WorldWideScience

Sample records for alkenes

  1. Intermolecular Hydropyridylation of Unactivated Alkenes.

    Science.gov (United States)

    Ma, Xiaoshen; Herzon, Seth B

    2016-07-20

    A general method for the hydropyridylation of unactivated alkenes is described. The transformation connects metal-mediated hydrogen atom transfer to alkenes and Minisci addition reactions. The reaction proceeds under mild conditions with high site-selectivities and allows for the construction of tertiary and quaternary centers from simple alkene starting materials. PMID:27384921

  2. NOx analyser interefence from alkenes

    Science.gov (United States)

    Bloss, W. J.; Alam, M. S.; Lee, J. D.; Vazquez, M.; Munoz, A.; Rodenas, M.

    2012-04-01

    Nitrogen oxides (NO and NO2, collectively NOx) are critical intermediates in atmospheric chemistry. NOx abundance controls the levels of the primary atmospheric oxidants OH, NO3 and O3, and regulates the ozone production which results from the degradation of volatile organic compounds. NOx are also atmospheric pollutants in their own right, and NO2 is commonly included in air quality objectives and regulations. In addition to their role in controlling ozone formation, NOx levels affect the production of other pollutants such as the lachrymator PAN, and the nitrate component of secondary aerosol particles. Consequently, accurate measurement of nitrogen oxides in the atmosphere is of major importance for understanding our atmosphere. The most widely employed approach for the measurement of NOx is chemiluminescent detection of NO2* from the NO + O3 reaction, combined with NO2 reduction by either a heated catalyst or photoconvertor. The reaction between alkenes and ozone is also chemiluminescent; therefore alkenes may contribute to the measured NOx signal, depending upon the instrumental background subtraction cycle employed. This interference has been noted previously, and indeed the effect has been used to measure both alkenes and ozone in the atmosphere. Here we report the results of a systematic investigation of the response of a selection of NOx analysers, ranging from systems used for routine air quality monitoring to atmospheric research instrumentation, to a series of alkenes ranging from ethene to the biogenic monoterpenes, as a function of conditions (co-reactants, humidity). Experiments were performed in the European Photoreactor (EUPHORE) to ensure common calibration, a common sample for the monitors, and to unequivocally confirm the alkene (via FTIR) and NO2 (via DOAS) levels present. The instrument responses ranged from negligible levels up to 10 % depending upon the alkene present and conditions used. Such interferences may be of substantial importance

  3. Chromium Salen Mediated Alkene Epoxidation

    DEFF Research Database (Denmark)

    Petersen, Kaare Brandt; Norrby, Per-Ola; Daly, Adrian M.; Gilheany, Declan G.

    2002-01-01

    The mechanism of alkene epoxidation by chromium(v) oxo salen complexes has been studied by DFT and experimental methods. The reaction is compared to the closely related Mn-catalyzed process in an attempt to understand the dramatic difference in selectivity between the two systems. Overall, the......-spin surface. The low-spin addition of metal oxo species to an alkene leads to an intermediate which forms epoxide either with a barrier on the low-spin surface or without a barrier after spin inversion. Supporting evidence for this intermediate was obtained by using vinylcyclopropane traps. The chromium...

  4. Interaction of iodosofluorosulfate with alkenes

    International Nuclear Information System (INIS)

    For the first time, electrophylic addition reactions of iodosofluorosulfate to some acyclic, mono-, bi- and polycyclic obefins, dienes and trienes were studied. High electrophility of the reagent promoted formation of intermediate carbocations. Their further stabilization was realized by intramolecular participation of ester group of alkenes, either binding of own nuclophile-fluorosulfate-aion, or addition of ternal moleophiles

  5. The arene–alkene photocycloaddition

    Directory of Open Access Journals (Sweden)

    Christian G. Bochet

    2011-04-01

    Full Text Available In the presence of an alkene, three different modes of photocycloaddition with benzene derivatives can occur; the [2 + 2] or ortho, the [3 + 2] or meta, and the [4 + 2] or para photocycloaddition. This short review aims to demonstrate the synthetic power of these photocycloadditions.

  6. Catalytic Enantioselective Functionalization of Unactivated Terminal Alkenes.

    Science.gov (United States)

    Coombs, John R; Morken, James P

    2016-02-01

    Terminal alkenes are readily available functional groups which appear in α-olefins produced by the chemical industry, and they appear in the products of many contemporary synthetic reactions. While the organic transformations that apply to alkenes are amongst the most studied reactions in all of chemical synthesis, the number of reactions that apply to nonactivated terminal alkenes in a catalytic enantioselective fashion is small in number. This Minireview highlights the cases where stereocontrol in catalytic reactions of 1-alkenes is high enough to be useful for asymmetric synthesis. PMID:26764019

  7. Remote functionalization through alkene isomerization

    Science.gov (United States)

    Vasseur, Alexandre; Bruffaerts, Jeffrey; Marek, Ilan

    2016-03-01

    Exploiting the reactivity of one functional group within a molecule to generate a reaction at a different position is an ongoing challenge in organic synthesis. Effective remote functionalization protocols have the potential to provide access to almost any derivatives but are difficult to achieve. The difficulty is more pronounced for acyclic systems where flexible alkyl chains are present between the initiating functional group and the desired reactive centres. In this Review, we discuss the concept of remote functionalization of alkenes using metal complexes, leading to a selective reaction at a position distal to the initial double bond. We aim to show the vast opportunity provided by this growing field through selected and representative examples. Our aim is to demonstrate that using a double bond as a chemical handle, metal-assisted long-distance activation could be used as a powerful synthetic strategy.

  8. Cobalt-Mediated Vinylic C-H Functionalization of Alkenes

    OpenAIRE

    Boyd, Warren Christopher

    2012-01-01

    The reaction of cobalt dinitrosyl complexes with alkenes to form cobalt dinitrosoalkane complexes is used to effect the C-H functionalization of alkenes. Deprotonation of cobalt dinitrosoalkane complexes, followed by reaction with neutral electrophiles, yields functionalized cobalt complexes. Thermolysis of such complexes with the parent alkene allows a migration of the cobalt dinitrosyl moiety to the parent alkene, releasing the organic product of C-H functionalization. Progress is presented...

  9. Heterogeneous Catalysis: The Horiuti-Polanyi Mechanism and Alkene Hydrogenation

    Science.gov (United States)

    Mattson, Bruce; Foster, Wendy; Greimann, Jaclyn; Hoette, Trisha; Le, Nhu; Mirich, Anne; Wankum, Shanna; Cabri, Ann; Reichenbacher, Claire; Schwanke, Erika

    2013-01-01

    The hydrogenation of alkenes by heterogeneous catalysts has been studied for 80 years. The foundational mechanism was proposed by Horiuti and Polanyi in 1934 and consists of three steps: (i) alkene adsorption on the surface of the hydrogenated metal catalyst, (ii) hydrogen migration to the beta-carbon of the alkene with formation of a delta-bond…

  10. Alkene carboboration enabled by synergistic catalysis.

    Science.gov (United States)

    Smith, Kevin B; Logan, Kaitlyn M; You, Wei; Brown, M Kevin

    2014-09-15

    A synergistic Pd/Cu system for the coupling of alkenes, (Bpin)2 (pin = pinacolate), and aryl/vinyl bromides is disclosed. This method allows for the catalytic generation of secondary Csp(3)-Cu nucleophiles in situ and subsequent Pd-catalyzed cross-coupling. PMID:25113669

  11. [C. E. Alken (1909-1986) and the Alken-Prize].

    Science.gov (United States)

    Konert, J

    2016-06-01

    C. E. Alken is regarded as the Nestor of German urology post World War II. His development path is given in brief and his specific contributions to the emancipation of the field are pointed out. In 1948 he received a teaching assignment in urology at Saarland State University Homburg, where in 1952, a Chair of Urology was established, and in 1958 he received the Ordinariat. The "Alken-Prize" which was named after him, is also presented. PMID:27160773

  12. Naturally Produced Defensive Alkenal Compounds Activate TRPA1.

    Science.gov (United States)

    Blair, Nathaniel T; Philipson, Benjamin I; Richards, Paige M; Doerner, Julia F; Segura, Abraham; Silver, Wayne L; Clapham, David E

    2016-05-01

    (E)-2-alkenals are aldehydes containing an unsaturated bond between the alpha and beta carbons. 2-alkenals are produced by many organisms for defense against predators and secretions containing (E)-2-alkenals cause predators to stop attacking and allow the prey to escape. Chemical ecologists have described many alkenal compounds with 3-20 carbons common, having varied positions of double bonds and substitutions. How do these defensive alkenals act to deter predators? We have tested the effects of (E)-2-alkenals with 6-12 carbons on transient receptor potential channels (TRP) commonly found in sensory neurons. We find that (E)-2-alkenals activate transient receptor potential ankyrin subtype 1 (TRPA1) at low concentrations-EC50s 10-100 µM (in 0 added Ca(2+) external solutions). Other TRP channels were either weakly activated (TRPV1, TRPV3) or insensitive (TRPV2, TRPV4, TRPM8). (E)-2-alkenals may activate TRPA1 by modifying cysteine side chains. However, target cysteines include others beyond the 3 in the amino-terminus implicated in activation, as a channel with cysteines at 621, 641, 665 mutated to serine responded robustly. Related chemicals, including the aldehydes hexanal and decanal, and (E)-2-hexen-1-ol also activated TRPA1, but with weaker potency. Rat trigeminal nerve recordings and behavioral experiments showed (E)-2-hexenal was aversive. Our results suggest that TRPA1 is likely a major target of these commonly used defensive chemicals. PMID:26843529

  13. Synthesis of terminal alkenes from internal alkenes and ethylene via olefin metathesis

    Energy Technology Data Exchange (ETDEWEB)

    Schrodi, Yann

    2016-02-09

    This invention relates generally to olefin metathesis, and more particularly relates to the synthesis of terminal alkenes from internal alkenes using a cross-metathesis reaction catalyzed by a selected olefin metathesis catalyst. In one embodiment of the invention, for example, a method is provided for synthesizing a terminal olefin, the method comprising contacting an olefinic substrate comprised of at least one internal olefin with ethylene, in the presence of a metathesis catalyst, wherein the catalyst is present in an amount that is less than about 1000 ppm relative to the olefinic substrate, and wherein the metathesis catalyst has the structure of formula (II) ##STR00001## wherein the various substituents are as defined herein. The invention has utility, for example, in the fields of catalysis, organic synthesis, and industrial chemistry.

  14. Synthesis of terminal alkenes from internal alkenes and ethylene via olefin metathesis

    Science.gov (United States)

    Schrodi, Yann

    2013-07-09

    This invention relates generally to olefin metathesis, and more particularly relates to the synthesis of terminal alkenes from internal alkenes using a cross-metathesis reaction catalyzed by a selected olefin metathesis catalyst. In one embodiment of the invention, for example, a method is provided for synthesizing a terminal olefin, the method comprising contacting an olefinic substrate comprised of at least one internal olefin with ethylene, in the presence of a metathesis catalyst, wherein the catalyst is present in an amount that is less than about 1000 ppm relative to the olefinic substrate, and wherein the metathesis catalyst has the structure of formula (II) ##STR00001## wherein the various substituents are as defined herein. The invention has utility, for example, in the fields of catalysis, organic synthesis, and industrial chemistry.

  15. Asymmetric Michael Addition of Activated Alkenes to Nitro Alkenes Catalyzed by Organic Catalyst

    Institute of Scientific and Technical Information of China (English)

    XUE Dong; CHEN Yong-Chun; CUI Xin; WANG Qi-Wei; ZHU Jin; DENG Jin-Gen

    2003-01-01

    @@ Enantioselective Michael addition is one of the most powerfulbond-forming reaction in organic synthesis. [1] A mong the Michael acceptors, nitro alkenes are very attractive, because the nitro group is the most electron-withdrawing group known and it can serve as masked functionality to be further transformed after the addition has taken place. [2] Recently, asymmetric Michael reactions catalyzed by organic catalyst have draw much attention.[3

  16. Formation of hydrogen peroxide through ozonolysis of alkenes

    Energy Technology Data Exchange (ETDEWEB)

    Bechara, J.; Becker, K.H. (Wuppertal Univ. (Gesamthochschule) (DE)); Brockmann, K.J.

    1991-07-01

    The gas phase reactions of ozone with several alkenes (including isoprene and some terpenes) are investigated for the formation of hydrogen peroxide (H202) under atmospheric conditions by means of a TDLAS. All alkenes produced hydrogen peroxide with a molar yield in the part per thousand range. Water vapour induced a significant increase (factor 3 to 14) in H202 yield, due to the reaction of water vapour with the Criegee biradical, the main intermediate in alkene ozonolysis. Reaction rate are reported, with respect to sulfur dioxide, for ethene, tetramethylethene and limonene. Forest air application is discussed.

  17. Synthesis of trans-disubstituted alkenes by cobalt-catalyzed reductive coupling of terminal alkynes with activated alkenes.

    Science.gov (United States)

    Mannathan, Subramaniyan; Cheng, Chien-Hong

    2012-09-10

    A cobalt-catalyzed reductive coupling of terminal alkynes, RC≡CH, with activated alkenes, R'CH=CH(2), in the presence of zinc and water to give functionalized trans-disubstituted alkenes, RCH=CHCH(2)CH(2)R', is described. A variety of aromatic terminal alkynes underwent reductive coupling with activated alkenes including enones, acrylates, acrylonitrile, and vinyl sulfones in the presence of a CoCl(2)/P(OMe)(3)/Zn catalyst system to afford 1,2-trans-disubstituted alkenes with high regio- and stereoselectivity. Similarly, aliphatic terminal alkynes also efficiently participated in the coupling reaction with acrylates, enones, and vinyl sulfone, in the presence of the CoCl(2)/P(OPh)(3)/Zn system providing a mixture of 1,2-trans- and 1,1-disubstituted functionalized terminal alkene products in high yields. The scope of the reaction was also extended by the coupling of 1,3-enynes and acetylene gas with alkenes. Furthermore, a phosphine-free cobalt-catalyzed reductive coupling of terminal alkynes with enones, affording 1,2-trans-disubstituted alkenes as the major products in a high regioisomeric ratio, is demonstrated. In the reactions, less expensive and air-stable cobalt complexes, a mild reducing agent (Zn) and a simple hydrogen source (water) were used. A possible reaction mechanism involving a cobaltacyclopentene as the key intermediate is proposed. PMID:22865622

  18. Reactions of strained hydrocarbons with alkene and alkyne metathesis catalysts.

    Science.gov (United States)

    Carnes, Matthew; Buccella, Daniela; Siegrist, Theo; Steigerwald, Michael L; Nuckolls, Colin

    2008-10-29

    Here we describe the metathesis reactions of a strained eight-membered ring that contains both alkene and alkyne functionality. We find that the alkyne metathesis catalyst produces polymer through a ring-opening alkyne metathesis reaction that is driven by the strain release from the monomer. The strained monomer provides unusual reactivity with ruthenium-based alkene metathesis catalysts. We isolate a discrete trimeric species a Dewar benzene derivative that is locked in this form through an unsaturated cyclophane strap. PMID:18826219

  19. Metal carbenes in homogeneous alkene metathesis: computational investigations

    OpenAIRE

    du Toit, J I; Van Sittert, C.G.C.E.; H. C. M. Vosloo

    2013-01-01

    This paper demonstrates the contribution of molecular modeling as a tool to understanding alkene metathesis e by giving an overview of computational studies done of the four main types of metal carbenes tested in homogeneous alkene metathesis as catalysts after the discovery of the Chauvin mechanism. Three areas were discussed, namely: properties of transition metal complexes, the theoretical treatment of the four main types of metal carbenes and the computational studies done on ...

  20. Combinatorial metabolic engineering of Saccharomyces cerevisiae for terminal alkene production.

    Science.gov (United States)

    Chen, Binbin; Lee, Dong-Yup; Chang, Matthew Wook

    2015-09-01

    Biological production of terminal alkenes has garnered a significant interest due to their industrial applications such as lubricants, detergents and fuels. Here, we engineered the yeast Saccharomyces cerevisiae to produce terminal alkenes via a one-step fatty acid decarboxylation pathway and improved the alkene production using combinatorial engineering strategies. In brief, we first characterized eight fatty acid decarboxylases to enable and enhance alkene production. We then increased the production titer 7-fold by improving the availability of the precursor fatty acids. We additionally increased the titer about 5-fold through genetic cofactor engineering and gene expression tuning in rich medium. Lastly, we further improved the titer 1.8-fold to 3.7 mg/L by optimizing the culturing conditions in bioreactors. This study represents the first report of terminal alkene biosynthesis in S. cerevisiae, and the abovementioned combinatorial engineering approaches collectively increased the titer 67.4-fold. We envision that these approaches could provide insights into devising engineering strategies to improve the production of fatty acid-derived biochemicals in S. cerevisiae. PMID:26164646

  1. Intramolecular Alkene Aminocarbonylation Using Concerted Cycloadditions of Amino-Isocyanates.

    Science.gov (United States)

    Ivanovich, Ryan A; Clavette, Christian; Vincent-Rocan, Jean-François; Roveda, Jean-Grégoire; Gorelsky, Serge I; Beauchemin, André M

    2016-06-01

    The ubiquity of nitrogen heterocycles in biologically active molecules challenges synthetic chemists to develop a variety of tools for their construction. While developing metal-free hydroamination reactions of hydrazine derivatives, it was discovered that carbazates and semicarbazides can also lead to alkene aminocarbonylation products if nitrogen-substituted isocyanates (N-isocyanates) are formed in situ as reactive intermediates. At first this reaction required high temperatures (150-200 °C), and issues included competing hydroamination and N-isocyanate dimerization pathways. Herein, improved conditions for concerted intramolecular alkene aminocarbonylation with N-isocyanates are reported. The use of βN-benzyl carbazate precursors allows the effective minimization of N-isocyanate dimerization. Diminished dimerization leads to higher yields of alkene aminocarbonylation products, to reactivity at lower temperatures, and to an improved scope for a reaction sequence involving alkene aminocarbonylation followed by 1,2-migration of the benzyl group. Furthermore, fine-tuning of the blocking (masking) group on the N-isocyanate precursor, and reaction conditions relying on base catalysis for N-isocyanate formation from simpler precursors resulted in room temperature reactivity, consequently minimizing the competing hydroamination pathway. Collectively, this work highlights that controlled reactivity of aminoisocyanates is possible, and provides a broadly applicable alkene aminocarbonylation approach to heterocycles possessing the β-aminocarbonyl motif. PMID:27112602

  2. Biogenic Emissions of Light Alkenes from a Coniferous Forest

    Science.gov (United States)

    Rhew, R. C.; Turnipseed, A. A.; Martinez, L.; Shen, S.; De Gouw, J. A.; Warneke, C.; Koss, A.; Lerner, B. M.; Miller, B. R.; Smith, J. N.; Guenther, A. B.

    2014-12-01

    Alkenes are reactive hydrocarbons that play important roles in the photochemical production of tropospheric ozone and in the formation of secondary organic aerosols. The light alkenes (C2-C4) originate from both biogenic and anthropogenic sources and include C2H4 (ethene), C3H6 (propene) and C4H8 (1-butene, 2-butene, 2-methylpropene). Light alkenes are used widely as chemical feedstocks because their double bond makes them versatile for industrial reactions. Their biogenic sources are poorly characterized, with most global emissions estimates relying on laboratory-based studies; net ecosystem emissions have been measured at only one site thus far. Here we report net ecosystem fluxes of light alkenes and isoprene from a semi-arid ponderosa pine forest in the Rocky Mountains of Colorado, USA. Canopy scale fluxes were measured using relaxed eddy accumulation (REA) techniques on the 28-meter NCAR tower in the Manitou Experimental Forest Observatory. Updrafts and downdrafts were determined by sonic anemometry and segregated into 'up' and 'down' reservoirs over the course of an hour. Samples were then measured on two separate automated gas chromatographs (GCs). The first GC measured light hydrocarbons (C2-C6 alkanes and C2-C5 alkenes) by flame ionization detection (FID). The second GC measured halocarbons (methyl chloride, CFC-12, and HCFC-22) by electron capture detection (ECD). Additional air measurements from the top of the tower included hydrocarbons and their oxidation products by Proton Transfer Reaction Mass Spectrometry (PTR-MS). Three field intensives were conducted during the summer of 2014. The REA flux measurements showed that ethene, propene and the butene emissions have significant diurnal cycles, with maximum emissions at midday. The light alkenes contribute significantly to the overall biogenic source of reactive hydrocarbons and have a temporal variability that may be associated with physical and biological parameters. These ecosystem scale measurements

  3. Heuristical Strategies on the Study Theme "The Unsaturated Hydrocarbons -- Alkenes"

    Science.gov (United States)

    Naumescu, Adrienne Kozan; Pasca, Roxana-Diana

    2011-01-01

    The influence of heuristical strategies upon the level of two experimental classes is studied in this paper. The didactic experiment took place at secondary school in Cluj-Napoca, in 2008-2009 school year. The study theme "The Unsaturated Hydrocarbons--Alkenes" has been efficiently learned by using the most active methods: laboratory…

  4. Mechanistic approaches to palladium-catalyzed alkene difunctionalization reactions

    OpenAIRE

    Jensen, Katrina H.; Sigman, Matthew S.

    2008-01-01

    Alkene difunctionalization, the addition of two functional groups across a double bond, exemplifies a class of reactions with significant synthetic potential. This emerging area examines recent developments of palladium-catalyzed difunctionalization reactions, with a focus on mechanistic strategies that allow for functionalization of a common palladium alkyl intermediate.

  5. Structure-Odor Relationships of (E)-3-Alkenoic Acids, (E)-3-Alken-1-ols, and (E)-3-Alkenals.

    Science.gov (United States)

    Lorber, Katja; Buettner, Andrea

    2015-08-01

    (E)-3-Unsaturated volatile acids, alcohols, and aldehydes are commonly found as odorants or pheromones in foods and other natural sources, playing a vital role in not only the attractiveness of foods but also chemo-communication in the animal kingdom. However, a systematic elucidation of their aroma properties, especially for humans, has not been carried out until today. To close this gap, the odor thresholds in air and odor qualities of homologous series of (E)-3-alkenoic acids, (E)-3-alken-1-ols, and (E)-3-alkenals were determined by gas chromatography-olfactometry. In the series of (E)-3-alkenoic acids the odor quality changed successively from sweaty via plastic-like to sweaty and waxy. On the other hand, the odor qualities in the series of (E)-3-alken-1-ols and (E)-3-alkenals changed from grassy, green to an overall citrus-like, fresh, soapy, and coriander-like odor with increasing chain length. With regard to their odor potencies, the lowest thresholds in air were found for (E)-3-heptenoic acid, (E)-3-hexenoic acid, and (E)-3-hexenal. PMID:26165743

  6. Direct C–H trifluoromethylation of di- and trisubstituted alkenes by photoredox catalysis

    Directory of Open Access Journals (Sweden)

    Ren Tomita

    2014-05-01

    Full Text Available Background: Trifluoromethylated alkene scaffolds are known as useful structural motifs in pharmaceuticals and agrochemicals as well as functional organic materials. But reported synthetic methods usually require multiple synthetic steps and/or exhibit limitation with respect to access to tri- and tetrasubstituted CF3-alkenes. Thus development of new methodologies for facile construction of Calkenyl–CF3 bonds is highly demanded.Results: The photoredox reaction of alkenes with 5-(trifluoromethyldibenzo[b,d]thiophenium tetrafluoroborate, Umemoto’s reagent, as a CF3 source in the presence of [Ru(bpy3]2+ catalyst (bpy = 2,2’-bipyridine under visible light irradiation without any additive afforded CF3-substituted alkenes via direct Calkenyl–H trifluoromethylation. 1,1-Di- and trisubstituted alkenes were applicable to this photocatalytic system, providing the corresponding multisubstituted CF3-alkenes. In addition, use of an excess amount of the CF3 source induced double C–H trifluoromethylation to afford geminal bis(trifluoromethylalkenes.Conclusion: A range of multisubstituted CF3-alkenes are easily accessible by photoredox-catalyzed direct C–H trifluoromethylation of alkenes under mild reaction conditions. In particular, trifluoromethylation of triphenylethene derivatives, from which synthetically valuable tetrasubstituted CF3-alkenes are obtained, have never been reported so far. Remarkably, the present facile and straightforward protocol is extended to double trifluoromethylation of alkenes.

  7. Electrocatalytic aerobic epoxidation of alkenes: Experimental and DFT investigation

    International Nuclear Information System (INIS)

    A new method for electrocatalytic aerobic epoxidation of alkenes catalyzed by binuclear Cu(II) complexes with azomethine ligands based on 2,6-diformyl-4-tert-butylphenol is described. In acetonitrile–water (5%), at the potential of CuII/CuI redox couple (–0.8 V vs. Ag/AgCl/KCl) at room temperature the epoxide is obtained in an average yield of around 50%. Contrary to the majority of known epoxidations, no strong oxidants are involved and no free hydrogen peroxide is formed in the reaction, thus making it ecologically friendly. The DFT quantum-chemical modeling of the reaction mechanism revealed that a copper hydroperoxo-complex rather than hydrogen peroxide or a copper oxo-complex oxidizes alkene. The process is very selective since neither products of hydroxylation of benzene ring in styrene nor of allylic oxidation of cyclohexene were detected.

  8. Cl atom initiated oxidation of 1-alkenes under atmospheric conditions

    Science.gov (United States)

    Walavalkar, M.; Sharma, A.; Alwe, H. D.; Pushpa, K. K.; Dhanya, S.; Naik, P. D.; Bajaj, P. N.

    2013-03-01

    In view of the importance of the oxidation pathways of alkenes in the troposphere, and the significance of Cl atom as an oxidant in marine boundary layer (MBL) and polluted industrial atmosphere, the reactions of four 1-alkenes (C6-C9) with Cl atoms are investigated. The rate coefficients at 298 K are measured to be (4.0 ± 0.5), (4.4 ± 0.7), (5.5 ± 0.9) and (5.9 ± 1.7) × 10-10 cm3 molecule-1 s-1 for 1-hexene, 1-heptene, 1-octene and 1-nonene, respectively. The quoted errors include the experimental 2σ, along with the error in the reference rate coefficients. From the systematic increase in the rate coefficients with the number of carbon atoms, an approximate value for the average rate coefficient for hydrogen abstraction per CH2 group in alkenes is estimated to be (4.9 ± 0.3) × 10-11 cm3 molecule-1 s-1. Based on these rate coefficients, the contribution of Cl atom reactions towards the degradation of these molecules is found to be comparable to that of OH radical reactions, under MBL conditions. The products identified in gas phase indicate that Cl atom addition occurs mainly at the terminal carbon, leading to the formation of 1-chloro-2-ketones and 1-chloro-2-ols. The major gas phase products from the alkenyl radicals (formed by H atom abstraction) are different positional isomers of long chain enols and enones. A preference for dissociation leading to an allyl radical, resulting in aldehydes, lower by three carbon atoms, is indicated. The observed relative yields suggest that in general, the increased contribution of the reactions of Cl atoms towards degradation of 1-alkenes in NOx free air does not result in an increase in the generation of small aldehydes (carbon number < 4), including chloroethanal, as compared to that in the reaction of 1-butene.

  9. Cp2TiCl2-Catalyzed Regioselective Hydrocarboxylation of Alkenes with CO2.

    Science.gov (United States)

    Shao, Peng; Wang, Sheng; Chen, Chao; Xi, Chanjuan

    2016-05-01

    Cp2TiCl2-catalyzed regioselective hydrocarboxylation of alkenes with CO2 to give carboxylic acids in high yields has been developed in the presence of (i)PrMgCl. The reaction proceeds with a wide range of alkenes under mild conditions. Styrene and its derivatives can transform to α-aryl carboxylic acids, and aliphatic alkenes can transform to form alkanoic acids. PMID:27097225

  10. 40 CFR 721.4464 - Mixture of hydrofluoro alkanes and hydrofluoro alkene.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Mixture of hydrofluoro alkanes and... Specific Chemical Substances § 721.4464 Mixture of hydrofluoro alkanes and hydrofluoro alkene. (a) Chemical... as a mixture of hydrofluoro alkanes and hydrofluoro alkene (PMNs P-96-945/946/947/948) are subject...

  11. Regioselective Wacker Oxidation of Internal Alkenes: Rapid Access to Functionalized Ketones Facilitated by Cross-Metathesis

    KAUST Repository

    Morandi, Bill

    2013-07-26

    Wacka wacka: The title reaction makes use of a wide range of directing groups (DG) to enable the highly regioselective oxidation of alkenes, and occurs predictably at the distal position. Both E and Z alkenes afford valuable functionalized ketones and cross-metathesis was shown to facilitate the preparation of the starting materials. BQ=benzoquinone.

  12. Metallocene-catalyzed alkene polymerization and the observation of Zr-allyls

    OpenAIRE

    Landis, Clark R.; Christianson, Matthew D.

    2006-01-01

    Single-site polymerization catalysts enable exquisite control over alkene polymerization reactions to produce new materials with unique properties. Knowledge of catalyst speciation and fundamental kinetics are essential for full mechanistic understanding of zirconocene-catalyzed alkene polymerization. Currently the effect of activators on fundamental polymerization steps is not understood. Progress in understanding activator effects requires determination of fundamental kinetics for zirconoce...

  13. Reactions of functionalized alkenes with sulfur trioxide; mechanistic and synthetic aspects. Doctoral thesis

    Energy Technology Data Exchange (ETDEWEB)

    Schonk, R.M.

    1993-01-07

    In the thesis mechanistic studies on the sulfonation of mono-functionalized alkenes, viz. phenylalkenes, naphthylalkenes, alkenoic acids, alkadienes and cycloalkylidenes, mainly with sulfur trioxide are described. The main objective of the studies is to determine the effect of the substituents at the alkene moiety on the formation of the beta-sultones and carbyl sulfates and on their chemistry.

  14. Chiral diamine-silver(I)-alkene complexes: a quantum chemical and NMR study

    DEFF Research Database (Denmark)

    Kieken, Elsa; Wiest, Olaf; Helquist, Paul; Cucciolito, Maria E.; Flores, Germana; Vitagliano, Aldo; Norrby, Per-Ola

    2005-01-01

    The ability of chiral diamine silver complexes to bind chiral and prochiral alkenes has been analyzed in detail. The stereoselectivity in binding of alkenes to a chiral ethanediamine silver complex has been investigated by NMR. The low-energy conformations of several small model complexes have be...

  15. Enantioselective Intramolecular Hydroarylation of Alkenes via Directed C-H Bond Activation

    Energy Technology Data Exchange (ETDEWEB)

    Harada, Hitoshi; Thalji, Reema; Bergman, Robert; Ellman, Jonathan

    2008-05-22

    Highly enantioselective catalytic intramolecular ortho-alkylation of aromatic imines containing alkenyl groups tethered at the meta position relative to the imine directing group has been achieved using [RhCl(coe){sub 2}]{sub 2} and chiral phosphoramidite ligands. Cyclization of substrates containing 1,1- and 1,2-disubstituted as well as trisubstituted alkenes were achieved with enantioselectivities >90% ee for each substrate class. Cyclization of substrates with Z-alkene isomers proceeded much more efficiently than substrates with E-alkene isomers. This further enabled the highly stereoselective intramolecular alkylation of certain substrates containing Z/E-alkene mixtures via a Rh-catalyzed alkene isomerization with preferential cyclization of the Z-isomer.

  16. Genes involved in long-chain alkene biosynthesis in Micrococcus luteus

    Energy Technology Data Exchange (ETDEWEB)

    Beller, Harry R.; Goh, Ee-Been; Keasling, Jay D.

    2010-01-07

    Aliphatic hydrocarbons are highly appealing targets for advanced cellulosic biofuels, as they are already predominant components of petroleum-based gasoline and diesel fuels. We have studied alkene biosynthesis in Micrococcus luteus ATCC 4698, a close relative of Sarcina lutea (now Kocuria rhizophila), which four decades ago was reported to biosynthesize iso- and anteiso branched, long-chain alkenes. The underlying biochemistry and genetics of alkene biosynthesis were not elucidated in those studies. We show here that heterologous expression of a three-gene cluster from M. luteus (Mlut_13230-13250) in a fatty-acid overproducing E. coli strain resulted in production of long-chain alkenes, predominantly 27:3 and 29:3 (no. carbon atoms: no. C=C bonds). Heterologous expression of Mlut_13230 (oleA) alone produced no long-chain alkenes but unsaturated aliphatic monoketones, predominantly 27:2, and in vitro studies with the purified Mlut_13230 protein and tetradecanoyl-CoA produced the same C27 monoketone. Gas chromatography-time of flight mass spectrometry confirmed the elemental composition of all detected long-chain alkenes and monoketones (putative intermediates of alkene biosynthesis). Negative controls demonstrated that the M. luteus genes were responsible for production of these metabolites. Studies with wild-type M. luteus showed that the transcript copy number of Mlut_13230-13250 and the concentrations of 29:1 alkene isomers (the dominant alkenes produced by this strain) generally corresponded with bacterial population over time. We propose a metabolic pathway for alkene biosynthesis starting with acyl-CoA (or -ACP) thioesters and involving decarboxylative Claisen condensation as a key step, which we believe is catalyzed by OleA. Such activity is consistent with our data and with the homology (including the conserved Cys-His-Asn catalytic triad) of Mlut_13230 (OleA) to FabH (?-ketoacyl-ACP synthase III), which catalyzes decarboxylative Claisen condensation during

  17. New developments in gold-catalyzed manipulation of inactivated alkenes

    Directory of Open Access Journals (Sweden)

    Michel Chiarucci

    2013-11-01

    Full Text Available Over the recent years, the nucleophilic manipulation of inactivated carbon–carbon double bonds has gained remarkable credit in the chemical community. As a matter of fact, despite lower reactivity with respect to alkynyl and allenyl counterparts, chemical functionalization of isolated alkenes, via carbon- as well as hetero atom-based nucleophiles, would provide direct access to theoretically unlimited added value of molecular motifs. In this context, homogenous [Au(I] and [Au(III] catalysis continues to inspire developments within organic synthesis, providing reliable responses to this interrogative, by combining crucial aspects such as chemical selectivity/efficiency with mild reaction parameters. This review intends to summarize the recent progresses in the field, with particular emphasis on mechanistic details.

  18. Ruthenium-catalysed alkoxycarbonylation of alkenes with carbon dioxide.

    Science.gov (United States)

    Wu, Lipeng; Liu, Qiang; Fleischer, Ivana; Jackstell, Ralf; Beller, Matthias

    2014-01-01

    Alkene carbonylations represent a major technology for the production of value-added bulk and fine chemicals. Nowadays, all industrial carbonylation processes make use of highly toxic and flammable carbon monoxide. Here we show the application of abundantly available carbon dioxide as C1 building block for the alkoxycarbonylations of industrially important olefins in the presence of a convenient and inexpensive ruthenium catalyst system. In our system, carbon dioxide works much better than the traditional combination of carbon monoxide and alcohols. The unprecedented in situ formation of carbon monoxide from carbon dioxide and alcohols permits an efficient synthesis of carboxylic acid esters, which can be used as detergents and polymer-building blocks. Notably, this transformation allows the catalytic formation of C-C bonds with carbon dioxide as C1 source and avoids the use of sensitive and/or expensive reducing agents (for example, Grignard reagents, diethylzinc or triethylaluminum). PMID:24518431

  19. Synthesis and dynamic behaviour of new metallo-based sterically overcrowded alkenes

    NARCIS (Netherlands)

    Smid, WI; Schoevaars, AM; Kruizinga, W; Veldman, N; Smeets, WJJ; Spek, AL; Feringa, BL; Smeets, Wilberth J.J.; Spek, Anthony L.; Feringa, Bernard

    1996-01-01

    The synthesis and crystal and molecular structures of novel metallo-based sterically overcrowded alkenes are reported and dynamic H-1 NMR studies reveals that the isomerization barriers are dramatically increased on metal coordination.

  20. A general, norbornyl based approach to anti-Bredt alkenes via sequential RCM-fragmentation strategy

    OpenAIRE

    Mehta, Goverdhan; Kumaran, Senthil R

    2002-01-01

    A general protocol for the synthesis of bicyclo[n.3.1 frameworks with bridgehead double bond (anti-Bredt alkenes), from a common, readily available norbornyl precursor, involving sequential ring closure metathesis (RCM) and Wharton fragmentation is outlined.

  1. Synthetic Studies on Erythromycin Derivatives: Reactivity of the C12-21 Alkene

    Directory of Open Access Journals (Sweden)

    Wei-Min Chen

    2006-01-01

    Full Text Available The reactivity of the C12-21 alkene of some erythromycin A derivatives was studied. This double bond was easily oxidized to the corresponding epoxide with excellent stereoselectivity. A single crystal X-ray structure showed that the epoxide moiety was on the same side as the acetonide. When an erythromycin derivative containing a C12-21 alkene was treated with diazomethane a [3+2] cycloaddition affording a pyrazoline occurred. In the case of 6-O-allylated erythromycin derivatives the C12-21 alkene was selectively epoxidized in the presence of the 6-O-allyl moiety. These results show that the C12-21 alkene is an active reaction site, which can be used for useful further modification of erythromycin derivatives.

  2. On the mechanism of homogeneous alkene metathesis : a computational study / Jean Isabelle du Toit

    OpenAIRE

    Du Toit, Jean Isabelle

    2012-01-01

    A mechanism for alkene metathesis has been proposed by Chauvin, wherein metal carbenes act as catalysts for the reaction. The use and discovery of Fischer-, Tebbe-, Grubbs- and Schrock-type metal carbenes have to a certain extent proven the general mechanism. These metal carbenes showed different activity for alkene metathesis. Only Grubbs- and Schrock-type carbenes proved to be highly active for metathesis. A lot of studies have been done on the reasons for the activity, but s...

  3. Ru Catalyzed Alkene-Alkyne Coupling. Total Synthesis of Amphidinolide P

    OpenAIRE

    Trost, Barry M.; Papillon, Julien P. N.; Nussbaumer, Thomas

    2005-01-01

    A coordinatively unsaturated ruthenium complex catalyzed the formation of a carbon-carbon bond between two judiciously chosen alkene and alkyne partners in good yield, and in a chemo- and regioselective fashion, in spite of the significant degree of unsaturation of the substrates. The resulting 1,4-diene forms the backbone of the cytotoxic marine natural product amphidinolide P. The alkene partner was rapidly assembled from (R)-glycidyl tosylate, which served as a linchpin in a one-flask, seq...

  4. Push-pull alkenes: structure and p-electron distribution

    Directory of Open Access Journals (Sweden)

    ERICH KLEINPETER

    2006-01-01

    Full Text Available Push-pull alkenes are substituted alkenes with one or two electron-donating substituents on one end of C=C double bond and with one or two electron-accepting substituents at the other end. Allowance for p-electron delocalization leads to the central C=C double bond becoming ever more polarized and with rising push-pull character, the p-bond order of this double bond is reduced and, conversely, the corresponding p-bond orders of the C–Don and C–Acc bonds are accordingly increased. This push-pull effect is of decisive influence on both the dynamic behavior and the chemical reactivity of this class of compounds and thus it is of considerable interest to both determine and to quantify the inherent push-pull effect. Previously, the barriers to rotation about the C=C, C–Don and/or C–Acc partial double bonds (DG±, as determined by dynamic NMR spectroscopy or the 13C chemical shift difference of the polarized C=C partial double bond (DdC=C were employed for this purpose. However, these parameters can have serious limitations, viz. the barriers can be immeasurable on the NMR timescale (either by being too high or too low; heavily-biased conformers are present, etc. or DdC=C behaves in a non-additive manner with respect to the combination of the four substituents. Hence, a general parameter to quantify the push-pull effect is not yet available. Ab initio MO calculations on a collection of compounds, together with NBO analysis, provided valuable information on the structure, bond energies, electron occupancies and bonding/antibonding interactions. In addition to DG±C=C (either experimentally determined or theoretically calculated and DdC=C, the bond length of the C=C partial double bond was also examined and it proved to be a reliable parameter to quantify the push-pull effect. Equally so, the quotient of the occupation numbers of the antibonding andbonding p orbitals of the central C=C partial double bond ( p*C=C/ pC=C could also be employed for

  5. Recent applications in natural product synthesis of dihydrofuran and -pyran formation by ring-closing alkene metathesis.

    Science.gov (United States)

    Jacques, Reece; Pal, Ritashree; Parker, Nicholas A; Sear, Claire E; Smith, Peter W; Ribaucourt, Aubert; Hodgson, David M

    2016-07-01

    In the past two decades, alkene metathesis has risen in prominence to become a significant synthetic strategy for alkene formation. Many total syntheses of natural products have used this transformation. We review the use, from 2003 to 2015, of ring-closing alkene metathesis (RCM) for the generation of dihydrofurans or -pyrans in natural product synthesis. The strategies used to assemble the RCM precursors and the subsequent use of the newly formed unsaturation will also be highlighted and placed in context. PMID:27108941

  6. The Origin of Anti-Markovnikov Regioselectivity in Alkene Hydroamination Reactions Catalyzed by [Rh(DPEphos)](.).

    Science.gov (United States)

    Couce-Rios, Almudena; Lledós, Agustí; Ujaque, Gregori

    2016-06-27

    The development of regioselective anti-Markovnikov alkene's hydroamination is a long-standing goal in catalysis. The [Rh(COD)(DPEphos)](+) complex is the most general and regioselective group 9 catalyst for such a process. The reaction mechanism for intermolecular hydroamination of alkenes catalyzed by [Rh(DPEphos)](+) complex is analyzed by means of DFT calculations. Hydroamination (alkene vs. amine activation routes) as well as oxidative amination pathways are analyzed. According to the computational results the operating mechanism can be generally described by alkene coordination, amine nucleophilic addition, proton transfer through the metal center and reductive elimination steps. The mechanism for the formation of the oxidative amination side product goes via a β-elimination after the nucleophilic addition and metal center protonation steps. The origin of the regioselectivity for the addition process (Markovnikov vs. anti-Markovnikov additions) is shown to be not charge but orbitally driven. Remarkably, η(2) to η(1) slippage degree on the alkene coordination mode is directly related to the regioselective outcome. PMID:27226329

  7. C(25) highly branched isoprenoid alkenes from the marine benthic diatom Pleurosigma strigosum.

    Science.gov (United States)

    Grossi, Vincent; Beker, Béatriz; Geenevasen, Jan A J; Schouten, Stefan; Raphel, Danielle; Fontaine, Marie-France; Sinninghe Damsté, Jaap S

    2004-11-01

    The hydrocarbon composition of the marine diatom Pleurosigma strigosum isolated from coastal Mediterranean sediments is described. A suite of five C(25) highly branched isoprenoid (HBI) alkenes with 2-5 double bonds were detected together with n-C(21:4) and n-C(21:5) alkenes and squalene. The analysis by (1)H and (13)C NMR spectroscopy of two isolated HBI alkenes allowed the structural identification of a novel C(25) HBI triene (2,6,10,14-tetramethyl-7-(3-methylpent-4-enyl)-pentadeca-5E,13-diene) and the first identification in diatom cells of 2,6,10,14-tetramethyl-7-(3-methylpent-4-enyl)-pentadec-5E-ene, an HBI previously detected in marine sediments and particulate matter. The other minor C(25) HBIs detected were a tetraene and a pentaene that have been previously identified in other diatoms from the genera Haslea and Rhizosolenia, and one other C(25) tetraene that could not be structurally identified. The structures of the HBI alkenes of P. strigosum were compared with those of C(25) homologues previously identified in three other Pleurosigma sp. (Pleurosigma intermedium, Pleurosigma planktonicum and Pleurosigma sp.). Unlike most structures previously reported, none of the HBI alkenes produced by P. strigosum showed an unsaturation at C7-C20, or E/Z isomerism of the trisubstituted double bond at C9-C10 (whenever present). PMID:15504440

  8. Highly efficient heterogeneous procedure for the conjugate addition of amines to electron deficient alkenes

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The novel efficient procedure has been developed for the conjugate addition of amines to electron deficient alkenes. K2CO3 supported on different carriers have been synthesized for the conjugate addition of amines and alkenes. After optimizing the reaction conditions, K2CO3/MgO was chosen as the most efficient catalyst for the reactions. The results showed that the catalyst was very efficient for the conjugate addition of amines to electron deficient alkenes with the excellent yields in several minutes. Operational simplicity, without need of any solvent, low cost of the catalyst used, high yields, reusability, excellent chemoselectivity, and applicability to large-scale reactions are the key features of this methodology.

  9. Mono-lacunary PrIII-Polyoxotungstate: Epoxidation of Alkenes with Unusual Selectivity

    Institute of Scientific and Technical Information of China (English)

    YANG Feng; MA Li; MA Zhi-Yuan

    2011-01-01

    The utilization of polyoxometalates (POMs) or their derivatives as homogeneous or heterogeneous catalysts in alkene epoxidation is a subject of considerable research activity[1]. The limitation to the use of POMs in these catalytic reactions is either their relatively low selectivity in epoxide formation or applicability for a rather limited type of alkenes. Therefore, it would be beneficial if the catalysts bear high selectivity for epoxidation and are applicable for a rather wide variety of alkenes, which is desirable in industrial processes and also vital for the selection of an ideal catalyst[2]. In search for an efficient and practical epoxidation method to utilize aqueous H2O2 as terminal oxidant, we focus on the rare-earth complexes with lacunary POM ligands.

  10. Alkene Cleavage Catalysed by Heme and Nonheme Enzymes: Reaction Mechanisms and Biocatalytic Applications

    Directory of Open Access Journals (Sweden)

    Francesco G. Mutti

    2012-01-01

    Full Text Available The oxidative cleavage of alkenes is classically performed by chemical methods, although they display several drawbacks. Ozonolysis requires harsh conditions (−78°C, for a safe process and reducing reagents in a molar amount, whereas the use of poisonous heavy metals such as Cr, Os, or Ru as catalysts is additionally plagued by low yield and selectivity. Conversely, heme and nonheme enzymes can catalyse the oxidative alkene cleavage at ambient temperature and atmospheric pressure in an aqueous buffer, showing excellent chemo- and regioselectivities in certain cases. This paper focuses on the alkene cleavage catalysed by iron cofactor-dependent enzymes encompassing the reaction mechanisms (in case where it is known and the application of these enzymes in biocatalysis.

  11. A Palladium-Catalyzed Three-Component Cross-Coupling of Conjugated Dienes or Terminal Alkenes with Vinyl Triflates and Boronic Acids

    OpenAIRE

    Liao, Longyan; Jana, Ranjan; Urkalan, Kaveri Balan; Sigman, Matthew S.

    2011-01-01

    A three-component coupling of vinyl triflates and boronic acids to alkenes catalyzed by palladium is reported. Using 1,3-dienes, selective 1,2-alkene difunctionalization is observed, whereas the use of terminal alkenes results in 1,1-alkene difunctionalization. The reaction outcome is attributed to the formation of stabilized, cationic Pd-π-allyl intermediates to regulate β-hydride elimination.

  12. Hydrogenation of Aliphatic Alkenes in a High-Temperature High-Pressure Packed-Bed Microreactor

    Czech Academy of Sciences Publication Activity Database

    Stavárek, Petr; Vajglová, Zuzana; Křišťál, Jiří; Herbstritt, F.; Heck, J.; Jiřičný, Vladimír

    Praha : Orgit, 2012, P1.164. ISBN 978-80-905035-1-9. [International Congress of Chemical and Process Engineering CHISA 2012 and 15th Conference PRES 2012 /20./. Prague (CZ), 25.08.2012-29.08.2012] Institutional support: RVO:67985858 Keywords : microreactor * hydrogenation reactions * aliphatic alkenes Subject RIV: CI - Industrial Chemistry, Chemical Engineering www.chisa.cz/2012

  13. Epoxidation of Alkenes with Aqueous Hydrogen Peroxide and Quaternary Ammonium Bicarbonate Catalysts

    DEFF Research Database (Denmark)

    Mielby, Jerrik Jørgen; Kegnæs, Søren

    2013-01-01

    A range of solid and liquid catalysts containing bicarbonate anions were synthesised and tested for the epoxidation of alkenes with aqueous hydrogen peroxide. The combination of bicarbonate anions and quaternary ammonium cations opens up for new catalytic systems that can help to overcome challen...

  14. ALKANES, METHYLALKANES, ALKENES AND ALKADIENES OF ADULT FLEA BEETLES, APHTHONA SPECIES

    Science.gov (United States)

    The adult beetles, Aphthona lacertosa and Aphthona nigriscutis, used as biocontrol agents for leafy spurge, had a complex mixture of hydrocarbons on their cuticular surface consisting of alkanes, methylalkanes, alkenes and alkadienes as determined by gas chromatography-mass spectrometry. A trace ...

  15. A new united atom force field for adsorption of alkenes in zeolites

    NARCIS (Netherlands)

    B. Liu; B. Smit; F. Rey; S. Valencia; S. Calero

    2008-01-01

    A new united atom force field was developed that accurately describes the adsorption properties of linear alkenes in zeolites. The force field was specifically designed for use in the inhomogeneous system and therefore a truncated and shifted potential was used. With the determined force field, we p

  16. The syn/anti-Dichotomy in the Palladium-Catalyzed Addition of Nucleophiles to Alkenes

    Czech Academy of Sciences Publication Activity Database

    Kočovský, Pavel; Bäckvall, J. E.

    2015-01-01

    Roč. 21, č. 1 (2015), s. 36-56. ISSN 0947-6539 Institutional support: RVO:61388963 Keywords : alkenes * catalysis * nucleophilic addition * palladium * stereochemistry Subject RIV: CC - Organic Chemistry Impact factor: 5.731, year: 2014 http://onlinelibrary.wiley.com/doi/10.1002/chem.201404070/pdf

  17. Catalytic production of sulfur heterocycles (dihydrobenzodithiins): a new application of ligand-based alkene reactivity.

    Science.gov (United States)

    Harrison, Daniel J; Fekl, Ulrich

    2009-12-28

    Activation of bis-o-phenylene tetrasulfide to render it a practical benzodithiete equivalent for [4+2] cycloadditions with alkenes has been achieved with catalytic amounts of Mo(tfd)(2)(bdt) (tfd = S(2)C(2)(CF(3))(2); bdt = S(2)C(6)H(4)). Substituted 2,3-dihydro-1,4-benzodithiins are produced. PMID:20024283

  18. Alkene Metathesis Catalysis: A Key for Transformations of Unsaturated Plant Oils and Renewable Derivatives

    Directory of Open Access Journals (Sweden)

    Dixneuf Pierre H.

    2016-03-01

    Full Text Available This account presents the importance of ruthenium-catalysed alkene cross-metathesis for the catalytic transformations of biomass derivatives into useful intermediates, especially those developed by the authors in the Rennes (France catalysis team in cooperation with chemical industry. The cross-metathesis of a variety of functional alkenes arising from plant oils, with acrylonitrile and fumaronitrile and followed by catalytic tandem hydrogenation, will be shown to afford linear amino acid derivatives, the precursors of polyamides. The exploration of cross-metathesis of bio-sourced unsaturated nitriles with acrylate with further catalytic hydrogenation has led to offer an excellent route to α,ω-amino acid derivatives. That of fatty aldehydes has led to bifunctional long chain aldehydes and saturated diols. Two ways of access to functional dienes by ruthenium-catalyzed ene-yne cross-metathesis of plant oil alkene derivatives with alkynes and by cross-metathesis of bio-sourced alkenes with allylic chloride followed by catalytic dehydrohalogenation, are reported. Ricinoleate derivatives offer a direct access to chiral dihydropyrans and tetrahydropyrans via ring closing metathesis. Cross-metathesis giving value to terpenes and eugenol for the straightforward synthesis of artificial terpenes and functional eugenol derivatives without C=C bond isomerization are described.

  19. Efficient synthesis of benzoprostacyclins using free-radical and palladium-catalyzed tandem alkene insertion strategies

    International Nuclear Information System (INIS)

    Efficient syntheses of PGI2 analogue 2a and its epimer 3 have been accomplished. Using aryl iodide 6 as the common intermediate, either radical or palladium-assisted tandem alkene insertion strategies have been employed for construction of the benzoprostacyclin framework

  20. The key role of water in the heterogeneous permanganate oxidation of $\\omega$-hydroxy alkenes

    OpenAIRE

    Baskaran, Sundarababu; Islam, Imadul; Vankar, Padma S; Chandrasekaran, Srinivasan

    1990-01-01

    Potassium permanganate–copper sulphate in dichloromethane in the presence of a catalytic amount of water effects a smooth oxidative cyclization of $\\omega$-hydroxy alkenes to $\\omega$-lactones in good yields with the net loss of one or more carbon atoms in the process.

  1. Synthesis and characterization of alkene-extended tetrathiafulvalenes with lateral alkyne appendages

    DEFF Research Database (Denmark)

    Nielsen, Mogens Brønsted; Gisselbrecht, Jean-Paul; Thorup, Niels;

    2003-01-01

    Tetrathiafulvalene (TTF) derivatives containing a diethynyl-substituted alkene spacer were synthesized and investigated for their electronic and structural properties. Co-planarity of the central diethynylethene unit and the two dithiole rings were confirmed by X-ray crystallographic analysis....

  2. Carbon Dioxide Induced Alkene Extrusion from Bis(pentamethylcyclopentadienyl)titanium(III) Alkyls

    NARCIS (Netherlands)

    Luinstra, Gerrit A.; Teuben, Jan H.

    1987-01-01

    Reaction of titanium(III) alkyls, (η5-C5Me5)2TiR (R = Et or Prn), in toluene solution with CO2 proceeds at room temperature with formation of the titanium formate (η5-C5Me5)2TiO2CH, and the corresponding alkene (ethene or propene).

  3. Atmospheric organic-phase photo-sensitized epoxidation of alkenes by α-dicarbonyls

    Directory of Open Access Journals (Sweden)

    G. Yu

    2012-06-01

    Full Text Available We report a new pathway of epoxide formation in organic phases via catalytic oxidation of alkenes by air with α-dicarbonyls as photo-sensitizers. Epoxide yields as high as 100% in 30 min of exposure to a solar simulator operating at the equivalent of 48.5° zenith angle are observed. The rate constants are proportional to light intensity and inversely proportional to temperature. The reaction rate is 0th order with respect to alkenes, implying that alkenes with small concentrations may rapidly be converted to epoxides in the organic phase. Based on a statistical estimate of α-dicarbonyl concentrations in secondary organic aerosol, we propose that this reaction could be highly effective under ambient conditions: the 0th-order lifetimes of organic-phase alkenes are estimated to be as low as 10 min, significantly shorter than their gas-phase 1st-order lifetimes, which are typically hours to days. The formation of epoxides in organic particles is expected to increase their hygroscopicity and ability to act as cloud condensation nuclei. Epoxides in deliquesced particles can subsequently form polyalcohols, oligomers, organosulphates and organonitrates, increasing the organic mass in the atmospheric waters.

  4. Copper-catalyzed electrophilic carbofunctionalization of alkynes to highly functionalized tetrasubstituted alkenes.

    Science.gov (United States)

    Suero, Marcos G; Bayle, Elliott D; Collins, Beatrice S L; Gaunt, Matthew J

    2013-04-10

    Copper catalysts enable the electrophilic carbofunctionalization of alkynes with vinyl- and diaryliodonium triflates. The new process forms highly substituted alkenyl triflates from a range of alkynes via a pathway that is opposite to classical carbometalation. The alkenyl triflate products can be elaborated through cross-coupling reactions to generate synthetically useful tetrasubstituted alkenes. PMID:23521626

  5. Copper-Catalyzed Enantioselective Intramolecular Alkene Amination/Intermolecular Heck-Type Coupling Cascade

    OpenAIRE

    Liwosz, Timothy W.; Chemler, Sherry R.

    2012-01-01

    Enantioselective copper-catalyzed cycliza-tion of γ-alkenylsulfonamides and a δ-alkenylsulfonamide in the presence of a range of vinyl arenes results in variously functionalized 2-substituted chiral nitrogen heterocycles via a formal alkene C–H functionalization process. Application of this reaction to the concise synthesis of a 5-HT7 receptor antagonist is demonstrated.

  6. Copper-catalyzed enantioselective intramolecular alkene amination/intermolecular Heck-type coupling cascade.

    Science.gov (United States)

    Liwosz, Timothy W; Chemler, Sherry R

    2012-02-01

    Enantioselective copper-catalyzed cyclization of γ-alkenylsulfonamides and a δ-alkenylsulfonamide in the presence of a range of vinyl arenes results in variously functionalized 2-substituted chiral nitrogen heterocycles via a formal alkene C-H functionalization process. Application of this reaction to the concise synthesis of a 5-HT(7) receptor antagonist is demonstrated. PMID:22257169

  7. QUANTIFICATION OF FUGITIVE REACTIVE ALKENE EMISSIONS FROM PETROCHEMICAL PLANTS WITH PERFLUOROCARBON TRACERS.

    Energy Technology Data Exchange (ETDEWEB)

    SENUM,G.I.; DIETZ,R.N.

