration of the nitrile moiety on the metal core surface. Meanwhile, infrared measurements showed that the C≡N stretch red-shifted from 2246 to 1944 cm{sup −1} upon adsorption on the nanoparticle surfaces, as confirmed by {sup 15}N isotopic labeling. This apparent red-shift suggests extensive intraparticle charge delocalization, which was further manifested by photoluminescence measurements of 1-cyanopyrene-functionalized ruthenium nanoparticles that exhibited a red shift of 40 nm of the emission maximum, in comparison to that of free monomers. The results further highlight the significance of metal−organic contacts in the manipulation of the dynamics of intraparticle charge transfer and the nanoparticle optical and electronic properties.

  17. Gold (I)-Catalyzed Diastereo- and Enantioselective 1,3-Dipolar Cycloaddition and Mannich Reactions of Azlactones

    Science.gov (United States)

    Melhado, Asa D.; Amarante, Giovanni W.; Wang, Z. Jane; Luparia, Marco; Toste, F. Dean

    2011-01-01

    Azlactones participate in stereoselective reactions with electron-deficient alkenes and N-sulfonyl aldimines to give products of 1,3-dipolar cycloaddition and Mannich addition reactions respectively. Both of these reactions proceed with good to excellent diastereo- and enantioselectivity using a single class of gold-catalysts, namely C2-symmetric bis(phosphinegold(I) carboxylate)complexes. The development of the azlactone Mannich reaction to provide fully protected anti-α,β-diamino acid derivatives is described. 1,3-Dipolar cycloaddition reactions of several acyclic 1,2-disubstituted alkenes, and the chemistry of the resultant cycloadducts, are examined to probe the stereochemical course of this reaction. Reaction kinetics and tandem MS studies of both the cycloaddition and Mannich reactions are reported. These studies support a mechanism in which the gold complexes catalyze addition reactions through nucleophile activation rather than the more typical activation of the electrophilic reaction component. PMID:21341677

  18. Production and Characterization of a Nitrilase fromPseudomonas aeruginosaRZ44 and its Potential for Nitrile Biotransformation.

    Science.gov (United States)

    Badoei-Dalfard, Arastoo; Ramezani-Pour, Narjes; Karami, Zahra

    2016-09-01

    The conversion of nitriles into amides or carboxylic acids by nitrilase has taken its application into consideration, as the scope of its applications has recently been extended. In this study, P. aeruginosa RZ44 was isolated from sewage in the Kerman which has Nitrile-degradation activity. In order to improve the nitrilase production, several optimization were done on environmental condition. Nitrilase activity was characterized against different pHs, temperatures, ions, and substrates. Enzyme activity was evaluated by determining the production of ammonia following to the modification of the phenol/hypochlorite method. Different factors that affect production of the enzyme by P. aeruginosa RZ44 were optimized and evaluated in the culture mediums. The results showed that degradation of the acetonitrile by P. aeruginosa RZ44 increased the pH of the growth medium from the initial pH 7.0 to 9.37. Optimizing the medium for P. aeruginosa RZ44, it was found that glucose and starch (5 g.L -1 ) have strongly supported nitrilase production, compared to the control. As well, urea (5 g.L -1 ) and yeast extract (15 g.L -1 ) have favored an increased biomass and nitrilase production, as the nitrogen sources. These results show that nitrilase production increases in the pH range 5.0 to 7.0 and then start decreasing. Addition of the Mg 2+ , Fe 2+ and Na + has supported the biomass and nitrilase production. Co 2+ , Mn 2+ and Cu 2+ were confirmed to inhibit cell growth and enzyme production. Enzyme characterization results show that, P. aeruginosa RZ44 nitrilase exhibits comparatively high activity and stability at pH 7.0 and 40°C. Nitrilase was completely inhibited by CoCl 2 and CaCl 2 , whereas, the inhibition in the presence of MnSO 4 and CuSO4 was about 60%. Time course analysis of the nitrile conversion by the resting P. aeruginosa RZ44 cells showed that nitrile substrates (i.e. acetonitrile) was hydrolyzed within 8 h. these results indicate that P. aeruginosa RZ44 has the

  19. Self-Subunit Swapping Occurs in Another Gene Type of Cobalt Nitrile Hydratase

    Science.gov (United States)

    Xia, Yuanyuan; Cui, Youtian; Kobayashi, Michihiko; Zhou, Zhemin

    2012-01-01

    Self-subunit swapping is one of the post-translational maturation of the cobalt-containing nitrile hydratase (Co-NHase) family of enzymes. All of these NHases possess a gene organization of , which allows the activator protein to easily form a mediatory complex with the α-subunit of the NHase after translation. Here, we discovered that the incorporation of cobalt into another type of Co-NHase, with a gene organization of , was also dependent on self-subunit swapping. We successfully isolated a recombinant NHase activator protein (P14K) of Pseudomonas putida NRRL-18668 by adding a Strep-tag N-terminal to the P14K gene. P14K was found to form a complex [α(StrepP14K)2] with the α-subunit of the NHase. The incorporation of cobalt into the NHase of P. putida was confirmed to be dependent on the α-subunit substitution between the cobalt-containing α(StrepP14K)2 and the cobalt-free NHase. Cobalt was inserted into cobalt-free α(StrepP14K)2 but not into cobalt-free NHase, suggesting that P14K functions not only as a self-subunit swapping chaperone but also as a metallochaperone. In addition, NHase from P. putida was also expressed by a mutant gene that was designed with a order. Our findings expand the general features of self-subunit swapping maturation. PMID:23226397

  20. Advanced Booster Composite Case/Polybenzimidazole Nitrile Butadiene Rubber Insulation Development

    Science.gov (United States)

    Gentz, Steve; Taylor, Robert; Nettles, Mindy

    2015-01-01

    The NASA Engineering and Safety Center (NESC) was requested to examine processing sensitivities (e.g., cure temperature control/variance, debonds, density variations) of polybenzimidazole nitrile butadiene rubber (PBI-NBR) insulation, case fiber, and resin systems and to evaluate nondestructive evaluation (NDE) and damage tolerance methods/models required to support human-rated composite motor cases. The proposed use of composite motor cases in Blocks IA and II was expected to increase performance capability through optimizing operating pressure and increasing propellant mass fraction. This assessment was to support the evaluation of risk reduction for large booster component development/fabrication, NDE of low mass-to-strength ratio material structures, and solid booster propellant formulation as requested in the Space Launch System NASA Research Announcement for Advanced Booster Engineering Demonstration and/or Risk Reduction. Composite case materials and high-energy propellants represent an enabling capability in the Agency's ability to provide affordable, high-performing advanced booster concepts. The NESC team was requested to provide an assessment of co- and multiple-cure processing of composite case and PBI-NBR insulation materials and evaluation of high-energy propellant formulations.

  1. Cloning and functional characterization of nitrilase from Fusarium proliferatum AUF-2 for detoxification of nitriles.

    Science.gov (United States)

    Yusuf, Farnaz; Rather, Irshad Ahmad; Jamwal, Urmila; Gandhi, Sumit G; Chaubey, Asha

    2015-07-01

    A fungal nitrilase gene from Fusarium proliferatum AUF-2 was cloned through reverse transcription-PCR. The open reading frame consisted of 903 bp and potentially encoded a protein of 301 amino acid residues with a theoretical molecular mass of 33.0 kDa. The encoding gene was expressed in Escherichia coli strain BL21 and the recombinant protein with His6-tag was purified to electrophoretic homogeneity. The purified enzyme exhibited optimal activity in the range of 35-40 °C and pH 8.0. EDTA, Mg(2+), Zn(2+), Ca(2+), Fe(2+), Fe(3+) and Mn(2+) stimulated hydrolytic activity, whereas Cu(2+), Co(2+) and Ni(2+) had inhibitory effect on nitrilase activity. Ag(+) ions showed a strong inhibitory effect on the recombinant nitrilase activity. This nitrilase was specific towards aliphatic, heterocyclic and aromatic nitriles. The kinetic parameters V(max) and K(m) for benzonitrile substrate were determined to be 14.6 μmol/min/mg protein and 1.55 mM, respectively. Homology modelling and molecular docking studies provided an insight into the substrate specificity and the proposed catalytic triad for recombinant nitrilase consisted of Glu-54, Lys-133 and Cys-175. This is the first report on the cloning and heterologous expression of nitrilase from Fusarium proliferatum.

  2. Permeation of limonene through disposable nitrile gloves using a dextrous robot hand

    Science.gov (United States)

    Banaee, Sean; S Que Hee, Shane

    2017-01-01

    Objectives: The purpose of this study was to investigate the permeation of the low-volatile solvent limonene through different disposable, unlined, unsupported, nitrile exam whole gloves (blue, purple, sterling, and lavender, from Kimberly-Clark). Methods: This study utilized a moving and static dextrous robot hand as part of a novel dynamic permeation system that allowed sampling at specific times. Quantitation of limonene in samples was based on capillary gas chromatography-mass spectrometry and the internal standard method (4-bromophenol). Results: The average post-permeation thicknesses (before reconditioning) for all gloves for both the moving and static hand were more than 10% of the pre-permeation ones (P≤0.05), although this was not so on reconditioning. The standardized breakthrough times and steady-state permeation periods were similar for the blue, purple, and sterling gloves. Both methods had similar sensitivity. The lavender glove showed a higher permeation rate (0.490±0.031 μg/cm2/min) for the moving robotic hand compared to the non-moving hand (P≤0.05), this being ascribed to a thickness threshold. Conclusions: Permeation parameters for the static and dynamic robot hand models indicate that both methods have similar sensitivity in detecting the analyte during permeation and the blue, purple, and sterling gloves behave similarly during the permeation process whether moving or non-moving. PMID:28111415

  3. Sound Absorption Properties Of Single-Hole Hollow Polyester Fiber Reinforced Hydrogenated Carboxyl Nitrile Rubber Composites

    Directory of Open Access Journals (Sweden)

    Jie Hong

    2017-09-01

    Full Text Available A series of single-hole hollow polyester fiber (SHHPF reinforced hydrogenated carboxyl nitrile rubber (HXNBR composites were fabricated. In this study, the sound absorption property of the HXNBR/SHHPF composite was tested in an impedance tube, the composite morphology was characterized by scanning electron microscope (SEM, and the tensile mechanical property was measured by strength tester. The results demonstrated that a remarkable change in sound absorption can be observed by increasing the SHHPF content from 0% to 40%. In the composite with 40% SHHPF in 1 mm thickness, the sound absorption coefficient reached 0.671 at 2,500 Hz; the effective bandwidth was 1,800-2,500 Hz for sound absorption coefficient larger than 0.2. But the sound absorption property of the composite deteriorated when the SHHPF content increased to 50% in 1 mm thickness. While with 20% SHHPF proportion, the sound absorption property was improved by increasing the thickness of composites from 1 to 5 mm. Compared with the pure HXNBR of the same thickness, the tensile mechanical property of the composite improved significantly by increasing the SHHPF proportion. As a lightweight composite with excellent sound absorption property, the HXNBR/SHHPF composite has potential practical application value in the fields of engineering.

  4. Activity Enhancement Based on the Chemical Equilibrium of Multiple-Subunit Nitrile Hydratase from Bordetella petrii.

    Science.gov (United States)

    Liu, Yi; Liu, Ping; Lin, Lu; Zhao, Yueqin; Zhong, Wenjuan; Wu, Lunjie; Zhou, Zhemin; Sun, Weifeng

    2016-09-01

    The maturation mechanism of nitrile hydratase (NHase) of Pseudomonas putida NRRL-18668 was discovered and named as "self-subunit swapping." Since the NHase of Bordetella petrii DSM 12804 is similar to that of P. putida, the NHase maturation of B. petrii is proposed to be the same as that of P. putida. However, there is no further information on the application of NHase according to these findings. We successfully rapidly purified NHase and its activator through affinity his tag, and found that the cell extracts of NHase possessed multiple types of protein ingredients including α, β, α2β2, and α(P14K)2 who were in a state of chemical equilibrium. Furthermore, the activity was significantly enhanced through adding extra α(P14K)2 to the cell extracts of NHase according to the chemical equilibrium. Our findings are useful for the activity enhancement of multiple-subunit enzyme and for the first time significantly increased the NHase activity according to the chemical equilibrium.

  5. Swelling and tribological properties of melt-mixed fluoroelastomer/nitrile rubber blends under crude oil

    Science.gov (United States)

    Tagelsir, Yasin; Li, San-Xi; Lv, Xiaoren; Wang, Shijie; Wang, Song; Osman, Zeinab

    2018-01-01

    The melt-mixed fluoroelastomer (FKM)/ nitrile rubber (NBR) blends of (90/10, 80/20, 70/30, 60/40 and 50/50) ratios with same hardness were prepared, and their swelling and tribological properties under crude oil were investigated for the purpose of developing high performance cost-effective elastomers meeting requirement of oil extraction progressive cavity pump stator. Differential scanning calorimetry confirmed compatible blend system for all blends. Field emission scanning electron microscopy (FE-SEM) showed co-continuous morphology of 200–400 nm phase size for all blends, expect FKM/NBR (90/10) which exhibited partially continuous phase morphology of 100–250 nm phase size. The results of swelling and linear wear tests under crude oil indicated that swelling percentage, coefficient of friction and specific wear rate of FKM/NBR blends were much better than NBR, with FKM/NBR (90/10 and 80/20) showing swelling percentage and specific wear rate very close to FKM. Attenuated total reflectance-Fourier transform infrared spectroscopy disclosed that fracture of macromolecular chains was the main mechanochemical effect of unswollen and swollen worn surfaces, in addition to oxygenated degradation detected with increasing NBR ratio in the blends. The fracture of macromolecular chains resulted in slight fatigue wear mechanism, which was also confirmed by FE-SEM of the worn surfaces.

  6. Effect of Nanoclay on Mechanical Properties and Ablation Behavior of a Nitrile-Based Heat Insulator

    Directory of Open Access Journals (Sweden)

    Fatemeh Arabgol

    2013-02-01

    Full Text Available Thermal insulation of rocket motor chamber is one of the most important functions of elastomeric ablative material. Combustion of solid rocket motor propellant produces turbulent media containing gases with a velocity more than 1000 m/s, temperature and pressure more than 3000°C and 10 MPa, respectively,which destroys all metallic alloys. Elastomeric nanocomposite heat insulators are more attractive subjects in comparison to their non-elastomeric counterparts, due to their excellent thermal stresses and larger deformation bearing capacity. Nitrile rubber with high thermal properties is a proper candidate in such applications. Development in ablation performance of these heat shields is considered as an important challenge nowadays. A few works have been recently carried out using organoclay to enhancethe ablation and mechanical properties of heat insulators. In this work, an elastomeric heat insulator with superior ablative and mechanical properties was presented using nanotechnology. The results showed that an elastomeric nanocomposite heat insulator containing 15 wt% organoclay exhibits superior characteristics compared to its composite counterpart such as: 46% more tensile strength, 60% more elongationat-break, 1.7 times higher modulus (at 100% strain, 62% higher “insulating index number” and 36% lower mass ablation and erosion rates under a standard test with a heat flux of 2500 kW/m2 for 15 s.

  7. Natural rubber/nitrile butadiene rubber/hindered phenol composites with high-damping properties

    Directory of Open Access Journals (Sweden)

    Xiuying Zhao

    2015-10-01

    Full Text Available New natural rubber (NR/nitrile butadiene rubber (NBR/hindered phenol (AO-80 composites with high-damping properties were prepared in this study. The morphological, structural, and mechanical properties were characterized by atomic force microscopy (AFM, polarized Fourier transform infrared spectrometer (FTIR, dynamic mechanical thermal analyzer (DMTA, and a tensile tester. Each composite consisted of two phases: the NR phase and the NBR/AO-80 phase. There was partial compatibility between the NR phase and the NBR/AO-80 phase, and the NR/NBR/AO-80 (50/50/20 composite exhibited a co-continuous morphology. Strain-induced crystallization occurred in the NR phase at strains higher than 200%, and strain-induced orientation appeared in the NBR/AO-80 phase with the increase of strain from 100% to 500%. The composites had a special stress–strain behavior and mechanical properties because of the simultaneous strain-induced orientation and strain-induced crystallization. In the working temperature range of a seismic isolation bearing, the composites (especially the NR/NBR/AO-80 (50/50/20 composite presented a high loss factor, high area of loss peak (TA, and high hysteresis energy. Therefore, the NR/NBR/AO-80 rubber composites are expected to have important application as a high-performance damping material for rubber bearing.

  8. Catalytic Asymmetric Synthesis of 8-Oxabicyclooctanes by Intermolecular [5+2] Pyrylium Cycloadditions**

    Science.gov (United States)

    Witten, Michael R.

    2014-01-01

    Highly enantioselective intermolecular [5+2] cycloadditions of pyrylium ion intermediates with electron-rich alkenes are promoted by a dual catalyst system composed of an achiral thiourea and a chiral primary aminothiourea. The observed enantioselectivity is highly dependent on the substitution pattern of the 5π component, and the basis for this effect is analyzed using experimental and computational evidence. The resultant 8-oxabicyclo[3.2.1]octane derivatives possess a scaffold common in natural products and medicinally active compounds and are also versatile chiral building blocks for further manipulations. Several stereoselective complexity-generating transformations of the 8-oxabicyclooctane products are presented. PMID:24782332

  9. Causation in a Cascade: The Origins of Selectivities in Intramolecular Nitrone Cycloadditions

    Science.gov (United States)

    Krenske, Elizabeth H.; Agopcan, Sesil; Aviyente, Viktorya; Houk, K. N.; Johnson, Brian A.; Holmes, Andrew B.

    2012-01-01

    The factors controlling chemo-, regio-, and stereoselectivity in a cascade of reactions starting from a bis(cyanoalkenyl)oxime and proceeding via nitrone cycloadditions, have been unravelled through a series of density functional calculations with several different functionals. Both kinetic and thermodynamic control of the reaction cascade are important depending upon conditions. Kinetic control is analysed by the distortion/interaction model and is found to be dictated by differences in distortions of the cycloaddends in the transition states. A new mechanism competing with that originally proposed in the application of these reactions to the histrionicotoxin synthesis is discovered in these studies. PMID:22788115

  10. Triazol-substituted titanocenes by strain-driven 1,3-dipolar cycloadditions

    Directory of Open Access Journals (Sweden)

    Andreas Gansäuer

    2014-07-01

    Full Text Available An operationally simple, convenient, and mild strategy for the synthesis of triazole-substituted titanocenes via strain-driven 1,3-dipolar cycloadditions between azide-functionalized titanocenes and cyclooctyne has been developed. It features the first synthesis of titanocenes containing azide groups. These compounds constitute ‘second-generation’ functionalized titanocene building blocks for further synthetic elaboration. Our synthesis is modular and large numbers of the complexes can in principle be prepared in short periods of time. Some of the triazole-substituted titanocenes display high cyctotoxic activity against BJAB cells. Comparison of the most active complexes allows the identification of structural features essential for biological activity.

  11. Syntheses of strychnine, norfluorocurarine, dehydrodesacetylretuline, and valparicine enabled by intramolecular cycloadditions of Zincke aldehydes.

    Science.gov (United States)

    Martin, David B C; Nguyen, Lucas Q; Vanderwal, Christopher D

    2012-01-06

    A full account of the development of the base-mediated intramolecular Diels-Alder cycloadditions of tryptamine-derived Zincke aldehydes is described. This important complexity-generating transformation provides the tetracyclic core of many indole monoterpene alkaloids in only three steps from commercially available starting materials and played a key role in short syntheses of norfluorocurarine (five steps), dehydrodesacetylretuline (six steps), valparicine (seven steps), and strychnine (six steps). Reasonable mechanistic possibilities for this reaction, a surprisingly facile dimerization of the products, and an unexpected cycloreversion to regenerate Zincke aldehydes under specific conditions are also discussed.

  12. Synthesis of 1,4-naphthoquinone derivatives using 1,3-dipolar cycloaddition and Sonogashira reactions

    Directory of Open Access Journals (Sweden)

    Wilson Silva do Nascimento

    2010-04-01

    Full Text Available Naphthoquinones are known according to their important bio-activities, such as their antitumoral and topoisomerase inhibition properties. From 2-azido (3 or 2,3-diacetylene-1,4-naphthoquinone (4 it was possible to obtain triazole derivatives (naphthoquinonic. This work describes the synthesis of two novel molecules, with triazole groups linked to 1,4-naphthoquinone using the 1,3-dipolar cycloaddition and Sonogashira reactions. The synthetic strategy followed two routes (Scheme 1. First, we synthesized the 2-bromo-1,4-naphthoquinone (2, yield 98% by using Br2 and CH3CO2H, and then used it to obtain 2-azido-1,4-naphthoquinone (3, yield 62% from compound 1, along with ethanolic solution (reflux and NaN3. Finally, we prepared 1,2,3-triazole compounds (4a, b by 1,3-dipolar cycloaddition, involving compound (3 and terminal acetylenes (phenylacetylene, a and glycoside (b using Cu(OAc2 and ascorbate, under argon atmosphere. During the second step, 2,3-dibromo-1,4-naphthoquinone was prepared using Br2/CH2Cl2 at room temperature. From compound (5 it was possible to synthesize (6, catalyzed by Pd(PPh32Cl2/CuI/Et3N, under argon atmosphere, in 40% yield. The 1,3-dipolar cycloaddition reactions involving 2-azido-1,4-naphthoquinone (3 and alkynes (a, yield 23% and b, yield 30% were conducted using the solvent system, (1:1 terc-BuOH/H2O/r.t/ 20 mol% of Cu(OAc2 and sodium ascorbate, under stirring during 24 hours. The reaction involving 2,3-dibromo-1,4-naphthoquinone (5, yield 65% and phenylacetylene was prepared using the solvent mixture (2:1 DMSO/CHCl3 and catalytic amount of CuI/Pd(PPh32Cl2. The final products were characterized by elemental analysis and spectrometric techniques (IR, NMR 1H and 13C. Two novel triazole compounds were synthesized from naphthoquinones by 1,3-dipolar cycloaddition from suitable 1,4-naphthoquinones obtained by Sonogashira couplings.

  13. Emerging approaches for the synthesis of triazoles: beyond metal-catalyzed and strain-promoted azide-alkyne cycloaddition.

    Science.gov (United States)

    Lima, Carolina G S; Ali, Akbar; van Berkel, Sander S; Westermann, Bernhard; Paixão, Márcio W

    2015-07-11

    Metal-free 1,3-dipolar cycloaddition reactions have proven to be a powerful tool for the assembly of key heterocycles, in particular diversely functionalized 1,2,3-triazoles. A number of metal-free (3+2)-cycloaddition approaches have been developed up to date with the aim to circumvent the use of metal catalysts allowing these reactions to take place in biological systems without perturbation of the naturally occurring processes. This feature article specifically provides an overview of emerging metal-free synthetic routes, and their mechanistic features, in the formation of functionalized 1,2,3-triazoles.

  14. Conversion of Oximes to Carbonyl Compounds by Triscetylpyridinium Tetrakis(oxodiperoxotungsto Phosphate (PCWP-mediated Oxidation with Hydrogen Peroxide

    Directory of Open Access Journals (Sweden)

    Rosa M. Toscano

    2008-06-01

    Full Text Available Aromatic and aliphatic oximes have been deoximated in chloroform-water to the corresponding aldehydes with dilute hydrogen peroxide and triscetylpyridinium tetrakis (oxodiperoxotungsto phosphate as catalyst. The presence of dipolarophiles in the reaction mixtures allows a competitive reaction that converts oximes into isoxazole and isoxazoline derivatives via the intermediate formation of nitrile oxide species.

  15. Cytotoxic conjugates of betulinic acid and substituted triazoles prepared by Huisgen Cycloaddition from 30-azidoderivatives.

    Directory of Open Access Journals (Sweden)

    Veronika Sidova

    Full Text Available In this work, we describe synthesis of conjugates of betulinic acid with substituted triazoles prepared via Huisgen 1,3-cycloaddition. All compounds contain free 28-COOH group. Allylic bromination of protected betulinic acid by NBS gave corresponding 30-bromoderivatives, their substitution with sodium azides produced 30-azidoderivatives and these azides were subjected to CuI catalysed Huisgen 1,3-cycloaddition to give the final conjugates. Reactions had moderate to high yields. All new compounds were tested for their in vitro cytotoxic activities on eight cancer and two non-cancer cell lines. The most active compounds were conjugates of 3β-O-acetylbetulinic acid and among them, conjugate with triazole substituted by benzaldehyde 9b was the best with IC50 of 3.3 μM and therapeutic index of 9.1. Five compounds in this study had IC50 below 10 μM and inhibited DNA and RNA synthesis and caused block in G0/G1 cell cycle phase which is highly similar to actinomycin D. It is unusual that here prepared 3β-O-acetates were more active than compounds with the free 3-OH group and this suggests that this set may have common mechanism of action that is different from the mechanism of action of previously known 3β-O-acetoxybetulinic acid derivatives. Benzaldehyde type conjugate 9b is the best candidate for further drug development.

  16. Quantifying Possible Routes for SpnF-Catalyzed Formal Diels-Alder Cycloaddition.

    Science.gov (United States)

    Medvedev, Michael G; Zeifman, Alexey A; Novikov, Fedor N; Bushmarinov, Ivan S; Stroganov, Oleg V; Titov, Ilya Yu; Chilov, Ghermes G; Svitanko, Igor V

    2017-03-22

    The Diels-Alder reaction is a cornerstone of modern organic synthesis. Despite this, it remains essentially inaccessible to biosynthetic approaches. Only a few natural enzymes catalyze even a formal [4 + 2] cycloaddition, and it remains uncertain if any of them proceed via the Diels-Alder mechanism. In this study, we focus on the [4 + 2] cycloaddition step in the biosynthesis of spinosyn A, a reaction catalyzed by SpnF enzyme, one of the most promising "true Diels-Alderase" candidates. The four currently proposed mechanisms (including the Diels-Alder one) for this reaction in water (as a first-order approximation of the enzymatic reaction) are evaluated by an exhaustive quantum mechanical search for possible transition states (728 were found in total). We find that the line between the recently proposed bis-pericyclic [J. Am. Chem. Soc. 2016, 138 (11), 3631] and Diels-Alder routes is blurred, and favorable transition states of both types may coexist. Application of the Curtin-Hammett principle, however, reveals that the bis-pericyclic mechanism accounts for ∼83% of the reaction flow in water, while the classical Diels-Alder mechanism contributes only ∼17%. The current findings provide a route for modeling this reaction inside the SpnF active site and inferring the catalytic architecture of possible Diels-Alderases.

  17. Accelerating Strain-Promoted Azide-Alkyne Cycloaddition Using Micellar Catalysis.

    Science.gov (United States)

    Anderton, Grant I; Bangerter, Alyssa S; Davis, Tyson C; Feng, Zhiyuan; Furtak, Aric J; Larsen, Jared O; Scroggin, Triniti L; Heemstra, Jennifer M

    2015-08-19

    Bioorthogonal conjugation reactions such as strain-promoted azide-alkyne cycloaddition (SPAAC) have become increasingly popular in recent years, as they enable site-specific labeling of complex biomolecules. However, despite a number of improvements to cyclooctyne design, reaction rates for SPAAC remain significantly lower than those of the related copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction. Here we explore micellar catalysis as a means to increase reaction rate between a cyclooctyne and hydrophobic azide. We find that anionic and cationic surfactants provide the most efficient catalysis, with rate enhancements of up to 179-fold for reaction of benzyl azide with DIBAC cyclooctyne. Additionally, we find that the presence of surfactant can provide up to 51-fold selectivity for reaction with a hydrophobic over hydrophilic azide. A more modest, but still substantial, 11-fold rate enhancement is observed for micellar catalysis of the reaction between benzyl azide and a DIBAC-functionalized DNA sequence, demonstrating that micellar catalysis can be successfully applied to hydrophilic biomolecules. Together, these results demonstrate that micellar catalysis can provide higher conjugation yields in reduced time when using hydrophobic SPAAC reagents.

  18. Diels–Alder cycloaddition of 2-methylfuran and ethylene for renewable toluene

    Energy Technology Data Exchange (ETDEWEB)

    Green, Sara K.; Patet, Ryan E.; Nikbin, Nima; Williams, C. Luke; Chang, Chun-Chih; Yu, Jingye; Gorte, Raymond J.; Caratzoulas, Stavros; Fan, Wei; Vlachos, Dionisios G.; Dauenhauer, Paul J.

    2016-01-01

    Diels–Alder cycloaddition of biomass-derived 2-methylfuran and ethylene provides a thermochemical pathway to renewable toluene. In this work, the kinetics and reaction pathways of toluene formation have been evaluated with H-BEA and Sn-BEA catalysts. Kinetic analysis of the main reaction chemistries reveals the existence of two rate-controlling reactions: (i) Diels–Alder cycloaddition of 2-methylfuran and ethylene where the production rate is independent of the Brønsted acid site concentration, and (ii) dehydration of the Diels–Alder cycloadduct where the production rate is dependent on the Brønsted acid site concentration. Application of a reduced kinetic model supports the interplay of these two regimes with the highest concentration of toluene measured at a catalyst loading equal to the transition region between the two kinetic regimes. Selectivity to toluene never exceeded 46%, as 2-methylfuran was consumed by several newly identified reactions to side products, including dimerization of 2-methylfuran, the formation of a trimer following hydrolysis and ring-opening of 2-methylfuran, and the incomplete dehydration of the Diels–Alder cycloadduct of 2-methylfuran and ethylene.

  19. Cytotoxic conjugates of betulinic acid and substituted triazoles prepared by Huisgen Cycloaddition from 30-azidoderivatives

    Science.gov (United States)

    Sidova, Veronika; Zoufaly, Pavel; Pokorny, Jan; Dzubak, Petr; Hajduch, Marian; Popa, Igor

    2017-01-01

    In this work, we describe synthesis of conjugates of betulinic acid with substituted triazoles prepared via Huisgen 1,3-cycloaddition. All compounds contain free 28-COOH group. Allylic bromination of protected betulinic acid by NBS gave corresponding 30-bromoderivatives, their substitution with sodium azides produced 30-azidoderivatives and these azides were subjected to CuI catalysed Huisgen 1,3-cycloaddition to give the final conjugates. Reactions had moderate to high yields. All new compounds were tested for their in vitro cytotoxic activities on eight cancer and two non-cancer cell lines. The most active compounds were conjugates of 3β-O-acetylbetulinic acid and among them, conjugate with triazole substituted by benzaldehyde 9b was the best with IC50 of 3.3 μM and therapeutic index of 9.1. Five compounds in this study had IC50 below 10 μM and inhibited DNA and RNA synthesis and caused block in G0/G1 cell cycle phase which is highly similar to actinomycin D. It is unusual that here prepared 3β-O-acetates were more active than compounds with the free 3-OH group and this suggests that this set may have common mechanism of action that is different from the mechanism of action of previously known 3β-O-acetoxybetulinic acid derivatives. Benzaldehyde type conjugate 9b is the best candidate for further drug development. PMID:28158265

  20. Construction of Benzene Rings by Copper-Catalyzed Cycloaddition Reactions of Oximes and Maleimides: An Access to Fused Phthalimides.

    Science.gov (United States)

    Yang, Jie; Zhao, Bo; Xi, Yue; Sun, Si; Yang, Zhen; Ye, Ying; Jiang, Kun; Wei, Ye

    2018-02-16

    A useful Cu-catalyzed cycloaddition protocol for the construction of benzene rings has been achieved. The reactions, utilizing readily available oximes and maleimides as starting materials, proceed under mild reaction conditions to generate a series of structurally interesting fused-phthalimides that are difficult to be prepared by conventional methods.

  1. 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.

  2. Structural Complexity Through Multicomponent Cycloaddition Cascades Enabled by Dual-Purpose, Reactivity Regenerating 1,2,3-Triene Equivalents

    Science.gov (United States)

    Wender, Paul A.; Fournogerakis, Dennis N.; Jeffreys, Matthew S.; Quiroz, Ryan V.; Inagaki, Fuyuhiko; Pfaffenbach, Magnus

    2014-01-01

    Multicomponent reactions allow for more bond-forming events per synthetic operation, enabling more step and time economical conversion of simple starting materials to complex and thus value-added targets. These processes invariably require that reactivity be relayed from intermediate to intermediate over several mechanistic steps until a termination event produces the final product. Here we report a multicomponent process in which a novel 1,2,3-butatriene equivalent (TMSBO: TMSCH2C≡CCH2OH) engages chemospecifically as a two-carbon alkyne component in a metal-catalyzed [5+2] cycloaddition with a vinylcyclopropane to produce an intermediate cycloadduct. Under the reaction conditions, this intermediate undergoes a remarkably rapid 1,4-Peterson elimination, producing a reactive four-carbon diene intermediate that is readily intercepted in either a metal-catalyzed or thermal [4+2] cycloaddition. TMSBO thus serves as an yne-to-diene transmissive reagent coupling two powerful and convergent cycloadditions - the homologous Diels-Alder and Diels-Alder cycloadditions - through a vinylogous Peterson elimination, and enabling flexible access to diverse polycycles. PMID:24755598

  3. Microwave-Enhanced Organic Syntheses for the Undergraduate Laboratory: Diels-Alder Cycloaddition, Wittig Reaction, and Williamson Ether Synthesis

    Science.gov (United States)

    Baar, Marsha R.; Falcone, Danielle; Gordon, Christopher

    2010-01-01

    Microwave heating enhanced the rate of three reactions typically performed in our undergraduate organic chemistry laboratory: a Diels-Alder cycloaddition, a Wittig salt formation, and a Williamson ether synthesis. Ninety-minute refluxes were shortened to 10 min using a laboratory-grade microwave oven. In addition, yields improved for the Wittig…

  4. Evolution of heteromeric nitrilase complexes in Poaceae with new functions in nitrile metabolism

    Science.gov (United States)

    Jenrich, Roland; Trompetter, Inga; Bak, Søren; Olsen, Carl Erik; Møller, Birger Lindberg; Piotrowski, Markus

    2007-01-01

    Members of the nitrilase 4 (NIT4) family of higher plants catalyze the conversion of β-cyanoalanine to aspartic acid and asparagine, a key step in cyanide detoxification. Grasses (Poaceae) possess two different NIT4 homologs (NIT4A and NIT4B), but none of the recombinant Poaceae enzymes analyzed showed activity with β-cyanoalanine, whereas protein extracts of the same plants clearly posses this activity. Sorghum bicolor contains three NIT4 isoforms SbNIT4A, SbNIT4B1, and SbNIT4B2. Individually, each isoform does not possess enzymatic activity whereas the heteromeric complexes SbNIT4A/B1 and SbNIT4A/B2 hydrolyze β-cyanoalanine with high activity. In addition, the SbNIT4A/B2 complex accepts additional substrates, the best being 4-hydroxyphenylacetonitrile. Corresponding NIT4A and NIT4B isoforms from other Poaceae species can functionally complement the sorghum isoforms in these complexes. Site-specific mutagenesis of the active site cysteine residue demonstrates that hydrolysis of β-cyanoalanine is catalyzed by the NIT4A isoform in both complexes whereas hydrolysis of 4-hydroxyphenylacetonitrile occurs at the NIT4B2 isoform. 4-Hydroxyphenylacetonitrile was shown to be an in vitro breakdown product of the cyanogenic glycoside dhurrin, a main constituent in S. bicolor. The results indicate that the SbNIT4A/B2 heterocomplex plays a key role in an endogenous turnover of dhurrin proceeding via 4-hydroxyphenylacetonitrile and thereby avoiding release of toxic hydrogen cyanide. The operation of this pathway would enable plants to use cyanogenic glycosides as transportable and remobilizable nitrogenous storage compounds. Through combinatorial biochemistry and neofunctionalizations, the small family of nitrilases has gained diverse biological functions in nitrile metabolism. PMID:18003897

  5. Do clinical examination gloves provide adequate electrical insulation for safe hands-on defibrillation? I: Resistive properties of nitrile gloves.

    Science.gov (United States)

    Deakin, Charles D; Lee-Shrewsbury, Victoria; Hogg, Kitwani; Petley, Graham W

    2013-07-01

    Uninterrupted chest compressions are a key factor in determining resuscitation success. Interruptions to chest compression are often associated with defibrillation, particularly the need to stand clear from the patient during defibrillation. It has been suggested that clinical examination gloves may provide adequate electrical resistance to enable safe hands-on defibrillation in order to minimise interruptions. We therefore examined whether commonly used nitrile clinical examination gloves provide adequate resistance to current flow to enable safe hands-on defibrillation. Clinical examination gloves (Kimberly Clark KC300 Sterling nitrile) worn by members of hospital cardiac arrest teams were collected immediately following termination of resuscitation. To determine the level of protection afforded by visually intact gloves, electrical resistance across the glove was measured by applying a DC voltage across the glove and measuring subsequent resistance. Forty new unused gloves (control) were compared with 28 clinical (non-CPR) gloves and 128 clinical (CPR) gloves. One glove in each group had a visible tear and was excluded from analysis. Control gloves had a minimum resistance of 120 kΩ (median 190 kΩ) compared with 60 kΩ in clinical gloves (both CPR (median 140 kΩ) and non-CPR groups (median 160 kΩ)). Nitrile clinical examination gloves do not provide adequate electrical insulation for the rescuer to safely undertake 'hands-on' defibrillation and when exposed to the physical forces of external chest compression, even greater resistive degradation occurs. Further work is required to identify gloves suitable for safe use for 'hands-on' defibrillation. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

  6. Properties of Nitrile Rubber/Clay Nanocomposites Prepared by In-Situ Emulsifier-free Emulsion Polymerization

    Directory of Open Access Journals (Sweden)

    Alireza Bagherian Mahmoodabadi

    2015-07-01

    Full Text Available Nitrile rubber/clay nanocomposites were prepared via in-situ emulsifier-free emulsion polymerization technique in the presence of 2-acrylamido-2-methylpropane sulfonic acid (AMPS and pristine sodium montmorillonite (Na-MMT. The morphology of the nanocomposites was studied using X-ray diffraction (XRD patterns and transmission electron microscopy (TEM. The XRD results showed exfoliated morphology for the nanocomposites containing up to 3 wt% nanoclay and exfoliated-intercalated morphology for the nanocomposite containing 5 wt% nanoclay. The basal spacing of the nanocomposite, containing 5 wt% nanoclay, was increased to 1.8 nm, which was 0.61 nm wider than that obtained using pristine Na-MMT. Compared to neat rubber, the thermogravimetric analysis (TGA revealed improvements in the thermal stability of all nanocomposite samples, in which the thermal degradation temperature was increased by increasing the clay content. The maximum increase in the thermal stability of the nanocomposites was obtained for the nanocomposite containing 5 wt% nanoclay with exfoliated-intercalated morphology. The tensile testing results showed remarkable improvements in the mechanical strength of the nanocomposites. In comparison with the neat nitrile rubber, the exfoliated nanocomposite, containing 3 wt% nanoclay, showed 302% and 219% increases in tensile modulus and tensile strength, respectively. The reason for improvementin mechanical properties of a nanocomposite, containing 3 wt% of nanoclay with respect to the nanocomposite containing 5 wt% of nanoclay, was related to the better dispersion of nanoclay platelets in the matrix and formation of exfoliated morphology. In addition, elongation-at-break and hardness were increased in the  nanocomposites, when compared with the neat nitrile rubber.

  7. Synthesis of 2-Alkenylquinoline by Reductive Olefination of Quinoline N-Oxide under Metal-Free Conditions.

    Science.gov (United States)

    Xia, Hong; Liu, Yuanhong; Zhao, Peng; Gou, Shaohua; Wang, Jun

    2016-04-15

    Synthesis of 2-alkenylquinoline by reductive olefination of quinoline N-oxide under metal-free conditions is disclosed. Practically, the reaction could be performed with quinoline as starting material via a one-pot, two-step process. A possible mechanism is proposed that involves a sequential 1,3-dipolar cycloaddition and acid-assisted ring opening followed by a dehydration process.

  8. High-resolution structure of the nitrile reductase QueF combined with molecular simulations provide insight into enzyme mechanism.

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Y.; Zhou, M.; Moy, S.; Morales, J.; Cunningham, M.; Joachimiak, A.; Biosciences Division; Univ. of Texas-Pan American

    2010-01-01

    Here, we report the 1.53-{angstrom} crystal structure of the enzyme 7-cyano-7-deazaguanine reductase (QueF) from Vibrio cholerae, which is responsible for the complete reduction of a nitrile (C {triple_bond} N) bond to a primary amine (H{sub 2}C-NH{sub 2}). At present, this is the only example of a biological pathway that includes reduction of a nitrile bond, establishing QueF as particularly noteworthy. The structure of the QueF monomer resembles two connected ferrodoxin-like domains that assemble into dimers. Ligands identified in the crystal structure suggest the likely binding conformation of the native substrates NADPH and 7-cyano-7-deazaguanine. We also report on a series of numerical simulations that have shed light on the mechanism by which this enzyme affects the transfer of four protons (and electrons) to the 7-cyano-7-deazaguanine substrate. In particular, the simulations suggest that the initial step of the catalytic process is the formation of a covalent adduct with the residue Cys194, in agreement with previous studies. The crystal structure also suggests that two conserved residues (His233 and Asp102) play an important role in the delivery of a fourth proton to the substrate.

  9. Identification of dipeptidyl nitriles as potent and selective inhibitors of cathepsin B through structure-based drug design.

