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Sample records for chiral olefin metathesis

  1. Olefin metathesis and metathesis polymerization

    CERN Document Server

    Ivin, K J

    1997-01-01

    This book is a follow-up to Ivins Olefin Metathesis, (Academic Press, 1983). Bringing the standard text in the field up to date, this Second Edition is a result of rapid growth in the field, sparked by the discovery of numerous well-defined metal carbene complexes that can act as very efficient initiators of all types of olefin metathesis reaction, including ring-closing metathesis of acyclic dienes, enynes, and dienynes; ring-opening metathesis polymerizationof cycloalkenes, acyclic diene metathesis polymerization; and polymerization of alkynes, as well as simple olefin metathesis. Olefin Metathesis and Metathesis Polymerization provides a broad, up-to-date account of the subject from its beginnings in 1957 to the latest applications in organic synthesis. The book follows the same format as the original, making it useful toteachers and to researchers, and will be of particular interest to those working in the fields of organic chemistry, polymer chemistry, organometallic chemistry, catalysis, materials scien...

  2. Olefin metathesis in air

    Directory of Open Access Journals (Sweden)

    Lorenzo Piola

    2015-10-01

    Full Text Available Since the discovery and now widespread use of olefin metathesis, the evolution of metathesis catalysts towards air stability has become an area of significant interest. In this fascinating area of study, beginning with early systems making use of high oxidation state early transition metal centers that required strict exclusion of water and air, advances have been made to render catalysts more stable and yet more functional group tolerant. This review summarizes the major developments concerning catalytic systems directed towards water and air tolerance.

  3. Olefin metathesis in nano-sized systems

    Directory of Open Access Journals (Sweden)

    Denise Méry

    2011-01-01

    Full Text Available The interplay between olefin metathesis and dendrimers and other nano systems is addressed in this mini review mostly based on the authors’ own contributions over the last decade. Two subjects are presented and discussed: (i The catalysis of olefin metathesis by dendritic nano-catalysts via either covalent attachment (ROMP or, more usefully, dendrimer encapsulation – ring closing metathesis (RCM, cross metathesis (CM, enyne metathesis reactions (EYM – for reactions in water without a co-solvent and (ii construction and functionalization of dendrimers by CM reactions.

  4. Olefin Metathesis in Peptidomimetics, Dynamic Combinatorial Chemistry, and Molecular Imprinting

    National Research Council Canada - National Science Library

    Low, Tammy K

    2006-01-01

    .... Our research goals consisted of employing olefin metathesis in the synthesis of peptidomimetics, and studying the feasibility of this method in dynamic combinatorial chemistry and molecular imprinting of nerve agents...

  5. Synthesis of interlocked molecules by olefin metathesis

    Science.gov (United States)

    Clark, Paul Gregory

    A large body of work in the Grubbs group has focused on the development of functional-group tolerant ruthenium alkylidene catalysts that perform a number of olefin metathesis reactions. These catalysts have seen application in a wide range of fields, including classic total synthesis as well as polymer and materials chemistry. One particular family of compounds, interlocked molecules, has benefitted greatly from these advances in catalyst stability and activity. This thesis describes several elusive and challenging interlocked architectures whose syntheses have been realized through the utilization of different types of ruthenium-catalyzed olefin metathesis reactions. Ring-closing olefin metathesis has enabled the synthesis of a [c2]daisy-chain dimer with the ammonium binding site near the cap of the dimer. A deprotonated DCD possessing such a structural attribute will more forcefully seek to restore coordinating interactions upon reprotonation, enhancing its utility as a synthetic molecular actuator. Dimer functionalization facilitated incorporation into linear polymers, with a 48% size increase of an unbound, extended analogue of the polymer demonstrating slippage of the dimer units. Ongoing work is directed at further materials studies, in particular, exploring the synthesis of macroscopic networks containing the DCD units and analyzing the correlation between molecular-scale extension-contraction manipulations and resulting macro-scale changes. A "clipping" approach to a polycatenated cyclic polymer, a structure that resembles a molecular "charm bracelet", has been described. The use of ring-opening metathesis polymerization of a carbamate monomer in the presence of a chain transfer agent allowed for the synthesis of a linear polymer that was subsequently functionalized and cyclized to the corresponding cyclic analogue. This cyclic polymer was characterized through a variety of techniques, and subjected to further functionalization reactions, affording a cyclic

  6. The activation mechanism of Fe-based olefin metathesis catalysts

    KAUST Repository

    Poater, Albert

    2014-08-01

    Density functional theory calculations have been used to describe the first turnover for olefin metathesis reaction of a homogenous Fe-based catalyst bearing a N-heterocyclic carbene ligand with methoxyethene as a substrate. Equal to conventional Ru-based catalysts, the activation of its Fe congener occurs through a dissociative mechanism, however with a more exothermic reaction energy profile. Predicted upper energy barriers were calculated to be on average ∼2 kcal/mol more beneficial for Fe catalyzed metathesis. Overall, this present computational study emphasises on advantages of Fe-based metathesis and gives a potential recipe for the design of an efficient Fe-based olefin metathesis catalysts. © 2014 Elsevier B.V.

  7. The activation mechanism of Fe-based olefin metathesis catalysts

    KAUST Repository

    Poater, Albert; Pump, Eva; Vummaleti, Sai V. C.; Cavallo, Luigi

    2014-01-01

    Density functional theory calculations have been used to describe the first turnover for olefin metathesis reaction of a homogenous Fe-based catalyst bearing a N-heterocyclic carbene ligand with methoxyethene as a substrate. Equal to conventional Ru-based catalysts, the activation of its Fe congener occurs through a dissociative mechanism, however with a more exothermic reaction energy profile. Predicted upper energy barriers were calculated to be on average ∼2 kcal/mol more beneficial for Fe catalyzed metathesis. Overall, this present computational study emphasises on advantages of Fe-based metathesis and gives a potential recipe for the design of an efficient Fe-based olefin metathesis catalysts. © 2014 Elsevier B.V.

  8. The olefin metathesis reaction: reorganization and cyclization of organic compounds

    International Nuclear Information System (INIS)

    Frederico, Daniel; Brocksom, Ursula; Brocksom, Timothy John

    2005-01-01

    The olefin metathesis reaction allows the exchange of complex alkyl units between two olefins, with the formation of a new olefinic link and a sub-product olefin usually ethylene. This reaction has found extensive application in the last ten years with the development of the Grubbs and Schrock catalysts, in total synthesis of complex organic molecules, as opposed to the very important use in the petrochemical industry with relatively simple molecules. This review intends to trace a historical and mechanistic pathway from industry to academy, before illustrating the more recent advances. (author)

  9. Comparing Ru and Fe-catalyzed olefin metathesis

    KAUST Repository

    Poater, Albert; Chaitanya Vummaleti, Sai Vikrama; Pump, Eva; Cavallo, Luigi

    2014-01-01

    Density functional theory calculations have been used to explore the potential of Fe-based complexes with an N-heterocyclic carbene ligand, as olefin metathesis catalysts. Apart from a less endothermic reaction energy profile, a small reduction in the predicted upper energy barriers (≈ 2 kcal mol -1) is calculated in the Fe catalyzed profile with respect to the Ru catalysed profile. Overall, this study indicates that Fe-based catalysts have the potential to be very effective olefin metathesis catalysts. This journal is © the Partner Organisations 2014.