    2004-06-30

    Recent studies demonstrate the impact of fugitive emissions of reactive alkenes on the atmospheric chemistry of the Houston Texas metropolitan area (1). Petrochemical plants located in and around the Houston area emit atmospheric alkenes, such as ethene, propene and 1,3-butadiene. The magnitude of emissions is a major uncertainty in assessing their effects. Even though the petrochemical industry reports that fugitive emissions of alkenes have been reduced to less than 0.1% of daily production, recent measurement data, obtained during the TexAQS 2000 experiment indicates that emissions are perhaps a factor of ten larger than estimated values. Industry figures for fugitive emissions are based on adding up estimated emission factors for every component in the plant to give a total estimated emission from the entire facility. The dramatic difference between estimated and measured rates indicates either that calculating emission fluxes by summing estimates for individual components is seriously flawed, possibly due to individual components leaking well beyond their estimated tolerances, that not all sources of emissions for a facility are being considered in emissions estimates, or that there are known sources of emissions that are not being reported. This experiment was designed to confirm estimates of reactive alkene emissions derived from analysis of the TexAQS 2000 data by releasing perfluorocarbon tracers (PFTs) at a known flux from a petrochemical plant and sampling both the perfluorocarbon tracer and reactive alkenes downwind using the Piper-Aztec research aircraft operated by Baylor University. PFTs have been extensively used to determine leaks in pipelines, air infiltration in buildings, and to characterize the transport and dispersion of air parcels in the atmosphere. Over 20 years of development by the Tracer Technology Center (TTC) has produced a range of analysis instruments, field samplers and PFT release equipment that have been successfully deployed in a

  8. Fast and Green Microwave-Assisted Conversion of Essential Oil Allylbenzenes into the Corresponding Aldehydes via Alkene Isomerization and Subsequent Potassium Permanganate Promoted Oxidative Alkene Group Cleavage

    OpenAIRE

    Thi X. Thi Luu; Trinh To Lam; Thach Ngoc Le; Fritz Duus

    2009-01-01

    Essential oil allylbenzenes from have been converted quickly and efficiently into the corresponding benzaldehydes in good yields by a two-step “green” reaction pathway based on a solventless alkene group isomerization by KF/Al2O3 to form the corresponding 1-arylpropene and a subsequent solventless oxidation of the latter to the corresponding benzaldehyde by KMnO4/CuSO4·5H2O. The assistance by microwave irradiation results in very short reaction times (<15 minutes). The green conversion of ...

  9. Alkoxy Hydrosilanes As Surrogates of Gaseous Silanes for Hydrosilylation of Alkenes.

    Science.gov (United States)

    Buslov, Ivan; Keller, Sébastien Carlos; Hu, Xile

    2016-04-15

    Me2SiH2, MeSiH3, and SiH4 are gaseous and flammable silanes that are inconvenient to use in chemical reactions. Catalytic amounts of a nickel pincer complex and NaO(t)Bu are reported to allow the synthesis of alkyl hydrosilanes from alkenes and alkoxy hydrosilanes, leading to the replacement of Me2SiH2, MeSiH3, and SiH4 by Me2(MeO)SiH, Me(EtO)2SiH, and (MeO)3SiH in hydrosilylation reactions of alkenes. The scope and mechanism of the reactions are also described. PMID:27045341

  10. Stabilized borata-alkene formation: structural features, reactions and the role of the counter cation.

    Science.gov (United States)

    Kohrt, Sonja; Dachwitz, Steffen; Daniliuc, Constantin G; Kehr, Gerald; Erker, Gerhard

    2015-12-28

    Dimethylbenzofulvene adds Piers' borane [HB(C6F5)2] at the indene double bond to give a mixture of regioisomeric boranes 8a,b. Subsequent isomerization under equilibrium conditions gives the isopropyl substituted 1H and 3H borylindenes 10a,b. Their treatment with the bulky LiTMP base under frustrated Lewis pair conditions resulted in a clean deprotonation reaction to give the borata-alkene 14. Its X-ray crystal structure analysis indicated a pronounced B[double bond, length as m-dash]C double bond character and thus a borata-benzofulvene description. The borata-alkene underwent (probably stepwise) [4 + 2] cycloaddition reactions with chalcone derivatives and a formal [6 + 2] cycloaddition with phenylmethylketene. Many products and derivatives were characterized by X-ray diffraction. PMID:26584629

  11. Alkenes as Chelating Groups in Diastereoselective Additions of Organometallics to Ketones

    OpenAIRE

    Raffier, Ludovic; Gutierrez, Osvaldo; Stanton, Gretchen R.; Kozlowski, Marisa C.; Walsh, Patrick J.

    2014-01-01

    Alkenes have been discovered to be chelating groups to Zn(II), enforcing highly stereoselective additions of organozincs to β,γ-unsaturated ketones. 1H NMR studies and DFT calculations provide support for this surprising chelation mode. The results expand the range of coordinating groups for chelation-controlled carbonyl additions from heteroatom Lewis bases to simple C–C double bonds, broadening the 60 year old paradigm.

  12. Hydrogenation of Aliphatic Alkenes in a High-Temperature High-Pressure Packed-Bed Microreactor

    OpenAIRE

    Stavárek, Petr

    2012-01-01

    This contribution presents results of the characterization of a new high-temperature high-pressure integrated packed-bed microreactor (MCTU 600 from Ehrfeld Mikrotechnik BTS GmbH) for lab-scale catalyst testing. As the model reaction we used the hydrogenation of C4-C5 aliphatic alkenes heterogeneously catalyzed by Pt/Al2O3 or Pd/Al2O3.

  13. Reactions of azoalkenes derived from hydrazones of ethyl bromopyruvate with electron rich alkenes and heterocycles

    OpenAIRE

    Clarke, S.; Gilchrist, Thomas L.; Lemos, A.; G. Roberts, Tony

    1991-01-01

    Three hydrazones of ethyl bromopyruvate, the dinitrophenylhydrazone 2a, the toluene-4-sulphonylhydrazone 2b and the t-butoxycarbonylhydrazone 2c, have been reacted with a series of nucleophilic alkenes and heterocycles in the presence of sodium carbonate. Azoalkenes 3 are presumed as intermediates and adducts have been isolated. The azoalkenes derived from hydrazones 2a and 2c are found to be useful electrophiles and electrophilic dienes.

  14. Enantioselective CuH-Catalyzed Reductive Coupling of Aryl Alkenes and Activated Carboxylic Acids.

    Science.gov (United States)

    Bandar, Jeffrey S; Ascic, Erhad; Buchwald, Stephen L

    2016-05-11

    A new method for the enantioselective reductive coupling of aryl alkenes with activated carboxylic acid derivatives via copper hydride catalysis is described. Dual catalytic cycles are proposed, with a relatively fast enantioselective hydroacylation cycle followed by a slower diastereoselective ketone reduction cycle. Symmetrical aryl carboxyclic anhydrides provide access to enantioenriched α-substituted ketones or alcohols with excellent stereoselectivity and functional group tolerance. PMID:27121395

  15. Copper-Catalyzed Amino Lactonization and Amino Oxygenation of Alkenes Using O-Benzoylhydroxylamines.

    Science.gov (United States)

    Hemric, Brett N; Shen, Kun; Wang, Qiu

    2016-05-11

    A copper-catalyzed amino lactonization of unsaturated carboxylic acids has been achieved as well as the analogous intermolecular three-component amino oxygenation of olefins. The transformation features mild conditions and a remarkably broad substrate scope, offering a novel and efficient approach to construct a wide range of amino lactones as well as 1,2-amino alcohol derivatives. Mechanistic studies suggest that the reaction proceeds via a distinctive O-benzoylhydroxylamine-promoted electrophilic amination of alkenes. PMID:27114046

  16. Synthesis of Fine Chemicals by the Conjugate Addition of Nitroalkanes to Electrophilic Alkenes

    Institute of Scientific and Technical Information of China (English)

    R. Ballini; G. Bosica; D. Fiorini; A. Palmieri

    2005-01-01

    @@ 1Introduction It is well known the ability of primary and secondary nitroalkanes to generate carbanions (under basic conditions) strongly stabilized by the electron-withdrawing effect of the nitro group[1-4]. Thus, the main use of nitroalkanes is devoted to the generation of new carbon-carbon bonds through two principal approaches (Scheme 1): (i) reaction with carbonyl derivatives (nitroaldol-Henry-reaction), and (ii) Michael addition to electron poor alkenes.

  17. Fast and Green Microwave-Assisted Conversion of Essential Oil Allylbenzenes into the Corresponding Aldehydes via Alkene Isomerization and Subsequent Potassium Permanganate Promoted Oxidative Alkene Group Cleavage

    Directory of Open Access Journals (Sweden)

    Thi X. Thi Luu

    2009-09-01

    Full Text Available Essential oil allylbenzenes from have been converted quickly and efficiently into the corresponding benzaldehydes in good yields by a two-step “green” reaction pathway based on a solventless alkene group isomerization by KF/Al2O3 to form the corresponding 1-arylpropene and a subsequent solventless oxidation of the latter to the corresponding benzaldehyde by KMnO4/CuSO4·5H2O. The assistance by microwave irradiation results in very short reaction times (<15 minutes. The green conversion of eugenol (4-allyl-2-methoxyphenol into vanillin (4-hydroxy-3-methoxybenzaldehyde has been carried out in a similar way, requiring however two additional microwave-assisted synthetic steps for acetylation of the hydroxy group prior to the oxidation reaction, and for the final deacetylation of vanillin acetate (4-acetoxy-3-methoxybenzaldehyde by KF/Al2O3 under solvent-free conditions, respectively.

  18. Charge transfer from the n-hexadecane radical cation to cycloalkanes, alkenes and aromatics

    International Nuclear Information System (INIS)

    Charge transfer from n-hexadecane radical cations C16H34+ to solutes as cycloalkanes, alkenes and aromatics was studied by pulse radiolysis. Using ion-pair kinetics the rate constants ksub(s) of the electron transfer reactions C16H34+ + S ->sup(ks) S+ + C16H34 were determined. The electron transfer rate constants ksub(s) increase from low values for slightly exothermic reactions to a limiting value of 9 . 109 dm3 mol-1 s-1 when the electron transfer reaction is more exothermic than -0.4 eV. (orig.)

  19. A new environmental friendly clay catalyst for one-pot coiodination and epoxidation of alkenes

    International Nuclear Information System (INIS)

    The commercial Brazilian clay Bentonit BrasgelTM was characterized by chemical and textural analyses, XRD, and 27Al and 29Si MAS-NMR, that indicated the presence of α-quartz and smectite as clay-minerals. This natural clay proved to be an efficient catalyst for the conversion of alkenes into epoxides by the reaction with iodine/water followed by in situ addition of KOH in hexane (80-91 % yield). Similar results were obtained with Bentonit BrasgelTM intercalated with Ag(I). (author)

  20. Cross-metathesis reaction of α- and β-vinyl C-glycosides with alkenes.

    Science.gov (United States)

    Šnajdr, Ivan; Parkan, Kamil; Hessler, Filip; Kotora, Martin

    2015-01-01

    Cross-metathesis of α- and β-vinyl C-deoxyribosides and α-vinyl C-galactoside with various terminal alkenes under different conditions was studied. The cross-metathesis of the former proceeded with good yields of the corresponding products in ClCH2CH2Cl the latter required the presence of CuI in CH2Cl2 to achieve good yields of the products. A simple method for the preparation of α- and β-vinyl C-deoxyribosides was also developed. In addition, feasibility of deprotection and further transformations were briefly explored. PMID:26425194

  1. Cross-metathesis reaction of α- and β-vinyl C-glycosides with alkenes

    Directory of Open Access Journals (Sweden)

    Ivan Šnajdr

    2015-08-01

    Full Text Available Cross-metathesis of α- and β-vinyl C-deoxyribosides and α-vinyl C-galactoside with various terminal alkenes under different conditions was studied. The cross-metathesis of the former proceeded with good yields of the corresponding products in ClCH2CH2Cl the latter required the presence of CuI in CH2Cl2 to achieve good yields of the products. A simple method for the preparation of α- and β-vinyl C-deoxyribosides was also developed. In addition, feasibility of deprotection and further transformations were briefly explored.

  2. Copper-promoted synthesis of 1,4-benzodiazepinones via alkene diamination

    Science.gov (United States)

    Karyakarte, Shuklendu D.; Sequeira, Fatima C.; Zibreg, Garrick H.; Huang, Guoqing; Matthew, Josiah P.; Ferreira, Marina M. M.

    2015-01-01

    A new method for the synthesis of 2-aminomethyl functionalized 1,4-benzodiazepin-5-ones is presented. The benzodiazepine core is well-known to interact with biological receptors and many pharmaceutical drugs are derived from this structure. The alkene diamination strategy is employed for the first time for the synthesis of 1,4-benzodiazepinones. In this reaction, copper(2-ethylhexanoate)2 serves as promoter and a range of external amines can be coupled with 2-sulfonamido-N-allyl benzamides to generate the 1,4-benzodiazepinones in good yields. PMID:26034340

  3. A combined experimental and theoretical study of the thermal cycloaddition of aryl azides with activated alkenes.

    OpenAIRE

    Zeghada, Sarah; Bentabed-Ababsa, Ghenia; Derdour, Aïcha; Abdelmounim, Safer; Domingo, Luis .R.; Sáez, José A.; Roisnel, Thierry; Nassar, Ekhlass; Mongin, Florence

    2011-01-01

    Reactions were performed from aryl azides on the one hand, and activated alkenes coming from β-dicarbonyl compounds or malonodinitrile on the other hand, either with recourse to conventional heating or to microwave activation, to afford 1-aryl-1H-1,2,3-triazoles. The mechanism and the regioselectivity of the reactions involving β-dicarbonyl compounds have been theoretically studied using DFT methods at the B3LYP/6-31G* level: they are domino processes comprising a tautomeric equilibrium of th...

  4. Functional Polyethylene Glycol with Carboxyl-supported Platinum as an Efficient Catalysis System for the Hydrosilylation of Alkenes

    Institute of Scientific and Technical Information of China (English)

    程媛; 彭家建; 杨虎; 厉嘉云; 来国桥; 李小年

    2012-01-01

    A series of carboxylated long chain polyethylene glycols(abbreviated as PEGCOOH) has been synthesized and used to support chloroplatinic acid.These supported catalysts were then tested for their efficiency in the hydrosilylation of alkenes.The factors affecting their catalytic properties,e.g.relative molecular mass of polyethylene glycol,reaction temperature,platinum content,and type of alkenes,have been studied.It was found that the activity of the platinum catalyst decreased with increasing length of the polyethylene glycol chain,and increased with reaction temperature.Moreover,these catalysts could be reused several times without a noticeable decrease in activity or selectivity.The reaction pathway leading to excellent selectivity for the β-adduct of hydrosilylation of alkenes with triethoxysilane catalyzed by this catalysis system was discussed.

  5. Sources of C₂-C₄ alkenes, the most important ozone nonmethane hydrocarbon precursors in the Pearl River Delta region.

    Science.gov (United States)

    Zhang, Yanli; Wang, Xinming; Zhang, Zhou; Lü, Sujun; Huang, Zhonghui; Li, Longfeng

    2015-01-01

    Surface ozone is becoming an increasing concern in China's megacities such as the urban centers located in the highly industrialized and densely populated Pearl River Delta (PRD) region, where previous studies suggested that ozone production is sensitive to VOC emissions with alkenes being important precursors. However, little was known about sources of alkenes. Here we present our monitoring of ambient volatile organic compounds at four representative urban, suburban and rural sites in the PRD region during November-December 2009, which experienced frequent ozone episodes. C2-C4 alkenes, whose total mixing ratios were 11-20% of non-methane hydrocarbons (NMHCs) quantified, accounted for 38-64% of ozone formation potentials (OFPs) and 30-50% of the total hydroxyl radical (OH) reactivity by NMHCs. Ethylene was the most abundant alkene, accounting for 8-15% in total mixing ratios of NMHCs and contributed 25-46% of OFPs. Correlations between C2-C4 alkenes and typical source tracers suggested that ethylene might be largely related to vehicle exhausts and industry activities, while propene and butenes were much more LPG-related. Positive Matrix Factorization (PMF) confirmed that vehicle exhaust and liquefied petroleum gas (LPG) were two major sources that altogether accounted for 52-62%, 58-77%, 73-83%, 68-79% and 73-84% for ethylene, propene, 1-butene, trans-2-butene and cis-2-butene, respectively. Vehicle exhausts alone contributed 32-49% ethylene and 35-41% propene. Industry activities contributed 13-23% ethylene and 7-20% propene. LPG instead contributed the most to butenes (38-65%) and substantially to propene (23-36%). Extensive tests confirmed high fractions of propene and butenes in LPG then used in Guangzhou and in LPG combustion plumes; therefore, limiting alkene contents in LPG would benefit regional ozone control. PMID:25260169

  6. The mechanism of alkene addition to a nickel bis(dithiolene) complex: the role of the reduced metal complex.

    Science.gov (United States)

    Dang, Li; Shibl, Mohamed F; Yang, Xinzheng; Alak, Aiman; Harrison, Daniel J; Fekl, Ulrich; Brothers, Edward N; Hall, Michael B

    2012-03-14

    The binding of an alkene by Ni(tfd)(2) [tfd = S(2)C(2)(CF(3))(2)] is one of the most intriguing ligand-based reactions. In the presence of the anionic, reduced metal complex, the primary product is an interligand adduct, while in the absence of the anion, dihydrodithiins and metal complex decomposition products are preferred. New kinetic (global analysis) and computational (DFT) data explain the crucial role of the anion in suppressing decomposition and catalyzing the formation of the interligand product through a dimetallic complex that appears to catalyze alkene addition across the Ni-S bond, leading to a lower barrier for the interligand adduct. PMID:22364208

  7. Phosphotungstic acid supported on magnetic nanoparticles as an efficient reusable catalyst for epoxidation of alkenes

    Energy Technology Data Exchange (ETDEWEB)

    Kooti, M., E-mail: m_kooti@scu.ac.ir [Department of Chemistry, College of Science, Shahid Chamran University, Ahvaz 61357- 43169 (Iran, Islamic Republic of); Afshari, M. [Department of Chemistry, College of Science, Shahid Chamran University, Ahvaz 61357- 43169 (Iran, Islamic Republic of)

    2012-11-15

    Highlights: ► Phosphotungstic acid supported on functionalized cobalt ferrite was prepared. ► Silica coated cobalt ferrite nanoparticles were used as support. ► This composite was successfully used as catalyst for epoxidation of alkenes. ► Oxidation reactions were carried out in the presence of t-BuOOH as oxidant. ► The catalyst can be readily separated from solution by magnetic field. -- Abstract: A new magnetically separable catalyst consisting of phosphotungstic acid supported on imidazole functionalized silica coated cobalt ferrite nanoparticles was prepared. The synthesized catalyst was characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR), and inductively coupled plasma atomic emission spectroscopy (ICP-AES). This immobilized phosphotungstic acid was shown to be an efficient heterogeneous catalyst for the epoxidation of various alkenes using tert-butylhydroperoxide (t-BuOOH) as oxidant. The catalyst is readily recovered by simple magnetic decantation and can be recycled several times with no significant loss of catalytic activity.

  8. DFT Rationalization of the Diverse Outcomes of the Iodine(III)-Mediated Oxidative Amination of Alkenes.

    Science.gov (United States)

    Funes-Ardoiz, Ignacio; Sameera, W M C; Romero, R Martín; Martínez, Claudio; Souto, José A; Sampedro, Diego; Muñiz, Kilian; Maseras, Feliu

    2016-05-23

    A computational study of the mechanism for the iodine(III)-mediated oxidative amination of alkenes explains the experimentally observed substrate dependence on product distribution. Calculations with the M06 functional have been carried out on the reaction between PhI(N(SO2 Me)2 )2 and three different representative substrates: styrene, α-methylstyrene, and (E)-methylstilbene. All reactions start with electrophilic attack by a cationic PhI(N(SO2 Me)2 )(+) unit on the double bond, and formation of an intermediate with a single C-I bond and a planar sp(2) carbocationic center. The major path, leading to 1,2-diamination, proceeds through a mechanism in which the bissulfonimide initially adds to the alkene through an oxygen atom of one sulfonyl group. This behavior is now corroborated by experimental evidence. An alternative path, leading to an allylic amination product, takes place through deprotonation at an allylic C-H position in the common intermediate. The regioselectivity of this amination depends on the availability of the resonant structures of an alternate carbocationic intermediate. Only in cases where a high electronic delocalization is possible, as in (E)-methylstilbene, does the allylic amination occur without migration of the double bond. PMID:27106535

  9. Copper(I)-catalyzed carbon-halogen bond-selective boryl substitution of alkyl halides bearing terminal alkene moieties

    OpenAIRE

    Iwamoto, Hiroaki; Kubota, Koji; Yamamoto, Eiji; Ito, Hajime

    2015-01-01

    The selective boryl substitution of alkyl halides bearing terminal C=C double bonds has been achieved using a copper(I)/tricyclohexylphosphine or copper(I)/o-diphenylphosphinophenol catalyst. This reaction represents a useful complementary approach to conventional procedures for the hydroboration of C=C double bonds or the borylative cyclization of alkyl halides bearing terminal alkenes.

  10. Epoxidation of alkenes through oxygen activation over a bifunctional CuO/Al2O3 catalyst.

    Science.gov (United States)

    Scotti, Nicola; Ravasio, Nicoletta; Zaccheria, Federica; Psaro, Rinaldo; Evangelisti, Claudio

    2013-03-01

    The epoxidation of alkenes was carried out over a CuO/Al(2)O(3) catalyst using cumene as an oxygen carrier, through a one-pot reaction, giving high conversion and selectivity with different substrates. Trans-β-methylstyrene gave the corresponding epoxide in 95% yield after 3 h. PMID:23358661

  11. Selektivní katalytické krakování vyšších alkenů

    Czech Academy of Sciences Publication Activity Database

    Kolena, J.; Morávek, P.; Bortnovsky, O.; Tukač, V.; Hanika, Jiří

    Praha : PetroCHemProgress, 2004, s. 46-55. ISBN 80-02-01576-2. [Aprochem 2004 /13./. Milovy (CZ), 20.09.2004-22.09.2004] R&D Projects: GA MŠk LN00B142 Institutional research plan: CEZ:AV0Z4072921 Keywords : catalytic craking * alkenes Subject RIV: CI - Industrial Chemistry, Chemical Engineering

  12. Self-assembled monolayers of 1-alkenes on oxidized platinum surfaces as platforms for immobilized enzymes for biosensing

    NARCIS (Netherlands)

    Aznar Alonso, J.M.; Bielen, A.A.M; Olthuis, W.; Kengen, S.W.M; Zuilhof, H.; Franssen, M.

    2016-01-01

    Alkene-based self-assembled monolayers grafted on oxidized Pt surfaces were used as a scaffold to covalently immobilize oxidase enzymes, with the aim to develop an amperometric biosensor platform. NH2-terminated organic layers were functionalized with either aldehyde (CHO) or N-hydroxysuccinimide (N

  13. Rh(iii)-catalyzed C-H activation/cyclization of oximes with alkenes for regioselective synthesis of isoquinolines.

    Science.gov (United States)

    Chen, Renjie; Qi, Jifeng; Mao, Zhenjun; Cui, Sunliang

    2016-07-14

    A Rh(iii)-catalyzed C-H activation/cyclization of oximes and alkenes for facile and regioselective access to isoquinolines has been developed. This protocol features mild reaction conditions and easily accessible starting materials, and has been applied to the concise synthesis of moxaverine. A kinetic isotope effect study was conducted and a plausible mechanism was proposed. PMID:27273816

  14. Efficient alkene epoxidation catalyzed by molybdenyl acetylacetonate supported on aminated UiO-66 metal−organic framework

    Energy Technology Data Exchange (ETDEWEB)

    Kardanpour, Reihaneh [Department of Chemistry, Catalysis Division, University of Isfahan, Isfahan 81746-73441 (Iran, Islamic Republic of); Tangestaninejad, Shahram, E-mail: stanges@sci.ui.ac.ir [Department of Chemistry, Catalysis Division, University of Isfahan, Isfahan 81746-73441 (Iran, Islamic Republic of); Mirkhani, Valiollah, E-mail: mirkhani@sci.ui.ac.ir [Department of Chemistry, Catalysis Division, University of Isfahan, Isfahan 81746-73441 (Iran, Islamic Republic of); Moghadam, Majid, E-mail: moghadamm@sci.ui.ac.ir [Department of Chemistry, Catalysis Division, University of Isfahan, Isfahan 81746-73441 (Iran, Islamic Republic of); Mohammadpoor-Baltork, Iraj; Zadehahmadi, Farnaz [Department of Chemistry, Catalysis Division, University of Isfahan, Isfahan 81746-73441 (Iran, Islamic Republic of)

    2015-03-15

    Metal–organic frameworks (MOFs) containing Mo Schiff base complexes were prepared by post-synthesis method and applied as efficient catalysts in the epoxidation of alkenes with tert-BuOOH. In this manner, UiO-66-NH{sub 2} (UiO=University of Oslo) MOF was reacted with salicylaldehyde and thiophene-2-carbaldehyde to produce bidentate Schiff bases. Then, the Schiff base ligands were used for immobilization of molybdenyl acetylacetonate. These new catalysts were characterized by FT-IR, UV–vis spectroscopic techniques, X-ray diffraction (XRD), BET, inductively coupled plasma atomic emission spectroscopy (ICP-AES) and field emission scanning electron microscopy (FE-SEM). These catalytic systems showed excellent activity in the epoxidation of alkenes such as cyclic and linear ones with tert-butyl hydroperoxide (TBHP) in 1,2-dichloroethane, and reused several times without any appreciable loss of their activity. - Graphical abstract: Efficient alkene epoxidation with TBHP catalyzed by heterogeneous and reusable molybdenum base catalysts is reported. - Highlights: • UiO-66-NH{sub 2} was modified with salicylaldehyde and thiophene-2-carbaldehyde. • The Schiff base groups were used for immobilization of MoO{sub 2}(acac){sub 2}. • The heterogeneous catalysts were prepared. • The prepared catalysts were used for epoxidation of alkenes. • Compared to other catalyst, our catalysts were more efficient and forceful.

  15. Trisubstituted (E)-Alkene Dipeptide Isosteres as β-Turn Promoters in the Gramicidin S Cyclodecapeptide Scaffold

    OpenAIRE

    Xiao, Jingbo; Weisblum, Bernard; Wipf, Peter

    2006-01-01

    A concise synthesis of a gramicidin S analogue with trisubstituted (E)-alkene dipeptide isostere (TEADI) replacements at both DPhe-Pro positions was realized. Conformational analysis demonstrated that TEADIs can serve as type II β-turn promoters in a cyclic scaffold and successfully mimic a proline residue.

  16. Efficient alkene epoxidation catalyzed by molybdenyl acetylacetonate supported on aminated UiO-66 metal−organic framework

    International Nuclear Information System (INIS)

    Metal–organic frameworks (MOFs) containing Mo Schiff base complexes were prepared by post-synthesis method and applied as efficient catalysts in the epoxidation of alkenes with tert-BuOOH. In this manner, UiO-66-NH2 (UiO=University of Oslo) MOF was reacted with salicylaldehyde and thiophene-2-carbaldehyde to produce bidentate Schiff bases. Then, the Schiff base ligands were used for immobilization of molybdenyl acetylacetonate. These new catalysts were characterized by FT-IR, UV–vis spectroscopic techniques, X-ray diffraction (XRD), BET, inductively coupled plasma atomic emission spectroscopy (ICP-AES) and field emission scanning electron microscopy (FE-SEM). These catalytic systems showed excellent activity in the epoxidation of alkenes such as cyclic and linear ones with tert-butyl hydroperoxide (TBHP) in 1,2-dichloroethane, and reused several times without any appreciable loss of their activity. - Graphical abstract: Efficient alkene epoxidation with TBHP catalyzed by heterogeneous and reusable molybdenum base catalysts is reported. - Highlights: • UiO-66-NH2 was modified with salicylaldehyde and thiophene-2-carbaldehyde. • The Schiff base groups were used for immobilization of MoO2(acac)2. • The heterogeneous catalysts were prepared. • The prepared catalysts were used for epoxidation of alkenes. • Compared to other catalyst, our catalysts were more efficient and forceful

  17. Uncatalyzed thermal gas phase aziridination of alkenes by organic azides. Part I: Mechanisms with discrete nitrene species

    Indian Academy of Sciences (India)

    S PREMILA DEVI; TEJESHWORI SALAM; R H DUNCAN LYNGDOH

    2016-05-01

    Alkene aziridination by azides through uncatalyzed thermal gas phase routes has been studiedusing the DFT B3LYP/6-31G(d,p) method, where the possible role of discrete nitrene intermediates is emphasized.The thermal decomposition of azides is studied using the MP2/aug-cc-pVDZ strategy as well. The MP2(but not the B3LYP) results discount the existence of singlet alkylnitrenes where the alkyl group has an α-hydrogen. Addition of the lowest lying singlet and triplet nitrenes R-N (R = H, Me, Ac) to four different alkenesubstrates leading to aziridine formation was studied by the B3LYP method. Singlet nitrenes with alkenes canyield aziridines via a concerted mechanism, where H-N insertion takes place without a barrier, whereas Me-Nshows larger barriers than Ac-N. Methyl substitution in the alkene favors this reaction. Triplet nitrene additionto alkenes is studied as a two-step process, where the initially formed diradical intermediates cyclize to formaziridines by ISC (intersystem crossing) and collapse. Scope for C-C bond rotation in the diradical leads to lossof stereochemical integrity for triplet nitrene addition to cis- and trans-2-butenes. Geometries of the transitionstates in the various reaction steps studied here are described as “early” or “late” in good accordance with theHammond postulate.

  18. Selective preparation of terminal alkenes from aliphatic carboxylic acids by a palladium-catalysed decarbonylation-eliminiation reaction

    NARCIS (Netherlands)

    Notre, le J.E.L.; Scott, E.L.; Franssen, M.C.R.; Sanders, J.P.M.

    2010-01-01

    Trialkylamines were used as additives in the decarbonylation–elimination reaction catalysed by the combination of palladium(II) chloride and DPE-Phos. Aliphatic carboxylic acids were transformed at relatively low temperature into terminal alkenes in high yield and high selectivity, without the need

  19. Catalytic, Enantioselective Addition of Alkyl Radicals to Alkenes via Visible-Light-Activated Photoredox Catalysis with a Chiral Rhodium Complex.

    Science.gov (United States)

    Huo, Haohua; Harms, Klaus; Meggers, Eric

    2016-06-01

    An efficient enantioselective addition of alkyl radicals, oxidatively generated from organotrifluoroborates, to acceptor-substituted alkenes is catalyzed by a bis-cyclometalated rhodium catalyst (4 mol %) under photoredox conditions. The practical method provides yields up to 97% with excellent enantioselectivities up to 99% ee and can be classified as a redox neutral, electron-transfer-catalyzed reaction. PMID:27218134

  20. Aldehyde-Selective Wacker-Type Oxidation of Unbiased Alkenes Enabled by a Nitrite Co-Catalyst

    KAUST Repository

    Wickens, Zachary K.

    2013-09-13

    Breaking the rules: Reversal of the high Markovnikov selectivity of Wacker-type oxidations was accomplished using a nitrite co-catalyst. Unbiased aliphatic alkenes can be oxidized with high yield and aldehyde selectivity, and several functional groups are tolerated. 18O-labeling experiments indicate that the aldehydic O atom is derived from the nitrite salt.

  1. Self-assembled monolayers of 1-alkenes on oxidized platinum surfaces as platforms for immobilized enzymes for biosensing

    NARCIS (Netherlands)

    Alonso, Jose Maria; Bielen, Abraham A.M.; Olthuis, Wouter; Kengen, Servé W.M.; Zuilhof, Han; Franssen, Maurice C.R.

    2016-01-01

    Alkene-based self-assembled monolayers grafted on oxidized Pt surfaces were used as a scaffold to covalently immobilize oxidase enzymes, with the aim to develop an amperometric biosensor platform. NH2-terminated organic layers were functionalized with either aldehyde (CHO) or N-hydroxy

  2. Molybdenum-catalyzed conversion of diols and biomass-derived polyols to alkenes using isopropyl alcohol as reductant and solvent

    DEFF Research Database (Denmark)

    Dethlefsen, Johannes Rytter; Lupp, Daniel; Gorfo, Ayele Teshome;

    2015-01-01

    Chemical processes capable of reducing the high oxygen content of biomass-derived polyols are in demand in order to produce renewable substitutes for chemicals of fossil origin. Deoxydehydration (DODH) is an attractive reaction that in a single step transforms a vicinal diol into an alkene, but the...

  3. Iron- and Cobalt-Catalyzed Alkene Hydrogenation: Catalysis with Both Redox-Active and Strong Field Ligands.

    Science.gov (United States)

    Chirik, Paul J

    2015-06-16

    The hydrogenation of alkenes is one of the most impactful reactions catalyzed by homogeneous transition metal complexes finding application in the pharmaceutical, agrochemical, and commodity chemical industries. For decades, catalyst technology has relied on precious metal catalysts supported by strong field ligands to enable highly predictable two-electron redox chemistry that constitutes key bond breaking and forming steps during turnover. Alternative catalysts based on earth abundant transition metals such as iron and cobalt not only offer potential environmental and economic advantages but also provide an opportunity to explore catalysis in a new chemical space. The kinetically and thermodynamically accessible oxidation and spin states may enable new mechanistic pathways, unique substrate scope, or altogether new reactivity. This Account describes my group's efforts over the past decade to develop iron and cobalt catalysts for alkene hydrogenation. Particular emphasis is devoted to the interplay of the electronic structure of the base metal compounds and their catalytic performance. First generation, aryl-substituted pyridine(diimine) iron dinitrogen catalysts exhibited high turnover frequencies at low catalyst loadings and hydrogen pressures for the hydrogenation of unactivated terminal and disubstituted alkenes. Exploration of structure-reactivity relationships established smaller aryl substituents and more electron donating ligands resulted in improved performance. Second generation iron and cobalt catalysts where the imine donors were replaced by N-heterocyclic carbenes resulted in dramatically improved activity and enabled hydrogenation of more challenging unactivated, tri- and tetrasubstituted alkenes. Optimized cobalt catalysts have been discovered that are among the most active homogeneous hydrogenation catalysts known. Synthesis of enantiopure, C1 symmetric pyridine(diimine) cobalt complexes have enabled rare examples of highly enantioselective

  4. Quantum mechanical investigation on the intermediates of alkene-ozone reaction

    International Nuclear Information System (INIS)

    The geometrical parameters, vibrational frequencies, and IR intensities for primary ozonide (POZ), secondary ozonide (SOZ) and carbonyl oxide as the intermediates of alkene-ozone reation have been predicted using high level ab initio quantum mechanical method with various basis sets. In general, the polarization function decreases bond lengths and bond angles, while the electron correlation effect increases bond lengths slightly. The electronic structure of carbonyl oxide has been predicted to be zwitterionic structure and energy difference between zwitterionic and diradical structure is evaluated to be 22.4 kcal/mol at TZ2P CISD level of theory. The experimental vibrational frequencies and IR intensities of POZ and SOZ will be compared and discussed with our high level theoretical predictions

  5. Quantum mechanical investigation on the intermediates of alkene-ozone reaction

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Chang Duk; Kim, Seung Joon [Hannam Univ., Taejon (Korea, Republic of)

    1998-02-01

    The geometrical parameters, vibrational frequencies, and IR intensities for primary ozonide (POZ), secondary ozonide (SOZ) and carbonyl oxide as the intermediates of alkene-ozone reation have been predicted using high level ab initio quantum mechanical method with various basis sets. In general, the polarization function decreases bond lengths and bond angles, while the electron correlation effect increases bond lengths slightly. The electronic structure of carbonyl oxide has been predicted to be zwitterionic structure and energy difference between zwitterionic and diradical structure is evaluated to be 22.4 kcal/mol at TZ2P CISD level of theory. The experimental vibrational frequencies and IR intensities of POZ and SOZ will be compared and discussed with our high level theoretical predictions.

  6. Enantioselective Oxidation of Alkenes with Potassium Permanganate Catalyzed by Chiral Dicationic Bisguanidinium.

    Science.gov (United States)

    Wang, Chao; Zong, Lili; Tan, Choon-Hong

    2015-08-26

    Chiral anion-controlled ion-pairing catalysis was demonstrated to be a wide-ranging strategy that can utilize a variety of cationic metal species. In a similar manner, we envision a complementary strategy using chiral cation in partnership with inorganic anionic metal salts. Herein, we report a chiral dicationic bisguanidinium-catalyzed asymmetric oxidation reaction of alkenes with potassium permanganate. Chiral induction is attributed to ion-pairing interaction between chiral cation and enolate anion. The success of the current permanganate oxidation reaction together with mechanistic insights should provide inspiration for expansion to other anionic metal salts and would open up new paradigms for asymmetric transition metal catalysis, phase-transfer catalysis, and ion-pairing catalysis. PMID:26237178

  7. A combined experimental and theoretical study of the thermal cycloaddition of aryl azides with activated alkenes.

    Science.gov (United States)

    Zeghada, Sarah; Bentabed-Ababsa, Ghenia; Derdour, Aïcha; Abdelmounim, Safer; Domingo, Luis R; Sáez, José A; Roisnel, Thierry; Nassar, Ekhlass; Mongin, Florence

    2011-06-01

    Reactions were performed from aryl azides on the one hand, and activated alkenes coming from β-dicarbonyl compounds or malonodinitrile on the other hand, either with recourse to conventional heating or to microwave activation, to afford 1-aryl-1H-1,2,3-triazoles. The mechanism and the regioselectivity of the reactions involving β-dicarbonyl compounds have been theoretically studied using DFT methods at the B3LYP/6-31G* level: they are domino processes comprising a tautomeric equilibrium of the β-dicarbonyl compounds with their enol forms, a 1,3-dipolar cycloaddition of the enol forms with the aryl azides (high activation energy), and a dehydration process (lower activation energy). The effect of non-conventional activation methods on the degradation of 1,2,3-triazolines was next studied experimentally. Finally, some of the 1,2,3-triazoles such synthesized were evaluated for their bactericidal and cytotoxic activities. PMID:21494704

  8. Progress toward a catalytic alkenation using transition metal alkylidene and oxo complexes

    CERN Document Server

    Broughton, S

    2002-01-01

    We are seeking to develop a new methodology for the synthesis of alkenes. Our desire is to develop an efficient, versatile and highly atom efficient process that offers an environmentally sound and cost effective alternative for the synthetic and industrial chemist to consider over current, well established methodologies. We have conceived a transition metal mediated hypothetical catalytic cycle, the basis of which is a series of ligand interconversions effected by cycloaddition chemistry. This thesis represents a feasibility study into our hypothetical catalytic cycle. Chapter 1 introduces the established methodologies, our hypothetical catalytic cycle and gives a review of the most relevant chemistry. Chapter 2 details our results. Particular attention is paid to relevant concepts in catalysis and transition metal chemistry. Chapter 2.1 reports our experiences in synthesising ketenes. An efficient synthesis of diphenylketene sup 1 sup 3 C sub 2 is described. Our hypothetical catalytic cycle requires a chemo...

  9. Synthesis of selected cage alkenes and their attempted ring-opening metathesis polymerisation with well-defined ruthenium carbene catalysts / Justus Röscher

    OpenAIRE

    Röscher, Justus

    2011-01-01

    In this study a number of cage alkenes were synthesised and tested for activity towards ringopening metathesis polymerisation (ROMP) with the commercially available catalysts 55 (Grubbs-I) and 56 (Grubbs-II). The first group of monomers are derivatives of tetracyclo[6.3.0.04,1105,9]undec-2-en-6-one (1). The synthesis of these cage alkenes are summarised in Scheme 7.1. The cage alkene 126b was synthesised by a Diels-Alder reaction between 1 and hexachlorocyclopentadiene (9, Scheme ...

  10. Size distribution studies in the SOA-particle formation during the ozonolysis of biogenic alkenes

    Science.gov (United States)

    Moortgat, G.; Bonn, B.; Winterhalter, R.

    2003-04-01

    It is established that secondary organic aerosols (SOA) are formed during the reaction of ozone with biogenic alkenes. Experiments of endocyclic (e.g. alpha-pinene, 3-carene) as well as exocyclic monoterpenes (e.g. beta-pinene, sabinene) with ozone have been performed with additional compounds such as water vapour, alcohols and carbonyl compounds, to examine their effect on the SOA particle size distribution in dependence of the alkene structure. This study was further used to describe the formation mechanism of nucleating species for both endo- and exocyclic terpene reactions. Experiments were performed in a spherical glass vessel of 570 L volume at atmospheric pressure. The particle size distribution was measured by a scanning mobility particle sizer, including a long DMA and an ultra-fine particle counter, with a time resolution of two minutes. Cyclohexane was present to prevent interfering reactions of the produced OH-radicals. The laboratory results seem to indicate that the homogeneous nucleation process during the ozonolysis of terpenes is controlled by the formation of large secondary ozonides and can be supressed by the addition of water vapour. These nucleating secondary ozonides are formed differently in endo-and exocyclic reactions: intramolecular in endocyclic and intermolecular in exocylic monoterpene ozonolyses. Such processes are known to be controlled by the stabilized Criegee Intermediates (CI), formed in the ozone reaction with biogenic terpenes. On the other hand, analysis of aerosol material from laboratory and some sparse field studies have identifed various multifunctional dicarboxylic, and keto-carboxylic acids (e.g. pinic and pinonic acid), whose current formation mechanism seems to involve excited CI. Due to their low volatility, these acids may act as nucleation precursors (new particle formation) or condense on preexisting particles (heterogeneous nucleation). The current dilemma, whether stabilized or excited CI are involved in the

  11. Katalýza radikálové polymerace jednoduchých alkenů lithiovými kationty

    Czech Academy of Sciences Publication Activity Database

    Michl, Josef

    2008-01-01

    Roč. 102, č. 10 (2008), s. 873-879. ISSN 0009-2770 Institutional research plan: CEZ:AV0Z40550506 Keywords : catalysis * polymerization * alkenes Subject RIV: CC - Organic Chemistry Impact factor: 0.593, year: 2008

  12. Rapid Access to β-Trifluoromethyl-Substituted Ketones: Harnessing Inductive Effects in Wacker-Type Oxidations of Internal Alkenes

    KAUST Repository

    Lerch, Michael M.

    2014-07-18

    We present a practical trifluoromethyl-directed Wacker-type oxidation of internal alkenes that enables rapid access to β-trifluoromethyl-substituted ketones. Allylic trifluoromethyl-substituted alkenes bearing a wide range of functional groups can be oxidized in high yield and regioselectivity. The distance dependence of the regioselectivity was established by systematic variation of the number of methylene units between the double bond and the trifluoromethyl group. The regioselectivity enforced by traditional directing groups could even be reversed by introduction of a competing trifluoromethyl group. Besides being a new powerful synthetic method to prepare fluorinated molecules, this work directly probes the role of inductive effects on nucleopalladation events. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Stereocontrolled Synthesis of Vinyl Boronates and Vinyl Silanes via Atom-Economical Ruthenium-Catalyzed Alkene-Alkyne Coupling.

    Science.gov (United States)

    Trost, Barry M; Koester, Dennis C; Herron, Alastair N

    2015-12-21

    The synthesis of vinyl boronates and vinyl silanes was achieved by employing a Ru-catalyzed alkene-alkyne coupling reaction of allyl boronates or allyl silanes with various alkynes. The double bond geometry in the generated vinyl boronates can be remotely controlled by the juxtaposing boron- and silicon groups on the alkyne substrate. The synthetic utility of the coupling products has been demonstrated in a variety of synthetic transformations, including iterative cross-coupling reactions, and a Chan-Lam-type allyloxylation followed by a Claisen rearrangement. A sequential one-pot alkene-alkyne-coupling/allylation-sequence with an aldehyde to deliver a highly complex α-silyl-β-hydroxy olefin with a handle for further functionalization was also realized. PMID:26572804

  14. Hydrocarbon activation by gas-phase lanthanide cations: interaction of Pr+, Eu+, and Gd+ with small alkanes, cycloalkanes, and alkenes

    International Nuclear Information System (INIS)

    The authors describe ion beam studies of the interaction of gas-phase lanthanide ions, praseodymium (Pr+), europium (Eu+), and gadolinium (Gd+), with small alkanes, cycloalkanes, alkenes, and several oxygen-containing compounds. Only Gd+ is seen to activate C-H and C-C bonds of alkanes. The ground state electronic configuration of Gd+ (4f75d16s1) is different from those of Pr+ (4f36s1) and Eu+ (4f76s1), leading to the conclusion that the f electrons play little part in the metal ion reactivity. Gd+ can be thought of as having two valence electrons, and indeed it reacts similarly to Sc+ and the other group 3 metal ions Y+ and La+, yielding products corresponding to elimination of hydrogen, alkanes, and alkenes. The elimination of neutral alkenes in the reaction of Gd+ with alkanes results in the formation of metal dialkyl or hydrido-alkyl complexes. This finding leads to estimates for the sum of two Gd+ σ bond dissociation energies of between 110 and 130 kcal/mol. Gd+ and Pr+ react readily with alkenes, yielding mostly dehydrogenation products along with smaller amounts of C-C bond cleavage products. Reactions of Gd+ and Pr+ with oxygen-containing species such as nitric oxide, formaldehyde, acetaldehyde, and acetone yield primarily the metal oxide ions and provide a lower limit for D(M+-O) of 179 kcal/mol, in good agreement with literature values of D(Pr+-O) = 188.4 +/- 5.2 kcal/mol and D(Gd+-0) = 181.0 +/- 4.4 kcal/mol. In keeping with the strong metal σ bonds, Gd+ is also seen to readily react with formaldehyde to eliminate CO and form GdH2+

  15. Alkene and Diene Complexes with [(C5Me4CnF2n+1)Rh] Fragment

    Czech Academy of Sciences Publication Activity Database

    Čermák, Jan; Strašák, Tomáš; Krupková, Alena; Auerová, Kateřina

    Praha : Česká společnost chemická, 2008, s. 1029-1030. ISSN 0009-2770. [Pokroky v organické, bioorganické a farmaceutické chemii /43./. Liblice (CZ), 14.11.2008-16.11.2008] R&D Projects: GA MŠk(CZ) LC06070 Institutional research plan: CEZ:AV0Z40720504 Keywords : alkene complexes * fluorous cyclopentadienes * rhodium complexes Subject RIV: CC - Organic Chemistry

  16. The different roles of a cationic gold(i) complex in catalysing hydroarylation of alkynes and alkenes with a heterocycle.

    Science.gov (United States)

    Mehrabi, Tahmineh; Ariafard, Alireza

    2016-08-01

    The mechanism of twofold hydroarylation of terminal alkynes with pyrrole catalyzed by a cationic gold(i) complex was investigated using DFT. It was found that while both the hydroarylation reactions proceed via a Friedel-Crafts-type mechanism, the first hydroarylation is directly promoted by gold(i) but the second hydroarylation by a proton released through interaction of the alkene product with gold-bound acidic organic species such as acetic acid and terminal alkynes. PMID:27377712

  17. Observations and comments on the mechanism of epoxidation of alkenes by manganese(III) porphyrins with hypochlorite.

    OpenAIRE

    Lee, R W; Nakagaki, P C; Balasubramanian, P N; Bruice, T C

    1988-01-01

    The kinetics of olefin epoxidation in a methylene chloride/water biphase containing a phase-transfer agent with hypochlorite as oxygen transfer reagent and manganese(III) tetraphenylporphyrin catalysts has been reinvestigated. The results do not support the accumulation of an intermediate composed of an alkene and a hypervalent metaloxo porphyrin. Second-order rate constants for oxygen transfer from hypochlorite to the manganese porphyrin, comproprotionation of the hypervalent manganese-oxo p...

  18. Gas-phase chemistry of curium: Reactions of Cm+ and CmO+ with alkenes, acetonitrile, and hexafluoropropene

    International Nuclear Information System (INIS)

    The metal ions, Cm+, U+, and Tb+, and their oxides, MO+, were reacted in the gas phase with alkenes, acetonitrile, and hexafluoropropene, Product compositions and abundances provide a survey of essential aspects of the gas-phase chemistry of the curium cation, now the heaviest element for which such systematic studies have been carried out (U and Tb were included to provide comparisons). Of particular interest is the difference in behavior between the 4f lanthanide and 5f actinide series and variations in chemistry across the actinide series. The primary emphasis was on reactions with alkenes, particularly dehydrogenation, as indicative of the ability of a M+ to activate C-H bonds (the extent of C-C activation was generally in parallel with that of C-H activation). With acetonitrile and all of the alkenes (except ethene), the three M+ ions induced dehydrogenation. Variations were evident for the different reactant substrates, but the overall qualitative ordering of dehydrogenation efficiency was U+ > Tb+ > Cm+. With hexafluoropropene, the primary reaction channel was F abstraction and the discrepant reactivities reflected the propensity for U to oxidize to higher valence states compared to Cm or Tb. The terminal MFn+ were CmIIIF2+, TbIIIF2+, and UIVF4+, and among the MO+, only UO+ induced F abstraction, producing UOFn+ with n = 1--3

  19. Thermodynamics of adsorption of light alkanes and alkenes in single-walled carbon nanotube bundles

    CERN Document Server

    Cruz, Fernando J A L

    2016-01-01

    The thermodynamics of adsorption of light alkanes and alkenes (CH4, C2H6, C2H4, C3H8, and C3H6) in single-walled carbon nanotube bundles is studied by configurational-bias grand canonical Monte Carlo simulation. The bundles consist of uniform nanotubes with diameters in the range 11.0 < D (A) < 18.1, arranged in the usual close-packed hexagonal lattice. The phase space is systematically analyzed with calculations for adsorption at room temperature and reduced pressure range of 8.7 x 10-9 < (p/p0) < 0.9. The simulation results are interpreted in terms of the molecular nature of the adsorbate and the corresponding solid-fluid interactions. It is shown that confinement in the internal volume of the bundle (interstitial and intratubular) is energetically more favorable than physisorption on the external surface (grooves and exposed surfaces of peripheral tubes), as indicated by the curves of isosteric heat as a function of reduced pressure. However, the zero-loading properties suggest a crossover poin...

  20. Ozonolysis of cyclic alkenes as surrogates for biogenic terpenes: primary ozonide formation and decomposition.

    Science.gov (United States)

    Epstein, Scott A; Donahue, Neil M

    2010-07-22

    Alkene ozonolysis reactions proceed through an unstable intermediate, the primary ozonide (POZ). POZ decomposition controls the complex mechanism. We probe the kinetics of primary ozonide decomposition using temperature programmed reaction spectroscopy (TPRS), revealing primary ozonide decomposition barrier heights of 9.1 +/- 0.4, 9.4 +/- 0.4, and 11.9 +/- 1.2 kcal mol(-1) for cyclohexene, 1-methyl-cyclohexene, and methylene-cyclohexane, respectively. We compare experimental decomposition spectra with spectral predictions using density functional theory (DFT) to reveal decomposition products resembling vinyl-hydroperoxides and dioxiranes. We do not find evidence of secondary ozonides. Additional computations with DFT, scaled with the TPRS barrier height, yield barrier heights ranging from 9.4 to 12.1 kcal mol(-1) for the four competing decomposition pathways of the 1-methyl-cyclohexene POZ. Entropic differences were minimal, indicating that POZ decomposition branching is controlled purely by enthalpic variations. These kinetic computations were used to calculate a hydroxyl radical yield for 1-methyl-cyclohexene ozonolysis of 0.85 at 298 K. PMID:20578707

  1. Secondary ozonides of endo-cyclic alkenes analyzed by atmospheric sampling Townsend discharge ionization mass spectrometry

    Science.gov (United States)

    Nøjgaard, J. K.; Nørgaard, A. W.; Wolkoff, P.

    2007-05-01

    Secondary ozonides (SOZ) of cyclohexene, 1-methylcyclohexene, 4-isopropyl-1-methylcyclohexene and d-limonene were cryo-synthesized by ozonolysis in pentane and purified on a silica gel column. The mass spectra obtained by atmospheric sampling Townsend discharge ionization (ASTDI) and collision activated dissociation (CAD) of the protonized SOZ showed characteristic losses evident of the ozonide structure. Oxygen was eliminated as, e.g., O and O2, and loss of (HCHO + HCHO) or (O + CO2) corresponded to the SOZ base-peak for the substituted cyclohexenes by ASTDI-MS. The CAD spectra of the protonized species by use of methane as chemical ionization gas, showed consecutive losses of three oxygen atoms. Elimination of hydroxy-methyl hydroperoxide (HMHP) was particular important for the protonized SOZ, unlike consecutive loss of (HCHO + HCHO) or (O + CO2). In addition, the spectra of d-limonene were characterized by an unique loss of H2O2. These losses appear to be useful for identification of SOZ in gas-phase ozonolysis mixtures of endo-cyclic alkenes, which makes ASTDI an alternative to other on-line techniques for analysis of SOZ in ozonolysis mixtures.

  2. Conformational Analysis of 1-ALKENE Secondary Ozonides by Means of Matrix Isolation FTIR Spectroscopy

    Science.gov (United States)

    Sablinskas, Valdas; Strazdaite, Simona; Ceponkus, Justinas

    2009-06-01

    An ability of ozone to break double C=C bond in olefins is known for more than five decades. Understanding of those reactions is very important in atmospheric chemistry. During different steps of the reaction the primary ozonide (POZ), carbonyl oxide (COX) and the secondary ozonide (SOZ) are formed. Fate of the reaction depends on many parameters such as type of radical, conformation of alkene, temperature of the reaction and environmental effects. Despite of numerous studies of the reaction by different spectroscopic techniques the precise mechanism of the reaction is still unknown. It is experimentally observed that the SOZ is more stable than POZ. Stability of the SOZ depends on the size and configuration of the radical. Unfortunately, it is not much known about the spatial structures of the SOZ'es. The aim of this study is to define the geometrical structures and stability of the different conformers of the 1-butene and 1-heptene secondary ozonides by combined analysis of the matrix isolation FTIR spectral data with the results of Density Functional Theory (DFT) calculations.

  3. Alkene ozonolysis SOA: inferences of composition and droplet growth kinetics from Köhler theory analysis

    Directory of Open Access Journals (Sweden)

    A. Asa-Awuku

    2007-06-01

    Full Text Available The CCN properties, surfactant characteristics, and droplet growth kinetics of secondary organic aerosol (SOA formed from the ozonolysis of three parent alkene hydrocarbons (terpinolene, 1-methlycycloheptene and cycloheptene are explored. Based on measurements of CCN activity, total carbon and inorganic ion concentrations, we estimate the average molar volume of the water-soluble organic component using Köhler Theory Analysis (KTA. The results suggest that the water-soluble organics in the SOA are composed of relatively low molecular weight species, with an effective molar mass less than 200 g mol−1. This finding is consistent with the speciated fraction for some of the SOA, and suggests that KTA can be applied to complex organic aerosol, such as that found in the atmosphere. From measurements of CCN activity and Köhler Theory, we apply a novel method to infer the surface tension at the point of activation; this is used to infer the presence of surface-active organics. It is found that the water-soluble carbon can be surface-active, depressing surface tension 10–15% from that of pure water at concentrations relevant for CCN activation. Although important, this level of surface tension depression is lower than expected for HULIS, which suggest that they are not likely in the SOA examined. In all cases, the CCN exhibit droplet growth kinetics similar to (NH42SO4.

  4. Progress toward a catalytic alkenation using transition metal alkylidene and oxo complexes

    International Nuclear Information System (INIS)

    We are seeking to develop a new methodology for the synthesis of alkenes. Our desire is to develop an efficient, versatile and highly atom efficient process that offers an environmentally sound and cost effective alternative for the synthetic and industrial chemist to consider over current, well established methodologies. We have conceived a transition metal mediated hypothetical catalytic cycle, the basis of which is a series of ligand interconversions effected by cycloaddition chemistry. This thesis represents a feasibility study into our hypothetical catalytic cycle. Chapter 1 introduces the established methodologies, our hypothetical catalytic cycle and gives a review of the most relevant chemistry. Chapter 2 details our results. Particular attention is paid to relevant concepts in catalysis and transition metal chemistry. Chapter 2.1 reports our experiences in synthesising ketenes. An efficient synthesis of diphenylketene 13C2 is described. Our hypothetical catalytic cycle requires a chemoselective reaction and Chapter 2.2 describes our preliminary work investigating the feasibility of this. Chapter 2.3 describes the synthesis of [PPN][Cp*MO3] (M=Mo, W) and Chapter 2.4 describes the reactivity of these complexes with ketenes and provides a unique experimental insight into the stepwise cycloaddition mechanism of diphenylketene with [PPN][Cp*WO3). Chapter 2.5 describes the reactivity of mono oxo complexes with ketenes and Chapter 2.6 describes the synthesis and reactivity of stereoelectronically activated dioxo complexes. A formal account of all experimental procedures is presented. (author)

  5. Terminal Alkene Formation by the Thioesterase of Curacin A Biosynthesis: Structure of a Decarboxylating Thioesterase

    Energy Technology Data Exchange (ETDEWEB)

    Gehret, Jennifer J.; Gu, Liangcai; Gerwick, William H.; Wipf, Peter; Sherman, David H.; Smith, Janet L. (Pitt); (Michigan); (UCSD)

    2011-11-07

    Curacin A is a polyketide synthase (PKS)-non-ribosomal peptide synthetase-derived natural product with potent anticancer properties generated by the marine cyanobacterium Lyngbya majuscula. Type I modular PKS assembly lines typically employ a thioesterase (TE) domain to off-load carboxylic acid or macrolactone products from an adjacent acyl carrier protein (ACP) domain. In a striking departure from this scheme the curacin A PKS employs tandem sulfotransferase and TE domains to form a terminal alkene moiety. Sulfotransferase sulfonation of {beta}-hydroxy-acyl-ACP is followed by TE hydrolysis, decarboxylation, and sulfate elimination (Gu, L., Wang, B., Kulkarni, A., Gehret, J. J., Lloyd, K. R., Gerwick, L., Gerwick, W. H., Wipf, P., Hakansson, K., Smith, J. L., and Sherman, D. H. (2009) J. Am. Chem. Soc. 131, 16033-16035). With low sequence identity to other PKS TEs (<15%), the curacin TE represents a new thioesterase subfamily. The 1.7-{angstrom} curacin TE crystal structure reveals how the familiar {alpha}/{beta}-hydrolase architecture is adapted to specificity for {beta}-sulfated substrates. A Ser-His-Glu catalytic triad is centered in an open active site cleft between the core domain and a lid subdomain. Unlike TEs from other PKSs, the lid is fixed in an open conformation on one side by dimer contacts of a protruding helix and on the other side by an arginine anchor from the lid into the core. Adjacent to the catalytic triad, another arginine residue is positioned to recognize the substrate {beta}-sulfate group. The essential features of the curacin TE are conserved in sequences of five other putative bacterial ACP-ST-TE tridomains. Formation of a sulfate leaving group as a biosynthetic strategy to facilitate acyl chain decarboxylation is of potential value as a route to hydrocarbon biofuels.