    Science.gov (United States)

    Greenspan, P D; Clark, K L; Tommasi, R A; Cowen, S D; McQuire, L W; Farley, D L; van Duzer, J H; Goldberg, R L; Zhou, H; Du, Z; Fitt, J J; Coppa, D E; Fang, Z; Macchia, W; Zhu, L; Capparelli, M P; Goldstein, R; Wigg, A M; Doughty, J R; Bohacek, R S; Knap, A K

    2001-12-20

    Cathepsin B is a member of the papain superfamily of cysteine proteases and has been implicated in the pathology of numerous diseases, including arthritis and cancer. As part of an effort to identify potent, reversible inhibitors of this protease, we examined a series of dipeptidyl nitriles, starting with the previously reported Cbz-Phe-NH-CH(2)CN (19, IC(50) = 62 microM). High-resolution X-ray crystallographic data and molecular modeling were used to optimize the P(1), P(2), and P(3) substituents of this template. Cathepsin B is unique in its class in that it contains a carboxylate recognition site in the S(2)' pocket of the active site. Inhibitor potency and selectivity were enhanced by tethering a carboxylate functionality from the carbon alpha to the nitrile to interact with this region of the enzyme. This resulted in the identification of compound 10, a 7 nM inhibitor of cathepsin B, with excellent selectivity over other cysteine cathepsins.

  10. Establishment of Bioprocess for Synthesis of Nicotinamide by Recombinant Escherichia coli Expressing High-Molecular-Mass Nitrile Hydratase.

    Science.gov (United States)

    Wang, Zhe; Liu, Zhongmei; Cui, Wenjing; Zhou, Zhemin

    2017-08-01

    Application of engineered bacteria expressing nitrile hydratase for the production of amide is getting tremendous attention due to the rapid development of recombinant DNA technique. This study evaluated the effect of 3-cyanopyridine concentrations on nicotinamide production using recombinant Escherichia coli strain (BAG) expressing high-molecular-mass nitrile hydratase from Rhodococcus rhodochrous J1, and established proper process of whole-cell catalysis of 3-cyanopyridine and high cell-density cultivation. The process of substrate fed-batch was applied in the production of nicotinamide, and the concentration of product reached 390 g/L under the condition of low cell-density. After the high cell-density cultivation of BAG in 5 L bioreactor, the OD 600 of cell attained 200 and the total activity reached 2813 U/mL. Different high density of BAG after fermentation in the tank was used to catalyze 3-cyanopyridine, and the concentration of nicotinamide reached to 508 g/L in just 60 min. The productivity of BAG was 212% higher than that of R. rhodochrous J1, and it is possible that BAG is able to achieve industrial production of nicotinamide.

  11. Prebiotic synthesis of 2-deoxy-d-ribose from interstellar building blocks promoted by amino esters or amino nitriles.

    Science.gov (United States)

    Steer, Andrew M; Bia, Nicolas; Smith, David K; Clarke, Paul A

    2017-09-25

    Understanding the prebiotic genesis of 2-deoxy-d-ribose, which forms the backbone of DNA, is of crucial importance to unravelling the origins of life, yet remains open to debate. Here we demonstrate that 20 mol% of proteinogenic amino esters promote the selective formation of 2-deoxy-d-ribose over 2-deoxy-d-threopentose in combined yields of ≥4%. We also demonstrate the first aldol reaction promoted by prebiotically-relevant proteinogenic amino nitriles (20 mol%) for the enantioselective synthesis of d-glyceraldehyde with 6% ee, and its subsequent conversion into 2-deoxy-d-ribose in yields of ≥ 5%. Finally, we explore the combination of these two steps in a one-pot process using 20 mol% of an amino ester or amino nitrile promoter. It is hence demonstrated that three interstellar starting materials, when mixed together with an appropriate promoter, can directly lead to the formation of a mixture of higher carbohydrates, including 2-deoxy-d-ribose.

  12. Inhibition of enterovirus 71 replication by an α-hydroxy-nitrile derivative NK-1.9k.

    Science.gov (United States)

    Wang, Yaxin; Cao, Lin; Zhai, Yangyang; Ma, Jiaming; Nie, Quandeng; Li, Ting; Yin, Zheng; Sun, Yuna; Shang, Luqing

    2017-05-01

    Enterovirus 71 (EV71) is one of the major etiological agents of human hand-foot-and-mouth disease (HFMD) worldwide. EV71 infection in young children and people with immunodeficiency causes severe symptoms with a high fatality rates. However, there is still no approved drugs to treat such infections. Based on our previous report of a peptide-aldehyde anti-EV71 protease, we present here a highly specific α-hydroxy-nitrile derivative NK-1.9k, which inhibited the proliferation of multiple EV71 strains and coxsackievirus A16 (CVA16) in various cells with EC 50 of 37.0 nM with low cytotoxicity (CC 50  > 200 μM). The hydroxy-nitrile covalent warhead conferred NK-1.9k high potency and selectivity to interact with the cysteine residue of the active site of the viral protease. We also documented the resistance to NK-1.9k with a N69S mutation in EV71 3C pro . The combination of NK-1.9k and EV71 polymerase or entry inhibitors produced strong synergistic antiviral effects. Collectively, our findings suggest our compounds can potentially be developed as drugs for the treatment of HFMD. Copyright © 2017. Published by Elsevier B.V.

  13. Efficient synthesis of functionalized 1,2,3-triazoles by catalyst-free 1,3-dipolar cycloaddition of nitroalkenes with sodium azide

    International Nuclear Information System (INIS)

    Wang, Ting; Hu, Xiao-Chun; Huang, Xu-Jiao; Li, Xin-Sheng; Xie, Jian-Wu

    2012-01-01

    A simple and efficient protocol has been developed for the synthesis of 1,2,3-triazole derivatives by catalyst-free 1,3-dipolar cycloaddition of nitroalkenes with sodium azide under mild conditions (author)

  14. Electronic effects of ruthenium-catalyzed [3+2]-cycloaddition of alkynes and azides

    KAUST Repository

    Hou, Duenren

    2010-11-01

    A combined experimental and theoretical study of ruthenium-catalyzed azide-alkyne cycloaddition (RuAAC) reactions is presented and various electronic analyses were conducted to provide a basis in understanding the observed regioselectivity of the 1,2,3-triazole products. Computational studies using density functional theory (DFT) and atoms in molecules quantum theory (AIM) further yield fresh details on the electronic factors that determine the regioselectivity in the RuAAC. It is found that the formation of 1,2,3-triazole products is irreversible and from the Hammett study, the pathway involving a vinyl cationic intermediate is ruled out. The electronic effect favors the formation of 5-electron-donating-group substituted-1,2,3-trizoles. © 2010 Elsevier Ltd. All rights reserved.

  15. Azide-Alkyne Huisgen [3+2] Cycloaddition Using CuO Nanoparticles

    Directory of Open Access Journals (Sweden)

    Hyunjoon Song

    2012-11-01

    Full Text Available Recent developments in the synthesis of CuO nanoparticles (NPs and their application to the [3+2] cycloaddition of azides with terminal alkynes are reviewed. With respect to the importance of click chemistry, CuO hollow NPs, CuO hollow NPs on acetylene black, water-soluble double-hydrophilic block copolymer (DHBC nanoreactors and ZnO–CuO hybrid NPs were synthesized. Non-conventional energy sources such as microwaves and ultrasound were also applied to these click reactions, and good catalytic activity with high regioselectivity was observed. CuO hollow NPs on acetylene black can be recycled nine times without any loss of activity, and water-soluble DHBC nanoreactors have been developed for an environmentally friendly process.

  16. Solid-state polymerisation via [2+2] cycloaddition reaction involving coordination polymers.

    Science.gov (United States)

    Medishetty, Raghavender; Park, In-Hyeok; Lee, Shim Sung; Vittal, Jagadese J

    2016-03-14

    Highly crystalline metal ions containing organic polymers are potentially useful to manipulate the magnetic and optical properties to make advanced multifunctional materials. However, it is challenging to synthesise monocrystalline metal complexes of organic polymers and single-phase hybrid materials made up of both coordination and organic polymers by traditional solution crystallisation. This requires an entirely different approach in the solid-state by thermal or photo polymerisation of the ligands. Among the photochemical methods available, [2+2] cycloaddition reaction has been recently employed to generate cyclobutane based coordination polymers from the metal complexes. Cyclobutane polymers have also been integrated into coordination polymers in this way. Recent advancements in the construction of polymeric chains of cyclobutane rings through photo-dimerisation reaction in the monocrystalline solids containing metal complexes, coordination polymers and metal-organic framework structures are discussed here.

  17. Asymmetric [5+3] formal cycloadditions with cyclic enones through cascade dienamine-dienamine catalysis.

    Science.gov (United States)

    Yin, Xiang; Zheng, Yi; Feng, Xin; Jiang, Kun; Wei, Xue-Zhen; Gao, Ning; Chen, Ying-Chun

    2014-06-10

    A few aminocatalytic modes, such as iminium ions and different dienamines, have provided versatile tools for the functionalization of cyclic enones at various sites. Described here is a previously unreported cascade dienamine/dienamine catalytic pathway for β-substituted 2-cyclopentenones, and even 2-cyclohexenone. It involves domino α'-regioselective Michael addition and a γ-regioselective Mannich reaction with 3-vinyl-1,2-benzoisothiazole-1,1-dioxides to give fused or bridged architectures, which incorporate a spirocyclic skeleton, in excellent stereocontrol, thus furnishing unusual [5+3] formal cycloaddition reactions. Moreover, preliminary biological assays showed that some of the chiral products exhibited promising activity against some cancer cell lines, thus indicating that such skeletons might serve as leads in drug discovery. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Mapping Vinyl Cyanide and Other Nitriles in Titan’s Atmosphere Using ALMA

    Energy Technology Data Exchange (ETDEWEB)

    Lai, J. C.-Y.; Cordiner, M. A.; Nixon, C. A.; Achterberg, R. K.; Molter, E. M.; Palmer, M. Y.; Charnley, S. B.; Lindberg, J. E.; Mumma, M. J. [NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771 (United States); Teanby, N. A. [School of Earth Sciences, University of Bristol, Wills Memorial Building, Queen’s Road, Bristol, BS8 1RJ (United Kingdom); Kisiel, Z. [Institute of Physics, Polish Academy of Sciences, Al. Lotnikøw 32/46, 02-668 Warszawa (Poland); Irwin, P. G. J., E-mail: martin.cordiner@nasa.gov [Atmospheric, Oceanic and Planetary Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford, OX1 3PU (United Kingdom)

    2017-11-01

    Vinyl cyanide (C{sub 2}H{sub 3}CN) is theorized to form in Titan’s atmosphere via high-altitude photochemistry and is of interest regarding the astrobiology of cold planetary surfaces due to its predicted ability to form cell membrane-like structures (azotosomes) in liquid methane. In this work, we follow up on the initial spectroscopic detection of C{sub 2}H{sub 3}CN on Titan by Palmer et al. with the detection of three new C{sub 2}H{sub 3}CN rotational emission lines at submillimeter frequencies. These new, high-resolution detections have allowed for the first spatial distribution mapping of C{sub 2}H{sub 3}CN on Titan. We present simultaneous observations of C{sub 2}H{sub 5}CN, HC{sub 3}N, and CH{sub 3}CN emission, and obtain the first (tentative) detection of C{sub 3}H{sub 8} (propane) at radio wavelengths. We present disk-averaged vertical abundance profiles, two-dimensional spatial maps, and latitudinal flux profiles for the observed nitriles. Similarly to HC{sub 3}N and C{sub 2}H{sub 5}CN, which are theorized to be short-lived in Titan’s atmosphere, C{sub 2}H{sub 3}CN is most abundant over the southern (winter) pole, whereas the longer-lived CH{sub 3}CN is more concentrated in the north. This abundance pattern is consistent with the combined effects of high-altitude photochemical production, poleward advection, and the subsequent reversal of Titan’s atmospheric circulation system following the recent transition from northern to southern winter. We confirm that C{sub 2}H{sub 3}CN and C{sub 2}H{sub 5}CN are most abundant at altitudes above 200 km. Using a 300 km step model, the average abundance of C{sub 2}H{sub 3}CN is found to be 3.03 ± 0.29 ppb, with a C{sub 2}H{sub 5}CN/C{sub 2}H{sub 3}CN abundance ratio of 2.43 ± 0.26. Our HC{sub 3}N and CH{sub 3}CN spectra can be accurately modeled using abundance gradients above the tropopause, with fractional scale-heights of 2.05 ± 0.16 and 1.63 ± 0.02, respectively.

  19. Arborescent Unimolecular Micelles: Poly(γ-Benzyl l-Glutamate Core Grafted with a Hydrophilic Shell by Copper(I-Catalyzed Azide–Alkyne Cycloaddition Coupling

    Directory of Open Access Journals (Sweden)

    Mario Gauthier

    2017-10-01

    Full Text Available Amphiphilic copolymers were obtained by grafting azide-terminated polyglycidol, poly(ethylene oxide, or poly(2-hydroxyethyl acrylate chain segments onto alkyne-functionalized arborescent poly(γ-benzyl l-glutamate (PBG cores of generations G1–G3 via copper(I-catalyzed azide–alkyne Huisgen cycloaddition (CuAAC coupling. The alkyne functional groups on the arborescent PBG substrates were either distributed randomly or located exclusively at the end of the chains added in the last grafting cycle of the core synthesis. The location of these coupling sites influenced the ability of the arborescent copolymers to form unimolecular micelles in aqueous environments: The chain end grafting approach provided enhanced dispersibility in aqueous media and favored the formation of unimolecular micelles in comparison to random grafting. This is attributed to a better defined core-shell morphology for the copolymers with end-grafted shell segments. Aqueous solubility also depended on the type of material used for the shell chains. Coupling by CuAAC opens up possibilities for grafting a broad range of polymers on the arborescent substrates under mild conditions.

  20. Conversion of 2-furylcarbinols with alkyl or aryl azides to highly functionalized 1,2,3-triazoles via cascade formal [3 + 2] cycloaddition/ring-opening.

    Science.gov (United States)

    Guo, Jiawei; Yu, Binxun; Wang, Ya-Nan; Duan, Dongyu; Ren, Li-Li; Gao, Ziwei; Gou, Jing

    2014-10-03

    A Lewis acid promoted cascade cycloaddition/ring-opening of 2-furylcarbinols with alkyl or aryl azides is described. The reaction features an initial formal [3 + 2] cycloaddition to form a trisubstitued triazole motif, followed by a ring opening of furan to generate the (E)-configuration of the enone. A wide range of highly functionalized triazoles is expediently and efficiently synthesized in a highly step-economical manner.

  1. Chain-growth cycloaddition polymerization via a catalytic alkyne [2 + 2 + 2] cyclotrimerization reaction and its application to one-shot spontaneous block copolymerization.

    Science.gov (United States)

    Sugiyama, Yu-ki; Kato, Rei; Sakurada, Tetsuya; Okamoto, Sentaro

    2011-06-29

    A cobalt-catalyzed alkyne [2 + 2 + 2] cycloaddition reaction has been applied to polymerizations yielding linear polymers via selective cross-cyclotrimerization of yne-diyne monomers, which occurs in a chain-growth manner. Additionally, through control of the alkyne reactivity of the two monomers, this method was efficiently applied to the spontaneous block copolymerization of their mixture. Here we present the proposed mechanism of the catalyst transfer process of this cycloaddition polymerization.

  2. Threshold Ionization Spectroscopy of La(CH_{3}CN) and La(C_{4}H_{9}CN) Radicals Formed by la Reactions with Alkane Nitriles

    Science.gov (United States)

    Ullah, Ahamed; Kim, Jong Hyun; Cao, Wenjin; Yang, Dong-Sheng

    2017-06-01

    La atom reactions with acetonitrile (CH_{3}CN) and pentanenitrile (C_{4}H_{9}CN) are carried out in a laser-vaporization supersonic molecular beam source. Metal-containing species are observed using time-of-flight mass spectrometry. In this talk, we report the mass-analyzed threshold ionization (MATI) spectroscopic characterization of two metal-containing radicals, La(CH_{3}CN) and La(C_{4}H_{9}CN), formed by La associations with acetonitrile and pentanenitrile, respectively. Adiabatic ionization energies of the two La-alkane nitrile species and their vibrational frequencies are measured from the MATI spectra. Metal-ligand binding modes and molecular structures are investigated by comparing the spectroscopic measurements with density functional theory calculations and spectral simulations. For both alkane nitriles, the preferred La binding site is identified to be the nitrile group with a π-bind mode, the resultant metal complexes are three-membered metallacycles. While a single isomer is observed for La(CH_{3}CN), two rotational conformers are identified for La(C_{4}H_{9}CN). The binding and structures of these metal-alkane nitrile radicals are different from those formed by metal ion reactions, where metal ions were reported to favor σ binding with the nitrogen atom. K. Eller, W. Zummack, H. Schwarz, L. M. Roth, B. S. Freiser, J. Am. Chem. Soc., 1991, 113, 833-839

  3. Effect of physicochemical parameters on nitrile-hydrolyzing potentials of newly isolated nitrilase of Fusarium oxysporum f. sp. lycopercisi ED-3.

    Science.gov (United States)

    Bura Gohain, Manorama; Talukdar, Shruti; Talukdar, Madhumita; Yadav, Archana; Gogoi, Binod Kumar; Bora, Tarun Chandra; Kiran, Shashi; Gulati, Arvind

    2015-01-01

    In recent years, nitrilases from fungus have received increasing attention, and most of the studies are performed on nitrilases of bacterial origin. Frequently used methods are based on analytical methods such as high-performance liquid chromatography, liquid chromatography-mass spectrometry, and gas chromatography; therefore, an efficient, user friendly, and rapid method has been developed to screen nitrilase enzyme based on the principle of color change of a pH indicator. Phenol red amended with the minimal medium appears light yellow at neutral pH, which changes into pink with the formation of ammonia, indicating nitrilase activity in the reaction medium. A highly potent strain ED-3 identified as Fusarium oxysporum f. sp. lycopercisi (specific activity 17.5 µmol/Min/mg dcw) was isolated using this method. The nitrilase activity of F. oxysporum f. sp. lycopercisi ED-3 strain showed wide substrate specificity toward aliphatic nitriles, aromatic nitriles, and orthosubstituted heterocyclic nitriles. 4-Aminobenzonitrile was found to be a superior substrate among all the nitriles used in this study. This nitrilase was active within pH 5-10 and temperature ranging from 25 to 60 °C with optimal at pH 7.0 and temperature at 50 °C. The nitrilase activity was enhanced to several folds through optimization of culture and biotransformation conditions from 1,121 to 1,941 µmol/Min. © 2014 International Union of Biochemistry and Molecular Biology, Inc.

  4. Application of continuous stirred membrane reactor to 3-cyanopyridine bioconversion using the nitrile hydratase–amidase cascade system of Microbacterium imperiale CBS 498-74

    Czech Academy of Sciences Publication Activity Database

    Cantarella, L.; Gallifuoco, A.; Malandra, A.; Martínková, Ludmila; Pasquarelli, F.; Spera, A.; Cantarella, M.

    2010-01-01

    Roč. 47, č. 3 (2010), s. 64-70 ISSN 0141-0229 R&D Projects: GA MŠk OC09046 Institutional research plan: CEZ:AV0Z50200510 Keywords : Nitrile hydratase-amidase cascade system * 3-Cyanopyridine bioconversion * Nicotinamide Subject RIV: EE - Microbiology, Virology Impact factor: 2.287, year: 2010

  5. p-Toluenesulfonic acid mediated 1,3-dipolar cycloaddition of nitroolefins with NaN3 for synthesis of 4-aryl-NH-1,2,3-triazoles.

    Science.gov (United States)

    Quan, Xue-Jing; Ren, Zhi-Hui; Wang, Yao-Yu; Guan, Zheng-Hui

    2014-11-07

    A p-TsOH-mediated 1,3-dipolar cycloaddition of nitroolefins and sodium azide for the synthesis of 4-aryl-NH-1,2,3-triazoles has been developed. p-TsOH was discovered as a vital additive in this type of 1,3-dipolar cycloaddition. This novel cycloaddition reaction is a good method for the rapid synthesis of valuable 4-aryl-NH-1,2,3-triazoles in high yields.

  6. A new approach to produce amino-carbon nanotubes as plasmid transfection vector by [2 + 1] cycloaddition of nitrenes

    International Nuclear Information System (INIS)

    Jiang Yongjian; Jin Chen; Yang Feng; Yu Xianjun; Wang Guojian; Cheng Si; Di, Yang; Li, Ji; Fu, Deliang; N, Quanxing

    2011-01-01

    Amino-carbon nanotubes (amino-CNTs) can conjugate with the DNA by electrostatic interactions and shuttle the DNA to the cell cytoplasm or even the nucleus. Here we report a new approach to produce amino-CNTs by cycloaddition of nitrenes. Fourier transform infrared spectroscopy was used to verify the success of the functionalization, and the functionalization degree was calculated by thermal gravity analysis. Transmission electron microscope (TEM) was used to observe the solubility of the CNTs and the interactions of the amino-CNTs with the plasmids. Cell ultrathin sections were made and observed under the TEM to confirm the amino-CNTs enter the cells. Transfection experiments ultimately verify the amino-CNTs produced through cycloadditions of nitrenes can serve as plasmid vector.

  7. Characterization of a nitrilase and a nitrile hydratase from Pseudomonas sp. strain UW4 that converts indole-3-acetonitrile to indole-3-acetic acid.

    Science.gov (United States)

    Duca, Daiana; Rose, David R; Glick, Bernard R

    2014-08-01

    Indole-3-acetic acid (IAA) is a fundamental phytohormone with the ability to control many aspects of plant growth and development. Pseudomonas sp. strain UW4 is a rhizospheric plant growth-promoting bacterium that produces and secretes IAA. While several putative IAA biosynthetic genes have been reported in this bacterium, the pathways leading to the production of IAA in strain UW4 are unclear. Here, the presence of the indole-3-acetamide (IAM) and indole-3-acetaldoxime/indole-3-acetonitrile (IAOx/IAN) pathways of IAA biosynthesis is described, and the specific role of two of the enzymes (nitrilase and nitrile hydratase) that mediate these pathways is assessed. The genes encoding these two enzymes were expressed in Escherichia coli, and the enzymes were isolated and characterized. Substrate-feeding assays indicate that the nitrilase produces both IAM and IAA from the IAN substrate, while the nitrile hydratase only produces IAM. The two nitrile-hydrolyzing enzymes have very different temperature and pH optimums. Nitrilase prefers a temperature of 50°C and a pH of 6, while nitrile hydratase prefers 4°C and a pH of 7.5. Based on multiple sequence alignments and motif analyses, physicochemical properties and enzyme assays, it is concluded that the UW4 nitrilase has an aromatic substrate specificity. The nitrile hydratase is identified as an iron-type metalloenzyme that does not require the help of a P47K activator protein to be active. These data are interpreted in terms of a preliminary model for the biosynthesis of IAA in this bacterium.

  8. Copper-catalyzed azide–alkyne cycloaddition (CuAAC) and beyond: new reactivity of copper(i) acetylides†

    OpenAIRE

    Hein, Jason E.; Fokin, Valery V.

    2010-01-01

    Copper-catalyzed azide–alkyne cycloaddition (CuAAC) is a widely utilized, reliable, and straightforward way for making covalent connections between building blocks containing various functional groups. It has been used in organic synthesis, medicinal chemistry, surface and polymer chemistry, and bioconjugation applications. Despite the apparent simplicity of the reaction, its mechanism involves multiple reversible steps involving coordination complexes of copper(i) acetylides of varying nucle...

  9. Growth of Fullerene Fragments Using the Diels-Alder Cycloaddition Reaction: First Step towards a C60 Synthesis by Dimerization

    Directory of Open Access Journals (Sweden)

    Julio A. Alonso

    2013-02-01

    Full Text Available Density Functional Theory has been used to model the Diels-Alder reactions of the fullerene fragments triindenetriphenilene and pentacyclopentacorannulene with ethylene and 1,3-butadiene. The purpose is to prove the feasibility of using Diels-Alder cycloaddition reactions to grow fullerene fragments step by step, and to dimerize fullerene fragments, as a way to obtain C60. The dienophile character of the fullerene fragments is dominant, and the reaction of butadiene with pentacyclopentacorannulene is favored.

  10. Synthesis of tetrafluoroethylene- and tetrafluoroethyl-containing azides and their 1,3-dipolar cycloaddition as synthetic application

    Czech Academy of Sciences Publication Activity Database

    Voltrová, Svatava; Muselli, Mickaël; Filgas, Josef; Matoušek, V.; Klepetářová, Blanka; Beier, Petr

    2017-01-01

    Roč. 12, č. 23 (2017), s. 4962-4965 ISSN 1477-0520 EU Projects: European Commission(XE) 607787 - FLUOR21 Institutional support: RVO:61388963 Keywords : nucleophilic tetrafluoroethylation * alkyne cycloaddition * liquid crystals Subject RIV: CC - Organic Chemistry OBOR OECD: Organic chemistry Impact factor: 3.564, year: 2016 http://pubs.rsc.org/en/content/articlehtml/2017/ob/c7ob01151b

  11. Synthesis of 2-azaspiro[4.4]nonan-1-ones via phosphine-catalysed [3+2]-cycloadditions

    Energy Technology Data Exchange (ETDEWEB)

    Yong, Sarah R.; Williams, Morwenna C.; Pyne, Stephen G.; Ung, Alison T.; Skelton, Brian W.; White, Allan H.; Turner, Peter (UWA); (Wollongong); (Sydney)

    2008-10-03

    The phosphine-catalyzed [3+2]-cycloaddition of the 2-methylene {gamma}-lactams 4 and 5 and the acrylate 6 with the ylides derived from the ethyl ester, the amide or the chiral camphor sultam derivative of 2-butynoic acid (7a-c) give directly, or indirectly after reductive cyclization, spiro-heterocyclic products. The acid 32 underwent Curtius rearrangement and then acid hydrolysis to give two novel spiro-cyclic ketones, 41 and 42.

  12. Recent Advances in Recoverable Systems for the Copper-Catalyzed Azide-Alkyne Cycloaddition Reaction (CuAAC

    Directory of Open Access Journals (Sweden)

    Alessandro Mandoli

    2016-09-01

    Full Text Available The explosively-growing applications of the Cu-catalyzed Huisgen 1,3-dipolar cycloaddition reaction between organic azides and alkynes (CuAAC have stimulated an impressive number of reports, in the last years, focusing on recoverable variants of the homogeneous or quasi-homogeneous catalysts. Recent advances in the field are reviewed, with particular emphasis on systems immobilized onto polymeric organic or inorganic supports.

  13. Nanocomposites of nitrile (NBR) rubber with multi-walled carbon nanotubes

    Science.gov (United States)

    Warasitthinon, Nuthathai

    Nanotechnology offers the promise of creating new materials with enhanced performance. There are different kinds of fillers used in rubber nanocomposites, such as carbon black, silica, carbon fibers, and organoclays. Carbon nanotube reinforced elastomers have potential for improved rubber properties in aggressive environments. The first chapter is an introduction to the literature. The second chapter investigated the incorporation of multi-walled carbon nanotubes (MWCNTs) into rubber matrix for potential use in high temperature applications. The vulcanization kinetics of acrylonitrile butadiene rubber (NBR) reinforced with multi-walled carbon nanotubes was investigated. The vulcanized NBR rubber with different loading percentages of MWCNTs was also compared to NBR reinforced with carbon black N330. The optimum curing time at 170°C (T90) was found to decrease with increasing content of MWCNTs. Increased filler loading of both carbon black and MWCNTs gave higher modulus and strength. The MWCNTs filled materials gave better retention of modulus and tensile strength at high temperatures, but lower strength as compared to the carbon black filled samples. In the third chapter, carbon black (CB, 50phr) content in nitrile rubber (NBR) nanocomposites was partially replaced by multi-walled carbon nanotubes (MWCNTs). NBR/CB/CNTs nanocomposites with varying ratio of CB/CNTs (50/0 phr to 40/10 phr) were formulated via the melt-mixing method using an internal mixer. The reinforcing effect of single filler (CB) and mixture of fillers (CB and CNTs) on the properties of NBR nanocomposites was investigated. The cure kinetics and bound rubber content were analyzed using rheometry and solvent swelling method. In addition, mechanical behavior at both room temperature and high temperature (350°F/ 121°C) were examined. The scorch time and curing time values showed that there was no significant effect on the curing behavior of NBR nanocomposites after the partial replacement of CB with

  14. Quantum-Mechanical Study of the Reaction Mechanism for 2π-2π Cycloaddition of Fluorinated Methylene Groups.

    Science.gov (United States)

    Motz, Andrew R; Herring, Andrew M; Vyas, Shubham; Maupin, C Mark

    2017-07-07

    Perfluorocyclobutyl polymers are thermally and chemically stable, may be produced without a catalyst via thermal 2π-2π cycloaddition, and can form block structures, making them suitable for commercialization of specialty polymers. Thermal 2π-2π cycloaddition is a rare reaction that begins in the singlet state and proceeds through a triplet intermediate to form an energetically stable four-membered ring in the singlet state. This reaction involves two changes in spin state and, thus, two spin-crossover transitions. Presented here are density functional theory calculations that evaluate the energetics and reaction mechanisms for the dimerizations of two different polyfluorinated precursors, 1,1,2-trifluoro-2-(trifluoromethoxy)ethane and hexafluoropropylene. The spin-crossover transition states are thoroughly investigated, revealing important kinetics steps and an activation energy for the gas-phase cycloaddition of two hexafluoropropene molecules of 36.9 kcal/mol, which is in good agreement with the experimentally determined value of 34.3 kcal/mol. It is found that the first carbon-carbon bond formation is the rate-limiting step, followed by a rotation about the newly formed bond in the triplet state that results in the formation of the second carbon-carbon bond. Targeting the rotation of the C-C bond, a set of parameters were obtained that best produce high molecular weight polymers using this chemistry.

  15. Synthetic methods and reactions. XVII. Uranium hexafluoride, a convenient new oxidizing agent for organic synthesis

    International Nuclear Information System (INIS)

    Olah, G.A.; Welch, J.; Ho, T.L.

    1976-01-01

    A study was made of reactions of the highly covalent UF 6 with organic compounds. Oxidative cleavage was observed for ethers and hydrazones; oxidation or oxidative fluorination for alcohols and aldehydes; and oxidation for carboxylic acid hydrazides and N,N-dimethylalkyl(cycloalkly)amines. Reaction products and yields were tabulated for several organic compounds. The limited fluorinating ability of UF 6 did not interfere with most reactions; and inter alia, ketone, ester, amide, nitrile, and nitro groups were unaffected under the given reaction conditions

  16. Synthetic methods and reactions. XVII. Uranium hexafluoride, a convenient new oxidizing agent for organic synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Olah, G.A.; Welch, J.; Ho, T.L.

    1976-10-13

    A study was made of reactions of the highly covalent UF/sub 6/ with organic compounds. Oxidative cleavage was observed for ethers and hydrazones; oxidation or oxidative fluorination for alcohols and aldehydes; and oxidation for carboxylic acid hydrazides and N,N-dimethylalkyl(cycloalkly)amines. Reaction products and yields were tabulated for several organic compounds. The limited fluorinating ability of UF/sub 6/ did not interfere with most reactions; and inter alia, ketone, ester, amide, nitrile, and nitro groups were unaffected under the given reaction conditions. (DDA)

  17. Preparation and Sound Absorption Properties of a Barium Titanate/Nitrile Butadiene Rubber–Polyurethane Foam Composite with Multilayered Structure

    Directory of Open Access Journals (Sweden)

    Xueliang Jiang

    2018-03-01

    Full Text Available Barium titanate/nitrile butadiene rubber (BT/NBR and polyurethane (PU foam were combined to prepare a sound-absorbing material with an alternating multilayered structure. The effects of the cell size of PU foam and the alternating unit number on the sound absorption property of the material were investigated. The results show that the sound absorption efficiency at a low frequency increased when decreasing the cell size of PU foam layer. With the increasing of the alternating unit number, the material shows the sound absorption effect in a wider bandwidth of frequency. The BT/NBR-PU foam composites with alternating multilayered structure have an excellent sound absorption property at low frequency due to the organic combination of airflow resistivity, resonance absorption, and interface dissipation.

  18. Preparation and Sound Absorption Properties of a Barium Titanate/Nitrile Butadiene Rubber-Polyurethane Foam Composite with Multilayered Structure.

    Science.gov (United States)

    Jiang, Xueliang; Yang, Zhen; Wang, Zhijie; Zhang, Fuqing; You, Feng; Yao, Chu

    2018-03-22

    Barium titanate/nitrile butadiene rubber (BT/NBR) and polyurethane (PU) foam were combined to prepare a sound-absorbing material with an alternating multilayered structure. The effects of the cell size of PU foam and the alternating unit number on the sound absorption property of the material were investigated. The results show that the sound absorption efficiency at a low frequency increased when decreasing the cell size of PU foam layer. With the increasing of the alternating unit number, the material shows the sound absorption effect in a wider bandwidth of frequency. The BT/NBR-PU foam composites with alternating multilayered structure have an excellent sound absorption property at low frequency due to the organic combination of airflow resistivity, resonance absorption, and interface dissipation.

  19. Multicomponent Reaction of Z-Chlorooximes, Isocyanides, and Hydroxylamines as Hypernucleophilic Traps. A One-Pot Route to Aminodioximes and Their Transformation into 5-Amino-1,2,4-oxadiazoles by Mitsunobu-Beckmann Rearrangement.

    Science.gov (United States)

    Mercalli, Valentina; Massarotti, Alberto; Varese, Monica; Giustiniano, Mariateresa; Meneghetti, Fiorella; Novellino, Ettore; Tron, Gian Cesare

    2015-10-02

    Synthetically useful aminodioximes are prepared via a novel three-component reaction among Z-chlorooximes, isocyanides, and hydroxylamines by exploiting the preferential attack of isocyanides to nitrile N-oxides via a [3 + 1] cycloaddition reaction. The results of quantum mechanical studies of the reaction mechanism are also discussed. Furthermore, the one-pot conversion of aminodioximes to 1,2,3-oxadiazole-5-amines via Mitsunobu-Beckmann rearrangement is reported for the first time.

  20. Photo-Induced Cycloaddition Reactions of α-Diketones and Transformations of the Photocycloadducts

    Directory of Open Access Journals (Sweden)

    Yan Zhang

    2013-03-01

    Full Text Available Photocycloaddition, along with subsequent transformation of the photocycloadducts, provides expeditious ways to construct various structures. The photo-induced reactions of α-diketones have been reported to proceed via different reaction pathways with the involvement of one or two of the carbonyl groups. Photoinduced reactions of cyclic α-diketones including N-acetylisatin, phenanthrenequinone and isoquinolinetrione with different C=C containing compounds could take place via [2 + 2], [4 + 2] or [4 + 4] photocycloaddition pathways. We have investigated the photoreactions of these cyclic α-diketones with different types of alkenes and alkynes, with a focus on the unusual cascade reactions initiated by the photocycloaddition reactions of these cyclic α-diketones and the applications of these photocycloaddition reactions along with the transformation of the photocycloadducts. In this paper, we discuss the diverse photo-cycloaddition pathways found in the photocycloaddition of o-diones leading to various photocycloadducts and the potential applications of these reactions via further transformation reactions of the adducts.

  1. Structural Determinants of Alkyne Reactivity in Copper-Catalyzed Azide-Alkyne Cycloadditions

    Directory of Open Access Journals (Sweden)

    Xiaoguang Zhang

    2016-12-01

    Full Text Available This work represents our initial effort in identifying azide/alkyne pairs for optimal reactivity in copper-catalyzed azide-alkyne cycloaddition (CuAAC reactions. In previous works, we have identified chelating azides, in particular 2-picolyl azide, as “privileged” azide substrates with high CuAAC reactivity. In the current work, two types of alkynes are shown to undergo rapid CuAAC reactions under both copper(II- (via an induction period and copper(I-catalyzed conditions. The first type of the alkynes bears relatively acidic ethynyl C-H bonds, while the second type contains an N-(triazolylmethylpropargylic moiety that produces a self-accelerating effect. The rankings of reactivity under both copper(II- and copper(I-catalyzed conditions are provided. The observations on how other reaction parameters such as accelerating ligand, reducing agent, or identity of azide alter the relative reactivity of alkynes are described and, to the best of our ability, explained.

  2. Synthetic modification of hydroxychavicol by Mannich reaction and alkyne-azide cycloaddition derivatives depicting cytotoxic potential.

    Science.gov (United States)

    Kumar, Sunil; Pathania, Anoop S; Satti, Naresh K; Dutt, Parbhu; Sharma, Neha; Mallik, Fayaz A; Ali, Asif

    2015-03-06

    Here we report the design, synthesis and lead optimization of hydroxychavicol (1) a high yielding metabolite ubiquitously present in the Piper betel leaves with the significant cytotoxic activity. This is the first report to describe the synthetic strategies of two distinct series of hydroxychavicol by Mannich reaction (2-10) and alkyne-azide cycloaddition (11-20). Furthermore, all the synthesized derivatives along with parent compound were evaluated for their in-vitro cytotoxic and antiproliferative potential in several distinct cancers cell lines. Among all, the Mannich reaction derived molecules 6, 8 and 10 displayed more potent cytotoxic activities with IC50 value in a range from 3 to 9 μM, which were 7-10 fold more potent than 1 against five human cancer cell lines viz. HL-60, Mia PaCa-2, MCF-7, HEP G2 and SK-N-SH. Our results describe an efficient synthetic approach used to evaluate the structure activity relationship of 1 and its derivative in search of potential new anticancer agents. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

  3. Metal-organic organopolymeric hybrid framework by reversible [2+2] cycloaddition reaction.

    Science.gov (United States)

    Park, In-Hyeok; Chanthapally, Anjana; Zhang, Zhenjie; Lee, Shim Sung; Zaworotko, Michael J; Vittal, Jagadese J

    2014-01-07

    Organic polymers are usually amorphous or possess very low crystallinity. The metal complexes of organic polymeric ligands are also difficult to crystallize by traditional methods because of their poor solubilities and their 3D structures can not be determined by single-crystal X-ray crystallography owing to a lack of single crystals. Herein, we report the crystal structure of a 1D Zn(II) coordination polymer fused with an organic polymer ligand made in situ by a [2+2] cycloaddition reaction of a six-fold interpenetrated metal-organic framework. It is also shown that this organic polymer ligand can be depolymerized in a single-crystal-to-single-crystal (SCSC) fashion by heating. This strategy could potentially be extended to make a range of monocrystalline metal organopolymeric complexes and metal-organic organopolymeric hybrid materials. Such monocrystalline metal complexes of organic polymers have hitherto been inaccessible for materials researchers. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Computational Characterization of the Origin of Selectivity in Cycloaddition Reactions Catalyzed by Phosphoric Acid Derivatives.

    Science.gov (United States)

    Liu, Chunhui; Besora, Maria; Maseras, Feliu

    2016-02-04

    The mechanism of the organocatalyzed [4+2] cycloaddition of ο-hydroxybenzaldimines to 2,3-dihydro-2 H-furan (DHF) to form furanobenzopyrans has been investigated by using computational methods. Experiments have shown that this reaction produces different products (trans-fused or cis-fused) if different phosphoric acid derivatives are applied. Our study shows the reaction proceeds through a mechanism in which the imine re-arranges into an amine, which subsequently reacts with DHF with mediation from the catalyst. The rate-limiting step in this process is the formation of two new bonds, which is also the key step in determining the reaction selectivity. The selectivity is controlled by a balance of noncovalent interactions between the catalyst and the substrates. The discriminating factor between the two catalysts is the presence of a triflyl substituent on one of catalysts, which constraints the relative orientations of the substrates. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Computational study of the 1,3-dipolar cycloaddition between methyl 2-trifluorobutynoate and substituted azides in terms of reactivity indices and activation parameters.

    Science.gov (United States)

    Salah, Mohammed; Komiha, Najia; Kabbaj, Oum Keltoum; Ghailane, Rachida; Marakchi, Khadija

    2017-05-01

    The 1,3-dipolar cycloaddition of methyl 2-trifluorobutynoate with various azides has been studied in terms of several theoretical approaches at DFT/B3LYP/6-311++G(d,p) level of theory. The mechanism of regioselectivity of these reactions was investigated through the evaluation of the potential energy surface of the cycloaddition process calculations and density DFT-based reactivity indices. These approaches were successfully applied to prediction of preferable regio-isomers for various reactions of 1,3-dipolar cycloadditions. The reactions were followed by performing transition state optimization, calculation of Intrinsic Reaction Coordinate and activation energies. Analysis of the geometries of the corresponding transition structures shows that the cycloaddition takes place along a single elementary step (one-step mechanism) but asynchronous mechanism. The calculation of the activation energies and reaction energies show that the 1,5-regioisomer for substituted phenyl azides as dipoles and the 1,4-regioisomer for substituted benzyl azides as dipoles are thermodynamically in all the cycloadditions reactions. The solvent effect was also studied in the solvent tert-butyl alcohol using self-consistent reaction field model. The observed regioselectivity was explained by using developed DFT-based reactivity descriptors, such as Fukui and Parr functions. The results were compared with experimental data to find a good agreement. Copyright © 2017 Elsevier Inc. All rights reserved.