  10. The asymmetric Schrock olefin metathesis catalysts. A computational study

    NARCIS (Netherlands)

    Goumans, T.P.M.; Ehlers, A.W.; Lammertsma, K.

    2005-01-01

    The mechanism of the transition metal catalyzed olefin metathesis reaction with the Schrock catalyst is investigated with pure (BP86) and hybrid (B3LYP) density functional theory. On the free-energy surface there is no adduct between ethylene and model catalyst (MeO)

  11. Mesoporous molecular sieves as advanced supports for olefin metathesis catalysts

    Czech Academy of Sciences Publication Activity Database

    Balcar, Hynek; Čejka, Jiří

    2013-01-01

    Roč. 257, 21-22 (2013), s. 3107-3124 ISSN 0010-8545 R&D Projects: GA AV ČR IAA400400805; GA ČR GBP106/12/G015 Institutional support: RVO:61388955 Keywords : Olefin metathesis * mesoporous molecular sieves * Heterogeneous catalysts Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 12.098, year: 2013

  12. A latent ruthenium based olefin metathesis catalyst with a sterically demanding NHC ligand

    KAUST Repository

    Leitgeb, Anita; Abbas, Mudassar E.; Fischer, Roland C.; Poater, Albert; Cavallo, Luigi; Slugovc, Christian

    2012-01-01

    An olefin metathesis catalyst featuring a SIPr NHC and an ester chelating carbene ligand is introduced. In contrast to its previously published SIMes analogue, only the trans dichloro configurated isomer was obtained. The two counterparts are tested in various olefin metathesis reactions, revealing a striking superiority of the new complex in the cross metathesis of olefins with methyl vinyl ketone allowing for full conversion with only 500 ppm catalyst loading. © 2012 The Royal Society of Chemistry.

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

    Science.gov (United States)

    Schrodi, Yann [Agoura Hills, CA

    2011-11-29

    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. NATO Advanced Study Institute on Ring-opening Metathesis Polymerization of Olefins and Polymerization of Alkynes

    CERN Document Server

    1998-01-01

    The first NATO Advanced Study Institute on Olefin Metathesis and Polymerization Catalysts was held on September 10-22, 1989 in Akcay, Turkey. Based on the fundamental research of RRSchrock, RGrubbs and K.B.Wagener in the field of ring opening metathesis polymerization (ROMP), acyclic diene metathesis (ADMET) and alkyne polymerization, these areas gained growing interest within the last years. Therefore the second NATO-ASI held on metathesis reactions was on Ring Opening Metathesis Po­ lymerization of Olefins and Polymerization of Alkynes on September 3-16, 1995 in Akcay, Turkey. The course joined inorganic, organic and polymer chemists to exchange their knowledge in this field. This volume contains the main and short lectures held in Akcay. To include ADMET reactions better into the title of this volume we changed it into: Metathesis Polymerization of Olefins and Alkyne Polymerization. This volume is addressed to research scientists, but also to those who start to work in the area of olefin metathesis and al...

  15. Synthesis of the EF-ring of ciguatoxin 3C based on the [2,3]-Wittig rearrangement and ring-closing olefin metathesis.

    Science.gov (United States)

    Goto, Akiyoshi; Fujiwara, Kenshu; Kawai, Ayako; Kawai, Hidetoshi; Suzuki, Takanori

    2007-12-20

    The EF-ring segment of ciguatoxin 3C, a causative toxin of ciguatera fish poisoning, was synthesized in three major steps: 1,4-addition for the C20O-C27 bond connection, chirality transferring anti selective [2,3]-Wittig rearrangement for the construction of the anti-2-hydroxyalkyl ether part, and ring-closing olefin metathesis for the F-ring formation.

  16. The right computational recipe for olefin metathesis with ru-based catalysts: The whole mechanism of ring-closing olefin metathesis

    KAUST Repository

    Poater, Albert

    2014-10-14

    The initiation mechanism of ruthenium methylidene complexes was studied detailing mechanistic insights of all involved reaction steps within a classical olefin metathesis pathway. Computational studies reached a good agreement with the rarely available experimental data and even enabled to complement them. As a result, a highly accurate computational and rather cheap recipe is presented; M06/TZVP//BP86/SVP (PCM, P = 1354 atm).

  17. The right computational recipe for olefin metathesis with ru-based catalysts: The whole mechanism of ring-closing olefin metathesis

    KAUST Repository

    Poater, Albert; Pump, Eva; Vummaleti, Sai V. C.; Cavallo, Luigi

    2014-01-01

    The initiation mechanism of ruthenium methylidene complexes was studied detailing mechanistic insights of all involved reaction steps within a classical olefin metathesis pathway. Computational studies reached a good agreement with the rarely available experimental data and even enabled to complement them. As a result, a highly accurate computational and rather cheap recipe is presented; M06/TZVP//BP86/SVP (PCM, P = 1354 atm).

  18. Ru-Based Complexes with Quaternary Ammonium Tags Immobilized on Mesoporous Silica as Olefin Metathesis Catalysts

    Czech Academy of Sciences Publication Activity Database

    Pastva, Jakub; Skowerski, K.; Czarnocki, S. J.; Žilková, Naděžda; Čejka, Jiří; Bastl, Zdeněk; Balcar, Hynek

    2014-01-01

    Roč. 4, č. 9 (2014), s. 3227-3236 ISSN 2155-5435 R&D Projects: GA ČR(CZ) GAP106/12/0189 Institutional support: RVO:61388955 Keywords : olefin metathesis * heterogeneous catalysts * mesoporous molecular sieves Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 9.312, year: 2014

  19. Omega-functionalized fatty acids, alcohols, and ethers via olefin metathesis

    Science.gov (United States)

    Methyl 17-hydroxy stearate was converted to methyl octadec-16-enoate using copper sulfate adsorbed on silica gel. This compound, possessing unsaturation at the opposite end of the chain from the carboxylate, served as a useful substrate for the olefin metathesis reaction. As a result, several fatt...

  20. Synthesis of 7-Deoxypancratistatin from Carbohydrates by the Use of Olefin Metathesis

    DEFF Research Database (Denmark)

    Håkansson, Anders Eckart; Palmelund, Anders; Holm, H.