  6. EtAlCl2/2,6-Disubstituted Pyridine-Mediated Carboxylation of Alkenes with Carbon Dioxide.

    Science.gov (United States)

    Tanaka, Shinya; Watanabe, Kota; Tanaka, Yuuki; Hattori, Tetsutaro

    2016-06-01

    α-Arylalkenes and trialkyl-substituted alkenes undergo carboxylation with CO2 in the presence of EtAlCl2 and 2,6-dibromopyridine to afford the corresponding α,β- and/or β,γ-unsaturated carboxylic acids. This reaction is suggested to proceed via the electrophilic substitution of EtAlCl2 with the aid of the base, followed by the carbonation of the resulting ate complex. This reaction can be applied to terminal dialkylalkenes by using a mixture of 2,6-di-tert-butylpyridine and 2,6-dibromopyridine. PMID:27187716

  7. Room Temperature Activation of Aryloxysulfonyl Azides by [Co(II)(TPP)] for Selective Radical Aziridination of Alkenes via Metalloradical Catalysis

    Science.gov (United States)

    Subbarayan, Velusamy; Jin, Li-Mei; Xin, Cui; Zhang, X. Peter

    2015-01-01

    Aryloxysulfonyl azides can be effectively activated by commercially available cobalt(II) complex of meso-tetraphenylporphyrin ([Co(TPP)]) at room temperature under neutral and nonoxidative conditions for selective radical aziridination of alkenes via metalloradical catalysis. The [Co(TPP)]-catalyzed radical aziridination system is suitable for different combinations of olefin substrates and aryloxysulfonyl azides, producing various N-aryloxysulfonyl aziridine derivatives in good to excellent yields. In addition to generating the environmentally benign N2 as the only byproduct, this Co(II)-based metalloradical aziridination process features mild reaction conditions and operational simplicity. PMID:26139944

  8. Regioselective vicinal functionalization of unactivated alkenes with sulfonium iodate(i) reagents under metal-free conditions.

    Science.gov (United States)

    Rao, Dodla S; Reddy, Thurpu R; Babachary, Kalvacherla; Kashyap, Sudhir

    2016-08-21

    Metal-free, molecular iodine-free direct 1,2-difunctionalization of unactivated alkenes has been reported. The sulfonium iodate(i) reagent efficiently promoted the intermolecular vicinal iodo-functionalization of a diverse range of olefins in a stereo and regioselective manner. This method enables the divergent and straightforward preparation of synthetically useful functionalities; β-iodocarboxylates, β-iodohydrins, and β-iodoethers in a one-step process. Further interconversion of iodo-functionalized derivatives allows easy access to valuable synthetic intermediates en route to biologically active molecules. PMID:27430994

  9. Pd-Catalyzed Regioselective Alkoxycarbonylation of 1-Alkenes Using a Lewis Acid [SnCl2 or Ti(O(i)Pr)4] and a Phosphine.

    Science.gov (United States)

    Amézquita-Valencia, Manuel; Achonduh, George; Alper, Howard

    2015-06-19

    The phosphine ligand mediated palladium catalyzed alkoxycarbonylation of alkenes was investigated with the objective of attaining good linear selectivity for the ester. The effect of various parameters such as solvents, additives, palladium precursors, CO pressures, and alkenes of various structural complexities were examined. The results revealed the importance of using a Lewis acid such as SnCl2 or Ti(O(i)Pr)4 in combination with a monodentate ligand such CYTOP 292 or P(p-anisyl)3 to enhance the regioselectivity for the linear isomers in the range of 70-96%. PMID:26005796

  10. Synthesis of N-Aryl-2-allyl Pyrrolidines via Palladium-catalyzed Carboamination Reactions of γ-(N-Arylamino)alkenes with Vinyl Bromides

    OpenAIRE

    Ney, Joshua E.; Hay, Michael B.; Yang, Qifei; Wolfe, John P.

    2005-01-01

    A palladium-catalyzed carboamination reaction of γ-N-arylamino alkenes with vinyl bromides that affords N-aryl-2-allyl pyrrolidines is described. These reactions proceed with high diastereoselectivity for the formation of trans-2,3- and cis-2,5-disubstituted pyrrolidines. Conditions for a tandem N-arylation/carboamination sequence that leads to the formation of an N-aryl-2-allyl pyrrolidine or indoline via the coupling of a primary γ-amino alkene, an aryl bromide, and a vinyl bromide are also...

  11. Cobalt salophen complex supported on imidazole functionalized magnetic nanoparticles as a recoverable catalyst for oxidation of alkenes

    Energy Technology Data Exchange (ETDEWEB)

    Afshari, Mozhgan, E-mail: m.afshari@iau-shoushtar.ac.ir [Department of Chemistry, Shoushtar Branch, Islamic Azad University, Shoushtar (Iran, Islamic Republic of); Gorjizadeh, Maryam [Department of Chemistry, Shoushtar Branch, Islamic Azad University, Shoushtar (Iran, Islamic Republic of); Nazari, Simin [Department of Chemistry, Sousangerd Branch, Islamic Azad University, Sousangerd (Iran, Islamic Republic of); Naseh, Mohammad [Department of Chemistry, Dezful Branch, Islamic Azad University, Dezful (Iran, Islamic Republic of)

    2014-08-01

    A new magnetically separable catalyst consisting of Co(II) salophen complex covalently supported on imidazole functionalized silica coated cobalt ferrite was prepared. The synthesized catalyst was characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA), inductively coupled plasma atomic emission spectroscopy (ICP-AES) and Fourier transform infrared (FT-IR). The immobilized catalyst was shown to be an efficient heterogeneous catalyst for the oxidation of some alkenes using hydrogen peroxide (H{sub 2}O{sub 2}) as oxidant. The catalyst could be easily and efficiently isolated from the final product solution by magnetic decantation and be reused for 5 consecutive reactions without showing any significant activity degradation. - Highlights: • A new magnetic catalyst consisting of Co(II) salophen complex was prepared. • The catalyst was shown to be an efficient catalyst for the oxidation of alkenes. • The catalyst could be easily isolated from the product by magnetic decantation. • The catalyst is reused 5 times without a significant loss of activity.

  12. Size-Dependent Catalytic Activity of Palladium Nanoparticles Fabricated in Porous Organic Polymers for Alkene Hydrogenation at Room Temperature.

    Science.gov (United States)

    Mondal, John; Trinh, Quang Thang; Jana, Avijit; Ng, Wilson Kwok Hung; Borah, Parijat; Hirao, Hajime; Zhao, Yanli

    2016-06-22

    Ultrafine palladium nanoparticles (Pd NPs) with 8 and 3 nm sizes were effectively fabricated in triazine functionalized porous organic polymer (POP) TRIA that was developed by nonaqueous polymerization of 2,4,6-triallyoxy-1,3,5-triazine. The Pd NPs encapsulated POP (Pd-POP) was fully characterized using several techniques. Further studies revealed an excellent capability of Pd-POP for catalytic transfer hydrogenation of alkenes at room temperature with superior catalytic performance and high selectivity of desired products. Highly flammable H2 gas balloon at high pressure and temperature used in conventional hydrogenation reactions was not needed in the present synthetic system. Catalytic activity is strongly dependent on the size of encapsulated Pd NPs in the POP. The Pd-POP catalyst with Pd NPs of 8 nm in diameter exhibited higher catalytic activity for alkene hydrogenation as compared with the Pd-POP catalyst encapsulating 3 nm Pd NPs. Computational studies were undertaken to gain insights into different catalytic activities of these two Pd-POP catalysts. High reusability and stability as well as no Pd leaching of these Pd-POP catalysts make them highly applicable for hydrogenation reactions at room temperature. PMID:27258184

  13. Total synthesis of gracilioether F. Development and application of Lewis acid promoted ketene–alkene [2+2] cycloadditions and late-stage C—H oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Rasik, Christopher M. [Indiana Univ., Bloomington, IN (United States); Brown, M. Kevin [Indiana Univ., Bloomington, IN (United States)

    2014-12-22

    The first synthesis of gracilioether F, a polyketide natural product with an unusual tricyclic core and five contiguous stereocenters, is described. Key steps of the synthesis include a Lewis acid promoted ketene–alkene [2+2] cycloaddition and a late-stage carboxylic acid directed C(sp³)—H oxidation. The synthesis requires only eight steps from norbornadiene.

  14. Quantitative determination of triperpene saponins and alkenated-phenolics from Labisia pumila using LC-UV/ELSD method and confirmation by LC-ESI-TOF

    Science.gov (United States)

    This study describes the first analytical method for the determination of saponins and alkenated-phenolics from the leaves, leaves/stems and roots of Labisia pumila using a HPLC-UV-ELSD method. The separation was achieved using a reversed phase column, PDA and ELS detection, and a water/acetonitrile...

  15. Quantitative determination of triterpene saponins and alkenated-phenolics from Labisia pumila using LC-UV/ELSD method and confirmation by LC-ESI-TOF

    Science.gov (United States)

    This study describes the first analytical method for the determination of saponins and alkenated-phenolics from the leaves, leaves/stems and roots of Labisia pumila using a HPLC-UV-ELSD method. The separation was achieved using a reversed phase column, PDA and ELS detection, and a water/acetonitrile...

  16. Asymmetric Baylis-Hillman Reaction between Chiral Activated Alkenes and Aromatic Aldehydes in Me3N/H2O/Solvent Medium

    Institute of Scientific and Technical Information of China (English)

    Ke HE; Zheng Hong ZHOU; Hong Ying TANG; Guo Feng ZHAO; Chu Chi TANG

    2005-01-01

    Chiral activated alkene, L-menthyl acrylate and (+)-N-α-phenylethyl acrylamide,induced asymmetric Baylis-Hillman reaction of aromatic aldehydes was realized at 25℃ for 7 days in Me3N/H2O/solvent homogeneous medium. The corresponding Baylis-Hillman adducts were obtained in good chemical yield with moderate to excellent diastereoselectivity (up to 99% de).

  17. Alkene and Diene Complexes with [(C5Me4CnF2n+1)Rh] Fragment for Fluorous Biphase Catalysis

    Czech Academy of Sciences Publication Activity Database

    Čermák, Jan; Strašák, Tomáš; Krupková, Alena; Auerová, Kateřina

    -: -, 2008 - (Baxter, D.; Bay, B.), P 274 ISBN N. [16th International Symposium on Homogeneous Catalysis , ISHC-XVI. Florence (IT), 06.07.2008-11.07.2008] R&D Projects: GA MŠk(CZ) LC06070 Institutional research plan: CEZ:AV0Z40720504 Keywords : rhodium complexes * fluorous cyclopentadienes * alkene complexes Subject RIV: CC - Organic Chemistry

  18. A new series of two-photon blue/violet fluorescent trans-alkenes: Green synthesis and optical properties

    Science.gov (United States)

    Huang, Jiu-Qiang; Cai, Zhi-Bin; Jin, Fan; Li, Sheng-Li; Tian, Yu-Peng

    2016-02-01

    A new series of trans-alkenes (3a-3e) containing different electron-donating groups were synthesized by the solvent-free Horner-Wadsworth-Emmons reaction, and characterized by infrared, hydrogen nuclear magnetic resonance, mass spectrometry and elemental analysis. Their UV-visible absorption, one-photon excited fluorescence, two-photon absorption, and two-photon excited fluorescence were systematically investigated in different solvents. Experimental results show different trends in linear and nonlinear optical properties with different donor units. 3a with triphenylamine donor exhibits the best optical properties. It emits strong blue up-converted fluorescence, and the two-photon absorption cross-section can be as large as 218 GM in DCM.

  19. An operationally simple approach to (E)-α-halo vinyl sulfides and their applications for accessing stereodefined trisubstituted alkenes.

    Science.gov (United States)

    Yang, Zhaozhen; Chen, Xiaoyi; Kong, Wei; Xia, Siyuan; Zheng, Renwei; Luo, Fang; Zhu, Gangguo

    2013-04-01

    An operationally simple and practical protocol for the synthesis of (E)-α-halo vinyl sulfides has been achieved via a highly regio- and stereoselective hydrohalogenation of alkynyl thioethers using lithium halides in HOAc or propionic acid at room temperature. It permits the formation of (E)-α-chloro and (E)-α-bromo vinyl sulfides in satisfactory yields with good to excellent stereoselectivities. Moreover, this work results in a new method for the assembly of stereodefined (E)- or (Z)-trisubstituted alkenes featuring the first coupling of the C-X bond of (E)-α-halo vinyl sulfides followed by a subsequent Ni-catalyzed coupling of the C-S bond with Grignard reagents. PMID:23403773

  20. Chain propagation and termination mechanisms for polymerization of conjugated polar alkenes by [Al]-based frustrated Lewis pairs

    KAUST Repository

    He, Jianghua

    2014-11-25

    A combined experimental and theoretical study on mechanistic aspects of polymerization of conjugated polar alkenes by frustrated Lewis pairs (FLPs) based on N-heterocyclic carbene (NHC) and Al(C6F5)3 pairs is reported. This study consists of three key parts: structural characterization of active propagating intermediates, propagation kinetics, and chain-termination pathways. Zwitterionic intermediates that simulate the active propagating species in such polymerization have been generated or isolated from the FLP activation of monomers such as 2-vinylpyridine and 2-isopropenyl-2-oxazoline-one of which, IMes+-CH2C(Me)=(C3H2NO)Al(C6F5)3 - (2), has been structurally characterized. Kinetics performed on the polymerization of 2-vinylpyridine by ItBu/Al(C6F5)3 revealed that the polymerization follows a zero-order dependence on monomer concentration and a first-order dependence on initiator (ItBu) and activator [Al(C6F5)3] concentrations, indicating a bimolecular, activated monomer propagation mechanism. The Lewis pair polymerization of conjugate polar alkenes such as methacrylates is accompanied by competing chain-termination side reactions; between the two possible chain-termination pathways, the one that proceeds via intramolecular backbiting cyclization involving nucleophilic attack of the activated ester group of the growing polymer chain by the O-ester enolate active chain end to generate a six-membered lactone (δ-valerolactone)-terminated polymer chain is kinetically favored, but thermodynamically disfavored, over the pathway leading to the -ketoester-terminated chain, as revealed by computational studies.

  1. Oxidation of Alkenes with H2O2 by an in-Situ Prepared Mn(II)/Pyridine-2-carboxylic Acid Catalyst and the Role of Ketones in Activating H2O2

    NARCIS (Netherlands)

    Dong, Jia Jia; Saisaha, Pattama; Meinds, Tim G.; Alsters, Paul L.; Ijpeij, Edwin G.; van Summeren, Ruben P.; Mao, Bin; Fananas-Mastral, Martin; de Boer, Johannes W.; Hage, Ronald; Feringa, Ben L.; Browne, Wesley R.

    2012-01-01

    A simple, high yielding catalytic method for the multigram scale selective epoxidation of electron-rich alkenes using near-stoichiometric H2O2 under ambient conditions is reported. The system consists of a Mn(II) salt (

  2. Green oxidation of alkenes in ionic liquid solvent by hydrogen peroxide over high performance Fe(III) Schiff base complexes immobilized on MCM-41

    Indian Academy of Sciences (India)

    Mohammad Taghi Goldani; Ali Mohammadi; Reza Sandaroos

    2014-05-01

    A series of Fe(III) Schiff base complexes immobilized on MCM-41 were prepared and characterized by various physicochemical and spectroscopic methods. The complexes were used for oxidation of cyclohexene by 30% hydrogen peroxide in the presence and absence of ethylmethyl imidazolium chloride (EMIM) ionic liquid as solvent. The immobilized complexes proved to be effective catalysts and generally exhibited much higher catalytic performance than their homogeneous analogue. Catalytic performance of the complexes was also found to be closely related to the Schiff base ligands used. Additionally, ion liquid solvent efficiently improved all the catalytic performances. Finally, the reaction was extended to different alkenes using the heterogeneous complex 2-L4. Among all the alkenes, those containing -electron-withdrawing groups and trans-orientations exhibited lower tendency for oxidation.

  3. Polystyrene-supported triphenylarsines: Useful ligands in palladium-catalyzed aryl halide homocoupling reactions and a catalyst for alkene epoxidation using hydrogen peroxide

    OpenAIRE

    Song He, H; Zhang, C; Ng, CKW; Toy, PH

    2005-01-01

    The utility of both soluble (non-cross-linked) and insoluble (cross-linked) polystyrene-supported triphenylarsine reagents were examined. These reagents were prepared by standard radical polymerization methodology and used in palladium-catalyzed homocoupling reactions of aryl halides. The insoluble reagent was also used as a catalyst precursor in heterogeneous alkene epoxidation reactions in which aqueous hydrogen peroxide was the stoichiometric oxidant. For the aryl halide homocoupling react...

  4. Construction of Pd(II)-poly(4-vinylpyridine) multilayers on quartz substrate surface as heterogeneous catalyst for selective hydrogenation of aromatic conjugated alkenes

    International Nuclear Information System (INIS)

    Research highlights: → Pd-PVP multilayers were prepared by layer-by-layer method. → Immobilized Pd-PVP multilayers acted as heterogeneous catalyst. → Hydrogen used as a reductant for the connectors of Pd(II) ions as well as hydrogen source for the hydrogenation reactions of alkenes. → The heterogeneous catalyst had advantages of high stability, good recyclability and easy separation. - Abstract: Palladium-mediated layer-by-layer (LBL) multilayers with poly(4-vinylpyridine) (PVP) as linker have been constructed on quartz substrate surface and characterized by using UV-Vis absorption spectra, attenuated total reflection infrared spectra, X-ray photoelectron spectra as well as scanning electron microscopy. The as-prepared Pd-PVP multilayers modified substrate was used as heterogeneous catalyst for selectively catalytic hydrogenation of aromatic conjugated alkenes at room temperature. Hydrogen gas was used as a reductant for the connectors of Pd(II) ions as well as hydrogen source for the hydrogenation reactions of alkenes. X-ray photoelectron spectra revealed that the connectors of Pd(II) ions could be reduced to Pd(0) atoms by hydrogen saturated aqueous solution. Yields of the hydrogenation reaction were closely related to the nature of aromatic conjugated alkenes. Because the Pd(0) atoms were encapsulated in the matrix of Pd-PVP multilayers and immobilized on the quartz surface, the present Pd-PVP heterogeneous catalysts had the advantages of high stability, good recyclability as well as the advantage of monitoring the catalytic reaction process through immersing in or withdrawing the modified substrate from the reaction solutions.

  5. Facial Synthesis of o-Carborane-Substituted Alkenes and Allenes by a Regioselective Ene Reaction of 1,3-Dehydro-o-carborane.

    Science.gov (United States)

    Zhao, Da; Zhang, Jiji; Xie, Zuowei

    2015-07-13

    1,3-Dehydro-o-carborane is a useful synthon for selective cage boron functionalization of o-carboranes. It reacts readily with alkenes or alkynes to give a variety of cage B(3)-alkenyl/allenyl o-carboranes by ene reactions in very high yields and excellent regioselectivity. This can be ascribed to the highly polarized cage C-B multiple bond, which lowers the activation barriers of the ene reaction. PMID:26074122

  6. Highly efficient asymmetric epoxidation of alkenes with a D(4)-symmetric chiral dichlororuthenium(IV) porphyrin catalyst.

    Science.gov (United States)

    Zhang, R; Yu, W Y; Wong, K Y; Che, C M

    2001-11-30

    A dichlororuthenium(IV) complex of 5,10,15,20-tetrakis[(1S,4R,5R,8S)-1,2,3,4,5,6,7,8-octahydro-1,2:5,8-dimethanoanthrance-9-yl]porphyrin, [Ru(IV)(D(4)-Por)Cl(2)] (1), was prepared by heating [Ru(II)(D(4)-Por)(CO)(MeOH)] (2) in refluxing CCl(4). Complex 1 is characterized by (1)H NMR (paramagnetically shifted pyrrolic protons at delta(H) = -52.3 ppm), FAB-mass spectroscopies, and magnetic susceptibility measurement (mu(eff) = 3.1 mu(B)). The ruthenium complex exhibits remarkable catalytic activity toward enantioselective alkene epoxidation using 2,6-dichloropyridine N-oxide (Cl(2)pyNO) as terminal oxidant. The Ru(IV)-catalyzed styrene epoxidation is achieved within 2 h (versus 48 h for the 2-catalyzed reaction), and optically active styrene oxide was obtained in 69% ee and 84% yield (875 turnovers). Likewise, substituted styrenes and some conjugated cis-disubstituted alkenes (e.g., cis-beta-methylstyrene, cis-1-phenyl-3-penten-1-yne, 1,2-dihydronaphthalene, and 2,2-dimethylchromenes) are converted effectively to their organic epoxides in 50-80% ee under the Ru(IV)-catalyzed conditions, and more than 850 turnovers of epoxides have been attained. When subjecting 1 to four repetitive uses by recharging the reaction mixture with Cl(2)pyNO and styrene, styrene oxide was obtained in a total of 2190 turnovers and 69% ee. UV-vis and ESI-mass spectral analysis of the final reaction mixture revealed that a ruthenium-carbonyl species could have been formed during the catalytic reaction, leading to the apparent catalyst deactivation. We prepared a heterogeneous chiral ruthenium porphyrin catalyst by immobilizing 1 into sol-gel matrix. The heterogeneous catalyst is highly active toward asymmetric styrene epoxidation producing styrene oxide in 69% ee with up to 10,800 turnovers being achieved. The loss of activity of the Ru/sol-gel catalyst is ascribed to catalyst leaching and/or deactivation. On the basis of Hammett correlation (rho(+) = -1.62, R = 0.99) and product analysis, a

  7. Implementation of PC-SAFT and SAFT + Cubic for modeling thermodynamic properties of eight 1-alkenes and their mixtures

    International Nuclear Information System (INIS)

    Highlights: ► PC-SAFT and SAFT + Cubic are used for modeling properties of 1-alkenes and their mixtures. ► SAFT + Cubic appears as a better estimator of pure compound data than PC-SAFT. ► SAFT + Cubic is superior in modeling inter-relation between VLE and LLE in mixtures. - Abstract: In the current study the widely used theoretically based model PC-SAFT and the recently proposed SAFT + Cubic have been implemented for correlating and predicting various thermodynamic properties of 1-Hexene, 1-Heptene, 1-Octene, 1-Nonene, 1-Decene, 1-Dodecene, 1-Tetradecene, and 1-Hexadecene, and the available high pressure data on their mixtures. Unlike PC-SAFT, SAFT + Cubic is capable of correlating the critical and subcritical pure compound data simultaneously. In addition, SAFT + Cubic is advantageous in predicting the isothermal compressibility factors and sound velocities. It is also superior in correlating the complex phase behavior in the asymmetric systems {Methane(1) + 1-Hexene(2)} and {Methane(1) + 1-Heptene(2)}. Overestimation of critical temperatures and pressures affects the accuracy of PC-SAFT in predicting VLE in the system {n-Hexane(1) + 1-Hexadecene(2)}. At the same time, this disadvantage of PC-SAFT possibly turns into advantage while modeling the VLE data of {Carbon Dioxide(1) + 1-Hexene(2)}. As seems, both of them are capable of only rough estimation of the heat capacity data.

  8. Modeling SOA formation from alkanes and alkenes in chamber experiments: effect of gas/wall partitioning of organic vapors.

    Science.gov (United States)

    Stéphanie La, Yuyi; Camredon, Marie; Ziemann, Paul; Ouzebidour, Farida; Valorso, Richard; Madronich, Sasha; Lee-Taylor, Julia; Hodzic, Alma; Aumont, Bernard

    2014-05-01

    Oxidation products of Intermediate Volatility Organic Compounds (IVOC) are expected to be the major precursors of secondary organic aerosols (SOA). Laboratory experiments were conducted this last decade in the Riverside APRC chamber to study IVOC oxidative mechanisms and SOA formation processes for a large set of linear, branched and cyclic aliphatic hydrocarbons (Ziemann, 2011). This dataset are used here to assess the explicit oxidation model GECKO-A (Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere) (Aumont et al., 2005). The simulated SOA yields agree with the general trends observed in the chamber experiments. They are (i) increasing with the increasing carbon number; (ii) decreasing with increasing methyl branch number; and (iii) increasing for cyclic compounds compared to their corresponding linear analogues. However, simulated SOA yields are systematically overestimated regardless of the precursors, suggesting missing processes in the model. In this study, we assess whether gas-to-wall partitioning of organic vapors can explain these model/observation mismatches (Matsunaga and Ziemann, 2010). First results show that GECKO-A outputs better match the observations when wall uptake of organic vapors is taken into account. Effects of gas/wall partitioning on SOA yields and composition will be presented. Preliminary results suggest that wall uptake is a major process influencing SOA production in the Teflon chambers. References Aumont, B., Szopa, S., Madronich, S.: Modelling the evolution of organic carbon during its gas-phase tropospheric oxidation: development of an explicit model based on a self generating approach. Atmos.Chem.Phys., 5, 2497-2517 (2005). P. J. Ziemann: Effects of molecular structure on the chemistry of aerosol formation from the OH-radical-initiated oxidation of alkanes and alkenes, Int. Rev.Phys.Chem., 30:2, 161-195 (2011). Matsunaga, A., Ziemann, P. J.: Gas-wall partitioning of organic compounds in a Teflon film

  9. Products and Mechanisms of Aerosol Formation from Reactions of OH Radicals with Linear and Branched Alkenes in the Presence of NOx (Invited)

    Science.gov (United States)

    Ziemann, P. J.; Matsunaga, A.

    2009-12-01

    The chemical and physical processes involved in the formation of secondary organic aerosol (SOA) are complex and can include reactions of volatile organic compounds with a number of atmospheric oxidants (the major ones are O3, and OH and NO3 radicals), as well as surface and condensed-phase reactions, homogeneous nucleation, and gas-particle partitioning. It should come as no surprise that understanding and accurately modeling these processes is a major challenge that has not yet been fully addressed. Alkenes emitted from vegetation are the largest source of non-methane hydrocarbons to the global atmosphere and consist mostly of isoprene (C5H8), monoterpenes (C10H16), and sesquiterpenes (C15H24), compounds with a large range of sizes and molecular structures. Their atmospheric oxidation is initiated primarily by reactions with hydroxyl radicals and can lead to a variety of products, some of which can form SOA. Because of the complexity of terpene reactions and the large numbers of products that are formed, there are advantages to studying the chemistry of simpler alkenes in order to gain insights that can be applied to more complex reaction systems. This is the approach we have taken, and in this talk I will report results of studies of the products, SOA yields, and mechanisms of SOA formation from reactions of a variety of linear and branched alkenes with hydroxyl radicals in the presence of nitrogen oxides. Products consist of a large array of multifunctional compounds, including oligomers, containing carbonyl, hydroxy, carboxyl, and nitrate groups. I will demonstrate some of the ways in which changes in molecular structure can alter both gas and SOA products, including those formed through condensed-phase reactions, and also SOA yields, and suggest explanations for these effects based on current understanding of chemical reaction mechanisms.

  10. Inhibition of Growth of a Graphium sp. on Gaseous n-Alkanes by Gaseous n-Alkynes and n-Alkenes

    OpenAIRE

    Curry, S.; Ciuffetti, L.; Hyman, M.

    1996-01-01

    The growth of a filamentous fungus, a Graphium sp., on n-alkanes (C(inf2) to C(inf4)) was inhibited by low concentrations of acetylene, propyne, 1-butyne, ethylene, and propylene. Acetylene and other unsaturated hydrocarbons had no effect on the growth of the Graphium sp. on potato dextrose broth, ethanol, or acetate. Our results suggest that n-alkynes and n-alkenes are selective inhibitors of a nonspecific monooxygenase enzyme responsible for the initial oxidation of n-alkanes.

  11. A new Organopalladium compound containing four Iron (III) Porphyrins for the selective oxidation of alkanes/alkenes by t-BuOOH

    Indian Academy of Sciences (India)

    Manoj Kumar Singh; Debkumar Bandyopadhyay

    2016-03-01

    Two iron(III) tetraphenyl porphyrin catalytic units are connected by an azo-link to form the dimeric compound A. The compound A was then reacted with Pd2+ to make a tetrameric iron(III) porphyrin complex B with all four iron(III) catalytic sites open to the substrates and reactants. Both the compounds were characterized spectroscopically and the results of homogeneous oxidation of some alkanes and alkenes with t-BuOOH in presence of catalytic quantities of A and B have indicated remarkable improvement in selectivity and efficiency of A over the monomeric catalyst and B over A.

  12. Rhodium(III) Catalyzed Carboamination of Alkenes Triggered by C-H Activation of N-Phenoxyacetamides under Redox-Neutral Conditions.

    Science.gov (United States)

    Hu, Zhiyong; Tong, Xiaofeng; Liu, Guixia

    2016-04-01

    N-Alkoxyacrylamides are coupled with N-phenoxyacetamides by Rh(III) catalysis through C-H functionalization and amido group transfer under external oxidant-free conditions, which affords acyclic alkene carboamination products in an atom-economical way. Mechanistic insight into this transformation indicates the amide group in N-alkoxyacrylamide plays a critical role in this C-C/C-N bond formation reaction. This methodology provides a highly efficient way to construct o-tyrosine derivatives under mild conditions. PMID:27002932

  13. Reaction Mechanism of the Hydrogermylation/Hydrostannylation of Unactivated Alkenes with Two-Coordinate E(II) Hydrides (E=Ge, Sn): A Theoretical Study.

    Science.gov (United States)

    Zhao, Lili; Hermann, Markus; Jones, Cameron; Frenking, Gernot

    2016-08-01

    Quantum chemical calculations using density functional theory with the TPSS+D3(BJ) and M06-2X+D3(ABC) functionals have been carried out to understand the mechanisms of catalyst-free hydrogermylation/hydrostannylation reactions between the two-coordinate hydrido-tetrylenes :E(H)(L(+) ) (E=Ge or Sn, L(+) =N(Ar(+) )(SiiPr3 ); Ar(+) =C6 H2 {C(H)Ph2 }2 iPr-2,6,4) and a range of unactivated terminal (C2 H3 R, R=H, Ph, or tBu) and cyclic [(CH)2 (CH2 )2 (CH2 )n , n=1, 2, or 4] alkenes. The calculations suggest that the addition reactions of the germylenes and stannylenes to the cyclic and acyclic alkenes occur as one-step processes through formal [2+2] addition of the E-H fragment across the C-C π bond. The reactions have moderate barriers and are weakly exergonic. The steric bulk of the tetrylene amido groups has little influence on the activation barriers and on the reaction energies of the anti-Markovnikov pathway, but the Markovnikov addition is clearly disfavored by the size of the substituents. The addition of the tetrylenes to the cyclic alkenes is less exergonic than the addition to the terminal alkenes, which agrees with the experimentally observed reversibility of the former reactions. The hydrogermylation reactions have lower activation energies and are more exergonic than the stannylene addition. An energy decomposition analysis of the transition state for the hydrogermylation of cyclohexene shows that the reaction takes place with simultaneous formation of the Ge-C and (Ge)H-C' bonds. The dominant orbitals of the germylene are the σ-type lone pair MO of Ge, which serves as a donor orbital, and the vacant p(π) MO of Ge, which acts as acceptor orbital for the π* and π MOs of the olefin. Inspection of the transition states of some selected reactions suggests that the differences between the activation energies come from a delicate balance between the deformation energies of the interacting species and their interaction energies. PMID:27403941

  14. Equilibrium 2H/ 1H fractionations in organic molecules. II: Linear alkanes, alkenes, ketones, carboxylic acids, esters, alcohols and ethers

    Science.gov (United States)

    Wang, Ying; Sessions, Alex L.; Nielsen, Robert J.; Goddard, William A., III

    2009-12-01

    Equilibrium 2H/ 1H fractionation factors (α eq) for various H positions in alkanes, alkenes, ketones, carboxylic acids, esters, alcohols, and ethers were calculated between 0 and 100 °C using vibrational frequencies from ab initio QM calculations (B3LYP/6-311G**). Results were then corrected using a temperature-dependent linear calibration curve based on experimental data for H α in ketones ( Wang et al., 2009). The total uncertainty in reported α eq values is estimated at 10-20‰. The effects of functional groups were found to increase the value of α eq for H next to electron-donating groups, e.g. sbnd OR, sbnd OH or sbnd O(C dbnd O)R, and to decrease the value of α eq for H next to electron-withdrawing groups, e.g. sbnd (C dbnd O)R or sbnd (C dbnd O)OR. Smaller but significant functional group effects are also observed for H β and sometimes H γ. By summing over individual H positions, we estimate the equilibrium fractionation relative to water to be -90‰ to -70‰ for n-alkanes and around -100‰ for pristane and phytane. The temperature dependence of these fractionations is very weak between 0 and 100 °C. Our estimates of α eq agree well with field data for thermally mature hydrocarbons (δ 2H values between -80‰ and -110‰ relative to water). Therefore the observed δ 2H increase of individual hydrocarbons and the disappearance of the biosynthetic δ 2H offset between n-alkyl and linear isoprenoid lipids during maturation of organic matter can be confidently attributed to H exchange towards an equilibrium state. Our results also indicate that many n-alkyl lipids are biosynthesized with δ 2H values that are close to equilibrium with water. In these cases, constant down-core δ 2H values for n-alkyl lipids cannot be reliably used to infer a lack of isotopic exchange.

  15. Impact of chamber wall loss of gaseous organic compounds on secondary organic aerosol formation: explicit modeling of SOA formation from alkane and alkene oxidation

    Science.gov (United States)

    La, Y. S.; Camredon, M.; Ziemann, P. J.; Valorso, R.; Matsunaga, A.; Lannuque, V.; Lee-Taylor, J.; Hodzic, A.; Madronich, S.; Aumont, B.

    2016-02-01

    Recent studies have shown that low volatility gas-phase species can be lost onto the smog chamber wall surfaces. Although this loss of organic vapors to walls could be substantial during experiments, its effect on secondary organic aerosol (SOA) formation has not been well characterized and quantified yet. Here the potential impact of chamber walls on the loss of gaseous organic species and SOA formation has been explored using the Generator for Explicit Chemistry and Kinetics of the Organics in the Atmosphere (GECKO-A) modeling tool, which explicitly represents SOA formation and gas-wall partitioning. The model was compared with 41 smog chamber experiments of SOA formation under OH oxidation of alkane and alkene series (linear, cyclic and C12-branched alkanes and terminal, internal and 2-methyl alkenes with 7 to 17 carbon atoms) under high NOx conditions. Simulated trends match observed trends within and between homologous series. The loss of organic vapors to the chamber walls is found to affect SOA yields as well as the composition of the gas and the particle phases. Simulated distributions of the species in various phases suggest that nitrates, hydroxynitrates and carbonylesters could substantially be lost onto walls. The extent of this process depends on the rate of gas-wall mass transfer, the vapor pressure of the species and the duration of the experiments. This work suggests that SOA yields inferred from chamber experiments could be underestimated up a factor of 2 due to the loss of organic vapors to chamber walls.

  16. Photoionization mass spectrometer studies of the collisionally stabilized product distribution in the reaction of OH radicals with selected alkenes at 298 K

    International Nuclear Information System (INIS)

    The reactions of OH radicals with propene, 1-butene, and 1-pentene have been studied in a discharge flow system coupled to a photoionization mass spectrometer. At total pressures near 2 torr a collisionally stabilized OH-alkene adduct was observed in each case. For 1-butene and 1-pentene the radicals arising from abstraction of a hydrogen atom from the alkene by OH were also observed and their absolute concentrations measured under controlled conditions. Contributions of the abstraction pathway to the overall reaction were as follows: propene, 3P) and OH taken from the literature and/or measured in this work. Rate constants (in cm3 molecule-1 s-1) obtained as part of this study include the following: k/sub OH+butene/ = (3.0 +- 0.4) x 10-11; k/sub OH+1-pentene/ = (2.9 +- 0.4) x 10-11, (2.87 +- 0.13) x 10-11 (50 torr of Ar); k/sub O(3P)+propene/ = (4.4 +- 0.6) x 10-12;k/sub O(3P)+1-pentene/ = (4.7 +- 0.5) x 10-12; k/sub OH+CS2/ less than or equal to 5 x 10-14, at 298 K and 2 torr of He total pressure unless otherwise stated. 5 figures, 2 tables

  17. Synthesis of dienyl ketones via palladium(II)-catalyzed direct cross-coupling reactions between simple alkenes and vinyl ketones: application to the synthesis of vitamin A1 and bornelone.

    Science.gov (United States)

    Zhang, Xiang; Wang, Min; Zhang, Ming-Xin; Xu, Yun-He; Loh, Teck-Peng

    2013-11-01

    An efficient and general method for the synthesis of conjugated dienyl ketones via palladium(II) acetate catalyzed direct cross-coupling between simple alkenes and vinyl ketones is reported. This method has been successfully applied for the synthesis of Vitamin A1 and bornelone. PMID:24131401

  18. Green Michael addition of thiols to electron deficient alkenes using KF/alumina and recyclable solvent or solvent-free conditions

    Energy Technology Data Exchange (ETDEWEB)

    Lenardao, Eder J.; Trecha, Danusia O.; Ferreira, Patricia da C.; Jacob, Raquel G.; Perin, Gelson [Universidade Federal de Pelotas (UFPEL), Pelotas, RS (Brazil). Inst. de Quimica e Geociencias. Lab. de Sintese Organica Limpa (LASOL)]. E-mail: lenardao@ufpel.edu.br

    2009-07-01

    A general, clean and easy method for the conjugated addition of thiols to citral promoted by KF/Al{sub 2}O{sub 3} under solvent-free or using glycerin as recyclable solvent at room temperature is described. It was found that the solvent-free protocol is applicable to the direct reaction of thiophenol with the essential oil of lemon grass (Cymbopogon citratus) to afford directly 3,7-dimethyl-3-(phenylthio)oct-6-enal, a potential bactericide agent. The method was extended to other electron-poor alkenes with excellent results. For the solvent-free protocol, the use of microwave irradiation facilitated the procedure and accelerates the reaction. The catalytic system and glycerin can be reused up to three times without previous treatment with comparable activity. (author)

  19. Green Michael addition of thiols to electron deficient alkenes using KF/alumina and recyclable solvent or solvent-free conditions

    International Nuclear Information System (INIS)

    A general, clean and easy method for the conjugated addition of thiols to citral promoted by KF/Al2O3 under solvent-free or using glycerin as recyclable solvent at room temperature is described. It was found that the solvent-free protocol is applicable to the direct reaction of thiophenol with the essential oil of lemon grass (Cymbopogon citratus) to afford directly 3,7-dimethyl-3-(phenylthio)oct-6-enal, a potential bactericide agent. The method was extended to other electron-poor alkenes with excellent results. For the solvent-free protocol, the use of microwave irradiation facilitated the procedure and accelerates the reaction. The catalytic system and glycerin can be reused up to three times without previous treatment with comparable activity. (author)

  20. Synthesis of chiral N-phosphoryl aziridines through enantioselective aziridination of alkenes with phosphoryl azide via Co(II-based metalloradical catalysis

    Directory of Open Access Journals (Sweden)

    Jingran Tao

    2014-06-01

    Full Text Available The Co(II complex of a new D2-symmetric chiral porphyrin 3,5-DiMes-QingPhyrin, [Co(P6], can catalyze asymmetric aziridination of alkenes with bis(2,2,2-trichloroethylphosphoryl azide (TcepN3 as a nitrene source. This new Co(II-based metalloradical aziridination is suitable for different aromatic olefins, producing the corresponding N-phosphorylaziridines in good to excellent yields (up to 99% with moderate to high enantioselectivities (up to 85% ee. In addition to mild reaction conditions and generation of N2 as the only byproduct, this new metalloradical catalytic system is highlighted with a practical protocol that operates under neutral and non-oxidative conditions.

  1. Phosphine-Catalyzed [2 + 4] Annulation of Allenoates with Thiazolone-Derived Alkenes: Synthesis of Functionalized 6,7-Dihydro-5H-pyrano[2,3-d]thiazoles.

    Science.gov (United States)

    Wang, Chang; Gao, Zhenzhen; Zhou, Leijie; Yuan, Chunhao; Sun, Zhanhu; Xiao, Yumei; Guo, Hongchao

    2016-07-15

    Phosphine-catalyzed [2 + 4] annulation of allenoates with thiazolone-derived alkenes has been achieved under mild conditions, giving biologically important 6,7-dihydro-5H-pyrano[2,3-d]thiazole derivatives in high to excellent yields. With the use of Kwon's phosphine as the chiral catalyst, optically active products were obtained in good yields with excellent enantioselectivities. PMID:27378106

  2. Molybdenum oxide catalysts for metathesis of higher 1-alkenes via supporting MoO2(acetylacetonate)2 and MoO2(glycolate)2 on SBA-15 mesoporous molecular sieves

    Czech Academy of Sciences Publication Activity Database

    Balcar, Hynek; Mishra, D.; Marceau, E.; Carrier, X.; Žilková, Naděžda; Bastl, Zdeněk

    2009-01-01

    Roč. 359, 1-2 (2009), s. 129-135. ISSN 0926-860X R&D Projects: GA MŠk MEB020723; GA AV ČR IAA400400805; GA AV ČR KAN100400701 Institutional research plan: CEZ:AV0Z40400503 Keywords : 1-alkene metathesis * Mo heterogeneous catalysts * Molybdenum dioxide bis(acetylacetonate) * Molybdenum dioxide bis(glycolate) Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.564, year: 2009

  3. Polyoxometalate systems for the catalytic selective production of nonthermodynamic alkenes from alkanes. Nature of excited-state deactivation processes and control of subsequent thermal processes in polyoxometalate photoredox chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Renneke, R.F.; Pasquali, M.; Hill, C.L. (Emory Univ., Atlanta, GA (USA))

    1990-08-29

    The photooxidations of exemplary branched acyclic alkanes and cycloalkanes by a range of polyoxotungstates varying in charge density, ground-state redox potential, acidity, and other properties were examined in detail. The organic products generated in these reactions depend on the polyoxometalate used, and in particular on the ground-state redox potential of the complex. Under anaerobic conditions acyclic branched alkanes yield principally alkenes, while cycloalkanes yield principally alkenes and dimers. Alkyl methyl ketones, derived in part from reaction with acetonitrile solvent, and isomerized alkanes are produced with some alkane substrates. Under aerobic conditions, autoxidation, initiated by radicals generated in the photoinduced redox chemistry, is observed. Under aerobic conditions the polyoxotungstates with formal redox potentials more negative than {minus}1.0 V vs Ag/AgNO{sub 3}(CH{sub 3}CN), such as W{sub 10}O{sub 32}{sup 4{minus}} and W{sub 6}O{sub 19}{sup 2{minus}}, photochemically dehydrogenate branched acyclic alkanes in high selectivity to {alpha}-olefins and the least substituted alkenes, products heretofore undocumented in photooxidation reactions catalyzed by polyoxometalates.

  4. Competition between lone pair–π, halogen bond, and hydrogen bond in adducts of water with perhalogenated alkenes C2ClnF4−n (n = 0–4)

    International Nuclear Information System (INIS)

    Highlights: • Charge transfer from O lone pair to alkene π* antibonding orbital. • lp→π is most strongly bound complex type between H2O and perhalogenated alkenes. • Binding energies larger than 2 kcal/mol, insensitive to identity of halogen atoms. • Halogen-bonded complexes are slightly less stable, followed by OH⋯X H-bond. - Abstract: A thorough search of the potential energy surface is carried out for heterodimers of water with C2ClnF4−n. Three different types of interactions are observed. Structures dominated by a lone pair–π interaction have the highest binding energies, and are stabilized by charge transfer from O lone pairs of H2O to the C-C π* antibonding orbital of the alkene. Halogen-bonded O⋯Cl complexes are slightly less strongly bound, followed by OH⋯X hydrogen bonds. The replacements of Cl by F atoms have only small effects upon binding energies. Inclusion of vibrational and entropic effects removes the clear energetic superiority of lp–π binding energies. When combined with the observation of several similar geometries for each particular heterodimer type, and a sensitivity to basis set, it would be quite difficult to predict with any degree of certainty the single most stable configuration, even with very high level calculations

  5. Competition between lone pair–π, halogen bond, and hydrogen bond in adducts of water with perhalogenated alkenes C{sub 2}Cl{sub n}F{sub 4−n} (n = 0–4)

    Energy Technology Data Exchange (ETDEWEB)

    Adhikari, Upendra; Scheiner, Steve, E-mail: steve.scheiner@usu.edu

    2014-08-31

    Highlights: • Charge transfer from O lone pair to alkene π{sup *} antibonding orbital. • lp→π is most strongly bound complex type between H{sub 2}O and perhalogenated alkenes. • Binding energies larger than 2 kcal/mol, insensitive to identity of halogen atoms. • Halogen-bonded complexes are slightly less stable, followed by OH⋯X H-bond. - Abstract: A thorough search of the potential energy surface is carried out for heterodimers of water with C{sub 2}Cl{sub n}F{sub 4−n}. Three different types of interactions are observed. Structures dominated by a lone pair–π interaction have the highest binding energies, and are stabilized by charge transfer from O lone pairs of H{sub 2}O to the C-C π{sup *} antibonding orbital of the alkene. Halogen-bonded O⋯Cl complexes are slightly less strongly bound, followed by OH⋯X hydrogen bonds. The replacements of Cl by F atoms have only small effects upon binding energies. Inclusion of vibrational and entropic effects removes the clear energetic superiority of lp–π binding energies. When combined with the observation of several similar geometries for each particular heterodimer type, and a sensitivity to basis set, it would be quite difficult to predict with any degree of certainty the single most stable configuration, even with very high level calculations.

  6. Palladium nanoparticles supported on fibrous-structured silica nanospheres (KCC-1): An efficient and selective catalyst for the transfer hydrogenation of alkenes

    KAUST Repository

    Qureshi, Ziyauddin

    2015-01-09

    An efficient palladium catalyst supported on fibrous silica nanospheres (KCC-1) has been developed for the hydrogenation of alkenes and α,β-unsaturated carbonyl compounds, providing excellent yields of the corresponding products with remarkable chemoselectivity. Comparison (high-resolution TEM, chemisorption) with analogous mesoporous (MCM-41, SBA-15) silica-supported Pd nanocatalysts prepared under identical conditions, demonstrates the advantage of employing the fibrous KCC-1 morphology versus traditional supports because it ensures superior accessibility of the catalytically active cores along with excellent Pd dispersion at high metal loading. This morphology ultimately leads to higher catalytic activity for the KCC-1-supported nanoparticles. The protocol developed for hydrogenation is advantageous and environmentally benign owing to the use of HCOOH as a source of hydrogen, water as a solvent, and because of efficient catalyst recyclability and durability. The recycled catalyst has been analyzed by XPS spectroscopy and TEM showing only minor changes in the oxidation state of Pd and in the morphology after the reaction, thus confirming the robustness of the catalyst.

  7. Quantitative determination of triperpene saponins and alkenated-phenolics from Labisia pumila using an LC-UV/ELSD method and confirmation by LC-ESI-TOF.

    Science.gov (United States)

    Avula, Bharathi; Wang, Yan-Hong; Ali, Zulfiqar; Smillie, Troy J; Khan, Ikhlas A

    2011-10-01

    This study describes the first analytical method for the determination of four triterpene saponins (ardisicrenoside B, ardisiacrispin A, 3- O- α- L-rhamnopyranosyl-(1 → 2)-β-D-glucopyranosyl-(1 → 4)-α-L-arabinopynanosyl cyclamiretin A and ardisimamilloside H) and three alkenated-phenolics (irisresorcinol, belamcandol B, and demethylbelamcandaquinone B) from the leaves, leaves/stems, and roots of LABISIA PUMILA using an HPLC-UV-ELSD method. The separation was achieved using a reversed-phase (C-18) column, PDA and ELS detection, and a water/acetonitrile gradient as the mobile phase. The major triterpenoid (ardisiacrispin A) and irisresorcinol compounds were detected at a concentration as low as 10.0 and 0.2 µg/mL, respectively. Analysis of various samples showed considerable variation of 0.11-2.46 % for the major triterpenoid compound, ardisiacrispin A. LC-mass spectrometry method coupled with electrospray ionization (ESI) is described for the identification of compounds in plant samples. This method involved the use of the [M + Na]+ and [M + NH₄]+ ions for compounds 1-4 in the positive ion mode with extractive ion chromatogram (EIC). PMID:21590653

  8. Regioselectivity in the [2 + 2] cyclo-addition reaction of triplet carbonyl compounds to substituted alkenes (Paterno-Büchi reaction): A spin-polarized conceptual DFT approach

    Indian Academy of Sciences (India)

    B Pintér; F De Proft; T Veszprémi; P Geerlings

    2005-09-01

    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 regioselectivity is explained using a series of DFT-based reactivity indices. In the first step, we use the local softness and the local HSAB principle within a softness matching approach, and explain the relative activation barriers of the addition step. In the final step, the regioselectivity is assessed within the framework of spin-polarized conceptual density functional theory, considering response functions of the system's external potential , number of electrons and spin number , being the difference between the number of and electrons in the spin-polarized system. Although the concept of local spin philicity, introduced recently within this theory, appears less suited to predict the regioselectivity in this reaction, the correct regioselectivity emerges from considering an interaction between the largest values of the generalized Fukui functions ss on both interacting molecules.

  9. Oligomer formation during gas-phase ozonolysis of small alkenes and enol ethers: new evidence for the central role of the Criegee Intermediate as oligomer chain unit

    Directory of Open Access Journals (Sweden)

    A. Sadezky

    2008-05-01

    Full Text Available An important fraction of secondary organic aerosol (SOA formed by atmospheric oxidation of diverse volatile organic compounds (VOC has recently been shown to consist of high-molecular weight oligomeric species. In our previous study (Sadezky et al., 2006, we reported the identification and characterization of oligomers as main constituents of SOA from gas-phase ozonolysis of small enol ethers. These oligomers contained repeated chain units of the same chemical composition as the main Criegee Intermediates (CI formed during the ozonolysis reaction, which were CH2O2 (mass 46 for alkyl vinyl ethers (AVE and C2H4O2 (mass 60 for ethyl propenyl ether (EPE. In the present work, we extend our previous study to another enol ether (ethyl butenyl ether EBE and a variety of structurally related small alkenes (trans-3-hexene, trans-4-octene and 2,3-dimethyl-2-butene.

    Experiments have been carried out in a 570 l spherical glass reactor at atmospheric conditions in the absence of seed aerosol. SOA formation was measured by a scanning mobility particle sizer (SMPS. SOA filter samples were collected and chemically characterized off-line by ESI(+/TOF MS and ESI(+/TOF MS/MS, and elemental compositions were determined by ESI(+/FTICR MS and ESI(+/FTICR MS/MS. The results for all investigated unsaturated compounds are in excellent agreement with the observations of our previous study. Analysis of the collected SOA filter samples reveal the presence of oligomeric compounds in the mass range 200 to 800 u as major constituents. The repeated chain units of these oligomers are shown to systematically have the same chemical composition as the respective main Criegee Intermediate (CI formed during ozonolysis of the unsaturated compounds, which is C3H6O2 (mass 74 for ethyl butenyl ether (EBE, trans-3-hexene, and 2,3-dimethyl-2-butene, and C4H8

  10. Chemical Imaging of Catalyst Deactivation during the Conversion of Renewables at the Single Particle Level: The Etherification of Biomass-based Polyols with Alkenes over H-Beta Zeolites

    Energy Technology Data Exchange (ETDEWEB)

    A Parvulescu; D Mores; E Stavitski; C Teodorescu; P Bruijnicx; R Klein Gebbing; B Weckhuysen

    2011-12-31

    The etherification of biomass-based alcohols with various linear {alpha}-olefins under solvent-free conditions was followed in a space- and time-resolved manner on 9 {micro}m large H-Beta zeolite crystals by confocal fluorescence microscopy. This allowed us to visualize the interaction with the substrate and distribution of the coke products into the catalyst at the level of an individual zeolite crystal during the etherification process. The spectroscopic information obtained on the micrometer-scale zeolite was in line with the results obtained with bulk characterization techniques and further confirmed by the catalytic results obtained both for micrometer-scale and nanoscale zeolites. This allowed us to explain the influence of the substrate type (glycerol, glycols, and alkenes) and zeolite properties (Si/Al ratio and particle size) on the etherification activity. The etherification of the biomass-based alcohols takes place mainly on the external surface of the zeolite particles. The gradual blockage of the external surface of the zeolite results in a partial or total loss of etherification activity. The deactivation could be attributed to olefin oligomerization. The high conversions obtained in the etherification of 1,2-propylene glycol with long linear alkenes (up to 80%) and the pronounced deactivation of the zeolite observed in the etherification of glycerol with long linear alkenes (max. 20% conversion) were explained by the spectroscopic measurements and is due to differences in the adsorption, i.e., in the center of the zeolite particle for glycerol and on the external surface in the case of glycols.

  11. Literature study and experimental investigations into the production of organic iodine compounds in alkene, alkanol as well as benzene-vapour/air mixtures with radioiodine in the radiation field

    International Nuclear Information System (INIS)

    It was assumed in these investigations that these compounds originated in the gas phase by irradiation - induced reactions with radioiodine. Benzene, alcohol (methanol, ethanol) and alkene (ethylene, propylene) vapour/air mixtures were radiolysed with iodine in a Co-60 gamma source. The parameters varied were the concentrations and the irradiation doses (2 E + 03 Gy - 6 E + 04 Gy). The gaseous reaction mixtures were analysed qualitatively and quantitatively by an ECD- and a MSD-detector for iodine compounds difficult to separate. (orig.)

  12. Optimized sampling of hydroperoxides and investigations of the water vapour dependence of hydroperoxide formation during ozonolysis of alkenes; Optimierung der Probenahme von Hydroperoxiden und Untersuchungen zur Wasserdampfabhaengigkeit der Bildung von Hydroperoxiden bei der Ozonolyse von Alkenen

    Energy Technology Data Exchange (ETDEWEB)

    Becker, K.H.; Plagens, H.

    1997-06-01

    There are several sampling methods for hydroperoxides none of which is particularly reliable. The authors therefore tested three new methods in order to optimize hydroperoxide sampling and, using the optimized sampling procedure, to investigate the water vapour dependence of hydroperoxide formation during ozonolysis of alkenes. (orig.) [Deutsch] Fuer die Probenahme von Hydroperoxiden existieren verschiedene Verfahren, von denen bisher keines als besonders zuverlaessig angesehen werden konnte. Daher wurden in dieser Arbeit drei Verfahren getestet, um die Probenahme von Hydroperoxiden zu optimieren und mit dem entsprechenden Verfahren die Wasserdampfabhaengigkeit der Bildung von Hydroperoxiden bei der Ozonolyse von Alkenen zu untersuchen. (orig.)

  13. Laser activation-modification of semiconductor surfaces (LAMSS) of 1-alkenes on silicon: A ToF-SIMS, chemometrics, and AFM analysis

    International Nuclear Information System (INIS)

    Laser-activation-modification of semiconductor surfaces (LAMSS) was carried out on silicon with a series of 1-alkenes. These laser spots were studied by time of flight secondary ion mass spectrometry (ToF-SIMS). The resulting spectra were analyzed using the multivariate curve resolution (MCR) method within the Automated eXpert Spectral Image Analysis (AXSIA) toolkit, and also by MCR and cluster analysis using commercially available toolboxes for Matlab: the PLSToolbox and the MIAToolbox, respectively. AXSIA based MCR generally finds three components for the spectral images: one for the background and two for the laser-activated spots, for both the positive and negative ion images. The negative ion component spectra from the spots show increased carbon and hydrogen signals compared to oxygen. They also show reduced chlorine and fluorine (contamination) peaks. In order to compare AXSIA-MCR results from different images, the AXSIA component spectra of different spots were further analyzed by principal components analysis (PCA). PCA of all of the negative ion components shows that component 1 is chemically distinct from components 2 and 3. PCA of all of the positive ion components yields the same result. The loadings plots of this PCA analysis confirm that component 1 generally contains fragments expected from the substrate, while components 2 and 3 contain fragments expected from an overlayer composed of alkyl chains in the spots. A comparison of the two MCR analyses suggests that roughly the same information can be obtained from AXSIA, which is not commercially available, and the PLSToolbox. Cluster analysis of the data also clearly separates the spots from the backgrounds. A key finding from these analyses is that the degree of surface functionalization in a LAMSS spot appears to decrease radially from the center of the spot. Finally, a comparison of atomic force microscopy (AFM) of the spots versus the AXSIA analysis of the ToF-SIMS data produced another important

  14. Celite Catalysed Alkylation of Alkenes

    Directory of Open Access Journals (Sweden)

    Irma Rojas-Oviedo

    2005-01-01

    Full Text Available En presencia de celita, alquenos mono- y di-sistituidos pueden ser alquilados con halogenuros de bencilo a temperatura ambiente. Para formar el enlace C-C, fue necesario usar compuestos aromáticos activados con alquenos o ésteres propargílicos.