  6. Ln[N(SiMe3)2]3-catalyzed cycloaddition of terminal alkynes to azides leading to 1,5-disubstituted 1,2,3-triazoles: new mechanistic features.

    Science.gov (United States)

    Hong, Longcheng; Lin, Weijia; Zhang, Fangjun; Liu, Ruiting; Zhou, Xigeng

    2013-06-21

    The first example of rare earth metal-catalyzed cycloaddition of terminal alkynes to azides resulting in the formation of 1,5-disubstituted 1,2,3-triazoles is described. Preliminary studies revealed that the present cycloaddition shows unprecedented mechanistic features involving a tandem anionic cascade cyclization and anti-addition across the C≡C triple bond.

  7. An amino acid at position 142 in nitrilase from Rhodococcus rhodochrous ATCC 33278 determines the substrate specificity for aliphatic and aromatic nitriles.

    Science.gov (United States)

    Yeom, Soo-Jin; Kim, Hye-Jung; Lee, Jung-Kul; Kim, Dong-Eun; Oh, Deok-Kun

    2008-11-01

    Nitrilase from Rhodococcus rhodochrous ATCC 33278 hydrolyses both aliphatic and aromatic nitriles. Replacing Tyr-142 in the wild-type enzyme with the aromatic amino acid phenylalanine did not alter specificity for either substrate. However, the mutants containing non-polar aliphatic amino acids (alanine, valine and leucine) at position 142 were specific only for aromatic substrates such as benzonitrile, m-tolunitrile and 2-cyanopyridine, and not for aliphatic substrates. These results suggest that the hydrolysis of substrates probably involves the conjugated pi-electron system of the aromatic ring of substrate or Tyr-142 as an electron acceptor. Moreover, the mutants containing charged amino acids such as aspartate, glutamate, arginine and asparagine at position 142 displayed no activity towards any nitrile, possibly owing to the disruption of hydrophobic interactions with substrates. Thus aromaticity of substrate or amino acid at position 142 in R. rhodochrous nitrilase is required for enzyme activity.

  8. Effect of multiple alcohol-based hand rub applications on the tensile properties of thirteen brands of medical exam nitrile and latex gloves.

    Science.gov (United States)

    Gao, Pengfei; Horvatin, Matthew; Niezgoda, George; Weible, Robyn; Shaffer, Ronald

    2016-12-01

    Current CDC guidance for the disinfection of gloved hands during the doffing of personal protective equipment (PPE) following the care of a patient with Ebola recommends for multiple applications of alcohol-based hand rub (ABHR) on medical exam gloves. To evaluate possible effects of ABHR applications on glove integrity, thirteen brands of nitrile and latex medical exam gloves from five manufacturers and two different ABHRs were included in this study. A pair of gloves were worn by a test operator and the outside surfaces of the gloves were separately treated with an ABHR for 1-6 applications. Tensile strength and ultimate elongation of the gloves without any ABHR treatments (control gloves) and gloves after 1-6 ABHR applications were measured based on the ASTM D412 standard method. In general, tensile strength decreased with each ABHR application. ABHRs had more effect on the tensile strength of the tested nitrile than latex gloves, while ethanol-based ABHR (EBHR) resulted in lesser changes in tensile strength compared to isopropanol-based ABHR (IBHR). The results show that multiple EBHR applications on the latex gloves and some of the nitrile gloves tested should be safe for Ebola PPE doffing based on the CDC guidance. Appropriate hospital staff practice using ABHR treatment and doffing gloves is recommended to become more familiar with changes in glove properties.

  9. Study of nitrile-containing proton exchange membranes prepared by radiation grafting: Performance and degradation in the polymer electrolyte fuel cell

    Science.gov (United States)

    Zhang, Zhuoxiang; Jetsrisuparb, Kaewta; Wokaun, Alexander; Gubler, Lorenz

    2013-12-01

    The fuel cell performance and durability of three kinds of styrene based radiation grafted membranes are investigated and compared in the single cell. The styrene/methacrylonitrile (MAN) co-grafted membrane exhibits the best performance among the tested radiation grafted membranes. The accelerated tests under open circuit voltage (OCV) conditions and post-mortem analysis demonstrate that the nitrile-containing membranes exhibit significantly enhanced durability compared to the pure styrene grafted membrane, which is associated with the reduced gas crossover rates and attributed to the improved gases barrier properties due to the polarity of the nitrile group. To understand the influence of each functional group in the co-monomer units, both styrene/MAN and styrene/acrylonitrile (AN) co-grafted membranes are evaluated in a set of tests at OCV. The degrees of loss of the graft components are subsequently quantitatively analyzed based on FTIR spectra, showing a comparable decomposition rate of grafted styrene units, but more loss of nitrile in case of the styrene/AN co-grafted membrane. The styrene/AN co-grafted membrane, with AN lacking protection at the α-position in contrast to MAN, is found to be susceptible to significant hydrolysis, directly leading to an accelerated degradation in the late stages of the 130 h OCV test and inhomogeneous in-plane degradation.

  10. An ab initio study on the allene-isocyanic acid and ketene-vinylimine [2 + 2] cycloaddition reaction paths.

    Science.gov (United States)

    Rode, Joanna E; Dobrowolski, Jan Cz

    2006-03-16

    The reaction paths of [2 + 2] cycloadditions of allene (H2C=C=CH2) to isocyanic acid (HN=C=O) and ketene (H2C=C=O) to vinylimine (H2C=C=NH), leading to all the possible 14 four-membered ring molecules, were investigated by the MP2/aug-cc-pVDZ method. In the two considered reactions, the 2-azetidinone (beta-lactam) ring compounds were predicted to be the most stable thermodynamically in the absence of an environment. Although 4-methylene-2-azetidinone is the most stable product of the ketene-vinylimine cycloaddition, its activation barrier is higher than that for 4-methylene-2-iminooxetane by ca. 6 kcal/mol. Therefore, the latter product can be obtained owing to kinetic control. The activation barriers in the allene-isocyanic acid reactions are quite high, 50-70 kcal/mol, whereas in the course of the ketene-vinylimine cycloaddition they are equal to ca. 30-55 kcal/mol. All the reactions studied were found to be concerted and mostly asynchronous. Simulation of the solvent environment (toluene, tetrahydrofuran, acetonitrile, and water) by using Tomasi's polarized continuum model with the integral equation formalism (IEF-PCM) method showed the allene-isocyanic reactions remained concerted, yet the activation barriers were somewhat higher than those in the gas phase, whereas the ketene-vinylimine reactions became stepwise. The larger the solvent dielectric constant, the lower the activation barriers found. The lowest-energy pathways in the gas phase and in solvent were confirmed by intrinsic reaction coordinate (IRC) calculations. The atoms in molecules (AIM) analysis of the electron density distribution in the transition-state (TS) structures allowed us to distinguish pericyclic from pseudopericyclic from nonplanar-pseudopericyclic types of reactions.

  11. A DFT study on the mechanisms for the cycloaddition reactions between 1-aza-2-azoniaallene cations and acetylenes.

    Science.gov (United States)

    Wang, Jing-mei; Li, Zhi-ming; Wang, Quan-rui; Tao, Feng-gang

    2013-01-01

    The mechanisms of cycloaddition reactions between 1-aza-2-azoniaallene cations 1 and acetylenes 2 have been investigated using the global electrophilicity and nucleophilicity of the corresponding reactants as global reactivity indexes defined within the conceptual density functional theory. The reactivity and regioselectivity of these reactions were predicted by analysis of the energies, geometries, and electronic nature of the transition state structures. The theoretical results revealed that the reaction features a tandem process: an ionic 1,3-dipolar cycloaddition to produce the cycloadducts 3 H-pyrazolium salts 3 followed by a [1,2]-shift affording the thermodynamically more stable adducts 4 or 5. The mechanism of the cycloaddition reactions can be described as an asynchronous concerted pathway with reverse electron demand. The model reaction has also been investigated at the QCISD/6-31++G(d,p) and CCSD(T)/6-31++G(d,p)//B3LYP/6-31++G(d,p) levels as well as by the DFT. The polarizable continuum model, at the B3LYP/6-31++G(d,p) level of theory, was used to study solvent effects on all the studied reactions. In solvent dichloromethane, all the initial cycloadducts 3 were obtained via direct ionic process as the result of the solvent effect. The consecutive [1,2]-shift reaction, in which intermediates 3 are rearranged to the five-membered heterocycles 4/5, is proved to be a kinetically controlled reaction, and the regioselectivity can be modulated by varying the migrant. The LOL function and RDG function based on localized electron analysis were used to analysis the covalent bond and noncovalent interactions in order to unravel the mechanism of the title reactions.

  12. 1,3-Dipolar Cycloaddition (Part I: Synthesis of 1,2,3-Triazole Derivatives in Nucleoside Chemistry

    Directory of Open Access Journals (Sweden)

    Saftić D.

    2015-09-01

    Full Text Available Copper catalysed Huisgen 1,3-dipolar cycloaddition of azides and alkynes which leads to 1,4-disubstituted-1,2,3-triazoles is a frequently used method in synthetic organic chemistry. Due to the simple reaction conditions, it has occupied an important place in the field of nucleoside chemistry since it enables preparation of a large number of potentially biologically active compounds with a number of interesting additional properties induced by the presence of 1,2,3-triazole structural motif in the molecule.

  13. Facile Quenching and Spatial Patterning of Cylooctynes via Strain-Promoted Alkyne-Azide Cycloaddition of Inorganic Azides.

    Science.gov (United States)

    Bjerknes, Matthew; Cheng, Hazel; McNitt, Christopher D; Popik, Vladimir V

    2017-05-17

    Little is known about the reactivity of strain-promoted alkyne-azide cycloaddition (SPAAC) reagents with inorganic azides. We explore the reactions of a variety of popular SPAAC reagents with sodium azide and hydrozoic acid. We find that the reactions proceed in water at rates comparable to those with organic azides, yielding in all cases a triazole adduct. The azide ion's utility as a cyclooctyne quenching reagent is demonstrated by using it to spatially pattern uniformly doped hydrogels. The facile quenching of cyclooctynes demonstrated here should be useful in other bioorthogonal ligation techniques in which cyclooctynes are employed, including SPANC, Diels-Alder, and thiol-yne.

  14. Regioselectivity of vinyl sulfone based 1,3-dipolar cycloaddition reactions with sugar azides by computational and experimental studies.

    Science.gov (United States)

    Sahu, Debashis; Dey, Santu; Pathak, Tanmaya; Ganguly, Bishwajit

    2014-04-18

    DFT (M06-L) calculations on the transition state for the 1,3-dipolar cycloadditions between substituted vinyl sulfones with sugar azide have been reported in conjunction with new experimental results, and the origin of reversal of regioselectivity has been revealed using a distortion/interaction model. This study provides the scientific justification for combining organic azides with two different types of vinyl sulfones for the preparation of 1,5-disubstituted 1,2,3-triazoles and 1,4-disubstituted triazolyl esters under metal-free conditions.

  15. Control of Azomethine Cycloaddition Stereochemistry by CF3 Group: Structural Diversity of Fluorinated β-Proline Dimers.

    Science.gov (United States)

    Kudryavtsev, Konstantin V; Mantsyzov, Alexey B; Ivantcova, Polina M; Sokolov, Mikhail N; Churakov, Andrei V; Bräse, Stefan; Zefirov, Nikolay S; Polshakov, Vladimir I

    2016-09-16

    β-Proline-functionalized dimers consisting of homochiral monomeric units were synthesized by a non-peptidic coupling method for the first time. The applied synthetic methodology is based on 1,3-dipolar cycloaddition chemistry of azomethine ylides and provides absolute control over the β-proline backbone stereogenic centers. An o-(trifluoromethyl)phenyl substituent contributes to appropriate stabilization of the definite acrylamide chiral cis conformation and to achieve the dipole reactivity that is not observed for aryl groups lacking strong electronegative character.

  16. CO2 Conversion: The Potential of Porous–Organic Polymers (POPs) for the cycloaddition of CO2 and epoxides

    KAUST Repository

    Alkordi, Mohamed Helmi

    2016-03-30

    Novel porous organic polymers (POPs) have been synthesized using functionalized Cr and Co-salen complexes as molecular building blocks. The integration of metalosalen catalysts into the porous polymers backbone permits the successful utilization of the materials as solid-state catalysts for CO2-epoxide cycloadditions reactions with excellent catalytic performance under mild conditions of temperature and pressure. The catalyst proved to be fully recyclable and robust thus showing the potential of POPs as smart functional materials for the heterogenization of key catalytic elements.

  17. End-labeled amino terminated monotelechelic glycopolymers generated by ROMP and Cu(I-catalyzed azide–alkyne cycloaddition

    Directory of Open Access Journals (Sweden)

    Ronald Okoth

    2013-03-01

    Full Text Available Functionalizable monotelechelic polymers are useful materials for chemical biology and materials science. We report here the synthesis of a capping agent that can be used to terminate polymers prepared by ring-opening metathesis polymerization of norbornenes bearing an activated ester. The terminating agent is a cis-butene derivative bearing a Teoc (2-trimethylsilylethyl carbamate protected primary amine. Post-polymerization modification of the polymer was accomplished by amidation with an azido-amine linker followed by Cu(I-catalyzed azide–alkyne cycloaddition with propargyl sugars. Subsequent Teoc deprotection and conjugation with pyrenyl isothiocyanates afforded well-defined end-labeled glycopolymers.

  18. Synergistic Catalysis for the Asymmetric [3+2] Cycloaddition of Vinyl Aziridines with α,β-Unsaturated Aldehydes.

    Science.gov (United States)

    Naesborg, Line; Tur, Fernando; Meazza, Marta; Blom, Jakob; Halskov, Kim Søholm; Jørgensen, Karl Anker

    2017-01-05

    The first asymmetric [3+2] cycloaddition of vinyl aziridines with α,β-unsaturated aldehydes, based on synergistic catalysis, is disclosed. This methodology allows the formation of attractive pyrrolidine structures in good yields (up to 84 %), moderate diastereoselectivity, and high enantioselectivity values (up to >99 % ee). Additionally, a tricyclic pyrrolidine core structure found in biologically active molecules was synthesized in a one-pot fashion by using the presented reaction concept. Finally, a mechanistic proposal is outlined. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Sequential One-Pot Ruthenium-Catalyzed Azide−Alkyne Cycloaddition from Primary Alkyl Halides and Sodium Azide

    KAUST Repository

    Johansson, Johan R.

    2011-04-01

    An experimentally simple sequential one-pot RuAAC reaction, affording 1,5-disubstituted 1H-1,2,3-triazoles in good to excellent yields starting from an alkyl halide, sodium azide, and an alkyne, is reported. The organic azide is formed in situ by treating the primary alkyl halide with sodium azide in DMA under microwave heating. Subsequent addition of [RuClCp*(PPh 3) 2] and the alkyne yielded the desired cycloaddition product after further microwave irradiation. © 2011 American Chemical Society.

  20. Synthesis of Carbocyclic Hydantocidins via Regioselective and Diastereoselective Phosphine-Catalyzed [3 + 2]-Cycloadditions to 5-Methylenehydantoins

    Energy Technology Data Exchange (ETDEWEB)

    Pham, Tien Q.; Pyne, Stephen G.; Skelton, Brian W.; White, Allan H. (UWA); (Wollongong)

    2010-07-20

    The phosphine-catalyzed [3 + 2]-cycloaddition of 5-methylenehydantoins 4 with the ylides 5, derived from addition of tributylphosphine to the 2-butynoic acid derivatives, 6a-d, gives spiro-heterocyclic products. The camphor sultam derivative 6b gives optically active products. Noteable was that the ylides derived from ethyl 2-butynoate and the 3-(2-butynoyl)-1,3-oxazolidin-2-one derivatives 6c and 6d gave spiro-heterocyclic products with reverse regioselectivities. The N,N-dibenzylprotected cycloadduct has been converted to carbocyclic hydantocidin and 6,7-diepi-carbocyclic hydantocidin.

  1. A Study of the Scope and Regioselectivity of the Ruthenium-Catalyzed [3+2]-Cycloaddition of Azides with Internal Alkynes

    Science.gov (United States)

    Majireck, Max M.; Weinreb, Steven M.

    2008-01-01

    [3+2]-Cycloadditions of alkyl azides with various unsymmetrical internal alkynes in the presence of Cp*RuCl(PPh3)2 as catalyst in refluxing benzene have been examined, leading to 1,4,5-trisubstituted-1,2,3-triazoles. Whereas alkyl phenyl and dialkyl acetylenes undergo cycloadditions to afford mixtures of regioisomeric 1,2,3-triazoles, acyl-substituted internal alkynes react with complete regioselectivity. In addition, propargyl alcohols and propargyl amines were found to react with azides to afford single regioisomeric products. PMID:17064059

  2. Wear resistance and friction reduction in acrylo nitrile butadiene rubber through hybrid combination of graphite flakes and nano tungsten disulphide

    Energy Technology Data Exchange (ETDEWEB)

    Agrawal, Neha, E-mail: neha87bhu@gmail.com [Defence Material Store Research Development and Establishment (DMSRDE), DRDO, GT Road, Kanpur 208013, U.P (India); Indian Institute of Technology Bombay, Powai, Mumbai 400076, Maharashtra (India); Pandey, Akanksha; Parihar, A. S.; Mishra, A. K.; Mukhopadhyay, K.; Prasad, N. E. [Defence Material Store Research Development and Establishment (DMSRDE), DRDO, GT Road, Kanpur 208013, U.P (India); Gandhi, M. N.; Bhattacharyya, A. R. [Indian Institute of Technology Bombay, Powai, Mumbai 400076, Maharashtra (India)

    2016-05-06

    Friction and wear have considerable role in the life span of two interacting parts. Incorporation of nanofillers in polymers/elastomers matrix causes commendable changes in its tribologicalproperties. The main purpose of this work is to reduce the coefficient of friction and wear rate of Acrylo Nitrile Butadiene rubber (NBR). To achieve such objective traditionally well knownlubricants graphite(G), tungsten disulphide (WS{sub 2}) and there hybrid combination was incorporated in NBR matrix. Effect of applied load (force) and concentration of fillers on tribological properties of NBR had been studied. The filler incorporation enhanced the hardnessby 8%, showed resistance to hydraulic oil and aging effect also got improved significantly. A particular optimized concentration of NBR with hybrid combination of 2% WS{sub 2} and 4% Graphite showed minimum coefficient of friction as well as wear rate. A hypothesis could be attributed that similar lamellar structure of WS{sub 2} and Graphite along with formation of a stable nanoscale disulfide tribofilmcould result in lowering of friction. These substantially improved properties of nanoreinforced rubber materials would definitely pave promising path for plethora of potential technological applications.

  3. Transport properties of carboxylated nitrile butadiene rubber (XNBR)-nanoclay composites; a promising material for protective gloves in occupational exposures.

    Science.gov (United States)

    Mirzaei Aliabadi, Mostafa; Naderi, Ghasem; Shahtaheri, Seyed Jamaleddin; Forushani, Abbas Rahimi; Mohammadfam, Iraj; Jahangiri, Mehdi

    2014-02-28

    This study was conducted in response to one of the research needs of National Institute for Occupational Safety and Health (NIOSH), i.e. the application of nanomaterials and nanotechnology in the field of occupational safety and health. In order to fill this important knowledge gap, the equilibrium solubility and diffusion of carbon tetrachloride and ethyl acetate through carboxylated nitrile butadiene rubber (XNBR)-clay nanocomposite, as a promising new material for chemical protective gloves (or barrier against the transport of organic solvent contaminant), were examined by swelling procedure. Near Fickian diffusion was observed for XNBR based nanocomposites containing different amounts of nanoclay. Decontamination potential is a key factor in development of a new material for reusable chemical protective gloves applications, specifically for routine or highly toxic exposures. A thermal decontamination regime for nanocomposite was developed for the first time. Then, successive cycles of exposure/decontamination for nanocomposite were performed to the maximum 10 cycles for the first time. This result confirms that the two selected solvents cannot deteriorate the rubber-nanoclay interaction and, therefore, such gloves can be reusable after decontamination.

  4. Influence of gamma irradiation on mechanical and thermal properties of waste polyethylene/nitrile butadiene rubber blend

    Directory of Open Access Journals (Sweden)

    Raouf O. Aly

    2016-11-01

    Full Text Available Gamma irradiation radical–radical interaction crosslinking of elastomers and thermoplastic is a special type of crosslinking technique that has gained importance over conventional chemical crosslinking method as process is fast, pollution free, and simple. In this work a blend polymer, based on waste polyethylene and nitrile butadiene rubber, has been irradiated with gamma-rays, mechanically and thermally investigated at varying NBR content. FTIR and SEM techniques were used in addition to the swelling behavior to emphasize the blend formation. Mechanical properties like tensile strength, elongation at break and modulus at different elongations were studied and compared with those of unirradiated ones. A relatively low-radiation dose was found effective in improving the level of mechanical properties. Differential scanning calorimeter and thermogravimetric analysis were used to study the thermal characteristics of the irradiated polymer. Enhancement in thermal stability has been observed for higher NBR containing blends and via radiation-induced crosslinking up to ≈50 kGy.

  5. The improvement of the mechanical properties of PMMA denture base by Al2O3 particles with nitrile rubber

    Science.gov (United States)

    Alhareb, Ahmed Omran; Akil, Hazizan Md; Ahmad, Zainal Arifin

    2017-07-01

    Poly methyl methacrylate (PMMA) is mostly used for fabrication of denture base by heat-curing technique. Therefore, the purpose of this study is to investigate the effect of Al2O3 filler as toughening particles together with nitrile butadiene rubber (NBR) particles as impact modifier were used to reinforce PMMA denture base materials on the impact strength (IS) and fracture toughness (KIC). PMMA powder was mixed with liquid methyl methacrylate (MMA) and ethylene glycol dimethacrylate (EGDMA) as crosslinking agent. The powder components are PMMA, benzoyl peroxide, NBR (5, 7.5 and 10 wt%), and Al2O3 filler (5 wt%) treated by silane. The liquid components are 90% of methyl methacrylate and 10 % ethylene glycol dimethacryate. FTIR analyses confirmed that the Al2O3 filler was successfully treated with silane as coupling agent. The morphology of fracture surfaces was characterized using field emission scanning electron microscopy (FESEM). The results shown that IS and KIC improved significantly when using treated the Al2O3 filler. IS has increased to 56% (8.26 KJ/m2) and 73% (2.77 MPa.m1/2) for KIC when treated Al2O3 filler compared to unreinforced PMMA matrix. Statistical analyses of data results were significantly improved (P<0.05) when using 7.5 wt% NBR with treated Al2O3 filler compared to other the compositions.

  6. Ammonium acrylate biomanufacturing by an engineered Rhodococcus ruber with nitrilase overexpression and double-knockout of nitrile hydratase and amidase.

    Science.gov (United States)

    Sun, Jizhe; Yu, Huimin; Chen, Jie; Luo, Hui; Shen, Zhongyao

    2016-12-01

    Rhodococcus ruber TH was selected as a parent strain to engineer for biomanufacturing of ammonium acrylate; the characteristics of this strain included accelerated growth rate, high cell tolerance and natively overexpressed nitrile hydratase (NHase). Transcriptome analysis revealed that the transcription levels of the native NHase, amidase and nitrilase were extremely high, moderate and extremely low, respectively. Through NHase-amidase double-knockout and amidase single-knockout, the engineered strains R. ruber THdAdN and R. ruber THdA were obtained for overexpression of a heterologous nitrilase from R. rhodochrous tg1-A6 using a urea-induced Pa2 promoter. The nitrilase activity toward substrate acrylonitrile in the engineered THdAdN(Nit) reached 187.0 U/mL at 42 h, threefold of that R. rhodochrous tg1-A6 and 2.3-fold of that of THdA(Nit). The optimal catalysis temperature and pH of the nitrilases in different cells exhibited no significant difference. Using the cells as catalysts, biomanufacturing of ammonium acrylate was performed under room temperature. When catalyzed by the engineered THdAdN(Nit), the titer and productivity of ammonium acrylate dramatically increased to 741.0 g/L and 344.9 g/L/h, which are the highest results reported to date.

  7. TiCl4 promoted formal [3 + 3] cycloaddition of cyclopropane 1,1-diesters with azides: synthesis of highly functionalized triazinines and azetidines.

    Science.gov (United States)

    Zhang, Huan-Huan; Luo, Yong-Chun; Wang, Hua-Peng; Chen, Wei; Xu, Peng-Fei

    2014-09-19

    A TiCl4 promoted formal [3 + 3] cycloaddition of cyclopropane 1,1-diesters with azides has been developed for the synthesis of highly functionalized triazinines. Both stoichiometric and substoichiometric versions of this reaction were accomplished dependent on the choice of solvent. It is noteworthy that the corresponding products could be easily converted to biologically important azetidines by simple thermolysis.

  8. An asymmetric approach to bicyclo[2.2.1]heptane-1-carboxylates via a formal [4 + 2] cycloaddition reaction enabled by organocatalysis.

    Science.gov (United States)

    Fu, Jian-Guo; Shan, Yi-Fan; Sun, Wang-Bin; Lin, Guo-Qiang; Sun, Bing-Feng

    2016-06-21

    An organocatalytic formal [4 + 2] cycloaddition reaction has been realized that permits rapid access to a wide range of bicyclo[2.2.1]heptane-1-carboxylates in a highly enantioselective manner from simple starting materials under mild and operationally simple conditions.

  9. (4+2) and (2+2) Cycloadditions of Benzyne to C-60 and Zig-Zag Single-Walled Carbon Nanotubes: The Effect of the Curvature

    NARCIS (Netherlands)

    Martinez, J.P.; Langa, F.; Bickelhaupt, F.M.; Osuna, S.; Sola, M.

    2016-01-01

    Addition of benzyne to carbon nanostructures can proceed via (4 + 2) (1,4-addition) or (2 + 2) (1,2-addition) cycloadditions depending on the species under consideration. In this work, we analyze by means of density functional theory (DFT) calculations the reaction mechanisms for the (4 + 2) and (2

  10. In-depth evaluation of the cycloaddition--retro-Diels--Alder reaction for in vivo targeting with [(111)In]-DTPA-RGD conjugates.

    NARCIS (Netherlands)

    Laverman, P.; Meeuwissen, S.A.; Berkel, S.S. van; Oyen, W.J.G.; Delft, F.L. van; Rutjes, F.P.J.T.; Boerman, O.C.

    2009-01-01

    INTRODUCTION: The spontaneous copper-free tandem 1,3-dipolar cycloaddition-retro-Diels-Alder (tandem crDA) reaction between cyclic Arg-Gly-Asp-d-Phe-Orn(N(3)) [c(RGDfX)] and oxanorbornadiene-DTPA (o-DTPA) or methyloxanorbornadiene-DTPA (mo-DTPA) into two DTPA-c(RGDfX) regioisomers is characterized.

  11. Synthesis, molecular docking and biological evaluation as HDAC inhibitors of cyclopeptide mimetics by a tandem three-component reaction and intramolecular [3+2] cycloaddition.

    Science.gov (United States)

    Pirali, Tracey; Faccio, Valeria; Mossetti, Riccardo; Grolla, Ambra A; Di Micco, Simone; Bifulco, Giuseppe; Genazzani, Armando A; Tron, Gian Cesare

    2010-02-01

    Novel macrocyclic peptide mimetics have been synthesized by exploiting a three-component reaction and an azide-alkyne [3 + 2] cycloaddition. The prepared compounds were screened as HDAC inhibitors allowing us to identify a new compound with promising biological activity. In order to rationalize the biological results, computational studies have also been performed.

  12. Asymmetric Domino Aza-Michael Addition/[3+2] Cycloaddition Reactions as a Versatile Approach to alpha,beta,gamma,-Triamino Acid Derivatives

    Czech Academy of Sciences Publication Activity Database

    Kapras, Vojtěch; Pohl, Radek; Císařová, I.; Jahn, Ullrich

    2014-01-01

    Roč. 16, č. 4 (2014), s. 1088-1091 ISSN 1523-7060 Institutional support: RVO:61388963 Keywords : 1,3-dipolar cycloaddition * lithium amides * aza-Michael addition * amino acids * pyrazoles Subject RIV: CC - Organic Chemistry Impact factor: 6.364, year: 2014

  13. Traceless Azido Linker for the Solid-Phase Synthesis of NH-1,2,3-Triazoles via Cu-Catalyzed Azide-Alkyne Cycloaddition Reactions

    DEFF Research Database (Denmark)

    Cohrt, Anders Emil; Jensen, Jakob Feldthusen; Nielsen, Thomas Eiland

    2010-01-01

    A broadly useful acid-labile traceless azido linker for the solid-phase synthesis of NH-1,2,3-triazoles is presented. A variety of alkynes were efficiently immobilized on a range of polymeric supports by Cu(I)-mediated azide-alkyne cycloadditions. Supported triazoles showed excellent compatibility...

  14. Enantiodivergent synthesis of either enantiomer of ABCDE-ring analogue of antitumor antibiotic fredericamycin A via intramolecular [4 + 2] cycloaddition approach.

    Science.gov (United States)

    Akai, S; Tsujino, T; Fukuda, N; Iio, K; Takeda, Y; Kawaguchi Ki, K; Naka, T; Higuchi, K; Kita, Y

    2001-12-13

    [reaction: see text] An intramolecular enantiodivergent synthesis of both enantiomers of the ABCDE-ring analogue 22 of fredericamycin A is reported. Key steps involve an intramolecular [4 + 2] cycloaddition of 17 and an aromatic Pummerer-type reaction of 19. A lipase-catalyzed enantioselective desymmetrization of prochiral diol 2 using 1-ethoxyvinyl 2-furoate 3 led to the pivotal intermediate (R)-4.

  15. Thermally reversible single-crystal to single-crystal transformation of mononuclear to dinuclear Zn(II) complexes by [2+2] cycloaddition reaction.

    Science.gov (United States)

    Medishetty, Raghavender; Yap, Terence Teck Sheng; Koh, Lip Lin; Vittal, Jagadese J

    2013-10-25

    Two Zn(II) complexes of trans-4-styrylpyridine ligands undergo [2+2] cycloaddition reaction forming Zn(II) complex dimers in a single-crystal to single-crystal (SCSC) manner which were thermally reversible. The dimers are presumed to be the stable intermediates in the formation of 1D coordination polymers upon prolonged exposure to UV light.

  16. Reactivity of Tin(II) Guanidinate with 1,2- and 1,3-Diones: Oxidative Cycloaddition or Ligand Substitution ?

    Czech Academy of Sciences Publication Activity Database

    Chlupatý, T.; Růžičková, Z.; Horáček, Michal; Merna, J.; Alonso, M.; de Proft, F.; Růžička, A.

    2015-01-01

    Roč. 34, č. 11 (2015), s. 2202-2211 ISSN 0276-7333 Institutional support: RVO:61388955 Keywords : DENSITY-FUNCTIONAL THEORY * CRYSTAL-STRUCTURE * ADDITION-REACTIONS Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.186, year: 2015

  17. On the interactions of nitriles and fluoro-substituted pyridines with silicon tetrafluoride: Computations and thin film IR spectroscopy

    Science.gov (United States)

    Hora, Nicholas J.; Wahl, Benjamin M.; Soares, Camilla; Lara, Skylee A.; Lanska, John R.; Phillips, James A.

    2018-04-01

    The nature of the interactions between silicon tetrafluoride and series of nitrogen bases, including nitriles (RCN, with R > CH3), pyridine, and various fluoro-substituted pyridines, has been investigated via quantum-chemical computations, low-temperature IR spectroscopy, and bulk reactivity experiments. Using (primarily) M06 with the 6-311+G(2df,2pd) basis set, we obtained equilibrium structures, binding energies, harmonic frequencies, and N-Si potentials in the gas-phase and in bulk dielectric media for an extensive series of 1:1 molecular complexes, including: C6H5CH2CN-SiF4, CH3CH2CN-SiF4, (CH3)3CCN-SiF4, C5H5N-SiF4, 4-FC5H4N-SiF4, 3,5-C5F2H3N-SiF4, 2,6-C5F2H3N-SiF4 and 3,4,5-C5F3H2N-SiF4. In addition, for the analogous 2:1 complexes of pyridine and 3,5-difluororpyridine, we obtained equilibrium structures, binding energies, and harmonic frequencies. The N-Si distances in the 1:1 nitrile complexes are fairly long, ranging from 2.84 Å to 2.88 Å, and the binding energies range from 4.0 to 4.2 kcal/mol (16.7-17.6 kJ/mol). Also, computations predict extremely anharmonic N-Si potentials, for which the inner portions of the curve are preferentially stabilized in dielectric media, which predict an enhancement of these interactions in condensed-phases. However, we see no evidence of bulk reactivity between C6H5CH2CN, CH3CH2CN, or (CH3)3CCN and SiF4, nor any significant interaction between (CH3)3CCN and SiF4 in low temperature IR spectra of solid, (CH3)3CCN/SiF4 thin films. Conversely, the interactions in four of the five 1:1, pyridine-SiF4 complexes are generally stronger; binding energies range from 5.7 to 9.6 kcal/mol (23.8-40.2 kJ/mol), and correspondingly the N-Si distances are relatively short (2.12-2.25 Å). The exception is 2,6-C5F2H3N-SiF4, for which the binding energy is only 3.6 kcal/mol (15.1 kJ/mol), and the N-Si distance is quite long (3.12 Å). In addition, both pyridine and 3,5-difluororpyridine were found to form stable reaction products with SiF4

  18. Blends of nitrile butadiene rubber/poly (vinyl chloride: The use of maleated anhydride castor oil based plasticizer

    Directory of Open Access Journals (Sweden)

    Indiah Ratna Dewi

    2016-06-01

    Full Text Available Recently, much attention has been focused on research to replace petroleum-based plasticizers, with biodegradable materials, such as biopolymer which offers competitive mechanical properties. In this study, castor oil was modified with maleic anhydride (MAH to produce bioplasticizer named maleated anhydride castor oil (MACO, and used in nitrile butadiene rubber (NBR/poly vinyl chloride (PVC blend. The effect of MACO on its cure characteristics and mechanical properties of NBR/PVC blend has been determined. The reactions were carried out at different castor oil (CO/xylene ratios, i.e. 1:0 and 1:1 by weight, and fixed CO/MAH ratio, 1:3 by mole. DOP, CO, and MACO were added into each NBR/PVC blend according to the formula. It was found that the viscosity and safe process level of NBR/PVC blend is similar from all plasticizer, however, MACO (1:0 showed the highest cure rate index (CRI. MACO-based plasticizer gave a higher value of the mechanical properties of the NBR/PVC blend as compared to DOP based plasticizer. MACO (1:1 based plasticizer showed a rather significance performance compared to another type of plasticizers both before and after aging. The value of hardness, elongation at break, tensile strength, and tear strength were 96 Shore A, 155.91 %, 19.15 MPa, and 74.47 MPa, respectively. From this result, NBR/PVC blends based on MACO plasticizer can potentially replace the DOP, and therefore, making the rubber blends eco-friendly.

  19. Evidence of the Participation of Remote Residues in the Catalytic Activity of Co-Type Nitrile Hydratase from Pseudomonas putida

    Energy Technology Data Exchange (ETDEWEB)

    Brodkin, Heather R.; Novak, Walter R.P.; Milne, Amy C.; D’Aquino, J. Alejandro; Karabacak, N.M.; Goldberg, Ilana G.; Agar, Jeffrey N.; Payne, Mark S.; Petsko, Gregory A.; Ondrechen, Mary Jo; Ringe, Dagmar (Brandeis); (E.I. DuPont); (NEU)

    2011-09-28

    Active sites may be regarded as layers of residues, whereby the residues that interact directly with substrate also interact with residues in a second shell and these in turn interact with residues in a third shell. These residues in the second and third layers may have distinct roles in maintaining the essential chemical properties of the first-shell catalytic residues, particularly their spatial arrangement relative to the substrate binding pocket, and their electrostatic and dynamic properties. The extent to which these remote residues participate in catalysis and precisely how they affect first-shell residues remains unexplored. To improve our understanding of the roles of second- and third-shell residues in catalysis, we used THEMATICS to identify residues in the second and third shells of the Co-type nitrile hydratase from Pseudomonas putida (ppNHase) that may be important for catalysis. Five of these predicted residues, and three additional, conserved residues that were not predicted, have been conservatively mutated, and their effects have been studied both kinetically and structurally. The eight residues have no direct contact with the active site metal ion or bound substrate. These results demonstrate that three of the predicted second-shell residues ({alpha}-Asp164, {beta}-Glu56, and {beta}-His147) and one predicted third-shell residue ({beta}-His71) have significant effects on the catalytic efficiency of the enzyme. One of the predicted residues ({alpha}-Glu168) and the three residues not predicted ({alpha}-Arg170, {alpha}-Tyr171, and {beta}-Tyr215) do not have any significant effects on the catalytic efficiency of the enzyme.

  20. Serendipitous preparation of fac-(aceto-nitrile-κN)tri-chlorido-[(1,2,5,6-η)-cyclo-octa-1,5-diene]iridium(III).

    Science.gov (United States)

    Morris, David M; Merola, Joseph S

    2015-04-01

    A reaction between [(COD)IrCl]2 (COD is cyclo-octa-1,5-diene), HCl and indene failed to provide the hoped for chlorido-indenyliridium dimer, but instead produced the title compound, [IrCl3(CH3CN)(C8H12)], which is an octa-hedral complex of iridium(III) with a chelating cyclo-octa-1,5-diene ligand, three chloride ligands in a fac arrangement, and one aceto-nitrile ligand. Attempts to devise a rational synthesis for the title compound were unsuccessful.

  1. Silver-catalysed azide-alkyne cycloaddition (AgAAC): assessing the mechanism by density functional theory calculations

    Science.gov (United States)

    Banerji, Biswadip; Chandrasekhar, K.; Killi, Sunil Kumar; Pramanik, Sumit Kumar; Uttam, Pal; Sen, Sudeshna; Maiti, Nakul Chandra

    2016-09-01

    `Click reactions' are the copper catalysed dipolar cycloaddition reaction of azides and alkynes to incorporate nitrogens into a cyclic hydrocarbon scaffold forming a triazole ring. Owing to its efficiency and versatility, this reaction and the products, triazole-containing heterocycles, have immense importance in medicinal chemistry. Copper is the only known catalyst to carry out this reaction, the mechanism of which remains unclear. We report here that the `click reactions' can also be catalysed by silver halides in non-aqueous medium. It constitutes an alternative to the well-known CuAAC click reaction. The yield of the reaction varies on the type of counter ion present in the silver salt. This reaction exhibits significant features, such as high regioselectivity, mild reaction conditions, easy availability of substrates and reasonably good yields. In this communication, the findings of a new catalyst along with the effect of solvent and counter ions will help to decipher the still obscure mechanism of this important reaction.

  2. Synthesis with Perfect Atom Economy: Generation of Furan Derivatives by 1,3-Dipolar Cycloaddition of Acetylenedicarboxylates at Cyclooctynes

    Directory of Open Access Journals (Sweden)

    Klaus Banert

    2014-09-01

    Full Text Available Cyclooctyne and cycloocten-5-yne undergo, at room temperature, a 1,3-dipolar cycloaddition with dialkyl acetylenedicarboxylates 1a,b to generate furan-derived short-lived intermediates 2, which can be trapped by two additional equivalents of 1a,b or alternatively by methanol, phenol, water or aldehydes to yield polycyclic products 3b–d, orthoesters 4a–c, ketones 5 or epoxides 6a,b, respectively. Treatment of bis(trimethylsilyl acetylenedicarboxylate (1c with cyclooctyne leads to the ketone 7 via retro-Brook rearrangement of the dipolar intermediate 2c. In all cases, the products are formed with perfect atom economy.

  3. Ansa-metallocene polymerization catalysts derived from [2+2]cycloaddition reactions of bis(1-methylethenyl-cyclopentadienyl)zirconium systems

    Science.gov (United States)

    Paradies, Jan; Kehr, Gerald; Fröhlich, Roland; Erker, Gerhard

    2006-01-01

    Bis(1-methylethenyl-cyclopentadienyl)zirconium dichloride (7a) was prepared by a fulvene route. Photolysis at 0°C with Pyrex-filtered UV light resulted in a rapid and complete intramolecular [2+2]cycloaddition reaction to yield the corresponding cyclobutylene-bridged ansa-zirconocene dichloride isomer (8a). This is one of the rare examples of an organic functional group chemistry that leads to carbon–carbon coupling at the framework of an intact sensitive group 4 bent metallocene complex. More sterically hindered open metallocenes that bear bulky isopropyl or tert-butyl substituents at their Cp rings in addition to the active 1-methylethenyl functional group undergo the photochemical ansa-metallocene ring closure reaction equally facile. The metallocene systems used and obtained in this study have served as transition metal components for the generation of active metallocene propene polymerization catalysts. PMID:17032775

  4. Aprotic Heterocyclic Anion Triazolide Ionic Liquids - A New Class of Ionic Liquid Anion Accessed by the Huisgen Cycloaddition Reaction

    Energy Technology Data Exchange (ETDEWEB)

    Thompson, Robert [National Energy Technology Laboratory; Damodaran, Krishnan [Department of Chemistry, University of Pittsburgh; Luebke, David [National Energy Technology Laboratory; Nulwala, Hunaid [National Energy Technology Laboratory

    2013-04-18

    The triazole core is a highly versatile heterocyclic ring which can be accessed easily with the Cu(I)-catalyzed Huisgen cycloaddition reaction. Herein we present the preparation of ionic liquids that incorporate a 1,2,3-triazolide anion. These ionic liquids were prepared by a facile procedure utilizing a base-labile pivaloylmethyl group at the 1-position, which can act as precursors to 1H- 4-substituted 1,2,3-triazole. These triazoles were then subsequently converted into ionic liquids after deprotonation using an appropriate ionic liquid cation hydroxide. The densities and thermal decompositions of these ionic liquids were measured. These novel ionic liquids have potential applications in gas separations and in metal-free catalysis.