    2006-01-01

    from D-xylose and piperonal. The former is converted into ribofuranoside 28, which is coupled with bromide 7 in the presence of zinc, and this is followed by ring-closing olefin metathesis. Subsequent Overman rearrangement, dihydroxylation, and deprotection then affords the natural product....

  1. Selective Metathesis of α-Olefins from Bio-Sourced Fischer–Tropsch Feeds

    KAUST Repository

    Rouen, Mathieu; Queval, Pierre; Borre, Etienne; Falivene, Laura; Poater, Albert; Berthod, Mikael; Hugues, Francois; Cavallo, Luigi; Basle, Olivier; Olivier-Bourbigou, Helene; Mauduit, Marc

    2016-01-01

    The search for a low-cost process for the valorization of linear alpha-olefins combining high productivity and high selectivity is a longstanding goal for chemists. Herein, we report a soluble ruthenium olefin metathesis catalyst that performs the conversion of linear alpha-olefins to longer internal linear olefins with high selectivity (>99%) under neat conditions at low loadings (50 ppm) and without the need of expensive additives. This robust catalytic process allowed us to efficiently and selectively re-equilibrate the naphtha fraction (C-5-C-8) of a Fischer-Tropsch feed derived from non petroleum resources to a higher-value product range (C-9-C-14), useful as detergent and plasticizer precursors.

  2. Selective Metathesis of α-Olefins from Bio-Sourced Fischer–Tropsch Feeds

    KAUST Repository

    Rouen, Mathieu

    2016-10-14

    The search for a low-cost process for the valorization of linear alpha-olefins combining high productivity and high selectivity is a longstanding goal for chemists. Herein, we report a soluble ruthenium olefin metathesis catalyst that performs the conversion of linear alpha-olefins to longer internal linear olefins with high selectivity (>99%) under neat conditions at low loadings (50 ppm) and without the need of expensive additives. This robust catalytic process allowed us to efficiently and selectively re-equilibrate the naphtha fraction (C-5-C-8) of a Fischer-Tropsch feed derived from non petroleum resources to a higher-value product range (C-9-C-14), useful as detergent and plasticizer precursors.

  3. Exploring new generations of ruthenium olefin metathesis catalysts: The reactivity of a bis-ylidene ruthenium complex by DFT

    KAUST Repository

    Poater, Albert; Credendino, Raffaele; Slugovc, Christian; Cavallo, Luigi

    2013-01-01

    Density functional theory calculations were used to predict the behaviour of a potential novel architecture of olefin metathesis catalysts, in which one of the neutral ligands of classical Ru-based catalysts, e.g. a phosphine or an N-heterocyclic carbene, is replaced by an alkylidene group. Introduction of a second alkylidene ligand favors dissociation of the remaining phosphine and the overall energy profile for the metathesis using ethylene as the probe substrate reveals that the proposed bis-alkylidene complexes might match the requirements of a good performing olefin metathesis catalyst. © 2013 The Royal Society of Chemistry.

  4. 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.

  5. Cis/trans Coordination in olefin metathesis by static and molecular dynamic DFT calculations

    KAUST Repository

    Poater, Albert; Correa, Andrea; Pump, Eva; Cavallo, Luigi

    2014-01-01

    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.

  6. Olefin Metathesis in Peptidomimetics, Dynamic Combinatorial Chemistry, and Molecular Imprinting

    Science.gov (United States)

    2006-08-01

    organic, and biochemistry, lectured in chemistry of weapons, and researched on ionic liquids and nucleic acid derivatives. She discovered her joy of...Products from oligomerization of the dimer scaffold or olefin isomerization are excluded from these projected numbers.97,98 The number of...Figure 3-8). This is excluding any olefin isomerization products or oligomerization of the cyclic scaffold. If stereoisomers are considered, then

  7. The activation mechanism of Ru-indenylidene complexes in olefin metathesis

    KAUST Repository

    Urbina-Blanco, César A.

    2013-05-08

    Olefin metathesis is a powerful tool for the formation of carbon-carbon double bonds. Several families of well-defined ruthenium (Ru) catalysts have been developed during the past 20 years; however, the reaction mechanism for all such complexes was assumed to be the same. In the present study, the initiation mechanism of Ru-indenylidene complexes was examined and compared with that of benzylidene counterparts. It was discovered that not all indenylidene complexes followed the same mechanism, highlighting the importance of steric and electronic properties of so-called spectator ligands, and that there is no single mechanism for the Ru-based olefin metathesis reaction. The experimental findings are supported quantitatively by DFT calculations. © 2013 American Chemical Society.

  8. The activation mechanism of Ru-indenylidene complexes in olefin metathesis

    KAUST Repository

    Urbina-Blanco, Cé sar A.; Poater, Albert; Lé bl, Tomá š; Manzini, Simone; Slawin, Alexandra M. Z.; Cavallo, Luigi; Nolan, Steven P.

    2013-01-01

    Olefin metathesis is a powerful tool for the formation of carbon-carbon double bonds. Several families of well-defined ruthenium (Ru) catalysts have been developed during the past 20 years; however, the reaction mechanism for all such complexes was assumed to be the same. In the present study, the initiation mechanism of Ru-indenylidene complexes was examined and compared with that of benzylidene counterparts. It was discovered that not all indenylidene complexes followed the same mechanism, highlighting the importance of steric and electronic properties of so-called spectator ligands, and that there is no single mechanism for the Ru-based olefin metathesis reaction. The experimental findings are supported quantitatively by DFT calculations. © 2013 American Chemical Society.

  9. The generation of efficient supported (Heterogeneous) olefin metathesis catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Grubbs, Robert H

    2013-04-05

    Over the past decade, a new family of homogeneous metathesis catalysts has been developed that will tolerate most organic functionalities as well as water and air. These homogeneous catalysts are finding numerous applications in the pharmaceutical industry as well as in the production of functional polymers. In addition the catalysts are being used to convert seed oils into products that can substitute for those that are now made from petroleum products. Seed oils are unsaturated, contain double bonds, and are a ready source of linear hydrocarbon fragments that are specifically functionalized. To increase the number of applications in the area of biomaterial conversion to petrol chemicals, the activity and efficiency of the catalysts need to be as high as possible. The higher the efficiency of the catalysts, the lower the cost of the conversion and a larger number of practical applications become available. Active supported catalysts were prepared and tested in the conversion of seed oils and other important starting materials. The outcome of the work was successful and the technology has been transferred to a commercial operation to develop viable applications of the discovered systems. A biorefinery that converts seed oils is under construction in Indonesia. The catalysts developed in this study will be considered for the next generation of operations.