  15. Gas-phase chemistry of the yttrium-imido cation YNH{sup +} with alkenes: {Beta}-hydrogen activation by a d{sup 0} system via a multicentered transition state

    Energy Technology Data Exchange (ETDEWEB)

    Ranatunga, D.R.A.; Hill, Y.D.; Freiser, B.S. [Purdue Univ., West Lafayette, IN (United States)

    1996-02-20

    The gas-phase chemistry of the yttrium-imido carbon cations with alkenes was studied by using Fourier transform mass spectrometry to explore the chemistry of transition metal ion complexes with low-valence metal centers. The YNH{sup +} species was synthesized by reacting Y{sup +}, generated by laser desorption, with ammonia. The dehydrogenation reaction is exothermic, yielding a lower limit for the imido bond energy of D{degree}(Y{sup +}-NH) > 101 kcal/mol. Due to the electron deficiency of the metal center upon binding to NH, the further reactivity of YNH{sup +} can only be explained by a reaction mechanism involving a multicentered transition state. YNH{sup +} reacts with ethene predominantly by dehydrogenation to produce YC{sub 2}H{sub 3}N{sup +}. Thus, instead of the metathesis reaction involving the cleavage of the 2-aza-1-metallacyclobutane intermediate, a {beta}-hydrogen transfers to the metal center and is then eliminated with a hydrogen from the remaining CH{sub 2} group to complete the reaction. All three linear butenes, 1-butene, cis-2-butene, and trans-2-butene, react very similarly with YNH{sup +}, yielding a variety of product ions with the predominant loss of NH{sub 3} resulting in the formation of YCH{sub 4}H{sub 6}{sup +}. Structural studies on this ion suggest that it is bent metallacyclopent-3-ene, not the butadiene isomer. 34 refs., 1 fig.

  16. Investigation of the NH-π hydrogen bond interaction in the aniline-alkene (C2H4,C3H6,C4H8) cluster cations by infrared depletion spectroscopy

    International Nuclear Information System (INIS)

    The vibrational spectra of the NH stretching vibrations of aniline-alkene cluster cations have been measured using infrared depletion method. Aniline-ethene cation showed three strong absorption bands at 3448, 3314 and 3220 cm-1. The comparison with MO calculation has shown that the main intermolecular interaction is the NH-π type hydrogen bond between one of the NH bonds of aniline cation and π-electron of ethene, which is different from that observed for the neutral aniline-ethene cluster. The bands at 3448 and 3220 cm-1 have been assigned to the stretching vibrations of free NH and bonded NH, respectively, and the band at 3314 cm-1 to the binary overtone of the NH2 deformation vibration. Similar results have been obtained for aniline-propene and aniline-butene cluster cations. The red shift of the stretching vibration of free NH bond of aniline cation agreed with that expected from the correlation with the proton affinity of the acceptor molecule obtained for the aniline-aromatic cluster cations (NH-π type)

  17. Alken en Zeekoeten op het Friese Front

    OpenAIRE

    Bemmelen, van, R.S.A.; Arts, F.; Leopold, M.F.

    2013-01-01

    Het Friese Front, zoals omschreven en geografisch aangeduid in het rapport van Lindeboom et al. (2005) zal worden aangewezen als Vogelrichtlijngebied, c.q. Natura 2000 gebied. Eén belangrijke reden voor de aanwijzing is de aanwezigheid, in zomer, nazomer en herfst, van internationaal belangrijke aantallen Zeekoeten Uria aalge. Vanwege de bijzondere status van het gebied is het belangrijk om te weten welke aantallen Zeekoeten het gebied bezoeken en wat de trends in aantallen zijn. Nederland mo...

  18. High court orders Lavents retrial / Ib Alken

    Index Scriptorium Estoniae

    Alken, Ib

    2003-01-01

    Pärast Euroopa Inimõiguste Kohtu otsust, mille kohaselt rikkus Läti riik Banka Baltija endise juhi Aleksandrs Lavents'i kohtuasja menetlemisel tema põhiõigusi, mõistis Läti Riigikohus asja uuesti läbivaatamisele

  19. Gas-phase chemistry of Sc(CH{sub 3}){sub 2}{sup +} with alkenes: Activation of allylic C-H bonds by a d{sup 0} system and the migratory insertion of C=C bonds into Sc{sup +}-CH{sub 3} bonds

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Yongqing; Hill, Y.D.; Freiser, B.S. [Purdue Univ., West Lafayette, IN (United States)] [and others

    1992-11-04

    The gas-phase chemistry of Sc(CH{sub 3}){sub 2}{sup +} with alkenes was studied by Fourier transform mass spectrometry. The metal center on Sc(CH{sub 3}){sub 2}{sup +} is d{sup 0}, providing an opportunity to study alternative mechanisms of C-C or C-H activation other than the most common one involving oxidative addition. The elimination of H{sub 2} is observed in the reaction of Sc(CH{sub 3}){sub 2}{sup +} with ethylene, and the product ScC{sub 4}H{sub 8}{sup +} and ScC{sub 6}H{sub 10}{sup +} ions have a metal(methyl)(allyl) and metal-bisallyl structure, respectively, consistent with a proposed reaction mechanism involving the consecutive migratory insertion of ethylenes into the scandium-methyl bonds. In addition, theoretical calculations indicate that the metal(methyl)(allyl) structure is between 10 and 20 kcal/mol more stable than the metal(1-butene) isomer. Sc(CH{sub 3}){sub 2}{sup +} reacts with propene to form predominantly ScC{sub 4}H{sub 8}{sup +} by loss of CH{sub 4}, with minor amounts of ScC{sub 3}H{sub 4}{sup +} and ScC{sub 4}H{sub 6}{sup +} also observed. ScC{sub 4}H{sub 6}{sup +} is formed as either the exclusive or the predominant product ion in the reactions of Sc(CH{sub 3}){sub 2}{sup +} with butenes. Sc(CH{sub 3}){sub 2} reacts with cyclopentene to form predominantly ScC{sub 6}H{sub 8}{sup +} by losing CH{sub 4} and H{sub 2}. Isotope labeling studies with Sc(CD{sub 3}){sub 2}{sup +} and other structure studies indicate that all of the alkenes studied, with the exception of ethylene, react with Sc(CH{sub 3}){sub 2}{sup +} via a multicentered {sigma}-bond metathesis mechanism to activate allylic C-H bonds. Finally, the dehydrogenation reactions of Sc{sup +} with n-butane and neopentane were revisited, and a new mechanism is proposed for such chemistry in light of the new results from this study. 34 refs., 5 figs., 2 tabs.

  20. 碳青霉烯类治疗儿童白血病粒细胞缺乏感染临床疗效探讨%Penicillium Carbon Alkene Treatment of Childhood Ieukemia Granulocyte Lack of Infection Clinical Curative Effect Observation

    Institute of Scientific and Technical Information of China (English)

    郑丽

    2015-01-01

    目的:探讨碳青霉烯类治疗儿童白血病粒细胞缺乏感染的临床效果。方法选取2011年11月—2013年11月在该院接受儿童白血病粒细胞缺乏感染治疗的患儿70例随机分为观察组和对照组。观察组患儿给予美罗培兰治疗,对照组患儿给予亚胺培南治疗。结果观察组治疗有效率为97.1%,对照组共治疗有效率为88.6%,观察组治疗效果要明显好于对照组,两组比较差异具有统计学意义(P<0.05)。此外观察组仅有1例患儿发生了不良反应,不良反应的发生率为2.9%;对照组有4例患儿发生了不良反应,不良反应的发生率为11.4%,比较差异有统计学意义(P<0.05)。结论碳青霉烯类药物具有很好的效果,其中美罗培兰效果明显且安全性强,在治疗儿童白血病粒细胞缺乏感染患儿的时候具有显著的效果。%Objective to explore the penicillium carbon alkene clinical effect for the treatment of childhood leukemia granulocyte lack of infection. Methods select in November 2011 to November 2013 in our hospital for treatment of children with leukemia granulocyte lack of infections in children, 70 cases were randomly divided into observation group and control group. Observation group to give the children Luo Peilan treatment, children with the control group given imine culture south treatment. Results ob-servation group treatment effective rate of 97.1%, control group total effective rate was 88.6%, two groups of children with treat-ment, efficient, without statistical significance (P>0.05);Observation group of children to better the effect of pseudomonas aerugi-nosa, small side effects, but the average defervescence time is longer than the control group, with statistical significance ( P<0.05). Conclusion penicillium carbon alkene drugs has very good effect, the beautiful Luo Peilan effect and the safety is strong, in the treatment of childhood leukemia granulocyte when children lack of

  1. Synthesis of 3-Unsubstituted Indolizines from Electron Deficient Alkenes under Transition Metal Free Conditions%无过渡金属存在下从缺电子烯烃出发合成3位未取代的中氮茚

    Institute of Scientific and Technical Information of China (English)

    胡华友; 李国栋; 顾宁; 吉民

    2016-01-01

    3-Unsubstituted indolizine not only exhibits a variety of important biological activities,but also is a kind of important intermediate in organic synthesis.A transition metal free method for synthesizing 3-unsubstituted indolizines from pyridines,2-chloroacetic acid and electron deficient alkenes has been invented in this paper.The designed products were obtained via oxidative dehydrogenation and decarboxylation reactions,and 2,2,6,6-tetramthyl-1-piperidinyloxy (TEMPO) was used as an oxidant.This method featured simple procedure,easy available starting materials and transition metal free conditions.%3位未取代的中氮茚不仅具有多种重要的生物活性,且是重要的有机合成中间体.报道了一种从吡啶衍生物、氯乙酸和缺电子烯烃出发,在无过渡金属存在下合成3位未取代的中氮茚的新方法.该反应的关键步骤为四氢中氮茚中间体在2,2,6,6-四甲基哌啶氮氧自由基(TEMPO)存在下的氧化脱氢芳构化和脱羧反应.该反应操作简便,原料易得,且在反应中无需使用任何过渡金属试剂,具有一定的实用价值.

  2. CHARACTERIZATION OF RADIATION GRAFT COPOLYMER OF INORGANIC COMPOUND ONTO ALKENE

    Institute of Scientific and Technical Information of China (English)

    ZhangWanxi; CheJitai; 等

    1995-01-01

    In this paper,the radiation graft copolymer of MgO,SiO2 and Y-molecular sieve onto organic compounds,such as methacrylate,styrene and acrylomitrile obtained by per-radiation method were characterized by X-ray diffraction,pyrolysis gas chromatography,GPC and X-ray photoelectron spectroscopy.

  3. Phosphotungstate-Based Ionic Silica Nanoparticles Network for Alkenes Epoxidation

    Directory of Open Access Journals (Sweden)

    Xiaoting Li

    2015-12-01

    Full Text Available An inorganic-organic porous silica network catalyst was prepared by linking silica nanoparticles using ionic liquid and followed by anion-exchange with phosphotungstate. Characterization methods of FT-IR, TG, SEM, TEM, BET, etc., were carried out to have a comprehensive insight into the catalyst. The catalyst was used for catalyzing cyclooctene epoxidation with high surface area, high catalytic activity, and convenient recovery. The conversion and selectivity of epoxy-cyclooctene could both reach over 99% at 70 °C for 8 h using hydrogen peroxide (H2O2 as an oxidant, and acetonitrile as a solvent when the catalyst was 10 wt. % of cyclooctene.

  4. Rhodium catalysed hydroformylation of alkenes using highly fluorophilic phosphines.

    Science.gov (United States)

    Adams, Dave J; Bennett, James A; Cole-Hamilton, David J; Hope, Eric G; Hopewell, Jonathan; Kight, Jo; Pogorzelec, Peter; Stuart, Alison M

    2005-12-21

    Highly fluorophilic phosphines incorporating at least one aromatic ring containing two directly attached perfluoroalkyl groups have been synthesised, their partition coefficients (organic phase : fluorous phase) measured and their electronic properties probed using (1)J(PtP) data for their trans-[PtCl(2)L(2)] complexes. These phosphines have been used as modifying ligands for the rhodium catalysed hydroformylation of 1-octene in perfluorocarbon solvents. Catalyst activity, regioselectivity and the levels of rhodium leaching to the product phase vary with the substitution patterns of the modifying ligands that do not correlate with the electronic properties or partition coefficients of these ligands, but can be interpreted in terms of differences in the resting states of the catalysts. PMID:16311639

  5. Modification of inorganic surface with 1-alkenes and 1-alkynes

    NARCIS (Netherlands)

    Maat, ter J.

    2012-01-01

    Surface modification is important because it allows the tuning of surface properties, thereby enabling new applications of a material. It can change physical properties such as wettability and friction, but can also introduce chemical functionalities and binding specificity. Several techniques are a

  6. Reinvestigation of a Catalytic, Enantioselective Alkene Dibromination and Chlorohydroxylation.

    Science.gov (United States)

    Denmark, Scott E; Carson, Nessa

    2015-12-01

    Attempts to reproduce eight, putative, enantioselective dibromination and chlorohydroxylation reactions from oft-cited literature studies are described. The reactions were performed with full fidelity to the original report wherever possible. Analysis of the enantiomeric composition was performed by chiral stationary phase HPLC or SFC (CSP-HPLC or CSP-SFC), as opposed to the original report, which used chiral shift reagent NMR spectroscopy. After careful study, the reported levels of enantioselectivity were found to be incorrect. Possible explanations for the false positive results are discussed. PMID:26566099

  7. Reinvestigation of a Catalytic, Enantioselective Alkene Dibromination and Chlorohydroxylation

    OpenAIRE

    Denmark, Scott E.; Carson, Nessa

    2015-01-01

    Attempts to reproduce eight, putative, enantioselective dibromination and chlorohydroxylation reactions from oftcited literature studies are described. The reactions were performed with full fidelity to the original report wherever possible. Analysis of the enantiomeric composition was performed by chiral stationary phase HPLC or SFC (CSP-HPLC or CSP-SFC), as opposed to the original report, which used chiral shift reagent NMR spectroscopy. After careful study, the reported levels of enantiose...

  8. Vicinal Diamination of Alkenes under Rh-Catalysis

    OpenAIRE

    Olson, David E.; Su, Justin Y.; Roberts, D. Allen; Du Bois, J.

    2014-01-01

    The synthesis of 1,2-diamines has been achieved through a single-step, tandem sequence involving Rh-catalyzed aziridination followed by NaI-promoted rearrangement to an isomeric cyclic sulfamide. Facile ring opening of these products in hot water and pyridine affords differentially protected vicinal diamines. Demonstration of the utility of this method for the syntheses of (±)-enduracididine and (±)-allo-enduracididine is highlighted.

  9. Synthesis of fluorinated brassinosteroids based on alkene cross-metathesis

    Czech Academy of Sciences Publication Activity Database

    Slavíková, Barbora; Eignerová, Barbara; Kotora, Martin

    Karpacz : Institute of Organic Chemistry Polish Academy of Sciences, 2009. P06-P06. [Conference on Advances in Organic Synthesis /22./ Conference on Isoprenoids. 08.07.2009-12.09.2009, Karpacz] R&D Projects: GA AV ČR IAA400550609 Institutional research plan: CEZ:AV0Z40550506 Keywords : steroids * cross-metathesis * perfluoralkylation Subject RIV: CC - Organic Chemistry

  10. Fast and Green Microwave-Assisted Conversion of Essential Oil Allylbenzenes into the Corresponding Aldehydes via Alkene Isomerization and Subsequent Potassium Permanganate Promoted Oxidative Alkene Group Cleavage

    DEFF Research Database (Denmark)

    Luu, Thi Xuan Thi; Lam, Trinh To; Le, Thach Ngoc;

    2009-01-01

    oxidation of the latter to the corresponding benzaldehyde by KMnO4/CuSO4 center dot 5H(2)O. The assistance by microwave irradiation results in very short reaction times (<15 minutes). The green conversion of eugenol (4-allyl-2-methoxyphenol) into vanillin (4-hydroxy-3-methoxybenzaldehyde) has been carried...... out in a similar way, requiring however two additional microwave-assisted synthetic steps for acetylation of the hydroxy group prior to the oxidation reaction, and for the final deacetylation of vanillin acetate (4-acetoxy-3-methoxybenzaldehyde) by KF/Al2O3 under solvent-free conditions, respectively....

  11. Selective oxidation of alkanes and/or alkenes to valuable oxygenates

    Science.gov (United States)

    Lin, Manhua; Pillai, Krishnan S.

    2011-02-15

    A catalyst, its method of preparation and its use for producing at least one of methacrolein and methacrylic acid, for example, by subjecting isobutane or isobutylene or a mixture thereof to a vapor phase catalytic oxidation in the presence of air or oxygen. In the case where isobutane alone is subjected to a vapor phase catalytic oxidation in the presence of air or oxygen, the product is at least one of isobutylene, methacrolein and methacrylic acid. The catalyst comprises a compound having the formula A.sub.aB.sub.bX.sub.xY.sub.yZ.sub.zO.sub.o wherein A is one or more elements selected from the group of Mo, W and Zr, B is one or more elements selected from the group of Bi, Sb, Se, and Te, X is one or more elements selected from the group of Al, Bi, Ca, Ce, Co, Fe, Ga, Mg, Ni, Nb, Sn, W and Zn, Y is one or more elements selected from the group of Ag, Au, B, Cr, Cs, Cu, K, La, Li, Mg, Mn, Na, Nb, Ni, P, Pb, Rb, Re, Ru, Sn, Te, Ti, V and Zr, and Z is one or more element from the X or Y groups or from the following: As, Ba, Pd, Pt, Sr, or mixtures thereof, and wherein a=1, 0.05

  12. Enhancement of Alkene Epoxidation Activity of Titanosilicates by Gas-Phase Ammonia Modification

    Institute of Scientific and Technical Information of China (English)

    张里艳; 徐乐; 孙晶晶; 蒋金刚; 刘月明; 吴海虹; 吴鹏

    2012-01-01

    Novel ammonia-treated titanosilicates have been prepared by heating the samples of Ti-MWW, TS-l and Ti-Beta under pure ammonia gas flow at 673 K for a period of time. The ammonia modification improved their catalytic performance in liquid-phase oxidations. Especially, the catalytic activities of ammonified Ti-MWW, N-Ti-MWW, were enhanced greatly in the epoxidation of 1-hexene with H2O2. The reason that the ammonia treat- ment played such an important role in post-modification of titanosilicate was investigated in details. In comparison to the parent Ti-MWW catalyst, N-Ti-MMW was more robust and produced less coke in oxidation reactions.

  13. MECHANISTIC STUDIES ON THE VITAMIN B12-CATALYZED DECHLORINATION OF CHLORINATED ALKENES. (U915562)

    Science.gov (United States)

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  14. Decomposition pathways of the excited Criegee intermediates in the ozonolysis of simple alkenes

    Science.gov (United States)

    Horie, O.; Moortgat, G. K.

    Ozonolysus of C 2H 4, C 3H 6, and trans-2-C 4H 8 was carried out at 758 ± 4 Torr and 297 ± 3 K in a 2 ℓ continuous-stirred tank-reactor coupled to a matrix-isolation FTIR spectrometer through molecular-beam sampling. The branching ratios of the decomposition channels of the activated Criegee intermediates CH 2OO ∗ and CH 3CHOO ∗ formed in the primary reactions were determined by means of a computer simulation based on the quantitative analysis of CH 3CHO, HCHO, CO 2, CO, CH 4, CH 3OH, HCOOH, and CH 3COOH. The fractions of the decomposition channels found are for CH2OO ∗: CO+H 2O 58%, CO 2+H 2 24%, CO 2+2H 18%, and for CH3CHOO∗: CH4+ CO2 30% , CH 3+CO 2+H 30%, CH 3+CO+OH 28%, CH 3OH+CO 12%. The results of the ozonolysis of C 3H 6 are described by combining the simulation models of the C 2H 4 and trans-2-C 4H 8 ozonolysis. The primary propene ozonide is found to split into CH3CHOO∗+ HCHO and CH2OO∗+ CH3CHO with the fraction of 62 and 38%, respectively.

  15. Two Metals Are Better Than One in the Gold Catalyzed Oxidative Heteroarylation of Alkenes

    OpenAIRE

    Tkatchouk, Ekaterina; Mankad, Neal P.; Benitez, Diego; Goddard, William A.; Toste, F. Dean

    2011-01-01

    We present a detailed study of the mechanism for oxidative heteroarylation, based on DFT calculations and experimental observations. We propose binuclear Au(II)–Au(II) complexes to be key intermediates in the mechanism for gold catalyzed oxidative heteroarylation. The reaction is thought to proceed via a gold redox cycle involving initial oxidation of Au(I) to binuclear Au(II)–Au(II) complexes by Selectfluor, followed by heteroauration and reductive elimination. While it is tempting to invoke...

  16. Chemotactic behavior of deep subsurface bacteria toward carbohydrates, amino acids and a chlorinated alkene

    Energy Technology Data Exchange (ETDEWEB)

    Lopez de Victoria, G. (Puerto Rico Univ., Rio Piedras (Puerto Rico). Dept. of Biology)

    1989-02-01

    The chemotactic behavior of deep terrestrial subsurface bacteria toward amino acids, carbohydrates and trichloroethylene was assayed using a modification of the capillary method and bacterial enumeration by acridine orange direct counts. Eleven isolates of bacteria isolated from six different geological formations were investigated. A bimodal response rather than an absolute positive or negative response was observed in most assays. Most of the isolates were positively chemotactic to low concentrations of substrates and were repelled by high concentrations of the same substrate. However, this was not the case for trichloroethylene (TCE) which was mostly an attractant and elicited the highest responses in all the isolates when compared with amino acids and carbohydrates. The movement rates of these isolates in aseptic subsurface sediments in the absence and presence of TCE were also determined using a laboratory model. All of the isolates showed distinct response range, peak, and threshold concentrations when exposed to the same substrates suggesting that they are possibly different species as has been inferred from DNA homology studies. 101 refs., 4 figs., 57 tabs.

  17. Mcm-41 Anchored Schrock catalysts - activity in alkene metathesis and ring-opening metathesis polymerization

    Czech Academy of Sciences Publication Activity Database

    Balcar, Hynek; Sedláček, J.; Žilková, Naděžda

    Luboń : Adam Mickiewicz University, 2005 - (Lis, J.; Macina, A.; Pietraszuk, C.; Waehner, J.). s. 64 [International Symposium on Olefin Metathesis and Related Chemistry /16./. 7.8. - 12.8. 2005, Poznań] R&D Projects: GA ČR ga203/05/2194 Institutional research plan: CEZ:AV0Z40400503 Keywords : physical chemistry * catalysis * molybdenum Subject RIV: CF - Physical ; Theoretical Chemistry

  18. Rapid Metal -free Macromolecular Coupling via in situ Nitrile Oxide-Activated Alkene Cycloaddition

    OpenAIRE

    Isaacman, Michael J.; Cui, Weibin; Theogarajan, Luke S.

    2014-01-01

    Nitrile oxide 1,3 dipolar cycloaddition is a simple and powerful coupling methodology. However, the self-dimerization of nitrile oxides has prevented the widespread use of this strategy for macromolecular coupling. By combining an in situ nitrile oxide generation with a highly reactive activated dipolarophile, we have overcome these obstacles and present a metal-free macromolecular coupling strategy for the modular synthesis of several ABA triblock copolymers. Nitrile oxides were generated in...

  19. Alkene Dioxygenation with Malonoyl Peroxides: Synthesis of γ-Lactones, Isobenzofuranones, and Tetrahydrofurans.

    Science.gov (United States)

    Alamillo-Ferrer, Carla; Karabourniotis-Sotti, Marianna; Kennedy, Alan R; Campbell, Matthew; Tomkinson, Nicholas C O

    2016-07-01

    Treatment of homoallylic alcohols or carboxylic acids with malonoyl peroxide 1 provides a stereoselective method for the preparation of tetrahydrofurans, γ-lactones, and isobenzofuranones in 44-82% yield and up to 27:1 trans selectivity. Application of this simple and effective heterocyclization in the synthesis of the antidepressant citalopram is also described. PMID:27314605

  20. "富勒烯"不是烯%Fullerene is not a member of Alkene

    Institute of Scientific and Technical Information of China (English)

    王永年

    1997-01-01

    @@1996年诺贝尔化学奖得主是10年前发现Fullerene的三位化学家。Fullerene国内译为"富勒烯"。对于科学名词,笔者按习惯采用国内的名称。但是,基于《化学通报》读者都能明白的原因,这次应约为香港中文报章撰文介绍有关问题时,破例地改称"富勒碳球"。 根据有机化学系统命名的原则,英文词尾-ene译为"烯",表示含双键的烃。而Fullerene一类物质的确富含碳碳双键,也具有这种键的某些通性。但是,Fullerene只是纯元素碳的一种存在的形态;是一种单质,而不是化合物,更不是有机化合物。

  1. Efficient Preparation of TMSCCl2 Br and Its Use in Dichlorocyclopropanation of Electron-Deficient Alkenes.

    Science.gov (United States)

    Lee, Darren S; Durán-Peña, María Jesús; Burroughs, Laurence; Woodward, Simon

    2016-05-23

    The reaction of excess TMSCl and LiCCl2 Br at low temperature is a technically simple high yield route to TMSCCl2 Br. The latter is a stable source of the dichlorobromomethide carbanion, which undergoes 1,4-addition with cyclic nitroalkenes and (E)-fumarates leading to dichlorocyclopropanes after bromide expulsion. For nitrostyrenes the reaction arrests at the 1,4-addition product. Low temperature NMR spectroscopy studies and DFT calculations suggest the formation of an "ate" species [(nitronate)SiFMe3 ](-) which, upon boil-off of TMSF at 10-20 °C, yields the cyclopropane. DFT calculations also support the experimental differences between fluoride and acetate as promotors. PMID:27112785

  2. Calcium-mediated hydroboration of alkenes : "Trojan horse" or "true" catalysis?

    NARCIS (Netherlands)

    Harder, Sjoerd; Spielmann, Jan

    2012-01-01

    The hydroboration of 1,1-diphenylethylene (DPE) with catecholborane (HBcat) proceeds at 100 degrees C. For conversion at room temperature three different organocalcium catalysts have been investigated: the calcium hydride complex [DIPPnacnacCaH center dot(THF)](2) (1, DIPPnacnac CH{(CMe)(2,6-iPr(2)C

  3. PALLADIUM-CATALYZED OXIDATION OF STYRENE AND ALKENES IN PRESENCE OF IONIC LIQUIDS (WACKER REACTION)

    Science.gov (United States)

    The use of ionic liquids in various synthetic transformations is gaining significance due to the enhanced reaction rates, potential for recycling and compatibility with various organic compounds and organometallic catalysts. Palladium-catalyzed oxidation of styrene and other alk...

  4. Unsaturated aldehydes as alkene equivalents in the Diels-Alder reaction

    DEFF Research Database (Denmark)

    Taarning, Esben; Madsen, Robert

    2008-01-01

    A one-pot procedure is described for using alpha,beta-unsaturated aldehydes as olefin equivalents in the Diels-Alder reaction. The method combines the normal electron demand cycloaddition with aldehyde dienophiles and the rhodium-catalyzed decarbonylation of aldehydes to afford cyclohexenes with no...

  5. Storable Arylpalladium(II) Reagents for Alkene Labeling in Aqueous Media

    OpenAIRE

    Simmons, Rebecca L.; Yu, Robert T.; Myers, Andrew G.

    2011-01-01

    We show that arylpalladium(II) reagents linked to biotin and indocyanine dye residues can be prepared by decarboxylative palladation of appropriately substituted electron-rich benzoic acid derivatives. When prepared under the conditions described, these organometallic intermediates are tolerant of air and water, can be stored for several months in solution in dimethylsulfoxide, and permit biotin- and indocyanine dye-labeling of functionally complex olefinic substrates in water by Heck-type co...

  6. Catalytic asymmetric synthesis of a tertiary benzylic carbon center via phenol-directed alkene hydrogenation.

    Science.gov (United States)

    Caille, Seb; Crockett, Rich; Ranganathan, Krishnakumar; Wang, Xiang; Woo, Jacqueline C S; Walker, Shawn D

    2011-07-01

    An expeditious synthetic approach to chiral phenol 1, a key building block in the preparation of a series of drug candidates, is reported. The strategy includes a cost-effective and readily scalable route to cyclopentanone 3 from isobutyronitrile (10). The sterically hindered and enolizable ketone 3 was subsequently employed in a challenging Grignard addition mediated by LaCl(3)·2LiCl. A novel preparation of the lanthanide reagent required for this transformation is described. To complete the process, a highly enantioselective hydrogenation step afforded the target (1). The importance of the phenol group to the success of this asymmetric transformation is discussed. PMID:21630712

  7. Effects of chemical complexity on the autoxidation mechanisms of endocyclic alkene ozonolysis products

    DEFF Research Database (Denmark)

    Rissanen, Matti P.; Kurtén, Theo; Sipilä, Mikko; Thornton, Joel A.; Kausiala, Oskari; Garmash, Olga; Kjærgaard, Henrik Grum; Petäjä, Tuukka; Worsnop, Douglas R.; Ehn, Mikael; Kulmala, Markku

    2015-01-01

    , enabling more oxygen molecules to attach to the carbon backbone. Dimer distributions are proposed to form by homogeneous peroxy radical recombination and cross combination reactions. These conclusions were supported by experiments where H atoms were exchanged to D atoms by addition of D2O to the...... (NO3-) based ionization scheme. The experiments were performed in borosilicate glass flow tube reactors at room temperature (T = 293 ± 3 K) and at ambient pressure. An ensemble of oxidized monomer and dimer products was detected, with elemental compositions obtained from the high......-resolution mass spectra. The monomer product distributions have O/C ratios from 0.8 to 1.6 and can be explained with an autocatalytic oxidation mechanism (=autoxidation) where the oxygen-centered peroxy radical (RO2) intermediates internally rearrange by intramolecular hydrogen shift reactions...

  8. Studies on the Reactions of Fluoroalkylazides with Electron-deficient Alkenes

    Institute of Scientific and Technical Information of China (English)

    SUN,Qing-Rui; CHEN,Zi-Xian; LI,Shan; WU,Yong-Ming; TIAN,Wei-Sheng

    2008-01-01

    The 1,3-dipolar cycloaddition of fluoroalkylazides with electron deficient olefins was studied. A series of fluoroalkylated triazoline and pyrazolines were synthesized by this method. A ring opening and diazo intermediate mechanism was proposed.

  9. Katalytické krakování vyšších alkenů

    Czech Academy of Sciences Publication Activity Database

    Kolena, J.; Morávek, P.; Bortnovskij, O.; Gonsiorová, O.; Tukač, V.; Hanika, Jiří

    2003-01-01

    Roč. 45, 3-4 (2003), s. 66-69. ISSN 1335-7727 R&D Projects: GA MŠk LN00B142 Institutional research plan: CEZ:AV0Z4072921 Keywords : higher olefins * propylene * cracking Subject RIV: CI - Industrial Chemistry, Chemical Engineering

  10. Organoselenium-catalyzed, hydroxy-controlled regio- and stereoselective amination of terminal alkenes: efficient synthesis of 3-amino allylic alcohols.

    Science.gov (United States)

    Deng, Zhimin; Wei, Jialiang; Liao, Lihao; Huang, Haiyan; Zhao, Xiaodan

    2015-04-17

    An efficient route to prepare 3-amino allylic alcohols in excellent regio- and stereoselectivity in the presence of bases by orangoselenium catalysis has been developed. In the absence of bases α,β-unsaturated aldehydes were formed in up to 97% yield. Control experiments reveal that the hydroxy group is crucial for the direct amination. PMID:25849818

  11. Copper-Catalyzed Coupling of 2-Siloxy-1-alkenes and Diazocarbonyl Compounds: Approach to Multisubstituted Furans, Pyrroles, and Thiophenes.

    Science.gov (United States)

    Tan, Wei Wen; Yoshikai, Naohiko

    2016-07-01

    We report herein copper(II)-catalyzed cyclization reactions of silyl enol ethers derived from methyl ketones with α-diazo-β-ketoesters or α-diazoketones to afford 2-siloxy-2,3-dihydrofuran derivatives or 2,3,5-trisubstituted furans, respectively, under mild conditions. The former cyclization products serve as versatile 1,4-diketone surrogates, allowing facile preparation of 2,3,5-trisubstituted furans, pyrroles, and thiophenes. PMID:27259097

  12. Transition metal-catalyzed oxidative double bond cleavage of simple and bio-derived alkenes and unsaturated fatty acids

    NARCIS (Netherlands)

    Spannring, Peter; Bruijnincx, Pieter C. A.; Weckhuysen, Bert. M.; Klein Gebbink, Bert

    2014-01-01

    The oxidative cleavage of the C=C double bond in unsaturated fatty acids into aldehydes or carboxylic acids is a reaction of current interest in biomass valorization. The products of this reaction, which is currently being performed on an industrial scale by means of ozonolysis, can be applied for t

  13. Beyond the use of modifiers in selective alkyne hydrogenation: silver and gold nanocatalysts in flow mode for sustainable alkene production

    Science.gov (United States)

    Vilé, Gianvito; Pérez-Ramírez, Javier

    2014-10-01

    We report on the excellent stereo and chemoselectivity of nanosized silver and gold catalysts in the three-phase hydrogenation of acetylenic compounds under flow chemistry conditions. The materials featuring metal nanoparticles in the range of 2-21 nm were prepared by spray deposition or incipient wetness impregnation of silver nitrate and sol immobilisation of gold chloride on different carriers (Al2O3, SiO2, TiO2, and carbon), followed by activation in various atmospheres. The samples were characterised by ICP-OES, N2 sorption, XPS, HAADF-STEM, and HRTEM, and evaluated in a continuous-flow flooded-bed micro-reactor. Both metals display optimal activities for particles below 5 nm, enabling stable operation at T = 373 K and P = 10 bar. While the performance of the silver catalysts is less influenced by the support, the gold nanoparticles exhibit significant activity only when deposited on TiO2, likely due to the strong metal-support interaction. Hydrogenations of functionalised alkynes reveal that silver and gold match, and in some cases exceed, the selectivity of benchmark palladium-based catalysts. Furthermore, in contrast to Pd, the Ag and Au samples require no modifiers, which brings fundamental and practical simplifications for their understanding and large scale manufacture. Therefore, these materials could be advantageously used for the continuous production of olefinic intermediates in the fine chemical and pharmaceutical industries.We report on the excellent stereo and chemoselectivity of nanosized silver and gold catalysts in the three-phase hydrogenation of acetylenic compounds under flow chemistry conditions. The materials featuring metal nanoparticles in the range of 2-21 nm were prepared by spray deposition or incipient wetness impregnation of silver nitrate and sol immobilisation of gold chloride on different carriers (Al2O3, SiO2, TiO2, and carbon), followed by activation in various atmospheres. The samples were characterised by ICP-OES, N2 sorption, XPS, HAADF-STEM, and HRTEM, and evaluated in a continuous-flow flooded-bed micro-reactor. Both metals display optimal activities for particles below 5 nm, enabling stable operation at T = 373 K and P = 10 bar. While the performance of the silver catalysts is less influenced by the support, the gold nanoparticles exhibit significant activity only when deposited on TiO2, likely due to the strong metal-support interaction. Hydrogenations of functionalised alkynes reveal that silver and gold match, and in some cases exceed, the selectivity of benchmark palladium-based catalysts. Furthermore, in contrast to Pd, the Ag and Au samples require no modifiers, which brings fundamental and practical simplifications for their understanding and large scale manufacture. Therefore, these materials could be advantageously used for the continuous production of olefinic intermediates in the fine chemical and pharmaceutical industries. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr02777a

  14. Theoretical Insights into the Chemistry of Organometallic Compounds with C2 p-ligands: Alkenes and Alkynes

    OpenAIRE

    Carbó Martín, Jorge Juan

    2002-01-01

    Consultable des del TDX Títol obtingut de la portada digitalitzada Els compostos de metalls de transició presenten una amplia varietat d'estructures, juntament amb una gran diversitat de propietats i de química. Aquesta diversitat ofereix abundants oportunitats per la seva aplicació en síntesi orgànica i en processos de catàlisi selectiva. No obstant, la gran varietat de la química organometàl·lica implica un augment de la complexitat del seu estudi. Aquestes característiques dels compo...

  15. Synthesis and Application of Chiral Spiro Cp Ligands in Rhodium-Catalyzed Asymmetric Oxidative Coupling of Biaryl Compounds with Alkenes.

    Science.gov (United States)

    Zheng, Jun; Cui, Wen-Jun; Zheng, Chao; You, Shu-Li

    2016-04-27

    The vastly increasing application of chiral Cp ligands in asymmetric catalysis results in growing demand for novel chiral Cp ligands. Herein, we report a new class of chiral Cp ligands based on 1,1'-spirobiindane, a privileged scaffold for chiral ligands and catalysts. The corresponding Rh complexes are shown to be excellent catalysts in asymmetric oxidative coupling reactions, providing axially chiral biaryls in 19-97% yields with up to 98:2 er. PMID:27070297

  16. Ruthenium complexes with N/C-donor ligands redox catalysts for water oxidation and the epoxidation of alkenes

    OpenAIRE

    Aguiló Carreras, Joan

    2013-01-01

    The understanding of the water oxidation reaction to molecular oxygen is still one of the great challenges faced by scientific community. On the other hand the epoxidation of olefins is a reaction of high relevance in both industry and academia. Epoxides are important intermediates in the chemical industry, particularly for the synthesis of various polymers and fine chemicals, such as pharmaceuticals, food additives, or flavor and fragrance compounds. Mononuclear and dinuclear Ru aqua complex...

  17. The Oxidation of Terminal Alkenes by Permanganate: A Practical Demonstration of the Use of Phase Transfer Agents.

    Science.gov (United States)

    Brown, Keith C.; And Others

    1982-01-01

    Use of phase transfer agents to facilitate/accelerate chemical reactions has become an established practice, particularly in organic chemistry. Describes an undergraduate laboratory procedure demonstrating the principles involved in the use of said agents. Includes student results from phase transfer assisted permanganate oxidations. (Author/JN)

  18. Organoselenium and DMAP co-catalysis: regioselective synthesis of medium-sized halolactones and bromooxepanes from unactivated alkenes.

    Science.gov (United States)

    Verma, Ajay; Jana, Sadhan; Prasad, Ch Durga; Yadav, Abhimanyu; Kumar, Sangit

    2016-03-18

    A catalytic system consisting of bis(4-methoxyphenyl)selenide and 4-(dimethylamino)pyridine (DMAP) has been developed for the regioselective synthesis of medium-sized bromo/iodo lactones and bromooxepanes possessing high transannular strain. (77)Se NMR, mass spectrometry and theoretical studies reveal that the reaction proceeds via a quaternary selenium intermediate. PMID:26906914

  19. Synthesis-Structure–Function Relationships of Silica-Supported Niobium(V) Catalysts for Alkene Epoxidation with H 2 O 2

    Energy Technology Data Exchange (ETDEWEB)

    Thornburg, Nicholas E.; Nauert, Scott L.; Thompson, Anthony B.; Notestein, Justin M.

    2016-08-12

    Many industrially significant selective oxidation reactions are catalyzed by supported and bulk transition metal oxides. Catalysts for the synthesis of oxygenates, and especially for epoxidation, have predominantly focused on TiOx supported on or co-condensed with SiO2, whereas much of the rest of Groups 4 and 5 have been less studied. We have recently demonstrated through periodic trends using a uniform molecular precursor that niobium(V)-silica catalysts reveal the highest activity and selectivity for efficient utilization of H2O2 for epoxidation across all of Groups 4 and 5. In this work, we graft a wide range of Nb(V) precursors, spanning surface densities of 0.07–1.6 Nb groups nm–2 on mesoporous silica, and we characterize these materials with UV–visible spectroscopy and Nb K-edge XANES. Further, we apply in situ chemical titration with phenylphosphonic acid (PPA) in the epoxidation of cis-cyclooctene by H2O2 to probe the numbers and nature of the active sites across this series and in a set of related Ti-, Zr-, Hf-, and Ta-SiO2 catalysts. By this method, the fraction of kinetically relevant NbOx species ranges from ~15% to ~65%, which correlates with spectroscopic evaluation of the NbOx sites. This titration leads to a single value for the average turnover frequency, on a per active site basis rather than a per Nb atom basis, of 1.4 ± 0.52 min–1 across the 21 materials in the series. These quantitative maps of structural properties and kinetic consequences link key catalyst descriptors of supported Nb-SiO2 to enable rational design for next-generation oxidation catalysts.

  20. The isolation of [Pd{OC(O)H}(H)(NHC)(PR3)] (NHC = N-heterocyclic carbene) and its role in alkene and alkyne reductions using formic acid

    KAUST Repository

    Broggi, Julie

    2013-03-27

    The [Pd(SIPr)(PCy3)] complex efficiently promotes a tandem process involving dehydrogenation of formic acid and hydrogenation of C-C multiple bonds using H2 formed in situ. The isolation of a key catalytic hydridoformatopalladium species, [Pd{OC(O)H}(H)(IPr)(PCy 3)], is reported. The complex plays a key role in the Pd(0)-mediated formation of hydrogen from formic acid. Mechanistic and computational studies delineate the operational role of the palladium complex in this efficient tandem sequence. © 2013 American Chemical Society.

  1. Rare-earth metal π-complexes of reduced arenes, alkenes, and alkynes: Bonding, electronic structure, and comparison with actinides and other electropositive metals

    OpenAIRE

    Huang, W.; Diaconescu, PL

    2015-01-01

    © 2015 The Royal Society of Chemistry. Rare-earth metal complexes of reduced π ligands are reviewed with an emphasis on their electronic structure and bonding interactions. This perspective discusses reduced carbocyclic and acyclic π ligands; in certain categories, when no example of a rare-earth metal complex is available, a closely related actinide analogue is discussed. In general, rare-earth metals have a lower tendency to form covalent interactions with π ligands compared to actinides, m...

  2. Development of (2-bromo-1,1,2,2-tetrafluoroethyl)(phenyl)sulfane as tetrafluoroethyl-radical and tetrafluoroethylene-diradical synthons for additions to alkenes

    Czech Academy of Sciences Publication Activity Database

    Chernykh, Yana; Beier, Petr

    2013-01-01

    Roč. 156, December (2013), s. 307-313. ISSN 0022-1139 R&D Projects: GA ČR GAP207/11/0421 Institutional support: RVO:61388963 Keywords : radical addition * sulfide * tetrafluoroethyl * tetrafluoroethylene Subject RIV: CC - Organic Chemistry Impact factor: 1.952, year: 2013

  3. Effect of multi-walled carbon nanotubes aspect ratio and temperature on the dielectric behavior of alternating alkene-carbon monoxide polyketone nanocomposites

    Science.gov (United States)

    Abu-Surrah, Adnan S.; Abdul Jawad, Saadi; Al-Ramahi, Esraa; Hallak, Awni B.; Khattari, Z.

    2015-04-01

    New alternating poly(propylene-alt-carbon monoxide/ethylene-alt-carbon monoxide) (PECO)/multiwalled carbon nanotubes (MWCNTs) composites have been prepared. Dielectric permittivity, electric modulus and ac conductivity of the isolated materials were investigated as a function of fiber aspect ratio, frequency and temperature. For aspect ratio of 30 and 200, a transition from insulator to semiconductor was observed at frequency 1×104. However, for high aspect ratio sample (660), no transition was observed and the conductivity is frequency independent in the measured frequency range of 10-106 Hz. The conductivity increases from about 1×10-4 for the sample that contain fibers of aspect ratio 30 and reaches 5×10-2 (Ω m)-1 for aspect ratio was 660. This behavior can be modeled by a circuit that consists of a contact resistance in series with a parallel combination of resistance (R) and capacitance (C). The calculated activation energy for sample filled with fibers having aspect ratio 30 is about 0.26 eV and decreases to about 0.16 eV when the aspect ratio is 660.

  4. Metallacyclobutane substitution and its effect on alkene metathesis for propylene production over W-H/Al2O3: Case of isobutene/2-butene cross-metathesis

    KAUST Repository

    Szeto, Kaï Chung

    2013-09-06

    Cross metathesis between 2-butenes and isobutene yielding the valuable products propylene and 2-methyl-2-butene has been investigated at low pressure and temperature using WH3/Al2O3, a highly active and selective catalyst. Two parallel catalytic cycles for this reaction have been proposed where the cycle involving the less sterically hindered tungstacyclobutane intermediates is most likely favored. Moreover, it has been found that the arrangement of substituents on the least thermodynamically favored tungstacyclobutane governs the conversion rate of the cross metathesis reaction for propylene production from butenes and/or ethylene. © 2013 American Chemical Society.

  5. Formation of highly oxidized multifunctional compounds: autoxidation of peroxy radicals formed in the ozonolysis of alkenes - deduced from structure-product relationships

    Science.gov (United States)

    Mentel, T. F.; Springer, M.; Ehn, M.; Kleist, E.; Pullinen, I.; Kurtén, T.; Rissanen, M.; Wahner, A.; Wildt, J.

    2015-06-01

    It has been postulated that secondary organic particulate matter plays a pivotal role in the early growth of newly formed particles in forest areas. The recently detected class of extremely low volatile organic compounds (ELVOC) provides the missing organic vapors and possibly contributes a significant fraction to atmospheric SOA (secondary organic aerosol). The sequential rearrangement of peroxy radicals and subsequent O2 addition results in ELVOC which are highly oxidized multifunctional molecules (HOM). Key for efficiency of such HOM in early particle growth is that their formation is induced by one attack of the oxidant (here O3), followed by an autoxidation process involving molecular oxygen. Similar mechanisms were recently observed and predicted by quantum mechanical calculations e.g., for isoprene. To assess the atmospheric importance and therewith the potential generality, it is crucial to understand the formation pathway of HOM. To elucidate the formation path of HOM as well as necessary and sufficient structural prerequisites of their formation we studied homologous series of cycloalkenes in comparison to two monoterpenes. We were able to directly observe highly oxidized multifunctional peroxy radicals with 8 or 10 O atoms by an Atmospheric Pressure interface High Resolution Time of Flight Mass Spectrometer (APi-TOF-MS) equipped with a NO3--chemical ionization (CI) source. In the case of O3 acting as an oxidant, the starting peroxy radical is formed on the so-called vinylhydroperoxide path. HOM peroxy radicals and their termination reactions with other peroxy radicals, including dimerization, allowed for analyzing the observed mass spectra and narrowing down the likely formation path. As consequence, we propose that HOM are multifunctional percarboxylic acids, with carbonyl, hydroperoxy, or hydroxy groups arising from the termination steps. We figured that aldehyde groups facilitate the initial rearrangement steps. In simple molecules like cycloalkenes, autoxidation was limited to both terminal C atoms and two further C atoms in the respective α positions. In more complex molecules containing tertiary H atoms or small, constrained rings, even higher oxidation degrees were possible, either by simple H shift of the tertiary H atom or by initialization of complex ring-opening reactions.

  6. Impact of chamber wall loss of gaseous organic compounds on secondary organic aerosol formation: explicit modeling of SOA formation from alkane and alkene oxidation

    OpenAIRE

    Y. S. La; Camredon, M; Ziemann, P. J.; R. Valorso; Matsunaga, A; V. Lannuque; Lee-Taylor, J.; Hodzic, A.; S. Madronich; B. Aumont

    2015-01-01

    Recent studies have shown that low volatility gas-phase species can be lost onto the smog chamber wall surfaces. Although this loss of organic vapors to walls could be substantial during experiments, its effect on secondary organic aerosol (SOA) formation has not been well characterized and quantified yet. Here the potential impact of chamber walls on the loss of gaseous organic species and SOA formation has been explored using the Generator for Explicit Chemistry and Kineti...

  7. Impact of chamber wall loss of gaseous organic compounds on secondary organic aerosol formation: explicit modeling of SOA formation from alkane and alkene oxidation

    OpenAIRE

    Y. S. La; Camredon, M; Ziemann, P. J.; R. Valorso; Matsunaga, A; V. Lannuque; Lee-Taylor, J.; Hodzic, A.; S. Madronich; B. Aumont

    2016-01-01

    Recent studies have shown that low volatility gas-phase species can be lost onto the smog chamber wall surfaces. Although this loss of organic vapors to walls could be substantial during experiments, its effect on secondary organic aerosol (SOA) formation has not been well characterized and quantified yet. Here the potential impact of chamber walls on the loss of gaseous organic species and SOA formation has been explored using the Generator for Explicit Chemistry and Kineti...

  8. Epoxidation of Alkenes with Molecular Oxygen Catalyzed by Immobilized Co(acac)2 and Co(bpy)2Cl2 Complexes within Nanoreactors of Al-MCM-41

    OpenAIRE

    Farzaneh, F; Jalalian, M; Tayebi, L.

    2012-01-01

    Cobalt complexes with different ligands such as bipyridine, and acetylacetonate were immobilized within nanoreactors of Al-MCM-41, designated as Co(acac)2/Al-MCM-41 and Co(bipy)22+/Al-MCM41. The immobilized complexes were characterized by XRD, N2-adsorption desorption, FT-IR and UV-Vis techniques. It was found that Co(bipy)22+/Al-MCM41 and Co(acac)2/Al-MCM-41 successfully catalyze the oxidation of norbornene, styrene, cis-stilbene, trans-stilbene, and cyclohexene with 68% to 100% conversion a...

  9. Synthesis of 2-Arylpyridopyrimidinones, 6-Aryluracils, and Tri- and Tetrasubstituted Conjugated Alkenes via Pd-Catalyzed Enolic C-O Bond Activation-Arylation.

    Science.gov (United States)

    Guchhait, Sankar K; Priyadarshani, Garima

    2015-06-19

    A new and efficient approach for the synthesis of biologically important 2-aryl-4H-pyrido[1,2-a]pyrimidin-4-ones and 6-aryluracils via previously unknown Pd-catalyzed enolic C-OH activation-arylation of pyridopyrimidin-2,4-diones and barbituric acids, respectively, with boronic acids is reported. The starting materials are readily available, and products are obtained in high yields. An efficient and chemo- and stereoselective access to various tri- and tetrasubstituted conjugated alkenones and alkenoates is also obtained in this arylation approach. Interestingly, the procedure for the construction of such diverse molecular frameworks is general and featured with excellent substrates scope, tolerance of a broad range of functionalities, the unusual viability of performing the reaction under open air and in aqueous cosolvent, and the amenability to a scale-up synthesis, which have been found to be common limitations in the conventional/classical routes. The application of the protocol in a simple one-step high-yield route to pharmaceutically important polyarylated pyridopyrimidinone demonstrates its further synthetic utility. PMID:25996549

  10. 40 CFR 721.6900 - Polymer of bisphenol A di-glyc-i-dal ether, substituted al-kenes, and but-a-diene.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Polymer of bisphenol A di-glyc-i-dal... SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.6900 Polymer of bisphenol A di-glyc-i... subject to reporting. (1) The chemical substances identified generically as polymer of bisphenol...

  11. Group 11 Metal Compounds with Tripodal Bis(imidazole) Thioether Ligands. Applications as Catalysts in the Oxidation of Alkenes and as Antimicrobial Agents

    OpenAIRE

    Armando Varela-Ramírez; Aguilera, Renato J; María Contel; Eunmi Hwang; Rafael Ovalle; Reema Anis; Fangwei Liu

    2011-01-01

    New group 11 metal complexes have been prepared using the previously described tripodal bis(imidazole) thioether ligand (N-methyl-4,5-diphenyl-2-imidazolyl)2C(OMe)C(CH3)2S(tert-Bu) ({BITOMe,StBu}, 2). The pincer ligand offers a N2S donor atom set that can be used to coordinate the group 11 metals in different oxidation states [AuI, AuIII, AgI, CuI and CuII]. Thus the new compounds [Au{BITOMe,StBu}Cl][AuCl4]2 (3), [Au{BITOMe,StBu}Cl] (4), [Ag{BITOMe,StBu}X] (X = OSO2CF3 − 5, PF6 − 6) and [Cu{B...

  12. Computationally Designed Zirconium Organometallic Catalyst for Direct Epoxidation of Alkenes without Allylic H Atoms: Aromatic Linkage Eliminates Formation of Inert Octahedral Complexes

    CERN Document Server

    Yang, Bo

    2016-01-01

    We used density functional theory to computationally design a Zr organometallic catalyst for selectively oxidizing substrates using molecular oxygen as oxidant without coreductant. Each selective oxidation cycle involves four general steps: (a) a peroxo or weakly adsorbed O2 group releases an O atom to substrate to form substrate oxide and an oxo group, (b) an oxygen molecule adds to the oxo group to generate an eta2-ozone group, (c) the eta2-ozone group rearranges to form an eta3-ozone group, and (d) the eta3-ozone group releases an O atom to substrate to form substrate oxide and regenerate the peroxo or weakly adsorbed O2 group. This catalyst could potentially be synthesized via the condensation reaction Zr(N(R)R')4 + 2 C6H4-1,6-(N(C6H3-2',6'-(CH(CH3)2)2)OH)2 --> Zr(C6H4-1,6-(N(C6H3-2',6'-(CH(CH3)2)2)O)2)2 [aka Zr_Benzol catalyst] + 4 N(R)(R')H where R and R' are CH3, CH2CH3, or other alkyl groups. For direct ethylene epoxidation, the computed enthalpic energetic span (i.e., effective activation energy for ...

  13. 1,3-Dipolar Cycloaddition Reactions of 1-(4-Phenylphenacyl)-1,10-phenanthrolinium N-Ylide with Activated Alkynes and Alkenes

    OpenAIRE

    A. Badoiu; Caproiu, M. T.; Draghici, C.; Caira, M. R.; Dumitrascu, F.

    2005-01-01

    The 3 2 cycloaddition reaction of 1-(4-phenylphenacyl)-1,10-phenanthrolinium ylide with activated alkynes gave pyrrolo[1,2- 4a][1,10]phenanthrolines 6a-d. The "one pot" synthesis of 6a,b,d from 4, activatedalkenes, Et3N and tetrakis-pyridine cobalt (II) dichromate (TPCD) is described. Thehelical chirality of pyrrolophenanthrolines 6b-d was put in evidence by NMRspectroscopy.

  14. Early Main Group Metal Catalysis : How Important is the Metal?

    NARCIS (Netherlands)

    Penafiel, Johanne; Maron, Laurent; Harder, Sjoerd

    2015-01-01

    Organocalcium compounds have been reported as efficient catalysts for various alkene transformations. In contrast to transition metal catalysis, the alkenes are not activated by metal-alkene orbital interactions. Instead it is proposed that alkene activation proceeds through an electrostatic interac

  15. Kinetics and mechanism of the oxidation of alkenes and silanes by hydrogen peroxide catalyzed by methylrhenium trioxide (MTO) and a novel application of electrospray mass spectrometry to study the hydrolysis of MTO

    Energy Technology Data Exchange (ETDEWEB)

    Tan, Haisong

    1999-11-08

    Conjugated dienes were oxidized by hydrogen peroxide with methylrhenium trioxide (MTO) as catalyst. Methylrhenium bis-peroxide was the major reactive catalyst present. Hydroxyalkenes and trisubstituted silane were also tested. Mechanisms for each of these reactions are presented.

  16. Valence excitation energies of alkenes, carbonyl compounds, and azabenzenes by time-dependent density functional theory: Linear response of the ground state compared to collinear and noncollinear spin-flip TDDFT with the Tamm-Dancoff approximation

    Science.gov (United States)

    Isegawa, Miho; Truhlar, Donald G.

    2013-04-01

    Time-dependent density functional theory (TDDFT) holds great promise for studying photochemistry because of its affordable cost for large systems and for repeated calculations as required for direct dynamics. The chief obstacle is uncertain accuracy. There have been many validation studies, but there are also many formulations, and there have been few studies where several formulations were applied systematically to the same problems. Another issue, when TDDFT is applied with only a single exchange-correlation functional, is that errors in the functional may mask successes or failures of the formulation. Here, to try to sort out some of the issues, we apply eight formulations of adiabatic TDDFT to the first valence excitations of ten molecules with 18 density functionals of diverse types. The formulations examined are linear response from the ground state (LR-TDDFT), linear response from the ground state with the Tamm-Dancoff approximation (TDDFT-TDA), the original collinear spin-flip approximation with the Tamm-Dancoff (TD) approximation (SF1-TDDFT-TDA), the original noncollinear spin-flip approximation with the TDA approximation (SF1-NC-TDDFT-TDA), combined self-consistent-field (SCF) and collinear spin-flip calculations in the original spin-projected form (SF2-TDDFT-TDA) or non-spin-projected (NSF2-TDDFT-TDA), and combined SCF and noncollinear spin-flip calculations (SF2-NC-TDDFT-TDA and NSF2-NC-TDDFT-TDA). Comparing LR-TDDFT to TDDFT-TDA, we observed that the excitation energy is raised by the TDA; this brings the excitation energies underestimated by full linear response closer to experiment, but sometimes it makes the results worse. For ethylene and butadiene, the excitation energies are underestimated by LR-TDDFT, and the error becomes smaller making the TDA. Neither SF1-TDDFT-TDA nor SF2-TDDFT-TDA provides a lower mean unsigned error than LR-TDDFT or TDDFT-TDA. The comparison between collinear and noncollinear kernels shows that the noncollinear kernel drastically reduces the spin contamination in the systems considered here, and it makes the results more accurate than collinear spin-flip TDDFT for functionals with a low percentage of Hartree-Fock exchange and sometimes for functionals with a higher percentage of Hartree-Fock exchange, but it yields less accurate results than ground-state TDDFT.