  5. Donor/Acceptor-Stabilized 1-Silaketene: Reversible [2+2] Cycloaddition with Pyridine and Evolution by an Olefin Metathesis Reaction.

    Science.gov (United States)

    Reyes, Morelia Lopez; Troadec, Thibault; Rodriguez, Ricardo; Baceiredo, Antoine; Saffon-Merceron, Nathalie; Branchadell, Vicenç; Kato, Tsuyoshi

    2016-07-11

    The reaction of silacyclopropylidene 1 with benzaldehyde generates a 1-silaketene complex 2 by a formal atomic silicon insertion into the C=O bond of the aldehyde. The highly reactive 1-silaketene 2 undergoes a reversible [2+2] cycloaddition with pyridine to give sila-β-lactam 3. Of particular interest, in the presence of 4-dimethylaminopyridine (DMAP), 1-silaketene complex 2 evolves through an intramolecular olefin metathesis reaction, generating a new 1-silaketene complex 8 and cis-stilbene. Theoretical studies suggest that the reaction proceeds through the formation of a transient silacyclobutanone, a four-membered-ring intermediate, similar to that proposed by Chauvin and co-workers for the transition-metal-based olefin metathesis. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Chelation-Assisted, Copper(II) Acetate-Accelerated Azide-Alkyne Cycloaddition

    Science.gov (United States)

    Kuang, Gui-Chao; Michaels, Heather A.; Simmons, J. Tyler; Clark, Ronald J.; Zhu, Lei

    2010-01-01

    We described in a previous communication (ref. 13) a variant of the popular CuI-catalyzed azide-alkyne cycloaddition (AAC) process where 5 mol% Cu(OAc)2 in the absence of any added reducing agent is sufficient to enable the reaction. 2-Picolylazide (1) and 2-azidomethylquinoline (2) were found to be by far the most reactive carbon azide substrates that convert to 1,2,3-triazoles in as short as a few minutes under the discovered conditions. We hypothesized that the abilities of 1 and 2 to chelate CuII contribute significantly to the observed high reaction rates. The current work examines the effect of auxiliary ligands near the azido group other than pyridyl for CuII on the efficiency of the Cu(OAc)2-accelerated AAC reaction. The carbon azides capable of binding to the catalytic copper center at the alkylated azido nitrogen in a chelatable fashion were indeed shown to be superior substrates under the reported conditions. The chelation between carbon azide 11 and CuII was demonstrated in an X-ray single crystal structure. In a limited set of examples, the ligand tris(benzyltriazolylmethyl)amine (TBTA), developed by Fokin et al. for assisting the original CuI-catalyzed AAC reactions (ref. 8), also dramatically enhances the Cu(OAc)2-accelerated AAC reactions involving non-chelating azides. This observation leads to the hypothesis of an additional effect of chelating azides on the efficiencies of Cu(OAc)2-accelerated AAC reactions, which is to facilitate the rapid reduction of CuII to highly catalytic CuI species. Mechanistic studies on the AAC reactions with particular emphasis on the role of carbon azide/copper interactions will be conducted based on the observations reported in this work. Finally, the immediate utility of the product 1,2,3-triazole molecules derived from chelating azides as multidentate metal coordination ligands is demonstrated. The resulting triazolyl-containing ligands are expected to bind with transition metal ions via the N(2) nitrogen of the 1

  7. THE DISSOCIATIVE RECOMBINATION OF PROTONATED ACRYLONITRILE, CH2CHCNH+, WITH IMPLICATIONS FOR THE NITRILE CHEMISTRY IN DARK MOLECULAR CLOUDS AND THE UPPER ATMOSPHERE OF TITAN

    International Nuclear Information System (INIS)

    Vigren, E.; Hamberg, M.; Zhaunerchyk, V.; Kaminska, M.; Thomas, R. D.; Larsson, M.; Geppert, W. D.; Millar, T. J.; Walsh, C.

    2009-01-01

    Measurements on the dissociative recombination (DR) of protonated acrylonitrile, CH 2 CHCNH + , have been performed at the heavy ion storage ring CRYRING located in the Manne Siegbahn Laboratory in Stockholm, Sweden. It has been found that at ∼2 meV relative kinetic energy about 50% of the DR events involve only ruptures of X-H bonds (where X = C or N) while the rest leads to the production of a pair of fragments each containing two heavy atoms (alongside H and/or H 2 ). The absolute DR cross section has been investigated for relative kinetic energies ranging from ∼1 meV to 1 eV. The thermal rate coefficient has been determined to follow the expression k(T) = 1.78 x 10 -6 (T/300) - 0.80 cm 3 s -1 for electron temperatures ranging from ∼10 to 1000 K. Gas-phase models of the nitrile chemistry in the dark molecular cloud TMC-1 have been run and results are compared with observations. Also, implications of the present results for the nitrile chemistry of Titan's upper atmosphere are discussed.

  8. fac-Aceto-nitrile-tricarbon-yl(di-methyl-carbamodi-thio-ato-κ2S,S')rhenium(I): crystal structure and Hirshfeld surface analysis.

    Science.gov (United States)

    Tan, Sang Loon; Lee, See Mun; Heard, Peter J; Halcovitch, Nathan R; Tiekink, Edward R T

    2017-02-01

    The title compound, [Re(C 3 H 6 NS 2 )(C 2 H 3 N)(CO) 3 ], features an octa-hedrally coordinated Re I atom within a C 3 NS 2 donor set defined by three carbonyl ligands in a facial arrangement, an aceto-nitrile N atom and two S atoms derived from a symmetrically coordinating di-thio-carbamate ligand. In the crystal, di-thio-carbamate-methyl-H⋯O(carbon-yl) inter-actions lead to supra-molecular chains along [36-1]; both di-thio-carbamate S atoms participate in intra-molecular methyl-H⋯S inter-actions. Further but weaker aceto-nitrile-C-H⋯O(carbonyl) inter-actions assemble mol-ecules in the ab plane. The nature of the supra-molecular assembly was also probed by a Hirshfeld surface analysis. Despite their weak nature, the C-H⋯O contacts are predominant on the Hirshfeld surface and, indeed, on those of related [Re(CO) 3 (C 3 H 6 NS 2 ) L ] structures.

  9. Nitrile/Buna N Material Failure Assessment for an O-Ring used on the Gaseous Hydrogen Flow Control Valve (FCV) of the Space Shuttle Main Engine

    Science.gov (United States)

    Wingard, Doug

    2006-01-01

    After the rollout of Space Shuttle Discovery in April 2005 in preparation for return-to-flight, there was a failure of the Orbiter (OV-103) helium signature leak test in the gaseous hydrogen (GH2) system. Leakage was attributed to the Flow Control Valve (FCV) in Main Engine 3. The FCV determined to be the source of the leak for OV-103 is designated as LV-58. The nitrile/Buna N rubber O-ring seal was removed from LV-58, and failure analysis indicated radial cracks providing leak paths in one quadrant. Cracks were eventually found in 6 of 9 FCV O-rings among the three Shuttle Orbiters, though none were as severe as those for LV-58, OV-103. Testing by EM10 at MSFC on all 9 FCV O- rings included: laser dimensional, Shore A hardness and properties from a dynamic mechanical analyzer (DMA) and an Instron tensile machine. The following test data was obtained on the cracked quadrant of the LV-58, OV-103 O-ring: (1) the estimated compression set was only 9.5%, compared to none for the rest of the O-ring; (2) Shore A hardness for the O.D. was higher by almost 4 durometer points than for the rest of the O-ring; and (3) DMA data showed that the storage/elastic modulus E was almost 25% lower than for the rest of the O-ring. Of the 8 FCV O-rings tested on an Instron, 4 yielded tensile strengths that were below the MIL spec requirement of 1350 psi-a likely influence of rubber cracking. Comparisons were made between values of modulus determined by DNA (elastic) and Instron (Young s). Each nitrile/Buna N O-ring used in the FCV conforms to the MIL-P-25732C specification. A number of such O-rings taken from shelf storage at MSFC and Kennedy Space Center (KSC) were used to generate a reference curve of DMA glass transition temperature (Tg) vs. shelf storage time ranging from 8 to 26 years. A similar reference curve of TGA onset temperature (of rubber weight loss) vs. shelf storage time was also generated. The DMA and TGA data for the used FCV O-rings were compared to the reference

  10. Efficient microwave assisted synthesis of novel 1,2,3-triazole-sucrose derivatives by cycloaddition reaction of sucrose azides and terminal alkynes.

    Science.gov (United States)

    Potewar, Taterao M; Petrova, Krasimira T; Barros, M Teresa

    2013-09-20

    Novel 1-(1',2,3,3',4,4',6-hepta-O-acetyl-6'-deoxy-sucros-6'-yl)-4-substituted-1,2,3-triazoles were synthesized by microwave assisted copper catalyzed 1,3-dipolar cycloaddition of sucrose derived azides with terminal alkynes in excellent yields and in short reaction times. The compound 1',2,3,3',4,4',6-hepta-O-acetyl-6'-azido-6'-deoxy-sucrose was regioselectively synthesized from sucrose by improved procedure and used for the cycloadditions. By combining carbohydrate and 1,2,3-triazole structural motifs, a library of 1,2,3-triazole-sucrose conjugates have been obtained. Copyright © 2013 Elsevier Ltd. All rights reserved.

  11. Quantum chemical study of reaction mechanism of [4+2]-cycloaddition between 2,3-dimethylbuta-1,3-diene and methyl acrylate

    Directory of Open Access Journals (Sweden)

    Yaroslav Kovalskyi

    2017-01-01

    Full Text Available The quantum-chemical modeling mechanism of the [4+2]-cycloaddition reaction of 2,3 dimethylbuta-1,3-diene and methyl acrylate was conducted. Its qualitative aspects were analyzed at the molecular level by the program MOPAC2012 and semiempirical method RM1. The potential energy surfaces of 2,3 dimethylbuta-1,3-diene and methyl acrylate [4+2] cycloaddition possible reaction pathways were constructed by restricted and unrestricted Hartree-Fock approximation. It has been established that the molecule of the final product methyl-3,4-dimethylcyclohex-3-encarboxylate has the half-chair shape, wherein the carboalkoxyl group is in the exo-orientation. Interaction between molecules of 2,3 dimethylbuta-1,3-diene and methyl acrylate occurs by a two-step mechanism more likely than one-step, since the activation parameters of this interaction maximum coincide with the experimental data.

  12. Isolation of an Eleven-Atom Polydentate Carbon-Chain Chelate Obtained by Cycloaddition of a Cyclic Osmium Carbyne with an Alkyne.

    Science.gov (United States)

    Zhu, Congqing; Zhu, Jun; Zhou, Xiaoxi; Zhu, Qin; Yang, Yuhui; Wen, Ting Bin; Xia, Haiping

    2018-03-12

    Carbon ligands have long played an important role in organometallic chemistry. However, previous examples of all-carbon chelating ligands are limited. Herein, we present a novel complex with an eleven-atom carbon chain as a polydentate chelating ligand. This species was formed by the [2+2+2] cycloaddition reaction of two equivalents of an alkyne with an osmapentalyne that contains the smallest carbyne bond angle (127.9°) ever observed. Density functional calculations revealed that electron-donating groups play a key role in the stabilization of this polydentate carbon-chain chelate. This process is also the first [2+2+2] cycloaddition reaction of an alkyne with a late-transition-metal carbyne complex. This study not only enriches the chemistry of polydentate carbon-chain chelates, but also deepens our understanding of the chelating ability of carbon ligands. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Chemoselective Switch in the Asymmetric Organocatalysis of 5 H -Oxazol-4-ones and N -Itaconimides: Addition-Protonation or [4+2] Cycloaddition

    KAUST Repository

    Zhu, Bo

    2015-12-09

    © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. We report a synthetic strategy for a chemoselective switch and a diastereo-divergent approach for the asymmetric reaction of 5H-oxazol-4-ones and N-itaconimides catalyzed by L-tert-leucine-derived tertiary amine-urea compounds. The reaction was modulated to harness either tandem conjugate addition-protonation or [4+2] cycloaddition as major product with excellent enantio- and diastereoselectivities. Subjecting the enantio-enriched cycloaddition products to a basic silica gel reagent yields the diastereomer vis-à-vis the product directly obtained under conditions for addition-protonation, thus opening a diastereo-divergent route for creating 1,3-tertiary-hetero-quaternary stereocenters. Quantum chemical studies further provide stereochemical analysis for the [4+2] process and a plausible mechanism for this chemoselective switch is proposed.

  14. Ce(OTf)₃-catalyzed [3 + 2] cycloaddition of azides with nitroolefins: regioselective synthesis of 1,5-disubstituted 1,2,3-triazoles.

    Science.gov (United States)

    Wang, Ying-Chun; Xie, Yu-Yang; Qu, Hong-En; Wang, Heng-Shan; Pan, Ying-Ming; Huang, Fu-Ping

    2014-05-16

    The first example of rare earth metal-catalyzed [3 + 2] cycloaddition of organic azides with nitroolefins and subsequent elimination reaction is described. In the presence of a catalytic amount of Ce(OTf)3, both benzyl and phenyl azides react with a broad range of aryl nitroolefins containing a range of functionalities selectively producing 1,5-disubstituted 1,2,3-triazoles in good to excellent yields.

  15. RuH2(CO)(PPh3)3 catalyzed selective formation of 1,4-disubstituted triazoles from cycloaddition of alkynes and organic azides.

    Science.gov (United States)

    Liu, Pei Nian; Siyang, Hai Xiao; Zhang, Li; Tse, Sunny Kai San; Jia, Guochen

    2012-07-06

    The ruthenium hydride complex RuH(2)(CO)(PPh(3))(3) was found to be an effective catalyst for the cycloaddition reactions of terminal alkynes and azides. In the presence of RuH(2)(CO)(PPh(3))(3), various azides reacted with a range of terminal alkynes to produce 1,4-disubstituted 1,2,3-triazoles with 100% selectivity and moderate to excellent yields.

  16. N-Heterocyclic Carbene Catalyzed [3+2] Cycloaddition of Enals with Masked Cinnamates for the Asymmetric One-Pot Synthesis of Adipic Acid Derivatives.

    Science.gov (United States)

    Chen, Xiang-Yu; Li, Sun; Sheng, He; Liu, Qiang; Jafari, Ehsan; von Essen, Carolina; Rissanen, Kari; Enders, Dieter

    2017-09-21

    A novel short entry to 3,4-disubstituted adipic acids has been developed by employing an asymmetric NHC-catalyzed [3+2] cycloaddition of enals with masked cinnammates in moderate to good yields and high stereoselectivities. The synthetic utility of the protocol was demonstrated by the basic conversion of the masked cyclopentanone intermediates to 3S,4S-disubstituted adipic acid precursors of pharmaceutically important gababutins. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. [4 + 3] Cycloadditions with Bromo-Substituted Morita-Baylis-Hillman Adducts of Isatins and N-(ortho-Chloromethyl)aryl Amides.

    Science.gov (United States)

    Zhan, Gu; Shi, Ming-Lin; He, Qing; Du, Wei; Chen, Ying-Chun

    2015-10-02

    Efficient construction of a challenging aza-spirocycloheptane oxindole scaffold is reported through an unprecedented [4 + 3] cycloaddition reaction with bromo-substituted Morita-Baylis-Hillman adducts of isatins and N-(ortho-chloromethyl)aryl amides. Both reactive intermediates, the allylic phosphonium ylides and aza-o-quinone methides, were in situ generated, chemoselectively facilitated by a Lewis base and Brønsted base, respectively.

  18. Phosphine-catalyzed highly enantioselective [3 + 3] cycloaddition of Morita-Baylis-Hillman carbonates with C,N-cyclic azomethine imines.

    Science.gov (United States)

    Zhang, Lei; Liu, Honglei; Qiao, Guanyu; Hou, Zhanfeng; Liu, Yang; Xiao, Yumei; Guo, Hongchao

    2015-04-08

    The first phosphine-catalyzed highly enantioselective [3 + 3] cycloaddition of Morita-Baylis-Hillman carbonates with C,N-cyclic azomethine imines is described. Using a spirocyclic chiral phosphine as the catalyst, a novel class of pharmaceutically interesting 4,6,7,11b-tetrahydro-1H-pyridazino[6,1-a]iso-quinoline derivatives were obtained in high yields with good to excellent diastereoselectivities and extremely excellent enantioselectivities (98->99% ee).

  19. Synthesis of novel isatin-type 5'-(4-Alkyl/Aryl-1H-1,2,3-triazoles) via 1,3-dipolar cycloaddition reactions

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Bianca N. M.; Silva, Barbara V.; Pinto, Angelo C., E-mail: biancanascimento@iq.ufrj.br [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil). Instituto de Quimica; Silva, Fernando C.; Gonzaga, Daniel T. G.; Ferreira, Vitor F. [Universidade Federal Fluminense (UFF), Niteroi, RJ (Brazil). Instituto de Quimica

    2013-02-15

    Isatin and 1H-1,2,3-triazoles are two classes of compounds with great prominence in organic synthesis and medicinal chemistry as they are heterocycle nuclei with a high reactivity allowing to obtain several compounds with important biological properties. Herein, the synthesis of novel 5'-(4-alquil/aril-1H-1,2,3-triazole)-isatin via reaction of 1,3-dipolar cycloaddition catalyzed by acetic acid is reported. (author)

  20. Enamine/enolate-mediated organocatalytic azide-carbonyl [3+2] cycloaddition reactions for the synthesis of densely functionalized 1,2,3-triazoles.

    Science.gov (United States)

    Ramasastry, Sripada S V

    2014-12-22

    Organocatalytic click! Recent advances in the metal-free enamine/enolate-mediated azide-carbonyl [3+2] cycloaddition reaction are discussed. These approaches require neither a metal catalyst nor alkyne substrates. Owing to the ready availability of carbonyl compounds, these methods thus offer excellent alternatives for the synthesis of 1,4-/1,5-disubstituted and 1,4,5-trisubstituted 1,2,3-triazoles. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Synthesis of novel nitroso acetal derivatives via tandem 6π-electrocyclization/ [3+2]-cycloaddition of 1-nitro-2-methyl-1,3 butadiene

    OpenAIRE

    Esra Koc

    2017-01-01

    Novel nitroso acetal derivatives (4-methyl-2,3,3a,6-tetrahydroisoxazolo[2,3-b][1,2]oxazine) were synthesized through 6π-electrocyclization/[3+2]-cycloaddition reaction of several dionophiles with 1-nitro-2-methyl-1,3-butadiene. Structures of the synthesized compounds were determined by 1H-NMR, 13C-NMR, IR and GC-MS analyses.

  2. Rhodium-catalyzed [5 + 2 + 1] cycloaddition of ene-vinylcyclopropanes and CO: reaction design, development, application in natural product synthesis, and inspiration for developing new reactions for synthesis of eight-membered carbocycles.

    Science.gov (United States)

    Wang, Yi; Yu, Zhi-Xiang

    2015-08-18

    Practical syntheses of natural products and their analogues with eight-membered carbocyclic skeletons are important for medicinal and biological investigations. However, methods and strategies to construct the eight-membered carbocycles are limited. Therefore, developing new methods to synthesize the eight-membered carbocycles is highly desired. In this Account, we describe our development of three rhodium-catalyzed cycloadditions for the construction of the eight-membered carbocycles, which have great potential in addressing the challenges in the synthesis of medium-sized ring systems. The first reaction described in this Account is our computationally designed rhodium-catalyzed two-component [5 + 2 + 1] cycloaddition of ene-vinylcyclopropanes (ene-VCPs) and CO for the diastereoselective construction of bi- and tricyclic cyclooctenones. The design of this reaction is based on the hypothesis that the C(sp(3))-C(sp(3)) reductive elimination of the eight-membered rhodacycle intermediate generated from the rhodium-catalyzed cyclopropane cleavage and alkene insertion, giving Wender's [5 + 2] cycloadduct, is not easy. Under CO atmosphere, CO insertion may occur rapidly, converting the eight-membered rhodacycle into a nine-membered rhodacycle, which then undergoes an easy C(sp(2))-C(sp(3)) reductive elimination process and furnishes the [5 + 2 + 1] product. This hypothesis was supported by our preliminary DFT studies and also served as inspiration for the development of two [7 + 1] cycloadditions: the [7 + 1] cycloaddition of buta-1,3-dienylcyclopropanes (BDCPs) and CO for the construction of cyclooctadienones, and the benzo/[7 + 1] cycloaddition of cyclopropyl-benzocyclobutenes (CP-BCBs) and CO to synthesize the benzocyclooctenones. The efficiency of these rhodium-catalyzed cycloadditions can be revealed by the application in natural product synthesis. Two eight-membered ring-containing natural products, (±)-asterisca-3(15),6-diene and (+)-asteriscanolide, have been

  3. 1. Progress toward the synthesis of vancosamine using a tandem [4+2]/[3+2] cycloaddition. 2. Discussion boards and pre-lecture quizzes in organic chemistry courses

    Science.gov (United States)

    Miller, Tyson A.

    The sugar vancosamine is one of the two sugar residues found on the broad spectrum antibiotic vancomycin. A strategy using a tandem intermolecular [4+2]/intermolecular [3+2] cycloaddition with nitro olefins was employed in an effort to enantioselectively synthesize the target. The [4+2] cycloaddition proceeded well with tin tetrachloride in high yield. However, the products from the [3+2] cycloaddition afforded diastereomers with stereocenters that were inconsistent with the natural product. An online facilitated group work assignment was introduced to a first semester non-majors organic chemistry lecture courses with large enrollments (˜300--660 students). Student opinion surveys, performance scores, and a detailed account of time spent by the facilitator afforded insight on the value of such assignments with large class sizes. Format and number of attempts were varied in online pre-lecture quizzes administered to a first semester non-majors organic chemistry lecture course. Student quiz performance and post-quiz assessment shows significant differences in mastery of material and class preparedness with format and number of attempts. When combined with student survey data, recommendations are made as to how format selection and number of attempts can optimize the value of online pre-lecture quizzes as a learning tool and as an assessment tool.

  4. Facile Synthesis of N-Tosyl Aza-Baylis-Hillman Adducts of Acrylamide via a Pd-Catalyzed Hydration of Nitrile to Amide

    International Nuclear Information System (INIS)

    Kim, Eun Sun; Kim, Yu Mi; Kim, Jae Nyoung

    2010-01-01

    We developed an efficient palladium-catalyzed two-step protocol for the synthesis of N-tosyl aza-Baylis-Hillman adducts of acrylamide. The method involved the preparation of the corresponding Baylis-Hillman adducts of acrylonitrile and the following Pd-catalyzed hydration of nitrile with acetaldoxime. The Baylis-Hillman reaction, which involves the coupling of activated vinyl compounds with electrophiles under the catalytic influence of a tertiary amine, gives rise to adducts, so called Baylis-Hillman adducts, with a new stereocenter and has proven to be a very useful carbon-carbon bond-forming method in the synthesis of highly functionalized molecules. As the activated vinyl compounds, various compounds have been used in the Baylis-Hillman reaction including acrylates, acrylonitrile, vinyl ketones, vinyl sulfones and acrylamides. However, among the activated vinyl compounds acrylamide has not been used much for the synthesis of the corresponding Baylis-Hillman adducts due to its sluggish reactivity

  5. Facile Synthesis of N-Tosyl Aza-Baylis-Hillman Adducts of Acrylamide via a Pd-Catalyzed Hydration of Nitrile to Amide

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Eun Sun; Kim, Yu Mi; Kim, Jae Nyoung [Chonnam National Univ., Gwangju (Korea, Republic of)

    2010-03-15

    We developed an efficient palladium-catalyzed two-step protocol for the synthesis of N-tosyl aza-Baylis-Hillman adducts of acrylamide. The method involved the preparation of the corresponding Baylis-Hillman adducts of acrylonitrile and the following Pd-catalyzed hydration of nitrile with acetaldoxime. The Baylis-Hillman reaction, which involves the coupling of activated vinyl compounds with electrophiles under the catalytic influence of a tertiary amine, gives rise to adducts, so called Baylis-Hillman adducts, with a new stereocenter and has proven to be a very useful carbon-carbon bond-forming method in the synthesis of highly functionalized molecules. As the activated vinyl compounds, various compounds have been used in the Baylis-Hillman reaction including acrylates, acrylonitrile, vinyl ketones, vinyl sulfones and acrylamides. However, among the activated vinyl compounds acrylamide has not been used much for the synthesis of the corresponding Baylis-Hillman adducts due to its sluggish reactivity.

  6. Adhesion of nitrile rubber to UV-assisted surface chemical modified PET fabric, part II: Interfacial characterization of MDI grafted PET

    Energy Technology Data Exchange (ETDEWEB)

    Razavizadeh, Mahmoud; Jamshidi, Masoud, E-mail: mjamshidi@iust.ac.ir

    2016-08-30

    Highlights: • In this research UV-irradiated PET fabric was chemically modified. • The fabric at first carboxylated under UV irradiation using glutaric anhydride, then it was grafted using isocyanate (i.e. MDI). • The surface of the fabric was characterized before and after each treating satge. • The composite samples were prepared and tested for T-Peel test. The surfaces of the fabrics were surface characterized to understand. - Abstract: Fiber to rubber adhesion is an important subject in rubber industry. It is well known that surface treatment (i.e. physical, mechanical and chemical) is an effective method to improve interfacial bonding of fibers and/or fabrics to rubbers. UV irradiation is an effective method which has been used to increase fabric-rubber interfacial interactions. In this research UV assisted chemical modification of PET fabrics was used to increase PET to nitrile rubber (NBR) adhesion. Nitrile rubber is a perfect selection as fuel and oil resistant rubber. However it has weak bonding to PET fabric. For this purpose PET fabric was carboxylated under UV irradiation and then methylenediphenyl diisocyanate (MDI) was grafted on carboxylated PET. The chemical composition of the fabric before and after surface treatment was investigated by X-ray photoelectron spectroscopy (XPS). The sectional morphology of the experimental PET fibers and the interface between rubber compound and PET fabric was studied using scanning electron microscope (SEM). The morphology and structure of the product were analyzed by an energy dispersive X-ray spectrometer (EDX). FTIR-ATR and H NMR analysis were used to assess surface modifications on the PET irradiated fabrics.

  7. Adhesion of nitrile rubber (NBR) to polyethylene terephthalate (PET) fabric. Part 1: PET surface modification by methylenediphenyl di-isocyanate (MDI)

    Energy Technology Data Exchange (ETDEWEB)

    Razavizadeh, Mahmoud; Jamshidi, Masoud, E-mail: mjamshidi@iust.ac.ir

    2016-01-01

    Graphical abstract: - Highlights: • Glutaric anhydride peroxide (GAP) was grafted on PET surface by UV irradiation method. Then MDI was attached to GAP on PET surface. • The fabric was vulcanized by nitrile rubber. • Peet test was performed after each stage of surface modification. • Curing temperature was increased and the tests were repeated. • Effect of MDI coating on PET without carboxylation was evaluated. Effect of vulcanizing temperature on this product was also studied. - Abstract: Fiber to rubber adhesion is an important subject in rubber composite industry. It is well known that surface physical, mechanical and chemical treatments are effective methods to improve interfacial bonding. Ultra violet (UV) light irradiation is an efficient method which is used to increase interfacial interactions. In this research UV assisted chemical modification of PET fabric was used to increase its bonding to nitrile rubber (NBR). NBR is perfect selection to produce fuel and oil resistant rubber parts but it has weak bonding to fabrics. For this purpose at first, the PET fabric was carboxylated under UV irradiation and then methylenediphenyl diisocyanate (MDI) was reacted and grafted to carboxylated PET. T-peel test was used to evaluate PET fabric to NBR bonding strength. Attenuated total reflectance-Fourier transform infrared spectroscopy (FTIR-AT) was used to assess surface modifications of the PET fabrics. The chemical composition of the PET surfaces before and after carboxylation and MDI grafting was investigated by X-ray photoelectron spectroscopy (XPS). It was found that at vulcanizing temperature of 150 °C, carboxylation in contrary to MDI grafting, improved considerably PET to NBR adhesion. Finally effect of curing temperature on PET to NBR bonding strength was determined. It was found that increasing vulcanizing temperature to 170 °C caused considerable improvement (about 134%) in bonding strength.

  8. Development and Applications of the Copper-Catalyzed Azide-Alkyne Cycloaddition (CuAAC as a Bioorthogonal Reaction

    Directory of Open Access Journals (Sweden)

    Li Li

    2016-10-01

    Full Text Available The emergence of bioorthogonal reactions has greatly broadened the scope of biomolecule labeling and detecting. Of all the bioorthogonal reactions that have been developed, the copper-catalyzed azide-alkyne cycloaddition (CuAAC is the most widely applied one, mainly because of its relatively fast kinetics and high efficiency. However, the introduction of copper species to in vivo systems raises the issue of potential toxicity. In order to reduce the copper-induced toxicity and further improve the reaction kinetics and efficiency, different strategies have been adopted, including the development of diverse copper chelating ligands to assist the catalytic cycle and the development of chelating azides as reagents. Up to now, the optimization of CuAAC has facilitated its applications in labeling and identifying either specific biomolecule species or on the omics level. Herein, we mainly discuss the efforts in the development of CuAAC to better fit the bioorthogonal reaction criteria and its bioorthogonal applications both in vivo and in vitro.

  9. Triphenylene discotic liquid crystal trimers synthesized by Co2(CO8-catalyzed terminal alkyne [2 + 2 + 2] cycloaddition

    Directory of Open Access Journals (Sweden)

    Bin Han

    2013-12-01

    Full Text Available The synthesis of star-shaped discotic liquid crystal trimers using Co2(CO8-catalyzed terminal alkyne [2 + 2 + 2] cycloaddition reaction is reported. The trimers consist of three triphenylene discotic units linked to a central 1,2,4-trisubstituted benzene ring via flexible spacers. The trimers were synthesized in the yields up to 70% by mixing the monomers with 10 mol % of Co2(CO8 as the catalyst in refluxing 1,4-dioxane. The liquid crystalline properties were investigated by using polarizing optical microscopy (POM, differential scanning calorimetry (DSC and X-ray diffraction (XRD. Trimer 4 with an ester connecting group and a longer spacer exhibited a rectangular columnar mesophase, while 5b and 5c possessing an ether linkage and a shorter spacer display a hexagonal columnar mesophase. The connecting functional group and the length of the flexible spacer between the central benzene ring and the triphenylene units have pivotal influence on the mesomorphism.

  10. Rapid Capture and Release of Nucleic Acids through a Reversible Photo-Cycloaddition Reaction in a Psoralen-Functionalized Hydrogel.

    Science.gov (United States)

    Zhang, Yizhe; Chan, Peggy P Y; Herr, Amy E

    2018-02-23

    Reversible immobilization of DNA and RNA is of great interest to researchers who seek to manipulate DNA or RNA in applications such as microarrays, DNA hydrogels, and gene therapeutics. However, there is no existing system that can rapidly capture and release intact nucleic acids. To meet this unmet need, we developed a functional hydrogel for rapid DNA/RNA capture and release based on the reversible photo-cycloaddition of psoralen and pyrimidines. The functional hydrogel can be easily fabricated through copolymerization of acrylamide with the synthesized allylated psoralen. The psoralen-functionalized hydrogel exhibits effective capture and release of nucleic acids spanning a wide range of lengths in a rapid fashion; over 90 % of the capture process is completed within 1 min, and circa 100 % of the release process is completed within 2 min. We observe no deleterious effects on the hybridization to the captured targets. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Occurrence of by-products of strong oxidants reacting with drinking water contaminants--scope of the problem.

    Science.gov (United States)

    Rice, R G; Gomez-Taylor, M

    1986-11-01

    This paper describes results of a detailed literature review of the organic and inorganic by-products that have been identified as being formed in aqueous solution with four of the strong oxidizing/disinfecting agents commonly employed in drinking water treatment. These agents are: chlorine, chlorine dioxide, chloramine, and ozone. Significant findings include the production of similar nonchlorinated organic oxidation products from chlorine, chlorine dioxide, and ozone. In addition, all three chlorinous oxidants/disinfectants can produce chlorinated by-products under certain conditions. The presence of chloronitrile compounds in drinking waters is indicated to arise from reactions of chlorine or chloramine to amine/amide functions in amino acids or proteinaceous materials, followed by dehydrohalogenation. These nitriles could hydrolyze to produce the corresponding chloroacetic acids. It is concluded that to minimize the presence of oxidation by-products in drinking waters, the concentrations of oxidizable organic/inorganic impurities should be lowered before any oxidizing agent is added.

  12. Synthesis of strigolactones analogues by intramolecular [2+2] cycloaddition of ketene-iminium salts to olefins and their activity on Orobanche cumana seeds.

    Science.gov (United States)

    Lachia, Mathilde; Wolf, Hanno Christian; De Mesmaeker, Alain

    2014-05-01

    Strigolactones have been the latest identified phytohormones. Among the strigolactones analogues described recently, GR-24 remains the most studied derivative which is used as standard in this field. In order to improve several properties of GR-24 for potential agronomical applications, we investigated the effect of substituents on the B and C-rings on the activity for seed germination induction. We report here the synthesis of 9 GR-24 analogues via a [2+2] intramolecular cycloaddition of ketene-iminium salts and a summary of their activity for the germination of Orobanche cumana (broomrape) seeds. Copyright © 2014 Elsevier Ltd. All rights reserved.

  13. Copper(I-Catalyzed [ 3+ 2] Cycloaddition of 3-Azidoquinoline-2,4(1H,3H-diones with Terminal Alkynes

    Directory of Open Access Journals (Sweden)

    Stanislav Kafka

    2011-05-01

    Full Text Available 3-Azidoquinoline-2,4(1H,3H-diones 1, which are readily available from 4-hydroxyquinolin-2(1H-ones 4 via 3-chloroquinoline-2,4(1H,3H-diones 5, afford, in copper(I-catalyzed [3 + 2] cycloaddition reaction with terminal acetylenes, 1,4-disubstituted 1,2,3-triazoles 3 in moderate to excellent yields. The structures of compounds 3 were confirmed by 1H and 13C-NMR spectroscopy, combustion analyses and mass spectrometry.

  14. Application of Cu(I-catalyzed azide–alkyne cycloaddition for the design and synthesis of sequence specific probes targeting double-stranded DNA

    Directory of Open Access Journals (Sweden)

    Svetlana V. Vasilyeva

    2016-06-01

    Full Text Available Efficient protocols based on Cu(I-catalyzed azide–alkyne cycloaddition were developed for the synthesis of conjugates of pyrrole–imidazole polyamide minor groove binders (MGB with fluorophores and with triplex-forming oligonucleotides (TFOs. Diverse bifunctional linkers were synthesized and used for the insertion of terminal azides or alkynes into TFOs and MGBs. The formation of stable triple helices by TFO-MGB conjugates was evaluated by gel-shift experiments. The presence of MGB in these conjugates did not affect the binding parameters (affinity and triplex stability of the parent TFOs.

  15. Synthesis of bi- and bis-1,2,3-triazoles by copper-catalyzed Huisgen cycloaddition: A family of valuable products by click chemistry

    Directory of Open Access Journals (Sweden)

    Zhan-Jiang Zheng

    2015-12-01

    Full Text Available The Cu(I-catalyzed azide-alkyne cycloaddition reaction, also known as click chemistry, has become a useful tool for the facile formation of 1,2,3-triazoles. Specifically, the utility of this reaction has been demonstrated by the synthesis of structurally diverse bi- and bis-1,2,3-triazoles. The present review focuses on the synthesis of such bi- and bistriazoles and the importance of using copper-promoted click chemistry (CuAAC for such transformations. In addition, the application of bitriazoles and the related CuAAAC reaction in different fields, including medicinal chemistry, coordination chemistry, biochemistry, and supramolecular chemistry, have been highlighted.

  16. Ultrasound-promoted organocatalytic enamine–azide [3 + 2] cycloaddition reactions for the synthesis of ((arylselanylphenyl-1H-1,2,3-triazol-4-ylketones

    Directory of Open Access Journals (Sweden)

    Gabriel P. Costa

    2017-04-01

    Full Text Available The use of sonochemistry is described in the organocatalytic enamine–azide [3 + 2] cycloaddition between 1,3-diketones and aryl azidophenyl selenides. These sonochemically promoted reactions were found to be amenable to a range of 1,3-diketones or aryl azidophenyl selenides, providing an efficient access to new ((arylselanylphenyl-1H-1,2,3-triazol-4-ylketones in good to excellent yields and short reaction times. In addition, this protocol was extended to β-keto esters, β-keto amides and α-cyano ketones. Selanyltriazoyl carboxylates, carboxamides and carbonitriles were synthesized in high yields at short times of reaction under very mild reaction conditions.

  17. KF/Al2O3 as a Recyclable Basic Catalyst for 1,3-Dipolar Cycloaddition Reaction: Synthesis of Indolizine-1-Carbonitrile Derivatives

    Directory of Open Access Journals (Sweden)

    Abaszadeh Mehdi

    2017-07-01

    Full Text Available KF/Al2O3 as a green and efficient catalyst has been used for synthesis of indolizine-1-carbonitrile derivatives. It can be proceeded by using 1,3-dipolar cycloaddition reaction of 1-alkyl-2-chloropyridinium bromides, malononitrile and benzaldehyde in ethanol, at reflux. The great advantage of this catalyst is the ease of handling. KF/Al2O3 can be used and removed by filtration, avoiding cumbersome aqueous workups and decreasing solvent waste handling issues. High conversions, short reaction times and a cleaner reaction profiles are some of the outstanding advantages of this method.

  18. A Novel One-Pot Green Synthesis of Dispirooxindolo-pyrrolidines via 1,3-Dipolar Cycloaddition Reactions of Azomethine Ylides

    Directory of Open Access Journals (Sweden)

    Abdulrahman I. Almansour

    2015-01-01

    Full Text Available A facile synthesis of dispirooxindolopyrrolidines has been accomplished via a one-pot three component 1,3-dipolar cycloaddition reaction. The reaction of azomethine ylides generated in situ from L-phenylalanine and substituted isatins with a series of unusual (E-2-oxoindolino-3-ylidene acetophenone dipolarophiles in the ionic liquid 1-butyl-3-methylimidazolium bromide [bmim]BF4, furnished the cycloadducts in good yields, with the regioisomers 5a–f being obtained with high selectivity. Furthermore, the recyclability of [bmim]BF4, up to five times, was also investigated.

  19. Synthesis of casuarine-related derivatives via 1,3-dipolar cycloaddition between a cyclic nitrone and an unsaturated gamma-lactone.

    Science.gov (United States)

    Stecko, Sebastian; Solecka, Jolanta; Chmielewski, Marek

    2009-01-26

    The 1,3-dipolar cycloaddition of the cyclic nitrone derived from tartaric acid and (S)-5-hydroxymethyl-2(5H)-furanone leads to the single adduct 7 which can be transformed into the 3-epi-1-homo-casuarine via a reaction sequence involving reduction of the lactone moiety and N-O bond hydrogenolysis, followed by intramolecular alkylation of the nitrogen atom. The adduct 7 can also be used in the synthesis of 1-methyl- or 3-methyl analogues of 3-epi-casuarine.

  20. 1,3-Dipolar cycloaddition of a cyclic nitrone derived from 2-deoxy-D-ribose to α,β-unsaturated lactones: An entry to carbapenem antibiotics.

    Science.gov (United States)

    Pieczykolan, Michał; Staszewska-Krajewska, Olga; Furman, Bartłomiej; Chmielewski, Marek

    2016-10-04

    1,3-Dipolar cycloadditions of 2-deoxy-D-ribose-derived L-threo five-membered cyclic nitrone to α,β-unsaturated γ- and δ-lactones were investigated. Cycloadducts obtained from δ-lactones, after NO bond cleavage, opening of the lactone ring, and protection of hydroxyl groups were subjected to β-lactam ring formation by using Mukaiyama's salt. Cycloadducts from γ-lactones subjected to the same reaction sequence undergo β-elimination of a water molecule to provide pyrrolidine-substituted unsaturated γ-lactones. Copyright © 2016 Elsevier Ltd. All rights reserved.

  1. γ'-Selective Functionalization of Cyclic Enones: Construction of a Chiral Quaternary Carbon Center by [4+2] Cycloaddition/Retro-Mannich Reaction with 3-Substituted Maleimides.