  10. Energetics of the ruthenium-halide bond in olefin metathesis (pre)catalysts

    KAUST Repository

    Falivene, Laura; Poater, Albert; Cazin, Catherine S J; Slugovc, Christian; Cavallo, Luigi

    2013-01-01

    A DFT analysis of the strength of the Ru-halide bond in a series of typical olefin metathesis (pre)catalysts is presented. The calculated Ru-halide bond energies span the rather broad window of 25-43 kcal mol-1. This indicates that in many systems dissociation of the Ru-halide bond is possible and is actually competitive with dissociation of the labile ligand generating the 14e active species. Consequently, formation of cationic Ru species in solution should be considered as a possible event. © 2013 The Royal Society of Chemistry.

  11. Synthesis of amide-functionalized cellulose esters by olefin cross-metathesis.

    Science.gov (United States)

    Meng, Xiangtao; Edgar, Kevin J

    2015-11-05

    Cellulose esters with amide functionalities were synthesized by cross-metathesis (CM) reaction of terminally olefinic esters with different acrylamides, catalyzed by Hoveyda-Grubbs 2nd generation catalyst. Chelation by amides of the catalyst ruthenium center caused low conversions using conventional solvents. The effects of both solvent and structure of acrylamide on reaction conversion were investigated. While the inherent tendency of acrylamides to chelate Ru is governed by the acrylamide N-substituents, employing acetic acid as a solvent significantly improved the conversion of certain acrylamides, from 50% to up to 99%. Homogeneous hydrogenation using p-toluenesulfonyl hydrazide successfully eliminated the α,β-unsaturation of the CM products to give stable amide-functionalized cellulose esters. The amide-functionalized product showed higher Tg than its starting terminally olefinic counterpart, which may have resulted from strong hydrogen bonding interactions of the amide functional groups. Copyright © 2015 Elsevier Ltd. All rights reserved.

  12. SOMC-Designed Silica Supported Tungsten Oxo Imidazolin-2-iminato Methyl Precatalyst for Olefin Metathesis Reactions

    KAUST Repository

    Qureshi, Ziyauddin

    2017-01-05

    Synthesis, structure, and olefin metathesis activity of a surface complex [(≡Si-O-)W(═O)(CH3)2-ImDippN] (4) (ImDipp = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-iminato) supported on silica by a surface organometallic chemistry (SOMC) approach are reported. The reaction of N-silylated 2-iminoimidazoline with tungsten(VI) oxytetrachloride generated the tungsten oxo imidazolin-2-iminato chloride complex [ImDippNW(═O)Cl3] (2). This was grafted on partially dehydroxylated silica pretreated at 700 °C (SiO2-700) to afford a well-defined monopodal surface complex [(≡Si-O-)W(═O)Cl2-ImDippN] (3). 3 underwent alkylation by ZnMe2 to produce [(≡Si-O-)W(═O)(CH3)2-ImDippN] (4). The alkylated surface complex was thoroughly characterized by solid-state NMR, elemental microanalysis, Raman, FT-IR spectroscopies, and XAS analysis. 4 proved to be an active precatalyst for self-metathesis of terminal olefins such as propylene and 1-hexene.

  13. SOMC-Designed Silica Supported Tungsten Oxo Imidazolin-2-iminato Methyl Precatalyst for Olefin Metathesis Reactions

    KAUST Repository

    Qureshi, Ziyauddin; Hamieh, Ali Imad Ali; Barman, Samir; Maity, Niladri; Samantaray, Manoja; Ould-Chikh, Samy; Abou-Hamad, Edy; Falivene, Laura; D’ Elia, Valerio; Rothenberger, Alexander; Llorens, Isabelle; Hazemann, Jean-Louis; Basset, Jean-Marie

    2017-01-01

    Synthesis, structure, and olefin metathesis activity of a surface complex [(≡Si-O-)W(═O)(CH3)2-ImDippN] (4) (ImDipp = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-iminato) supported on silica by a surface organometallic chemistry (SOMC) approach are reported. The reaction of N-silylated 2-iminoimidazoline with tungsten(VI) oxytetrachloride generated the tungsten oxo imidazolin-2-iminato chloride complex [ImDippNW(═O)Cl3] (2). This was grafted on partially dehydroxylated silica pretreated at 700 °C (SiO2-700) to afford a well-defined monopodal surface complex [(≡Si-O-)W(═O)Cl2-ImDippN] (3). 3 underwent alkylation by ZnMe2 to produce [(≡Si-O-)W(═O)(CH3)2-ImDippN] (4). The alkylated surface complex was thoroughly characterized by solid-state NMR, elemental microanalysis, Raman, FT-IR spectroscopies, and XAS analysis. 4 proved to be an active precatalyst for self-metathesis of terminal olefins such as propylene and 1-hexene.

  14. Striking difference between alkane and olefin metathesis using the well-defined precursor [≡Si-O-WMe5]: Indirect evidence in favour of a bifunctional catalyst W alkylidene-hydride

    KAUST Repository

    Riache, Nassima; Callens, Emmanuel; Espinas, Jeff; Dé ry, Alexandre; Samantaray, Manoja; Dey, Raju; Basset, Jean-Marie

    2015-01-01

    Metathesis of linear alkanes catalyzed by the well-defined precursor (≡Si-O-WMe5) affords a wide distribution of linear alkanes from methane up to triacontane. Olefin metathesis using the same catalyst and under the same reaction conditions gives a very striking different distribution of linear α-olefins and internal olefins. This shows that olefin and alkane metathesis processes occur via very different pathways.

  15. Efficient synthesis of enantiopure conduritols by ring-closing metathesis

    DEFF Research Database (Denmark)

    Jørgensen, Morten; Iversen, Erik Høgh; Paulsen, Andreas Lundtang

    2001-01-01

    Two short synthetic approaches to enantiopure conduritols are described starting from the chiral pool. In both cases, the cyclohexene ring is assembled via ring-closing olefin metathesis. The terminal diene precursers for the metathesis reaction are prepared either from octitols or from tartaric...

  16. Consequences of the electronic tuning of latent ruthenium-based olefin metathesis catalysts on their reactivity

    KAUST Repository

    Żukowska, Karolina

    2015-08-20

    Two ruthenium olefin metathesis initiators featuring electronically modified quinoline-based chelating carbene ligands are introduced. Their reactivity in RCM and ROMP reactions was tested and the results were compared to those obtained with the parent unsubstituted compound. The studied complexes are very stable at high temperatures up to 140 °C. The placement of an electron-withdrawing functionality translates into an enhanced activity in RCM. While electronically modified precatalysts, which exist predominantly in the trans-dichloro configuration, gave mostly the RCM and a minor amount of the cycloisomerization product, the unmodified congener, which preferentially exists as its cis-dichloro isomer, shows a switched reactivity. The position of the equilibrium between the cis- and the trans-dichloro species was found to be the crucial factor governing the reactivity of the complexes.