  17. 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).

  18. Synthesis and Characterization of Bis-benzyl and Bis-allyl Complexes of Titanium(III) and Vanadium(III); Catalytic Isomerization of Alkenes with CpV(η3-C3H5)2

    OpenAIRE

    Nieman, J.; Pattiasina, J.W.; Teuben, J.H.

    1984-01-01

    Reactions of CpTiCl2 (Cp = η5-C5H5) with RMgX (X = Cl, Br) yield the complexes CpTiR2 (R = CH2Ph, η3-C3H5). The complex Cp*Ti(η3-C3H5)2 (Cp* = η5-C5Me5) was prepared analogously from Cp*TiCl2(THF). CpVCl2(PEt3)2 and Cp´VCl2(PEt3)2 (Cp´ = η5-C5H4Me) were used for the preparation of CpV(CH2Ph)2, CpV(η3-C3H5)2, CpV(η3-1-MeC3H4)2 and Cp´V(η3-C3H5)2, respectively. The corresponding Cp*V derivatives could not be obtained. The reaction of CpCrCl2(thf) with C3H5MgCl gives a dimeric complex [CpCr(C3H5...

  19. Maghemite decorated with ultra-small palladium nanoparticles (γ-Fe2O3–Pd): applications in the Heck–Mizoroki olefination, Suzuki reaction and allylic oxidation of alkenes

    Science.gov (United States)

    A nanocatalyst comprising ultra-small Pd/PdO nanoparticles (<5 nm) supported on maghemite was prepared by a co-precipitation protocol using inexpensive raw materials and was deployed successfully in various significant synthetic transformations, namely the Heck–Mizoroki olefinati...

  20. Intermolecular Dehydrative Coupling Reaction of Arylketones with Cyclic Alkenes Catalyzed by a Well-Defined Cationic Ruthenium-Hydride Complex: A Novel Ketone Olefination Method via Vinyl C–H Bond Activation

    OpenAIRE

    Yi, Chae S.; Lee, Do W.

    2010-01-01

    The cationic ruthenium-hydride complex [(η6-C6H6)(PCy3)(CO)RuH]+BF4− was found to be a highly effective catalyst for the intermolecular olefination reaction of arylketones with cycloalkenes. The preliminary mechanistic analysis revealed that electrophilic ruthenium-vinyl complex is the key species for mediating both vinyl C–H bond activation and the dehydrative olefination steps of the coupling reaction.

  1. Mechanisms of flash pyrolysis of ether lipids isolated from the green microalga Botryococcus braunii race

    OpenAIRE

    Sinninghe Damsté, J.S.; Gelin, F.; Gatellier, J-P.L.A.; Metzger, P.; Derenne, S.; Largeau, C.; Leeuw, J.W. de

    1993-01-01

    Two types of ether lipids isolated from the microalga Botryococcus braunii have been subjected to flash pyrolysis. The pyrolysis products were separated and analyzed by GC/MS. The nature and distribution of the pyrolysis compounds gave clues to the different mechanisms involved in the pyrolysis of ether-linked alkyl chains. The relatively abundant presence of alkenes, alkadienes, alken-9-ones and alken-10-ones with chain lengths corresponding to those of the ether-bound alkyl chains indicated...

  2. In-situ and operando infrared investigations on supported ionic liquid- and ionic liquid crystal-based catalytic materials

    OpenAIRE

    Morain, Bruno

    2013-01-01

    Alkenes are widely used primary chemicals in petrochemical industry. Among them, the linear alpha olefins (LAO), produced by dimerization of short alkenes, are essential for polymers and for industrial surfactants. However, linear aldehydes, synthesized by hydroformylation of alkenes, are preferred over the branched ones for the production of plasticizer or detergent alcohols. To enhance the yield of linear compounds (i.e. α-olefines or aldehydes) over the branched ones, many efforts have bee...

  3. Thermoset polymers via ring opening metathesis polymerization of functionalized oils

    Science.gov (United States)

    Larock, Richard C; Henna, Phillip H; Kessier, Michael R

    2012-11-27

    The invention provides a method for producing a thermosetting resin from renewable oils, the method comprising supplying renewable oil molecules containing strained ring alkene moieties; reacting the alkene moieties with cyclic alkenes to create a polymer; and repeating the above two steps until the resin having desired characteristics are obtained. Also provided is a thermoset resin comprising functionalized renewable oil polymerized with a co-monomer.

  4. Cuticular lipids of female solitary bees, Osmia lignaria Say and Megachile rotundata (F.) (Hymenoptera: Megachilidae).

    Science.gov (United States)

    Buckner, James S; Pitts-Singer, Theresa L; Guédot, Christelle; Hagen, Marcia M; Fatland, Charlotte L; Kemp, William P

    2009-06-01

    The cuticular lipids of the cavity-nesting adult female solitary bees, Osmia lignaria Say and Megachile rotundata (F.) (Hymenoptera: Megachilidae), were analyzed by gas chromatography (GC) and combined GC-mass spectrometry. The cuticular lipids of these female bees are mainly consisted of hydrocarbons. For O. lignaria, nearly 64% of the cuticular lipids were C(25)-C(31) mono-alkenes. For M. rotundata, 48% of the cuticular lipids were C(23)-C(33) alkanes with nearly the same quantities of the same chain-length mono-alkenes (45%). For the mono-alkenes of O. lignaria, 14 mono-alkene constituents were identified, with two of these, 9-heptacosene and 7-nonacosene, comprising 67% of the total alkene distribution. For M. rotundata females, the mixtures of mono-alkenes were more complex with 26 constituents identified and quantified. For the M. rotundata mono-alkenes, 57% of the total composition consisted of the three alkenes, 7-pentacosene, 9-pentacosene and 7-heptacosene. For both bee species, small quantities of C(40)-C(48) wax esters were also characterized with the major components possessing a C(18) mono-unsaturated fatty acid (9-octadecenoate) moiety esterified to even-carbon number (C(22-30)) fatty alcohols. The possible role of these cuticular lipids as nest recognition chemicals is discussed in light of nesting behavior of managed crop pollinators. PMID:19298863

  5. Simple, Chemoselective Hydrogenation with Thermodynamic Stereocontrol

    OpenAIRE

    Iwasaki, Kotaro; Wan, Kanny K.; Oppedisano, Alberto; Crossley, Steven W. M.; Shenvi, Ryan A.

    2014-01-01

    Few methods permit the hydrogenation of alkenes to a thermodynamically favored configuration when steric effects dictate the alternative trajectory of hydrogen delivery. Dissolving metal reduction achieves this control, but with extremely low functional group tolerance. Here we demonstrate a catalytic hydrogenation of alkenes that affords the thermodynamic alkane products with remarkably broad functional group compatibility and rapid reaction rates at standard temperature and pressure.

  6. Factors influencing ring closure through olefin metathesis - A perspective

    Indian Academy of Sciences (India)

    Subrata Ghosh; Sarita Ghosh; Niladri Sarkar

    2006-05-01

    Success of ring closure reactions of substrates having two terminal alkenes through olefin metathesis depends on a number of factors such as catalysts, nature and size of the rings to be formed and the substituents/functional groups present on the alkenes as well as at the allylic position. This article presents an overview of these influencing factors with illustrative examples.

  7. Two strategies for the development of mitochondrion-targeted small molecule radiation damage mitigators

    NARCIS (Netherlands)

    Rwigema, Jean-Claude M.; Beck, Barbara; Wang, Wei; Doemling, Alexander; Epperly, Michael W.; Shields, Donna; Goff, Julie P.; Franicola, Darcy; Dixon, Tracy; Frantz, Marie-Céline; Wipf, Peter; Tyurina, Yulia; Kagan, Valerian E.; Wang, Hong; Greenberger, Joel S.

    2011-01-01

    Purpose: To evaluate the effectiveness of mitigation of acute ionizing radiation damage by mitochondrion-targeted small molecules. Methods and Materials: We evaluated the ability of nitroxide-linked alkene peptide isostere JP4-039, the nitric oxide synthase inhibitor-linked alkene peptide esostere M

  8. CHEMISTRY OF THIENOPYRIDINES .39. SYNTHESIS OF [1]BENZOTHIENO[2,3-H]ISOQUINOLINE AND RELATED STUDIES

    NARCIS (Netherlands)

    KLEMM, LH; SEVERNS, B; WYNBERG, H

    1991-01-01

    Benzo[b]thiophene-2-carboxaldehyde undergoes condensation with 4-methylpyridine and with 2-methylquinoline to produce trans-diarylethenes (52% and 76%, respectively). The former alkene photocyclizes in cyclohexane to yield [1]benzo[2,3-h]isoquinoline (35%), while the latter alkene does not give succ

  9. Organometallic chemistry: A new metathesis

    Science.gov (United States)

    Hennessy, Elisabeth T.; Jacobsen, Eric N.

    2016-08-01

    Carbonyls and alkenes, two of the most common functional groups in organic chemistry, generally do not react with one another. Now, a simple Lewis acid has been shown to catalyse metathesis between alkenes and ketones in a new carbonyl olefination reaction.

  10. Major reactive species of ambient volatile organic compounds (VOCs) and their sources in Beijing

    Institute of Scientific and Technical Information of China (English)

    SHAO Min; FU Linlin; LIU Ying; LU Sihua; ZHANG Yuanhang; TANG Xiaoyan

    2005-01-01

    Volatile organic compounds (VOCs) are important precursors of atmospheric chemical processes. As a whole mixture, the ambient VOCs show very strong chemical reactivity. Based on OH radical loss rates in the air, the chemical reactivity of VOCs in Beijing was calculated. The results revealed that alkenes, accounting for only about 15% in the mixing ratio of VOCs, provide nearly 75% of the reactivity of ambient VOCs and the C4 to C5 alkenes were the major reactive species among the alkenes. The study of emission characteristics of various VOCs sources indicated that these alkenes are mainly from vehicle exhaust and gasoline evaporation. The reduction of alkene species in these two sources will be effective in photochemical pollution control in Beijing.

  11. EFSA CEF Panel (EFSA Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids), 2013. Scientific Opinion on Flavouring Group Evaluation 216, Revision 1 (FGE.216Rev1). Consideration of genotoxic potential for α,β-unsaturated 2-Phenyl -2-Alkenals from Subgroup 3.3 of FGE.19

    DEFF Research Database (Denmark)

    Beltoft, Vibe Meister; Binderup, Mona-Lise; Lund, Pia;

    The Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids of the European Food Safety Authority was requested to evaluate the genotoxic potential of five flavouring substances from subgroup 3.3 of FGE.19. In the Flavouring Group Evaluation 216 (FGE.216) additional genotoxicity...... of animals treated with 2-phenylcrotonaldehyde. Moreover, since the substance was genotoxic only without metabolic activation, it appears necessary to prove the absence of genotoxic effect locally in the gastro intestinal system using the Comet assay....

  12. Stearoyl-acyl carrier protein desaturases are associated with floral isolation in sexually deceptive orchids

    Energy Technology Data Exchange (ETDEWEB)

    Schluter, P.M.; Shanklin, J.; Xu, S.; Gagliardini, V.; Whittle, E.; Grossniklaus, U.; Schiestl, F. P.

    2011-04-05

    The orchids Ophrys sphegodes and O. exaltata are reproductively isolated from each other by the attraction of two different, highly specific pollinator species. For pollinator attraction, flowers chemically mimic the pollinators sex pheromones, the key components of which are alkenes with different double-bond positions. This study identifies genes likely involved in alkene biosynthesis, encoding stearoyl-acyl carrier protein (ACP) desaturase (SAD) homologs. The expression of two isoforms, SAD1 and SAD2, is flower-specific and broadly parallels alkene production during flower development. SAD2 shows a significant association with alkene production, and in vitro assays show that O. sphegodes SAD2 has activity both as an 18:0-ACP {Delta}{sup 9} and a 16:0-ACP {Delta}{sup 4} desaturase. Downstream metabolism of the SAD2 reaction products would give rise to alkenes with double-bonds at position 9 or position 12, matching double-bond positions observed in alkenes in the odor bouquet of O. sphegodes. SAD1 and SAD2 show evidence of purifying selection before, and positive or relaxed purifying selection after gene duplication. By contributing to the production of species-specific alkene bouquets, SAD2 is suggested to contribute to differential pollinator attraction and reproductive isolation among these species. Taken together, these data are consistent with the hypothesis that SAD2 is a florally expressed barrier gene of large phenotypic effect and, possibly, a genic target of pollinator-mediated selection.

  13. Estabilidade relativa de alcenos: análise dos critérios encontrados nos livros textos de graduação e uma proposta de explicação operacional para alcenos dissubstituídos

    Directory of Open Access Journals (Sweden)

    Cunha Silvio

    2003-01-01

    Full Text Available Despite of being used as thermodynamic criterion to rank alkene stability in a number of undergraduate textbooks, the heat of hydrogenation does not describe adequately the relative stability of disubstituted alkenes. In this work, both the heat of formation and the heat of combustion were used as thermodynamic criteria to rank correctly the stability of alkenes according to the degree of alkyl substitution and also in the disubstituted series (geminal > trans > cis. An operational model based on molecular orbital and valence bond representations of hyperconjugation is proposed to show how this effect can explain the order of stability of this class of compounds.

  14. Solvent-free one-pot 1,3-dipolar cycloaddition reactions of dihydropyran derived nitrone

    Indian Academy of Sciences (India)

    Bhaskar Chakraborty; Prawin Kumar Sharma; Neelam Rai; Chiran Devi Sharma

    2012-05-01

    Microwave-induced 1,3-dipolar cycloaddition reactions of dihydropyran derived nitrone with various activated alkenes have been studied in situ and found to afford new isoxazolidine derivatives with moderate selectivity.

  15. Carbenes and Nitrenes

    Science.gov (United States)

    Coyle, J. D.

    1974-01-01

    Summarizes the general methods for carbene and nitrene formation and the reactions in which carbenes and nitrenes are involved such as their reactions with transition metal atoms, alkenes of aromatic compounds, and uncharged oxygen or nitrogen nucleophiles. (CC)

  16. Structural and Pharmacological Effects of Ring-Closing Metathesis in Peptides

    Directory of Open Access Journals (Sweden)

    Pål Rongved

    2010-09-01

    Full Text Available Applications of ring-closing alkene metathesis (RCM in acyclic α- and β-peptides and closely related systems are reviewed, with a special emphasis on the structural and pharmacological effects of cyclization by RCM.

  17. Structural and Pharmacological Effects of Ring-Closing Metathesis in Peptides

    OpenAIRE

    Pål Rongved; Øyvind Jacobsen; Jo Klaveness

    2010-01-01

    Applications of ring-closing alkene metathesis (RCM) in acyclic α- and β-peptides and closely related systems are reviewed, with a special emphasis on the structural and pharmacological effects of cyclization by RCM.

  18. (Z-4-(2,5-Di-tert-butylanilinopent-3-en-2-one

    Directory of Open Access Journals (Sweden)

    Jesús Pastrán

    2011-06-01

    Full Text Available In the crystal structure of the title ketoamine, C19H29NO, the bond lengths from the N atom through the alkene group to the ketone O atom show the presence of an extensively delocalized π-system. The dihedral angle between the plane of the phenyl ring and that of the alkene component is 63.45 (7° due to steric hindrance exerted by the tert-butyl groups. The molecule has a Z-configured alkene function, which is facilitated by an intramolecular N—H...O hydrogen bond between the amine and ketone groups. The molecules are linked into extended chains, which run parallel to the [010] direction, by a very weak C—H...O interaction between the methyl substituent of the alkene group and the ketone O atom of a neighbouring molecule.

  19. Magnetic Carbon Supported Palladium Nanoparticles: An Efficient and Sustainable Catalyst for Hydrogenation Reactions

    Science.gov (United States)

    Magnetic carbon supported Pd catalyst has been synthesized via in situ generation of nanoferrites and incorporation of carbon from renewable cellulose via calcination; the catalyst can be used for the hydrogenation of alkenes and reduction of aryl nitro compounds.

  20. Boosting the Boron Dopant Level in Monolayer Doping by Carboranes.

    Science.gov (United States)

    Ye, Liang; González-Campo, Arántzazu; Núñez, Rosario; de Jong, Michel P; Kudernac, Tibor; van der Wiel, Wilfred G; Huskens, Jurriaan

    2015-12-16

    Monolayer doping (MLD) presents an alternative method to achieve silicon doping without causing crystal damage, and it has the capability of ultrashallow doping and the doping of nonplanar surfaces. MLD utilizes dopant-containing alkene molecules that form a monolayer on the silicon surface using the well-established hydrosilylation process. Here, we demonstrate that MLD can be extended to high doping levels by designing alkenes with a high content of dopant atoms. Concretely, carborane derivatives, which have 10 B atoms per molecule, were functionalized with an alkene group. MLD using a monolayer of such a derivative yielded up to ten times higher doping levels, as measured by X-ray photoelectron spectroscopy and dynamic secondary mass spectroscopy, compared to an alkene with a single B atom. Sheet resistance measurements showed comparably increased conductivities of the Si substrates. Thermal budget analyses indicate that the doping level can be further optimized by changing the annealing conditions. PMID:26595856

  1. Beyond catalyst deactivation: cross-metathesis involving olefins containing N-heteroaromatics

    OpenAIRE

    Kevin Lafaye; Cyril Bosset; Lionel Nicolas; Amandine Guérinot; Janine Cossy

    2015-01-01

    Alkenes containing N-heteroaromatics are known to be poor partners in cross-metathesis reactions, probably due to catalyst deactivation caused by the presence of a nitrogen atom. However, some examples of ring-closing and cross-metathesis involving alkenes that incorporate N-heteroaromatics can be found in the literature. In addition, recent mechanistic studies have focused on the rationalization of nitrogen-induced catalysts deactivation. The purpose of this mini-review is to give a brief ov...

  2. Novel Haloperoxidase Reaction: Synthesis of Dihalogenated Products

    OpenAIRE

    Geigert, John; Neidleman, Saul L.; Dalietos, Demetrios J.; DeWitt, Susanne K.

    1983-01-01

    The enzymatic synthesis of vicinal, dihalogenated products from alkenes and alkynes is described. The enzymatic reaction required an alkene or alkyne, dilute hydrogen peroxide, a haloperoxidase, and molar amounts of halide ions. Vicinal dichloro, dibromo, and diiodo products could be formed. A hydroxyl group on the carbon adjacent to the carbon-carbon double or triple bond lowered the halide ion concentration needed to produce the dihalo product. This reaction offers one explanation for the o...

  3. Observation of the simplest Criegee intermediate CH2OO in the gas-phase ozonolysis of ethylene

    OpenAIRE

    Womack, Caroline C.; Martin-Drumel, Marie-Aline; Brown, Gordon G.; Field, Robert W.; McCarthy, Michael C.

    2015-01-01

    Ozonolysis is one of the dominant oxidation pathways for tropospheric alkenes. Although numerous studies have confirmed a 1,3-cycloaddition mechanism that generates a Criegee intermediate (CI) with form R[subscript 1]R[subscript 2]COO, no small CIs have ever been directly observed in the ozonolysis of alkenes because of their high reactivity. We present the first experimental detection of CH[subscript 2]OO in the gas-phase ozonolysis of ethylene, using Fourier transform microwave spectroscopy...

  4. Chromium oxide catalysts in the dehydrogenation of alkanes

    OpenAIRE

    Airaksinen, Sanna

    2005-01-01

    Light alkenes, such as propene and butenes, are important intermediates in the manufacture of fuel components and chemicals. The direct catalytic dehydrogenation of the corresponding alkanes is a selective way to produce these alkenes and is frequently carried out using chromia/alumina catalysts. The aim of this work was to obtain structure–activity information, which could be utilised in the optimisation of this catalytic system. The properties of chromia/alumina catalysts were investigated ...

  5. Synthesis and characterization of microporous and mesoporous catalysts for shale gas upgrading

    OpenAIRE

    Contractor, Danesh; Joshi, Ravi; Gounder, Rajamani

    2014-01-01

    The petroleum industry is gradually shifting from using naphtha to ethane as its feedstock and new ethane steam crackers are being built. Using ethane as a feedstock produces more ethene and less co-products such as propene, aromatics and C4 alkenes. Thus, the shift in feedstock will reduce the availability of these co-products. Developing methods for the interconversion of alkenes, and specifically using ethene as a reactant, can solve this problem. This project focuses on synthesis and c...

  6. Fast and Efficient [2+2] UV Cycloaddition for Polymer Modification via Flow Synthesis

    OpenAIRE

    CONRADI, Matthias Horst; Junkers, Thomas

    2014-01-01

    The alkene enone [2 + 2] photocycloaddition reaction between polymer-bound maleimide and functional alkenes has been tested in a UV-flow reactor, demonstrating a very high efficiency of the reaction. As a test reaction, polymer end group modifications were carried out on maleimide-functional poly(butyl acrylate). The polymer was prepared by atom transfer radical polymerization (ATRP) using a N-hydroxysuccinimide-functionalized initiator, followed by exchange reaction of the activated ester wi...

  7. Catalytic activation of alkanes on noble metal-loaded zeolites : experimental studies and simulation of the dehydroalkylation of toluene with ethane

    OpenAIRE

    Rezai, Alireza

    2012-01-01

    With the recent progress in chemical reaction engineering and highly active, multi-functional catalysts, the activation of relatively inert alkanes may be achieved. The direct use of short-chain alkanes, especially methane and ethane, as basic chemical feedstocks represents an attractive alternative to alkenes. Significant reserves of alkanes are found in nature in the form of wet natural gas, whereas alkenes have to be synthesized via other chemical reactions. The activation of alkanes can b...

  8. Enantioconvergent synthesis by sequential asymmetric Horner-Wadsworth-Emmons and palladium-catalyzed allylic substitution reactions

    DEFF Research Database (Denmark)

    Pedersen, Torben Møller; Hansen, E. Louise; Kane, John;

    2001-01-01

    A new method for enantioconvergent synthesis has been developed. The strategy relies on the combination of an asymmetric Horner-Wadsworth-Emmons (HWE) reaction and a palladium-catalyzed allylic substitution. Different $alpha@-oxygen-substituted, racemic aldehydes were initially transformed by...... asymmetric HWE reactions into mixtures of two major $alpha@,$beta@-unsaturated esters, possessing opposite configurations at their allylic stereocenters as well as opposite alkene geometry. Subsequently, these isomeric mixtures of alkenes could be subjected to palladium-catalyzed allylic substitution...

  9. Rhodium(III)-catalyzed C-C coupling of 7-azaindoles with vinyl acetates and allyl acetates.

    Science.gov (United States)

    Li, Shuai-Shuai; Wang, Cheng-Qi; Lin, Hui; Zhang, Xiao-Mei; Dong, Lin

    2016-01-01

    The behaviour of electron-rich alkenes with 7-azaindoles in rhodium(III)-catalyzed C-H activation is investigated. Various substituted vinyl acetates and allyl acetates as coupling partners reacted smoothly providing a wide variety of 7-azaindole derivatives, and the selectivity of the coupling reaction is alkene-dependent. In addition, the approaches of rhodium(III)-catalyzed dehydrogenative Heck-type reaction (DHR) and carbonylation reaction were quite novel and simple. PMID:26553424

  10. Integrated process for preparing a carboxylic acid from an alkane

    Energy Technology Data Exchange (ETDEWEB)

    Benderly, Abraham (Elkins Park, PA); Chadda, Nitin (Radnor, PA); Sevon, Douglass (Fairless Hills, PA)

    2011-12-20

    The present invention relates to an integrated process for producing unsaturated carboxylic acids from the corresponding C.sub.2-C.sub.4 alkane. The process begins with performance of thermally integrated dehydrogenation reactions which convert a C.sub.2-C.sub.4 alkane to its corresponding C.sub.2-C.sub.4 alkene, and which involve exothermically converting a portion of an alkane to its corresponding alkene by oxidative dehydrogenation in an exothermic reaction zone, in the presence of oxygen and a suitable catalyst, and then feeding the products of the exothermic reaction zone to an endothermic reaction zone wherein at least a portion of the remaining unconverted alkane is endothermically dehydrogenated to form an additional quantity of the same corresponding alkene, in the presence of carbon dioxide and an other suitable catalyst. The alkene products of the thermally integrated dehydrogenation reactions are then provided to a catalytic vapor phase partial oxidation process for conversion of the alkene to the corresponding unsaturated carboxylic acid or nitrile. Unreacted alkene and carbon dioxide are recovered from the oxidation product stream and recycled back to the thermally integrated dehydrogenation reactions.

  11. Adsorption of Small Hydrocarbons on Rutile TiO2(110)

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Long; Smith, R. Scott; Kay, Bruce D.; Dohnalek, Zdenek

    2016-08-01

    Temperature programmed desorption and molecular beam scattering were used to study the adsorption and desorption of small hydrocarbons (n-alkanes, 1-alkenes and 1-alkynes with 1 - 4 carbon atoms of C1-C4) on rutile TiO2(110). We show that the sticking coefficients for all the hydrocarbons are close to unity (> 0.95) at an adsorption temperature of 60 K. The desorption energies for hydrocarbons of the same chain length increase from n-alkanes to 1-alkenes and to 1-alkynes. This trend is likely a consequence of an additional dative bonding of the alkene and alkyne π system to the coordinatively unsaturated Ti5c sites. Similar to previous studies on the adsorption of n-alkanes on metal and metal oxide surfaces, we find the desorption energies within each group (n-alkanes vs. 1-alkenes vs. 1-alkynes) from Ti5c sites increase linearly with the chain length. The absolute saturation coverages of each hydrocarbon on Ti5c sites were also determined. The saturation coverage of CH4, is found to be ~ 2/3 monolayer (ML). The saturation coverages of C2-C4 hydrocarbons are found nearly independent of the chain length with values of ~1/2 ML for n-alkanes and 1-alkenes and 2/3 ML for 1-alkynes. This result is surprising considering their similar sizes.

  12. Methods of making organic compounds by metathesis

    Energy Technology Data Exchange (ETDEWEB)

    Abraham, Timothy W.; Kaido, Hiroki; Lee, Choon Woo; Pederson, Richard L.; Schrodi, Yann; Tupy, Michael John

    2015-09-01

    Described are methods of making organic compounds by metathesis chemistry. The methods of the invention are particularly useful for making industrially-important organic compounds beginning with starting compositions derived from renewable feedstocks, such as natural oils. The methods make use of a cross-metathesis step with an olefin compound to produce functionalized alkene intermediates having a pre-determined double bond position. Once isolated, the functionalized alkene intermediate can be self-metathesized or cross-metathesized (e.g., with a second functionalized alkene) to produce the desired organic compound or a precursor thereto. The method may be used to make bifunctional organic compounds, such as diacids, diesters, dicarboxylate salts, acid/esters, acid/amines, acid/alcohols, acid/aldehydes, acid/ketones, acid/halides, acid/nitriles, ester/amines, ester/alcohols, ester/aldehydes, ester/ketones, ester/halides, ester/nitriles, and the like.

  13. Enantiopure Functional Molecular Motors Obtained by a Switchable Chiral-Resolution Process.

    Science.gov (United States)

    van Leeuwen, Thomas; Gan, Jefri; Kistemaker, Jos C M; Pizzolato, Stefano F; Chang, Mu-Chieh; Feringa, Ben L

    2016-05-17

    Molecular switches, rotors, and motors play an important role in the development of nano-machines and devices, as well as responsive and adaptive functional materials. For unidirectional rotors based on chiral overcrowded alkenes, their stereochemical homogeneity is of crucial importance. Herein, a method to obtain new and functionalizable overcrowded alkenes in enantiopure form is presented. The procedure involves a short synthesis of three steps and a solvent-switchable chiral resolution by using a readily available resolving agent. X-ray crystallography revealed the mode of binding of the motor with the resolving agent, as well as the absolute configuration of the motor. (1) H NMR and UV/Vis spectroscopy techniques were used to determine the dynamic behavior of this molecular motor. This method provides rapid access to ample amounts of enantiopure molecular motors, which will greatly facilitate the further development of responsive molecular systems based on chiral overcrowded alkenes. PMID:27072290

  14. Polythioether Particles Armored with Modifiable Graphene Oxide Nanosheets.

    Science.gov (United States)

    Rodier, Bradley J; Mosher, Eric P; Burton, Spencer T; Matthews, Rachael; Pentzer, Emily

    2016-06-01

    Facile and scalable fabrication methods are attractive to prepare materials for diverse applications. Herein, a method is presented to prepare cross-linked polymeric nanoparticles with graphene oxide (GO) nanosheets covalently attached to the surface. Alkene-modified GO serves as a surfactant in a miniemulsion polymerization, and the alkene functionalities of GO exposed to the oil-phase are incorporated into the polymer particle through thiol-ene reactions, leaving the unreacted alkene functional groups of the other face of GO available for further functionalization. The surface of GO-armored polymer particles is then modified with a small molecule fluorophore or carboxylic acid functional groups that bind to Fe2 O3 and TiO2 nanoparticles. This methodology provides a facile route to preparing complex hybrid composite materials. PMID:27076068

  15. Synthesis of Some New Long-chain Salen Catalysts

    Institute of Scientific and Technical Information of China (English)

    WU JinCai; TANG Ning; SUN Yang; ZHANG Ling; Song Bo; TAN MinYu

    2001-01-01

    @@ In the research of enantioselective epoxidation of unfunctionalized alkenes using Salen compounds, Katasuki1 and Jacobsen2 pointed out that 3 and 3′ groups of Salen were very important to increase the e.e of the catalytic product. Recently, in order to explore useful information concerning molecular design of metal catalysts for enantioselective epoxidation of trans-disubstituted alkenes, which remains an unresolved problem in the field of metal-catalyzed asymmetric epoxidation of unfunctionalized alkenes,some new Salen compounds containing long-chain in 3 and 3′ were designed and synthesized. We think these 3 and 3′ long-chain groups not only do as bulky group, but also act as second introduced chiral source. The following is the route:

  16. Conversion of , '-dichlorodiazene dioxides using levulinic acid under solvent-free conditions to -chloroketones through a three-step domino process

    Indian Academy of Sciences (India)

    B C Vimala; Gopalpur Nagendrappa

    2009-11-01

    -Chloroketones find numerous synthetic uses. We have developed a simple method of preparation of these compounds starting from alkenes adopting the Green Chemistry principle of solventfree reaction. The procedure involves addition of NOCl generated in situ by the reaction of AcOH-HCl (3 : 1) with amyl nitrite to alkenes and treating the -chloronitroso compounds obtained as dimers with levulinic acid in presence of a few drops of 6N HCl, the latter being a three-step domino reaction, in which the first is dissociation of dimer to monomer, the second is tautomerisation of the nitroso function to oxime followed by deoximation in the third step. The yields are excellent. Since the starting compounds are readily available alkenes and the reaction is carried out under mild conditions leading to excellent yields of highly useful -chloroketones, the procedure has the potential of wide application.

  17. Epoxidation catalyst and process

    Science.gov (United States)

    Linic, Suljo; Christopher, Phillip

    2010-10-26

    Disclosed herein is a catalytic method of converting alkenes to epoxides. This method generally includes reacting alkenes with oxygen in the presence of a specific silver catalyst under conditions suitable to produce a yield of the epoxides. The specific silver catalyst is a silver nanocrystal having a plurality of surface planes, a substantial portion of which is defined by Miller indices of (100). The reaction is performed by charging a suitable reactor with this silver catalyst and then feeding the reactants to the reactor under conditions to carry out the reaction. The reaction may be performed in batch, or as a continuous process that employs a recycle of any unreacted alkenes. The specific silver catalyst has unexpectedly high selectivity for epoxide products. Consequently, this general method (and its various embodiments) will result in extraordinarily high epoxide yields heretofore unattainable.

  18. Control of ozonolysis kinetics and aerosol yield by nuances in the molecular structure of volatile organic compounds

    Science.gov (United States)

    Harvey, Rebecca M.; Petrucci, Giuseppe A.

    2015-12-01

    Secondary organic aerosol (SOA) plays integral roles in climate and human health, yet there remains a limited understanding of the mechanisms that lead to its formation and ultimate fate, as evidenced by a disparity between modeled atmospheric SOA loadings and field measurements. This disparity highlights the need for a more accurate representation of the molecular-level interactions between SOA sources and oxidative pathways. Due to the paucity of detailed chemical data for most SOA precursors of atmospheric relevance, models generally predict SOA loadings using structure activity relationships generalized to classes of SOA precursors. However, the kinetics and SOA forming potential of molecules are nuanced by seemingly minor structural differences in parent molecules that may be neglected in models. Laboratory chamber studies were used to measure SOA yields and rate constants for the ozonolysis of several linear, cyclic and oxygenated C5-C7 alkenes whose molecular structure vary in the site of unsaturation and/or the presence/position of functional groups and that represent atmospherically relevant classes of molecules. For the alkenes studied in this work, we found greater SOA yields for cyclic compounds compared to their linear analogs. For 1-alkenes, SOA yield increased with carbon number but was also dependent on the position of the double bond (internal vs terminal). Both the identity and position of oxygenated functional groups influenced SOA yield and kinetics through steric and electronic effects. Additionally, terminal alkenes generally resulted in a greater SOA yield than analogous internal alkenes, indicating that the position of the double bond in alkenes plays an important role in its atmospheric fate. Herein, we demonstrate the nuanced behavior of these ozonolysis reactions and discuss relationships between parent compound molecular structure and SOA yield and kinetics.

  19. Origin and palaeoenvironmental significance of C25 and C27n-alk-1-enes in a 25,000-year lake-sedimentary record from equatorial East Africa

    Science.gov (United States)

    van Bree, L. G. J.; Rijpstra, W. I. C.; Cocquyt, C.; Al-Dhabi, N. A.; Verschuren, D.; Sinninghe Damsté, J. S.; de Leeuw, J. W.

    2014-11-01

    We studied the distribution of long-chain alkenes (n-C23 to n-C31) in well-dated sediments from Lake Challa, a deep crater lake near Mt. Kilimanjaro in equatorial East Africa, to reveal signatures of palaeo-environmental and palaeo-climatic changes affecting the production of these compounds during the last 25 kyr. The apolar fractions of organic sediment extracts dated to the last 16 kyr showed an unusual dominance of δ13C-depleted n-C25:1 and n-C27:1 alk-1-enes. These alkenes were not detected in soil and litter from near the shoreline and from the inner rim of the crater, pointing to an autochthonous, aquatic source. Analysis of suspended particulate matter indicated that the n-alk-1-enes are produced in the well-oxygenated upper 30 m of the water column, indicating a phytoplanktonic origin. Sedimenting particles collected monthly from December 2006 to November 2007 showed increased fluxes of n-alk-1-enes following the locally prominent short rain season in November-December. Green algae and/or cyanobacteria were identified as candidate sources of these alkenes. Production of the n-C25:1 and n-C27:1 alkenes in Lake Challa was much reduced during the Last Glacial Maximum and early late-glacial period, suggesting a temperature or CO2 effect on habitat suitability. We explored the potential of n-alk-1-ene accumulation rates, and of a derived Alkene Index [n-C27:1]/([n-C25:1] + [n-C27:1]), to record longer-term climatic changes. The Alkene Index record of Lake Challa over the past 25 kyr shows clear periodicity with a dominant frequency of ∼2.3 kyr, potentially indicative of monsoon variability directly or indirectly forced by variation in solar radiation.

  20. Volatile Organic Compounds Selection for Incorporation in Photochemical Mechanisms and the Development of Secondary Pollution Reduction Strategies

    International Nuclear Information System (INIS)

    In the present work a method for the evaluation of the importance of the VOCs species is presented, aiming to provide criteria for the incorporation of these species into atmospheric photochemical mechanisms and for the successful application of secondary pollution reduction strategies. According to the method presented here, the species can be divided into more important and less important ones, taking into account their mixing ratios and emission values in combination with their reactivity. For this classification three quantitative and one qualitative criteria were introduced. Overall, it is concluded that alkenes with more than a few carbon atoms in their chain appear to be more important in urban and suburban areas, while in background conditions the alkanes, having the smaller chain (ethane, propane), become more important. In the case of alkenes there is no clear species classification, except for the biogenically emitted compounds, isoprene and limonene. In general, more important alkenes appear to be those with the smaller chain (ethene, propene, butene). Most abundant aromatics are benzene, toluene, and xylene. In background conditions higher aromatics are also important, especially 1,2,3-, 1,3,5-, and 1,2,4-trimethylbenzene. The most important carbonylic compounds are formaldehyde, acetaldehyde, and acetone. Finally, taking into account the results mentioned above, a new photochemical mechanism was developed. The species and species groups used in the proposed mechanism are: ethane, higher alkanes, ethene, propene, 2- butene, 1-alkenes, 2-alkenes, higher alkenes, benzene, toluene, m-, o-, p-xylene, 1,3,5-, 1,2,3-, 1,2,4-trimethylbenzene, higher aromatics, formaldehyde, acetaldehyde, higher aldehydes, isoprene, limonene, and other biogenic VOCs

  1. Amino Acid Change in an Orchid Desaturase Enables Mimicry of the Pollinator's Sex Pheromone.

    Science.gov (United States)

    Sedeek, Khalid E M; Whittle, Edward; Guthörl, Daniela; Grossniklaus, Ueli; Shanklin, John; Schlüter, Philipp M

    2016-06-01

    Mimicry illustrates the power of selection to produce phenotypic convergence in biology [1]. A striking example is the imitation of female insects by plants that are pollinated by sexual deception of males of the same insect species [2-4]. This involves mimicry of visual, tactile, and chemical signals of females [2-7], especially their sex pheromones [8-11]. The Mediterranean orchid Ophrys exaltata employs chemical mimicry of cuticular hydrocarbons, particularly the 7-alkenes, in an insect sex pheromone to attract and elicit mating behavior in its pollinators, males of the cellophane bee Colletes cunicularius [11-13]. A difference in alkene double-bond positions is responsible for reproductive isolation between O. exaltata and closely related species, such as O. sphegodes [13-16]. We show that these 7-alkenes are likely determined by the action of the stearoyl-acyl-carrier-protein desaturase (SAD) homolog SAD5. After gene duplication, changes in subcellular localization relative to the ancestral housekeeping desaturase may have allowed proto-SAD5's reaction products to undergo further biosynthesis to both 7- and 9-alkenes. Such ancestral coproduction of two alkene classes may have led to pollinator-mediated deleterious pleiotropy. Despite possible evolutionary intermediates with reduced activity, amino acid changes at the bottom of the substrate-binding cavity have conferred enzyme specificity for 7-alkene biosynthesis by preventing the binding of longer-chained fatty acid (FA) precursors by the enzyme. This change in desaturase function enabled the orchid to perfect its chemical mimicry of pollinator sex pheromones by escape from deleterious pleiotropy, supporting a role of pleiotropy in determining the possible trajectories of adaptive evolution. PMID:27212404

  2. Beyond catalyst deactivation: cross-metathesis involving olefins containing N-heteroaromatics

    Science.gov (United States)

    Lafaye, Kevin; Bosset, Cyril; Nicolas, Lionel

    2015-01-01

    Summary Alkenes containing N-heteroaromatics are known to be poor partners in cross-metathesis reactions, probably due to catalyst deactivation caused by the presence of a nitrogen atom. However, some examples of ring-closing and cross-metathesis involving alkenes that incorporate N-heteroaromatics can be found in the literature. In addition, recent mechanistic studies have focused on the rationalization of nitrogen-induced catalysts deactivation. The purpose of this mini-review is to give a brief overview of successful metathesis reactions involving olefins containing N-heteroaromatics in order to delineate some guidelines for the use of these challenging substrates in metathesis reactions. PMID:26664645

  3. H2 evolution in hexadecane irradiated at high temperatures

    International Nuclear Information System (INIS)

    H2 yields of n-hexadecane irradiated at 330-400 deg. C were determined and compared with that at room temperature. The temperature dependence of G(H2) was found to be insignificant up to 330 deg. C. High G(H2) values above 330 deg. C indicated the enhanced dehydrogenation of hydrocarbons. Compared to alkane, irradiation of alkene at high temperature produces higher H2 yields as shown from the correlation between G(H2) and the fraction of alkene. (author)

  4. Ionic association of Na+-Cl-, Na+-Na+ and Cl--Cl- in methanol: mean force potentials and friction kernels

    OpenAIRE

    Sesé Castel, Gemma; Guàrdia Manuel, Elvira; Padro Cardenas, Joan Angel

    1995-01-01

    Kinetic investigation of 1-octene bromination in AOT-isooctane-water microemulsions (13 = w = [H2O]/[AOT] = 24 and 6 = z = [IO]/[AOT] = 57) shows that the reaction is first-order in alkene and first-order in bromine, as usually found in protic media. Although both reagents are mainly located in the isooctane phase (Ktr, transfer coefficients from isooctane to water, are 1.5 × 10-5 and 8.8 × 10-3 for alkene and bromine, respectively), bromination occurs in an aqueous microenvironment, as illus...

  5. Iron-Catalyzed, Highly Regioselective Synthesis of alpha-Aryl Carboxylic Acids from Styrene Derivatives and CO2

    OpenAIRE

    Greenhalgh, Mark D.; Thomas, Stephen P.

    2012-01-01

    The iron-catalyzed hydrocarboxylation of aryl alkenes has been developed using a highly active bench-stable iron(II) precatalyst to give alpha-aryl carboxylic acids in excellent yields and with near-perfect regioselectivity. Using just 1 mol % FeCl2, bis(imino)pyridine 6 (1 mol %), CO2 (atmospheric pressure), and a hydride source (EtMgBr, 1.2 equiv), a range of sterically and electronically differentiated aryl alkenes were transformed to the corresponding alpha-aryl carboxylic acids (up to 96...

  6. Origin and palaeoenvironmental significance of C25 and C27n-alk-1-enes in a 25,000-year lake-sedimentary record from equatorial East Africa

    OpenAIRE

    van Bree, L.G.J.; Rijpstra, W.I.C.; C. Cocquyt; Al-Dhabi, N.-A.; Verschuren, D.; Sinninghe Damsté, J. S.; Leeuw, J. W. de

    2014-01-01

    We studied the distribution of long-chain alkenes (n-C23 to n-C31) in well-dated sediments from Lake Challa, a deep crater lake near Mt. Kilimanjaro in equatorial East Africa, to reveal signatures of palaeo-environmental and palaeo-climatic changes affecting the production of these compounds during the last 25 kyr. The apolar fractions of organic sediment extracts dated to the last 16 kyr showed an unusual dominance of d13C-depleted n-C25:1 and n-C27:1 alk-1-enes. These alkenes were not detec...

  7. One-pot odourless synthesis of thioesters via in situ generation of thiobenzoic acids using benzoic anhydrides and thiourea.

    Science.gov (United States)

    Abbasi, Mohammad; Khalifeh, Reza

    2015-01-01

    An efficient and odourless procedure for a one-pot synthesis of thioesters by the reaction of benzoic anhydrides, thiourea and various organic halides (primary, allylic, and benzylic) or structurally diverse, electron-deficient alkenes (ketones, esters, and nitriles) in the presence of Et3N has been developed. In this method, thiobenzoic acids were in situ generated from the reaction of thiourea with benzoic anhydrides, which were subjected to conjugate addition with electron-deficient alkenes or a nucleophilic displacement reaction with alkyl halides. PMID:26425185

  8. [2+2+1] cyclization of allenes.

    Science.gov (United States)

    Kitagaki, S; Inagaki, F; Mukai, C

    2014-05-01

    The [2+2+1] cyclization of an alkyne, an alkene and carbon monoxide, i.e., the Pauson-Khand reaction, is one of the most powerful tools for constructing a five-membered ring. In place of the alkene or alkyne part, the use of an allene functionality has proven to make this reaction more valuable for organic synthesis. This review focuses on the origin and progress of the allenic [2+2+1] cyclocarbonylation, including the chirality transfer of the allene and its synthetic applications. PMID:24514744

  9. Beyond catalyst deactivation: cross-metathesis involving olefins containing N-heteroaromatics

    Directory of Open Access Journals (Sweden)

    Kevin Lafaye

    2015-11-01

    Full Text Available Alkenes containing N-heteroaromatics are known to be poor partners in cross-metathesis reactions, probably due to catalyst deactivation caused by the presence of a nitrogen atom. However, some examples of ring-closing and cross-metathesis involving alkenes that incorporate N-heteroaromatics can be found in the literature. In addition, recent mechanistic studies have focused on the rationalization of nitrogen-induced catalysts deactivation. The purpose of this mini-review is to give a brief overview of successful metathesis reactions involving olefins containing N-heteroaromatics in order to delineate some guidelines for the use of these challenging substrates in metathesis reactions.

  10. ESR studies on the radiolysis of crystalline materials at cryogenic temperatures

    International Nuclear Information System (INIS)

    Presently we report our recent works on the radiolysis of crystalline materials that were studied mainly by ESR spectroscopy. They include A)hydrocarbon radiolysis using hydrocarbon mixed crystals with hydrocarbon having a different molecular chain length, alkenes, and with alkynes, B)the structure and reactions of extremely unstable ions of alkenes, alkynes, and halogenated alkanes trapped in crystalline matrices at cryogenic temperatures, and C)transfer and reactions of electrons, holes, and H atoms, and H/D isotope effects in the radiolytic reactions of hydrocarbons and H2O/D2O mixed crystals. (author)

  11. Construction of quaternary stereogenic carbon centers through copper-catalyzed enantioselective allylic cross-coupling with alkylboranes.

    Science.gov (United States)

    Hojoh, Kentaro; Shido, Yoshinori; Ohmiya, Hirohisa; Sawamura, Masaya

    2014-05-01

    A combination of an in situ generated chiral Cu(I) /DTBM-MeO-BIPHEP catalyst system and EtOK enabled the enantioselective SN 2'-type allylic cross-coupling between alkylborane reagents and γ,γ-disubstituted primary allyl chlorides with enantiocontrol at a useful level. The reaction generates a stereogenic quaternary carbon center having three sp(3) -alkyl groups and a vinyl group. This protocol allowed the use of terminal alkenes as nucleophile precursors, thus representing a formal reductive allylic cross-coupling of terminal alkenes. A reaction pathway involving addition/elimination of a neutral alkylcopper(I) species with the allyl chloride substrate is proposed. PMID:24668885

  12. Catalyst-controlled regioselectivity in the synthesis of branched conjugated dienes via aerobic oxidative Heck reactions.

    Science.gov (United States)

    Zheng, Changwu; Wang, Dian; Stahl, Shannon S

    2012-10-10

    Pd-catalyzed aerobic oxidative coupling of vinylboronic acids and electronically unbiased alkyl olefins provides regioselective access to 1,3-disubstituted conjugated dienes. Catalyst-controlled regioselectivity is achieved by using 2,9-dimethylphenanthroline as a ligand. The observed regioselectivity is opposite to that observed from a traditional (nonoxidative) Heck reaction between a vinyl bromide and an alkene. DFT computational studies reveal that steric effects of the 2,9-dimethylphenanthroline ligand promote C-C bond formation at the internal position of the alkene. PMID:22998540

  13. The Synthesis and Crystal Structure of a Remarkable Binuclear, Double Pd–Cl–H–O–Pd Bridged Palladium Alcohol Complex. Catalytic Oxidations with Molecular Oxygen mediated by [{[Me2C(OH)CH2CONMe2]Pd(Cl)NO2}2

    OpenAIRE

    Kiers, Niklaas H.; Kooijman, Huub; Anthony L. Spek; van Leeuwen, Piet W. N. M.; Feringa, Bernard

    1992-01-01

    The Pd(Cl)NO2 complex of N,N-3-trimethyl-3-hydroxybutyramide is dimeric in the solid state with two Pd–Cl–H–O–Pd hydrogen-bond bridges; however, in solution the complex is monomeric and catalytically active in the oxidation of alkenes.

  14. Enyne Metathesis Catalyzed by Ruthenium Carbene Complexes

    DEFF Research Database (Denmark)

    Poulsen, Carina Storm; Madsen, Robert

    2003-01-01

    Enyne metathesis combines an alkene and an alkyne into a 1,3-diene. The first enyne metathesis reaction catalyzed by a ruthenium carbene complex was reported in 1994. This review covers the advances in this transformation during the last eight years with particular emphasis on methodology...

  15. Water-soluble diphosphadiazacyclooctanes as ligands for aqueous organometallic catalysis

    KAUST Repository

    Boulanger, Jérôme

    2012-12-01

    Two new water-soluble diphosphacyclooctanes been synthesized and characterized by NMR and surface tension measurements. Both phosphanes proved to coordinate rhodium in a very selective way as well-defined bidentates were obtained. When used in Rh-catalyzed hydroformylation of terminal alkenes, both ligands positively impacted the reaction chemoselectivity. © 2012 Elsevier B.V.

  16. Effect of Coexistent Hydrogen on the Selective Production of Ethane by Dehydrogenative Methane Coupling through Dielectric-Barrier Discharge under Ordinary Pressure at an Ambient Temperature

    OpenAIRE

    Katsuya Konno; Kaoru Onoe; Yasuyuki Takiguchi; Tatsuaki Yamaguchi

    2014-01-01

    The effect of coexistence of hydrogen on the product selectivity to ethane from methane by dielectric-barrier discharge (DBD) reactor was examined experimentally under ordinary pressure without use of catalyst and external heating. By the dilution of methane with hydrogen, both the increase of methane conversion and the decrease of alkene production were observed, improving the selectivities to ethane by ca. 70%.

  17. N-halossacarinas: reagentes úteis (e alternativos em síntese orgânica

    Directory of Open Access Journals (Sweden)

    Souza Soraia P. L. de

    2006-01-01

    Full Text Available N-halosaccharins proved to be useful and alternative reagents for diverse organic transformations, such as halogenation of aromatic compounds, benzylic and alpha-carbonylic positions, cohalogenation of alkenes, oxidation of secondary alcohols, etc. Their preparation from saccharin, a cheap and readly available starting material, is simple.

  18. N-halossacarinas: reagentes úteis (e alternativos em síntese orgânica

    Directory of Open Access Journals (Sweden)

    Soraia P. L. de Souza

    2006-10-01

    Full Text Available N-halosaccharins proved to be useful and alternative reagents for diverse organic transformations, such as halogenation of aromatic compounds, benzylic and alpha-carbonylic positions, cohalogenation of alkenes, oxidation of secondary alcohols, etc. Their preparation from saccharin, a cheap and readly available starting material, is simple.

  19. 4-Oxalocrotonate tautomerase, its homologue YwhB, and active vinylpyruvate hydratase : Synthesis and evaluation of 2-fluoro substrate analogues

    NARCIS (Netherlands)

    Johnson, William H; Wang, Susan C; Stanley, Thanuja M; Czerwinski, Robert M; Almrud, Jeffrey J; Poelarends, Gerrit J; Murzin, Alexey G; Whitman, Christian P

    2004-01-01

    A series of 2-fluoro-4-alkene and 2-fluoro-4-alkyne substrate analogues were synthesized and examined as potential inhibitors of three enzymes: 4-oxalocrotonate tautomerase (4-OT) and vinylpyruvate hydratase (VPH) from the catechol meta-fission pathway and a closely related 4-OT homologue found in B

  20. Modern Reduction Methods

    CERN Document Server

    Andersson, Pher G

    2008-01-01

    With its comprehensive overview of modern reduction methods, this book features high quality contributions allowing readers to find reliable solutions quickly and easily. The monograph treats the reduction of carbonyles, alkenes, imines and alkynes, as well as reductive aminations and cross and heck couplings, before finishing off with sections on kinetic resolutions and hydrogenolysis. An indispensable lab companion for every chemist.

  1. Amide and amine nucleophiles in polar radical crossover cycloadditions: synthesis of γ-lactams and pyrrolidines.

    Science.gov (United States)

    Gesmundo, Nathan J; Grandjean, Jean-Marc M; Nicewicz, David A

    2015-03-01

    In this work we present a direct catalytic synthesis of γ-lactams and pyrrolidines from alkenes and activated unsaturated amides or protected unsaturated amines, respectively. Using a mesityl acridinium single electron photooxidant and a thiophenol cocatalyst under irradiation, we are able to directly forge these important classes of heterocycles with complete regiocontrol. PMID:25695366

  2. Synthesis of Macrocyclic Tetrazoles for Rapid Photoinduced Bioorthogonal 1,3-Dipolar Cycloaddition Reactions

    OpenAIRE

    Yu, Zhipeng; Lim, Reyna K. V.; Lin, Qing

    2010-01-01

    A series of conformationally constrained, macrocyclic tetrazoles were expediently prepared by double alkylation of a bis(o-phenolyl)tetrazole precursor. Several of them showed excellent reactivity toward norbornene in a photoinduced tetrazole-alkene cycloaddition reaction in organic solvent as well as toward a norbornene-modified protein in PBS buffer.

  3. Engineering metabolic systems for production of advanced fuels

    OpenAIRE

    Yan, Yajun; Liao, James C.

    2009-01-01

    The depleting petroleum storage and increasing environmental deterioration are threatening the sustainable development of human societies. As such, biofuels and chemical feedstocks generated from renewable sources are becoming increasingly important. Although previous efforts led to great success in bio-ethanol production, higher alcohols, fatty acid derivatives including biodiesels, alkanes, and alkenes offer additional advantages because of their compatibility with existing infrastructure. ...

  4. Nanoscale Polymeric Amphiphiles by Combination of Controlled Polymerizations and "Click" Reactions: Implications for Drug Delivery

    DEFF Research Database (Denmark)

    Javakhishvili, Irakli

    Denne ph.d.-afhandling er baseret på tre forskellige temaer, der er sammenflettet af den uvurdelige alsidighed og de værdifulde egenskaber af -heterobifunktionel poly(-caprolacton). Et bibliotek af -heterobifunktionelle poly(-caprolacton)er med alkyn, alken, bromoalkyl og -bromoiosbutyryl...

  5. PRECISE SYNTHESIS OF OLEFIN BLOCK COPOLYMERS USING A SYNDIOSPECIFIC LIVING POLYMERIZATION SYSTEM

    Institute of Scientific and Technical Information of China (English)

    Zheng-guo Cai; Hai-hui Su; Takeshi Shiono

    2013-01-01

    This feature article summarizes the synthesis of novel olefin block copolymers using fast syndiospecific living homo-and copolymerization of propylene,higher 1-alkene,and norbomene with ansa-fluorenylamidodimethyltitaniumbased catalyst according to the authors' recent results.The catalytic synthesis of monodisperse polyolefin and olefin block copolymer was also described using this living system.

  6. An optimal hydrogen-bond surrogate for α-helices.

    Science.gov (United States)

    Joy, Stephen T; Arora, Paramjit S

    2016-04-14

    Substitution of a main chain i → i + 4 hydrogen bond with a covalent bond can nucleate and stabilize the α-helical conformation in peptides. Herein we describe the potential of different alkene isosteres to mimic intramolecular hydrogen bonds and stabilize α-helices in diverse peptide sequences. PMID:27046675

  7. Catálise assimétrica na ciclopropanação de olefinas Asymmetric catalysis in the cyclopropanation of olefins

    Directory of Open Access Journals (Sweden)

    Raquel A. C. Leão

    2007-01-01

    Full Text Available The main methodologies in the asymmetric cyclopropanation of alkenes with emphasis on asymmetric catalysis are covered. Exemples are the Simmons-Smith reaction, the use of diazoalkanes and reactions carried out by decomposition of alpha-diazoesters in the presence of transition metals.

  8. Rhodium(III)-Catalyzed C-H Activation/Annulation with Vinyl Esters as an Acetylene Equivalent

    OpenAIRE

    Webb, NJ; Marsden, SP; Raw, SA

    2014-01-01

    The behavior of electron-rich alkenes in rhodium-catalyzed C–H activation/annulation reactions is investigated. Vinyl acetate emerges as a convenient acetylene equivalent, facilitating the synthesis of sixteen 3,4-unsubstituted isoquinolones, as well as select heteroaryl-fused pyridones. The complementary regiochemical preferences of enol ethers versus enol esters/enamides is discussed

  9. Renewable linear alpha olefins by selective ethenolysis of decarboxylated fatty acids

    NARCIS (Netherlands)

    Klis, van der F.; Notre, le J.E.L.; Blaauw, R.; Haveren, van J.; Es, van D.S.

    2012-01-01

    A two-step concept for the production of linear alpha olefins from biomass is reported. As a starting material an internally unsaturated C17 alkene was used, which was obtained by the decarboxylation of oleic acid. Here, we report on the ethenolysis of this bio-based product, using commercially avai

  10. Combined experimental and theoretical study of the mechanism and enantioselectivity of palladium-catalyzed intermolecular Heck coupling

    DEFF Research Database (Denmark)

    Henriksen, Signe Teuber; Norrby, Per-Ola; Kaukoranta, Päivi;

    2008-01-01

    -Pd(P,N) species prefers a geometry with the phenyl trans to N. However, the alternative form, with Ph trans to P, is much less stable but much more reactive. In the preferred transition state, the phenyl moiety is trans to P, but significant electron density has been transferred to the alkene carbon trans to N...... date....