    Science.gov (United States)

    Zou, Chuncheng; Zeng, Chuikun; Liu, Zhen; Lu, Min; Sun, Xiaohua; Ye, Jinxing

    2016-11-07

    The first example of organocatalyzed γ'-selective functionalization of cyclic enones with 3-substituted maleimides results in the stereoselective construction quaternary carbon center is presented. The reactions provided γ'-functionalized cyclic enones and β-functionalized cyclopentenones in good to excellent yields with excellent diastereo- and enantioselectivities. DFT calculations indicated that the reaction might proceed as a [4+2] cycloaddition/retro-Mannich reaction which could explain the unexpected product with a chiral quaternary carbon center and the excellent stereoselectivity. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Facile solid-phase ruthenium assisted azide-alkyne cycloaddition (RuAAC) utilizing the Cp*RuCl(COD)-catalyst

    DEFF Research Database (Denmark)

    Engholm, Ebbe; sgz228, sgz228; Blixt, Klas Ola

    2017-01-01

    The ruthenium assisted azide-alkyne cycloaddition (RuAAC) reaction is a well-established method for the generation of 1,5- and 1,4,5-substituted 1,2,3-triazoles, which we have extended to the solid-phase synthesis of 1,2,3-triazole-peptides. The 1,2,3-triazole moieties were formed upon the reaction......-chain protection. Almost quantitative conversion to the corresponding 1,2,3-triazoles was observed within 1h....

  3. Mono and dinuclear arene ruthenium(II) triazoles by 1,3-dipolar cycloadditions to a coordinated azide in ruthenium(II) compounds

    Digital Repository Service at National Institute of Oceanography (India)

    Singh, K.S.; Svitlyk, V.; Mozharivskyj, Y.

    , crystallography. * Corresponding author; Tel: +91 0832 2450458; Fax No.: +91 0832 2450607 e-mail:keisham@nio.org or sarjitkeisham@yahoo.co.in 2 1,3-dipolar cycloaddition is a common process in organic chemistry for synthesis of 1,2,3- triazoles compounds... in triclinic space group P-1. The distance between the centroid of the C 6 Me 6 ring to ruthenium is 1.650 Å. Both the ruthenium atoms are bounded to the triazole ring through N-(2). The selected bond lengths and bond angles are presented in Table 1...

  4. An Ultra-Performance Liquid Chromatoghraphy-Tandem Mass Spectrometry (UPLC-MS/MS) Method for the Rapid and Sensitive Determination of Sulforaphane and Sulforaphane Nitrile in Brassica Vegetables

    OpenAIRE

    Alvarez Jubete, Laura; Smyth, Thomas J.; Valverde, Juan; Rai, Dilip K.; Barry-Ryan, Catherine

    2013-01-01

    A rapid UPLC-MS/MS method has been developed and validated for the simultaneous analysis of sulforaphane and sulforaphane nitrile from Brassica Oleracea L. This method was developed utilising an Acquity BEH C8 column with gradient elution combined with tandem mass spectrometry detection, using positive ion electrospray ionisation in multiple reaction monitoring (MRM) mode. The method was validated for linearity, sensitivity, precision, accuracy, matrix effects and recovery. The retention time...

  5. Oxidation of Phenol by Hydrogen Peroxide Catalyzed by Metal-Containing Poly(amidoxime Grafted Starch

    Directory of Open Access Journals (Sweden)

    Hany El-Hamshary

    2011-11-01

    Full Text Available Polyamidoxime chelating resin was obtained from polyacrylonitrile (PAN grafted starch. The nitrile groups of the starch-grafted polyacrylonitrile (St-g-PAN were converted into amidoximes by reaction with hydroxylamine under basic conditions. The synthesized graft copolymer and polyamidoxime were characterized by FTIR, TGA and elemental microanalysis. Metal chelation of the polyamidoxime resin with iron, copper and zinc has been studied. The produced metal-polyamidoxime polymer complexes were used as catalysts for the oxidation of phenol using H2O2 as oxidizing agent. The oxidation of phenol depends on the central metal ion present in the polyamidoxime complex. Reuse of M-polyamidoxime catalyst/H2O2 system showed a slight decrease in catalytic activities for all M-polyamidoxime catalysts.

  6. Oxidation of phenol by hydrogen peroxide catalyzed by metal-containing poly(amidoxime) grafted starch.

    Science.gov (United States)

    El-Hamshary, Hany; El-Newehy, Mohamed H; Al-Deyab, Salem S

    2011-11-29

    Polyamidoxime chelating resin was obtained from polyacrylonitrile (PAN) grafted starch. The nitrile groups of the starch-grafted polyacrylonitrile (St-g-PAN) were converted into amidoximes by reaction with hydroxylamine under basic conditions. The synthesized graft copolymer and polyamidoxime were characterized by FTIR, TGA and elemental microanalysis. Metal chelation of the polyamidoxime resin with iron, copper and zinc has been studied. The produced metal-polyamidoxime polymer complexes were used as catalysts for the oxidation of phenol using H(2)O(2) as oxidizing agent. The oxidation of phenol depends on the central metal ion present in the polyamidoxime complex. Reuse of M-polyamidoxime catalyst/H(2)O(2) system showed a slight decrease in catalytic activities for all M-polyamidoxime catalysts.

  7. The concern of emergence of multi-station reaction pathways that might make stepwise the mechanism of the 1,3-dipolar cycloadditions of azides and alkynes

    Science.gov (United States)

    Mohtat, Bita; Siadati, Seyyed Amir; Khalilzadeh, Mohammad Ali; Zareyee, Daryoush

    2018-03-01

    After hot debates on the concerted or stepwise nature of the mechanism of the catalyst-free 1,3-dipolar cycloadditions (DC)s, nowadays, it is being believed that for the reaction of each dipole and dipolarophile, there is a possibility that the reaction mechanism becomes stepwise, intermediates emerge, and the reaction becomes non-stereospecific. Yield of even minimal amounts of unwanted side products or stereoisomers as impurities could bring many troubles like difficult purification steps. In this project, we have made attempts to study all probable reaction channels of the azide cycloadditions with two functionalized alkynes, in order to answer this question: "is there any possibility that intermediates evolve in the catalyst-free click 1,3-DC reaction of azide-alkynes?". During the calculations, several multi-station reaction pathways supporting the stepwise and concerted mechanisms were detected. Also, the born-oppenheimer molecular dynamic (BOMD) simulation was used to find trustable geometries which could be emerged during the reaction coordinate.

  8. The Diels-Alder reaction of 4,6-dinitrobenzofuroxan with 1-trimethylsilyloxybuta-1,3-diene: a case example of a stepwise cycloaddition.

    Science.gov (United States)

    Lakhdar, Sami; Terrier, François; Vichard, Dominique; Berionni, Guillaume; El Guesmi, Nizar; Goumont, Régis; Boubaker, Taoufik

    2010-05-17

    The reaction of 4,6-dinitrobenzofuroxan (DNBF) with 1-trimethylsilyloxybuta-1,3-diene (8) is shown to afford a mixture of [2+4] diastereomeric cycloadducts (10, 11) through stepwise addition-cyclization pathways. Zwitterionic intermediate sigma-adduct 9, which is involved in the processes, has been successfully characterized by (1)H and (13)C NMR spectroscopy and UV/visible spectrophotometry in acetonitrile. A kinetic study has been carried out in this solvent that revealed that the rate of formation of 9 nicely fits the three-parameter equation log k=s(E+N) developed by Mayr to describe the feasibility of nucleophile-electrophile combinations. This significantly adds to the NMR spectroscopic evidence that the overall cycloadditions take place through a stepwise mechanism. The reaction has also been studied in dichloromethane and toluene. In these less polar solvents, the stability of 9 is not sufficient to allow direct characterization by spectroscopic methods, but a kinetic investigation supports the view that stepwise processes are still operating. An informative comparison of our reaction with previous interactions firmly identified as prototype stepwise cycloadditions is made on the basis of the global electrophilicity index, omega, defined by Parr within the density functional theory, and highlighted by Domingo et al. as a powerful tool for understanding Diels-Alder reactions.

  9. A theoretical investigation on the regioselectivity of the intramolecular hetero Diels-Alder and 1,3-dipolar cycloaddition of 2-vinyloxybenzaldehyde derivatives

    Directory of Open Access Journals (Sweden)

    Hamzehloueian Mahshid

    2014-01-01

    Full Text Available The present study reports a systematic computational analysis of the two possible pathways, fused and bridged, for an intramolecular hetero Diels-Alder (IMHDA and an intramolecular 1,3-dipolar cycloaddition (IMDCA of 2-vinyloxybenzaldehyde derivatives. The potential energy surface analysis for both reactions is in agreement with experimental observations. The activation energies associated with the two regioisomeric channels in IMHDA reaction show that the bridged product is favored, although in IMDCA, the most stable TS results the fused product. The global electronic properties of fragments within each molecule were studied to discuss the reactivity patterns and charge transfer direction in the intramolecular processes. The asynchronicity of the bond formation and aromaticity of the optimized TSs in the Diels-Alder reaction as well as cycloaddition reaction were evaluated. Finally, 1H NMR chemical shifts of the possible regioisomers have been calculated using the GIAO method which of the most stable products are in agreement with the experimental data in the both reaction.

  10. Synthesis of New 3-(2-Chloroquinolin-3-yl)-5-Phenylisoxazole Derivatives via Click-Chemistry Approach

    International Nuclear Information System (INIS)

    Fernández-Galleguillos, Carlos; Saavedra, Luis A.; Gutierrez, Margarita

    2014-01-01

    Herein, we report the synthesis of new substituted 3-(2-chloroquinolin-3-yl)-5-phenylisoxazole (3a-j) by click chemistry in good to moderate yields. This approach is based on the regioselective copper(I)-catalyzed cycloaddition between different nitrile oxides derived from 2-chloroquinoline- 3-carbaldehyde (2a-j) and phenylacetylene. Finally these derivatives were screened for their antibacterial evaluation in vitro against three Gram-negative clinical bacteria: Escherichia coli, Pseudomonas aeruginosa and Acinetobacter baumannii using standard methods. (author)

  11. Accreditation to supervise researches

    International Nuclear Information System (INIS)

    Le Gall, Thierry

    1999-01-01

    In this report, the author first proposes an overview of his academic researches and works performed within the framework of a thesis (approach to the indolizidine skeleton, synthesis of analogues of biosynthesis intermediates of leukotrienes, approach to the synthesis of compactin). In a second part, he presents and comments research works performed within the CEA: cyclo-addition of nitrile oxide with trienes complexed by tricarbonyl iron, synthesis of sulphur-containing analogues of myo-inositol, new approaches to taxol synthesis, stereo-selective synthesis with Lewis complexes of borided derived compounds, study of the bio-synthesis of biotin. The report contains lists of contributions and publications

  12. Synthesis of New 3-(2-Chloroquinolin-3-yl)-5-Phenylisoxazole Derivatives via Click-Chemistry Approach

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez-Galleguillos, Carlos; Saavedra, Luis A.; Gutierrez, Margarita [Laboratorio de Sintesis Organica, Instituto de Quimica de Recursos Naturales, Universidad de Talca (Chile)

    2014-02-15

    Herein, we report the synthesis of new substituted 3-(2-chloroquinolin-3-yl)-5-phenylisoxazole (3a-j) by click chemistry in good to moderate yields. This approach is based on the regioselective copper(I)-catalyzed cycloaddition between different nitrile oxides derived from 2-chloroquinoline- 3-carbaldehyde (2a-j) and phenylacetylene. Finally these derivatives were screened for their antibacterial evaluation in vitro against three Gram-negative clinical bacteria: Escherichia coli, Pseudomonas aeruginosa and Acinetobacter baumannii using standard methods. (author)

  13. The use of styrene-butadiene rubber waste as a potential filler in nitrile rubber: order of addition and size of waste particles

    Directory of Open Access Journals (Sweden)

    D. A. Baeta

    2009-03-01

    Full Text Available Styrene-butadiene rubber (SBR has large applications in the shoe industry, especially as expanded sheets used to produce insoles and inner soles. According to TG analysis, the rubber content in SBR residues (SBR-r was found to be around 26-wt%. Based on that data, a cost-effective technique for the reuse of SBR-r in Nitrile rubber (NBR was developed. Later, the effect of SBR-r on the cure behavior, mechanical performance, swelling, and crosslink density of reused rubber was investigated, with more emphasis placed on the effect of both particle size and loading of waste filler. Cure characteristics such as optimum cure time and scorch time were then reduced by the increasing amount of SBR-r filler. Owing to the reinforced nature of the largest particle size SBR-r, the best results for the mechanical properties of NBR were those in which SBR-r was added at the end of the cure process. The study has thus shown that SBR residue (SBR-r can be used as an economical alternative filler in NBR.

  14. The Fe-type nitrile hydratase from Comamonas testosteroni Ni1 does not require an activator accessory protein for expression in Escherichia coli

    Energy Technology Data Exchange (ETDEWEB)

    Kuhn, Misty L.; Martinez, Salette; Gumataotao, Natalie; Bornscheuer, Uwe; Liu, Dali; Holz, Richard C. (Loyola); (Greifswald)

    2012-10-10

    We report herein the functional expression of an Fe-type nitrile hydratase (NHase) without the co-expression of an activator protein or the Escherichia coli chaperone proteins GroES/EL. Soluble protein was obtained when the {alpha}- and {beta}-subunit genes of the Fe-type NHase Comamonas testosteroni Ni1 (CtNHase) were synthesized with optimized E. coli codon usage and co-expressed. As a control, the Fe-type NHase from Rhodococcus equi TG328-2 (ReNHase) was expressed with (ReNHase{sup +Act}) and without (ReNHase{sup -Act}) its activator protein, establishing that expression of a fully functional, metallated ReNHase enzyme requires the co-expression of its activator protein, similar to all other Fe-type NHase enzymes reported to date, whereas the CtNHase does not. The X-ray crystal structure of CtNHase was determined to 2.4 {angstrom} resolution revealing an {alpha}{beta} heterodimer, similar to other Fe-type NHase enzymes, except for two important differences. First, two His residues reside in the CtNHase active site that are not observed in other Fe-type NHase enzymes and second, the active site Fe(III) ion resides at the bottom of a wide solvent exposed channel. The solvent exposed active site, along with the two active site histidine residues, are hypothesized to play a role in iron incorporation in the absence of an activator protein.

  15. Composites Based on Core-Shell Structured HBCuPc@CNTs-Fe3O4 and Polyarylene Ether Nitriles with Excellent Dielectric and Mechanical Properties

    Science.gov (United States)

    Pu, Zejun; Zhong, Jiachun; Liu, Xiaobo

    2017-10-01

    Core-shell structured magnetic carbon nanotubes (CNTs-Fe3O4) coated with hyperbranched copper phthalocyanine (HBCuPc) (HBCuPc@CNTs-Fe3O4) hybrids were prepared by the solvent-thermal method. The results indicated that the HBCuPc molecules were decorated on the surface of CNTs-Fe3O4 through coordination behavior of phthalocyanines, and the CNTs-Fe3O4 core was completely coaxial wrapped by a functional intermediate HBCuPc shell. Then, polymer-based composites with a relatively high dielectric constant and low dielectric loss were fabricated by using core-shell structured HBCuPc@CNTs-Fe3O4 hybrids as fillers and polyarylene ether nitriles (PEN) as the polymer matrix. The cross-sectional scanning electron microscopy (SEM) images of composites showed that there is almost no agglomeration and internal delamination. In addition, the rheological analysis reveals that the core-shell structured HBCuPc@CNTs-Fe3O4 hybrids present better dispersion and stronger interface adhesion with the PEN matrix than CNTs-Fe3O4, thus resulting in significant improvement of the mechanical, thermal and dielectric properties of polymer-based composites.

  16. Metal-free [3+2] cycloaddition of azides with Tf2C=CH2 for the regioselective preparation of elusive 4-(trifluoromethylsulfonyl)-1,2,3-triazoles.

    Science.gov (United States)

    Alcaide, Benito; Almendros, Pedro; Lázaro-Milla, Carlos

    2015-04-25

    1,2-Dipole Tf2C=CH2 is generated in situ and immediately reacts at room temperature with an azide to afford previously unknown 4-trifluoromethanesulfonyl 1,2,3-triazoles through a stepwise [3+2] cycloaddition reaction. Noteworthily, this mild and powerful uncatalyzed protocol is highly regio- and chemoselective.

  17. [3+2] Cycloadditions of 1-halo-1-nitroethenes with (Z-C-(3,4,5-trimethoxyphenyl-N-methyl-nitrone as regio- and stereocontrolled source of novel bioactive compounds: preliminary studies

    Directory of Open Access Journals (Sweden)

    Radomir Jasiński

    2016-07-01

    Full Text Available Preliminary experiments shows, that [3+2] cycloadditions reactions proceeds with full regioselectivity and high stereoselectivity. In consequence, 3,4-trans-2-methyl-3-(3,4,5-trimethoxyphenyl-4-halo-4-nitroisoxazolidines are forming as predominantly (or sole products. Additionally, prognosis for the synthesized compounds to be potential ingredients of drugs is good.

  18. One-Pot Three-Step Synthesis of 1,2,3-Triazoles by Copper-Catalyzed Cycloaddition of Azides with Alkynes formed by a Sonogashira Cross-Coupling and Desilylation

    Science.gov (United States)

    Friscourt, Frédéric; Boons, Geert-Jan

    2010-01-01

    A microwave-assisted one-pot, three-step Sonogashira cross coupling-desilylation-cycloaddition sequence was developed for the convenient preparation of 1,4-disubstituted 1,2,3-triazoles starting from a range of halides, acyl chlorides, ethynyltrimethylsilane and azides. PMID:20942390

  19. Novel sulfonated poly(ether ether ketone)s containing nitrile groups and their composite membranes for fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Meimei; Liu, Baijun; Guan, Shaowei; Li, Long; Liu, Chang; Zhang, Yunhe; Jiang, Zhenhua [Alan G. MacDiarmid Institute, Jilin University, 2699 Qianjin Street, Changchun 130012 (China)

    2010-08-01

    A series of novel sulfonated poly(ether ether ketone)s containing a cyanophenyl group (SPEEKCNxx) are prepared based on (4-cyano)phenylhydroquinone via nucleophilic substitution polycondensation reactions. To further improve their properties, novel composite membranes composed of sulfonated poly(ether ether ketone)s containing cyanophenyl group as an acidic component and aminated poly(aryl ether ketone) as a basic component are successfully prepared. Most of the membranes exhibit excellent thermal, oxidative and dimensional stability, low-swelling ratio, high proton conductivity, low methanol permeability and high selectivity. The proton conductivities of the membranes are close to Nafion 117 at room temperature. And especially, the values of SPEEKCN40 and its composite membranes are higher than Nafion 117 at 80 C (0.17 S cm{sup -1} of Nafion, 0.26 S cm{sup -1} of SPEEKCN40, 0.20 S cm{sup -1} of SPEEKCN40-1, and 0.18 S cm{sup -1} of SPEEKCN40-2). Moreover, the methanol permeability is one order magnitude lower than that of Nafion 117. All the data prove that both copolymers and their composite membranes may be potential proton exchange membrane for fuel cells applications. (author)

  20. Tensile Properties and Integrity of Clean Room and Low-Modulus Disposable Nitrile Gloves: A Comparison of Two Dissimilar Glove Types

    Science.gov (United States)

    Phalen, Robert N.; Wong, Weng kee

    2012-01-01

    Background: The selection of disposable nitrile exam gloves is complicated by (i) the availability of several types or formulations, (ii) product variability, and (iii) an inability of common quality control tests to detect small holes in the fingers. Differences in polymer formulation (e.g. filler and plasticizer/oil content) and tensile properties are expected to account for much of the observed variability in performance. Objectives: This study evaluated the tensile properties and integrity (leak failure rates) of two glove choices assumed to contain different amounts of plasticizers/oils. The primary aims were to determine if the tensile properties and integrity differed and if associations existed among these factors. Additional physical and chemical properties were evaluated. Methods: Six clean room and five low-modulus products were evaluated using the American Society for Testing and Materials Method D412 and a modified water-leak test to detect holes capable of passing a virus or chemical agent. Results: Significant differences in the leak failure rates and tensile properties existed between the two glove types (P ≤ 0.05). The clean room gloves were about three times more likely to have leak failures (chi-square; P = 0.001). No correlation was observed between leak failures and tensile properties. Solvent extract, an indication of added plasticizer/oil, was not associated with leak failures. However, gloves with a maximum modulus gloves were a better choice for protection against aqueous chemical or biological penetration. The observed variability between glove products indicated that glove selection cannot rely solely on glove type or manufacturer labeling. Measures of modulus and AD may aid in the selection process, in contrast with common measures of tensile strength and elongation at break. PMID:22201179

  1. Overproduction of the Escherichia coli Chaperones GroEL-GroES in Rhodococcus ruber Improves the Activity and Stability of Cell Catalysts Harboring a Nitrile Hydratase.

    Science.gov (United States)

    Tian, Yuxuan; Chen, Jie; Yu, Huimin; Shen, Zhongyao

    2016-02-01

    Three combinations of molecular chaperones from Escherichia coli (i.e., DnaK-DnaJ-GrpEGroEL- GroES, GroEL-GroES, and DnaK-DnaJ-GrpE) were overproduced in E. coli BL21, and their in vitro stabilizing effects on a nitrile hydratase (NHase) were assessed. The optimal gene combination, E. coli groEL-groES (ecgroEL-ES), was introduced into Rhodococcus ruber TH3. A novel engineered strain, R. ruber TH3G was constructed with the native NHase gene on its chromosome and the heterologous ecgroEL-ES genes in a shuttle plasmid. In R. ruber TH3G, NHase activity was enhanced 37.3% compared with the control, TH3. The in vivo stabilizing effect of ecGroEL-ES on the NHase was assessed using both acrylamide immersion and heat shock experiments. The inactivation behavior of the in vivo NHase after immersion in a solution of dynamically increased concentrations of acrylamide was particularly evident. When the acrylamide concentration was increased to 500 g/l (50%), the remaining NHase activity in TH3G was 38%, but in TH3, activity was reduced to 10%. Reactivation of the in vivo NHases after varying degrees of inactivation was further assessed. The activity of the reactivated NHase was more than 2-fold greater in TH3G than in TH3. The hydration synthesis of acrylamide catalyzed by the in vivo NHase was performed with continuous acrylonitrile feeding. The final concentration of acrylamide was 640 g/l when catalyzed by TH3G, compared with 490 g/l acrylamide by TH3. This study is the first to show that the chaperones ecGroEL-ES work well in Rhodococcus and simultaneously possess protein-folding assistance functions and the ability to stabilize and reactivate the native NHases.

  2. Tensile properties and integrity of clean room and low-modulus disposable nitrile gloves: a comparison of two dissimilar glove types.

    Science.gov (United States)

    Phalen, Robert N; Wong, Weng Kee

    2012-05-01

    The selection of disposable nitrile exam gloves is complicated by (i) the availability of several types or formulations, (ii) product variability, and (iii) an inability of common quality control tests to detect small holes in the fingers. Differences in polymer formulation (e.g. filler and plasticizer/oil content) and tensile properties are expected to account for much of the observed variability in performance. This study evaluated the tensile properties and integrity (leak failure rates) of two glove choices assumed to contain different amounts of plasticizers/oils. The primary aims were to determine if the tensile properties and integrity differed and if associations existed among these factors. Additional physical and chemical properties were evaluated. Six clean room and five low-modulus products were evaluated using the American Society for Testing and Materials Method D412 and a modified water-leak test to detect holes capable of passing a virus or chemical agent. Significant differences in the leak failure rates and tensile properties existed between the two glove types (P ≤ 0.05). The clean room gloves were about three times more likely to have leak failures (chi-square; P = 0.001). No correlation was observed between leak failures and tensile properties. Solvent extract, an indication of added plasticizer/oil, was not associated with leak failures. However, gloves with a maximum modulus <4 MPa or area density (AD) <11 g cm(-2) were about four times less likely to leak. On average, the low-modulus gloves were a better choice for protection against aqueous chemical or biological penetration. The observed variability between glove products indicated that glove selection cannot rely solely on glove type or manufacturer labeling. Measures of modulus and AD may aid in the selection process, in contrast with common measures of tensile strength and elongation at break.

  3. Cyclic Multiblock Copolymers via Combination of Iterative Cu(0)-Mediated Radical Polymerization and Cu(I)-Catalyzed Azide-Alkyne Cycloaddition Reaction.

    Science.gov (United States)

    Xiao, Lifen; Zhu, Wen; Chen, Jiqiang; Zhang, Ke

    2017-02-01

    Cyclic multiblock polymers with high-order blocks are synthesized via the combination of single-electron transfer living radical polymerization (SET-LRP) and copper-catalyzed azide-alkyne cycloaddition (CuAAC). The linear α,ω-telechelic multiblock copolymer is prepared via SET-LRP by sequential addition of different monomers. The SET-LRP approach allows well control of the block length and sequence as A-B-C-D-E, etc. The CuAAC is then performed to intramolecularly couple the azide and alkyne end groups of the linear copolymer and produce the corresponding cyclic copolymer. The block sequence and the cyclic topology of the resultant cyclic copolymer are confirmed by the characterization of 1 H nuclear magnetic resonance spectroscopy, gel permeation chromatography, Fourier transform infrared spectroscopy, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. A green, multicomponent, regio- and stereo-selective 1,3-dipolar cycloaddition of azides and azomethine ylides generated in situ with bifunctional dipolarophiles using PEG-400.

    Science.gov (United States)

    Sindhu, Jayant; Singh, Harjinder; Khurana, J M

    2014-05-01

    A series of novel dispiropyrrolidine-linked 1,2,3-triazole derivatives have been prepared by one-pot, four-component protocol that employed 5-arylidene-3-(prop-2-ynyl)thiazolidine-2,4-dione, isatin, sarcosine and substituted azides using Cu(I) generated in situ as catalyst in PEG-400 as a highly efficient and green media. This is the first report of a four-component reaction involving a classical Huisgen reaction, in which the two dipolar moieties (substituted azides and in situ generated azomethine ylides) react with acetylenic and olefinic dipolarophiles, respectively. The 1,3-dipolar cycloaddition proceeds in a highly regio- and stereo-selective manner. This methodology can be an ideal tool for the preparation of biologically important five-membered heterocyclic compounds in one pot.

  5. Etude d'une séquence allylmétallation-cycloaddition contrôlée par un groupe silyle

    OpenAIRE

    Distelmans, Anouk

    2004-01-01

    Notre thèse s'intéresse à l'étude de séquences réactionnelles permeettant la création de carbones quaternaires. Deux séquences de réactions sont envisagées : - La première s'inscrit dans le prolongement des travaux de J-M. Adam et combine une réaction d'allylmétallation asymétrique et une réaction de cycloaddition [2+2] intramoléculaire. Elle conduit à des cyclobutanones bicycliques portant un substituant méthyle en tête de pont. La réaction d'allylmétallation a tout d'abord été étud...

  6. Tandem synthesis of novel 4-(azidocarbonylphenylazide from 3-(4-hydrazinocarbonylphenylsydnone and its chemoselective 1,3 dipolar cycloaddition reaction and Curtius rearrangement

    Directory of Open Access Journals (Sweden)

    Prashant R. Latthe

    2011-01-01

    Full Text Available C The 4-(azidocarbonylphenylazide 3 obtained from 4-(hydrazinocarbonyl phenylsydnone 1 by tandem hydrolysis – diazotisation, is used as the key intermediate for the chemoselective one-pot 1,3- dipolar cycloaddition reaction with dimethylacetylene dicarboxylate (DMAD along with Curtius rearrangement affording the carbamates 5a-c and the isocyanate 6. These compounds were further used as building blocks for the triheterocyclic carbamates 9a-c and 10a-c and 4- triazolophenylaryl ureas 7a-f. The ethyl carbamate derivative 5a exhibited antibacterial inhibition selectively against B.subtilis almost one and half times more than Norfloxacin while compounds 5a, 7b and 10c were as active as Griseofulvin against A.flavus

  7. In situ vibrational spectroscopic investigation of C4 hydrocarbon selective oxidation over vanadium-phosphorus-oxide catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Xue, Zhi -Yang [Iowa State Univ., Ames, IA (United States)

    1999-05-10

    n-Butane selective oxidation over the VPO catalyst to maleic anhydride is the first and only commercialized process of light alkane selective oxidation. The mechanism of this reaction is still not well known despite over twenty years of extensive studies, which can partially be attributed to the extreme difficulties to characterize catalytic reactions real-time under typical reaction conditions. In situ spectroscopic characterization techniques such as Infrared spectroscopy and laser Raman spectroscopy were used in the current mechanistic investigations of n-butane oxidation over VPO catalysts. To identify the reaction intermediates, oxidation of n-butane, 1,3-butadiene and related oxygenates on the VPO catalyst were monitored using FTIR spectroscopy under transient conditions. n-Butane was found to adsorb on the VPO catalyst to form olefinic species, which were further oxidized to unsaturated, noncyclic carbonyl species. The open chain dicarbonyl species then experienced cycloaddition to form maleic anhydride. VPO catalyst phase transformations were investigated using in situ laser Raman spectroscopy. This report contains Chapter 1: General introduction; Chapter 2: Literature review; and Chapter 5: Conclusion and recommendations.

  8. Bottom-up electrochemical preparation of solid-state carbon nanodots directly from nitriles/ionic liquids using carbon-free electrodes and the applications in specific ferric ion detection and cell imaging.

    Science.gov (United States)

    Niu, Fushuang; Xu, Yuanhong; Liu, Mengli; Sun, Jing; Guo, Pengran; Liu, Jingquan

    2016-03-14

    Carbon nanodots (C-dots), a new type of potential alternative to conventional semiconductor quantum dots, have attracted numerous attentions in various applications including bio-chemical sensing, cell imaging, etc., due to their chemical inertness, low toxicity and flexible functionalization. Various methods including electrochemical (EC) methods have been reported for the synthesis of C-dots. However, complex procedures and/or carbon source-containing electrodes are often required. Herein, solid-state C-dots were simply prepared by bottom-up EC carbonization of nitriles (e.g. acetonitrile) in the presence of an ionic liquid [e.g. 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6)], using carbon-free electrodes. Due to the positive charges of BMIM(+) on the C-dots, the final products presented in a precipitate form on the cathode, and the unreacted nitriles and BMIMPF6 can be easily removed by simple vacuum filtration. The as-prepared solid-state C-dots can be well dispersed in an aqueous medium with excellent photoluminescence properties. The average size of the C-dots was found to be 3.02 ± 0.12 nm as evidenced by transmission electron microscopy. Other techniques such as UV-vis spectroscopy, fluorescence spectroscopy, X-ray photoelectron spectroscopy and atomic force microscopy were applied for the characterization of the C-dots and to analyze the possible generation mechanism. These C-dots have been successfully applied in efficient cell imaging and specific ferric ion detection.

  9. Multiconfiguration Self-Consistent Field Study on Formonitrile Imine and N-Substituted Nitrile Imines HCN2-R: Energy Component Analysis of the Pseudo-Jahn-Teller Effect.

    Science.gov (United States)

    Toyota, Azumao; Muramatsu, Takashi; Koseki, Shiro

    2017-03-23

    Stable geometrical structures for formonitrile imine (1) and N-substituted nitrile imines HCN 2 -R (R = Li, BeH, BH 2 , CH 3 , CN, CCH, C 6 H 5 , NH 2 , OH, and F) (2-11) were examined by using the multiconfiguration self-consistent-field (MCSCF) method followed by second-order configuration interaction (SOCI) calculations and second-order multiconfiguration quasi-degenerate perturbation theory (MCQDPT2) calculations, together with the aug-cc-pVTZ basis sets. The results show that 1 suffers a pseudo-Jahn-Teller (JT) distortion from a linear C ∞v structure to a C 1 structure via a planar bent C s structure. Each of the others is found to undergo pseudo-JT distortion from a symmetrical structure to a planar bent C s structure for 2, 3, and 7 and to a C 1 structure for 4, 5, 6, 8, 9, 10, and 11. At the stationary structures of 1-11, the structural characteristics were briefly discussed in terms of allenic and propargylic. To elucidate the nature of pseudo-JT distortions, energy component analyses were carried out at the MCSCF+SOCI level of theory at all of the stationary structures for the relevant molecules. In most of the molecules examined, pseudo-JT stabilizations were classified into two groups, one in which the stability arises from a lowering of the energy of the attractive term V en and the other in which the stability results from a lowering of the energy of the repulsive terms V nn and V ee . In addition to the above two groups, it was also found that the following three groups are responsible for the pseudo-JT stabilizations in a certain stage of the structural changes. Namely, one is a lowering of the energy of the term V ee observed in 6, another is a lowering of the energy of the terms V ee and V en observed in 9-11, and the other is a lowering of the energy of the terms V en and V nn observed in 10. These energetic behaviors were accounted in terms of an elongation or a contraction of the molecular skeleton, a migration of electrons from one part of

  10. Rh(I-catalyzed intramolecular [2 + 2 + 1] cycloaddition of allenenes: Construction of bicyclo[4.3.0]nonenones with an angular methyl group and tricyclo[6.4.0.01,5]dodecenone

    Directory of Open Access Journals (Sweden)

    Chisato Mukai

    2011-04-01

    Full Text Available The [RhCl(COdppp]2-catalyzed intramolecular carbonylative [2 + 2 + 1] cycloaddition of allenenes was developed to prepare bicyclo[4.3.0]nonenones possessing a methyl group at the ring junction, which is difficult to achieve by the Pauson–Khand reaction of the corresponding enynes. This method also provided a new procedure for the construction of the tricyclo[6.4.0.01,5]dodecenone framework in a satisfactory yield.

  11. Fine-Tuning Strain and Electronic Activation of Strain-Promoted 1,3-Dipolar Cycloadditions with Endocyclic Sulfamates in SNO-OCTs.

    Science.gov (United States)

    Burke, Eileen G; Gold, Brian; Hoang, Trish T; Raines, Ronald T; Schomaker, Jennifer M

    2017-06-14

    The ability to achieve predictable control over the polarization of strained cycloalkynes can influence their behavior in subsequent reactions, providing opportunities to increase both rate and chemoselectivity. A series of new heterocyclic strained cyclooctynes containing a sulfamate backbone (SNO-OCTs) were prepared under mild conditions by employing ring expansions of silylated methyleneaziridines. SNO-OCT derivative 8 outpaced even a difluorinated cyclooctyne in a 1,3-dipolar cycloaddition with benzylazide. The various orbital interactions of the propargylic and homopropargylic heteroatoms in SNO-OCT were explored both experimentally and computationally. The inclusion of these heteroatoms had a positive impact on stability and reactivity, where electronic effects could be utilized to relieve ring strain. The choice of the heteroatom combinations in various SNO-OCTs significantly affected the alkyne geometries, thus illustrating a new strategy for modulating strain via remote substituents. Additionally, this unique heteroatom activation was capable of accelerating the rate of reaction of SNO-OCT with diazoacetamide over azidoacetamide, opening the possibility of further method development in the context of chemoselective, bioorthogonal labeling.

  12. A Teaching Experiment to Elucidate a Cation-π Effect in an Alkyne Cycloaddition Reaction and Illustrate Hypothesis Driven Design of Experiments.

    Science.gov (United States)

    St Germain, Elijah J; Horowitz, Andrew S; Rucco, Dominic; Rezler, Evonne M; Lepore, Salvatore D

    2017-02-14

    An organic chemistry experiment is described that is based on recent research to elucidate a novel cation-π interaction between tetraalkammonium cations and propargyl hydrazines. This non-bonded interaction is a key component of the mechanism of ammonium-catalyzed intramolecular cycloaddition of nitrogen to the terminal carbon of a C-C triple bond of the propargyl substrate. In this teaching experiment, reactions and control experiments are employed to demonstrate the testing of two alternative mechanistic hypotheses. Specifically, cyclization reactions are performed with a soluble base (sodium phenoxide) with and without tetrabutylammonium bromide under homogeneous conditions. Students observe that the added ammonium salt accelerates the reaction. They are then encouraged to develop a testable hypothesis for the role of the ammonium salt in the cyclization mechanism: typical phase transfer or other. IR spectroscopy is then used to directly observe a dose dependent shift of the alkyne stretching mode due to a cation-π interaction. In this experiment, undergraduate "researchers" were able to practice the scientific method on a contemporary system and see how data are generated and interpreted to adjudicate between rival hypotheses in a way that emulates authentic and current research in a lab setting. This experimental design was tested on students enrolled in the introductory undergraduate Organic Chemistry Lab.

  13. (2 + 2) Cycloaddition of Benzyne to Endohedral Metallofullerenes M3N@C80 (M = Sc, Y): A Rotating-Intermediate Mechanism.

    Science.gov (United States)

    Yang, Tao; Nagase, Shigeru; Akasaka, Takeshi; Poblet, Josep M; Houk, K N; Ehara, Masahiro; Zhao, Xiang

    2015-06-03

    The reaction mechanism and origin of regioselectivity of (2 + 2) cycloadditions of benzyne to endohedral metallofullerenes M3N@C80 (M = Sc, Y) were investigated with density functional calculations. The reaction was demonstrated to follow a diradical mechanism rather than a carbene mechanism, in which the formation of the diradical intermediate is the rate-determining step. Through rotation of benzyne moiety on the fullerene surface, the diradical intermediate on 566 site could isomerize to two new diradical intermediates which give rise to two distinct [5,6] and [6,6] benzoadducts, respectively. However, the diradical intermediate on 666 site only produces the [6,6] benzoadduct. The nature of the endohedral cluster not only influences the regioselectivity, but also determines the cycloadduct geometry. For Sc3N@C80, the [5,6] benzoadduct is preferred kinetically and thermodynamically, whereas in the case of Y3N@C80, both [5,6] and [6,6] benzoadducts are favorable. In contrast to closed-cage benzoadducts of Sc3N@C80, Y3N@C80 affords open-cage benzoadducts, making it the first example that the endohedral cluster could alter cycloadducts from the closed cage to open cage. With further analysis, it is revealed that the origin of regioselectivity results from the local strain energy of the fullerene cage.

  14. Metal-Free Poly-Cycloaddition of Activated Azide and Alkynes toward Multifunctional Polytriazoles: Aggregation-Induced Emission, Explosive Detection, Fluorescent Patterning, and Light Refraction.

    Science.gov (United States)

    Wu, Yongwei; He, Benzhao; Quan, Changyun; Zheng, Chao; Deng, Haiqin; Hu, Rongrong; Zhao, Zujin; Huang, Fei; Qin, Anjun; Tang, Ben Zhong

    2017-09-01

    The metal-free click polymerization (MFCP) of activated alkynes and azides or activated azide and alkynes have been developed into powerful techniques for the construction of polytriazoles without the obsession of metallic catalyst residues problem. However, the MFCP of activated azides and alkynes is rarely applied in preparation of functional polytriazoles. In this paper, soluble multifunctional polytriazoles (PIa and PIb) with high weight-average molecular weights (M w up to 32 000) are prepared via the developed metal-free poly-cycloaddition of activated azide and alkynes in high yields (up to 90%). The resultant PIa and PIb are thermally stable, and show aggregation-induced emission characteristics, enabling their aggregates to detect explosives with superamplification effect. Moreover, thanks to their containing aromatic rings and polar moieties, PIa and PIb exhibit high refractive indices. In addition, they can also be cross-linked upon UV irradiation to generate 2D fluorescent patterning due to their remaining azide groups and containing ester groups. Thus, these multifunctional polytriazoles are potentially applicable in the optoelectronic and sensing fields. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Photo-Mediated Copper(I)-Catalyzed Azide-Alkyne Cycloaddition (CuAAC) "Click" Reactions for Forming Polymer Networks as Shape Memory Materials.

    Science.gov (United States)

    McBride, Matthew K; Gong, Tao; Nair, Devatha P; Bowman, Christopher N

    2014-11-05

    The formation of polymer networks polymerized with the Copper (I) - catalyzed azide - alkyne cycloaddition (CuAAC) click reaction is described along with their accompanying utilization as shape memory polymers. Due to the click nature of the reaction and the synthetic accessibility of azide and alkyne functional-monomers, the polymer architecture was readily controlled through monomer design to manipulate crosslink density, ability for further functionalization, and the glass transition temperature (55 to 120°C). Free strain recovery is used to quantify the shape memory properties of a model CuAAC network resulting in excellent shape fixity and recovery of 99%. The step growth nature of this polymerization results in homogenous network formation with narrow glass transitions ranges having half widths of the transition close to 15°C for these materials resulting in shape recovery sharpness of 3.9 %/°C in a model system comparable to similarly crosslinked chain growth polymers. Utilization of the CuAAC reaction to form shape memory materials opens a range of possibilities and behaviors that are not readily achieved in other shape memory materials such as (meth) acrylates, thiolene, thiol-Michael, and poly(caprolactone) based shape memory materials.

  16. Photo-Mediated Copper(I)-Catalyzed Azide-Alkyne Cycloaddition (CuAAC) “Click” Reactions for Forming Polymer Networks as Shape Memory Materials

    Science.gov (United States)

    McBride, Matthew K.; Gong, Tao; Nair, Devatha P.; Bowman, Christopher N.

    2014-01-01

    The formation of polymer networks polymerized with the Copper (I) – catalyzed azide – alkyne cycloaddition (CuAAC) click reaction is described along with their accompanying utilization as shape memory polymers. Due to the click nature of the reaction and the synthetic accessibility of azide and alkyne functional-monomers, the polymer architecture was readily controlled through monomer design to manipulate crosslink density, ability for further functionalization, and the glass transition temperature (55 to 120°C). Free strain recovery is used to quantify the shape memory properties of a model CuAAC network resulting in excellent shape fixity and recovery of 99%. The step growth nature of this polymerization results in homogenous network formation with narrow glass transitions ranges having half widths of the transition close to 15°C for these materials resulting in shape recovery sharpness of 3.9 %/°C in a model system comparable to similarly crosslinked chain growth polymers. Utilization of the CuAAC reaction to form shape memory materials opens a range of possibilities and behaviors that are not readily achieved in other shape memory materials such as (meth) acrylates, thiolene, thiol-Michael, and poly(caprolactone) based shape memory materials. PMID:25378717

  17. 35,37Cl, and 79,81Br, and 69,71Ga nuclear quadrupole resonance of complexes of gallium trichloride and aluminum bromide with nitriles and amines

    International Nuclear Information System (INIS)

    Popkova, L.A.; Gur'yanova, E.N.; Muromtsev, V.I.; Zhukov, A.P.