  17. Consequences of the electronic tuning of latent ruthenium-based olefin metathesis catalysts on their reactivity

    KAUST Repository

    Żukowska, Karolina; Pump, Eva; Pazio, Aleksandra E; Woźniak, Krzysztof; Cavallo, Luigi; Slugovc, Christian

    2015-01-01

    Two ruthenium olefin metathesis initiators featuring electronically modified quinoline-based chelating carbene ligands are introduced. Their reactivity in RCM and ROMP reactions was tested and the results were compared to those obtained with the parent unsubstituted compound. The studied complexes are very stable at high temperatures up to 140 °C. The placement of an electron-withdrawing functionality translates into an enhanced activity in RCM. While electronically modified precatalysts, which exist predominantly in the trans-dichloro configuration, gave mostly the RCM and a minor amount of the cycloisomerization product, the unmodified congener, which preferentially exists as its cis-dichloro isomer, shows a switched reactivity. The position of the equilibrium between the cis- and the trans-dichloro species was found to be the crucial factor governing the reactivity of the complexes.

  18. Cationic Tungsten(VI) Penta-Methyl Complex: Synthesis, Characterization and its Application in Olefin Metathesis Reaction

    KAUST Repository

    Dey, Raju

    2016-04-13

    Tungsten-hexa-methyl readily reacts with B(C6F5)3 in dichloromethane and generates the corresponding well-defined cationic tungsten-penta-methyl complex which was identified precisely by 1H NMR, 13C NMR, 1H-13C NMR correlation spectroscopy. Unlike WMe6, this cationic complex has low energy barrier to form tungsten carbene intermediate, which was further supported by the fact that WMe6 alone has no activity in olefin metathesis reaction whereas the cationic complex shows catalytic activity for self-metathesis of 1-octene.

  19. Cationic Tungsten(VI) Penta-Methyl Complex: Synthesis, Characterization and its Application in Olefin Metathesis Reaction

    KAUST Repository

    Dey, Raju; Samantaray, Manoja; Callens, Emmanuel; Hamieh, Ali Imad Ali; Emwas, Abdul-Hamid M.; Abou-Hamad, Edy; Kavitake, Santosh Giridhar; Basset, Jean-Marie

    2016-01-01

    Tungsten-hexa-methyl readily reacts with B(C6F5)3 in dichloromethane and generates the corresponding well-defined cationic tungsten-penta-methyl complex which was identified precisely by 1H NMR, 13C NMR, 1H-13C NMR correlation spectroscopy. Unlike WMe6, this cationic complex has low energy barrier to form tungsten carbene intermediate, which was further supported by the fact that WMe6 alone has no activity in olefin metathesis reaction whereas the cationic complex shows catalytic activity for self-metathesis of 1-octene.

  20. In Silico Olefin Metathesis with Ru-Based Catalysts Containing N-Heterocyclic Carbenes Bearing C60Fullerenes

    KAUST Repository

    Martínez, Juan Pablo

    2016-04-10

    Density functional theory calculations have been used to explore the potential of Ru-based complexes with 1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene (SIMes) ligand backbone (A) being modified in silico by the insertion of a C60 molecule (B and C), as olefin metathesis catalysts. To this end, we investigated the olefin metathesis reaction catalyzed by complexes A, B, and C using ethylene as the substrate, focusing mainly on the thermodynamic stability of all possible reaction intermediates. Our results suggest that complex B bearing an electron-withdrawing N-heterocyclic carbene improves the performance of unannulated complex A. The efficiency of complex B is only surpassed by complex A when the backbone of the N-heterocyclic carbene of complex A is substituted by two amino groups. The particular performance of complexes B and C has to be attributed to electronic factors, that is, the electronic-donating capacity of modified SIMes ligand rather than steric effects, because the latter are predicted to be almost identical for complexes B and C when compared to those of A. Overall, this study indicates that such Ru-based complexes B and C might have the potential to be effective olefin metathesis catalysts. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. In Silico Olefin Metathesis with Ru-Based Catalysts Containing N-Heterocyclic Carbenes Bearing C60Fullerenes

    KAUST Repository

    Martí nez, Juan Pablo; Vummaleti, Sai V. C.; Falivene, Laura; Nolan, Steven P.; Cavallo, Luigi; Solà , Miquel; Poater, Albert

    2016-01-01

    Density functional theory calculations have been used to explore the potential of Ru-based complexes with 1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene (SIMes) ligand backbone (A) being modified in silico by the insertion of a C60 molecule (B and C), as olefin metathesis catalysts. To this end, we investigated the olefin metathesis reaction catalyzed by complexes A, B, and C using ethylene as the substrate, focusing mainly on the thermodynamic stability of all possible reaction intermediates. Our results suggest that complex B bearing an electron-withdrawing N-heterocyclic carbene improves the performance of unannulated complex A. The efficiency of complex B is only surpassed by complex A when the backbone of the N-heterocyclic carbene of complex A is substituted by two amino groups. The particular performance of complexes B and C has to be attributed to electronic factors, that is, the electronic-donating capacity of modified SIMes ligand rather than steric effects, because the latter are predicted to be almost identical for complexes B and C when compared to those of A. Overall, this study indicates that such Ru-based complexes B and C might have the potential to be effective olefin metathesis catalysts. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Well-Defined Molybdenum Oxo Alkyl Complex Supported on Silica by Surface Organometallic Chemistry: A Highly Active Olefin Metathesis Precatalyst

    KAUST Repository

    Merle, Nicolas; Le Qué mé ner, Fré dé ric; Bouhoute, Yassine; Szeto, Kai C.; De Mallmann, Aimery; Barman, Samir; Samantaray, Manoja; Delevoye, Laurent; Gauvin, Ré gis M.; Taoufik, Mostafa; Basset, Jean-Marie

    2016-01-01

    The well-defined silica-supported molybdenum oxo alkyl species (SiO−)MoO(CH Bu) was selectively prepared by grafting of MoO(CH Bu)Cl onto partially dehydroxylated silica (silica) using the surface organometallic chemistry approach. This surface species was fully characterized by elemental analysis and DRIFT, solid-state NMR, and EXAFS spectroscopy. This new material is related to the active species of industrial supported MoO/SiO olefin metathesis catalysts. It displays very high activity in propene self-metathesis at mild (turnover number = 90 000 after 25 h). Remarkably, its catalytic performance outpaces those of the parent imido derivative and its tungsten oxo analogue.

  3. Well-Defined Molybdenum Oxo Alkyl Complex Supported on Silica by Surface Organometallic Chemistry: A Highly Active Olefin Metathesis Precatalyst

    KAUST Repository

    Merle, Nicolas

    2016-12-05

    The well-defined silica-supported molybdenum oxo alkyl species (SiO−)MoO(CH Bu) was selectively prepared by grafting of MoO(CH Bu)Cl onto partially dehydroxylated silica (silica) using the surface organometallic chemistry approach. This surface species was fully characterized by elemental analysis and DRIFT, solid-state NMR, and EXAFS spectroscopy. This new material is related to the active species of industrial supported MoO/SiO olefin metathesis catalysts. It displays very high activity in propene self-metathesis at mild (turnover number = 90 000 after 25 h). Remarkably, its catalytic performance outpaces those of the parent imido derivative and its tungsten oxo analogue.