  11. Tetramethyl(perfluoroalkyl)cyclopentadienyl Rhodium(I) Complexes with Ethylene or Diene Ligands. Crystal Structure of [(eta-5-C5Me4C6F13)Rh(CO)2

    Czech Academy of Sciences Publication Activity Database

    Čermák, Jan; Krupková, Alena; Auerová, Kateřina; Zamrzla, M.; Nguyen Thi, T.H.; Vojtíšek, P.; Císařová, I.

    2010-01-01

    Roč. 695, č. 3 (2010), s. 375-381. ISSN 0022-328X R&D Projects: GA AV ČR IAA4072203; GA MŠk(CZ) LC06070 Institutional research plan: CEZ:AV0Z40720504 Keywords : fluorous cyclopentadienes * rhodium complexes * alkene complexes Subject RIV: CC - Organic Chemistry Impact factor: 2.205, year: 2010

  12. DETERMINATION OF CHEMICAL CLASSES FROM MASS SPECTRA OF TOXIC ORGANIC COMPOUNDS BY SIMCA PATTERN RECOGNITION AND INFORMATION THEORY

    Science.gov (United States)

    The low resolution mass spectra of a set of 78 toxic volatile organic compounds were examined for information concerning chemical classes. These compounds were predominately chloro- and/or bromoaromatics, -alkanes, or -alkenes, which are routinely sought at trace levels in ambien...

  13. Ni(0-CMC-Na Nickel Colloids in Sodium Carboxymethyl-Cellulose: Catalytic Evaluation in Hydrogenation Reactions

    Directory of Open Access Journals (Sweden)

    Abdallah Karim

    2011-01-01

    Full Text Available A recyclable catalyst, Ni(0-CMC-Na, composed of nickel colloids dispersed in a water soluble bioorganic polymer, sodium carboxymethylcellulose (CMC-Na, was synthesized by a simple procedure from readily available reagents. The catalyst thus obtained is stable and highly active in alkene hydrogenations.

  14. Ni(0)-CMC-Na Nickel Colloids in Sodium Carboxymethyl-Cellulose: Catalytic Evaluation in Hydrogenation Reactions

    OpenAIRE

    Abdallah Karim; Larbi El Firdoussi; Issam Houssini; Mustapha Ait Ali; M. Carmen Puerta; Mohamed Anouar Harrad; Pedro Valerga

    2011-01-01

    A recyclable catalyst, Ni(0)-CMC-Na, composed of nickel colloids dispersed in a water soluble bioorganic polymer, sodium carboxymethylcellulose (CMC-Na), was synthesized by a simple procedure from readily available reagents. The catalyst thus obtained is stable and highly active in alkene hydrogenations.

  15. Pd-Catalyzed Z-Selective Semihydrogenation of Alkynes : Determining the Type of Active Species

    NARCIS (Netherlands)

    Drost, Ruben M.; Rosar, Vera; Marta, Silvia Dalla; Lutz, Martin; Demitri, Nicola; Milani, Barbara; De Bruin, Bas; Elsevier, Cornelis J.

    2015-01-01

    A protocol was developed to distinguish between well-defined molecular and nanoparticle-based catalysts for the Pd-catalyzed semihydrogenation reaction of alkynes to Z-alkenes. The protocol applies quantitative partial poisoning and dynamic light scattering methods, which allow the institution of ad

  16. Experimental and theoretical study of Hoveyda-Grubbs catalysts modified by perfluorohexyl ponytail in the alkoxybenzylidene ligand

    Czech Academy of Sciences Publication Activity Database

    Kvíčala, J.; Schindler, M.; Kelbichová, V.; Babuněk, M.; Rybáčková, M.; Kvíčalová, M.; Cvačka, Josef; Březinová, Anna

    2013-01-01

    Roč. 153, September (2013), s. 12-25. ISSN 0022-1139 Grant ostatní: GA ČR(CZ) GAP207/10/1533 Institutional support: RVO:61388963 Keywords : Hoveyda-Grubbs catalyst * NHC ligand * ruthenium complex * fluorous * alkene metathesis * DFT Subject RIV: CC - Organic Chemistry Impact factor: 1.952, year: 2013

  17. Bite angle effects of diphosphines in carbonylation reactions

    NARCIS (Netherlands)

    P.W.N.M. van Leeuwen; Z. Freixa

    2008-01-01

    This chapter contains sections titled: * Introduction * Rhodium-Catalyzed Hydroformylation o Introduction o Steric Bite Angle Effect and Regioselectivity o Electronic Bite Angle Effect and Activity o Isotope Effects [24] * Platinum-Catalyzed Alkene Hydroformylation * Palladium-Catalyzed CO/Ethene Co

  18. Preparative semiconductor photoredox catalysis: An emerging theme in organic synthesis

    Directory of Open Access Journals (Sweden)

    David W. Manley

    2015-09-01

    Full Text Available Heterogeneous semiconductor photoredox catalysis (SCPC, particularly with TiO2, is evolving to provide radically new synthetic applications. In this review we describe how photoactivated SCPCs can either (i interact with a precursor that donates an electron to the semiconductor thus generating a radical cation; or (ii interact with an acceptor precursor that picks up an electron with production of a radical anion. The radical cations of appropriate donors convert to neutral radicals usually by loss of a proton. The most efficient donors for synthetic purposes contain adjacent functional groups such that the neutral radicals are resonance stabilized. Thus, ET from allylic alkenes and enol ethers generated allyl type radicals that reacted with 1,2-diazine or imine co-reactants to yield functionalized hydrazones or benzylanilines. SCPC with tertiary amines enabled electron-deficient alkenes to be alkylated and furoquinolinones to be accessed. Primary amines on their own led to self-reactions involving C–N coupling and, with terminal diamines, cyclic amines were produced. Carboxylic acids were particularly fruitful affording C-centered radicals that alkylated alkenes and took part in tandem addition cyclizations producing chromenopyrroles; decarboxylative homo-dimerizations were also observed. Acceptors initially yielding radical anions included nitroaromatics and aromatic iodides. The latter led to hydrodehalogenations and cyclizations with suitable precursors. Reductive SCPC also enabled electron-deficient alkenes and aromatic aldehydes to be hydrogenated without the need for hydrogen gas.

  19. 含o-Me2N-C6H4-C(CH3)(CH3)-基团的茂铬催化剂的合成及催化乙烯聚合研究%Synthesis and Characterization of Cyclopentadienylchromium Complexes Bearing a Pendant o-Me2N-C6H4-C(CH3)(CH3)-Group as Catalysts for Ethylene Polymerization

    Institute of Scientific and Technical Information of China (English)

    钱延龙; 张浩; 黄吉玲

    2003-01-01

    High-density polyethylene (PE) was developed in the 1950s by Hogan et al[1] using a Cr2O3/SiO2 catalyst and by the Union Carbide Corporation[2,3] using a Cp2Cr catalyst. Chromium catalysts have played a key role in the early development of heterogeneous catalysts for the alkene polymerization.

  20. In Situ Spectroscopic Investigation of the Rhenium-Catalyzed Deoxydehydration of Vicinal Diols

    DEFF Research Database (Denmark)

    Dethlefsen, Johannes Rytter; Fristrup, Peter

    2015-01-01

    rhenium(V) complex (the rate-limiting step), 2) condensation of the diol and the rhenium(V) complex to a rhenium(V) diolate, and 3) extrusion of the alkene accompanied by oxidation of the Re center and thus regeneration of CH3ReO3. The reaction follows zero-order kinetics initially but, unexpectedly...

  1. "Decarbonization" of an imino N-heterocyclic carbene via triple benzyl migration from hafnium

    Science.gov (United States)

    An imino N-heterocyclic carbene underwent three sequential benzyl migrations upon reaction with tetrabenzylhafnium, resulting in complete removal of the carbene carbon from the ligand. The resulting eneamido-amidinato hafnium complex showed alkene polymerization activity comparable to that of a prec...

  2. DFT Investigation of the Palladium-Catalyzed Ene-Yne Coupling

    DEFF Research Database (Denmark)

    Henriksen, Signe Teuber; Tanner, David Ackland; Skrydstrup, T.;

    2010-01-01

    The mechanism of the recently developed palladium-catalyzed ene-yne coupling has been evaluated by DFT methods. The calculations validate the previously proposed reaction mechanism and explain the stereoselectivity of the reaction (exclusive formation of the E isomer of the disubstituted alkene)....

  3. Tandem Ru-alkylidene-catalysed cross metathesis/hydrogenation: synthesis of lipophilic amino acids.

    Science.gov (United States)

    Wang, Zhen J; Spiccia, Nicolas D; Jackson, W Roy; Robinson, Andrea J

    2013-08-01

    Highly efficient synthesis of lipidic amino acids can be achieved via Ru-alkylidene-catalysed cross metathesis of long chain alkenes with commercially available allylglycine. The resultant unsaturated analogues can be then optionally hydrogenated under mild reaction conditions by using the spent metathesis catalyst. PMID:23733491

  4. CUTICULAR HYDROCARBONS OF THE FLEA BEETLES, APHTHONA LACERTOSA AND APHTHONA NIGRISCUTIS, BIOCONTROL AGENTS FOR LEAFY SPURGE, EUPHORBIA ESULA

    Science.gov (United States)

    The adult beetles, Aphthona lacertosa and Aphthona nigriscutis, used as biocontrol agents for leafy spurge, had a complex mixture of hydrocarbons on their cuticular surface consisting of alkanes, methylalkanes, alkenes and alkadienes as determined by gas chromatography-mass spectrometry. In both ...

  5. Hydrocarbons. Independent Learning Project for Advanced Chemistry (ILPAC). Unit O1.

    Science.gov (United States)

    Inner London Education Authority (England).

    This unit on hydrocarbons is one of 10 first year units produced by the Independent Learning Project for Advanced Chemistry (ILPAC). The unit is divided into sections dealing with alkanes, alkenes, alkynes, arenes, and several aspects of the petroleum industry. Two experiments, exercises (with answers), and pre- and post-tests are included.…

  6. Biocatalysts for selective introduction of oxygen

    DEFF Research Database (Denmark)

    Leak, D. J.; Sheldon, R. A.; Woodley, John; Adlercreutz, P.

    2009-01-01

    Three types of oxygenase biocatalysts are treated in detail in this review: the non-haem iron alkene mono-oxygenases, the haem and vanadium haloperoxidases, and flavin-based Baeyer-Villiger mono-oxygenases. Other oxygenases are briefly included for comparison. Characteristics of the biocatalysts...

  7. High Yield of Liquid Range Olefins Obtained by Converting i-Propanol over Zeolite H-ZSM-5

    DEFF Research Database (Denmark)

    Mentzel, Uffe Vie; Shunmugavel, Saravanamurugan; Hruby, S.L.;

    2009-01-01

    , the selectivity toward alkanes and aromatics declines rapidly over time on stream, and at 20 bar of pressure the liquid product mixture consists almost exclusively Of C-4-C-12 alkenes after approximately a third of the full reaction time. This discovery could open a new route to hydrocarbons via i-propanol from...

  8. Product distributions of Fischer-Tropsch synthesis over Co/AC catalyst

    Institute of Scientific and Technical Information of China (English)

    Weixin Qian; Haitao Zhang; Weiyong Ying; Dingye Fang

    2011-01-01

    The product distributions of Fischer-Tropsch synthesis over Co/AC catalyst are investigated under different reaction conditions in an integral fixed bed reactor.It is found that the product distributions deviate from the ASF distribution.The deviation from ASF distribution is analyzed by taking the readsorption of alkenes and the following secondary reaction into consideration.It is noted that the contents of alcohol,alkene and alkane decline with the increasing carbon number,showing a slighter declining tendency of alkanes than those of alkenes and alcohols.It is also found that high temperature,space velocity,H2/CO in feed gas and low pressure are preferential for light hydrocarbons and alcohols while against the chain propagation.The effect of space velocity on the product distributions especially on the light products is not obvious.It is noticed that low temperature,space velocity,H2/CO and high pressure lead to high contents of alcohols; high temperature,H2/CO and low space velocity lead to high contents of alkanes.The effect of pressure on the amounts of alkanes is not significant; high space velocity and low temperature,pressure,H2/CO are preferential for alkenes.

  9. Matsuda-Heck reaction with arenediazonium tosylates in water.

    Science.gov (United States)

    Kutonova, Ksenia V; Trusova, Marina E; Stankevich, Andrey V; Postnikov, Pavel S; Filimonov, Victor D

    2015-01-01

    An environmentally friendly Matsuda-Heck reaction with arenediazonium tosylates has been developed for the first time. A range of alkenes was arylated in good to quantitative yields in water. The reaction is significantly accelerated when carried out under microwave heating. The arylation of haloalkylacrylates with diazonium salts has been implemented for the first time. PMID:25977709

  10. Hoveyda-Grubbs type metathesis catalyst immobilized on mesoporous molecular sieves MCM-41 and SBA-15

    Czech Academy of Sciences Publication Activity Database

    Balcar, Hynek; Shinde, Tushar; Žilková, Naděžda; Bastl, Zdeněk

    2011-01-01

    Roč. 7, January (2011), s. 22-28. ISSN 1860-5397 R&D Projects: GA AV ČR IAA400400805; GA AV ČR KAN100400701 Institutional research plan: CEZ:AV0Z40400503 Keywords : alkene metathesis * catalyst immobilization * hybrid catalysis Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.517, year: 2011

  11. Preparative semiconductor photoredox catalysis: An emerging theme in organic synthesis.

    Science.gov (United States)

    Manley, David W; Walton, John C

    2015-01-01

    Heterogeneous semiconductor photoredox catalysis (SCPC), particularly with TiO2, is evolving to provide radically new synthetic applications. In this review we describe how photoactivated SCPCs can either (i) interact with a precursor that donates an electron to the semiconductor thus generating a radical cation; or (ii) interact with an acceptor precursor that picks up an electron with production of a radical anion. The radical cations of appropriate donors convert to neutral radicals usually by loss of a proton. The most efficient donors for synthetic purposes contain adjacent functional groups such that the neutral radicals are resonance stabilized. Thus, ET from allylic alkenes and enol ethers generated allyl type radicals that reacted with 1,2-diazine or imine co-reactants to yield functionalized hydrazones or benzylanilines. SCPC with tertiary amines enabled electron-deficient alkenes to be alkylated and furoquinolinones to be accessed. Primary amines on their own led to self-reactions involving C-N coupling and, with terminal diamines, cyclic amines were produced. Carboxylic acids were particularly fruitful affording C-centered radicals that alkylated alkenes and took part in tandem addition cyclizations producing chromenopyrroles; decarboxylative homo-dimerizations were also observed. Acceptors initially yielding radical anions included nitroaromatics and aromatic iodides. The latter led to hydrodehalogenations and cyclizations with suitable precursors. Reductive SCPC also enabled electron-deficient alkenes and aromatic aldehydes to be hydrogenated without the need for hydrogen gas. PMID:26664577

  12. Rhenium-Catalyzed Deoxydehydration of Diols and Polyols

    DEFF Research Database (Denmark)

    Dethlefsen, Johannes Rytter; Fristrup, Peter

    2015-01-01

    heniumcatalyzeddeoxydehydration (DODH) of a vicinal diol into analkene; this is a model system for abundant polyols like glyceroland sugar alcohols. The present contribution includesa review of early investigations of stoichiometric reactions involvingrhenium, diols, and alkenes followed by a discussion ofthe various catalytic...... systems that have been developed withemphasis on the nature of the reductant, the substrate scope,and mechanistic investigations....

  13. Chloride ion-catalyzed generation of difluorocarbene for efficient preparation of gem-difluorinated cyclopropenes and cyclopropanes

    KAUST Repository

    Wang, Fei

    2011-01-01

    A chloride ion-catalyzed generation of difluorocarbene from a relatively non-toxic and inexpensive precursor, Me3SiCF2Cl (1), under mild and neutral conditions leads to an efficient preparation of gem-difluorocyclopropenes and difluorocyclopropanes through [2 + 1] cycloaddition reactions with alkynes and alkenes, respectively. © 2011 The Royal Society of Chemistry.

  14. Lewis acid-base 1,2-addition reactions: synthesis of pyrylium borates from en-ynoate precursors.

    Science.gov (United States)

    Wilkins, Lewis C; Hamilton, Hugh B; Kariuki, Benson M; Hashmi, A Stephen K; Hansmann, Max M; Melen, Rebecca L

    2016-03-30

    Treatment of methyl (Z)-2-alken-4-ynoates with the strong Lewis acid tris(pentafluorophenyl) borane, B(C6F5)3, yield substituted zwitterionic pyrylium borate species via an intramolecular 6-endo-dig cyclisation reaction. PMID:26435394

  15. Dehydration of Methylcyclohexanol Isomers in the Undergraduate Organic Laboratory and Product Analysis by Gas Chromatography-Mass Spectroscopy (GC-MS)

    Science.gov (United States)

    Clennan, Malgorzata M.; Clennan, Edward L.

    2011-01-01

    Dehydrations of "cis"- and "trans"-2-methylcyclohexanol mixtures were carried out with 60% sulfuric acid at 78-80 [degrees]C as a function of time and the products were identified by gas chromatography-mass spectroscopy (GC-MS) analysis. The compounds identified in the reaction mixtures include alkenes, 1-, 3-, and 4-methylcyclohexenes and…

  16. Exposure of bus and taxi drivers to urban air pollutants as measured by DNA and protein adducts

    DEFF Research Database (Denmark)

    Hemminki, K.; Zhang, L.F.; Krüger, J.;

    1994-01-01

    Urinary 1-hydroxypyrene, lymphocyte DNA adducts, serum protein-bound PAH and hemoglobin-bound alkene adducts were analysed from 4 groups of non-smoking men: urban and suburban bus drivers, taxi drivers and suburban controls. The only differences between the groups were in DNA adducts between subu...

  17. Maleimide-assisted anti-Markovnikov Wacker-type oxidation of vinylarenes using molecular oxygen as a terminal oxidant.

    Science.gov (United States)

    Nakaoka, Sonoe; Murakami, Yuka; Kataoka, Yasutaka; Ura, Yasuyuki

    2016-01-01

    Arylacetaldehydes were successfully synthesized by the anti-Markovnikov Wacker-type oxidation of vinylarenes using 1 atm O2 as a terminal oxidant under mild conditions. Electron-deficient alkenes, such as maleic anhydride and maleimides, were effective additives and would operate as ligands to stabilize the Pd(0) species during the reaction. PMID:26514316

  18. Nuclear Overhauser Effect Spectroscopy: An Advanced Undergraduate Experiment

    Science.gov (United States)

    Huggins, Michael T.; Billimoria, Freida

    2007-01-01

    The stereochemical features of molecules can have far reaching effects in many areas of science including medicinal chemistry, materials chemistry, and supramolecular chemistry. There have been many techniques developed over the years to determine the absolute configuration of alkenes: the R,S configuration of chiral centers and the most stable…

  19. The Palladium-Catalyzed Vinylation and Carbonylation of Bromoindoles and N-Acety1-bromoindoline

    OpenAIRE

    Kasahara, Akira; Izumi, Taeko; Ogata, Hideaki

    1989-01-01

    Abstracts The palladium-catalyzed vinylic substitution reaction of alkenes has been shown to proceed in moderate yields with 5- and 6-bromoindols, and N-acetyl-5-bromoindoline. 4-, 5-, 6-, and 7-Bromoindoles also undergo facile palladium-assisted carbonylation with carbon monoxide in methanol to produce methoxycarbonylindoles in moderate yields.

  20. Synthesis of some novel fluoro isoxazolidine and isoxazoline derivatives using -benzyl fluoro nitrone via cycloaddition reaction in ionic liquid

    Indian Academy of Sciences (India)

    Bhaskar Chakraborty; Govinda Prasad Luitel

    2013-09-01

    1-Butyl-3-methylimidazolium-based ionic liquids are found to accelerate significantly the intermolecular 1,3-dipolar cycloaddition of -benzyl-fluoro nitrone derived in situ from 2,6-difluoro benzaldehyde and -benzylhydroxylamine, with activated alkenes and electron deficient alkynes to afford enhanced rates and improved yields of novel isoxazolidines and isoxazolines.

  1. The Evolution of a Green Chemistry Laboratory Experiment: Greener Brominations of Stilbene

    Science.gov (United States)

    McKenzie, Lallie C.; Huffman, Lauren M.; Hutchison, James E.

    2005-01-01

    The use of green metrics to compare three bromination laboratory procedures demonstrates the effectiveness of an incremental greening process for chemistry curricula. Due to this process, the bromination of alkenes can be introduced to students through the use of a safe, effective, modern practice.

  2. Kinetic analysis of the rotation rate of light-driven unidirectional molecular motors

    NARCIS (Netherlands)

    Klok, Martin; Browne, Wesley R.; Feringa, Ben L.

    2009-01-01

    The combination of a photochemical and a thermal equilibrium in overcrowded alkenes, which is the basis for unidirectional rotation of light-driven molecular rotary motors, is analysed in relation to the actual average rotation rates of such structures. Experimental parameters such as temperature, c

  3. Build/Couple/Pair Strategy Combining the Petasis 3-Component Reaction with Ru-Catalyzed Ring-Closing Metathesis and Isomerization

    DEFF Research Database (Denmark)

    Ascic, Erhad; Le Quement, Sebastian Thordal; Ishøy, Mette;

    2012-01-01

    A “build/couple/pair” pathway for the systematic synthesis of structurally diverse small molecules is presented. The Petasis 3-component reaction was used to synthesize anti-amino alcohols displaying pairwise reactive combinations of alkene moieties. Upon treatment with a ruthenium alkylidene...

  4. Metal-Organic Frameworks Stabilize Solution-Inaccessible Cobalt Catalysts for Highly Efficient Broad-Scope Organic Transformations.

    Science.gov (United States)

    Zhang, Teng; Manna, Kuntal; Lin, Wenbin

    2016-03-01

    New and active earth-abundant metal catalysts are critically needed to replace precious metal-based catalysts for sustainable production of commodity and fine chemicals. We report here the design of highly robust, active, and reusable cobalt-bipyridine- and cobalt-phenanthroline-based metal-organic framework (MOF) catalysts for alkene hydrogenation and hydroboration, aldehyde/ketone hydroboration, and arene C-H borylation. In alkene hydrogenation, the MOF catalysts tolerated a variety of functional groups and displayed unprecedentedly high turnover numbers of ∼2.5 × 10(6) and turnover frequencies of ∼1.1 × 10(5) h(-1). Structural, computational, and spectroscopic studies show that site isolation of the highly reactive (bpy)Co(THF)2 species in the MOFs prevents intermolecular deactivation and stabilizes solution-inaccessible catalysts for broad-scope organic transformations. Computational, spectroscopic, and kinetic evidence further support a hitherto unknown (bpy(•-))Co(I)(THF)2 ground state that coordinates to alkene and dihydrogen and then undergoing σ-complex-assisted metathesis to form (bpy)Co(alkyl)(H). Reductive elimination of alkane followed by alkene binding completes the catalytic cycle. MOFs thus provide a novel platform for discovering new base-metal molecular catalysts and exhibit enormous potential in sustainable chemical catalysis. PMID:26864496

  5. Metal–Organic Frameworks Stabilize Solution-Inaccessible Cobalt Catalysts for Highly Efficient Broad-Scope Organic Transformations

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Teng; Manna, Kuntal; Lin, Wenbin (UC)

    2016-05-06

    New and active earth-abundant metal catalysts are critically needed to replace precious metal-based catalysts for sustainable production of commodity and fine chemicals. We report here the design of highly robust, active, and reusable cobalt-bipyridine- and cobalt-phenanthroline-based metal–organic framework (MOF) catalysts for alkene hydrogenation and hydroboration, aldehyde/ketone hydroboration, and arene C–H borylation. In alkene hydrogenation, the MOF catalysts tolerated a variety of functional groups and displayed unprecedentedly high turnover numbers of ~2.5 × 106 and turnover frequencies of ~1.1 × 105 h–1. Structural, computational, and spectroscopic studies show that site isolation of the highly reactive (bpy)Co(THF)2 species in the MOFs prevents intermolecular deactivation and stabilizes solution-inaccessible catalysts for broad-scope organic transformations. Computational, spectroscopic, and kinetic evidence further support a hitherto unknown (bpy•–)CoI(THF)2 ground state that coordinates to alkene and dihydrogen and then undergoing σ-complex-assisted metathesis to form (bpy)Co(alkyl)(H). Reductive elimination of alkane followed by alkene binding completes the catalytic cycle. MOFs thus provide a novel platform for discovering new base-metal molecular catalysts and exhibit enormous potential in sustainable chemical catalysis.

  6. Morita–Baylis–Hillman reaction of acrylamide with isatin derivatives

    Directory of Open Access Journals (Sweden)

    Radhey M. Singh

    2014-12-01

    Full Text Available The Morita–Baylis–Hillman reaction of acrylamide, as an activated alkene, has seen little development due to its low reactivity. We have developed the reaction using isatin derivatives with acrylamide, DABCO as a promoter and phenol as an additive in acetonitrile. The corresponding aza version with acrylate and acrylonitrile has also been developed resulting in high product yields.

  7. Reactions of Nitroso Hetero Diels-Alder Cycloadducts with Azides: Stereoselective Formation of Triazolines and Aziridines

    Science.gov (United States)

    Bodnar, Brian S.

    2011-01-01

    The addition of azides to acylnitroso hetero Diels-Alder cycloadducts derived from cyclopentadiene affords exo triazolines in excellent yield. The reaction is greatly affected by reducing the level of alkene strain, while sterically demanding azides do not hinder the reaction. Conversion of the triazolines to aziridines is also described. PMID:17429998

  8. Reactions of nitroso hetero-Diels-Alder cycloadducts with azides: stereoselective formation of triazolines and aziridines.

    Science.gov (United States)

    Bodnar, Brian S; Miller, Marvin J

    2007-05-11

    The addition of azides to acylnitroso hetero-Diels-Alder cycloadducts derived from cyclopentadiene affords exo-triazolines in excellent yield. The reaction is greatly affected by the level of alkene strain, while sterically demanding azides do not hinder the reaction. Conversion of the triazolines to aziridines is also described. PMID:17429998

  9. The stereochemistry and confirmation of marrubiin: An X-ray study

    International Nuclear Information System (INIS)

    An X-ray crystallographic determination of the structure of marrubiin confirms the structure and stereochemistry determined chemically. The molecule is highly strained with ring A, a distorted boat and ring B, a flattened chair. The dehydration of marrubiin to an exocyclic alkene is discussed. (author)

  10. Coiodação de alquenos com nucleófilos oxigenados: reações intermoleculares

    Directory of Open Access Journals (Sweden)

    Sanseverino Antonio Manzolillo

    2001-01-01

    Full Text Available A review on the electrophilic addition of iodine to alkenes in the presence of oxygen containing nucleophiles (cohalogenation reaction is presented. The intermolecular reactions are discussed with emphasis in methods of reaction and synthetic applications of the resulting vicinal iodo-functionalized products (iodohydrins, beta-iodoethers and beta-iodocarboxylates.

  11. Carbon dioxide as a carbon source in organic transformation: carbon-carbon bond forming reactions by transition-metal catalysts.

    OpenAIRE

    Tsuji, Yasushi; Fujihara, Tetsuaki

    2012-01-01

    Recent carbon-carbon bond forming reactions of carbon dioxide with alkenes, alkynes, dienes, aryl zinc compounds, aryl boronic esters, aryl halides, and arenes having acidic C-H bonds are reviewed in which transition-metal catalysts play an important role.

  12. Trends in predicted chemoselectivity of cytochrome P450 oxidation

    DEFF Research Database (Denmark)

    Rydberg, Patrik; Lonsdale, Richard; Harvey, Jeremy N;

    2014-01-01

    Prediction of epoxide formation in drug metabolism is a difficult but important task, as epoxide formation is linked to drug toxicity. A comparison of the energy barriers for cytochrome P450 mediated epoxidation of alkenes to the barriers for the hydroxylation of an aliphatic carbon atom next to a...

  13. Hetero [6+3] cycloaddition of fulvenes with N-alkylidene glycine esters: a facile synthesis of the delavayine and incarvillateine framework.

    Science.gov (United States)

    Hong, Bor-Cherng; Gupta, Arun Kumar; Wu, Ming-Fun; Liao, Ju-Hsiou; Lee, Gene-Hsiang

    2003-05-15

    [reaction: see text] In contrast to the [3+2] or [4+3] cycloaddition of N-metalated azomethine ylides and various alkenes, N-benzylidene glycine ethyl ester reacts with fulvenes to give the hetero [6+3] cycloaddition adducts with high stereoselectivity, constituting an efficient and novel route to [2]pyrindines. PMID:12735753

  14. Iron-catalyzed coupling reactions of vinylic chalcogenides with Grignard reagents

    International Nuclear Information System (INIS)

    A general new method for the cross-coupling reaction between vinylic selenides and tellurides and Grignard reagents catalyzed by Fe(acac)3 at room temperature is described. This reaction proceeded with retention of configuration, providing the respective alkenes in good to excellent yields. This method is also efficient for the coupling reaction of divinyl chalcogenides with Grignard reagents. (author)

  15. Z-Selective copper-catalyzed asymmetric allylic alkylation with Grignard reagents.

    Science.gov (United States)

    Giannerini, Massimo; Fañanás-Mastral, Martín; Feringa, Ben L

    2012-03-01

    Allylic gem-dichlorides undergo regio- and enanantioselective (er up to 99:1) copper-catalyzed allylic alkylation with Grignard reagents affording chiral Z-vinyl chlorides. This highly versatile class of synthons can be subjected to Suzuki cross coupling affording optically active Z-alkenes and 1,3-cis,trans dienes. PMID:22352853

  16. Z-Selective Copper-Catalyzed Asymmetric Allylic Alkylation with Grignard Reagents

    OpenAIRE

    Giannerini, Massimo; Fananas-Mastral, Martin; Feringa, Ben L.; Fañanás-Mastral, Martín

    2012-01-01

    Allylic gem-dichlorides undergo regio- and enanantioselective (er up to 99:1) copper-catalyzed allylic alkylation with Grignard reagents affording chiral Z-vinyl chlorides. This highly versatile class of synthons can be subjected to Suzuki cross coupling affording optically active Z-alkenes and 1,3-cis,trans dienes.

  17. Iron-catalyzed coupling reactions of vinylic chalcogenides with Grignard reagents

    Energy Technology Data Exchange (ETDEWEB)

    Silveira, Claudio C.; Mendes, Samuel R.; Wolf, Lucas, E-mail: silveira@quimica.ufsm.b [Universidade Federal de Santa Maria (UFSM), RS (Brazil). Centro de Tecnologia. Dept. de Quimica

    2010-07-01

    A general new method for the cross-coupling reaction between vinylic selenides and tellurides and Grignard reagents catalyzed by Fe(acac){sub 3} at room temperature is described. This reaction proceeded with retention of configuration, providing the respective alkenes in good to excellent yields. This method is also efficient for the coupling reaction of divinyl chalcogenides with Grignard reagents. (author)

  18. Determination of lipid oxidation products in vegetable oils and marine omega-3 supplements

    Directory of Open Access Journals (Sweden)

    Rune Blomhoff

    2011-06-01

    Full Text Available Background : There is convincing evidence that replacing dietary saturated fats with polyunsaturated fats (PUFA decreases risk of cardiovascular diseases. Therefore, PUFA rich foods such as vegetable oils, fatty fish, and marine omega-3 supplements are recommended. However, PUFA are easily oxidizable and there is concern about possible negative health effects from intake of oxidized lipids. Little is known about the degree of lipid oxidation in such products. Objective : To assess the content of lipid oxidation products in a large selection of vegetable oils and marine omega-3 supplements available in Norway. Both fresh and heated vegetable oils were studied. Design : A large selection of commercially available vegetable oils and marine omega-3 supplements was purchased from grocery stores, pharmacies, and health food stores in Norway. The content of lipid oxidation products were measured as peroxide value and alkenal concentration. Twelve different vegetable oils were heated for a temperature (225°C and time (25 minutes resembling conditions typically used during cooking. Results : The peroxide values were in the range 1.04–10.38 meq/kg for omega-3 supplements and in the range 0.60–5.33 meq/kg for fresh vegetable oils. The concentration range of alkenals was 158.23–932.19 nmol/mL for omega-3 supplements and 33.24–119.04 nmol/mL for vegetable oils. After heating, a 2.9–11.2 fold increase in alkenal concentration was observed for vegetable oils. Conclusions : The contents of hydroperoxides and alkenals in omega-3 supplements are higher than in vegetable oils. After heating vegetable oils, a large increase in alkenal concentration was observed.

  19. Transformation of Oximes and Alcohols to Carbonyl Compounds Using Amberlite IRA-400 Supported Chromic Acid in the Presence of Zirconium Tetrachloride

    Institute of Scientific and Technical Information of China (English)

    BAHRAMI, Kiumars; KHODAEIMohammad-Mehdi; GORGIN-KARAJI, Usef

    2009-01-01

    A wide variety of oximes and alcohols were efficiently converted to their corresponding aldehydes and ketones in good to excellent yields using amberlite IRA-400 supported chromic acid in the presence of zirconium tetrachlo-ride in refluxing acetonitrile-H2O. Selective oxidation of oximes and alcohols in the presence of other functional groups such as acetal, hydrazone, aldehyde, ether and alkene can be considered as a noteworthy advantage of this method. A wide variety of oximes and alcohols were efficiently converted to their corresponding aldehydes and ke-tones in good to excellent yields using amberlite IRA-400 supported chromic acid in the presence of zirconium tet-rachloride in refluxing acetonitrile-H2O. Selective oxidation of oximes and alcohols in the presence of other func-tional groups such as acetal, hydrazone, aldehyde, ether and alkene can be considered as a noteworthy advantage of this method.

  20. Pollination by sexual deception-it takes chemistry to work.

    Science.gov (United States)

    Bohman, Björn; Flematti, Gavin R; Barrow, Russell A; Pichersky, Eran; Peakall, Rod

    2016-08-01

    Semiochemicals are of paramount importance in sexually deceptive plants. These plants sexually lure specific male insects as pollinators by chemical and physical mimicry of the female of the pollinator. The strategy has evolved repeatedly in orchids, with a wide diversity of insect groups exploited. Chemical communication systems confirmed by field bioassays include: alkenes and alkanes in bee pollinated Ophrys species, keto-acid and hydroxy-acids in scoliid wasp pollinated O. speculum, and cyclohexanediones and pyrazines in thynnine wasp pollinated Chiloglottis and Drakaea orchids, respectively. In Ophrys, stearoyl-acyl carrier protein desaturase (SAD) enzymes have been confirmed to control species level variation in alkene double bond position. The production of cyclohexanediones in Chiloglottis unexpectedly depends on UVB light, a phenomenon unknown for other plant specialised metabolites. Potential biosynthetic pathways for other systems are explored, and alternative approaches to further accelerate chemical discovery in sexually deceptive plants are proposed. PMID:27368084

  1. Metal-Organic Frameworks as Catalysts for Oxidation Reactions.

    Science.gov (United States)

    Dhakshinamoorthy, Amarajothi; Asiri, Abdullah M; Garcia, Hermenegildo

    2016-06-01

    This Concept is aimed at describing the current state of the art in metal-organic frameworks (MOFs) as heterogeneous catalysts for liquid-phase oxidations, focusing on three important substrates, namely, alkenes, alkanes and alcohols. Emphases are on the nature of active sites that have been incorporated within MOFs and on future targets to be set in this area. Thus, selective alkene epoxidation with peroxides or oxygen catalyzed by constitutional metal nodes of MOFs as active sites are still to be developed. Moreover, no noble metal-free MOF has been reported to date that can act as a general catalyst for the aerobic oxidation of primary and secondary aliphatic alcohols. In contrast, in the case of alkanes, a target should be to tune the polarity of MOF internal pores to control the outcome of the autooxidation process, resulting in the selective formation of alcohol/ketone mixtures at high conversion. PMID:27113486

  2. Preparation and characterization of QDs all-silicon

    Energy Technology Data Exchange (ETDEWEB)

    Giovannozzi, Andrea M.; Rocchia, Massimiliano; Amato, Giampiero [Electromagnetism Division, National Institute of Metrological Research, Torino (Italy); Troia, Adriano [Thermodynamics Division, National Institute of Metrological Research, Torino (Italy); Bertinetti, Luca [Dipartimento di Chimica IFM, University of Torino (Italy)

    2009-07-15

    Quantum Dots (QDs) all- silicon have been prepared through ultrasound treatments of light-emitting porous silicon layers (PSL) obtained from electrochemically etching of a p type crystalline silicon (c-Si). The sonication treatments enabled to separate the PS nanoparticles (porousfraction) from the bulk c-Si as well as to mechanically reduce their dimensions. The ultrasounds processes have been carried out in two different organic solvents (toluene and tetrahydrofurane, THF) which enabled us to obtaine silicon QD emitting light in the blue-green part of the visible spectrum (estimated QDs dimension below 4nm). Moreover, by adding the proper chemicals in the solvents, such as alkenes or {omega}-carboxy alkenes, we have stabilized the QDs achieving surface modification together with size reduction. Photoluminescence spectra of the QDs and TEM images re presented in this paper. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  3. Observation of the simplest Criegee intermediate CH2OO in the gas-phase ozonolysis of ethylene.

    Science.gov (United States)

    Womack, Caroline C; Martin-Drumel, Marie-Aline; Brown, Gordon G; Field, Robert W; McCarthy, Michael C

    2015-03-01

    Ozonolysis is one of the dominant oxidation pathways for tropospheric alkenes. Although numerous studies have confirmed a 1,3-cycloaddition mechanism that generates a Criegee intermediate (CI) with form R1R2COO, no small CIs have ever been directly observed in the ozonolysis of alkenes because of their high reactivity. We present the first experimental detection of CH2OO in the gas-phase ozonolysis of ethylene, using Fourier transform microwave spectroscopy and a modified pulsed nozzle, which combines high reactant concentrations with rapid sampling and sensitive detection. Nine other product species of the O3 + C2H4 reaction were also detected, including formaldehyde, formic acid, dioxirane, and ethylene ozonide. The presence of all these species can be attributed to the unimolecular and bimolecular reactions of CH2OO, and their abundances are in qualitative agreement with published mechanisms and rate constants. PMID:26601145

  4. Autoignition behavior of unsaturated hydrocarbons in the low and high temperature regions

    Energy Technology Data Exchange (ETDEWEB)

    Mehl, M; Pitz, W J; Westbrook, C K; Yasunaga, K; Curran, H J

    2010-02-22

    In this work, numerical and experimental techniques are used to investigate the effect of the position of the double bond on the ignition properties of pentene and hexene linear isomers. A wide-range kinetic model for the oxidation of C{sub 5}-C{sub 6} linear alkenes has been developed. Literature rapid compression machine data were used to validate the model at low temperatures and new shock tube experiments were performed in order to assess the behavior of the considered alkenes in the high temperature region. Some interesting inversions in the relative reactivity of the isomers were detected. The model successfully reproduced the measured behavior and allowed to explain the reason of these reactivity changes. The information gathered will be applied to the development of the kinetic mechanisms of larger unsaturated surrogate components.

  5. Radiation curable resistant coatings and their preparation

    International Nuclear Information System (INIS)

    A prepolymer containing unsaturated hydrocarbon groups is prepared and mixed on a roller mill with one or more acrylic ester monomers and various additives to make a coating formulation of a desired viscosity. In general, low viscosity formulations are used for overprint varnishes, on paper or foil, or with pigments, for certain types of printing inks. Higher viscosity formulations are used to apply thick films on panels, tiles, or other bodies. Thin films are cured to hardness by brief exposure to ultraviolet light. Thicker films require more energetic radiation such as plasma arc and electron beam radiation. The prepolymers particularly useful for making such radiation curable coatings are the reaction products of polyether polyols and bis- or polyisocyanates and hydroxy alkenes or acrylic (or methacrylic) hydroxy esters, and, likewise, reactive polyamides modified with dicarboxy alkenes, their anhydrides or esters. A small amount of wax incorporated in the coating formulations results in coatings with release characteristics similar to those of PTFE coatings. 10 claims

  6. Cage-like bifunctional chelators, copper-64 radiopharmaceuticals and PET imaging using the same

    Energy Technology Data Exchange (ETDEWEB)

    Conti, Peter S.; Cai, Hancheng; Li, Zibo; Liu, Shuanglong

    2016-08-02

    Disclosed is a class of versatile Sarcophagine based bifunctional chelators (BFCs) containing a hexa-aza cage for labeling with metals having either imaging, therapeutic or contrast applications radiolabeling and one or more linkers (A) and (B). The compounds have the general formula ##STR00001## where A is a functional group selected from group consisting of an amine, a carboxylic acid, an ester, a carbonyl, a thiol, an azide and an alkene, and B is a functional group selected from the group consisting of hydrogen, an amine, a carboxylic acid, and ester, a carbonyl, a thiol, an azide and an alkene. Also disclosed are conjugate of the BFC and a targeting moiety, which may be a peptide or antibody. Also disclosed are metal complexes of the BFC/targeting moiety conjugates that are useful as radiopharmaceuticals, imaging agents or contrast agents.

  7. Analysis of unregulated emissions from an off-road diesel engine during realistic work operations

    Science.gov (United States)

    Lindgren, Magnus; Arrhenius, Karine; Larsson, Gunnar; Bäfver, Linda; Arvidsson, Hans; Wetterberg, Christian; Hansson, Per-Anders; Rosell, Lars

    2011-09-01

    Emissions from vehicle diesel engines constitute a considerable share of anthropogenic emissions of pollutants, including many non-regulated compounds such as aromatic hydrocarbons and alkenes. One way to reduce these emissions might be to use fuels with low concentrations of aromatic hydrocarbons, such as Fischer-Tropsch (F-T) diesels. Therefore this study compared Swedish Environmental Class 1 diesel (EC1) with the F-T diesel fuel Ecopar™ in terms of emissions under varied conditions (steady state, controlled transients and realistic work operations) in order to identify factors influencing emissions in actual operation. Using F-T diesel reduced emissions of aromatic hydrocarbons, but not alkenes. Emissions were equally dependent on work operation character (load, engine speed, occurrence of transients) for both fuels. There were indications that the emissions originated from unburnt fuel, rather than from combustion products.

  8. Radiation-chemical oxidation of adamantylideneadamantane with dioxetane formation

    International Nuclear Information System (INIS)

    Liquid-phase radiation-chemical oxidation of adamantylideneadamantane with 1,2-dioxetane formation is studied. Gamma-irradiation is carried out with the doses up to 17.2 kGy, the dose rate being 1.2 Gy/s. It is shown that the main chance of radiation-chemical oxidation of this alkene is radical expoxidation. One of the sources of radical generation in acetone is the process of oxygen quenching the triplet acetone. In the presence of intermediaries passing excitation to dissolved oxygene in solvents with high yield of excited states generation 1O2 is produced, and alkene is oxidized to dioxetane. Therewith, the epoxide yield is decreased, the dioxetane and epoxide yield ratio is defined by competition between reactions of O2 and intermediaries leading to 1O2 or radical products

  9. Liquid chromatography/coordination ion spray-mass spectrometry for the analysis of rubber vulcanization products.

    Science.gov (United States)

    Hayen, Heiko; Alvarez-Grima, M Montserrat; Debnath, Subhas C; Noordermeer, Jacques W M; Karst, Uwe

    2004-02-15

    Liquid chromatography/coordination ion spray-mass spectrometry has been used for the identification of reaction products in a model rubber vulcanization process. After LC separation using reversed-phase conditions, AgBF(4) in acetonitrile was added, and strong signals were observed for silica-rubber coupling agents and products of the reaction between these and alkenes. The method performs best for substances containing sulfur chains with chain lengths between two and eight sulfur atoms, but sulfur-free compounds containing triethoxysilyl groups were detected as well. For the latter, the postcolumn addition of NaBF(4) proved to be a suitable alternative. Besides the coupling agents, various reaction products, including sulfur-chain bridged alkenes were identified. PMID:14961739

  10. Catalytic hydrogenation using complexes of base metals with tridentate ligands

    Energy Technology Data Exchange (ETDEWEB)

    Vasudevan, Kalyan V.; Zhang, Guoqi; Hanson, Susan K.

    2016-09-06

    Complexes of cobalt and nickel with tridentate ligand PNHP.sup.R are effective for hydrogenation of unsaturated compounds. Cobalt complex [(PNHP.sup.Cy)Co(CH.sub.2SiMe.sub.3)]BAr.sup.F.sub.4 (PNHP.sup.Cy=bis[2-(dicyclohexylphosphino)ethyl]amine, BAr.sup.F.sub.4=B(3,5-(CF.sub.3).sub.2C.sub.6H.sub.3).sub.4)) was prepared and used with hydrogen for hydrogenation of alkenes, aldehydes, ketones, and imines under mild conditions (25-60.degree. C., 1-4 atm H.sub.2). Nickel complex [(PNHP.sup.Cy)Ni(H)]BPh.sub.4 was used for hydrogenation of styrene and 1-octene under mild conditions. (PNP.sup.Cy)Ni(H) was used for hydrogenating alkenes.

  11. The thermal effects on the methanol-to-olefins reaction: A modelling and experimental approach

    OpenAIRE

    Pereira, Sara Filipa Fagulha

    2015-01-01

    With the projection of an increasing world population, hand-in-hand with a journey towards a bigger number of developed countries, further demand on basic chemical building blocks, as ethylene and propylene, has to be properly addressed in the next decades. The methanol-to-olefins (MTO) is an interesting reaction to produce those alkenes using coal, gas or alternative sources, like biomass, through syngas as a source for the production of methanol. This technology has been widely applied s...

  12. Investigations into the occurrence of penetrating iodine species. Pt. 2

    International Nuclear Information System (INIS)

    Investigations on the formation of penetrating iodine species have been continued. Alcohol (methanol, ethanol) and alkene (ethylene, propylene) vapour-air mixtures were radiolyzed with iodine in a Co-60 gamma source. The concentration and the irradiation doses were varied (4,45 E + 04-6,2 E + 06 rad). The gaseous products were analyzed qualitatively and quantitatively by an ECD and a MSD detector for iodine compounds difficult to separate. (orig.)

  13. Friese Front Alk / Zeekoet: Oktober / November 2012, cruise rapport

    OpenAIRE

    Leopold, M.F.; Bemmelen, van, R.S.A.; Kuhn, S; Lagerveld, S

    2012-01-01

    Het Friese Front, zoals omschreven en geografisch aangeduid in het rapport van Lindeboom et al. (2005) zal binnenkort worden aangewezen als Natura 2000 gebied. Vanwege de bijzondere status van het gebied is het belangrijk om te weten welke aantallen Zeekoeten het gebied bezoeken. De aantallen moeten daarom worden gevolgd, maar een monitoringsprogramma dat de benodigde gegevens kan aanleveren is er nog niet. Daarbij is het niet uitgesloten dat ook de aantallen Alken die het Friese Front bezoek...

  14. Metal-catalysed organic transformations in water: From bromination to polymerisation

    Indian Academy of Sciences (India)

    Manish Bhattacharjee; Braja N Patra

    2006-11-01

    Reaction of ,-unsaturated aromatic carboxylic acids with KBr and H2O2 in the presence of Na2MoO4$\\cdot$H2O in aqueous medium affords -bromo alkenes in high yields. Metallocene dichlorides, Cp2MCl2 (M = Ti, Zr, or V) catalyse polymerisation of olefins in aqueous medium to afford high molecular weight polymers with low molecular weight distribution.

  15. Identification of organic matter sources in sulfidic late Holocene Antarctic fjord sediments from fossil rDNA sequence analysis

    OpenAIRE

    Coolen, M.J.L.; Volkman, J.K.; Abbas, B.; Muyzer, G; Schouten, S.; Sinninghe Damsté, J. S.

    2007-01-01

    The 18S ribosomal DNA (rDNA) isolated from sulfidic Holocene sediments and particulate organic matter in the water column of the stratified Small Meromictic Basin (SMB) in Ellis Fjord (eastern Antarctica) was analyzed to identify possible biological sources of organic matter. Previous work had shown that the sediments contained numerous diatom frustules and high contents of a highly branched isoprenoid (HBI) C25:2 alkene (which is a specific biomarker of certain species of the diatom genera N...

  16. Phosphine-Based Z‑Selective Ruthenium Olefin Metathesis Catalysts

    OpenAIRE

    Smit, Wietse; Koudriavtsev, Vitali; Occhipinti, Giovanni; Törnroos, Karl Wilhelm; Jensen, Vidar Remi

    2016-01-01

    Whereas a number of highly Z-selective ruthenium-based olefin metathesis catalysts bearing N-heterocyclic carbene ligands have been reported in recent years, Zselectivity has so far been difficult to achieve for phosphinebased catalysts. Guided by predictive density functional theory (DFT) calculations, we have developed phosphine-based ruthenium olefin metathesis catalysts giving 70−95% of the Zisomer product in homocoupling of terminal alkenes such as allylbenzene, 1...

  17. Transformation of methylcyclohexane on an FCC catalyst

    Directory of Open Access Journals (Sweden)

    A. Rabeharitsara

    2003-06-01

    Full Text Available The transformation of methylcyclohexane at 723 K over on a USHY sample and on an FCC catalyst composed of 30% USHY and 70% matrix containing 25% Al2O3 was studied. With both samples, C2-C7 alkenes and alkanes, cyclopentane and methylcyclopentane (cracking products, dimethylcyclopentanes and ethylcyclopentane (isomers and aromatics appeared as primary products. The activity and selectivity of fresh samples as well as the influence of coke deposits on porosity and selectivity are discussed.

  18. Palladium-Catalyzed C–C Bond Formations via Activation of Carboxylic Acids and Their Derivatives

    OpenAIRE

    Song, Bingrui

    2013-01-01

    Applications of carboxylic acids and their derivatives in transition metal-catalyzed cross-coupling reactions regio-selectively forming Csp3-Csp2, and Csp2-Csp2 bonds were explored in this thesis. Several important organic building blocks such as aryl acetates, diaryl acetates, imines, ketones, biaryls, styrenes and polysubstituted alkenes were successfully accessed from carboxylic acids and their derivatives by the means of C–H activation and decarboxylative cross-couplings. An efficient ...

  19. A mechanism of haloalkene-induced renal carcinogenesis.

    OpenAIRE

    Dekant, W; Vamvakas, S; Koob, M; Köchling, A; Kanhai, W; Müller, D.; Henschler, D

    1990-01-01

    Several halogenated alkenes are nephrotoxic; some others induce renal tubular adenocarcinomas in rodents after lifelong administration. A bioactivation mechanism accounting for the organ-selective tumor induction has been elucidated: conjugation of the parent compounds with glutathione (GSH), catalyzed by hepatic GSH S-transferases, results in the formation of haloalkyl and halovinyl glutathione S-conjugates. Formation of S-conjugates (identified by NMR and mass spectrometry) could be demonst...

  20. Stereocontrolled total synthesis of neuroprotectin D1 / protectin D1 and its aspirin-triggered stereoisomer

    OpenAIRE

    Petasis, Nicos A.; Yang, Rong; Winkler, Jeremy W.; Zhu, Min; Uddin, Jasim; Bazan, Nicolas G.; Serhan, Charles N.

    2012-01-01

    Neuroprotectin D1 / protectin D1, a potent anti-inflammatory, proresolving, and neuroprotective lipid mediator derived biosynthetically from docosahexaenoic acid, was prepared in enantiomerically pure form via total organic synthesis. The synthetic strategy is highly stereocontrolled and convergent, featuring epoxide opening of glycidol starting materials for the introduction of the 10(R) and 17(S) hydroxyl groups. The desired alkene Z geometry was secured via the cis-reduction of alkyne prec...

  1. Total Synthesis of Laulimalide: Assembly of the Fragments and Completion of the Synthesis of the Natural Product and a Potent Analogue

    OpenAIRE

    Trost, Barry M.; Amans, Dominique; Seganish, W. Michael; Chung, Cheol K.

    2012-01-01

    In this manuscript, we report the full account of our efforts to couple the northern and the southern building blocks, whose synthesis were described in the preceding paper, along with the modifications required which ultimately lead to a successful synthesis of laulimalide. Key highlights include an exceptionally efficient and atom-economical intramolecular ruthenium-catalyzed alkene-alkyne coupling to build the macrocycle followed by a highly stereoselective 1,3-allylic isomerization promot...

  2. Photocatalytic generation of N-centered hydrazonyl radicals: a strategy for hydroamination of β,γ-unsaturated hydrazones.

    Science.gov (United States)

    Hu, Xiao-Qiang; Chen, Jia-Rong; Wei, Qiang; Liu, Feng-Lei; Deng, Qiao-Hui; Beauchemin, André M; Xiao, Wen-Jing

    2014-11-01

    A visible-light photocatalytic generation of N-centered hydrazonyl radicals has been accomplished for the first time. This approach allows efficient intramolecular addition of hydrazonyl radical to terminal alkenes, thus providing hydroamination and oxyamination products in good yields. Importantly, the protocol involves deprotonation of an N-H bond and photocatalytic oxidation to an N-centered radical, thus obviating the need to prepare photolabile amine precursors or the stoichiometric use of oxidizing reagents. PMID:25513705

  3. The inverse electron demand Diels–Alder click reaction in radiochemistry‡

    OpenAIRE

    Reiner, Thomas; Zeglis, Brian M

    2013-01-01

    The inverse electron-demand Diels-Alder (IEDDA) cycloaddition between 1,2,4,5-tetrazines and strained alkene dienophiles is an emergent variety of catalyst-free ‘click’ chemistry that has the potential to have a transformational impact on the synthesis and development of radiopharmaceuticals. The ligation is selective, rapid, high-yielding, clean, and bioorthogonal and, since its advent in 2008, has been employed in a wide variety of chemical settings. In radiochemistry, the reaction has prov...

  4. A rapidly photo-activatable light-up fluorescent nucleoside and its application in DNA base variation sensing.

    Science.gov (United States)

    He, Zhiyong; Chen, Yuqi; Wang, Yafen; Wang, Jiaqi; Mo, Jing; Fu, Boshi; Wang, Zijing; Du, Yuhao; Zhou, Xiang

    2016-06-30

    A new DNA building block (d(Tet)U) bearing a tetrazole and allyloxy group at N-phenyl ring linked through an aminopropynyl linker to the 5-position of 2'-deoxyuridine was synthesized. The modified DNA can be lit up via a photoinduced intramolecular tetrazole-alkene cycloaddition reaction, but quenched when the fully-matched double strand is formed. This conspicuous difference in fluorescence could open a door for DNA single nucleotide polymorphism (SNP) typing. PMID:27315545

  5. New Methodology for the Synthesis of Thiobarbiturates Mediated by Manganese(III Acetate

    Directory of Open Access Journals (Sweden)

    Patrice Vanelle

    2012-04-01

    Full Text Available A three step synthesis of various thiobarbiturate derivatives 17–24 was established. The first step is mediated by Mn(OAc3, in order to generate a carbon-carbon bond between a terminal alkene and malonate. Derivatives 1–8 were obtained in moderate to good yields under mild conditions. This key step allows synthesis of a wide variety of lipophilic thiobarbiturates, which could be tested for their anticonvulsive or anesthesic potential.

  6. The effect of non-migrating tides on the equatorial electrojet

    OpenAIRE

    Hermann Lühr; Martin Rother; Häusler, K.; Alken, P.; Maus, S.

    2008-01-01

    The climatological model of the equatorial electrojet, EEJM-1, derived from Ørsted, CHAMP and SAC-C satellite measurements [Alken and Maus, 2007] provides the opportunity to investigate the longitudinal variation of the current strength in detail. Special emphasis is put in this paper on the effect of non-migrating tides. We have found that the influence of the diurnal eastward propagating mode with wavenumber 3, DE3, is particularly strong. In polar orbiting satellite observations the DE3 ti...

  7. ANTIMICROBIAL ACTIVITY OF EUGENOL DERIVATIVES Antimikrobielle Aktivität EUGENOL DERIVATE

    OpenAIRE

    George Eyambe, Luis Canales and Bimal K. Banik

    2011-01-01

    The antibacterial properties of the clove plant are due to the presence of eugenol, an aromatic phenolic compound. Eugenol was isolated from clove by stem distillation. The alkene group in eugenol was epoxidized resulting in the synthesis of epoxide-eugenol. The heterocyclic ring in epoxide was cleaved to a bromoalcohol derivative. The compounds synthesized epoxideeugenol, bromo alcohol and euginol were tested for antimicrobial activity against Staphylococcus aureus (ATCC 25923). Epoxide-euge...

  8. Effect of Coexistent Hydrogen on the Selective Production of Ethane by Dehydrogenative Methane Coupling through Dielectric-Barrier Discharge under Ordinary Pressure at an Ambient Temperature

    Directory of Open Access Journals (Sweden)

    Katsuya Konno

    2014-01-01

    Full Text Available The effect of coexistence of hydrogen on the product selectivity to ethane from methane by dielectric-barrier discharge (DBD reactor was examined experimentally under ordinary pressure without use of catalyst and external heating. By the dilution of methane with hydrogen, both the increase of methane conversion and the decrease of alkene production were observed, improving the selectivities to ethane by ca. 70%.

  9. A Synthesis of the Tricyclic Core Structure of FR901483 Featuring an Ugi Four-Component Coupling and a Remarkably Selective Elimination Reaction1

    OpenAIRE

    Seike, Hirofumi; Sorensen, Erik J.