    1989-01-01

    The formation of an intermolecular bond in complexes of the electron donor-acceptor (DA) type is accompanied by a redistribution of electron density in both components of the complex. Valuable information on the character of the changes undergone by the donor and acceptor molecules in complexation can be obtained from NQR spectrometry. The present work is aimed at correlating NQR frequencies and multiplicity of spectra with the redistribution of electron density among orbitals of the central atom and the transfer of electron density to the halogen atoms upon complexation. The authors have investigated the 35,37 Cl, 69,71 Ga, and 79,81 Br NQR spectra of complexes of gallium trichloride and aluminum bromide with nitriles and amines

  18. Crystal structure of tri­chlorido­(4'-ferrocenyl-2,2':6',2''-terpyridine-[kappa]3N,N',N'')iridium(III) aceto­nitrile disolvate

    KAUST Repository

    Davaasuren, Bambar

    2015-02-25

    In the title compound, [FeIr(C5H5)(C20H14N3)Cl3]·2CH3CN, the central IrIII atom is sixfold coordinated by three chloride ligands and three terpyridine N atoms in a slightly distorted octa­hedral fashion. The terpyridine ligand is functionalized at the 4\\'-position with a ferrocenyl group, the latter being in an eclipsed conformation. In the crystal, mol­ecules are stacked in rows parallel to [001], with the aceto­nitrile solvent mol­ecules situated between the rows. An extensive network of intra- and inter­molecular C-H...Cl inter­actions is present, stabilizing the three-dimensional structure.

  19. Whole glove permeation of cyclohexanol through disposable nitrile gloves on a dextrous robot hand and comparison with the modified closed-loop ASTM F739 method 1. No fist clenching.

    Science.gov (United States)

    Mathews, Airek R; Que Hee, Shane S

    2017-04-01

    The aim was to develop a whole glove permeation method for cyclohexanol to generate permeation parameter data for a non-moving dextrous robot hand (normalized breakthrough time t b , standardized breakthrough time t s , steady state permeation rate P s , and diffusion coefficient D). Four types of disposable powderless, unsupported, and unlined nitrile gloves from the same producer were investigated: Safeskin Blue and Kimtech Science Blue, Purple, and Sterling. The whole glove method developed involved a peristaltic pump for water circulation through chemically resistant Viton tubing to continually wash the inner surface of the test glove via holes in the tubing, a dextrous robot hand operated by a microprocessor, a chemically protective nitrile glove to protect the robot hand, an incubator to maintain 35°C temperature, and a hot plate to maintain 35°C at the sampling point of the circulating water. Aliquots of 1.0 mL were sampled at regular time intervals for the first 60 min followed by removal of 0.5 mL aliquots every hour to 8 hr. Quantification was by the internal standard method after gas chromatography-selective ion electron impact mass spectrometry using a non-polar capillary column. The individual glove values of t b and t s differed for the ASTM closed loop method except for Safeskin Blue, but did not for the whole glove method. Most of the kinetic parameters agreed within an order of magnitude for the two techniques. The order of most protective to least protective glove was Blue and Safeskin, then Purple followed by Sterling for the whole gloves. The analogous order for the modified F739 ASTM closed loop method was: Safeskin, Blue, Purple, and Sterling, almost the same as for the whole glove. The Sterling glove was "not recommended" from the modified ASTM data, and was "poor" from the whole glove data.

  20. Ethylene Oxide

    Science.gov (United States)

    Learn about ethylene oxide, which can raise your risk of lymphoma and leukemia. Exposure may occur through industrial emissions, tobacco smoke, and the use of products sterilized with ethylene oxide, such as certain medical products or cosmetics.

  1. Oxide ceramics

    International Nuclear Information System (INIS)

    Ryshkewitch, E.; Richerson, D.W.

    1985-01-01

    The book explores single-phase ceramic oxide systems from the standpoint of physical chemistry and technology. This second edition also focuses on advances in technology since publication of the original edition. These include improvements in raw materials and forming and sintering techniques, and the major role that oxide ceramics have had in development of advanced products and processes. The text is divided into five major sections: general fundamentals of oxide ceramics, advances in aluminum oxide technology, advances in zirconia technology, and advances in beryllium oxide technology

  2. Graphene Oxide as a Carbocatalyst for a Diels-Alder Reaction in an Aqueous Medium.

    Science.gov (United States)

    Girish, Yarabhally R; Pandit, Subrata; Pandit, Subhendu; De, Mrinmoy

    2017-09-19

    The Diels-Alder (DA) reaction, a [4+2] cycloaddition reaction, is highly important in synthetic organic chemistry and is frequently used in the synthesis of natural products containing six-membered rings. Herein, we report an efficient protocol for the DA reaction between 9-hydroxymethylanthracene and N-substituted maleimides using two-dimensional graphene oxide (GO) as a heterogeneous carbocatalyst in an aqueous medium at room temperature. High yields, a wide substrate scope, low temperature, excellent functional group tolerance, atom economy, and water as a green solvent are noteworthy features of this protocol. The heterogeneous GO catalyst can be easily recovered and used multiple times without any significant loss in catalytic activity. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. 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.

  4. Kinetics and mechanics of photo-polymerized triazole-containing thermosetting composites via the copper(I)-catalyzed azide-alkyne cycloaddition.

    Science.gov (United States)

    Song, Han Byul; Wang, Xiance; Patton, James R; Stansbury, Jeffrey W; Bowman, Christopher N

    2017-06-01

    Several features necessary for polymer composite materials in practical applications such as dental restorative materials were investigated in photo-curable CuAAC (copper(I)-catalyzed azide-alkyne cycloaddition) thermosetting resin-based composites with varying filler loadings and compared to a conventional BisGMA/TEGDMA based composite. Tri-functional alkyne and di-functional azide monomers were synthesized for CuAAC resins and incorporated with alkyne-functionalized glass microfillers for CuAAC composites. Polymerization kinetics, in situ temperature change, and shrinkage stress were monitored simultaneously with a tensometer coupled with FTIR spectroscopy and a data-logging thermocouple. The glass transition temperature was analyzed by dynamic mechanical analysis. Flexural modulus/strength and flexural toughness were characterized in three-point bending on a universal testing machine. The photo-CuAAC polymerization of composites containing between 0 and 60wt% microfiller achieved ∼99% conversion with a dramatic reduction in the maximum heat of reaction (∼20°C decrease) for the 60wt% filled CuAAC composites as compared with the unfilled CuAAC resin. CuAAC composites with 60wt% microfiller generated more than twice lower shrinkage stress of 0.43±0.01MPa, equivalent flexural modulus of 6.1±0.7GPa, equivalent flexural strength of 107±9MPa, and more than 10 times higher energy absorption of 10±1MJm -3 when strained to 11% relative to BisGMA-based composites at equivalent filler loadings. Mechanically robust and highly tough, photo-polymerized CuAAC composites with reduced shrinkage stress and a modest reaction exotherm were generated and resulted in essentially complete conversion. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  5. Fully recoverable rigid shape memory foam based on copper-catalyzed azide-alkyne cycloaddition (CuAAC) using a salt leaching technique.

    Science.gov (United States)

    Alzahrani, Abeer A; Saed, Mohand; Yakacki, Christopher M; Song, Han Byul; Sowan, Nancy; Walston, Joshua J; Shah, Parag K; McBride, Matthew K; Stansbury, Jeffrey W; Bowman, Christopher N

    2018-01-07

    This study is the first to employ the use of the copper-catalyzed azide-alkyne cycloaddition (CuAAC) polymerization to form a tough and stiff, porous material from a well-defined network possessing a high glass transition temperature. The effect of the network linkages formed as a product of the CuAAC reaction, i.e., the triazoles, on the mechanical behavior at high strain was evaluated by comparing the CuAAC foam to an epoxy-amine-based foam, which consisted of monomers with similar backbone structures and mechanical properties (i.e., T g of 115 °C and a rubbery modulus of 1.0 MPa for the CuAAC foam, T g of 125 °C and a rubbery modulus of 1.2 MPa for the epoxy-amine foam). When each foam was compressed uniformly to 80% strain at ambient temperature, the epoxy-amine foam was severely damaged after only reaching 70% strain in the first compression cycle with a toughness of 300 MJ/m 3 . In contrast, the CuAAC foam exhibited pronounced ductile behavior in the glassy state with three times higher toughness of 850 MJ/m 3 after the first cycle of compression to 80% strain. Additionally, when the CuAAC foam was heated above T g after each of five compression cycles to 80% strain at ambient temperature, the foam completely recovered its original shape while exhibiting a gradual decrease in mechanical performance over the multiple compression cycles. The foam demonstrated almost complete shape fixity and recovery ratios even through five successive cycles, indicative of "reversible plasticity", making it highly desirable as a glassy shape memory foams.

  6. RNA oxidation

    DEFF Research Database (Denmark)

    Kjaer, L. K.; Cejvanovic, V.; Henriken, T.

    2015-01-01

    RNA modification has attracted increasing interest as it is realized that epitranscriptomics is important in disease development. In type 2 diabetes we have suggested that high urinary excretion of 8-oxo-2'-Guanosine (8oxoGuo), as a measure of global RNA oxidation, is associated with poor survival.......9 significant hazard ratio for death compared with the quartile with the lowest 8oxoGuo excretion when adjusted for age, sex, BMI, smoker status, s-HbA1c, urine protein excretion and s-cholesterol. We conclude that it is now established that RNA oxidation is an independent risk factor for death in type 2...... diabetes. In agreement with our previous finding, DNA oxidation did not show any prognostic value. RNA oxidation represents oxidative stress intracellularly, presumably predominantly in the cytosol. The mechanism of RNA oxidation is not clear, but hypothesized to result from mitochondrial dysfunction...

  7. Experimental and Computational Studies of Binding of Dinitrogen, Nitriles, Azides, Diazoalkanes, Pyridine and Pyrazines to M(PR3)2(CO)3 (M=Mo, W; R=Me, iPr)

    Energy Technology Data Exchange (ETDEWEB)

    Hoff, C.D.; Muckerman, J.; Achord, P.; Fujita, E.; Scott, B.; Fortman, G.C.; Temprado, M.; Cai, X.; Captain, B.; Isrow, D.; Weir, J.J.; McDonough, J.E.

    2009-08-17

    The enthalpies of binding of a number of N-donor ligands to the complex Mo(P{sup i}Pr{sub 3}){sub 2}(CO){sub 3} in toluene have been determined by solution calorimetry and equilibrium measurements. The measured binding enthalpies span a range of {approx}10 kcal mol{sup -1}: {Delta}H{sub binding} = -8.8 {+-} 1.2 (N{sub 2}-Mo(P{sup i}Pr{sub 3}){sub 2}(CO){sub 3}); -10.3 {+-} 0.8 (N{sub 2}); -11.2 {+-} 0.4 (AdN{sub 3} (Ad = 1-adamantyl)); -13.8 {+-} 0.5 (N{sub 2}CHSiMe{sub 3}); -14.9 {+-} 0.9 (pyrazine = pz); -14.8 {+-} 0.6 (2,6-Me{sub 2}pz); -15.5 {+-} 1.8 (Me{sub 2}NCN); -16.6 {+-} 0.4 (CH{sub 3}CN); -17.0 {+-} 0.4 (pyridine); -17.5 {+-} 0.8 ([4-CH{sub 3}pz][PF{sub 6}] (in tetrahydrofuran)); -17.6 {+-} 0.4 (C{sub 6}H{sub 5}CN); -18.6 {+-} 1.8 (N{sub 2}CHC(=O)OEt); and -19.3 {+-} 2.5 kcal mol{sup -1} (pz)Mo(P{sup i}Pr{sub 3}){sub 2}(CO){sub 3}). The value for the isonitrile AdNC (-29.0 {+-} 0.3) is 12.3 kcal mol{sup -1} more exothermic than that of the nitrile AdCN (-16.7 {+-} 0.6 kcal mol{sup -1}). The enthalpies of binding of a range of arene nitrile ligands were also studied, and remarkably, most nitrile complexes were clustered within a 1 kcal mol{sup -1} range despite dramatic color changes and variation of v{sub CN}. Computed structural and spectroscopic parameters for the complexes Mo(P{sup i}Pr{sub 3}){sub 2}(CO){sub 3}L are in good agreement with experimental data. Computed binding enthalpies for Mo(P{sup i}Pr{sub 3}){sub 2}(CO){sub 3}L exhibit considerable scatter and are generally smaller compared to the experimental values, but relative agreement is reasonable. Computed enthalpies of binding using a larger basis set for Mo(PMe{sub 3}){sub 2}(CO){sub 3}L show a better fit to experimental data than that for Mo(P{sup i}Pr{sub 3}){sub 2}(CO){sub 3}L using a smaller basis set. Crystal structures of Mo(P{sup i}Pr{sub 3}){sub 2}(CO){sub 3}(AdCN), W(P{sup i}Pr{sub 3}){sub 2}(CO){sub 3}(Me{sub 2}NCN), W(P{sup i}Pr{sub 3}){sub 2}(CO){sub 3}(2,6-F{sub 2}C{sub 6}H

  8. Experimental and computational studies of binding of dinitrogen, nitriles, azides, diazoalkanes, pyridine, and pyrazines to M(PR(3))(2)(CO)(3) (M = Mo, W; R = Me, (i)Pr).

    Science.gov (United States)

    Achord, Patrick; Fujita, Etsuko; Muckerman, James T; Scott, Brian; Fortman, George C; Temprado, Manuel; Cai, Xiaochen; Captain, Burjor; Isrow, Derek; Weir, John J; McDonough, James Eric; Hoff, Carl D

    2009-08-17

    The enthalpies of binding of a number of N-donor ligands to the complex Mo(P(i)Pr(3))(2)(CO)(3) in toluene have been determined by solution calorimetry and equilibrium measurements. The measured binding enthalpies span a range of approximately 10 kcal mol(-1): DeltaH(binding) = -8.8 +/- 1.2 (N(2)-Mo(P(i)Pr(3))(2)(CO)(3)); -10.3 +/- 0.8 (N(2)); -11.2 +/- 0.4 (AdN(3) (Ad = 1-adamantyl)); -13.8 +/- 0.5 (N(2)CHSiMe(3)); -14.9 +/- 0.9 (pyrazine = pz); -14.8 +/- 0.6 (2,6-Me(2)pz); -15.5 +/- 1.8 (Me(2)NCN); -16.6 +/- 0.4 (CH(3)CN); -17.0 +/- 0.4 (pyridine); -17.5 +/- 0.8 ([4-CH(3)pz][PF(6)] (in tetrahydrofuran)); -17.6 +/- 0.4 (C(6)H(5)CN); -18.6 +/- 1.8 (N(2)CHC( horizontal lineO)OEt); and -19.3 +/- 2.5 kcal mol(-1) (pz)Mo(P(i)Pr(3))(2)(CO)(3)). The value for the isonitrile AdNC (-29.0 +/- 0.3) is 12.3 kcal mol(-1) more exothermic than that of the nitrile AdCN (-16.7 +/- 0.6 kcal mol(-1)). The enthalpies of binding of a range of arene nitrile ligands were also studied, and remarkably, most nitrile complexes were clustered within a 1 kcal mol(-1) range despite dramatic color changes and variation of nu(CN). Computed structural and spectroscopic parameters for the complexes Mo(P(i)Pr(3))(2)(CO)(3)L are in good agreement with experimental data. Computed binding enthalpies for Mo(P(i)Pr(3))(2)(CO)(3)L exhibit considerable scatter and are generally smaller compared to the experimental values, but relative agreement is reasonable. Computed enthalpies of binding using a larger basis set for Mo(PMe(3))(2)(CO)(3)L show a better fit to experimental data than that for Mo(P(i)Pr(3))(2)(CO)(3)L using a smaller basis set. Crystal structures of Mo(P(i)Pr(3))(2)(CO)(3)(AdCN), W(P(i)Pr(3))(2)(CO)(3)(Me(2)NCN), W(P(i)Pr(3))(2)(CO)(3)(2,6-F(2)C(6)H(3)CN), W(P(i)Pr(3))(2)(CO)(3)(2,4,6-Me(3)C(6)H(2)CN), W(P(i)Pr(3))(2)(CO)(3)(2,6-Me(2)pz), W(P(i)Pr(3))(2)(CO)(3)(AdCN), Mo(P(i)Pr(3))(2)(CO)(3)(AdNC), and W(P(i)Pr(3))(2)(CO)(3)(AdNC) are reported.

  9. Selective oxidation

    International Nuclear Information System (INIS)

    Cortes Henao, Luis F.; Castro F, Carlos A.

    2000-01-01

    It is presented a revision and discussion about the characteristics and factors that relate activity and selectivity in the catalytic and not catalytic partial oxidation of methane and the effect of variables as the temperature, pressure and others in the methane conversion to methanol. It thinks about the zeolites use modified for the catalytic oxidation of natural gas

  10. Anodic oxidation

    CERN Document Server

    Ross, Sidney D; Rudd, Eric J; Blomquist, Alfred T; Wasserman, Harry H

    2013-01-01

    Anodic Oxidation covers the application of the concept, principles, and methods of electrochemistry to organic reactions. This book is composed of two parts encompassing 12 chapters that consider the mechanism of anodic oxidation. Part I surveys the theory and methods of electrochemistry as applied to organic reactions. These parts also present the mathematical equations to describe the kinetics of electrode reactions using both polarographic and steady-state conditions. Part II examines the anodic oxidation of organic substrates by the functional group initially attacked. This part particular

  11. High-performance magnetic poly (arylene ether nitrile) nanocomposites: Co-modification of Fe3O4 via mussel inspired poly(dopamine) and amino functionalized silane KH550

    Science.gov (United States)

    Wan, Xinyi; Zhan, Yingqing; Long, Zhihang; Zeng, Guangyong; Ren, Yang; He, Yi

    2017-12-01

    To develop high-performance magnetic polymer composites, we reported a facial mussel-inspired way to functionalize Fe3O4 microspheres with dopamine (DA) and KH550, followed by compounding with poly (arylene ether nitrile) (PEN), to prepare functional nanocomposite films. Such mussel inspired co-modification of Fe3O4 was characterized and confirmed by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Therefore, the outstanding properties of the functionalize Fe3O4/polymer composites were obtained. With the addition of 15 wt% functionalized Fe3O4, the saturation magnetization (Ms) and dielectric permittivity of the PEN composites were increased to 12.49 emu/g and 14.3 (250 Hz), respectively, while the low dielectric loss was maintained. In addition, even the high loading content of Fe3O4 was incorporated, the functional PEN composites still exhibited high mechanical properties and thermal stability, including the significant improvement in glass transition temperature, and the same level of the tensile strength compared with neat PEN. Our work revealed that magnetic and dielectric PEN composites materials along with high comprehensive properties may be potentially used in the electromagnetic fields.

  12. Magnesium Oxide

    Science.gov (United States)

    Magnesium is an element your body needs to function normally. Magnesium oxide may be used for different reasons. Some people use it as ... one to four times daily depending on which brand is used and what condition you have. Follow ...

  13. Iron Oxides

    Energy Technology Data Exchange (ETDEWEB)

    Qafoku, Nikolla; Amonette, James E.

    2016-09-19

    Abstract: Fe oxides are common clay-sized oxide, oxyhydroxide and hydroxide soil minerals. They are compounds of Fe, O, and H that have structures based on close-packed arrays of O. The octahedral and tetrahedral cavities within these arrays are filled with either Fe3+ or Fe2+ to form Fe(O/OH)6, FeO6, or FeO4 structural units. All of the naturally occurring Fe oxide minerals usually undergo some degree of isomorphous substitution of other metal ions for Fe in their structures. Relatively simple techniques may be used to identify Fe oxides in the field based on their typical colors and magnetic properties. In the laboratory, a variety of instrumental techniques can be used to confirm phase identity and to quantify amount. Of these, X-ray diffraction, infrared spectroscopy, electron microscopy, thermal analysis, and Mössbauer spectroscopy are the most commonly used techniques. As oxides, the functional groups on their surfaces may have positive, negative, or no charge depending on pH and on the concentration and nature of other ions in the contact solution. A net positive surface charge usually is observed in soils because Fe oxides have a point-of-zero-charge in the neutral or slightly basic pHs. The functional groups on the surface form complexes with cations and anions from the aqueous phase. Their sorption and electron-buffering properties significantly affect the geochemical cycles of almost all elements having agronomic or environmental significance.

  14. Palladium-catalyzed [3+2] cycloaddition of trimethylenemethane with p-benzoquinones; Parajiumu shokubai wo mochiita torimechiren metan to p-benzokinon rui tono [3+2] fukakanka hanno

    Energy Technology Data Exchange (ETDEWEB)

    Mukawa, T.; Shiraishi, S. [The University of Tokyo, Tokyo (Japan). Institute of Industrial Science

    2000-01-10

    The reaction of trimethylenemethane with various alkyl-substituted p-benzoquinones was investigated. The reaction of 2,5-di-tert-butyl-p-benzoquinone with 2-(trimethylsilylmethyl) allyl acetate (1) was conducted with palladium (0) as a catalyst to afford 1 : 1-C=C-cycloadduct 2 in good yield. Similarly, 1 : -C=C-cycloadducts 3, 4, 5 and 6 were obtained with 2,6-di-tert-butyl-p-benzoquinone, 2,3,5,6-tetramethyl-p-benzoquinone, 2,3,5-trimethyl-p-benzoquinone and 2-methyl-1,4-naphthoquinone, respectively. On the other hand, the reaction with methyl-p-benzoquinone afforded the complicated mixture. As is the case with Diels-Alder reactions, the cycloaddition of trimethylenemethane with p-benzoquinones occurred towards C-C double bond. So, the reaction of trimethylenemethane with substituted p-benzoquinones is effective in the synthesis of methylenecyclopentane-fused cyclohexenediones having various substituents. (author)

  15. Green synthesis of copper nanoparticles using Ginkgo biloba L. leaf extract and their catalytic activity for the Huisgen [3+2] cycloaddition of azides and alkynes at room temperature.

    Science.gov (United States)

    Nasrollahzadeh, Mahmoud; Sajadi, S Mohammad

    2015-11-01

    During this study, we report the green synthesis of copper nanoparticles (Cu NPs) using Ginkgo biloba L. leaf extract as a reducing and stabilizing agent under surfactant-free conditions. The formation of Cu NPs is monitored by recording the UV-vis absorption spectra. The green synthesized Cu NPs are characterized by TEM, EDS, FT-IR and UV-visible techniques. According to UV-vis results, the synthesized Cu NPs by this method are quite stable even after one month indicating the stability of Cu NPs. In terms of environmental impact and economy, metallic Cu NPs offer several advantages over homogeneous and traditional heterogeneous catalysts. In addition, due to the increased metal surface area, Cu NPs shows very high catalytic activity for the Huisgen [3+2] cycloaddition of azides and alkynes at room temperature. Furthermore, the catalyst can be simply recovered and reused several times with almost no loss in activity. Copyright © 2015 Elsevier Inc. All rights reserved.

  16. Divergent Strategy for the Diastereoselective Synthesis of the Tricyclic 6,7-Diaryltetrahydro-6H-benzo[c]chromene Core via Pt(IV)-Catalyzed Cycloaddition of o-Quinone Methides and Olefin Ring-Closing Metathesis.

    Science.gov (United States)

    Tangdenpaisal, Kassrin; Chuayboonsong, Kanokpish; Ruchirawat, Somsak; Ploypradith, Poonsakdi

    2017-03-03

    A divergent strategy for the synthesis of the tricyclic 6,7-diaryltetrahydro-6H-benzo[c]chromene core was successfully developed. The 2,3-trans, 2,4-cis trisubstituted chroman moiety was formed via highly efficient and stereoselective Pt(IV)-catalyzed cycloaddition reactions of the corresponding quinone methides with chalcones. Subsequent steps provided the common diene alcohol, which underwent BF 3 ·Et 2 O-mediated Et 3 SiH reduction and olefin ring-closing metathesis (RCM) using Ru(II) catalysts. The sequence of the final two steps provided a handle to diversify the stereochemical outcomes at C6 as well as C10a.

  17. H-ferrierite zeolite: As an effective and reusable heterogeneous catalyst for synthesis of 1,5-benzothiazepine under solvent free condition and 1,3-dipolar cycloaddition in water

    Directory of Open Access Journals (Sweden)

    Thoraya A. Farghaly

    2017-05-01

    Full Text Available An efficient synthesis of new derivatives of 1,5-benzothiazepine has been developed by the reaction of various chalcones (1,3-diaryl-2-propenones with 2-amino-thiophenol in the presence of H-ferrierite zeolite as acidic catalyst without solvent. In addition, 1,3-dipolar cycloaddition of hydrazonoyl chlorides on CN bond of 1,5-benzothiazepines in water in the presence of Na2CO3/THAC as a base catalyst afforded 1,2,4-triazolo[3,4-d][1,5]benzothiazepines. The structure of all the newly synthesized compounds was established on the basis of spectral data (Mass, IR, 1H NMR, 13C NMR and elemental analysis.

  18. PyBidine-Cu(OTf)2 -catalyzed asymmetric [3+2] cycloaddition with imino esters: harmony of Cu-Lewis acid and imidazolidine-NH hydrogen bonding in concerto catalysis.

    Science.gov (United States)

    Arai, Takayoshi; Ogawa, Hiroki; Awata, Atsuko; Sato, Makoto; Watabe, Megumi; Yamanaka, Masahiro

    2015-01-26

    A bis(imidazolidine)pyridine (PyBidine)-Cu(OTf)2 complex catalyzing the endo-selective [3+2] cycloaddition of nitroalkenes with imino esters was applied to the reaction of methyleneindolinones with imino esters to afford spiro[pyrrolidin-3,3'-oxindole]s in up to 98 % ee. X-ray crystallographic analysis of the PyBidine-Cu(OTf)2 complex and DFT calculations suggested that an intermediate Cu enolate of the imino ester reacts with nitroalkenes or methyleneindolinones, which are activated by NH-hydrogen bonding with the PyBidine-Cu(OTf)2 catalyst. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Oxidation catalyst

    Science.gov (United States)

    Ceyer, Sylvia T.; Lahr, David L.

    2010-11-09

    The present invention generally relates to catalyst systems and methods for oxidation of carbon monoxide. The invention involves catalyst compositions which may be advantageously altered by, for example, modification of the catalyst surface to enhance catalyst performance. Catalyst systems of the present invention may be capable of performing the oxidation of carbon monoxide at relatively lower temperatures (e.g., 200 K and below) and at relatively higher reaction rates than known catalysts. Additionally, catalyst systems disclosed herein may be substantially lower in cost than current commercial catalysts. Such catalyst systems may be useful in, for example, catalytic converters, fuel cells, sensors, and the like.

  20. In situ growth of capping-free magnetic iron oxide nanoparticles on liquid-phase exfoliated graphene

    Science.gov (United States)

    Tsoufis, T.; Syrgiannis, Z.; Akhtar, N.; Prato, M.; Katsaros, F.; Sideratou, Z.; Kouloumpis, A.; Gournis, D.; Rudolf, P.

    2015-05-01

    We report a facile approach for the in situ synthesis of very small iron oxide nanoparticles on the surface of high-quality graphene sheets. Our synthetic strategy involved the direct, liquid-phase exfoliation of highly crystalline graphite (avoiding any oxidation treatment) and the subsequent chemical functionalization of the graphene sheets via the well-established 1,3-dipolar cycloaddition reaction. The resulting graphene derivatives were employed for the immobilization of the nanoparticle precursor (Fe cations) at the introduced organic groups by a modified wet-impregnation method, followed by interaction with acetic acid vapours. The final graphene-iron oxide hybrid material was achieved by heating (calcination) in an inert atmosphere. Characterization by X-ray diffraction, transmission electron and atomic force microscopy, Raman and X-ray photoelectron spectroscopy gave evidence for the formation of rather small (magnetite-rich nanoparticles which were evenly distributed on the surface of few-layer (nanoparticles, the hybrid material showed a superparamagnetic behaviour at room temperature.We report a facile approach for the in situ synthesis of very small iron oxide nanoparticles on the surface of high-quality graphene sheets. Our synthetic strategy involved the direct, liquid-phase exfoliation of highly crystalline graphite (avoiding any oxidation treatment) and the subsequent chemical functionalization of the graphene sheets via the well-established 1,3-dipolar cycloaddition reaction. The resulting graphene derivatives were employed for the immobilization of the nanoparticle precursor (Fe cations) at the introduced organic groups by a modified wet-impregnation method, followed by interaction with acetic acid vapours. The final graphene-iron oxide hybrid material was achieved by heating (calcination) in an inert atmosphere. Characterization by X-ray diffraction, transmission electron and atomic force microscopy, Raman and X-ray photoelectron spectroscopy

  1. A novel approach for the synthesis of 5-substituted-1H-tetrazoles

    Energy Technology Data Exchange (ETDEWEB)

    Akhlaghinia, Batool; Rezazadeh, Soodabeh, E-mail: akhlaghinia@um.ac.ir [Department of Chemistry, Faculty of Sciences, Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of)

    2012-12-15

    A series of 5-substituted-1H-tetrazoles (RCN{sub 4}H) have been synthesized by cycloaddition reaction of different aryl and alkyl nitriles with sodium azide in DMSO using CuSO{sub 4}{center_dot}5H{sub 2}O as catalyst. A wide variety of aryl nitriles underwent [3+2] cycloaddition to afford tetrazoles under mild reaction conditions in good to excellent yields. The catalyst used is readily available and environmentally friendly. Short reaction times, good to excellent yields, safe process and simple workup make this method an attractive and useful contribution to present organic synthesis of 5-substituted-1H-tetrazoles. (author)

  2. Oxidative stress

    Directory of Open Access Journals (Sweden)

    Stevanović Jelka

    2012-01-01

    Full Text Available The unceasing need for oxygen is in contradiction to the fact that it is in fact toxic to mammals. Namely, its monovalent reduction can have as a consequence the production of short-living, chemically very active free radicals and certain non-radical agents (nitrogen-oxide, superoxide-anion-radicals, hydroxyl radicals, peroxyl radicals, singlet oxygen, peroxynitrite, hydrogen peroxide, hypochlorous acid, and others. There is no doubt that they have numerous positive roles, but when their production is stepped up to such an extent that the organism cannot eliminate them with its antioxidants (superoxide-dismutase, glutathione-peroxidase, catalase, transferrin, ceruloplasmin, reduced glutathion, and others, a series of disorders is developed that are jointly called „oxidative stress.“ The reactive oxygen species which characterize oxidative stress are capable of attacking all main classes of biological macromolecules, actually proteins, DNA and RNA molecules, and in particular lipids. The free radicals influence lipid peroxidation in cellular membranes, oxidative damage to DNA and RNA molecules, the development of genetic mutations, fragmentation, and the altered function of various protein molecules. All of this results in the following consequences: disrupted permeability of cellular membranes, disrupted cellular signalization and ion homeostasis, reduced or loss of function of damaged proteins, and similar. That is why the free radicals that are released during oxidative stress are considered pathogenic agents of numerous diseases and ageing. The type of damage that will occur, and when it will take place, depends on the nature of the free radicals, their site of action and their source. [Projekat Ministarstva nauke Republike Srbije, br. 173034, br. 175061 i br. 31085

  3. Synthesis and Biological Evaluation of Novel Hybrid Molecules Containing Purine, Coumarin and Isoxazoline or Isoxazole Moieties

    Science.gov (United States)

    Kallitsakis, Michael G.; Carotti, Angelo; Catto, Marco; Peperidou, Aikaterini; Hadjipavlou-Litina, Dimitra J.; Litinas, Konstantinos E.

    2017-01-01

    Introduction: The 1,3-dipolar cycloaddition reactions of nitrile oxides formed in situ (in the presence of NCS and Et3N) from the oximes of (purin-9-yl)acetaldehyde or (coumarinyloxy)acetaldehyde with allyloxycoumarins or 9-allylpurines, respectively resulted in 3,5-disubstituted isoxazolines. The similar reactions of propargyloxycoumarins or 9-propargylpurines led to 3,5-disubstituted isoxazoles by treatment with PIDA and catalytic amount of TFA. Methods: The new compounds were tested in vitro as antioxidant agents and inhibitors of soybean lipoxygenase LO, AChE and MAO-B. Results: The majority of the compounds showed significant hydroxyl radical scavenging activity. Compounds 4k and 4n presented LO inhibitory activity. Conclusion: Compound 13e presents an antioxidant significant profile combining anti-LO, anti-AChE and anti-MAO-B activities. PMID:29387274

  4. Water and organic synthesis: a focus on the in-water and on-water border. Reversal of the in-water Breslow hydrophobic enhancement of the normal endo-effect on crossing to on-water conditions for Huisgen cycloadditions with increasingly insoluble organic liquid and solid 2π-dipolarophiles.

    Science.gov (United States)

    Butler, Richard N; Coyne, Anthony G; Cunningham, William J; Moloney, Eamon M

    2013-04-05

    Measurements of the endo/exo product ratios for Huisgen cycloadditions with a series of vinyl ketones, alkyl acrylates, and substituted styrenes as dipolarophiles with phthalazinium and pyridazinium dicyanomethanide 1,3-dipoles in acetonitrile and water show that as the reactions change from in-water (large hydrophobic enhancement of endo-products) to on-water, the hydrophobic enhancement of the endo-products is reduced and partially reversed (relative to acetonitrile). An expected increase of the endo-effect with increasing hydrophobic character of the dipolarophile is overcome by decreasing water solubility causing changeover to on-water conditions. On-water reactions do not show increased cycloaddition endo-effects (relative to organic solvents) as do in-water reactions.

  5. Protection of the Queuosine Biosynthesis Enzyme QueF from Irreversible Oxidation by a Conserved Intramolecular Disulfide

    Directory of Open Access Journals (Sweden)

    Adeba Mohammad

    2017-03-01

    Full Text Available QueF enzymes catalyze the nicotinamide adenine dinucleotide phosphate (NADPH-dependent reduction of the nitrile group of 7-cyano-7-deazaguanine (preQ0 to 7-aminomethyl-7-deazaguanine (preQ1 in the biosynthetic pathway to the tRNA modified nucleoside queuosine. The QueF-catalyzed reaction includes formation of a covalent thioimide intermediate with a conserved active site cysteine that is prone to oxidation in vivo. Here, we report the crystal structure of a mutant of Bacillus subtilis QueF, which reveals an unanticipated intramolecular disulfide formed between the catalytic Cys55 and a conserved Cys99 located near the active site. This structure is more symmetric than the substrate-bound structure and exhibits major rearrangement of the loops responsible for substrate binding. Mutation of Cys99 to Ala/Ser does not compromise enzyme activity, indicating that the disulfide does not play a catalytic role. Peroxide-induced inactivation of the wild-type enzyme is reversible with thioredoxin, while such inactivation of the Cys99Ala/Ser mutants is irreversible, consistent with protection of Cys55 from irreversible oxidation by disulfide formation with Cys99. Conservation of the cysteine pair, and the reported in vivo interaction of QueF with the thioredoxin-like hydroperoxide reductase AhpC in Escherichia coli suggest that regulation by the thioredoxin disulfide-thiol exchange system may constitute a general mechanism for protection of QueF from oxidative stress in vivo.

  6. Synthesis and characterization of cyclic polystyrene using copper-catalyzed alkyne-azide cycloaddition coupling - evaluation of physical properties and optimization of cyclization conditions

    Science.gov (United States)

    Elupula, Ravinder

    . Whereas, anionically prepared A-PS had much higher reliance on the molecular weight changes for its glass transition temperature. However, in thin films, c-PS films have, within error, no confinement effect. In contrast, A-PS has seen large T g reduction with confinement. Ellipsometry analysis suggests that this invariance of the Tg-confinement effect in c-PS is a result of the weak perturbation to Tg near the free surface (i.e. the polymer-air interface). These weak perturbations are the result of the high packing efficiency of cyclic PS segments. The copper-catalyzed alkyne/azide cycloaddition (CuAAC) click reaction has been used to cyclize many linear polymers with complementary azide and alkyne end groups via unimolecular heterodifunctional approach. Cyclic polymers exhibit unique and potentially useful physical properties compared to their linear analogs, hence increasing interest in techniques for preparing this class of polymers. However, a general route for producing high purity cyclic polymers remained elusive. Prior to the discovery of "click" chemistry, it was difficult to produce highly pure cyclic polymers via the ring-closure approach, requiring extensive post-cyclization purification. However, even minor amounts of linear impurities can influence the physical properties of cyclic polymers. Thermal gradient interaction chromatography (TGIC) coupled with Matrix-Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry (MALDI-ToF MS) allows the fractionation of cyclic polymer samples and produce valuable data for determining both the quantity and identity of linear impurities. This understanding further enables us to optimize cyclization conditions towards the goal of and efficient, general methodology for producing highly pure cyclic polymers. To solve the ever-growing energy needs of the world and capture the renewable energy that is generated sporadically, we need to create devices that can store high amounts of energy and discharge power at

  7. Modular "click" chemistry for electrochemically and photoelectrochemically active molecular interfaces to tin oxide surfaces.

    Science.gov (United States)

    Benson, Michelle C; Ruther, Rose E; Gerken, James B; Rigsby, Matthew L; Bishop, Lee M; Tan, Yizheng; Stahl, Shannon S; Hamers, Robert J

    2011-08-01

    We demonstrate the use of "click" chemistry to form electrochemically and photoelectrochemically active molecular interfaces to SnO(2) nanoparticle thin films. By using photochemical grafting to link a short-chain alcohol to the surface followed by conversion to a surface azide group, we enable use of the Cu(I)-catalyzed azide-alkyne [3 + 2] cycloaddition (CuAAC) reaction, a form of "click" chemistry, on metal oxide surfaces. Results are shown with three model compounds to test the surface chemistry and subsequent ability to achieve electrochemical and photoelectrochemical charge transfer. Surface-tethered ferrocene groups exhibit good electron-transfer characteristics with thermal rates estimated at >1000 s(-1). Time-resolved surface photovoltage measurements using a ruthenium terpyridyl coordination compound demonstrate photoelectron charge transfer on time scales of nanoseconds or less, limited by the laser pulse width. The results demonstrate that the CuAAC "click" reaction can be used to form electrochemically and photoelectrochemically active molecular interfaces to SnO(2) and other metal oxide semiconductors.

  8. Four mechanisms in the reactions of 3-aminopyrrole with 1,3,5-triazines: inverse electron demand Diels-Alder cycloadditions vs S(N)Ar reactions via uncatalyzed and acid-catalyzed pathways.

    Science.gov (United States)

    De Rosa, Michael; Arnold, David; Hartline, Douglas

    2013-09-06

    Reaction of 3-aminopyrrole with seven 1,3,5-triazines was studied in a one-step reaction (in situ formation of 3-aminopyrrole) and a two-step reaction (using the tetraphenylborate salt and an amine base). An inverse-electron demand Diels-Alder reaction (IEDDA) was observed with R1 = CF3, CO2Et, and H with the formation of 5H-pyrrolo[3,2-d]pyrimidine derivatives. S(N)Ar was observed when 2,4,6-trifluoro- or 2,4,6-trichloro-1,3,5-triazine were used--1,3,5-triazines that had leaving groups. If excess 1,3,5-triazine was present the initial S(N)Ar product reacted further, in the presence of acid and water, with another equivalent of 1,3,5-triazine to give compounds containing three linked heterocyclic rings. No reaction was observed with R1 = C6H5 and OCH3. Four mechanisms are proposed to explain the experimental results: uncatalyzed and acid catalyzed inverse electron demand Diels-Alder cascades leading to cycloaddition, and uncatalyzed and acid-catalyzed S(N)Ar reactions leading, respectively, to single and double substitution products. Acid catalysis was a factor when there was reduced reactivity in either reactant.

  9. Elastomeric Nanocomposite Based on Exfoliated Graphene Oxide and Its Characteristics without Vulcanization

    Directory of Open Access Journals (Sweden)

    Nasser Abdullah Habib

    2017-01-01

    Full Text Available Rubber nanocomposites have emerged as one of the advanced materials in recent years. The aim of this work was to homogeneously disperse graphene oxide (GO sheets into Nitrile Butadiene Rubber (NBR and investigate the characteristics of GO/NBR nanocomposite without vulcanization. A suitable solvent was found to dissolve dry NBR while GO was exfoliated completely in an aqueous base solution using sonication. GO was dispersed into NBR at different loadings by solution mixing to produce unvulcanized GO/NBR nanocomposites. Scanning Electron Microscopy (SEM, Fourier-Transform Infrared Spectroscopy (FTIR, and X-Ray Diffraction (XRD were used to characterize the samples. Furthermore, mechanical and electrical properties of unvulcanized GO/NBR nanocomposites were carried out to determine the influence of GO on the NBR properties. The results showed that the modulus of GO/NBR nanocomposite at 1 wt% of GO was enhanced by about 238% compared with unfilled NBR. These results provide insight into the properties of unvulcanized GO/NBR nanocomposite for application as coatings or adhesives.