  4. Truncated borrelidin analogues: synthesis by sequential cross metathesis/olefination for the southern fragment and biological evaluation.

    Science.gov (United States)

    Gündemir-Durmaz, Tülay; Schmid, Fabian; El Baz, Yana; Häusser, Annette; Schneider, Carmen; Bilitewski, Ursula; Rauhut, Guntram; Garnier, Delphine; Baro, Angelika; Laschat, Sabine

    2016-09-21

    The construction of novel borrelidin analogues is reported in which the northern fragment is truncated to a simple hydroxyundecanecarboxylate and the original cyclopentanecarboxylic acid in the southern fragment is replaced with different six-membered rings. The required precursors were prepared by cross metathesis of the appropriate carbocycle-based homoallylic alcohol with crotonaldehyde followed by HWE olefination of the resulting enal with bromocyanophosphonate. The key aldehyde for intramolecular cross coupling was accessible by oxidation of the hydroxy group of the linked undecanecarboxylate unit. Grignard mediated macrocyclization finally yielded the borrelidin related products. The investigation is complemented by SAR studies and quantum-chemical calculations.

  5. Cycloalkyl-based unsymmetrical unsaturated (U2)-NHC ligands: Flexibility and dissymmetry in ruthenium-catalysed olefin metathesis

    KAUST Repository

    Rouen, Mathieu

    2014-01-01

    Air-stable Ru-indenylidene and Hoveyda-type complexes bearing new unsymmetrical unsaturated N-heterocyclic carbene (U2-NHC) ligands combining a mesityl unit and a flexible cycloalkyl moiety as N-substituents were synthesised. Structural features, chemical stabilities and catalytic profiles in olefin metathesis of this new library of cycloalkyl-based U2-NHC Ru complexes were studied and compared with their unsymmetrical saturated NHC-Ru homologues as well as a set of commercially available Ru-catalysts bearing either symmetrical SIMes or IMes NHC ligands. © 2014 the Partner Organisations.

  6. Synthesis and characterization of a homogeneous and silica supported homoleptic cationic tungsten(vi) methyl complex: application in olefin metathesis

    KAUST Repository

    Dey, Raju

    2016-08-19

    A method for the synthesis of a homogeneous cationic tungsten(VI)penta-methyl complex [(WMe5)(+)(C6F5)(3)BMe-] from neutral tungstenhexamethyl (WMe6) and a silica supported cationic tungstentetramethyl complex [( Si-O-)WMe4+ (C6F5)(3)BMe-] from a neutral silica supported tungstenpentamethyl complex [( Si-O-)WMe5] is described. In both cases a direct demethylation using the B(C6F5)(3) reagent was used. The aforesaid complexes were characterized by liquid or solid state NMR spectroscopy. Interestingly, the homogeneous cationic complex [(WMe5)(+)(C6F5)(3)BMe-] shows moderate activity whereas the supported cationic complex [( Si-O-)WMe4+(C6F5)(3)BMe-] exhibits good activity in olefin metathesis reactions.

  7. Moving from Classical Ru-NHC to Neutral or Charged Rh-NHC Based Catalysts in Olefin Metathesis

    Directory of Open Access Journals (Sweden)

    Albert Poater

    2016-01-01

    Full Text Available Considering the versatility of oxidation states of rhodium together with the successful background of ruthenium-N-heterocyclic carbene based catalysts in olefin metathesis, it is envisaged the exchange of the ruthenium of the latter catalysts by rhodium, bearing an open-shell neutral rhodium center, or a +1 charged one. In the framework of in silico experiments, density functional theory (DFT calculations have been used to plot the first catalytic cycle that as a first step includes the release of the phosphine. DFT is, in this case, the tool that allows the discovery of the less endergonic reaction profile from the precatalytic species for the neutral catalyst with respect to the corresponding ruthenium one; increasing the endergonic character when dealing with the charged system.

  8. Mechanism of the Ru–Allenylidene to Ru–Indenylidene Rearrangement in Ruthenium Precatalysts for Olefin Metathesis

    KAUST Repository

    Pump, Eva

    2015-06-30

    The intramolecular allenylidene RuCl2(PR3)2(C═C═CPh2) to indenylidene RuCl2(PR3)2(Ind) rearrangement that occurs during the synthesis of Ru-based precatalysts for olefin metathesis is presented. In the absence of acid, the ring closure via C–H activation was shown to be unfavored for energy barriers up to 70 kcal/mol. Thus, it turned out to be HCl (or other acid) that plays a crucial role during formation of the indenylidene, as the upper energy barrier decreases to a reasonable 35 kcal/mol. Moreover, we proved computationally that depending on the nature of the phosphine the intramolecular rearrangement is either facilitated (PPh3) or slightly hampered (PCy3), which is in line with experimental results.

  9. Synthesis and characterization of a homogeneous and silica supported homoleptic cationic tungsten(vi) methyl complex: application in olefin metathesis

    KAUST Repository

    Dey, Raju; Samantaray, Manoja; Poater, Albert; Hamieh, Ali Imad Ali; Kavitake, Santosh Giridhar; Abou-Hamad, Edy; Callens, Emmanuel; Emwas, Abdul-Hamid M.; Cavallo, Luigi; Basset, Jean-Marie

    2016-01-01

    A method for the synthesis of a homogeneous cationic tungsten(VI)penta-methyl complex [(WMe5)(+)(C6F5)(3)BMe-] from neutral tungstenhexamethyl (WMe6) and a silica supported cationic tungstentetramethyl complex [( Si-O-)WMe4+ (C6F5)(3)BMe-] from a neutral silica supported tungstenpentamethyl complex [( Si-O-)WMe5] is described. In both cases a direct demethylation using the B(C6F5)(3) reagent was used. The aforesaid complexes were characterized by liquid or solid state NMR spectroscopy. Interestingly, the homogeneous cationic complex [(WMe5)(+)(C6F5)(3)BMe-] shows moderate activity whereas the supported cationic complex [( Si-O-)WMe4+(C6F5)(3)BMe-] exhibits good activity in olefin metathesis reactions.