    2008-01-01

    Three key reactions, an efficient Ugi four-component coupling, a regiospecific, base-mediated elimination reaction, and an intramolecular nitrone/alkene [3+2] cycloaddition, were used to achieve an effective synthesis of the tricyclic molecular framework of the immunosuppressant FR901483. The outcome of a control experiment supports the idea that an internal deprotonation by an alkoxide ion is the origin of the site selectivity observed in the base-induced elimination of hydroxy mesylate 17.

  10. Enantiospecific Alkynylation of Alkylboronic Esters

    OpenAIRE

    Wang, Yahui; Noble, Adam; Myers, Eddie L.; Aggarwal, Varinder K.

    2016-01-01

    Enantioenriched secondary and tertiary alkyl pinacolboronic esters undergo enantiospecific deborylative alkynylation through a Zweifel-type alkenylation followed by a 1,2-elimination reaction. The process involves the use of α-lithio vinyl bromide or vinyl carbamate, species whose application to Zweifel-type reactions has not previously been explored. The resulting functionalized 1,1-disubstituted alkenes undergo facile base-mediated elimination to generate the terminal alkyne products in hig...

  11. Transmetallation Versus β-Hydride Elimination : The Role of 1,4 Benzoquinone in Chelation-Controlled Arylation Reactions with Arylboronic Acids

    OpenAIRE

    Sköld, Christian; Kleimark, Jonatan; Trejos, Alejandro; Odell, Luke R; Nilsson Lill, Sten O.; Norrby, Per-Ola; Larhed, Mats

    2012-01-01

    AbstractThe formation of an atypical, saturated, diarylated, Heck/Suzuki, domino product produced under oxidative Heck reaction conditions, employing arylboronic acids and a chelating vinyl ether, has been investigated by DFT calculations. The calculations highlight the crucial role of 1,4-benzoquinone (BQ) in the reaction. In addition to its role as an oxidant of palladium, which is necessary to complete the catalytic cycle, this electron-deficient alkene opens up a low-energy reaction pathw...

  12. The chemistry of half-sandwich vanadium imido-amido complexes

    OpenAIRE

    Batinas, Aurora Alexandra

    2009-01-01

    Many important industrial processes make use of catalyzed reactions. One of the best known catalytic processes is the production of polyethylene and polypropylene plastics used in everyday life by means of olefin polymerisation (carbon-carbon bond formation). Another catalyzed chemical transformation that received widespread attention is the formation of carbon-heteroatom bonds. The hydroamination reaction, for instance, creates a carbon-nitrogen bond from amines and alkenes or alkynes. It is...

  13. Rhodium(I) catalyzed [2+2+2] cycloaddition reactions: experimental and theoretical studies

    OpenAIRE

    Dachs Soler, Anna

    2011-01-01

    The [2+2+2] cycloaddition reaction involves the formation of three carbon-carbon bonds in one single step using alkynes, alkenes, nitriles, carbonyls and other unsaturated reagents as reactants. This is one of the most elegant methods for the construction of polycyclic aromatic compounds and heteroaromatic, which have important academic and industrial uses. The thesis is divided into ten chapters including six related publications. The first study based on the Wilkinson’s catalyst, RhCl(PPh3)...

  14. Highly Regioselective Indoline Synthesis under Nickel/Photoredox Dual Catalysis

    OpenAIRE

    Tasker, Sarah Z.; Jamison, Timothy F.

    2015-01-01

    Nickel/photoredox catalysis is used to synthesize indolines in one step from iodoacetanilides and alkenes. Very high regioselectivity for 3-substituted indoline products is obtained for both aliphatic and styrenyl olefins. Mechanistic investigations indicate that oxidation to Ni(III) is necessary to perform the difficult C–N bond-forming reductive elimination, producing a Ni(I) complex which in turn is reduced to Ni(0). This process serves to further demonstrate the utility of photoredox cata...

  15. Nitro-Grela-type complexes containing iodides – robust and selective catalysts for olefin metathesis under challenging conditions

    Directory of Open Access Journals (Sweden)

    Andrzej Tracz

    2015-10-01

    Full Text Available Iodide-containing nitro-Grela-type catalysts have been synthesized and applied to ring closing metathesis (RCM and cross metathesis (CM reactions. These new catalysts have exhibited improved efficiency in the transformation of sterically, non-demanding alkenes. Additional steric hindrance in the vicinity of ruthenium related to the presence of iodides ensures enhanced catalyst stability. The benefits are most apparent under challenging conditions, such as very low reaction concentrations, protic solvents or with the occurrence of impurities.

  16. Enantiospecific total syntheses of (-)-valeranone

    OpenAIRE

    Srikrishna, A; Viswajanani, R; C.Dinesh

    2004-01-01

    Two convenient methodologies are described for the enantiospecific synthesis of (-)-valeranone. The hydrindanone I, obtained from the readily and abundantly available monoterpene (R)-carvone, was converted into the ketoaldehyde II via an alkene. In another direction the lactone III, obtained from the hydrindanone I, has been elaborated into the ketoaldehyde II employing two methodologies. Intramol. aldol condensation followed by hydrogenation transformed the ketoaldehyde II into (-)-valera...

  17. Mono- and dialkyl glycerol ether lipids in anaerobic bacteria: biosynthetic insights from the mesophilic sulfate reducer Desulfatibacillum alkenivorans PF2803T.

    Science.gov (United States)

    Grossi, Vincent; Mollex, Damien; Vinçon-Laugier, Arnauld; Hakil, Florence; Pacton, Muriel; Cravo-Laureau, Cristiana

    2015-05-01

    Bacterial glycerol ether lipids (alkylglycerols) have received increasing attention during the last decades, notably due to their potential role in cell resistance or adaptation to adverse environmental conditions. Major uncertainties remain, however, regarding the origin, biosynthesis, and modes of formation of these uncommon bacterial lipids. We report here the preponderance of monoalkyl- and dialkylglycerols (1-O-alkyl-, 2-O-alkyl-, and 1,2-O-dialkylglycerols) among the hydrolyzed lipids of the marine mesophilic sulfate-reducing proteobacterium Desulfatibacillum alkenivorans PF2803T grown on n-alkenes (pentadec-1-ene or hexadec-1-ene) as the sole carbon and energy source. Alkylglycerols account for one-third to two-thirds of the total cellular lipids (alkylglycerols plus acylglycerols), depending on the growth substrate, with dialkylglycerols contributing to one-fifth to two-fifths of the total ether lipids. The carbon chain distribution of the lipids of D. alkenivorans also depends on that of the substrate, but the chain length and methyl-branching patterns of fatty acids and monoalkyl- and dialkylglycerols are systematically congruent, supporting the idea of a biosynthetic link between the three classes of compounds. Vinyl ethers (1-alken-1'-yl-glycerols, known as plasmalogens) are not detected among the lipids of strain PF2803T. Cultures grown on different (per)deuterated n-alkene, n-alkanol, and n-fatty acid substrates further demonstrate that saturated alkylglycerols are not formed via the reduction of hypothetic alken-1'-yl intermediates. Our results support an unprecedented biosynthetic pathway to monoalkyl/monoacyl- and dialkylglycerols in anaerobic bacteria and suggest that n-alkyl compounds present in the environment can serve as the substrates for supplying the building blocks of ether phospholipids of heterotrophic bacteria. PMID:25724965

  18. Preparation and Reaction Chemistry of Novel Silicon-Substituted 1,3-Dienes

    OpenAIRE

    Partha P. Choudhury; Mark E. Welker

    2015-01-01

    2-Silicon-substituted 1,3-dienes containing non transferrable groups known to promote transmetallation were prepared by Grignard chemistry and enyne metathesis. These dienes participated in one pot metathesis/Diels-Alder reactions in regio- and diastereoselective fashions. Electron-rich alkenes showed the fastest rates in metathesis reactions, and ethylene, a commonly used metathesis promoter slowed enyne metathesis. 2-Pyridyldimethylsilyl and 2-thienyldimethylsilyl substituted Diels-Alder cy...

  19. Formation of gas-phase peroxides in a rural atmosphere: An interpretation of the recent SOS/SERON field results

    Energy Technology Data Exchange (ETDEWEB)

    Lee, J.H.; Tang, I.N. [Brookhaven National Lab., Upton, NY (United States); Weinstein-Lloyd, J.B. [State Univ. of New York, Old Westbury, NY (United States). Chemistry/Physics Dept.

    1993-09-01

    Hydrogen perioxide (H{sub 2}O{sub 2}) and certain organic peroxides such as hydroxymethyl-hydroperoxide (HMHP), are gas-phase oxidants present in the atmosphere at ppbv concentration levels. These oxidants play an important role in atmospheric chemistry. In addition, precipitation containing H{sub 2}O{sub 2} is toxic to trees, and it has also been suggested that organic peroxides formed presumably by ozone reactions with biogenic alkenes are responsible for leaf disorders. Recently, we have developed a nonenzymatic method or aqueous-phase H{sub 2}O{sub 2} measurement, using Fenton reagent and fluorescent hydroxy- benzoic acid. The new method, in conjunction with the well-known method of p-hydroxyphenylacetic acid and horseradish peroxidase for total peroxides, and together with an improved gas scrubber to mitigate sampling line problems, has been successfully deployed in recent SOS/SERON field measurements in rural Georgia. For the first time, continuously measured and speciated gas-phase peroxide data have become available, making it possible to examine some aspects of the ozone chemistry leading to the formation of these oxidants. It is observed that daily H{sub 2}O{sub 2} maximum frequently occurs at a different time than does HMHP, and that H{sub 2}O{sub 2} concentration, but not HMHP, tends to correlate with solar fluxes measured at the same location. These findings seem to indicate that the formation mechanisms for H{sub 2}O{sub 2} and organic peroxides are basically different. It is likely that H{sub 2}O{sub 2} is formed from radical-radical recombination, while HMHP is formed by ozone-alkene reactions. Since the gas-phase ozone-alkene reactions are usually too slow to account for the diurnal concentration variations observed for HMHP, heterogeneous processes involving ozone and alkenes are also a possibility.

  20. Evolution of sexual mimicry in the orchid subtribe orchidinae: the role of preadaptations in the attraction of male bees as pollinators

    OpenAIRE

    Cozzolino Salvatore; Schiestl Florian P

    2008-01-01

    Abstract Background Within the astonishing diversity of orchid pollination systems, sexual deception is one of the most stunning. An example is the genus Ophrys, where plants attract male bees as pollinators by mimicking female mating signals. Unsaturated hydrocarbons (alkenes) are often the key signal for this chemical mimicry. Here we investigate the evolution of these key compounds within Orchidinae by mapping their production in flowers of selected species onto their estimated phylogeny. ...

  1. Evolution of sexual mimicry in the orchid subtribe orchidinae: the role of preadaptations in the attraction of male bees as pollinators

    OpenAIRE

    Schiestl, F. P.; Cozzolino, S.

    2008-01-01

    BACKGROUND: Within the astonishing diversity of orchid pollination systems, sexual deception is one of the most stunning. An example is the genus Ophrys, where plants attract male bees as pollinators by mimicking female mating signals. Unsaturated hydrocarbons (alkenes) are often the key signal for this chemical mimicry. Here we investigate the evolution of these key compounds within Orchidinae by mapping their production in flowers of selected species onto their estimated phylogeny. RESULTS:...

  2. Cis-Selective Ring-Opening Metathesis Polymerization with Ruthenium Catalysts

    OpenAIRE

    Keitz, Benjamin K.; Alexey FEDOROV; Grubbs, Robert H.

    2012-01-01

    Cis-selective ring-opening metathesis polymerization of several monocyclic alkenes as well as norbornene and oxanorbornene-type monomers using a C–H activated, ruthenium-based metathesis catalyst is reported. The cis content of the isolated polymers depended heavily on the monomer structure and temperature. A cis content as high as 96% could be obtained by lowering the temperature of the polymerization.

  3. Selektive Oxidationsreaktionen mit molekularem Sauerstoff in komprimiertem Kohlendioxid

    OpenAIRE

    Theyssen, Nils

    2003-01-01

    The present dissertation is divided into two research projects. In the first one the possibility for a synthesis of organic carbonates starting from alkenes, oxygen, carbon dioxide and aldehydes as coreductants was investigated. The first part of the consecutive reaction sequence-the stainless steel initiated synthesis of epoxides using O2/aldehyde mixtures in supercritical carbon dioxide-was successively performed by Loeker.[1] This result bares the potential for an in situ synthesis of orga...

  4. Impact of California Reformulated Gasoline on Motor Vehicle Emissions. 2. Volatile Organic Compound Speciation and Reactivity

    OpenAIRE

    Kirchstetter, Thomas; Singer, Brett; Harley, Robert

    1999-01-01

    This paper addresses the impact of California phase 2 reformulated gasoline (RFG) on the composition and reactivity of motor vehicle exhaust and evaporative emissions. Significant changes to gasoline properties that occurred in the first half of 1996 included an increase in oxygen content; decreases in alkene, aromatic, benzene, and sulfur contents; and modified distillation properties. Vehicle emissions were measured in a San Francisco Bay Area roadway tunnel in summers 1994-1997; gasoline s...

  5. Polymer precursors from catalytic reactions of natural oils

    OpenAIRE

    Furst, Marc R. L.

    2013-01-01

    The bidentate ligand 1,2-bis(ditertbutylphosphinomethyl)benzene has been shown to be a very efficient catalyst for operating the alkoxycarbonylation of alkenes and unsaturated esters and carboxylic acids giving a very high selectivity to the linear product with very few exceptions to this general rule. Due to the increasing prices of petroleum feedstock and petroleum-derived chemicals, the preparation of chemicals starting from renewable resources and waste products from the industry be...

  6. Comparison of the catalytic activity of MOFs and zeolites in Knoevenagel condensation

    Czech Academy of Sciences Publication Activity Database

    Opanasenko, Maksym; Dhakshinamoorthy, A.; Shamzhy, Mariya; Nachtigall, P.; Horáček, Michal; Garcia, H.; Čejka, Jiří

    2013-01-01

    Roč. 3, č. 2 (2013), s. 500-507. ISSN 2044-4753 R&D Projects: GA ČR GBP106/12/G015 Grant ostatní: European Commission(XE) FP7/2007-2013, contract 228862 Institutional support: RVO:61388955 Keywords : SOLVENT-FREE CONDITIONS * METAL-ORGANIC FRAMEWORKS * ELECTROPHILIC ALKENES Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.760, year: 2013

  7. Copper-catalyzed stereoselective conjugate addition of alkylboranes to alkynoates

    Science.gov (United States)

    Wakamatsu, Takamichi; Nagao, Kazunori

    2015-01-01

    Summary A copper-catalyzed conjugate addition of alkylboron compounds (alkyl-9-BBN, prepared by hydroboration of alkenes with 9-BBN-H) to alkynoates to form β-disubstituted acrylates is reported. The addition occurred in a formal syn-hydroalkylation mode. The syn stereoselectivity was excellent regardless of the substrate structure. A variety of functional groups were compatible with the conjugate addition. PMID:26734092

  8. Evaluating Transition-Metal Catalyzed Transformations for the Synthesis of Laulimalide

    OpenAIRE

    Trost, Barry M.; Amans, Dominique; Seganish, W. Michael; Chung, Cheol K.

    2009-01-01

    Laulimalide is a structurally unique 20-membered marine macrolide displaying microtubule stabilizing activity similar to that of paclitaxel and the epothilones. The use of atom economical transformations such as a rhodium-catalyzed cycloisomerization to form the endocyclic dihydropyran, a dinuclear zinc-catalyzed asymmetric glycolate aldol to prepare the syn 1,2-diol and an intramolecular ruthenium-catalyzed alkene-alkyne coupling to build the macrocycle enabled us to synthesize laulimalide v...

  9. Manganese-Mediated Coupling Reaction of Vinylarenes and Aliphatic Alcohols

    Science.gov (United States)

    Zhang, Wei; Wang, Nai-Xing; Bai, Cui-Bing; Wang, Yan-Jing; Lan, Xing-Wang; Xing, Yalan; Li, Yi-He; Wen, Jia-Long

    2015-10-01

    Alcohols and alkenes are the most abundant and commonly used organic building blocks in the large-scale chemical synthesis. Herein, this is the first time to report a novel and operationally simple coupling reaction of vinylarenes and aliphatic alcohols catalyzed by manganese in the presence of TBHP (tert-butyl hydroperoxide). This coupling reaction provides the oxyalkylated products of vinylarenes with good regioselectivity and accomplishes with the principles of step-economies. A possible reaction mechanism has also been proposed.

  10. Factors influencing crude oil biodegradation by Yarrowia lipolytica

    OpenAIRE

    Tatiana Felix Ferreira; Maria Alice Zarur Coelho; Maria Helena Miguez da Rocha-Leão

    2012-01-01

    Yarrowia lipolytica is unique strictly aerobic yeast with the ability to efficiently degrade hydrophobic substrates such as n-alkenes, fatty acids, glycerol and oils. In the present work, a 2(4) full factorial design was used to investigate the influence of the independent variables of temperature, agitation, initial cell concentration and initial petroleum concentration on crude oil biodegradation. The results showed that all variables studied had significant effects on the biodegradation pr...

  11. A Chiral Electrophilic Selenium Catalyst for Highly Enantioselective Oxidative Cyclization.

    Science.gov (United States)

    Kawamata, Yu; Hashimoto, Takuya; Maruoka, Keiji

    2016-04-27

    Chiral electrophilic selenium catalysts have been applied to catalytic asymmetric transformations of alkenes over the past two decades. However, highly enantioselective reactions with a broad substrate scope have not yet been developed. We report the first successful example of this reaction employing a catalyst based on a rigid indanol scaffold, which can be easily synthesized from a commercially available indanone. The reaction efficiently converts β,γ-unsaturated carboxylic acids into various enantioenriched γ-butenolides under mild conditions. PMID:27064419

  12. Oxidation of Group 8 transition-Metal Hydrides and Ionic Hydrogenation of Ketones and Aldehydes

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Kjell-Tore

    1996-08-01

    Transition-metal hydrides have received considerable attention during the last decades because of their unusual reactivity and their potential as homogeneous catalysts for hydrogenation and other reactions of organic substrates. An important class of catalytic processes where transition-metal hydrides are involved is the homogeneous hydrogenation of alkenes, alkynes, ketones, aldehydes, arenes and nitro compounds. This thesis studies the oxidation of Group 8 transition-metal hydrides and the ionic hydrogenation of ketones and aldehydes.

  13. Multicomponent vinylpyrrolidone hydrogels and use thereof in tissue engineering and/or regenerative medicine

    OpenAIRE

    Gallardo Ruiz, Alberto; Aranaz, Inmaculada; Nash, María E.; Gómez Tardajos, Myriam; Elvira, Carlos; Reinecke, Helmut; Martínez-Campos, Enrique; Ramos, Viviana; López-Lacomba, José Luis

    2014-01-01

    [EN] The invention relates to a hydrogel having a cross-linked multicomponent polymer network structure, characterised in that said hydrogel includes: a) blocks derived from vinylpyrrolidone (V) and blocks derived from an anionic or anionisable alkene monomer (A), wherein the reactivity ratios in binary radical copolymerisation of (V) and (A) have maximum and minimum values of 0.5, respectively; and b) blocks derived from at least one cross-linking agent; as long as the one or more cross-link...

  14. Studies of Atmospheric Chemistry and Reaction Mechanisms Using Optical Spectroscopy and Mass Spectrometry

    OpenAIRE

    Liu, Yingdi

    2011-01-01

    This thesis mainly focuses on (1) development and applications of cavity ringdown spectroscopy (CRDS) to study atmospheric trace gases; (2) reactive intermediates in the alkene ozonolysis reactions using photoionization time-of-flight mass spectrometry (TOFMS); and (3) development of new methods using CRDS for thin film studies.Specifically, CRDS based instruments are developed to measure and characterize peroxy radicals in atmosphere. By combining the chemical amplification detection of pero...

  15. Substrate Specificity Combined with Stereopromiscuity in Glutathione Transferase A4-4-dependent Metabolism of 4-Hydroxynonenal

    OpenAIRE

    Balogh, Larissa M.; Le Trong, Isolde; Kripps, Kimberly A.; Shireman, Laura M.; Stenkamp, Ronald E.; Zhang, Wei; Mannervik, Bengt; Atkins, William M.

    2010-01-01

    Conjugation to glutathione (GSH) by glutathione transferase A4-4 (GSTA4-4) is a major route of elimination for the lipid peroxidation product 4-hydroxynonenal (HNE), a toxic compound that contributes to numerous diseases. Both enantiomers of HNE are presumed to be toxic, and GSTA4-4 has negligible stereoselectivity towards them, despite its high catalytic chemospecificity for alkenals. In contrast to the highly flexible, and substrate promiscuous, GSTA1-1 isoform that has poor catalytic effic...

  16. Evaluation of the quality of pet foods using fast techniques and official methods Avaliação da qualidade de rações utilizando métodos rápidos e métodos oficiais

    OpenAIRE

    Cibele Cristina Osawa; Lireny Aparecida Guaraldo Gonçalves; Sidnei Ragazzi

    2008-01-01

    This paper was designed to evaluate the rancidity of 18 pet food samples using the Diamed FATS kits and official AOCS methods for the quantification of free fatty acids, peroxide value and concentrations of malonaldehyde and alkenal in the lipid extracted. Although expiration dates have passed, the samples presented good quality evidencing little oxidative rancidity. The results of this study suggest that the Brazilian pet food market is replete with products of excellent quality due to the c...

  17. Energies of organic compounds. Technical progress report

    Energy Technology Data Exchange (ETDEWEB)

    Wiberg, K.B.

    1987-08-12

    A procedure was developed for carbonyl group reduction using triethylborohydride. Esters and lactones are readily reduced and are suitable as substrates. Some enthalpies of hydrolysis of lactones and esters were measured. Heats of trifluoroacetolysis of alkenes leading to tertiary alcohols were measured; some cyclic systems were also investigated. In order to study the effect of {alpha}-alkyl substituents on ketones, rotational barriers adjacent to carbonyl groups were studied.

  18. The Ritter Reaction in Liquid Sulfur Dioxide

    OpenAIRE

    Posevins, D

    2015-01-01

    Ritter reaction is associated with a one-pot process for amide bond formation, that involves nitrile and a group, capable of giving a relatively stable carbenium ion (originally - alcohol or alkene) in strongly ionizing acidic medium. The classical Ritter reaction involves use of at least stoichiometric amounts of a corrosive Brønsted acid (i.e., conc. H2SO4), thus often limiting its applicability to compounds containing acid labile functional groups. Nevertheless because of its atom economy ...

  19. Single-step DNA immobilization on antifouling self-assembled monolayers covalently bound to silicon (111).

    Science.gov (United States)

    Böcking, Till; Kilian, Kristopher A; Gaus, Katharina; Gooding, J Justin

    2006-04-11

    Hydrosilylation of alkenes with epoxide-terminated tri(ethylene oxide) moieties on Si-H surfaces yields homogeneous monolayers for the efficient coupling of biomolecules. The wetting properties of the epoxide-functionalized surface allow for the spotting of solutions of biomolecules, making the surface amenable to microarraying. Immobilization of thiolated DNA was achieved in a single step to fabricate biorecognition interfaces showing the hybridization of complementary DNA at low concentrations and negligible binding of noncomplementary DNA. PMID:16584219

  20. Formation of 1,4- and 1,5-regioisomers of triazolines in reactions of 2-ethoxyethyl azide with monosubstituted ethylenes

    International Nuclear Information System (INIS)

    The structural specificity of the reactions of 2-ethoxyethyl azide with alkenes RCH=CH2 [R = CH2C6H5, CH2OC6H13, CH(OC2H5)2, C6H5] was studied. The formation of 1,4- and 1,5-substituted triazolines and the high stabilities of the latter were demonstrated by PMR spectroscopy, data from gas-liquid chromatography (GLC), and the kinetics of thermolysis

  1. Reproductive competition in the bumble-bee Bombus terrestris: do workers advertise sterility?

    OpenAIRE

    Amsalem, Etya; Twele, Robert; Francke, Wittko; Hefetz, Abraham

    2009-01-01

    Reproductive competition in social insects is generally mediated through specific fertility pheromones. By analysing Dufour's gland secretion in queens and workers of Bombus terrestris under varying social conditions, we demonstrate here that the volatile constituents of the secretion exhibit a context-dependent composition. The secretion of egg-laying queens is composed of a series of aliphatic hydrocarbons (alkanes and alkenes), while that of sterile workers contains in addition octyl ester...

  2. Well-defined single-site monohydride silica-supported zirconium from azazirconacyclopropane

    KAUST Repository

    Hamzaoui, Bilel

    2015-01-13

    The silica-supported azazirconacyclopropane ≡SiOZr(HNMe2)(η2-NMeCH2)(NMe2) (1) leads exclusively under hydrogenolysis conditions (H2, 150°C) to the single-site monopodal monohydride silica-supported zirconium species ≡SiOZr(HNMe2)(NMe2)2H (2). Reactivity studies by contacting compound 2 with ethylene, hydrogen/ethylene, propene, or hydrogen/propene, at a temperature of 200°C revealed alkene hydrogenation.

  3. Nickel-Catalyzed Intramolecular [3 + 2 + 2] Cycloadditions of Alkylidenecyclopropanes. A Straightforward Entry to Fused 6,7,5-Tricyclic Systems

    OpenAIRE

    Saya Codesal, Lucía; Fernández, Israel; López, Fernando; Mascareñas Cid, José Luis

    2014-01-01

    A highly diastereo- and chemoselective intramolecular nickel-catalyzed cycloaddition of alkene- and alkyne-tethered alkynylidenecyclopropanes is reported. The method constitutes the first fully intramolecular [3 + 2 + 2] alkylidenecyclopropropane cycloaddition occurring via a proximal cleavage of the cyclopropane and makes it possible to build relevant 6,7,5-tricyclic frameworks in a single-pot reaction. Importantly, the reaction outcome is highly dependent on the characteristics of the nicke...

  4. Catalyst-Controlled Regioselectivity in the Synthesis of Branched Conjugated Dienes via Aerobic Oxidative Heck Reactions

    OpenAIRE

    Zheng, Changwu; Wang, Dian; Stahl, Shannon S.

    2012-01-01

    Pd-catalyzed aerobic oxidative coupling of vinylboronic acids and electronically unbiased alkyl olefins provides regioselective access to 1,3-disubstituted conjugated dienes. Catalyst-controlled regioselectivity is achieved by using 2,9-dimethylphenanthroline as a ligand. The observed regioselectivity is opposite to that observed from a traditional (non-oxidative) Heck reaction between a vinyl bromide and an alkene. DFT computational studies reveal that steric effects of the 2,9-dimethylphena...

  5. Phosphine Catalysis using Allenoates with pro-Nucleophiles or Arylidenes; Development of an Asymetric Phosphine Catalyst; and Allenes as π-Ligands in Copper-Mediated Cross-Coupling

    OpenAIRE

    Martin, Tioga Jarrett

    2014-01-01

    The unique characteristics of 1,2-dienes have proven to be a dynamic and ever growing field of study in organic chemistry. Allenes have been manipulated into a myriad of transformations, and have offered their unique characteristics to a number of fields of study. Chapter 1 discusses a phosphine catalyzed annulation between allenoates and alkenes to form cyclohexenes. In Chapter 2 the new phosphine catalyzed β'-Addition of a Pronucleophile to an allenoate is examined. Chapter 3 presents ...

  6. Click-In Ferroelectric Nanoparticles for Dielectric Energy Storage.

    Science.gov (United States)

    Riggs, Brian C; Elupula, Ravinder; Rehm, Caroline; Adireddy, Shiva; Grayson, Scott M; Chrisey, Douglas B

    2015-08-19

    Polymer-ceramic nanocomposites have been thoroughly investigated previously for high energy storage devices. However, the increase in performance of these nanocomposites has proven to be significantly lower than predicted values. Through surface functionalization of high dielectric constant nanoparticles (NP), the flaws that reduce composite performance can be eliminated to form high energy density composite materials. Functionalization methods utilize high throughput printing and curing techniques (i.e., inkjet printing and xenon flash lamp curing) that are crucial for rapid adoption into industrial production. (Ba,Ca) (Zr,Ti)O3 NPs (50 nm) are synthesized through the solvothermal method and functionalized with alkene terminated methoxysilanes. A thiol-ene monomer ink system, PTD3 [pentaerythritol tetrakis (3-mercaptopropionate) (PEMP, P), 1,3-Diisopropenylbenzene (DPB, D), 2,4,6-Triallyloxy-1,3,5-triazine (TOTZ, T)], is used as a high breakdown polymer matrix. Neat polymer, alkene terminated NP-polymer composites, and hydrophilic, TBAOH functionalized NP-polymer composites were spin coated onto both copper laminated glass slides and printed onto copper substrates in 1 cm(2) patterns for testing. Alkene functionalized NPs increased the breakdown strength by ∼38% compared to the nonfunctionalized NPs. Functionalized NPs increased both the breakdown strength and dielectric constant compared to the neat polymer, increasing the energy density nearly 3-fold from 13.3 to 36.1 J·cm(-3). PMID:26214655

  7. Improved method for estimating molecular weights of volatile organic compounds from low-resolution mass spectra

    Energy Technology Data Exchange (ETDEWEB)

    Scott, D.R.

    1991-01-01

    An improved method of estimating molecular weights of volatile organic compounds from their mass spectra has been developed and implemented with an expert system. The method is based on the strong correlation of MAXMASS, the highest mass with an intensity of 5% of the base peak in a mass spectrum, with the true molecular weight. Linear corrections to MAXMASS, which yield molecular weight estimates, were derived empirically using the expert system. The system is based on a sequential modular design with a primary classifier linked to molecular weight estimators for the resulting six classes. These are non-halobenzenes; chlorobenzenes; bromoalkenes/alkenes; mono- and dichloroalkanes/alkenes; tri-, tetra- and pentachloro-alkanes/alkenes; and others. Performance tests were made with the old and improved expert systems and the Self Training Interpretive and Retrieval System (STIRS) on NIST reference spectra of the 107 training compounds; on a set of 32 test NIST reference spectra of other compounds found in air samples; on a set of 100 randomly selected NIST reference spectra; and on 27 spectra taken from actual field gas chromatography/mass spectrometry samples.

  8. Expert system for estimates of molecular weights of volatile organic compounds from low-resolution mass spectra

    Energy Technology Data Exchange (ETDEWEB)

    Scott, D.R.

    1991-01-01

    MAXMASS, the highest mass with an intensity of 5% of the base peak in a low resolution mass spectrum, has been found to be linearly correlated with the true molecular weights of 400 randomly selected spectra, yielding a family of parellel lines. A simple expert system using MAXMASS has been developed to estimate molecular weights of unknown volatile compounds from their mass spectra. This is an empirical rule-based system which will run on a personal computer. It consists of a classification module chained to separate molecular weight prediction modules for six classes. These are benzenes; chlorobenzenes; bromoalkenes/alkenes; mono- and dichloroalkanes/alkenes; tri-, tetra- and pentachloroalkanes/alkenes; and unknown (other) classes. The rules were derived from National Institute of Standards and Technology (NIST) reference spectra of 75 target toxic compounds from the first five classes and 32 from the unknown class. Performance tests of molecular weight predictions were made with the expert system and the Self Training interpretive and Retrieval System (STIRS) on NIST reference spectra of the 107 training compounds; on a set of 32 test NIST reference spectra of other compounds found in air samples; on a set of 100 randomly selected NIST reference spectra; and on 30 spectra taken from actual field gas chromatography/mass spectrometry samples.

  9. Ozone Oxidation of Self-Assembled Monolayers on SiOx-Coated Zinc Selenide Surfaces

    Science.gov (United States)

    McIntire, T. M.; Ryder, O. S.; Finlayson-Pitts, B. J.

    2008-12-01

    Airborne particles are important for visibility, human health, climate, and atmospheric reactions. Atmospheric particles contain a significant fraction of organics and such compounds present on airborne particles are susceptible to oxidation by atmospheric oxidants, such as OH, ozone, halogen atoms, and nitrogen trioxide. Oxidized organics associated with airborne particles are thought to be polar, hygroscopic species with enhanced cloud-nucleating properties. Oxide layers on silicon, or SiO2-coated substrates, act as models of environmentally relevant surfaces such as dust particles upon which organics adsorb. We have shown previously that ozone oxidation of unsaturated self-assembled monolayers (SAMs) on silicon attenuated total reflectance (ATR) crystals leads to the formation of carbonyl groups and micron-sized, hydrophobic organic aggregates surrounded by carbon depleted substrate that do not have increased water uptake as previously assumed. Reported here are further ATR-FTIR studies of the oxidation of alkene SAMs on ZnSe and SiO2-coated ZnSe. These substrates have the advantage that they transmit below 1500 cm-1, allowing detection of additional product species. These experiments show that the loss of C=C and formation of carbonyl groups is also accompanied by formation of a peak at 1110 cm-1, attributed to the secondary ozonide. Details concerning the products and mechanism of ozonolysis of alkene SAMs on surfaces based on these new data are presented and the implications for the oxidation of alkenes on airborne dust particles are discussed.

  10. Manganese porphyrin immobilized on magnetite nanoparticles as a recoverable nanocatalyst for epoxidation of olefins

    Energy Technology Data Exchange (ETDEWEB)

    Saeedi, Mohammad Saleh; Tangestaninejad, Shahram, E-mail: stanges@sci.ui.ac.ir; Moghadam, Majid, E-mail: moghadamm@sci.ui.ac.ir; Mirkhani, Valiollah; Mohammadpoor-Baltork, Iraj; Khosropour, Ahmad Reza

    2014-07-01

    Efficient epoxidation of alkenes catalysed by tetraphenylporphyrinatomanganese(III) chloride, [Mn(TPP)Cl], supported on silica coated magnetite nanoparticles, SiO{sub 2}–Fe{sub 3}O{sub 4}, is reported. First, the SiO{sub 2}–Fe{sub 3}O{sub 4} nanoparticles were modified with triethoxysilylpropyl chloride and then with imidazole. In the final step, [Mn(TPP)Cl] was attached to the support via axial ligation. The prepared catalyst was characterized by elemental analysis, FT-IR and diffuses reflectance UV–vis spectroscopic methods, and scanning electron microscopy. This new heterogenized catalyst was used for efficient epoxidation of alkenes with NaIO{sub 4} at room temperature. The catalyst is of high reusability in the epoxidation reactions, in which it was reused several times without significant loss of its catalytic activity. - Highlights: • The [Mn(TPP)Cl] was supported on silica coated magnetic nanoparticles. • The [Mn(TPP)Cl@Im–SiO{sub 2}–Fe{sub 3}O{sub 4}] heterogeneous catalyst was characterized. • The [Mn(TPP)Cl@Im–SiO{sub 2}–Fe{sub 3}O{sub 4}]/NaIO{sub 4} catalytic system was used for alkene epoxidation. • The catalyst was efficient and reusable.

  11. Identification and biotransformation of aliphatic hydrocarbons during co-composting of sewage sludge-Date Palm waste using Pyrolysis-GC/MS technique.

    Science.gov (United States)

    El Fels, Loubna; Lemee, Laurent; Ambles, André; Hafidi, Mohamed

    2016-08-01

    The behavior of aliphatic hydrocarbons during co-composting of sewage sludge activated with palm tree waste was studied for 6 months using Py-GC/MS. The main aliphatic compounds represented as doublet alkenes/alkanes can be classified into three groups. The first group consists of 11 alkenes (undecene, tridecene, pentadecene, hexadecene, heptadecene, octadecene, nonadecene, eicosene, uncosene, docosene, tricosene) and 15 alkanes (heptane, octane, nonane, decane, undecane, dodecane, tetradecane, pentadecane, heptadecane, octadecane, nonadecane, eicosane, uncosane, docosane, and tricosane), which remain stable during the co-composting process. The stability of these compounds is related to their recalcitrance behavior. The second group consists of five alkenes (heptene, octene, nonene, decene, dodecene) and tridecane as a single alkane that decreases during co-composting. The decrease in these compounds is the combined result of their metabolism and their conversion into other compounds. The third group is constituted with tetradecene and hexadecane that increase during composting, which could be explained by accumulation of these compounds, which are released by the partial breakdown of the substrate. As a result, these molecules are incorporated or adsorbed in the structure of humic substances. PMID:27197656

  12. Thermally induced alkylation of diamond.

    Science.gov (United States)

    Hoeb, Marco; Auernhammer, Marianne; Schoell, Sebastian J; Brandt, Martin S; Garrido, Jose A; Stutzmann, Martin; Sharp, Ian D

    2010-12-21

    We present an approach for the thermally activated formation of alkene-derived self-assembled monolayers on oxygen-terminated single and polycrystalline diamond surfaces. Chemical modification of the oxygen and hydrogen plasma-treated samples was achieved by heating in 1-octadecene. The resulting layers were characterized using X-ray photoelectron spectroscopy, thermal desorption spectroscopy, atomic force microscopy, Fourier transform infrared spectroscopy, and water contact angle measurements. This investigation reveals that alkenes selectively attach to the oxygen-terminated sites via covalent C-O-C bonds. The hydrophilic oxygen-terminated diamond is rendered strongly hydrophobic following this reaction. The nature of the process limits the organic layer growth to a single monolayer, and FTIR measurements reveal that such monolayers are dense and well ordered. In contrast, hydrogen-terminated diamond sites remain unaffected by this process. This method is thus complementary to the UV-initiated reaction of alkenes with diamond, which exhibits the opposite reactivity contrast. Thermal alkylation increases the range of available diamond functionalization strategies and provides a means of straightforwardly forming single organic layers in order to engineer the surface properties of diamond. PMID:21090790

  13. Co-feeding with DME:An effective way to enhance gasoline production via low temperature aromatization of LPG

    Institute of Scientific and Technical Information of China (English)

    Xiangxue; Zhu; Yuzhong; Wang; Xiujie; Li; Hongbing; Li; Peng; Zeng; Jie; An; Fucun; Chen; Sujuan; Xie; Hongping; Lan; Dawei; Wang; Shenglin; Liu; Longya; Xu

    2013-01-01

    The aromatization of light alkenes in liquefied petroleum gas (LPG) with and without dimethyl ether (DME) addition in the feed was investigated on a modified ZSM-5 catalyst.The results showed that under the given reaction conditions the selectivity of alkenes to high-octane gasoline blending components was markedly enhanced and the formation of propane and butanes was greatly suppressed with the addition of DME.It was also found that the distribution of C5+ components was changed a lot with DME addition into the LPG feed.The formation of branched hydrocarbons (mainly C6 C8 i-paraffin) and multi-methyl substituted aromatics,which are high octane number gasoline blending components,was promoted significantly,while the content of n-paraffins and olefins in C5+ components was decreased obviously,indicating that in addition to the oligomerization,cracking,hydrogen-transfer and dehydrogenation-cyclization of alkenes,the methylation of the formed aromatics and olefins intermediates also plays an important role in determining the product distribution due to the high reactivity of surface methoxy groups formed by DME.And this process,in combination with the syngas-to-methanol/DME technology,provides an alternative way to the production of high-octane gasoline from coal,natural gas or renewable raw materials.

  14. Fundamental aspects of nucleation and growth in the solution-phase synthesis of germanium nanocrystals

    KAUST Repository

    Codoluto, Stephen C.

    2010-01-01

    Colloidal Ge nanocrystals (NCs) were synthesized via the solution phase reduction of germanium(ii) iodide. We report a systematic investigation of the nanocrystal nucleation and growth as a function of synthesis conditions including the nature of coordinating solvents, surface bound ligands, synthesis duration and temperature. NC synthesis in reaction environments with weakly bound phosphine surface ligand led to the coalescence of nascent particles leading to ensembles with broad lognormal particle diameter distributions. Synthesis in the presence of amine or alkene ligands mitigated particle coalescence. High-resolution transmission electron micrographs revealed that NCs grown in the presence of weak ligands had a high crystal defect density whereas NCs grown in amine solutions were predominantly defect-free. We applied infrared spectroscopy to study the NC surface chemistry and showed that alkene ligands project the NCs from surface oxidation. Photoluminescence spectroscopy measurements showed that alkene ligands passivate surface traps, as indicated by infrared fluorescence, conversely oxidized phosphine and amine passivated NCs did not fluoresce. © 2010 The Royal Society of Chemistry.

  15. Carboxylic Acid Photochemistry is a Marine Source of Glyoxal and Other Aldehydes

    Science.gov (United States)

    Chiu, R.; Gonzalez, L.; Tinel, L.; George, C.; Volkamer, R. M.

    2015-12-01

    Glyoxal is a highly water-soluble precursor in secondary organic aerosol (SOA) formation. Over land, glyoxal is known to be produced by the oxidation of volatile organic carbon (VOC) from both anthropogenic and natural sources. However, marine sources are still not well understood. Previous studies above the remote Pacific Ocean have detected typical glyoxal mixing ratios of 30-40 pptv, concentrations too high to be explained with current chemical understanding or atmospheric models. Because the lifetime of glyoxal is very short, the glyoxal found must have originated from, rather than been transported to, the open ocean. Furthermore, eddy covariance measurements indicate that an organic surface microlayer may be producing the glyoxal by as yet unknown processes. Here we present laboratory studies of the formation of glyoxal from carboxylic acids. Nonanoic, octanoic, and heptanoic acids floated on water and subjected to ultraviolet light are converted into their equivalent alkenals. Subsequent ozonolysis of the alkenals leads to the formation of glyoxal. We employ a PTR-MS to detect the alkenals, and a cavity-enhanced DOAS to detect the glyoxal. Considering the ubiquitous occurrence of carboxylic acids and their derivatives in the environment, this mechanism has the potential to be a significant source of glyoxal in the atmosphere.

  16. Synthesis of fatty trichloromethyl-{beta}-diketones and new 1H-Pyrazoles as unusual FAMEs and FAEEs

    Energy Technology Data Exchange (ETDEWEB)

    Flores, Alex F.C.; Souto, Alynne A.; Malavolta, Juliana L.; Flores, Darlene C., E-mail: alex.fcf@ufsm.br [Universidade Federal de Santa Maria (UFSM), RS (Brazil). Departamento de Quimica; Blanco, Rogerio F. [Uniao de Ensino do Sudoeste do Parana (UNISEP), Dois Vizinhos, PR (Brazil). Faculdade de Farmacia

    2013-12-01

    The efficient synthesis of new fatty 1,1,1-trichloro-4-methoxy-3-alken-2-ones [Cl{sub 3}CC(O)C(R{sup 2})=C(R{sup 1})OMe, where R{sup 1} = n-hexyl, heptyl, nonyl, undecyl, tridecyl and R{sup 2} = H] and 1,1,1-trichloro-2,4-alkanediones [Cl{sub 3}CC(O)CHR{sup 2}C(O)R{sup 1}, where R{sup 1} = n-pentyl and R{sup 2} = Me, R{sup 1} = Et and R{sup 2} = n-butyl, R{sup 1} = n-butyl and R{sup 2} = n-propyl] in good yields (85-95%) from acetal acylation with trichloroacetyl chloride is reported. The fatty 1,1,1-trichloro-4-methoxy-3-alken-2-ones and 1,1,1-trichloro-2,4-alkanediones were reacted with hydrazine hydrochloride, leading to respective {sup 1}H-pyrazole-5-carboxylates, unusual class of fatty acid methyl (FAMEs) and ethyl (FAEEs) esters. Their structures were confirmed by elemental analysis and {sup 1}H and {sup 13}C nuclear magnetic resonance (NMR). The fatty 1,1,1-trichloro-4-methoxy-3-alken-2-ones and {sup 1}H-pyrazole derivatives are new oleochemicals with potentially interesting and differential properties. (author)

  17. A water-soluble ruthenium glycosylated porphyrin catalyst for carbenoid transfer reactions in aqueous media with applications in bioconjugation reactions.

    Science.gov (United States)

    Ho, Chi-Ming; Zhang, Jun-Long; Zhou, Cong-Ying; Chan, On-Yee; Yan, Jessie Jing; Zhang, Fu-Yi; Huang, Jie-Sheng; Che, Chi-Ming

    2010-02-17

    Water-soluble [Ru(II)(4-Glc-TPP)(CO)] (1, 4-Glc-TPP = meso-tetrakis(4-(beta-D-glucosyl)phenyl)porphyrinato dianion) is an active catalyst for the following carbenoid transfer reactions in aqueous media with good selectivities and up to 100% conversions: intermolecular cyclopropanation of styrenes (up to 76% yield), intramolecular cyclopropanation of an allylic diazoacetate (68% yield), intramolecular ammonium/sulfonium ylide formation/[2,3]-sigmatroptic rearrangement reactions (up to 91% yield), and intermolecular carbenoid insertion into N-H bonds of primary arylamines (up to 83% yield). This ruthenium glycosylated porphyrin complex can selectively catalyze alkylation of the N-terminus of peptides (8 examples) and mediate N-terminal modification of proteins (four examples) using a fluorescent-tethered diazo compound (15). A fluorescent group was conjugated to ubiquitin via 1-catalyzed alkene cyclopropanation with 15 in aqueous solution in two steps: (1) incorporation of an alkenic group by the reaction of N-hydroxysuccinimide ester 19 with ubiquitin and (2) cyclopropanation of the alkene-tethered Lys(6) ubiquitin (23) with the fluorescent-labeled diazoacetate 15 in the presence of a catalytic amount of 1. The corresponding cyclopropanation product (24) was obtained with approximately 55% conversion based on MALDI-TOF mass spectrometry. The products 23, 24, and the N-terminal modified peptides and proteins were characterized by LC-MS/MS and/or SDS-PAGE analyses. PMID:20088517

  18. Geographical matching of volatile signals and pollinator olfactory responses in a cycad brood-site mutualism.

    Science.gov (United States)

    Suinyuy, Terence N; Donaldson, John S; Johnson, Steven D

    2015-10-01

    Brood-site mutualisms represent extreme levels of reciprocal specialization between plants and insect pollinators, raising questions about whether these mutualisms are mediated by volatile signals and whether these signals and insect responses to them covary geographically in a manner expected from coevolution. Cycads are an ancient plant lineage in which almost all extant species are pollinated through brood-site mutualisms with insects. We investigated whether volatile emissions and insect olfactory responses are matched across the distribution range of the African cycad Encephalartos villosus. This cycad species is pollinated by the same beetle species across its distribution, but cone volatile emissions are dominated by alkenes in northern populations, and by monoterpenes and a pyrazine compound in southern populations. In reciprocal choice experiments, insects chose the scent of cones from the local region over that of cones from the other region. Antennae of beetles from northern populations responded mainly to alkenes, while those of beetles from southern populations responded mainly to pyrazine. In bioassay experiments, beetles were most strongly attracted to alkenes in northern populations and to the pyrazine compound in southern populations. Geographical matching of cone volatiles and pollinator olfactory preference is consistent with coevolution in this specialized mutualism. PMID:26446814

  19. Insights into aerosol formation chemistry from comprehensive gas-phase precursor measurement in the TRAPOZ chamber experiments; an overview

    Science.gov (United States)

    Carr, Timo; Wyche, Kevin; Monks, Paul S.; Camredon, Marie; Alam, Mohammed S.; Bloss, William J.; Rickard, Andrew R.

    2010-05-01

    Aerosols have a profound affect on the environment on local, regional and even global levels, with impacts including adverse health effects, (Alfarra, Paulsen et al. 2006) visibility reduction, cloud formation, direct radiative forcing (Charlson, Schwartz et al. 1992) and an important role in influencing the climate due to their contribution to important atmospheric processes (Baltensperger, Kalberer et al. 2005; Alfarra, Paulsen et al. 2006). The Total Radical Production from the OZonolysis of alkenes (TRAPOZ) project was used to study the gas phase and radical chemistry along with secondary organic aerosol (SOA) formation for a number of different alkenes and terpenes. In order to better the scientific knowledge regarding the oxidation mechanisms of terpene and alkene species along with radical and SOA formation, the experiments were conducted under varying conditions controlled and monitored by the EUropean PHOto REactor (EUPHORE) simulation chamber in Valencia, Spain. A vast number of instruments enabled a detailed examination of the chemistry within oxidation of each precursor. However the work here will focus on the results obtained from the University of Leicester Chemical Ionisation Reaction Time-of-Flight Mass Spectrometer (CIR-TOF-MS). With regard to the gas phase chemistry an analysis of the degradation of the precursor Volatile Organic Compounds (VOCs) and evolution of certain gas phase species in each experiment has been presented and discussed.

  20. Effect of catalyst structure on oxidative dehydrogenation of ethane and propane on alumina-supported vanadia

    Energy Technology Data Exchange (ETDEWEB)

    Argyle, Morris D.; Chen, Kaidong; Bell, Alexis T.; Iglesia, Enrique

    2001-09-11

    The catalytic properties of Al2O3-supported vanadia with a wide range of VOx surface density (1.4-34.2 V/nm2) and structure were examined for the oxidative dehydrogenation of ethane and propane. UV-visible and Raman spectra showed that vanadia is dispersed predominantly as isolated monovanadate species below {approx}2.3 V/nm2. As surface densities increase, two-dimensional polyvanadates appear (2.3-7.0 V/nm2) along with increasing amounts of V2O5 crystallites at surface densities above 7.0 V/nm2. The rate constant for oxidative dehydrogenation (k1) and its ratio with alkane and alkene combustion (k2/k1 and k3/k1, respectively) were compared for both alkane reactants as a function of vanadia surface density. Propene formation rates (per V-atom) are {approx}8 times higher than ethene formation rates at a given reaction temperature, but the apparent ODH activation energies (E1) are similar for the two reactants and relatively insensitive to vanadia surface density. Ethene and propene formation rates (per V-atom) are strongly influenced by vanadia surface density and reach a maximum value at intermediate surface densities ({approx}8 V/nm2). The ratio of k2/k1 depends weakly on reaction temperature, indicating that activation energies for alkane combustion and ODH reactions are similar. The ratio of k2/k1 is independent of surface density for ethane, but increase slightly with vanadia surface density for propane, suggesting that isolated structures prevalent at low surface densities are slightly more selective for alkane dehydrogenation reactions. The ratio of k3/k1 decreases markedly with increasing reaction temperature for both ethane and propane ODH. Thus, the apparent activation energy for alkene combustion (E3) is much lower than that for alkane dehydrogenation (E1) and the difference between these two activation energies decreases with increasing surface density. The lower alkene selectivities observed at high vanadia surface densities are attributed to an

  1. Reduced cobalt phases of ZrO2 and Ru/ZrO2 promoted cobalt catalysts and product distributions from Fischer–Tropsch synthesis

    International Nuclear Information System (INIS)

    Highlights: • Ru/ZrO2, ZrO2 promoted Co/SiO2 for FTS were reduced by time resolved XANES. • Reduced catalysts resulted from XANES reduction showed the mixed phases of Co, CoO. • The highest percentages of CoO resulted from the high ZrO2 promoted Co/SiO2. • Product distributions of 1-alkenes, iso-alkanes indicated sites for FTS and the 2° reaction. • Alkene readsorption were high corresponding to the high CoO forming branched alkanes. - Abstract: Co/SiO2 catalysts were promoted with 4% and 8% ZrO2. Small amounts (0.07%) of Ru were impregnated onto 4%ZrO2/Co/SiO2. Catalysts resulting from time-resolved XANES reduction showed mixed phases of Co and CoO, with the highest percentages of Co resulting from Ru/4%ZrO2/Co/SiO2 and the highest percentages of CoO resulting from 8%ZrO2/Co/SiO2. Product distributions of n-alkanes, iso-alkanes and alkenes during Fischer–Tropsch Synthesis (FTS) were used to investigate the catalyst performance of 4%ZrO2/Co/SiO2 8%ZrO2/Co/SiO2 and Ru/4%ZrO2/Co/SiO2. FTS steady state was studied by growth probabilities of n-alkane products. No 1-alkene was produced from Ru/4%ZrO2/Co/SiO2, indicating high availability of Fischer–Tropsch sites for long chain hydrocarbon growth, despite high methanation. Branched alkanes produced from the secondary reaction were related to the high CoO percentages on 8%ZrO2/Co/SiO2. Alkene readsorption sites were high, corresponding to the high CoO percentages, causing a high probability of forming branched alkane products

  2. Reduced cobalt phases of ZrO{sub 2} and Ru/ZrO{sub 2} promoted cobalt catalysts and product distributions from Fischer–Tropsch synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Kangvansura, Praewpilin [Department of Materials Science, Faculty of Science, Kasetsart University, Bangkok 10900 (Thailand); Schulz, Hans, E-mail: hans.schulz@kit.edu [Karlsruhe Institute of Technology, Engler-Bunte Institute, 76131 Karlsruhe (Germany); Suramitr, Anwaraporn, E-mail: sfsciawn@src.ku.ac.th [Faculty of Science at Si Racha, Kasetsart University Si Racha Campus, Chonburi 20230 (Thailand); Poo-arporn, Yingyot, E-mail: yingyot@slri.or.th [Synchrotron Light Research Institute (Public Organization), Nakhon Ratchasima 30000 (Thailand); Viravathana, Pinsuda, E-mail: fscipvd@ku.ac.th [Department of Chemistry, Faculty of Science, Kasetsart University, Bangkok 10900 (Thailand); Worayingyong, Attera, E-mail: fscippl@ku.ac.th [Department of Materials Science, Faculty of Science, Kasetsart University, Bangkok 10900 (Thailand)

    2014-12-15

    Highlights: • Ru/ZrO{sub 2}, ZrO{sub 2} promoted Co/SiO{sub 2} for FTS were reduced by time resolved XANES. • Reduced catalysts resulted from XANES reduction showed the mixed phases of Co, CoO. • The highest percentages of CoO resulted from the high ZrO{sub 2} promoted Co/SiO{sub 2}. • Product distributions of 1-alkenes, iso-alkanes indicated sites for FTS and the 2° reaction. • Alkene readsorption were high corresponding to the high CoO forming branched alkanes. - Abstract: Co/SiO{sub 2} catalysts were promoted with 4% and 8% ZrO{sub 2}. Small amounts (0.07%) of Ru were impregnated onto 4%ZrO{sub 2}/Co/SiO{sub 2}. Catalysts resulting from time-resolved XANES reduction showed mixed phases of Co and CoO, with the highest percentages of Co resulting from Ru/4%ZrO{sub 2}/Co/SiO{sub 2} and the highest percentages of CoO resulting from 8%ZrO{sub 2}/Co/SiO{sub 2}. Product distributions of n-alkanes, iso-alkanes and alkenes during Fischer–Tropsch Synthesis (FTS) were used to investigate the catalyst performance of 4%ZrO{sub 2}/Co/SiO{sub 2} 8%ZrO{sub 2}/Co/SiO{sub 2} and Ru/4%ZrO{sub 2}/Co/SiO{sub 2}. FTS steady state was studied by growth probabilities of n-alkane products. No 1-alkene was produced from Ru/4%ZrO{sub 2}/Co/SiO{sub 2}, indicating high availability of Fischer–Tropsch sites for long chain hydrocarbon growth, despite high methanation. Branched alkanes produced from the secondary reaction were related to the high CoO percentages on 8%ZrO{sub 2}/Co/SiO{sub 2}. Alkene readsorption sites were high, corresponding to the high CoO percentages, causing a high probability of forming branched alkane products.

  3. Functionalization of group IV semiconductors; Funktionalisierung von Gruppe IV-Halbleitern

    Energy Technology Data Exchange (ETDEWEB)

    Hoeb, Marco Andreas

    2011-01-15

    The present work is focused on the structural and electronic properties of thermally and photochemically grafted alkene molecules. The semiconductor substrates used in this work are the group IV-semiconductors silicon, diamond, and silicon carbide. On silicon, functionalization via the commonly known hydrosilylation reaction was performed. During thermal treatment in vacuum-distilled 1-octadecene, the alkene molecules covalently added to the substrate via Si-C bond formation, resulting in self-assembled organic monolayers. The reaction resulted in smooth and homogeneous alkyl-terminated surfaces. Static water contact angles were determined to be 113 . Photoelectron spectroscopy was performed and showed no evidence of surface oxidation. The high packing of the organic layers is indicated by the asymmetric methylene vibrational mode, which has been redshifted by -4 cm{sup -1} with respect to the liquid alkene mode position. The average molecular tilt-angle of the alkyl-molecules, relative to the surface normal, has been identified to be 34 . The transport properties have been determined to be dominated by tunneling processes. On diamond, first results on the thermal functionalization of hydrogen- and oxygen-terminated surfaces are demonstrated. Thermal functionalization with octadecene showed high selectivity, while hydrogenated diamond surfaces were found to be inert to the thermally induced reaction with alkenes. In contrast, alkene molecules were successfully grafted to oxygen-terminated sites via covalent C-O-C bonds. Reaction temperatures as high as 160 C were necessary to initiate the functionalization process.Wetting experiments on the alkyl-modified surfaces revealed contact angle values of 103 . The high quality of the monolayers on oxygenated surfaces was confirmed by IR-spectroscopy. In addition, polarized IR-measurements indicated a tilt angle of 23 . On silicon carbide, thermal and UV-induced alkoxylation were studied. Hydrofluoric acid treatment

  4. Tempo-spatial variation of emission inventories of speciated volatile organic compounds from on-road vehicles in China

    Directory of Open Access Journals (Sweden)

    H. Cai

    2009-05-01

    Full Text Available Emission inventories of sixty-nine speciated non-methane volatile organic compounds (NMVOC from on-road vehicles in China were estimated for the period of 1980–2005, using seven NMVOC emission profiles, which were summarized based on local and international measurements from published literatures dealing with specific vehicle categories running under particular modes.