  10. Solute's perspective on how trimethylamine oxide, urea, and guanidine hydrochloride affect water's hydrogen bonding ability.

    Science.gov (United States)

    Pazos, Ileana M; Gai, Feng

    2012-10-18

    While the thermodynamic effects of trimethylamine oxide (TMAO), urea, and guanidine hydrochloride (GdnHCl) on protein stability are well understood, the underlying mechanisms of action are less well characterized and, in some cases, even under debate. Herein, we employ the stretching vibration of two infrared (IR) reporters, i.e., nitrile (C≡N) and carbonyl (C═O), to directly probe how these cosolvents mediate the ability of water to form hydrogen bonds with the solute of interest, e.g., a peptide. Our results show that these three agents, despite having different effects on protein stability, all act to decrease the strength of the hydrogen bonds formed between water and the infrared probe. While the behavior of TMAO appears to be consistent with its protein-protecting ability, those of urea and GdnHCl are inconsistent with their role as protein denaturants. The latter is of particular interest as it provides strong evidence indicating that although urea and GdnHCl can perturb the hydrogen-bonding property of water their protein-denaturing ability does not arise from a simple indirect mechanism.

  11. Surface morphology and dewettability of self-organized thermosets involving epoxy and POSS-capped poly(ethylene oxide) telechelics

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Lei [Department of Polymer Science and Engineering and the State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240 (China); Zheng, Sixun, E-mail: szheng@sjtu.edu.cn [Department of Polymer Science and Engineering and the State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240 (China)

    2012-10-15

    A heptaphenyl polyhedral oligomeric silsesquioxane-capped poly(ethylene oxide) (POSS-capped PEO) telechelics was synthesized via the Huisgen 1,3-dipolar cycloaddition between 3-azidopropylheptaphenyl POSS and {alpha},{omega}-dialkynyl-terminated poly(ethylene oxide). The organic-inorganic amphiphile was incorporated into epoxy to obtain the organic-inorganic nanocomposites. The morphology of the nanocomposites was investigated by means of atomic force microscopy (AFM) and dynamic mechanical thermal analysis (DMTA). It was found that the epoxy thermosets containing POSS-capped PEO telechelics were microphase-separated. The formation of the nanophases in the thermosets followed a self-assembly mechanism. The static contact angle measurements show that the nanocomposites displayed a significant enhancement in surface hydrophobicity as well as reduction in surface free energy. The improvement in surface dewettability was ascribed to the enrichment of POSS cages at the surface of the nanocomposites and the formation of the specific surface morphology as evidenced by X-ray photoelectron spectroscopy (XPS) and surface atomic force microscopy (AFM). -- Highlights: Black-Right-Pointing-Pointer POSS-capped PEO telechelics was synthesized via click chemistry approach. Black-Right-Pointing-Pointer The organic-inorganic amphiphile can be self-assembled into the nanophases in epoxy. Black-Right-Pointing-Pointer The hybrid nanocomposites were successfully prepared via a self-assembly approach. Black-Right-Pointing-Pointer The nanocomposites displayed a significant enhancement in surface hydrophobicity.

  12. Surface morphology and dewettability of self-organized thermosets involving epoxy and POSS-capped poly(ethylene oxide) telechelics

    International Nuclear Information System (INIS)

    Wang, Lei; Zheng, Sixun

    2012-01-01

    A heptaphenyl polyhedral oligomeric silsesquioxane-capped poly(ethylene oxide) (POSS-capped PEO) telechelics was synthesized via the Huisgen 1,3-dipolar cycloaddition between 3-azidopropylheptaphenyl POSS and α,ω-dialkynyl-terminated poly(ethylene oxide). The organic–inorganic amphiphile was incorporated into epoxy to obtain the organic–inorganic nanocomposites. The morphology of the nanocomposites was investigated by means of atomic force microscopy (AFM) and dynamic mechanical thermal analysis (DMTA). It was found that the epoxy thermosets containing POSS-capped PEO telechelics were microphase-separated. The formation of the nanophases in the thermosets followed a self-assembly mechanism. The static contact angle measurements show that the nanocomposites displayed a significant enhancement in surface hydrophobicity as well as reduction in surface free energy. The improvement in surface dewettability was ascribed to the enrichment of POSS cages at the surface of the nanocomposites and the formation of the specific surface morphology as evidenced by X-ray photoelectron spectroscopy (XPS) and surface atomic force microscopy (AFM). -- Highlights: ► POSS-capped PEO telechelics was synthesized via click chemistry approach. ► The organic–inorganic amphiphile can be self-assembled into the nanophases in epoxy. ► The hybrid nanocomposites were successfully prepared via a self-assembly approach. ► The nanocomposites displayed a significant enhancement in surface hydrophobicity.

  13. Photochemical Oxidation of Thioketones by Singlet Molecular Oxygen Revisited: Insights into Photoproducts, Kinetics, and Reaction Mechanism.

    Science.gov (United States)

    Sánchez-Arroyo, Antonio J; Pardo, Zulay D; Moreno-Jiménez, Florencio; Herrera, Antonio; Martín, Nazario; García-Fresnadillo, David

    2015-11-06

    Photosensitized oxidation of trimethyl[2.2.1]bicycloheptane thioketones by (1)O2 can yield more photoproducts than exclusively ketones and sulfines. Moreover, the ketone/sulfine ratio can be reversed when protic conditions and high thioketone concentrations are used, conversely to earlier results reporting ketones as the main photoproducts. A new mechanistic proposal for sulfine formation is suggested following intermolecular oxygen transfer from a peroxythiocarbonyl intermediate to a second thioketone molecule. Reaction quantum yields (10(-5)-10(-2)) depend on the reaction conditions and time. Sulfine production reaches a maximum at short irradiation times, whereas decomposition to the corresponding ketone is observed at long reaction times. When the thioketone substrate has a hydrogen atom at the α position a peroxyvinylsulfenic acid intermediate can be formed by proton transfer. Reaction of this intermediate with another thioketone molecule can yield more sulfine and its tautomeric vinylsulfenic acid, which dimerizes in situ to the thiosulfinate. The hydroperoxyl group of the peroxyvinylsulfenic acid can also rearrange to the α position, and by reaction with the starting thioketone, α-hydroxy thioketone and additional sulfine can be formed, while dehydration yields the α-oxo thioketone. In situ [2 + 2] and [4 + 2] self-cycloaddition of the α-oxo thioketone yields significant amounts of the corresponding adducts at prolonged irradiation times.

  14. RNA modifications by oxidation

    DEFF Research Database (Denmark)

    Poulsen, Henrik E; Specht, Elisabeth; Broedbaek, Kasper

    2012-01-01

    to encompass various classes of novel regulatory RNAs, including, e.g., microRNAs. It is well known that DNA is constantly oxidized and repaired by complex genome maintenance mechanisms. Analogously, RNA also undergoes significant oxidation, and there are now convincing data suggesting that oxidation......, and the consequent loss of integrity of RNA, is a mechanism for disease development. Oxidized RNA is found in a large variety of diseases, and interest has been especially devoted to degenerative brain diseases such as Alzheimer disease, in which up to 50-70% of specific mRNA molecules are reported oxidized, whereas...... other RNA molecules show virtually no oxidation. The iron-storage disease hemochromatosis exhibits the most prominent general increase in RNA oxidation ever observed. Oxidation of RNA primarily leads to strand breaks and to oxidative base modifications. Oxidized mRNA is recognized by the ribosomes...

  15. Studies on PLA grafting onto graphene oxide and its effect on the ensuing composite films

    Energy Technology Data Exchange (ETDEWEB)

    Campos, João M., E-mail: jmdcampos@ua.pt [CICECO - Aveiro Institute of Materials and Department of Chemistry, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro (Portugal); Instituto de Biotecnologia e Bioengenharia (IBB) and Department of Chemical Engineering, Instituto Superior Técnico, University of Lisbon, Av. Rovisco Pais, 1049-001 Lisbon (Portugal); Ferraria, Ana M.; Botelho do Rego, Ana M. [Centro de Química-Física Molecular and Institute of Nanoscience and Nanotechnology, Instituto Superior Técnico, University of Lisbon, Av. Rovisco Pais, 1049-001 Lisbon (Portugal); Ribeiro, M. Rosário [Centro de Química Estrutural (CQE) and Department of Chemical Engineering, Instituto Superior Técnico, University of Lisbon, Av. Rovisco Pais, 1049-001 Lisbon (Portugal); Barros-Timmons, Ana [CICECO - Aveiro Institute of Materials and Department of Chemistry, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro (Portugal)

    2015-09-15

    Polylactide (PLA) with a terminal triple bond was synthesized by organocatalyzed ring-opening polymerization and coupled with azide-functionalized graphene oxide (GO) through an azide-alkyne cycloaddition “click” reaction. The functionalized graphenic species involved were analyzed by spectroscopic techniques (FT-IR, solid state {sup 13}C NMR, Raman), which confirmed the coupling of PLA and GO. Additionally, an in depth study of the prepared GO, intermediates and GO-g-PLA hybrid was carried out that sheds light on the mechanisms involved in the functionalization path. The obtained GO-g-PLA hybrid, containing at least 20% of biopolymer, presented an exfoliated graphenic structure, as established by XRD. The conditions used in the grafting of the PLA chains inhibited the crystallization and melting observed for the free polymer. Furthermore, the graphene oxide seems to be reduced during functionalization, which can also be an advantage. Nanocomposites were obtained as solvent-cast films, prepared by dispersion of the GO-g-PLA hybrid in commercial PLA. Preliminary results regarding the performance of these nanocomposites, obtained by DSC and DMA, highlighted the effect of functionalization. Loading values as low as 0.5% suffice to improve the mechanical properties over a broad temperature range due to the high surface area resulting from the good dispersibility of polymer functionalized nanofillers and/or their effect on the polymer chain organization. - Highlights: • A graphene oxide/PLA (GO-g-PLA) hybrid was obtained by a grafting-to method. • Grafting of PLA chains onto the surface of GO inhibited polymer crystallization. • The GO-g-PLA material was used in the reinforcement of PLA, as nanocomposite films. • GO-g-PLA provides more homogeneously reinforced nanocomposite films, than neat GO. • Nanocomposite films with 0.5% loading present high storage modulus even above T{sub g}.

  16. Photo-oxidation catalysts

    Science.gov (United States)

    Pitts, J Roland [Lakewood, CO; Liu, Ping [Irvine, CA; Smith, R Davis [Golden, CO

    2009-07-14

    Photo-oxidation catalysts and methods for cleaning a metal-based catalyst are disclosed. An exemplary catalyst system implementing a photo-oxidation catalyst may comprise a metal-based catalyst, and a photo-oxidation catalyst for cleaning the metal-based catalyst in the presence of light. The exposure to light enables the photo-oxidation catalyst to substantially oxidize absorbed contaminants and reduce accumulation of the contaminants on the metal-based catalyst. Applications are also disclosed.

  17. Pseudo steres and XXXIII derivated. Synthesis of cyclopropane compounds by photolysis of pyrazolines obtained by cycloaddition of 1-3 dipolar to the 5-methoxy-2 (5H) furanone; Pseudoesteres derivados XXXIII. Sintesis de compuestos ciclopropanicos por fotolisis de pirazolinas obtenidas por cicloadicion 1,3 dipolar a la 5-metaxi-2(5h)-furanona

    Energy Technology Data Exchange (ETDEWEB)

    Farina, F.; Martin, M.V.; Soria, M.L. [Instituto de Quimica Oeganica General, CSIC, Madrid (Spain)

    1995-11-01

    By cycloaddition of 2-diazopropane to 5-methoxy-2(5H)-furanone (1) two regioisomeric 1-pyrazolines 3 and 4 are stereo specifically obtained. Both isomers give by photolysis, as major or sole compound, the same cyclopropane derivative 7. Hydrolysis of the bicyclic compound 7, followed by esterification, leads to cis open chain derivatives, which are appropriately functioned for the synthesis of pyrethroids. A similar set of reactions, using diazomethane-de{sub 2} as dipolarophile, affords selectively deuterated cyclopropane derivatives. 20 refs.

  18. The Enzymatic Oxidation of Graphene Oxide

    Science.gov (United States)

    Kotchey, Gregg P.; Allen, Brett L.; Vedala, Harindra; Yanamala, Naveena; Kapralov, Alexander A.; Tyurina, Yulia Y.; Klein-Seetharaman, Judith; Kagan, Valerian E.; Star, Alexander

    2011-01-01

    Two-dimensional graphitic carbon is a new material with many emerging applications, and studying its chemical properties is an important goal. Here, we reported a new phenomenon – the enzymatic oxidation of a single layer of graphitic carbon by horseradish peroxidase (HRP). In the presence of low concentrations of hydrogen peroxide (~40 µM), HRP catalyzed the oxidation of graphene oxide, which resulted in the formation of holes on its basal plane. During the same period of analysis, HRP failed to oxidize chemically reduced graphene oxide (RGO). The enzymatic oxidation was characterized by Raman, UV-Vis, EPR and FT-IR spectroscopy, TEM, AFM, SDS-PAGE, and GC-MS. Computational docking studies indicated that HRP was preferentially bound to the basal plane rather than the edge for both graphene oxide and RGO. Due to the more dynamic nature of HRP on graphene oxide, the heme active site of HRP was in closer proximity to graphene oxide compared to RGO, thereby facilitating the oxidation of the basal plane of graphene oxide. We also studied the electronic properties of the reduced intermediate product, holey reduced graphene oxide (hRGO), using field-effect transistor (FET) measurements. While RGO exhibited a V-shaped transfer characteristic similar to a single layer of graphene that was attributed to its zero band gap, hRGO demonstrated a p-type semiconducting behavior with a positive shift in the Dirac points. This p-type behavior rendered hRGO, which can be conceptualized as interconnected graphene nanoribbons, as a potentially attractive material for FET sensors. PMID:21344859

  19. Electronic Structure of Manganese Complexes of the Redox-Non-innocent Tetrazene Ligand and Evidence for the Metal-Azide/Imido Cycloaddition Intermediate.

    Science.gov (United States)

    Vaddypally, Shivaiah; McKendry, Ian G; Tomlinson, Warren; Hooper, Joseph P; Zdilla, Michael J

    2016-07-18

    The first synthetic manganese tetrazene complexes are described as a redox pair comprising anionic [Mn(N4 Ad2 )2 ](-) (1) and neutral Mn(N4 Ad2 )2 (2) complexes (N4 Ad2 =[Ad-N-N=N-N-Ad](2-) ). Compound 1 is obtained in two forms as lithium salts, one as a cationic Li2 Mn cluster, and one as a Mn-Li 1D ionic polymer. Compound 1 is electronically described as a Mn(III) center with two [N4 Ad2 ](2-) ligands. The one-electron oxidized 2 is crystalized in two morphologies, one as pure 2 and one as an acetonitrile adduct. Despite similar composition, the behavior of 2 differs in the two morphologies. Compound 2-MeCN is relatively air and temperature stable. Crystalline 2, on the other hand, exhibits a compositional, dynamic disorder wherein the tetrazene metallacycle ring-opens into a metal imide/azide complex detectable by X-ray crystallography and FTIR spectroscopy. Electronic structure of 2 was examined by EPR and XPS spectroscopies and DFT calculations, which indicate 2 is best described as a Mn(III) ion with an anion radical delocalized across the two ligands through spin-polarization effects. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Nitric oxide supersensitivity

    DEFF Research Database (Denmark)

    Olesen, J; Iversen, Helle Klingenberg; Thomsen, L L

    1993-01-01

    Nitroglycerin, which may be regarded as a prodrug for nitric oxide, induces a mild to moderate headache in healthy subjects. In order to study whether migraine patients are more sensitive to nitric oxide than non-migrainous subjects, four different doses of intravenous nitroglycerin were given...... previously shown a similar supersensitivity to histamine which in human cerebral arteries activates endothelial H1 receptors and causes endothelial production of nitric oxide. Migraine patients are thus supersensitive to exogenous nitric oxide from nitroglycerin as well as to endothelially produced nitric...... oxide. It is suggested that nitric oxide may be partially or completely responsible for migraine pain....

  1. Zinc oxide overdose

    Science.gov (United States)

    Zinc oxide is an ingredient in many products. Some of these are certain creams and ointments used ... prevent or treat minor skin burns and irritation. Zinc oxide overdose occurs when someone eats one of ...

  2. Oxidative Stress in Neurodegeneration

    Directory of Open Access Journals (Sweden)

    Varsha Shukla

    2011-01-01

    Full Text Available It has been demonstrated that oxidative stress has a ubiquitous role in neurodegenerative diseases. Major source of oxidative stress due to reactive oxygen species (ROS is related to mitochondria as an endogenous source. Although there is ample evidence from tissues of patients with neurodegenerative disorders of morphological, biochemical, and molecular abnormalities in mitochondria, it is still not very clear whether the oxidative stress itself contributes to the onset of neurodegeneration or it is part of the neurodegenerative process as secondary manifestation. This paper begins with an overview of how oxidative stress occurs, discussing various oxidants and antioxidants, and role of oxidative stress in diseases in general. It highlights the role of oxidative stress in neurodegenerative diseases like Alzheimer's, Parkinson's, and Huntington's diseases and amyotrophic lateral sclerosis. The last part of the paper describes the role of oxidative stress causing deregulation of cyclin-dependent kinase 5 (Cdk5 hyperactivity associated with neurodegeneration.

  3. A Customized Metal Oxide Semiconductor-Based Gas Sensor Array for Onion Quality Evaluation: System Development and Characterization

    Science.gov (United States)

    Konduru, Tharun; Rains, Glen C.; Li, Changying

    2015-01-01

    A gas sensor array, consisting of seven Metal Oxide Semiconductor (MOS) sensors that are sensitive to a wide range of organic volatile compounds was developed to detect rotten onions during storage. These MOS sensors were enclosed in a specially designed Teflon chamber equipped with a gas delivery system to pump volatiles from the onion samples into the chamber. The electronic circuit mainly comprised a microcontroller, non-volatile memory chip, and trickle-charge real time clock chip, serial communication chip, and parallel LCD panel. User preferences are communicated with the on-board microcontroller through a graphical user interface developed using LabVIEW. The developed gas sensor array was characterized and the discrimination potential was tested by exposing it to three different concentrations of acetone (ketone), acetonitrile (nitrile), ethyl acetate (ester), and ethanol (alcohol). The gas sensor array could differentiate the four chemicals of same concentrations and different concentrations within the chemical with significant difference. Experiment results also showed that the system was able to discriminate two concentrations (196 and 1964 ppm) of methlypropyl sulfide and two concentrations (145 and 1452 ppm) of 2-nonanone, two key volatile compounds emitted by rotten onions. As a proof of concept, the gas sensor array was able to achieve 89% correct classification of sour skin infected onions. The customized low-cost gas sensor array could be a useful tool to detect onion postharvest diseases in storage. PMID:25587975

  4. A Customized Metal Oxide Semiconductor-Based Gas Sensor Array for Onion Quality Evaluation: System Development and Characterization

    Directory of Open Access Journals (Sweden)

    Tharun Konduru

    2015-01-01

    Full Text Available A gas sensor array, consisting of seven Metal Oxide Semiconductor (MOS sensors that are sensitive to a wide range of organic volatile compounds was developed to detect rotten onions during storage. These MOS sensors were enclosed in a specially designed Teflon chamber equipped with a gas delivery system to pump volatiles from the onion samples into the chamber. The electronic circuit mainly comprised a microcontroller, non-volatile memory chip, and trickle-charge real time clock chip, serial communication chip, and parallel LCD panel. User preferences are communicated with the on-board microcontroller through a graphical user interface developed using LabVIEW. The developed gas sensor array was characterized and the discrimination potential was tested by exposing it to three different concentrations of acetone (ketone, acetonitrile (nitrile, ethyl acetate (ester, and ethanol (alcohol. The gas sensor array could differentiate the four chemicals of same concentrations and different concentrations within the chemical with significant difference. Experiment results also showed that the system was able to discriminate two concentrations (196 and 1964 ppm of methlypropyl sulfide and two concentrations (145 and 1452 ppm of 2-nonanone, two key volatile compounds emitted by rotten onions. As a proof of concept, the gas sensor array was able to achieve 89% correct classification of sour skin infected onions. The customized low-cost gas sensor array could be a useful tool to detect onion postharvest diseases in storage.

  5. Sputtered tin oxide and titanium oxide thin films as alternative transparent conductive oxides

    OpenAIRE

    Boltz, Janika

    2011-01-01

    Alternative transparent conductive oxides to tin doped indium oxide have been investigated. In this work, antimony doped tin oxide and niobium doped titanium oxide have been studied with the aim to prepare transparent and conductive films. Antimony doped tin oxide and niobium doped titanium oxide belong to different groups of oxides; tin oxide is a soft oxide, while titanium oxide is a hard oxide. Both oxides are isolating materials, in case the stoichiometry is SnO2 and TiO2. In order to ach...

  6. The oxidative pulverisation of mixed oxide fuels

    International Nuclear Information System (INIS)

    Rance, Peter; Beznosyuk, Vassily

    2005-01-01

    An investigation of the oxidation of mixed uranium-plutonium oxide (MOx) fuels containing from 5-30% plutonium (heavy metal basis) in air and oxygen atmospheres has been undertaken. MOx pellets prepared by a co-precipitation process were oxidised at temperatures from 600 to 1200degC, samples were reduced back to the MO 2 state and then re-oxidised. Weight changes were monitored during each procedure and the phases present in the products from each treatment were analysed using X-ray diffraction (XRD). Samples containing up to 10% Pu were oxidised sufficiently to cause pulverisation of the fuel matrix by a single oxidation treatment at 600degC whereas samples containing higher plutonium contents required a cycle of oxidation-reduction-oxidation cause them to become fragmented. XRD data suggests the formation of plutonium-rich and plutonium-lean grains during the reduction cycle and it is suggested that the oxidation of plutonium-lean grains during re-oxidation step is responsible for the break up of the pellets during this step. (author)

  7. Effect Of Oxidation Temperature And Oxidation Time On Thickness ...

    African Journals Online (AJOL)

    Investigation has been made concerning the effect of oxidation temperature and time on the thickness of copper (I) oxides solar cells prepared by thermal oxidation method. The samples were oxidized at different oxidation temperatures and time. The different oxidation temperatures and lengths of time ware employed in ...

  8. Wet oxidation of quinoline

    DEFF Research Database (Denmark)

    Thomsen, A.B.; Kilen, H.H.

    1998-01-01

    The influence of oxygen pressure (0.4 and 2 MPa). reaction time (30 and 60 min) and temperature (260 and 280 degrees C) on the wet oxidation of quinoline has been studied. The dominant parameters for the decomposition of quinoline were oxygen pressure and reaction temperature. whereas the reaction...... time was less important within the range studied. Nitrifying bacteria were used to measure the inhibition from wet oxidative-treated samples to study the effect of the (wet oxidation) reaction conditions. Wet oxidation made quinoline more toxic to Nitrosomonas. This was observed for Nitrobacter as well....... The combined wet oxidation and biological treatment of reaction products resulted in 91% oxidation of the parent compound to CO2 and water. Following combined wet oxidation and biological treatment the sample showed low toxicity towards Nitrosomonas and no toxicity towards Nitrobacter. (C) 1998 Elsevier...

  9. Oxidation Resistant Graphite Studies

    Energy Technology Data Exchange (ETDEWEB)

    W. Windes; R. Smith

    2014-07-01

    The Very High Temperature Reactor (VHTR) Graphite Research and Development Program is investigating doped nuclear graphite grades exhibiting oxidation resistance. During a oxygen ingress accident the oxidation rates of the high temperature graphite core region would be extremely high resulting in significant structural damage to the core. Reducing the oxidation rate of the graphite core material would reduce the structural effects and keep the core integrity intact during any air-ingress accident. Oxidation testing of graphite doped with oxidation resistant material is being conducted to determine the extent of oxidation rate reduction. Nuclear grade graphite doped with varying levels of Boron-Carbide (B4C) was oxidized in air at nominal 740°C at 10/90% (air/He) and 100% air. The oxidation rates of the boronated and unboronated graphite grade were compared. With increasing boron-carbide content (up to 6 vol%) the oxidation rate was observed to have a 20 fold reduction from unboronated graphite. Visual inspection and uniformity of oxidation across the surface of the specimens were conducted. Future work to determine the remaining mechanical strength as well as graphite grades with SiC doped material are discussed.

  10. Biomimetic Water-Oxidation Catalysts: Manganese Oxides.

    Science.gov (United States)

    Kurz, Philipp

    2016-01-01

    The catalytic oxidation of water to molecular oxygen is a key process for the production of solar fuels. Inspired by the biological manganese-based active site for this reaction in the enzyme Photosystem II, researchers have made impressive progress in the last decades regarding the development of synthetic manganese catalysts for water oxidation. For this, it has been especially fruitful to explore the many different types of known manganese oxides MnOx. This chapter first offers an overview of the structural, thermodynamic, and mechanistic aspects of water-oxidation catalysis by MnOx. The different test systems used for catalytic studies are then presented together with general reactivity trends. As a result, it has been possible to identify layered, mixed Mn (III/IV)-oxides as an especially promising class of bio-inspired catalysts and an attempt is made to give structure-based reasons for the good performances of these materials. In the outlook, the challenges of catalyst screenings (and hence the identification of a "best MnOx catalyst") are discussed. There is a great variety of reaction conditions which might be relevant for the application of manganese oxide catalysts in technological solar fuel-producing devices, and thus catalyst improvements are currently still addressing a very large parameter space. Nonetheless, detailed knowledge about the biological catalyst and a solid experimental basis concerning the syntheses and water-oxidation reactivities of MnOx materials have been established in the last decade and thus this research field is well positioned to make important contributions to solar fuel research in the future.

  11. Barium oxide, calcium oxide, magnesia, and alkali oxide free glass

    Science.gov (United States)

    Lu, Peizhen Kathy; Mahapatra, Manoj Kumar

    2013-09-24

    A glass composition consisting essentially of about 10-45 mole percent of SrO; about 35-75 mole percent SiO.sub.2; one or more compounds from the group of compounds consisting of La.sub.2O.sub.3, Al.sub.2O.sub.3, B.sub.2O.sub.3, and Ni; the La.sub.2O.sub.3 less than about 20 mole percent; the Al.sub.2O.sub.3 less than about 25 mole percent; the B.sub.2O.sub.3 less than about 15 mole percent; and the Ni less than about 5 mole percent. Preferably, the glass is substantially free of barium oxide, calcium oxide, magnesia, and alkali oxide. Preferably, the glass is used as a seal in a solid oxide fuel/electrolyzer cell (SOFC) stack. The SOFC stack comprises a plurality of SOFCs connected by one or more interconnect and manifold materials and sealed by the glass. Preferably, each SOFC comprises an anode, a cathode, and a solid electrolyte.

  12. Oxidizer Scoping Studies

    Energy Technology Data Exchange (ETDEWEB)

    Chancellor, Christopher John [Los Alamos National Laboratory

    2016-11-07

    The purpose of this report is to present the results of the acceptable knowledge (AK) review of oxidizers present in active waste streams, provide a technical analysis of the oxidizers, and report the results of the scoping study testing. This report will determine the fastest burning oxidizer to be used in the development of a Test Plan for Preparation and Testing of Sorbents Mixed with Oxidizer found in Transuranic Waste (DWT-TP-001). The companion report, DWT-RPT-002, Sorbent Scoping Studies, contains similar information for sorbents identified during the AK review of TRU waste streams. The results of the oxidizer and sorbent scoping studies will be used to inform the QL1 test plan. The QL1 test results will support the development of a basis of knowledge document that will evaluate oxidizing chemicals and sorbents in TRU waste and provide guidance for treatment.

  13. METAL OXIDE NANOPARTICLES

    Energy Technology Data Exchange (ETDEWEB)

    FERNANDEZ-GARCIA,M.; RODGRIGUEZ, J.A.

    2007-10-01

    This chapter covers the fundamental science, synthesis, characterization, physicochemical properties and applications of oxide nanomaterials. Explains fundamental aspects that determine the growth and behavior of these systems, briefly examines synthetic procedures using bottom-up and top-down fabrication technologies, discusses the sophisticated experimental techniques and state of the art theory results used to characterize the physico-chemical properties of oxide solids and describe the current knowledge concerning key oxide materials with important technological applications.

  14. Molecular water oxidation catalysis

    CERN Document Server

    Llobet, Antoni

    2014-01-01

    Photocatalytic water splitting is a promising strategy for capturing energy from the sun by coupling light harvesting and the oxidation of water, in order to create clean hydrogen fuel. Thus a deep knowledge of the water oxidation catalysis field is essential to be able to come up with useful energy conversion devices based on sunlight and water splitting. Molecular Water Oxidation Catalysis: A Key Topic for New Sustainable Energy Conversion Schemes presents a comprehensive and state-of-the-art overview of water oxidation catalysis in homogeneous phase, describing in detail the most importan

  15. Cosmological billiards and oxidation

    International Nuclear Information System (INIS)

    De Buyl, S.; Paulot, L.; Henneaux, M.; Julia, B.

    2004-01-01

    We show how the properties of the cosmological billiards provide useful information (spacetime dimension and p-form spectrum) on the oxidation endpoint of the oxidation sequence of gravitational theories. We compare this approach to the other available methods: GL(n,R) subgroups and the superalgebras of dualities. (Abstract Copyright [2004], Wiley Periodicals, Inc.)

  16. Catalyst for Ammonia Oxidation

    DEFF Research Database (Denmark)

    2015-01-01

    The present invention relates to a bimetallic catalyst for ammonia oxidation, a method for producing a bimetallic catalyst for ammonia oxidation and a method for tuning the catalytic activity of a transition metal. By depositing an overlayer of less catalytic active metal onto a more catalytic...

  17. Monolithic metal oxide transistors.

    Science.gov (United States)

    Choi, Yongsuk; Park, Won-Yeong; Kang, Moon Sung; Yi, Gi-Ra; Lee, Jun-Young; Kim, Yong-Hoon; Cho, Jeong Ho

    2015-04-28

    We devised a simple transparent metal oxide thin film transistor architecture composed of only two component materials, an amorphous metal oxide and ion gel gate dielectric, which could be entirely assembled using room-temperature processes on a plastic substrate. The geometry cleverly takes advantage of the unique characteristics of the two components. An oxide layer is metallized upon exposure to plasma, leading to the formation of a monolithic source-channel-drain oxide layer, and the ion gel gate dielectric is used to gate the transistor channel effectively at low voltages through a coplanar gate. We confirmed that the method is generally applicable to a variety of sol-gel-processed amorphous metal oxides, including indium oxide, indium zinc oxide, and indium gallium zinc oxide. An inverter NOT logic device was assembled using the resulting devices as a proof of concept demonstration of the applicability of the devices to logic circuits. The favorable characteristics of these devices, including (i) the simplicity of the device structure with only two components, (ii) the benign fabrication processes at room temperature, (iii) the low-voltage operation under 2 V, and (iv) the excellent and stable electrical performances, together support the application of these devices to low-cost portable gadgets, i.e., cheap electronics.

  18. Synthesis of Polyimides Curable by Intramolecular Cycloaddition

    Science.gov (United States)

    1977-03-01

    5.17; N, 6.90; mol. wt., 384 (by mass spectrometry). c. 2’-Iodo-4!nitroacetanilide 2’-Iodo-4- acetanilide has been previously prepared in two steps...water, and the precipitate formed was stirred for one hour, filtered, washed with water, dried under suction, and recrystallized from ethanol to afford...5,5’dinitrobiphenyl. An analytical sample, m.p. 263-265°C, was obtained by recrystallization from ethanol. Anal. Calcd. for C16 H1 4 N4 04 : C, 53.60

  19. Regio and stereoselectivity in ionic cycloadditions

    Indian Academy of Sciences (India)

    WINTEC

    to be more reactive than DMIQ as a diene and as a dienophile MVE is found to be more reactive than PY. Computed bond orders establish that the syn 2 ... of many carbocycles, heterocycles, less reactive π systems and heteromultiple bonds. 2 ... been calculated from the Wiberg. 16 indices using NBO analysis and from ...

  20. Theoretical insights into the cycloaddition reaction mechanism ...

    Indian Academy of Sciences (India)

    cSchool of Chemistry and Chemical Engineering, Qufu Normal University, Qufu, Shandong, 273165,. People's Republic of China e-mail: chem.2001@163.com; lpsdu@sdu.edu.cn .... are both interstellar molecules.20. Accordingly, we postulate that the reaction of keten- imine and methyleneimine may be one of the forma-.

  1. cycloaddition reactions: An assessment of reactivity descriptors

    Indian Academy of Sciences (India)

    Unknown

    The global electrophilicity index is given by ω = µ2/2η,. (8) where µ = (εHOMO + εLUMO) and η = εLUMO – εHOMO. The local electrophilicity index (ωk), which gives the maximum electrophilicity power in a molecule devel- oped at a particular site, is given by ω+ k = f + k, for nucleophilic attack,. (9) ω– k = f – k, for electrophilic ...

  2. Theoretical insights into the cycloaddition reaction mechanism ...

    Indian Academy of Sciences (India)

    , People's Republic of China; College of Biological Science and Technology, University of Jinan, Jinan, Shandong, 250022, People's Republic of China; School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu, Shandong ...

  3. Photochemical cycloaddition reactions of cyanoacetylene and dicyanoacetylene

    Science.gov (United States)

    Ferris, J. P.; Guillemin, J. C.

    1990-01-01

    Photolysis of cyanoacetylene with 185- or 206-nm light yields 1,3,5-tricyanobenzene while 254-nm radiation yields a mixture of tetracyanocyclooctatetraenes, 1,2,4- and 1,3,5-tricyanobenzene. A polymer of cyanoacetylene is the major photoproduct. 1,3,5-Tricarbomethoxybenzene was the only photoproduct identified from the irradiation of methyl propiolate at 254 nm. Mono-, di-, and tricyanobenzenes are formed by irradiation of mixtures of acetylene and cyanoacetylene at 185, 206, and 254 nm along with trace amounts of cyclooctatetraenes. No photoadducts were detected on photolysis of mixtures of cyanoacetylene and CO or HCN. The tetracyanocyclooctatetraene structures were established by UV, MS, and NMR analyses. The 1H NMR of the product mixture exhibited a singlet at delta 7.028 consistent with either 1 or 2 and two singlets at delta 6.85 and 6.91 assigned to 3. Photolysis of mixtures of dicyanoacetylene and acetylene with either 185- or 206-nm light yielded 1,2-dicyanobenzene and (E,Z)-1-buten-3-yne-1,4-dicarbonitrile. These products were also obtained using 254-nm light along with a mixture of tetracyanocyclooctatetraenes. The same three singlets were observed in this product mixture as were observed in the tetracyanocyclooctatetraenes obtained from cyanoacetylene. From this observation it was concluded that the delta 7.02 signal is due to 2 and not 1. The photolysis of cyanoacetylene and dicyanoacetylene in the presence of ethylene with 185-nm light yields 1-cyanocylobutene and 1,2-dicyanocyclobutene, respectively. 2-Cyanobutadiene and 2,3-dicyanobutadiene are the photoproducts with 254-nm light. Reaction pathways are proposed to explain these findings.

  4. Death from Nitrous Oxide.

    Science.gov (United States)

    Bäckström, Björn; Johansson, Bengt; Eriksson, Anders

    2015-11-01

    Nitrous oxide is an inflammable gas that gives no smell or taste. It has a history of abuse as long as its clinical use, and deaths, although rare, have been reported. We describe two cases of accidental deaths related to voluntary inhalation of nitrous oxide, both found dead with a gas mask covering the face. In an attempt to find an explanation to why the victims did not react properly to oncoming hypoxia, we performed experiments where a test person was allowed to breath in a closed system, with or without nitrous oxide added. Vital signs and gas concentrations as well as subjective symptoms were recorded. The experiments indicated that the explanation to the fact that neither of the descendents had reacted to oncoming hypoxia and hypercapnia was due to the inhalation of nitrous oxide. This study raises the question whether nitrous oxide really should be easily, commercially available. © 2015 American Academy of Forensic Sciences.

  5. Protein oxidation in aquatic foods

    DEFF Research Database (Denmark)

    Baron, Caroline P.

    2014-01-01

    The chapter discusses general considerations about protein oxidation and reviews the mechanisms involved in protein oxidation and consequences of protein oxidation on fish proteins. It presents two case studies, the first deals with protein and lipid oxidation in frozen rainbow trout......, and the second with oxidation in salted herring. The mechanisms responsible for initiation of protein oxidation are unclear, but it is generally accepted that free radical species initiating lipid oxidation can also initiate protein oxidation. The chapter focuses on interaction between protein and lipid...... oxidation. The protein carbonyl group measurement is the widely used method for estimating protein oxidation in foods and has been used in fish muscle. The chapter also talks about the impact of protein oxidation on protein functionality, fish muscle texture, and food nutritional value. Protein oxidation...

  6. Oxide Nanocrystal Model Catalysts.

    Science.gov (United States)

    Huang, Weixin

    2016-03-15

    Model catalysts with uniform and well-defined surface structures have been extensively employed to explore structure-property relationships of powder catalysts. Traditional oxide model catalysts are based on oxide single crystals and single crystal thin films, and the surface chemistry and catalysis are studied under ultrahigh-vacuum conditions. However, the acquired fundamental understandings often suffer from the "materials gap" and "pressure gap" when they are extended to the real world of powder catalysts working at atmospheric or higher pressures. Recent advances in colloidal synthesis have realized controlled synthesis of catalytic oxide nanocrystals with uniform and well-defined morphologies. These oxide nanocrystals consist of a novel type of oxide model catalyst whose surface chemistry and catalysis can be studied under the same conditions as working oxide catalysts. In this Account, the emerging concept of oxide nanocrystal model catalysts is demonstrated using our investigations of surface chemistry and catalysis of uniform and well-defined cuprous oxide nanocrystals and ceria nanocrystals. Cu2O cubes enclosed with the {100} crystal planes, Cu2O octahedra enclosed with the {111} crystal planes, and Cu2O rhombic dodecahedra enclosed with the {110} crystal planes exhibit distinct morphology-dependent surface reactivities and catalytic properties that can be well correlated with the surface compositions and structures of exposed crystal planes. Among these types of Cu2O nanocrystals, the octahedra are most reactive and catalytically active due to the presence of coordination-unsaturated (1-fold-coordinated) Cu on the exposed {111} crystal planes. The crystal-plane-controlled surface restructuring and catalytic activity of Cu2O nanocrystals were observed in CO oxidation with excess oxygen. In the propylene oxidation reaction with O2, 1-fold-coordinated Cu on Cu2O(111), 3-fold-coordinated O on Cu2O(110), and 2-fold-coordinated O on Cu2O(100) were identified

  7. Oxidants for uranium leaching

    International Nuclear Information System (INIS)

    Ho, E.; Ring, B.

    2007-01-01

    Most uranium ores are leached with sulfuric acid under oxidising conditions. This paper reviews the oxidants that have been traditionally used in uranium leaching and discusses their merits in the context of overall flow sheet considerations. Options for alternative oxidants are also discussed. In acid leaching, ferric ion in solution oxidises insoluble uranium(IV) to soluble uranium (VI). Though ferric ion may be added directly, usually an oxidant is added to the circuit to convert ferrous ion to ferric ion in the liquor so that leaching can continue. The most common oxidants are pyrolusite and sodium chlorate. Pyrolusite is relatively cheap but introduces manganese ions into the liquor and consumes twice as much acid as sodium chlorate. Sodium chlorate is a slow reacting oxidant at low temperatures and acidities, and introduces chloride into the leach liquor. Caro's acid, is a non-polluting reagent that was used successfully at the Nabarlek uranium mine, and provided very good control of oxidising conditions. Other oxidants that are now being considered to overcome the disadvantages of pyrolusite and sodium chlorate are oxygen, hydrogen peroxide and SO 2 /O 2 . Some performance data for these oxidants are presented

  8. Markers of protein oxidation

    DEFF Research Database (Denmark)

    Headlam, Henrietta A; Davies, Michael Jonathan

    2004-01-01

    Exposure of proteins to radicals in the presence of O2 gives both side-chain oxidation and backbone fragmentation. These processes can be interrelated, with initial side-chain oxidation giving rise to backbone damage via transfer reactions. We have shown previously that alkoxyl radicals formed...... on the C-3 carbons of Ala, Val, Leu, and Asp residues undergo beta-scission to give backbone alpha-carbon radicals, with the release of the side- chain as a carbonyl compound. We now show that this is a general mechanism that occurs with a wide range of oxidants. The quantitative significance...... of this process depends on the extent of oxidation at C-3 compared with other sites. HO*, generated by gamma radiolysis, gave the highest total carbonyl yield, with protein-bound carbonyls predominating over released. In contrast, metal ion/H2O2 systems, gave more released than bound carbonyls, with this ratio...

  9. Protein oxidation and peroxidation

    DEFF Research Database (Denmark)

    Davies, Michael Jonathan

    2016-01-01

    Proteins are major targets for radicals and two-electron oxidants in biological systems due to their abundance and high rate constants for reaction. With highly reactive radicals damage occurs at multiple side-chain and backbone sites. Less reactive species show greater selectivity with regard...... and modified turnover. In the presence of O2, high yields of peroxyl radicals and peroxides (protein peroxidation) are formed; the latter account for up to 70% of the initial oxidant flux. Protein peroxides can oxidize both proteins and other targets. One-electron reduction results in additional radicals...... and chain reactions with alcohols and carbonyls as major products; the latter are commonly used markers of protein damage. Direct oxidation of cysteine (and less commonly) methionine residues is a major reaction; this is typically faster than with H2O2, and results in altered protein activity and function...