  10. Mechanism of the Ru–Allenylidene to Ru–Indenylidene Rearrangement in Ruthenium Precatalysts for Olefin Metathesis

    KAUST Repository

    Pump, Eva; Slugovc, Christian; Cavallo, Luigi; Poater, Albert

    2015-01-01

    The intramolecular allenylidene RuCl2(PR3)2(C═C═CPh2) to indenylidene RuCl2(PR3)2(Ind) rearrangement that occurs during the synthesis of Ru-based precatalysts for olefin metathesis is presented. In the absence of acid, the ring closure via C–H activation was shown to be unfavored for energy barriers up to 70 kcal/mol. Thus, it turned out to be HCl (or other acid) that plays a crucial role during formation of the indenylidene, as the upper energy barrier decreases to a reasonable 35 kcal/mol. Moreover, we proved computationally that depending on the nature of the phosphine the intramolecular rearrangement is either facilitated (PPh3) or slightly hampered (PCy3), which is in line with experimental results.

  11. P(O)R2-Directed Enantioselective C-H Olefination toward Chiral Atropoisomeric Phosphine-Olefin Compounds.

    Science.gov (United States)

    Li, Shi-Xia; Ma, Yan-Na; Yang, Shang-Dong

    2017-04-07

    An effective synthesis of chiral atropoisomeric biaryl phosphine-olefin compounds via palladium-catalyzed enantioselective C-H olefination has been developed for the first time. The reactions are operationally simple, tolerate wide functional groups, and have a good ee value. Notably, P(O)R 2 not only acts as the directing group to direct C-H activation in order to make a useful ligand but also serves to facilitate composition of the product in a useful manner in this transformation.

  12. Olefin Metathesis with Ru-Based Catalysts Exchanging the Typical N-Heterocyclic Carbenes by a Phosphine–Phosphonium Ylide

    Directory of Open Access Journals (Sweden)

    Laia Arnedo

    2017-03-01

    Full Text Available Density functional theory (DFT calculations have been used to describe the first turnover of an olefin metathesis reaction calling for a new in silico family of homogenous Ru-based catalysts bearing a phosphine–phosphonium ylide ligand, with ethylene as a substrate. Equal to conventional Ru-based catalysts bearing an N-heterocyclic carbene (NHC ligand, the activation of these congeners occurs through a dissociative mechanism, with a more exothermic first phosphine dissociation step. In spite of a stronger electron-donating ability of a phosphonium ylide C-ligand with respect to a diaminocarbene analogue, upper energy barriers were calculated to be on average ca. 5 kcal/mol higher than those of Ru–NHC standards. Overall, the study also highlights advantages of bidentate ligands over classical monodentate NHC and phosphine ligands, with a particular preference for the cis attack of the olefin. The new generation of catalysts is constituted by cationic complexes potentially soluble in water, to be compared with the typical neutral Ru–NHC ones.

  13. Synthetic Strategies for Converting Carbohydrates into Carbocycles by the Use of Olefin Metathesis

    DEFF Research Database (Denmark)

    Madsen, Robert

    2007-01-01

    This microreview covers recent advances in the use of ring-closing metathesis for the synthesis of carbocycles from carbohydrates. Various strategies for the synthesis of a,w-dienes from carbohydrates are presented, which give rise to a large variety of dienes with different stereochemistry, prot...

  14. Well-defined silica supported bipodal molybdenum oxo alkyl complexes: a model of the active sites of industrial olefin metathesis catalysts

    KAUST Repository

    Merle, Nicolas

    2017-09-25

    A well-defined, silica-supported molybdenum oxo alkyl species, ([triple bond, length as m-dash]SiO-)2Mo([double bond, length as m-dash]O)(CH2tBu)2, was prepared by the selective grafting of Mo([double bond, length as m-dash]O)(CH2tBu)3Cl onto a silica partially dehydroxylated at 200 °C using a rigorous surface organometallic chemistry approach. The immobilized bipodal surface species, partly resembling the active species of industrial MoO3/SiO2 olefin metathesis catalysts, exhibited excellent functional group tolerance in conjunction with its high activity in homocoupling, self and ring closing olefin metathesis.

  15. Well-defined silica supported bipodal molybdenum oxo alkyl complexes: a model of the active sites of industrial olefin metathesis catalysts

    KAUST Repository

    Merle, Nicolas; Le Qué mé ner, Fré dé ric; Barman, Samir; Samantaray, Manoja; Szeto, Kai C.; De Mallmann, Aimery; Taoufik, Mostafa; Basset, Jean-Marie

    2017-01-01

    A well-defined, silica-supported molybdenum oxo alkyl species, ([triple bond, length as m-dash]SiO-)2Mo([double bond, length as m-dash]O)(CH2tBu)2, was prepared by the selective grafting of Mo([double bond, length as m-dash]O)(CH2tBu)3Cl onto a silica partially dehydroxylated at 200 °C using a rigorous surface organometallic chemistry approach. The immobilized bipodal surface species, partly resembling the active species of industrial MoO3/SiO2 olefin metathesis catalysts, exhibited excellent functional group tolerance in conjunction with its high activity in homocoupling, self and ring closing olefin metathesis.

  16. Hydro-Metathesis of Long-Chain Olefin (1-decene) using Well-Defined Silica-Supported Tungsten (VI), Molybdenum (VI) and Tantalum (V) Catalysts

    KAUST Repository

    Saidi, Aya

    2016-11-01

    Nowadays, catalysis lies at the heart of economy growth mainly in the petroleum industry. Catalysis can offer real and potential solutions to the current challenges for a long-term sustainable energy, green chemistry, and environmental protection. In this context, one of the most important and future prosperity promising catalytic applications in the petrochemical field is hydrocarbons metathesis; it consists on the conversion of both renewable and non-petroleum fossil carbon sources to transportation fuels. Olefin metathesis has become one of the standard methodologies for constructing C-C bonds in many organic transformation reactions. This owed to the numerous types of metathesis reactions that have been developed, for example, enyne, ring-opening and closing, self and cross metathesis, etc. But the one step conversion of olefin to alkanes has not been studied much. Recently, only one such a work has been published for the hydro-metathesis of propylene by tantalum hydride supported on KCC-1 in dynamic reactor. With this knowledge, we thought to study the hydro-metathesis using liquid olefin (1-decene). Another aspect of using 1-decene comes from our previous experience on metathesis of n-decane where the first step is the conversion of decane to 1-decene and subsequently to different chain length alkanes with W-alkyl/alkylidene catalyst. In this way, it would be easy for us to use different catalysts and compare them with parent catalyst concerning TON. We found 100% conversion with TON of 1010 using supported WMe6 onto SiO2-700 [(≡Si-O-)WMe5] against the previous results for n-decane showing 20% conversion and TON of 153. In this work, we disclose the hydro-metathesis reaction of 1-decene using well-defined silica supported W(VI), Mo(VI) and Ta(V) alkyl catalysts in batch reactor condition. This work is divided into three major sections; first chapter contains an introduction to the field of catalysis and surface organometallic chemistry. In second chapter

  17. The metathesis of alkynes

    Directory of Open Access Journals (Sweden)

    H. C. M. Vosloo

    1991-07-01

    Full Text Available The alkyne metathesis reaction is a direct result of the known and intensively studied alkene or olefin metathesis reaction. Unfortunately this reaction was never studied as intensively as the alkene metathesis reaction, mainly because of a lack of active catalytic systems. In the alkyn metathesis reaction the carbon-carbon triple bonds are broken and rearranged to give a redistribution of alkylidyne groups.