    Results show an exponential growth trend of China's historical emissions of alkanes, alkenes, alkines, aromatics and carbonyls during the period of 1980–2005, increasing from 63.9, 39.3, 6.9, 36.8 and 24.1 thousand tons, respectively, in 1980 to 2781.4, 1244.9, 178.5, 1350.7 and 403.3 thousand tons, respectively, in 2005, which coincided well with China's economic growth. Emission inventories of alkenes, aromatics and carbonyls were gridded at a high resolution of 40 km×40 km for air quality simulation and health risk evaluation, using the geographic information system (GIS methodology. Spatial distribution of speciated NMVOC emissions shows a clear difference in emission densities between developed eastern and relatively underdeveloped western and inland China. Besides, the appearance and expansion of high-emission areas was another notable characteristic of spatial distribution of speciated NMVOC emissions during the period.

    Emission contributions of vehicle categories to speciated NMVOC groups showed annual variation, due to the variance in the provincial emissions and in the relative fractions of the seven emission profiles adopted at the provincial level. Highly reactive and toxic compounds accounted for high proportions of emissions of speciated NMVOC groups. The most abundant compounds were isopentane, pentane and butane from alkanes; ethene, propene, 2-methyl-2-butene and ethyne from alkenes and alkines; benzene, toluene, ethylbenzene, o-xylene, and m,p-xylene (BTEX and 1,2,4-trimethylbenzene from aromatics and formaldehyde, acetaldehyde

  5. Tempo-spatial variation of emission inventories of speciated volatile organic compounds from on-road vehicles in China

    Directory of Open Access Journals (Sweden)

    H. Cai

    2009-09-01

    Full Text Available Emission inventories of sixty-seven speciated non-methane volatile organic compounds (NMVOC from on-road vehicles in China were estimated for the period of 1980–2005, using seven NMVOC emission profiles, which were summarized based on local and international measurements from published literatures dealing with specific vehicle categories running under particular modes.

    Results show an exponential growth trend of China's historical emissions of alkanes, alkenes, alkines, aromatics and carbonyls during the period of 1980–2005, increasing from 63.9, 39.3, 6.9, 36.8 and 24.1 thousand tons, respectively, in 1980 to 2778.2, 1244.5, 178.7, 1351.7 and 406.0 thousand tons, respectively, in 2005, which coincided well with China's economic growth. Emission inventories of alkenes, aromatics and carbonyls were gridded at a high resolution of 40 km×40 km for air quality simulation and health risk evaluation, using the geographic information system (GIS methodology. Spatial distribution of speciated NMVOC emissions shows a clear difference in emission densities between developed eastern and relatively underdeveloped western and inland China. Besides, the appearance and expansion of high-emission areas was another notable characteristic of spatial distribution of speciated NMVOC emissions during the period.

    Emission contributions of vehicle categories to speciated NMVOC groups showed annual variation, due to the variance in the provincial emissions and in the relative fractions of the seven emission profiles adopted at the provincial level. Highly reactive and toxic compounds accounted for high proportions of emissions of speciated NMVOC groups. The most abundant compounds were isopentane, pentane and butane from alkanes; ethene, propene, 2-methyl-2-butene and ethyne from alkenes and alkines; benzene, toluene, ethylbenzene, o-xylene, and m,p-xylene (BTEX and 1,2,4-trimethylbenzene from aromatics and formaldehyde, acetaldehyde

  6. Pyrolytic conversion of lipid feeds for bio-chemical and bio-fuel production

    Energy Technology Data Exchange (ETDEWEB)

    Maher, K.D.; Kirkwood, K.M.; Bressler, D.C. [Alberta Univ., Edmonton, AB (Canada). Dept. of Agricultural, Food and Nutritional Sciences

    2009-07-01

    The production of renewable fuels and chemicals through pyrolysis of lipid feedstock was investigated with particular focus on the effect of unsaturation on thermal cracking behaviour and product distribution. The feasibility of producing deoxygenated liquid hydrocarbons for renewable fuel and chemical applications was studied using oleic acid and linoleic acid as unsaturated model free fatty acids. These were pyrolyzed in 15 mL batch micro-reactors under a nitrogen atmosphere. The analyzed products were compared to previous work investigating pyrolysis of a fully saturated free fatty acid, stearic acids, as well as fatty acids hydrolyzed from animal fats and vegetable oils. The primary reaction in oleic acid pyrolysis was decarboxylation to heptadecene and carbon dioxide, which is consistent with stearic acid pyrolysis. Some hydrogen addition was indicated by the presence of n-heptacecane. Cracking at the double bond was found to be a dominant reaction because only the C9 and lower alkane/alkenes were present in notable concentrations. In addition, the C10-C20 alkanes/alkenes were not easily distinguishable from other compounds that were found to be alkane isomers. The product mixture was highly influenced by reaction temperatures (350-500 degrees C) and time (0.5-8 hours). Lower temperatures and shorter reaction times resulted in low acid conversion. Although higher temperatures and longer reaction times increased conversion, they eventually caused degeneration into aromatic compounds. Pyrolysis of fatty acids from hydrolyzed beef tallow, poultry tallow and canola oil yielded a similar series of alkanes and alkenes where the product distribution was consistent with an additive effect of the constituent saturated and unsaturated fatty acids.

  7. Characterization of waxes derived from Fischer-Tropsch reactors: Final report

    Energy Technology Data Exchange (ETDEWEB)

    Sturm, G.P. Jr.; Anderson, R.P.; Grigsby, R.D.; Vogh, J.W.; Doughty, D.A.

    1988-12-01

    Methods are described for improved characterization of Fischer-Tropsch (f-T) waxes. With these methods, detailed composition of F-T waxes can be determined, which may lead to improved understanding of the Fischer-Tropsch process and of the processing required to upgrade the waxes into higher value products. The characterization involved separation of the wax into neutral and polar fractions using high performance liquid chromatography on wide port silica with 1.0% (volume) n-propanol in heptane as eluant at 60(degree) to 80(degree)C. the neutral fraction was further spearted into alkanes and alkenes using a silver-loaded, sulfonic-acid-boned silica column with 0.5 to 2.0% (volume) toluene in heptane as eluant at 60(degree) to 80(degree)C. the whole wax and separated fractions were analyzed by infrared, nuclear magnetic resonance, and mass spectrometry. Sample introduction in the mass spectrometry experiments was by probe microdistillation. Results indicated good spearation with some very minor amounts of cycloparfin and virtually no oxygenated compounds in the alkane fraction. The alkene fraction contained mostly alkenes with small amounts of alkanes or oxygen compound and dioxygen compounds (C/sub n/H/sub 2n/O/sub 2/), probably esters or unsaturated diethers. Modifications to and extension of several computer programs made in the course of this study are described in an appendix. this computer software significantly decreased the time and effort involved in processing and interpreting the vast quantity of data acquired in the probe microdistillation mass spectral analysis of the F-T waxes and spearted fractions. 19 refs., 25 figs., 6 tabs.

  8. Predicting the environmental fate properties of petroleum hydrocarbon mixtures

    International Nuclear Information System (INIS)

    The environmental fate and transport of petroleum products for risk assessment can be evaluated based on the physico-chemical properties of an indicator chemical or a surrogate compound, or the whole mixture. A study was conducted to develop a simple representation of the hydrocarbon mixture as if it contained only few constituents, each of which represents a large number of compounds. The products considered are gasoline, diesel fuel, and jet fuel (JP4). Each petroleum hydrocarbon was characterized as a mixture of six constituents: short chain alkanes, long chain alkanes, short chain cycloalkanes and alkenes, long chain cycloalkanes and alkenes, BTEX, and other aromatics. The carbon number used as a cut-off between short and long chain alkanes, alkenes, and cycloalkanes varies with the type of product. Each mixture has different average molecular weight, water solubility, vapor pressure, organic carbon partition coefficient, and air diffusivity. The properties of each constituent of gasoline were derived from the weighted average of all compounds belonging to each constituent group. For diesel fuel and JP4, the properties of each constituent were generated from the properties of the component most representative of the group. Any property that is missing or not available from common literature sources was derived from regression equations developed from the data base for gasoline. These regression equations express the property as function of the number of carbon atoms. The R2 values of the regression equations range from 0.82--0.92. Some case studies involving petroleum product contamination in which the estimated properties were applied are presented

  9. Microalgae Synthesize Hydrocarbons from Long-Chain Fatty Acids via a Light-Dependent Pathway.

    Science.gov (United States)

    Sorigué, Damien; Légeret, Bertrand; Cuiné, Stéphan; Morales, Pablo; Mirabella, Boris; Guédeney, Geneviève; Li-Beisson, Yonghua; Jetter, Reinhard; Peltier, Gilles; Beisson, Fred

    2016-08-01

    Microalgae are considered a promising platform for the production of lipid-based biofuels. While oil accumulation pathways are intensively researched, the possible existence of a microalgal pathways converting fatty acids into alka(e)nes has received little attention. Here, we provide evidence that such a pathway occurs in several microalgal species from the green and the red lineages. In Chlamydomonas reinhardtii (Chlorophyceae), a C17 alkene, n-heptadecene, was detected in the cell pellet and the headspace of liquid cultures. The Chlamydomonas alkene was identified as 7-heptadecene, an isomer likely formed by decarboxylation of cis-vaccenic acid. Accordingly, incubation of intact Chlamydomonas cells with per-deuterated D31-16:0 (palmitic) acid yielded D31-18:0 (stearic) acid, D29-18:1 (oleic and cis-vaccenic) acids, and D29-heptadecene. These findings showed that loss of the carboxyl group of a C18 monounsaturated fatty acid lead to heptadecene formation. Amount of 7-heptadecene varied with growth phase and temperature and was strictly dependent on light but was not affected by an inhibitor of photosystem II. Cell fractionation showed that approximately 80% of the alkene is localized in the chloroplast. Heptadecane, pentadecane, as well as 7- and 8-heptadecene were detected in Chlorella variabilis NC64A (Trebouxiophyceae) and several Nannochloropsis species (Eustigmatophyceae). In contrast, Ostreococcus tauri (Mamiellophyceae) and the diatom Phaeodactylum tricornutum produced C21 hexaene, without detectable C15-C19 hydrocarbons. Interestingly, no homologs of known hydrocarbon biosynthesis genes were found in the Nannochloropsis, Chlorella, or Chlamydomonas genomes. This work thus demonstrates that microalgae have the ability to convert C16 and C18 fatty acids into alka(e)nes by a new, light-dependent pathway. PMID:27288359

  10. Ozone production in four major cities of China: sensitivity to ozone precursors and heterogeneous processes

    Directory of Open Access Journals (Sweden)

    L. K. Xue

    2013-10-01

    Full Text Available Despite a large volume of research over a number of years, our understandings of the key precursors that control tropospheric ozone production and the impacts of heterogeneous processes remain incomplete. In this study, we analyze measurements of ozone and its precursors made at rural/suburban sites downwind of four large Chinese cities – Beijing, Shanghai, Guangzhou and Lanzhou. At each site the same measurement techniques were utilized and a photochemical box model based on the Master Chemical Mechanism (v3.2 was applied, to minimize uncertainties in comparison of the results due to differences in methodology. All four cities suffered from severe ozone pollution. At the rural site of Beijing, export of the well-processed urban plumes contributed to the extremely high ozone levels (up to an hourly value of 286 ppbv, while the pollution observed at the suburban sites of Shanghai, Guangzhou and Lanzhou was characterized by intense in-situ ozone production. The major anthropogenic hydrocarbons were alkenes and aromatics in Beijing and Shanghai, aromatics in Guangzhou, and alkenes in Lanzhou. The ozone production was found to be in a VOCs-limited regime in both Shanghai and Guangzhou, and a mixed regime in Lanzhou. In Shanghai, the ozone formation was most sensitive to aromatics and alkenes, while in Guangzhou aromatics were the predominant ozone precursors. In Lanzhou, either controlling NOx or reducing emissions of olefins from the petrochemical industry would mitigate the local ozone production. The potential impacts of several heterogeneous processes on the ozone formation were assessed. The hydrolysis of dinitrogen pentoxide (N2O5, uptake of the hydroperoxyl radical (HO2 on particles, and surface reactions of NO2 forming nitrous acid (HONO present considerable sources of uncertainty in the current studies of ozone chemistry. Further efforts are urgently required to better understand these processes and refine atmospheric models.

  11. Direct hydrothermal liquefaction of undried macroalgae Enteromorpha prolifera using acid catalysts

    International Nuclear Information System (INIS)

    Highlights: • Bio-oil from liquefaction of wet E. prolifera was as feasible as dry powder. • Adding acid catalysts could improve the flow property of bio-oil. • Alkenes in the bio-oil converted to ketones in the presence of acid catalysts. • Content of 5-methyl furfural increased in the bio-oil obtained with acid catalysts. • Esters were formed in the bio-oil when adding sulfuric acid as a catalyst. - Abstract: Direct liquefaction of macroalgae Enteromorpha prolifera without predrying treatment was performed in a batch reactor. Effects of temperature, reaction time, biomass-to-water ratio and acid catalysts (sulfuric acid and acetic acid) on liquefaction products were investigated. Raw material and liquefaction products were analyzed by elemental analysis, Fourier transform infrared (FT-IR) and gas chromatography–mass spectrometry (GC–MS). Results showed that liquefaction at 290 °C for 20 min with 1:3 biomass-to-water ratio produced the highest bio-oil yield of 28.4 wt%, and high heating value (HHV) was 29.5 MJ/kg. Main components of bio-oil were fatty acids, ketones, alkenes and 5-methyl furfural, and main components of water soluble organics (WSOs) were pyridines, carboxylic acids and glycerol. In the bio-oil obtained with acid catalysts, content of ketones significantly increased while alkenes disappeared. Content of 5-methyl furfural also increased. Flow property of bio-oils was improved in the presence of acid catalysts. Moreover, esters were formed when adding sulfuric acid

  12. Status study of aviation biofuel at home and abroad%国内外生物航油研究现状

    Institute of Scientific and Technical Information of China (English)

    陈俊英; 马晓建; 冯向应; 韩秀丽; 李红伟

    2012-01-01

    介绍了生物航油的特性、原料、生产方法及利用现状.用微藻生产生物航油是今后研究的主要方向,但微藻大规模培养、收集以及提取都存在问题,尚未工业化.植物油需要进行复杂的催化裂解处理,将高碳烷烃分解为低链烷烃;生物质可分解为合成气,然后以合成气为原料,利用费一托合成反应生产相当于煤油的航空代用燃料;热裂解利用生物质为原料,经快速热裂解生产液体产物,但整体产物中轻质烃的产率较低.%In this paper, the property, raw material, production method and utilization status of aviation biofuel was introduced.The research of aviation biofuel produced by algal would the major orientation in future, but there are some problems in the large-scale cultivation, collection and extraction processes of microalgae, not industrial yet. Vegetable oil need complicated catalytic pyrol-ysis,the heavy alkenes could be cracked into light alkenes. The biomass could be decomposed to synthesis gas. Then the synthesis gas was used as raw materials, and by Fischer-Tropsch reaction set) to produce the aviation substitute fuel equivalent to kerosene. The cellulosic biomass could produce liquids by fast pyrolysis processes. But the production rate of light alkene is low.

  13. An experimental and theoretical study of reaction steps relevant to the methanol-to-hydrocarbons reaction

    Energy Technology Data Exchange (ETDEWEB)

    Svelle, Stian

    2004-07-01

    The primary objective of the present work is to obtain new insight into the reaction mechanism of the zeolite catalyzed methanol-to-hydrocarbons (MTH) reaction. It was decided to use both experimental and computational techniques to reach this goal. An investigation of the n-butene + methanol system was therefore initiated. Over time, it became apparent that it was possible to determine the rate for the methylation of n-butene by methanol. The ethene and propene systems were therefore reexamined in order to collect kinetic information also for those cases. With the development of user-friendly quantum chemistry programs such as the Gaussian suite of programs, the possibility of applying quantum chemical methods to many types of problems has become readily available even for non-experts. When performing mechanistic studies, there is quite often a considerable synergy effect when combining experimental and computational approaches. The methylation reactions mentioned above turned out to be an issue well suited for quantum chemical investigations. The incentive for examining the halomethane reactivity was the clear analogy to the MTH reaction system. Alkene dimerization was also a reaction readily examined with quantum chemistry. As discussed in the introduction of this thesis, polymethylbenzenes, or their cationic counterparts, are suspected to be key intermediates in the MTH reaction. It was therefore decided to investigate the intrinsic reactivity of these species in the gas-phase by employing sophisticated mass spectrometric (MS) techniques in collaboration with the MS group at the Department of Chemistry, University of Oslo The data thus obtained will also be compared with results from an ongoing computational study on gas phase polymethylbenzenium reactivity. 6 papers presenting various studies are included. The titles are: 1) A Theoretical Investigation of the Methylation of Alkenes with Methanol over Acidic Zeolites. 2) A Theoretical Investigation of the

  14. Key processes in ruthenium-catalysed olefin metathesis

    OpenAIRE

    Nelson, David J.; Manzini, Simone; Urbina-Blanco, César A.; Nolan, Steven P.

    2014-01-01

    The authors acknowledge the following sources of funding: the EPSRC, the ERC (via Advanced Investigator Grant ‘FUNCAT’ to SPN), the EC (via FP7 project ‘EUMET’) and Umicore (for gifts of materials). SPN is a Royal Society Wolfson Research Merit Award holder. While the fundamental series of [2+2]cycloadditions and retro[2+2]cycloadditions that make up the pathways of ruthenium-catalysed metathesis reactions is well-established, the exploration of mechanistic aspects of alkene metathesis con...

  15. Ruthenium-Mediated Cycloaromatization of Tri-Pi Systems

    OpenAIRE

    Cope, Stephen Kyle

    2015-01-01

    This work describes mechanistic studies into a ruthenium-mediated cycloaromatization of dienynes. The results of deuterium labeling experiments are consistent with a mechanism that proceeds via a 6-electrocyclization to form an 4-isobenzene adduct followed by a metal-mediated [1,5]-hydride shift. The cycloaromatization of dienynes with substituents in the E-position of the distal alkene is proposed to give arene product via a process involving two sequential [1,2]-hydride shifts. Dienynes b...

  16. Highly Active Carbene Ruthenium Catalyst for Metathesis of 1-Hexene

    Institute of Scientific and Technical Information of China (English)

    BAI Chen-Xi; ZHANG Zhi-Qiang; L(U) Xiao-Bing; HE Ren; ZHANG Wen-Zhen; LU Shu-Lai

    2006-01-01

    A new carbene ruthenium complex, 1,3-bis(2,6-dimethylphenyl)-4,5-dihydroimidazol-2-ylidene)(PPh3)Cl2-Ru=CHPh, was synthesized and used as catalyst for the metathesis of 1-hexene. The resulting complex exhibited very high catalytic activity whose TOF is up to 6680 h-1. However, at the same time significant olefin isomerization was observed and could be surpressed by changing reaction conditions, such as temperature, time, alkene/Ru molar ratio and solvent.

  17. Comparative Studies on Mass Spectrometric Fragmentation of Linear Chiral Secondary Alcohols (R) -1-(4-Alkylphenyl) and (R) -1-(4-Alkoxyphenyl/Alkylthiophenyl) Alcohols

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Mass spectrometric behaviour of (R)-1-(4-alkylphenyl) alcohols, 1-(4-alkoxylphenyl) alcohols, and 1-(4-alkylthiophenyl) alcohols were studied with the aid of mass-analyzed ion kinetic energy spectrometry under electron impact ionization. All the title compounds show a tendency to eliminate a water molecule to form alkene ions and undergo an a-cleavage to produce protonated aldehyde ions by the loss of alkyl radicals. Except these two common fragment ions, they also show some different fragmentations due to with or without oxy/thioether-linkage.

  18. Synthesis of β-haloacids by radiation

    International Nuclear Information System (INIS)

    Hydrogen halides add to alkenes yielding the corresponding haloalkane. The addition of HX ordinally follows the course of Markownikoff's rule. In this paper we analyze the HBr addition reaction to unsaturated carboxylic acids. The course of the addition is anti-Markownikoff. This implies that the reaction goes through free radical mechanism and the haloacid formed is in the β-position. The acids under study are fumaric, itaconic, citraconic acids and the methyl ester of fumaric acid. The β-haloacids formed are easily purified from the bulk solutions. (author)

  19. Synthesis and characterization of a small analogue of the anticancer natural product leinamycin

    OpenAIRE

    Keerthi, Kripa; Rajapakse, Anuruddha; Sun, Daekyu; Gates, Kent S.

    2012-01-01

    Leinamycin (1) is a Streptomyces-derived natural product that displays nanomolar IC50 values against human cancer cell lines. In the work described here, we report the synthesis and characterization of a small leinamycin analogue 19 that closely resembles the “upper-right quadrant” of the natural product, consisting of an alicyclic 1,2-dithiolan-3-one 1-oxide heterocycle connected to an alkene by a two-carbon linker. The results indicate that this small analogue contains the core set of funct...

  20. Methods for attaching polymerizable ceragenins to water treatment membranes using silane linkages

    Science.gov (United States)

    Hibbs, Michael; Altman, Susan J.; Jones, Howland D. T.; Savage, Paul B.

    2013-09-10

    This invention relates to methods for chemically grafting and attaching ceragenin molecules to polymer substrates; methods for synthesizing ceragenin-containing copolymers; methods for making ceragenin-modified water treatment membranes and spacers; and methods of treating contaminated water using ceragenin-modified treatment membranes and spacers. Ceragenins are synthetically produced antimicrobial peptide mimics that display broad-spectrum bactericidal activity. Alkene-functionalized ceragenins (e.g., acrylamide-functionalized ceragenins) can be attached to polyamide reverse osmosis membranes using amine-linking, amide-linking, UV-grafting, or silane-coating methods. In addition, silane-functionalized ceragenins can be directly attached to polymer surfaces that have free hydroxyls.

  1. Diamond surface functionalization with biomimicry - Amine surface tether and thiol moiety for electrochemical sensors

    Science.gov (United States)

    Sund, James B.; Causey, Corey P.; Wolter, Scott D.; Parker, Charles B.; Stoner, Brian R.; Toone, Eric J.; Glass, Jeffrey T.

    2014-05-01

    The surface of conducting diamond was functionalized with a terminal thiol group that is capable of binding and detecting nitrogen-oxygen species. The functionalization process employed multiple steps starting with doped diamond films grown by plasma enhanced chemical vapor deposition followed by hydrogen termination and photochemical attachment of a chemically protected amine alkene. The surface tether was deprotected to reveal the amine functionality, which enabled the tether to be extended with surface chemistry to add a terminal thiol moiety for electrochemical sensing applications. Each step of the process was validated using X-ray photoelectron spectroscopy analysis.

  2. Cis/trans Coordination in olefin metathesis by static and molecular dynamic DFT calculations

    KAUST Repository

    Poater, Albert

    2014-05-25

    In regard to [(N-heterocyclic carbene)Ru]-based catalysts, it is still a matter of debate if the substrate binding is preferentially cis or trans to the N-heterocyclic carbene ligand. By means of static and molecular dynamic DFT calculations, a simple olefin, like ethylene, is shown to be prone to the trans binding. Bearing in mind the higher reactivity of trans isomers in olefin metathesis, this insight helps to construct small alkene substrates with increased reactivity. © 2014 Springer Science+Business Media New York.

  3. Towards selective catalytic oxidations using in-situ generated H2O2

    OpenAIRE

    Sullivan, James A; O'Callaghan, Niamh

    2013-01-01

    A series of Ti-modified mesoporous SiO2 materials (SBA-15 and MCF) are prepared, characterised and used as catalysts in the selective epoxidation of a probe alkene (cyclohexene) using H2O2 as an oxidising agent. Similarly, a series of mesoporous SiO2-supported monometallic and bimetallic DMAP-stabilized Au and Pd nanoparticles were prepared, characterised and used as catalysts in the production of H2O2 from dilute H2(g) + O2(g) mixtures.The metallic nanoparticles were then supported on the Ti...

  4. Pumping of hydrocarbons using non-evaporable getters

    International Nuclear Information System (INIS)

    Pumping speed measurements have been obtained for a number of gaseous hydrocarbons including members of the alkene, alkadiene, and cycloalkane groups as a function of temperature using a Zr-Al alloy getter. Pumping speeds were obtained by analysis of an exponential least squares fit to the pressure decay curve following introduction of each gas. It was found that these pumping speeds are relatively high (up to 400 1/s) and exhibit, with only a few exceptions, little temperature dependence. This is in contrast to the earlier reported results for the alkane series

  5. Structural and textural study of Ni and/or Co in a common molybdate lattice as catalysts

    Directory of Open Access Journals (Sweden)

    Boukhlouf H.

    2013-09-01

    Full Text Available This work deals with the search for new molybdate catalyst formulations, which are known to be active in light alkane oxidative dehydrogenation, a process which could be replace in the near future the common steam cracking and pure dehydrogenation processes currently used for the production of alkenes. Co, Ni and mixed Ni-Co molybdates of various compositions are prepared by a modified coprecipitation procedure from metal nitrates and ammonium heptamolybdate. Their structural and textural properties were studied by XRD, Raman, B.E.T and XPS. Textural and structural properties of the materials are correlated to the composition.

  6. Ethanol Conversion on Cyclic (MO3)3 (M = Mo, W) Clusters

    Energy Technology Data Exchange (ETDEWEB)

    Li, Zhenjun; Fang, Zongtang; Kelley, Matthew S.; Kay, Bruce D.; Rousseau, Roger J.; Dohnalek, Zdenek; Dixon, David A.

    2014-03-06

    Oxides of molybdenum and tungsten are an important class of catalytic materials with applications ranging from isomerization of alkanes and alkenes, partial oxidation of alcohols, selective reduction of nitric oxide and metathesis of alkeness.[1-10] While many studies have focused on the structure - function relationships, the nature of high catalytic activity is still being extensively investigated. There is a general agreement that the activity of supported MOx (M = W, Mo) catalysts is correlated with the presence of acidic sites, where the catalytic activity is strongly affected by the type of oxide support, delocalization of electron density, structures of tungsten oxide domains and presence of protons

  7. Safety testing of 18650-style Li-Ion cells

    Energy Technology Data Exchange (ETDEWEB)

    CRAFTS,CHRIS C.; BOREK III,THEODORE T.; MOWRY,CURTIS DALE

    2000-06-08

    To address lithium-ion cell safety issues in demanding power applications, electrical and thermal abuse tests were performed on 18650 sized cells. Video and electrically monitored abuse tests in air included short circuit, forced overcharge, forced reversal, and controlled overheating (thermal) modes. Controlled overheating tests to 200 C were performed in a sealed chamber under a helium atmosphere and the gases released from the cell during thermal runaway were analyzed at regular intervals using gas chromatography and mass spectrometry. In addition to alkane and alkene solvent breakdown fragments, significant H{sub 2} was detected and evidence that HF was evolved was also found.

  8. The Catalytic Enantioselective Total Synthesis of (+)‐Liphagal

    DEFF Research Database (Denmark)

    Day, Joshua J.; McFadden, Ryan M.; Virgil, Scott C.;

    2011-01-01

    Ring a ding: The first catalytic enantioselective total synthesis of the meroterpenoid natural product (+)-liphagal is disclosed. The approach showcases a variety of technology including enantioselective enolate alkylation, a photochemical alkyne-alkene [2+2] reaction, microwaveassisted metal...... establish the trans homodecalin system found in the natural product...... catalysis, and an intramolecular aryne capture cyclization reaction. Pivotal to the successful completion of the synthesis was a sequence involving ring expansion from a [6-5-4] tricycle to a [6-7] bicyclic core followed by stereoselective hydrogenation of a sterically occluded tri-substituted olefin to...

  9. Debenzylative Cycloetherification: An Overlooked Key Strategy for Complex Tetrahydrofuran Synthesis.

    Science.gov (United States)

    Tikad, Abdellatif; Delbrouck, Julien A; Vincent, Stéphane P

    2016-07-01

    Tetrahydrofuran (THF) is a major structural feature found in many synthetic and natural products displaying a variety of biological properties. This review summarizes the main synthetic approaches that have been developed to construct tetrahydrofuran moieties involving debenzylative cycloetherification reactions (DBCE). Interestingly, this reaction is regio- and stereoselective without the requirement of a selective protection/deprotection strategy. Many applications of this process have been reported, including carbafuranoside synthesis, regioselective deprotection of the benzyl group positioned γ to an alkene, and total synthesis of natural products. The stereochemical outcome and the mechanism of these interesting transformations are also discussed. PMID:27304427

  10. The carbonyl oxide-aldehyde complex: a new intermediate of the ozonolysis reaction

    Science.gov (United States)

    Cremer, Dieter; Kraka, Elfi; McKee, M. L.; Radharkrishnan, T. P.

    1991-12-01

    MP4(SDQ)/6-31G (d,p) calculations suggest that the ozonolysis of alkenes in solution phase does not proceed via carbonyl oxide, but via a dipole complex between aldehyde and carbonyl oxide, which is 9 kcal/mol more stable than the separated molecules. The dipole complex is probably formed in the solvent cage upon decomposition of primary ozonide to aldehyde and carbonyl oxide. Rotation of either aldehyde or carbonyl oxide in the solvent cage leads to an antiparallel alignment of molecular dipole moments and dipole-dipole attraction.

  11. I. Collagen-like polypeptides. II. Helix-turn-helix peptides and turn mimetics.

    OpenAIRE

    Dai, Nan

    2008-01-01

    Collagen is one of the most important and abundant proteins in mammals. It consists of three left-handed PPII helixes coiled along a common axis to form a very compact right-handed super helix. The primary structure is shown to be (Gly-Xaa-Yaa)n repeats with high content of prolyl residues at both Xaa and Yaa positions. Cis-trans isomerization of the prolyl amide bonds is one of the rate-limiting steps during collagen triple helix folding. The conformationally locked alkene isosteres Fmoc-...

  12. Two-chamber hydrogen generation and application: access to pressurized deuterium gas.

    Science.gov (United States)

    Modvig, Amalie; Andersen, Thomas L; Taaning, Rolf H; Lindhardt, Anders T; Skrydstrup, Troels

    2014-06-20

    Hydrogen and deuterium gas were produced and directly applied in a two-chamber system. These gaseous reagents were generated by the simple reaction of metallic zinc with HCl in water for H2 and DCl in deuterated water for D2. The setup proved efficient in classical Pd-catalyzed reductions of ketones, alkynes, alkenes, etc. in near-quantitative yields. The method was extended to the synthesis and isotope labeling of quinoline and 1,2,3,4-tetrahydroquinoline derivatives. Finally, CX-546 and Olaparib underwent efficient Ir-catalyzed hydrogen isotope exchange reactions. PMID:24870212

  13. Zirconium-catalyzed intermolecular hydrophosphination using a chiral, air-stable primary phosphine.

    Science.gov (United States)

    Bange, Christine A; Ghebreab, Michael B; Ficks, Arne; Mucha, Neil T; Higham, Lee; Waterman, Rory

    2016-02-01

    Catalytic hydrophosphination of alkenes using a chiral, air-stable primary phosphine, (R)-[2'-methoxy(1,1'-binapthalen)-2-yl]phosphine, (R)-MeO-MOPH2, proceeds under mild conditions with a zirconium catalyst, [κ(5)-N,N,N,N,C-(Me3SiNCH2CH2)2NCH2CH2NSiMe2CH]Zr (1), to selectively furnish anti-Markovnikov, air-stable secondary phosphines or tertiary phosphines with slight modification of the protocol. An intermediate in the catalysis, [(N3N)Zr(R)-MeO-MOPH] (4), was structurally characterized. PMID:26530894

  14. A cross-linked manganese porphyrin as highly efficient heterogeneous catalyst for selective oxidation of cycloalkenes/alkanes

    Indian Academy of Sciences (India)

    Manoj Kumar Singh; Debkumar Bandyopadhyay

    2014-11-01

    The monomeric tetrakis (5,10,15,20--bromophenyl) manganese porphyrin has been converted to a micro- and mesoporous material of surface area 1301m2/g by carefully manipulating the reaction conditions of Suzuki coupling. This material has been tested for its oxidizing ability of cycloalkenes/alkane by -BuOOH, H2O2, CumOOH and m-CPBA. The catalyst is found to oxidize the alkenes selectively and it is not destroyed even 5% in 10 cycles of successive oxidation processes in one pot. The parent monomer gets destroyed appreciably under similar oxidizing conditions.

  15. Production of Hydrocarbon Liquid by Thermal Pyrolysis of Paper Cup Waste

    OpenAIRE

    Bijayani Biswal; Sachin Kumar; Singh, R. K.

    2013-01-01

    The paper cup waste was pyrolysed in a stainless steel semibatch reactor at a temperature range of 325°C to 425°C and at a heating rate of 20°C min−1 with an aim to study the physical and chemical characteristics of the obtained hydrocarbon liquid and to determine its feasibility as a commercial fuel. The maximum liquid yield was 52% at 400°C. The functional groups present in the liquid are aldehydes, ketones, carboxylic acids, esters, alkenes, and alkanes. It was found that the pyrolytic li...

  16. Probing cytochrome P450-mediated activation with a truncated azinomycin analogue

    OpenAIRE

    Vinader, Victoria; Sadiq, Maria; Sutherland, Mark; Huang, Menying; Loadman, Paul; Elsalem, Lina; Shnyder, Steven; Cui, Hongjuan; Afarinkia, Kamyar; Searcey, Mark; Patterson, Laurence; Pors, Klaus

    2015-01-01

    A deactivated alkene precursor (IC50 = 81 μM) to the azinomycin epoxide natural product can be bioactivated by several cytochromes P450 (CYP) to generate antiproliferative metabolites with increased potency (IC50 = 1-30 μM) in CHOwt cells. CYP1A1 and 3A4 were shown to generate exclusively the unnatural and the natural-configured azinomycin epoxide diastereoisomer respectively, while CYP1B1 produced both epoxides in a 3:1 mixture. The antiproliferative activity is linked to DNA damage as demon...

  17. Preparation of Molecular Sieve Catalyst and Application in the Catalytic Oxidation Treatment of Waste Water

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    @@ Citric acid is an important additive in foods, cosmetics, medicine and so on, but it discharges about 10 ton of factory effluent when 1 ton of citric acid is produced. The COD of the factory effluent is near 20000 mg/L. The treatment of citric acid factory effluent is a serious problem in environmental chemistry. It is found that molecular sieve support metal complexes have high catalytic activity in aerobic oxidation of alkene [1,2]. In this paper, a kind of molecular sieve catalyst was prepared. The catalyst was used for the treatment of citric acid factory effluent by method of catalytic oxygen oxidation.

  18. Oxidative capacity of the Mexico City atmosphere – Part 1: A radical source perspective

    Directory of Open Access Journals (Sweden)

    M. J. Molina

    2007-04-01

    Full Text Available A detailed analysis of OH, HO2 and RO2 radical sources is presented for the near field photochemical regime inside the Mexico City Metropolitan Area (MCMA. During spring of 2003 (MCMA-2003 field campaign an extensive set of measurements was collected to quantify time resolved ROx (sum of OH, HO2, RO2 radical production rates from day- and nighttime radical sources. The Master Chemical Mechanism (MCMv3.1 was constrained by measurements of (1 concentration time-profiles of photosensitive radical precursors, i.e., nitrous acid (HONO, formaldehyde (HCHO, ozone (O3, glyoxal (CHOCHO, and other oxygenated volatile organic compounds (OVOCs; (2 respective photolysis-frequencies (J-values; (3 concentration time-profiles of alkanes, alkenes, and aromatic VOCs (103 compound are treated and oxidants, i.e., OH- and NO3 radicals, O3; and (4 NO, NO2, meteorological and other parameters. The ROx production rate was calculated directly from these observations; MCM was used to estimate further ROx production from unconstrained sources, and express overall ROx production as OH-equivalents (i.e., taking into account the propagation efficiencies of RO2 and HO2 radicals into OH radicals. Daytime radical production is found to be about 10-25 times higher than at night; it does not track the abundance of sunlight. 12-h average daytime contributions of individual sources are: HCHO and O3 photolysis, each about 20%; O3/alkene reactions and HONO photolysis, each about 15%; unmeasured sources about 30%. While the direct contribution of O3/alkene reactions appears to be moderately small, source-apportionment of ambient HCHO and HONO identifies O3/alkene reactions as being largely responsible for jump-starting photochemistry about one hour after sunrise. The peak radical production is found to be higher than in any other urban influenced environment studied to date; further, differences exist in the timing of radical production. Our measurements and analysis comprise a

  19. An efficient catalytic reductive amination: A facile one-pot access to 1,2-dihydropyrrolo[3,4-b]indol-3(4H)-ones by using B(C6F5)3/NaBH4

    Indian Academy of Sciences (India)

    Atulya Nagarsenkar; Santosh Kumar Prajapti; Nagendra Babu Bathini

    2015-04-01

    An efficient combination of B(C6F5)3 and NaBH4 was developed for direct reductive amination of aldehydes. A wide range of functional groups such as ester, nitro, nitrile, halogen, alkene, heterocycles were tolerated. Also, acid sensitive protecting groups like TBDMS and TBDPS were not affected. In addition, the present methodology was extended for tandem amination-amidation of 3-formyl-indole-2-carboxylic acids with substituted anilines to afford 1,2-dihydropyrrolo[3,4-b]indol-3(4H)-ones.

  20. Volatile Components from Old Plum Brandies

    OpenAIRE

    Tešević, Vele; Nikićević, Ninoslav; Jovanović, Anka; Djoković, Dejan; Vujisić, Ljubodrag; Vučković, Ivan; Bonić, Mirjana

    2005-01-01

    Gas chromatography and GC/MS methods were used to detect volatile components of three home-made natural old plum brandy samples and one sample of industrially-produced plum brandy. Gas chromatography and gas chromatography-mass spectrometric analysis of this extracts led to the identification of 99 components, including 46 esters, 7 hydrocarbons (alkanes and alkenes), 3 aldehydes, 9 alcohols, 1 lactone, 1 ketone, 8 acetals, 14 terpenes, 8 acids and 2 phenols. Ethyl esters of C8–C18 acids were...

  1. Investigations into the chemistry of atmospheric peroxides. Final report. Pt. A and B; Untersuchungen zur Chemie der atmosphaerischen Peroxide. Abschlussbericht. T. A und B

    Energy Technology Data Exchange (ETDEWEB)

    Becker, K.H.; Brockmann, K.J.; Bechara, J. [Wuppertal Univ. (Gesamthochschule) (Germany). Lehrgebiet Physikalische Chemie; Klockow, D.; Cramer, C.; Esser, G.; Hoffmann, T.; Jacob, P.; Troost, G.; Valdes, J. [Dortmund Univ. (Germany). Inst. fuer Spektrochemie und Angewandte Spektroskopie

    1992-06-01

    This project investigates the atmospheric-chemical behaviour of hydroperoxides as a part of the atmospheric oxidants blamed for contributing to novel forest decline. In particular, the investigations covered such processes as form hydrogen peroxide in the gas or liquid phase or on icy surfaces, by the effect of light or by reactions of ozone with biogenous alkenes. A diode laser spectroscope was used in combination with a long-path infra-red absorption cell and a temperature-adjustable photoreactor for studying the reactions of ozone with different terpenes and some non-biogenic alkenes, under atmospheric conditions, regarding H{sub 2}O{sub 2} formation. The reaction with water vapour of the intermediate products from the ozone/terpene reactions represents a hitherto unknown source of H{sub 2}O{sub 2} in forest air. This formation of H{sub 2}O{sub 2} acquires importance particularly where high levels of atmospheric NO (> 10 pptV) and ozone occur at a close distance to intense sources of biogenic alkenes. (orig./EF). [Deutsch] Im vorliegenden Projekt wurde das luftchemische Verhalten der Hydroperoxide als Teil der atmosphaerischen Oxidantien, die fuer neuartige Waldschaeden mitverantwortlich gemacht werden, untersucht. Insbesondere erstreckten sich die Untersuchungen auf Prozesse, die mit Lichteinwirkung oder durch Reaktionen von Ozon mit biogenen Alkenen in der Gasphase, in der Fluessigphase und auf Eisoberflaechen Wasserstoffperoxid bilden. Das Diodenlaserspektrometer wurde in Verbindung mit der Langwegabsorptionszelle und einem temperierbaren Photoreaktor benutzt, um die Reaktionen von Ozon mit verschiedenen Terpenen und einigen nicht-biogenen Alkenen unter atmosphaerischen Bedingungen auf die Bildung von H{sub 2}O{sub 2} hin zu untersuchen. Die Reaktion der bei den Ozon-Terpenreaktionen entstehenden Zwischenprodukte mit Wasserdampf stellt eine bisher nicht bekannte H{sub 2}O{sub 2}-Quelle in der Waldluft dar. Diese H{sub 2}O{sub 2}-Bildung gewinnt besonders bei

  2. Exposure of the hydrophobic components of porcine lung surfactant to oxidant stress alters surface tension properties.

    OpenAIRE

    Gilliard, N; Heldt, G P; Loredo, J.; Gasser, H; Redl, H; Merritt, T A; Spragg, R G

    1994-01-01

    We have tested the hypothesis that oxidation of lung surfactant results in loss of surface tension lowering function. Porcine lung surfactant was exposed to conditions known to cause lipid peroxidation (0.2 mM FeCl2 + 0.1 mM H2O2 or 5 microM CuCl2). Lipid peroxidation was verified by detection of conjugated dienes, thiobarbituric acid reactive substances, fluorescent products, hydroxy alkenals, and loss of unsaturated fatty acids. Exposed samples had significantly diminished surface tension l...

  3. Reduction of CO2 to C1 products and fuel

    Science.gov (United States)

    Mill, T.; Ross, D.

    2002-01-01

    Photochemical semiconductor processes readily reduced CO2 to a broad range of C1 products. However the intrinsic and solar efficiencies for the processes were low. Improved quantum efficiencies could be realized utilizing quantum-sized particles, but at the expense of using less of the visible solar spectrum. Conversely, semiconductors with small bandgaps used more of the visible solar spectrum at the expense of quantum efficiency. Thermal reduction of CO2 with Fe(II) was thermodynamically favored for forming many kinds of organic compounds and occurred readily with olivine and other Fe(II) minerals above 200??C to form higher alkanes and alkenes. No added hydrogen was required.

  4. Decomposition kinetics and mechanism of n-hexadecane-1,2- 13C 2 and dodec-1-ene-1,2-13C2 doped in petroleum and n-hexadecane

    Science.gov (United States)

    Burnham, Alan K.; Gregg, Hugh R.; Ward, Raymond L.; Knauss, Kevin G.; Copenhaver, Sally A.; Reynolds, John G.; Sanborn, Russell

    1997-09-01

    Isotopically labeled n-hexadecane doped at the percent level in three crude oils is used to determine the intrinsic decomposition kinetics and mechanism of n-alkanes in petroleum. Adjacent 13C labels at the end of the hexadecane and dodecene give a mass fragment sufficiently unique that its disappearance and many of its products can be followed by ordinary gas chromatography-mass spectrometry. Additional structural details of the labeled reaction products are measurable by the NMR INADEQUATE technique, which detects only adjacent 13C atoms. Samples were heated at temperatures ranging from 310 to 360°C in capillary glass tubes and Dickson autoclaves. At temperatures around 350°C, n-alkane decomposition in dissimilar oil matrices forms primarily normal alkanes smaller than the starting alkane at a rate about 60% as fast as the decomposition of the neat alkane. Unlike in neat hexadecane, no significant branched alkanes are formed from the labeled hexadecane in crude oil by alkylation of alkene intermediates. Doping the oils and n-hexadecane with labeled dodecene confirms that alkenes in two of the three oils are rapidly converted primarily to the corresponding alkanes, while reaction of alkenes in hexadecane forms primarily branched alkanes. Reaction of alkenes in the high paraffin oil was intermediate in characteristics. One autoclave experiment included water to assess the importance of water during pyrolysis, with the result that the alkane decomposition rate is affected very little. However, coking of aromatics is inhibited, and there is a significant increase in the production of both H 2 and CO 2 gas with water present, indicating that water is chemically reactive under these conditions. At temperatures around 310°C, the decomposition rate of neat hexadecane is roughly equal to that in a high paraffin oil and substantially slower than in North Sea and high sulfur oil, suggesting that the effect of the oil matrix has switched from suppression of propagation

  5. Lewis Acid Catalysis in the Oxidative Cycloaddition of Thiophenes

    OpenAIRE

    Li, Yuanqiang; Thiemann, Thies; Sawada, Tsuyoshi; Mataka, Shuntaro; Tashiro, Masashi

    1997-01-01

    Thiophenes 1 were treated with m-chloroperbenzoic acid (m-CPBA) under BF3·Et2O catalysis to afford thiophene S-monoxides. These could be reacted in situ as intermediary species with a number of dienophiles to provide arenes (with alkynes as dienophiles) or 7-thiabicyclo[2.2.1]hept-2-ene 7-oxides (with alkenes as dienophiles). It was also possible to isolate thiophene S-monoxides in solution and to cycloadd them in a second step. In either way it could be shown that the use of BF3·Et2O enhance...

  6. A Facile and Efficient Synthesis of (15R)-Latanoprost from Chiral Precursor Corey Lactone Diol

    Indian Academy of Sciences (India)

    K Vijendhar; B Srinivas; Sathyanarayana Boodida

    2015-11-01

    An efficient asymmetric synthetic route for the synthesis of anti-glaucoma agent, (15R)-latanoprost using Corey lactone diol as chiral substrate under Swern oxidation, allylic reduction and Wittig reaction conditions has been developed. In this method, reduction of keto and alkene functional groups has been achieved in a single step using low cost catalyst NiCl2/NaBH4 in methanol. This new synthetic protocol is a good alternative for the synthesis of latanoprost with high stereo selectivity and improved yield.

  7. Chemical datuments as scientific enablers.

    Science.gov (United States)

    Rzepa, Henry S

    2013-01-01

    This article is an attempt to construct a chemical datument as a means of presenting insights into chemical phenomena in a scientific journal. An exploration of the interactions present in a small fragment of duplex Z-DNA and the nature of the catalytic centre of a carbon-dioxide/alkene epoxide alternating co-polymerisation is presented in this datument, with examples of the use of three software tools, one based on Java, the other two using Javascript and HTML5 technologies. The implications for the evolution of scientific journals are discussed. PMID:23343381

  8. Chemical datuments as scientific enablers

    Directory of Open Access Journals (Sweden)

    Rzepa Henry S

    2013-01-01

    Full Text Available Abstract This article is an attempt to construct a chemical datument as a means of presenting insights into chemical phenomena in a scientific journal. An exploration of the interactions present in a small fragment of duplex Z-DNA and the nature of the catalytic centre of a carbon-dioxide/alkene epoxide alternating co-polymerisation is presented in this datument, with examples of the use of three software tools, one based on Java, the other two using Javascript and HTML5 technologies. The implications for the evolution of scientific journals are discussed.

  9. Targeting p53 Null Neuroblastomas through RLIP76**

    OpenAIRE

    Singhal, Jyotsana; Yadav, Sushma; Nagaprashantha, Lokesh Dalasanur; Vatsyayan, Rit; SINGHAL, SHARAD S.; Awasthi, Sanjay

    2011-01-01

    The search for p53-independent mechanism of cancer cell killing is highly relevant to pediatric neuroblastomas, where successful therapy is limited by its transformation into p53 mutant and a highly drug-resistant neoplasm. Our studies on the drug-resistant p53 mutant as compared with drug-resistant p53 wild-type neuroblastoma revealed a novel mechanism for resistance to apoptosis: a direct role of p53 in regulating the cellular concentration of pro-apoptotic alkenals by functioning as a spec...

  10. Single-Event Microkinetics for Methanol to Olefins on H-ZSM-5

    OpenAIRE

    Kumar, Pravesh; Thybaut, Joris W.; Svelle, Stian; Olsbye, Unni; Guy B. Marin

    2013-01-01

    A single-event microkinetic (SEMK) model was developed for the conversion of methanol to olefins (MTO) and used in the assessment of experimental data obtained on H-ZSM-5 with a Si/Al ratio of 200. The experiments were performed at temperatures from 643 to 753 K, space times between 0.5 and 6.5 kg(cat).s mol(-1) and at atmospheric pressure. Dimethyl ether (DME) and primary olefins formation through aromatic hydrocarbon pool and higher olefins formation via the alkene homologation cycle, was i...

  11. Alkyl phenols and saponins from the roots of Labisia pumila (Kacip Fatimah).

    Science.gov (United States)

    Ali, Zulfiqar; Khan, Ikhlas A

    2011-11-01

    Recently, there is a remarkable boom in the sales of Labisia pumila (Kacip Fatimah) in the Malaysian market, as an extract of the plant is used to gain energy and libido as well as to treat many other ailments. A chemical analysis of its roots was undertaken and three metabolites, demethylbelamcandaquinone B (1), fatimahol (2), and dexyloprimulanin (3) together with 21 known compounds including epoxyoleanane glycosides, alkenated phenolics, cerebroside, glycerogalactolipids, and lipids were isolated and identified. Structure elucidation was achieved by spectroscopic and chemical studies. The MeOH extract of KF and compounds 12 and 13 exhibited moderate in vitro antibacterial activity. PMID:21784496

  12. Palladium-catalyzed coupling reactions of tetrafluoroethylene with arylzinc compounds.

    Science.gov (United States)

    Ohashi, Masato; Kambara, Tadashi; Hatanaka, Tsubasa; Saijo, Hiroki; Doi, Ryohei; Ogoshi, Sensuke

    2011-03-16

    Organofluorine compounds are widely used in all aspects of the chemical industry. Although tetrafluoroethylene (TFE) is an example of an economical bulk organofluorine feedstock, the use of TFE is mostly limited to the production of poly(tetrafluoroethylene) and copolymers with other alkenes. Furthermore, no catalytic transformation of TFE that involves carbon-fluorine bond activation has been reported to date. We herein report the first example of a palladium-catalyzed coupling reaction of TFE with arylzinc reagents in the presence of lithium iodide, giving α,β,β-trifluorostyrene derivatives in excellent yields. PMID:21322557

  13. Nature and origin of the hydrocarbons in sediments of Lake Constance. Art und Herkunft der Kohlenwasserstoffe in Sedimenten des Bodensees

    Energy Technology Data Exchange (ETDEWEB)

    Giger, W.; Schaffner, C.; Hollerbach, A.; Kalbfus, W.; Wachs, B.; Wagner, H.; Mueller, G.; Mueller, H.

    1982-04-01

    Six samples of sediment were taken from Lake Constance and hydrocarbons tested for biogenic or mineral oil origin with the following results: The high proportion of polar extractable matter is indicative of a biogenic origin. 2. The alkanes and alkenes are largely of biogenic composition, whereby an indication of fossile hydrocarbons was found for two samples. A distribution could not be made between mineral oil-derived hydrocarbons and other fossile hydrocarbons because of the low proportions present. 3. The composition of the aromatic fraction was indicative of a biogenic or pyrolytic origin.

  14. Impact of pollution controls in Beijing on atmospheric oxygenated volatile organic compounds (OVOCs) during the 2008 Olympic Games: observation and modeling implications

    Science.gov (United States)

    Liu, Y.; Yuan, B.; Li, X.; Shao, M.; Lu, S.; Li, Y.; Chang, C.-C.; Wang, Z.; Hu, W.; Huang, X.; He, L.; Zeng, L.; Hu, M.; Zhu, T.

    2015-03-01

    Oxygenated volatile organic compounds (OVOCs) are important products of the photo-oxidation of hydrocarbons. They influence the oxidizing capacity and the ozone-forming potential of the atmosphere. In the summer of 2008, 2 months of emission restrictions were enforced in Beijing to improve air quality during the Olympic Games. Observational evidence reported in related studies that these control measures were efficient in reducing the concentrations of primary anthropogenic pollutants (CO, NOx and non-methane hydrocarbons, i.e., NMHCs) by 30-40%. In this study, the influence of the emission restrictions on ambient levels of OVOCs was explored using a neural network analysis with consideration of meteorological conditions. Statistically significant reductions in formaldehyde (HCHO), acetaldehyde (CH3CHO), methyl ethyl ketone (MEK) and methanol were found to be 12.9, 15.8, 17.1 and 19.6%, respectively, when the restrictions were in place. The effect of emission controls on acetone was not detected in neural network simulations, probably due to pollution transport from surrounding areas outside Beijing. Although the ambient levels of most NMHCs were reduced by ~35% during the full control period, the emission ratios of reactive alkenes and aromatics closely related to automobile sources did not present much difference (< 30%). A zero-dimensional box model based on the Master Chemical Mechanism version 3.2 (MCM3.2) was applied to evaluate how OVOC production responds to the reduced precursors during the emissions control period. On average, secondary HCHO was produced from the oxidation of anthropogenic alkenes (54%), isoprene (30%) and aromatics (15%). The importance of biogenic sources for the total HCHO formation was almost on par with that of anthropogenic alkenes during the daytime. Anthropogenic alkenes and alkanes dominated the photochemical production of other OVOCs such as acetaldehyde, acetone and MEK. The relative changes of modeled HCHO, CH3CHO, methyl

  15. Application of 7-azaisatins in enantioselective Morita–Baylis–Hillman reaction

    Science.gov (United States)

    He, Qing; Zhan, Gu; Du, Wei

    2016-01-01

    Summary 7-Azaisatin and 7-azaoxindole skeletons are valuable building blocks in diverse biologically active substances. Here 7-azaisatins turned out to be more efficient electrophiles than the analogous isatins in the enantioselective Morita–Baylis–Hillman (MBH) reactions with maleimides using a bifunctional tertiary amine, β-isocupreidine (β-ICD), as the catalyst. This route allows a convenient approach to access multifunctional 3-hydroxy-7-aza-2-oxindoles with high enantiopurity (up to 94% ee). Other types of activated alkenes, such as acrylates and acrolein, could also be efficiently utilized. PMID:26977190

  16. An efficient and general route to reduced polypropionates via Zr-catalyzed asymmetric C—C bond formation

    OpenAIRE

    Negishi, Ei-ichi; Tan, Ze; Liang, Bo; Novak, Tibor

    2004-01-01

    An efficient and general method for the synthesis of reduced polypropionates has been developed through the application of asymmetric carboalumination of alkenes catalyzed by dichlorobis(1-neomenthylindenyl)zirconium [(NMI)2ZrCl2]. In this investigation, attention has been focused on those reduced polypropionates that are α-monoheterofunctional and either ω-ethyl or ω-n-propyl. The reaction of 3-buten-1-ol with triethylaluminum (Et3Al) or tripropylaluminum (nPr3Al) in the presence of (NMI)2Zr...

  17. Omsetning av metylklorid til hydrokarboner over H-SAPO-34 og H-SSZ-13

    OpenAIRE

    2009-01-01

    Metylklorid-til-hydrokarboner (MeXTH)-prosessen er et trinn i oppgraderingen av naturgass til alkener. Prosessen unngår produksjon av syntesegass som er en energikrevende prosess. I dette arbeidet sammenlignes to mikroporøse katalysatorer til MeXTH-prosessen, zeolitten H-SSZ-13 og zeotypen H-SAPO-34. Begge katalysatorene har CHA-topologien, men har ulik syrestyrke på grunn av forskjellig nettverkskomposisjon. Katalysatorene ble testet i en stasjonær-sjikt-reaktor, og reaksjonstemperaturen...

  18. Radiolysis of saturated phospholipids. [/sup 60/Co

    Energy Technology Data Exchange (ETDEWEB)

    Handel, A.P.; Nawar, W.W.

    1981-06-01

    Volatile radiolysis products of 1,2-dipalmitoyl-sn-glycerol-3-phosphoethanolamine were recovered by cold-finger distillation and analyzed by gas chromatogrphy and mass spectrometry. They include series of n-alkanes, 1-alkenes, n-alkanals, 2-alkanones, 3-alkanones, 4-alkanones, and methyl and ethyl esters. Quantitative analysis showed that the amounts of products from irradiated 3-sn-phosphatidylethanolamine were strikingly different from those recovered from the acylglycerols. Nonvolatile radiolytic products were separated by thin-layer chromatography. These included palmitic acid, palmitone, lysophosphatidylethanolamine, ethanolamine phosphate, and five unidentified compounds. Possible mechanisms for the formation of these compounds are discussed.

  19. Synthesis and Application of Zeolite-encapsulated Nickel Schiff-base Complex

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    @@ Transition-metal complex-catalyzed oxidation of organic substrates with molecular oxygen is gaining importance as a viable alternative to the environmentally hazardous metal-oxide-based reagents. The complexes have received much attention recently due to the potential application of these complexes as oxidation catalysts for the oxidation of alkene, enolizable, aldehydes and other organic substrates. Recent studies of our group showed that metal complexes catalyzed the oxidation of organic substrates selectively in the presence of molecular oxygen 1,5. Here, it is reported that zeolite-encapsulated Ni (I) Schiff-base complex exhibit a catalytic activity and selectivity for the oxidation of styrene.

  20. Modern Arylation Methods

    CERN Document Server

    Ackermann, Lutz

    2009-01-01

    Today, arylation methods are belonging to the most important reaction types in organic synthesis. Lutz Ackermann, a young and ambitious professor has gathered a number of top international authors to present the first comprehensive book on the topic. Starting from a historical review, the book covers hot topics like Palladium-catalyzed arylation of N-H and alpha-C-H-acidic Bonds, Copper-catalyzed arylation of N-H and O-H Bonds, direct arylation reactions, carbanion aromatic synthesis, arylation reactions of alkenes, alkynes and much more. This compact source of high quality information is indi