  10. High Current Oxide Cathodes

    National Research Council Canada - National Science Library

    Luhmann, N

    2000-01-01

    The aim of the AASERT supported research is to develop the plasma deposition/implantation process for coating barium, strontium and calcium oxides on nickel substrates and to perform detailed surface...

  11. High Current Oxide Cathodes

    National Research Council Canada - National Science Library

    Luhmann, N

    2000-01-01

    .... The vacuum are plasma deposition gun developed at Lawrence Berkeley National Laboratory (LBNL) has been used to deposit oxides and nitrides with very precise control over deposition rate and composition.

  12. CATALYTIC ENANTIOSELECTIVE ALLYLIC OXIDATION

    NARCIS (Netherlands)

    Rispens, Minze T.; Zondervan, Charon; Feringa, Bernard

    Several chiral Cu(II)-complexes of cyclic amino acids catalyse the enantioselective allylic oxidation of cyclohexene to cyclohexenyl esters. Cyclohexenyl propionate was obtained in 86% yield with e.e.'s up to 61%.

  13. Titanium oxide fever

    International Nuclear Information System (INIS)

    De Jonge, D.; Visser, J.

    2012-01-01

    One measure to improve air quality is to apply photo-catalytic substances that capture NOx onto the road surface or onto baffle boards alongside the roads. The effect of titanium oxide containing clinkers with coating was discussed in the report 'Demonstration project of air-purifying pavement in Hengelo, The Netherlands' that was published in May 2011. This article examines the way in which the effectiveness of this study was determined. Can titanium oxide containing clinkers and coatings indeed capture NOx?. [nl

  14. Thin zirconium oxides

    International Nuclear Information System (INIS)

    Oviedo, Cristina

    2000-01-01

    Polycrystalline Zr and two pure Zr single-crystal samples, one oriented with the normal to the surface parallel to the c-axis of the hcp structure (Z1) and the other with the normal perpendicular to c (Z2), were oxidised at 10 -8 , 10 -7 and 10 -6 Torr and room temperature. Oxidation kinetics, composition and thicknesses of the oxide films formed in each case were analyzed using XPS (X-ray Photoelectron Spectroscopy) as the main technique. The oxidation kinetics followed logarithmic laws in all cases. The deconvolution of XPS Zr3d peaks indicated the formation of two Zr-O compounds before the formation of ZrO 2 . Varying the photoelectrons take-off angle, the compound distribution inside the oxide films could be established. Thus, it was confirmed that the most external oxide, in contact with the gas, was ZrO 2 . The thickness of the films grown at the different pressures was determined. In the polycrystalline samples, thicknesses between 15 and 19 ± 2Angstroem were obtained for pressures between 10 -8 and 10 -6 Torr, in close coincidence with the determined ones for Z2. The thicknesses measured in Z1 were smaller, reaching 13 ± 2Angstroem for the oxidations performed at 10 -6 Torr. (author)

  15. Porous ceramics out of oxides

    International Nuclear Information System (INIS)

    Bakunov, V.S.; Balkevich, V.L.; Vlasov, A.S.; Guzman, I.Ya.; Lukin, E.S.; Poluboyarinov, D.N.; Poliskij, R.Ya.

    1977-01-01

    A review is made of manufacturing procedures and properties of oxide ceramics intended for high-temperature thermal insulation and thermal protection applications. Presented are structural characteristics of porous oxide refractories and their properties. Strength and thermal conductivity was shown to depend upon porosity. Described is a procedure for manufacturing porous ceramic materials from aluminium oxide, zirconium dioxide, magnesium oxide, beryllium oxide. The thermal resistance of porous ceramics from BeO is considerably greater than that of other high-refractoriness oxides. Listed are areas of application for porous materials based on oxides

  16. Study of the Effect of Grafting Method on Surface Polarity of Tempo-Oxidized Nanocellulose Using Polycaprolactone as the Modifying Compound: Esterification versus Click-Chemistry

    Directory of Open Access Journals (Sweden)

    Abdelhaq Benkaddour

    2013-12-01

    Full Text Available Esterification and click-chemistry were evaluated as surface modification treatments for TEMPO-oxidized nanocelluloses (TONC using Polycaprolactone-diol (PCL as modifying compound in order to improve the dispersion of nanofibers in organic media. These two grafting strategies were analyzed and compared. The first consists of grafting directly the PCL onto TONC, and was carried out by esterification between hydroxyl groups of PCL and carboxyl groups of TONC. The second strategy known as click-chemistry is based on the 1,3-dipolar cycloaddition reaction between azides and alkyne terminated moieties to form the triazole ring between PCL and TONC. The grafted samples were characterized by transmission electron microscopy (TEM, Fourier transform infrared spectroscopy (FTIR, X-ray photoelectron spectroscopy (XPS, and Thermogravimetry analysis (TGA. Further, the effects of the two treatments on the surface hydrophobization of TONC were investigated by contact angle measurements. The results show that both methods confirm the success of such a modification and the click reaction was significantly more effective than esterification.

  17. Enzymatic halogenation and oxidation using an alcohol oxidase-vanadium chloroperoxidase cascade

    NARCIS (Netherlands)

    But, Andrada; Noord, Van Aster; Poletto, Francesca; Sanders, Johan P.M.; Franssen, Maurice C.R.; Scott, Elinor L.

    2017-01-01

    The chemo-enzymatic cascade which combines alcohol oxidase from Hansenula polymorpha (AOXHp) with vanadium chloroperoxidase (VCPO), for the production of biobased nitriles from amino acids was investigated. In the first reaction H2O2 (and acetaldehyde) are generated from ethanol and oxygen by AOXHp.

  18. Single sheet iron oxides

    DEFF Research Database (Denmark)

    Yin, Zhou

    activity. LDH single sheets have been reported to be effective sorbents, catalysts in electrochemical and photochemical reactions, and building thin films together with other nanomaterials for designing new functionalities. Here we focus on the delamination of FeII-FeIII LDHs into single sheet iron oxide...... was rapid compared to other iron oxides, reaching equilibrium within 60 minutes. Arsenic sorption and acid-base titration data could be successfully described with a 1pk Basic Stern Model (BSM). The point of zero charge was around 8. The intrinsic surface complexation equilibrium constants (log K...... became abundant at low pH. (3) Electrochemical reduction of chlorinated compounds using an SSI modified electrode. Here, the electrochemical reactivity of SSIs coated on indium tin oxide coated glass electrodes was investigated. Iron on the SSI modified electrode showed a typical Cyclic Voltammetry...

  19. Volume reduction by oxidation

    International Nuclear Information System (INIS)

    Kuribayashi, H.; Hasegawa, A.; Koshiba, Y.; Yamanaka, A.

    1984-01-01

    JGC Corporation has been actively investigating the treatment of various combustible and organic wastes generated at nuclear power stations and reprocessing plants. In particular, JGC has analyzed three new technologies which produce dramatic volume reductions and complete conversion of wastes into inorganic substances for durable storage and disposal. Those technologies are; Incineration, Wet oxidation and Photooxidation. Incineration is an excellent volume reducer for combustible wastes, and wet oxidation, using hydrogen peroxide, is also a good way for reducing spent ion-exchange resins without any off-gas problems. Photooxidation is a new technology to purify polluted water for recycled use in the stations without th release of contaminated water to the environment. Polluted water may include NH4+, detergents, chelating agents and other organic decontamination agents. These VR technologies are all based on ''Oxidation'' from which the title of this paper comes

  20. Methanol partial oxidation reformer

    Science.gov (United States)

    Ahmed, Shabbir; Kumar, Romesh; Krumpelt, Michael

    1999-01-01

    A partial oxidation reformer comprising a longitudinally extending chamber having a methanol, water and an air inlet and an outlet. An igniter mechanism is near the inlets for igniting a mixture of methanol and air, while a partial oxidation catalyst in the chamber is spaced from the inlets and converts methanol and oxygen to carbon dioxide and hydrogen. Controlling the oxygen to methanol mole ratio provides continuous slightly exothermic partial oxidation reactions of methanol and air producing hydrogen gas. The liquid is preferably injected in droplets having diameters less than 100 micrometers. The reformer is useful in a propulsion system for a vehicle which supplies a hydrogen-containing gas to the negative electrode of a fuel cell.

  1. Ethylene Oxide Gaseous Sterilization

    Science.gov (United States)

    Ernst, Robert R.; Shull, James J.

    1962-01-01

    The duration of the equilibration period between admission of water vapor and subsequent introduction of gaseous ethylene oxide to an evacuated sterilizer chamber was studied with respect to its effect on the inactivation of spores of Bacillus subtilis var. niger under simulated practical conditions. Introduction of a water-adsorbing cotton barrier between the spores and an incoming gas mixture of water vapor and ethylene oxide caused a marked increase in the observed thermochemical death time of the spore populations. This effect was negated by admission of water vapor one or more minutes prior to introduction of ethylene oxide gas. Increases in temperature and relative humidity of the system promoted passage of water vapor through the cotton barriers and diminished their effect. PMID:13890660

  2. Oxidation of orthopaedic UHMWPE.

    Science.gov (United States)

    Costa, L; Jacobson, K; Bracco, P; Brach del Prever, E M

    2002-04-01

    Retrieved EtO sterilised acetabular cups usually show much less degradation than gamma-ray sterilised cups. Some of our retrieved EtO sterilised cups did, however, reveal unexpected bulk oxidation. It was observed that this oxidation was always accompanied by whitening of the material. This whitening was found to be due to a break-up of the compression moulded material into its original particles. It was noticed that there was no oxidation in all parts, where the break-up and whitening appeared. The oxidation did, however, occur exclusively in the parts where there was a badly consolidated material. Upon examining shelf aged, unsterilised samples, it was found that the degradation was also present here. This shows that the observed phenomenon is not due to the service in vivo and that it must originate from the processing step. Just as for the retrieved samples, the shelf aged cups only showed oxidation in the bulk and not at the surface. It was concluded that the material used for the cups had been badly fused together during the compression moulding and that the machining had created a bad stress situation in the cups leading to a break-up of the particles. The mechanism that initiates the oxidation is not known, but it is believed that the distribution depends on how the internal stresses have acted to break up the structure. In the areas where the particles have been separated, there is probably a higher availability of oxygen than what is normally observed in UHMWPE.

  3. Synthesis and Characterization of 5-Substituted 1H-Tetrazoles in the ...

    African Journals Online (AJOL)

    NICOLAAS

    cycloaddition of nitriles and sodium azide, Polyhedron, 2011, 30,. 2606–2610. 18 J. He, B. Li, F. Chen, Z. Xu and G. Yin, Tungstates: Novel heteroge- neous catalysts for the synthesis of 5-substituted 1H-tetrazoles, J. mol. Catal. A., 2009, 304, 135–138. 19 S.M. Sajadi, M. Naderi and S. Babadoust, Nano TiO2 as an efficient.

  4. Photo-patterning of non-fouling polymers and biomolecules on paper

    Czech Academy of Sciences Publication Activity Database

    Tischer, T.; Rodriguez-Emmenegger, Cesar; Trouillet, V.; Welle, A.; Schueler, V.; Mueller, J. O.; Goldmann, A. S.; Brynda, Eduard; Barner-Kowollik, C.

    2014-01-01

    Roč. 26, č. 24 (2014), s. 4087-4092 ISSN 0935-9648 R&D Projects: GA ČR GAP205/12/1702; GA MŠk(CZ) LH13178; GA MŠk(CZ) ED1.1.00/02.0109 Institutional support: RVO:61389013 Keywords : bioactive paper * micropatterning * nitrile imine-mediated tetrazole-ene cycloaddition (NITEC) Subject RIV: CD - Macromolecular Chemistry Impact factor: 17.493, year: 2014

  5. Controlled cell adhesion on poly(dopamine) interfaces photopatterned with non-fouling brushes

    Czech Academy of Sciences Publication Activity Database

    Rodriguez-Emmenegger, C.; Preuss, C. M.; Yameen, B.; Pop-Georgievski, Ognen; Bachmann, M.; Mueller, J. O.; Bruns, M.; Goldmann, A. S.; Bastmeyer, M.; Barner-Kowollik, C.

    2013-01-01

    Roč. 25, č. 42 (2013), s. 6123-6127 ISSN 0935-9648 R&D Projects: GA ČR GAP205/12/1702; GA ČR GAP106/12/1451; GA ČR GAP108/11/1857 Institutional support: RVO:61389013 Keywords : micropatterning * nitrile imine-mediated tetrazole-ene cycloaddition (NITEC) * photoligation Subject RIV: CD - Macromolecular Chemistry Impact factor: 15.409, year: 2013

  6. Oxidation by metal salts

    International Nuclear Information System (INIS)

    Makhon'kov, D.I.; Cheprakov, A.V.; Rodkin, M.A.; Mil'chenko, A.Yu.; Beletskaya, I.P.

    1986-01-01

    Oxidation of toluene and para-substituted toluenes containing electron acceptor groups: p-toluic acid, p-methyltoluylate and p-nitrotoluene by ammonium cerium (4) nitrate and ammonium cerium (4) sulfate in aqueous solutions of trifluoroacetic acid in the presence of chlorides and bromides of alkali metals is studied. The rate and selectivity of oxidative halogenation in side chain and/or aromatic ring under the conditions studied depend both on the nature of substrate and halogenide-ion and on the reaction conditions and ligand surrounding of cerium (4) atom

  7. Sintering of beryllium oxide

    International Nuclear Information System (INIS)

    Caillat, R.; Pointud, R.

    1955-01-01

    This study had for origin to find a process permitting to manufacture bricks of beryllium oxide of pure nuclear grade, with a density as elevated as possible and with standardized shape. The sintering under load was the technique kept for the manufacture of the bricks. Because of the important toxicity of the beryllium oxide, the general features for the preliminary study of the sintering, have been determined while using alumina. The obtained results will be able to act as general indication for ulterior studies with sintering under load. (M.B.) [fr

  8. Uranium oxidation: characterization of oxides formed by reaction with water

    International Nuclear Information System (INIS)

    Fuller, E.L. Jr.; Smyrl, N.R.; Condon, J.B.; Eager, M.H.

    1983-01-01

    Three different uranium oxide samples have been characterized with respect to the different preparation techniques. Results show that the water reaction with uranium metal occurs cyclically forming laminar layers of oxide which spall off due to the strain at the oxide/metal interface. Single laminae are released if liquid water is present due to the prizing penetration at the reaction zone. The rate of reaction of water with uranium is directly proportional to the amount of adsorbed water on the oxide product. Rapid transport is effected through the open hydrous oxide product. Dehydration of the hydrous oxide irreversibly forms a more inert oxide which cannot be rehydrated to the degree that prevails in the original hydrous product of uranium oxidation with water. 27 figures

  9. Uranium oxidation: characterization of oxides formed by reaction with water

    Energy Technology Data Exchange (ETDEWEB)

    Fuller, E.L. Jr.; Smyrl, N.R.; Condon, J.B.; Eager, M.H.

    1983-04-27

    Three different uranium oxide samples have been characterized with respect to the different preparation techniques. Results show that the water reaction with uranium metal occurs cyclically forming laminar layers of oxide which spall off due to the strain at the oxide/metal interface. Single laminae are released if liquid water is present due to the prizing penetration at the reaction zone. The rate of reaction of water with uranium is directly proportional to the amount of adsorbed water on the oxide product. Rapid transport is effected through the open hydrous oxide product. Dehydration of the hydrous oxide irreversibly forms a more inert oxide which cannot be rehydrated to the degree that prevails in the original hydrous product of uranium oxidation with water. 27 figures.

  10. Green oxidations: Titanium dioxide induced tandem oxidation coupling reactions

    OpenAIRE

    Jeena, Vineet; Robinson, Ross S

    2009-01-01

    Summary The application of titanium dioxide as an oxidant in tandem oxidation type processes is described. Under microwave irradiation, quinoxalines have been synthesized in good yields from the corresponding ?-hydroxyketones.

  11. Protein oxidation and ageing

    DEFF Research Database (Denmark)

    Linton, S; Davies, Michael Jonathan; Dean, R T

    2001-01-01

    of redox-active metal ions that could catalyse oxidant formation. As a result of this decrease in antioxidant defences, and increased rate of ROS formation, it is possible that the impact of ROS increases with age. ROS are known to oxidise biological macromolecules, with proteins an important target...

  12. Solid Oxide Fuel Cell

    DEFF Research Database (Denmark)

    2010-01-01

    The solid oxide fuel cell comprising a metallic support material, an active anode layer consisting of a good hydrocarbon cracking catalyst, an electrolyte layer, an active cathode layer, and a transition layer consisting of preferably a mixture of LSM and a ferrite to the cathode current collector...

  13. Oxidative stress in myopia.

    Science.gov (United States)

    Francisco, Bosch-Morell; Salvador, Mérida; Amparo, Navea

    2015-01-01

    Myopia affected approximately 1.6 billion people worldwide in 2000, and it is expected to increase to 2.5 billion by 2020. Although optical problems can be corrected by optics or surgical procedures, normal myopia and high myopia are still an unsolved medical problem. They frequently predispose people who have them to suffer from other eye pathologies: retinal detachment, glaucoma, macular hemorrhage, cataracts, and so on being one of the main causes of visual deterioration and blindness. Genetic and environmental factors have been associated with myopia. Nevertheless, lack of knowledge in the underlying physiopathological molecular mechanisms has not permitted an adequate diagnosis, prevention, or treatment to be found. Nowadays several pieces of evidence indicate that oxidative stress may help explain the altered regulatory pathways in myopia and the appearance of associated eye diseases. On the one hand, oxidative damage associated with hypoxia myopic can alter the neuromodulation that nitric oxide and dopamine have in eye growth. On the other hand, radical superoxide or peroxynitrite production damage retina, vitreous, lens, and so on contributing to the appearance of retinopathies, retinal detachment, cataracts and so on. The objective of this review is to suggest that oxidative stress is one of the key pieces that can help solve this complex eye problem.

  14. Dopamine Oxidation and Autophagy

    Directory of Open Access Journals (Sweden)

    Patricia Muñoz

    2012-01-01

    Full Text Available The molecular mechanisms involved in the neurodegenerative process of Parkinson's disease remain unclear. Currently, there is a general agreement that mitochondrial dysfunction, α-synuclein aggregation, oxidative stress, neuroinflammation, and impaired protein degradation are involved in the neurodegeneration of dopaminergic neurons containing neuromelanin in Parkinson's disease. Aminochrome has been proposed to play an essential role in the degeneration of dopaminergic neurons containing neuromelanin by inducing mitochondrial dysfunction, oxidative stress, the formation of neurotoxic α-synuclein protofibrils, and impaired protein degradation. Here, we discuss the relationship between the oxidation of dopamine to aminochrome, the precursor of neuromelanin, autophagy dysfunction in dopaminergic neurons containing neuromelanin, and the role of dopamine oxidation to aminochrome in autophagy dysfunction in dopaminergic neurons. Aminochrome induces the following: (i the formation of α-synuclein protofibrils that inactivate chaperone-mediated autophagy; (ii the formation of adducts with α- and β-tubulin, which induce the aggregation of the microtubules required for the fusion of autophagy vacuoles and lysosomes.

  15. Partial Oxidation of n-Pentane over Vanadium Phosphorus Oxide ...

    African Journals Online (AJOL)

    NICOLAAS

    The selective oxidation ofn-pentane to value-added products, maleic anhydride or phthallic anhydride by vanadium phosphorus oxide loaded on hydroxyapatites as catalysts and oxygen as oxidant was investigated. Hydroxyapatite (HAp) and cobalt- hydroxyapatite (Co-HAp) were prepared by the co-precipitation method ...

  16. Nanostructured transition metal oxides useful for water oxidation catalysis

    Science.gov (United States)

    Frei, Heinz M; Jiao, Feng

    2013-12-24

    The present invention provides for a composition comprising a nanostructured transition metal oxide capable of oxidizing two H.sub.2O molecules to obtain four protons. In some embodiments of the invention, the composition further comprises a porous matrix wherein the nanocluster of the transition metal oxide is embedded on and/or in the porous matrix.

  17. Staged membrane oxidation reactor system

    Science.gov (United States)

    Repasky, John Michael; Carolan, Michael Francis; Stein, VanEric Edward; Chen, Christopher Ming-Poh

    2012-09-11

    Ion transport membrane oxidation system comprising (a) two or more membrane oxidation stages, each stage comprising a reactant zone, an oxidant zone, one or more ion transport membranes separating the reactant zone from the oxidant zone, a reactant gas inlet region, a reactant gas outlet region, an oxidant gas inlet region, and an oxidant gas outlet region; (b) an interstage reactant gas flow path disposed between each pair of membrane oxidation stages and adapted to place the reactant gas outlet region of a first stage of the pair in flow communication with the reactant gas inlet region of a second stage of the pair; and (c) one or more reactant interstage feed gas lines, each line being in flow communication with any interstage reactant gas flow path or with the reactant zone of any membrane oxidation stage receiving interstage reactant gas.

  18. Electrochemical analysis of metal oxides

    Czech Academy of Sciences Publication Activity Database

    Grygar, Tomáš; Bezdička, Petr; Hradil, David; Pikna, L.

    90-91, - (2003), s. 45-50 ISSN 1012-0394 Institutional research plan: CEZ:AV0Z4032918 Keywords : powder electroanalysis * Fe oxides * Mn oxides Subject RIV: CA - Inorganic Chemistry Impact factor: 0.687, year: 2003

  19. Thin film metal-oxides

    CERN Document Server

    Ramanathan, Shriram

    2009-01-01

    Presents an account of the fundamental structure-property relations in oxide thin films. This title discusses the functional properties of thin film oxides in the context of applications in the electronics and renewable energy technologies.

  20. Self-assembled manganese oxide structures through direct oxidation

    KAUST Repository

    Zhao, Chao

    2012-12-01

    The morphology and phase of self-assembled manganese oxides during different stages of thermal oxidation were studied. Very interesting morphological patterns of Mn oxide films were observed. At the initial oxidation stage, the surface was characterized by the formation of ring-shaped patterns. As the oxidation proceeded to the intermediate stage, concentric plates formed to relax the compressive stress. Our experimental results gave a clear picture of the evolution of the structures. We also examined the properties of the structures. © 2012 Elsevier B.V.

  1. Oxidative Decarboxylation of Levulinic Acid by Cupric Oxides

    Directory of Open Access Journals (Sweden)

    Lu Lin

    2010-11-01

    Full Text Available In this paper, cupric oxides was found to effectively oxidize levulinic acid (LA and lead to the decarboxylation of levulinic acid to 2-butanone. The effects of cupric oxide dosage, reaction time and initial pH value were investigated in batch experiments and a plausible mechanism was proposed. The results showed that LA decarboxylation over cupric oxides at around 300 °C under acidic conditions produced the highest yield of butanone (67.5%. In order to elucidate the catalytic activity of cupric oxides, XRD, AFM, XPS and H2-TPR techniques was applied to examine their molecular surfaces and their effects on the reaction process.

  2. Low Temperature Oxidation of Methane: The Influence of Nitrogen Oxides

    DEFF Research Database (Denmark)

    Bendtsen, Anders Broe; Glarborg, Peter; Dam-Johansen, Kim

    2000-01-01

    An experimental investigation of methane oxidation in the presence of NO and NO2 has been made in an isothermal plug-flow reactor at 750-1250K. The temperature for on-set of oxidation was lowered by 250 K in the presence of NO or NO2 at residence times of 200 ms. At shorter residence times (140 ms......) this enhancement effect is reduced for NO but maintained for NO2. Furthermore two temperature regimes of oxidation separated by an intermediate regime where only little oxidation takes place exist at residence times of 140 ms, if NO is the only nitrogen oxide initially present. The results were explained...

  3. Oxidative decarboxylation of levulinic acid by cupric oxides.

    Science.gov (United States)

    Gong, Yan; Lin, Lu; Shi, Jianbin; Liu, Shijie

    2010-11-05

    In this paper, cupric oxides was found to effectively oxidize levulinic acid (LA) and lead to the decarboxylation of levulinic acid to 2-butanone. The effects of cupric oxide dosage, reaction time and initial pH value were investigated in batch experiments and a plausible mechanism was proposed. The results showed that LA decarboxylation over cupric oxides at around 300 °C under acidic conditions produced the highest yield of butanone (67.5%). In order to elucidate the catalytic activity of cupric oxides, XRD, AFM, XPS and H(2)-TPR techniques was applied to examine their molecular surfaces and their effects on the reaction process.

  4. Biomimetic PDMS-hydroxyurethane terminated with catecholic moieties for chemical grafting on transition metal oxide-based surfaces

    Science.gov (United States)

    de Aguiar, Kelen R.; Rischka, Klaus; Gätjen, Linda; Noeske, Paul-Ludwig Michael; Cavalcanti, Welchy Leite; Rodrigues-Filho, Ubirajara P.

    2018-01-01

    The aim of this work was to synthesize a non-isocyanate poly(dimethylsiloxane) hydroxyurethane with biomimetic terminal catechol moieties, as a candidate for inorganic and metallic surface modification. Such surface modifier is capable to strongly attach onto metallic and inorganic substrates forming layers and, in addition, providing water-repellent surfaces. The non-isocyanate route is based on carbon dioxide cycloaddition into bis-epoxide, resulting in a precursor bis(cyclic carbonate)-polydimethylsiloxane (CCPDMS), thus fully replacing isocyanate in the manufacture process. A biomimetic approach was chosen with the molecular composition being inspired by terminal peptides present in adhesive proteins of mussels, like Mefp (Mytilus edulis foot protein), which bear catechol moieties and are strong adhesives even under natural and saline water. The catechol terminal groups were grafted by aminolysis reaction into a polydimethylsiloxane backbone. The product, PDMSUr-Dopamine, presented high affinity towards inhomogeneous alloy surfaces terminated by native oxide layers as demonstrated by quartz crystal microbalance (QCM-D), as well as stability against desorption by rinsing with ethanol. As revealed by QCM-D, X-ray photoelectron spectroscopy (XPS) and computational studies, the thickness and composition of the resulting nanolayers indicated an attachment of PDMSUr-Dopamine molecules to the substrate through both terminal catechol groups, with the adsorbate exposing the hydrophobic PDMS backbone. This hypothesis was investigated by classical molecular dynamic simulation (MD) of pure PDMSUr-Dopamine molecules on SiO2 surfaces. The computationally obtained PDMSUr-Dopamine assembly is in agreement with the conclusions from the experiments regarding the conformation of PDMSUr-Dopamine towards the surface. The tendency of the terminal catechol groups to approach the surface is in agreement with proposed model for the attachment PDMSUr-Dopamine. Remarkably, the versatile

  5. The aqueous chemistry of oxides

    CERN Document Server

    Bunker, Bruce C

    2016-01-01

    The Aqueous Chemistry of Oxides is a comprehensive reference volume and special topics textbook that explores all of the major chemical reactions that take place between oxides and aqueous solutions. The book highlights the enormous impact that oxide-water reactions have in advanced technologies, materials science, geochemistry, and environmental science.

  6. (VI) oxide in acetic acid

    African Journals Online (AJOL)

    The oxidation of cyclohexene by chromium (VI) oxide in aqueous and acetic media was studied. The reaction products were analysed using infra red (IR) and gas chromatography coupled with mass (GC/MS) spectroscopy. The major products of the oxidation reaction in acetic acid medium were cyclohexanol, ...

  7. Model catalytic oxidation studies using supported monometallic and heterobimetallic oxides

    Energy Technology Data Exchange (ETDEWEB)

    Ekerdt, J.G.

    1992-02-03

    This research program is directed toward a more fundamental understanding of the effects of catalyst composition and structure on the catalytic properties of metal oxides. Metal oxide catalysts play an important role in many reactions bearing on the chemical aspects of energy processes. Metal oxides are the catalysts for water-gas shift reactions, methanol and higher alcohol synthesis, isosynthesis, selective catalytic reduction of nitric oxides, and oxidation of hydrocarbons. A key limitation to developing insight into how oxides function in catalytic reactions is in not having precise information of the surface composition under reaction conditions. To address this problem we have prepared oxide systems that can be used to study cation-cation effects and the role of bridging (-O-) and/or terminal (=O) surface oxygen anion ligands in a systematic fashion. Since many oxide catalyst systems involve mixtures of oxides, we selected a model system that would permit us to examine the role of each cation separately and in pairwise combinations. Organometallic molybdenum and tungsten complexes were proposed for use, to prepare model systems consisting of isolated monomeric cations, isolated monometallic dimers and isolated bimetallic dimers supported on silica and alumina. The monometallic and bimetallic dimers were to be used as models of more complex mixed- oxide catalysts. Our current program was to develop the systems and use them in model oxidation reactions.

  8. Aerobic Oxidations of Light Alkanes over Solid Metal Oxide Catalysts.

    Science.gov (United States)

    Grant, Joseph T; Venegas, Juan M; McDermott, William P; Hermans, Ive

    2017-11-07

    Heterogeneous metal oxide catalysts are widely studied for the aerobic oxidations of C 1 -C 4 alkanes to form olefins and oxygenates. In this review, we outline the properties of supported metal oxides, mixed-metal oxides, and zeolites and detail their most common applications as catalysts for partial oxidations of light alkanes. By doing this we establish similarities between different classes of metal oxides and identify common themes in reaction mechanisms and research strategies for catalyst improvement. For example, almost all partial alkane oxidations, regardless of the metal oxide, follow Mars-van Krevelen reaction kinetics, which utilize lattice oxygen atoms to reoxidize the reduced metal centers while the gaseous O 2 reactant replenishes these lattice oxygen vacancies. Many of the most-promising metal oxide catalysts include V 5+ surface species as a necessary constituent to convert the alkane. Transformations involving sequential oxidation steps (i.e., propane to acrylic acid) require specific reaction sites for each oxidation step and benefit from site isolation provided by spectator species. These themes, and others, are discussed in the text.

  9. Chaperones, but not oxidized proteins, are ubiquitinated after oxidative stress

    DEFF Research Database (Denmark)

    Kästle, Marc; Reeg, Sandra; Rogowska-Wrzesinska, Adelina

    2012-01-01

    After oxidative stress proteins which are oxidatively modified are degraded by the 20S proteasome. However, several studies documented an enhanced ubiquitination of yet unknown proteins. Since ubiqutination is a prerequisite for degradation by the 26S proteasome in an ATP-dependent manner...... this raises the question whether these proteins are also oxidized and, if not, what proteins need to be ubiquitinated and degraded after oxidative conditions. By determination of oxidized- and ubiquitinated proteins we demonstrate here that most oxidized proteins are not preferentially ubiquitinated. However......, we were able to confirm an increase of ubiquitinated proteins 16h upon oxidative stress. Therefore, we isolated ubiquitinated proteins from hydrogen peroxide treated cells, as well as from control and lactacystin, an irreversible proteasome inhibitor, treated cells, and identified some...

  10. Iron oxide surfaces

    Science.gov (United States)

    Parkinson, Gareth S.

    2016-03-01

    The current status of knowledge regarding the surfaces of the iron oxides, magnetite (Fe3O4), maghemite (γ-Fe2O3), haematite (α-Fe2O3), and wüstite (Fe1-xO) is reviewed. The paper starts with a summary of applications where iron oxide surfaces play a major role, including corrosion, catalysis, spintronics, magnetic nanoparticles (MNPs), biomedicine, photoelectrochemical water splitting and groundwater remediation. The bulk structure and properties are then briefly presented; each compound is based on a close-packed anion lattice, with a different distribution and oxidation state of the Fe cations in interstitial sites. The bulk defect chemistry is dominated by cation vacancies and interstitials (not oxygen vacancies) and this provides the context to understand iron oxide surfaces, which represent the front line in reduction and oxidation processes. Fe diffuses in and out from the bulk in response to the O2 chemical potential, forming sometimes complex intermediate phases at the surface. For example, α-Fe2O3 adopts Fe3O4-like surfaces in reducing conditions, and Fe3O4 adopts Fe1-xO-like structures in further reducing conditions still. It is argued that known bulk defect structures are an excellent starting point in building models for iron oxide surfaces. The atomic-scale structure of the low-index surfaces of iron oxides is the major focus of this review. Fe3O4 is the most studied iron oxide in surface science, primarily because its stability range corresponds nicely to the ultra-high vacuum environment. It is also an electrical conductor, which makes it straightforward to study with the most commonly used surface science methods such as photoemission spectroscopies (XPS, UPS) and scanning tunneling microscopy (STM). The impact of the surfaces on the measurement of bulk properties such as magnetism, the Verwey transition and the (predicted) half-metallicity is discussed. The best understood iron oxide surface at present is probably Fe3O4(100); the structure is

  11. A 26-Membered Macrocycle Obtained by a Double Diels-Alder Cycloaddition Between Two 2H-Pyran-2-one Rings and Two 1,1'-(Hexane-1,6-diyl)bis (1H-pyrrole-2,5-dione)s.

    Science.gov (United States)

    Turek, Bor Lucijan; Kočevar, Marijan; Kranjc, Krištof; Perdih, Franc

    2017-12-01

    With the application of a double dienophile 1,1'-(hexane-1,6-diyl)bis(1H-pyrrole-2,5-dione) for a [4+2] cycloaddition with a substituted 2H-pyran-2-one a novel 26-membered tetraaza heteromacrocyclic system 3 was prepared via a direct method under solvent-free conditions with microwave irradiation. The macrocycle prepared is composed of two units of the dienophile and two of the diene. The structure of the macrocycle was characterized on the basis of IR, 1H and 13C NMR and mass spectroscopy, as well as by the elemental analysis and melting point determination. With X-ray diffraction of a single crystal of the macrocycle we have determined that the two acetyl groups (attached to the bridging double bond of the bicyclo[2.2.2]octene fragments) are oriented towards each other (and also towards the inside of the cavity of the macrocycle), therefore, mostly filling it completely.

  12. Electrorheology of graphene oxide.

    Science.gov (United States)

    Zhang, Wen Ling; Liu, Ying Dan; Choi, Hyoung Jin; Kim, Sang Guk

    2012-04-01

    Novel polarizable graphene oxide (GO) particles with oxidized groups on their edge and basal planes were prepared by a modified Hummers method, and their electro-responsive electrorheological (ER) characteristics when dispersed in silicone oil were examined with and without an electric field applied. The fibrillation phenomenon of this GO-based electro-responsive fluid was also observed via an optical microscope under an applied electric field. Both flow curves and dielectric spectra of the ER fluid were measured using a rotational rheometer and a LCR meter, respectively. Its viscoelastic properties of both storage and loss moduli were also examined using a vertical oscillation rheometer equipped with a high voltage generator, finding that the GO-based smart ER system behaves as a viscoelastic material under an applied electric field.

  13. Thin Solid Oxide Cell

    DEFF Research Database (Denmark)

    2010-01-01

    The present invention relates to a thin and in principle unsupported solid oxide cell, comprising at least a porous anode layer, an electrolyte layer and a porous cathode layer, wherein the anode layer and the cathode layer comprise an electrolyte material, at least one metal and a catalyst...... material, and wherein the overall thickness of the thin reversible cell is about 150 [mu]m or less, and to a method for producing same. The present invention also relates to a thin and in principle unsupported solid oxide cell, comprising at least a porous anode layer, an electrolyte layer and a porous...... cathode layer, wherein the anode layer and the cathode layer comprise an electrolyte material and a catalyst material, wherein the electrolyte material is doper zirconia, and wherein the overall thickness of the thin reversible cell is about 150 [mu]m or less, and to a method for producing same...

  14. Defects at oxide surfaces

    CERN Document Server

    Thornton, Geoff

    2015-01-01

    This book presents the basics and characterization of defects at oxide surfaces. It provides a state-of-the-art review of the field, containing information to the various types of surface defects, describes analytical methods to study defects, their chemical activity and the catalytic reactivity of oxides. Numerical simulations of defective structures complete the picture developed. Defects on planar surfaces form the focus of much of the book, although the investigation of powder samples also form an important part. The experimental study of planar surfaces opens the possibility of applying the large armoury of techniques that have been developed over the last half-century to study surfaces in ultra-high vacuum. This enables the acquisition of atomic level data under well-controlled conditions, providing a stringent test of theoretical methods. The latter can then be more reliably applied to systems such as nanoparticles for which accurate methods of characterization of structure and electronic properties ha...

  15. Deactivation of Oxidation Catalysts

    Science.gov (United States)

    1991-05-01

    been observed to decrease CO oxidation even at 500TC ( Farrauto and Wedding, 1973, p. 254) by a sulfate formation mechanism, it is likely that the...sulfated CoO, in the study of Farrauto and Wedding (1973) and that no deactivation was observed in the previously discussed study by Pope et al...This is attributed to the adsorption of HO on the catalyst surface which competes with the adsorption of ethanol. Farrauto and Wedding (1973) studied

  16. Radiolytic graphite oxidation revisited

    International Nuclear Information System (INIS)

    Minshall, P.C.; Sadler, I.A.; Wickham, A.J.

    1996-01-01

    The importance of radiolytic oxidation in graphite-moderated CO 2 -cooled reactors has long been recognised, especially in the Advanced Gas-Cooled Reactors where potential rates are higher because of the higher gas pressure and ratings than the earlier Magnox designs. In all such reactors, the rate of oxidation is partly inhibited by the CO produced in the reaction and, in the AGR, further reduced by the deliberate addition of CH 4 . Significant roles are also played by H 2 and H 2 O. This paper reviews briefly the mechanisms of these processes and the data on which they are based. However, operational experience has demonstrated that these basic principles are unsatisfactory in a number of respects. Gilsocarbon graphites produced by different manufacturers have demonstrated a significant difference in oxidation rate despite a similar specification and apparent equivalence in their pore size and distribution, considered to be the dominant influence on oxidation rate for a given coolant-gas composition. Separately, the inhibiting influence of CH 4 , which for many years had been considered to arise from the formation of a sacrificial deposit on the pore walls, cannot adequately be explained by the actual quantities of such deposits found in monitoring samples which frequently contain far less deposited carbon than do samples from Magnox reactors where the only source of such deposits is the CO. The paper also describes the current status of moderator weight-loss predictions for Magnox and AGR Moderators and the validation of the POGO and DIFFUSE6 codes respectively. 2 refs, 5 figs

  17. Nitrous Oxide Explosive Hazards

    Science.gov (United States)

    2008-05-01

    JC, Departement d’anesthesie- reanimation, CHU Angers, 49033 cedex 01, Angers, France , Ann Fr Anesth Reanim, pp 366-8, April 22, 2003. 8. “Some...Krisjansons, Doren E. Bollinger , and Rudolph Edse, ARL 62-431. September 1962. 21. “Detonability of Nitrous Oxide at Elevated Initial Pressures and...Temperatures”, James A Laughrey, Loren E. Bollinger , Rudolph Edse, ARL 62-432, September 1962. 22. “Investigation of Decomposition Characteristics

  18. Oxidative stability of polyaniline

    Czech Academy of Sciences Publication Activity Database

    Stejskal, Jaroslav; Exnerová, Milena; Morávková, Zuzana; Trchová, Miroslava; Hromádková, Jiřina; Prokeš, J.

    2012-01-01

    Roč. 97, č. 6 (2012), s. 1026-1033 ISSN 0141-3910 R&D Projects: GA ČR GA202/09/1626; GA ČR GAP205/12/0911 Institutional research plan: CEZ:AV0Z40500505 Institutional support: RVO:61389013 Keywords : polyaniline * nanotubes * oxidation stability Subject RIV: BK - Fluid Dynamics Impact factor: 2.770, year: 2012

  19. Molecular theory of graphene oxide.

    Science.gov (United States)

    Sheka, Elena F; Popova, Nadezhda A

    2013-08-28

    Applied to graphene oxide, the molecular theory of graphene considers its oxide as a final product in the succession of polyderivatives related to a series of oxidation reactions involving different oxidants. The graphene oxide structure is created in the course of a stepwise computational synthesis of polyoxides of the (5,5) nanographene molecule governed by an algorithm that takes into account the molecule's natural radicalization due to the correlation of its odd electrons, the extremely strong influence of the structure on properties, and a sharp response of the molecule behavior on small actions of external factors. Taking these together, the theory has allowed for a clear, transparent and understandable explanation of the hot points of graphene oxide chemistry and suggesting reliable models of both chemically produced and chemically reduced graphene oxides.

  20. Alkane oxidation by osmium tetroxide.

    Science.gov (United States)

    Bales, Brian C; Brown, Peter; Dehestani, Ahmad; Mayer, James M

    2005-03-09

    Aqueous alkaline OsO4 at 85 degrees C oxidizes saturated alkanes, including primary, secondary, and tertiary C-H bonds. Isobutane affords tert-butanol in quantitative yield based on consumed OsO4. Cyclohexane is oxidized to a mixture of adipate and succinate. Ethane and propane are oxidized to acetate, which itself is further oxidized under the reaction conditions. A few turnovers of isobutane oxidation have been accomplished using NaIO4 as the terminal oxidant. The alkane oxidation is an example of ligand accelerated catalysis, as hydroxide binding to OsO4 is required for reaction. A concerted mechanism involving [3+2] addition of a C-H bond to two oxo groups of OsO4(OH)- is suggested, analogous to the pathways for dihydroxylation of alkenes by OsO4(L) and for addition of H2 to OsO4(L).