  18. From ruthenium olefin metathesis catalyst to (η5-3- phenylindenyl)hydrido complex via alcoholysis

    KAUST Repository

    Manzini, Simone; Nelson, David J.; Lé bl, Tomá š; Poater, Albert; Cavallo, Luigi; Slawin, Alexandra M. Z.; Nolan, Steven P.

    2014-01-01

    The synthesis and characterisation of [Ru(H)(η5-3- phenylindenyl)(iBu-Phoban)2] 4 is reported ( iBu-Phoban = 9-isobutyl-9-phosphabicyclo-[3.3.1]-nonane). 4 is obtained via alcoholysis of metathesis pre-catalyst M11, in a process that was previously thought to be limited to analogous complex [RuCl 2(PPh3)2(3-phenylindenylidene)] (M 10). This journal is © The Royal Society of Chemistry.

  19. A comprehensive study of olefin metathesis catalyzed by Ru-based catalysts

    KAUST Repository

    Poater, Albert

    2015-09-29

    During a Ru-catalyzed reaction of an olefin with an alkylidene moiety that leads to a metallacycle intermediate, the cis insertion of the olefin can occur from two different directions, namely side and bottom with respect to the phosphine or N-heterocyclic ligand (NHC), depending on the first or second generation Grubbs catalyst. Here, DFT calculations unravel to which extent the bottom coordination of olefins with respect is favored over the side coordination through screening a wide range of catalysts, including first and second generation Grubbs catalysts as well as the subsequent Hoveyda derivatives. The equilibrium between bottom and side coordination is influenced by sterics, electronics, and polarity of the solvent. The side attack is favored for sterically less demanding NHC and/or alkylidene ligands. Moreover the generation of a 14-electron species is also discussed, with either pyridine or phosphine ligands to dissociate.

  20. A comprehensive study of olefin metathesis catalyzed by Ru-based catalysts

    KAUST Repository

    Poater, Albert; Cavallo, Luigi

    2015-01-01

    During a Ru-catalyzed reaction of an olefin with an alkylidene moiety that leads to a metallacycle intermediate, the cis insertion of the olefin can occur from two different directions, namely side and bottom with respect to the phosphine or N-heterocyclic ligand (NHC), depending on the first or second generation Grubbs catalyst. Here, DFT calculations unravel to which extent the bottom coordination of olefins with respect is favored over the side coordination through screening a wide range of catalysts, including first and second generation Grubbs catalysts as well as the subsequent Hoveyda derivatives. The equilibrium between bottom and side coordination is influenced by sterics, electronics, and polarity of the solvent. The side attack is favored for sterically less demanding NHC and/or alkylidene ligands. Moreover the generation of a 14-electron species is also discussed, with either pyridine or phosphine ligands to dissociate.

  1. Alkane Metathesis

    KAUST Repository

    Basset, Jean-Marie; Callens, Emmanuel; Riache, Nassima

    2015-01-01

    metal for alkane (de)hydrogenation and another for olefin metathesis in which the activity of these catalysts is essentially driven by the performance of the (de)hydrogenation steps. In this book chapter, we would focus on the evolution of these two

  2. A Silica-Supported Monoalkylated Tungsten Dioxo Complex Catalyst for Olefin Metathesis

    KAUST Repository

    Maity, Niladri

    2018-02-15

    A well-defined silica-supported monoalkylated tungsten dioxo complex [(Si-O-)W(=O)(CH-Bu)] was prepared by treatment of highly dehydroxylated silica (SiO: silica treated at 700 °C under high vacuum) with an ionic precursor complex [NEt][W(=O)(CH-Bu)]. The identity of the resulting neutral monoalkylated tungsten dioxo surface complex was established by means of elemental microanalysis and spectroscopic studies (IR, solid-state NMR, Raman, and X-ray absorption spectroscopies). The supported tungsten complex was found to act as a precatalyst for the self-metathesis of 1-octene in a batch reactor. The mechanistic implications of this reaction are discussed with the support of DFT calculations highlighting the potential occurrence of thus-far unexplored mechanistic pathways.

  3. A Silica-Supported Monoalkylated Tungsten Dioxo Complex Catalyst for Olefin Metathesis

    KAUST Repository

    Maity, Niladri; Barman, Samir; Minenkov, Yury; Ould-Chikh, Samy; Abou-Hamad, Edy; Ma, Tao; Qureshi, Ziyauddin; Cavallo, Luigi; D'Elia, Valerio; Gates, Bruce C.; Basset, Jean-Marie

    2018-01-01

    A well-defined silica-supported monoalkylated tungsten dioxo complex [(Si-O-)W(=O)(CH-Bu)] was prepared by treatment of highly dehydroxylated silica (SiO: silica treated at 700 °C under high vacuum) with an ionic precursor complex [NEt][W(=O)(CH-Bu)]. The identity of the resulting neutral monoalkylated tungsten dioxo surface complex was established by means of elemental microanalysis and spectroscopic studies (IR, solid-state NMR, Raman, and X-ray absorption spectroscopies). The supported tungsten complex was found to act as a precatalyst for the self-metathesis of 1-octene in a batch reactor. The mechanistic implications of this reaction are discussed with the support of DFT calculations highlighting the potential occurrence of thus-far unexplored mechanistic pathways.

  4. Evaluation of an olefin metathesis pre-catalyst with a bulky and electron-rich N-heterocyclic carbene

    KAUST Repository

    Manzini, Simone

    2015-03-01

    The commercially-available metathesis pre-catalyst M23 has been evaluated alongside new complex [RuCl2((3-phenyl)indenylidene)(PPh3)(SIPrOMe)] (1), which bears a para-methoxy-substituted N-heterocyclic carbene ligand. Several model metathesis reactions could be conducted using only parts-per-million levels of ruthenium catalyst. The effects of the different NHC ligands on reactivity have been explored.

  5. 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.

  6. Evaluation of an olefin metathesis pre-catalyst with a bulky and electron-rich N-heterocyclic carbene

    KAUST Repository

    Manzini, Simone; Urbina Blanco, Cé sar A.; Nelson, David J.; Poater, Albert; Lebl, Tomas; Meiries, Sé bastien; Slawin, Alexandra M.Z.; Falivene, Laura; Cavallo, Luigi; Nolan, Steven P.

    2015-01-01

    The commercially-available metathesis pre-catalyst M23 has been evaluated alongside new complex [RuCl2((3-phenyl)indenylidene)(PPh3)(SIPrOMe)] (1), which bears a para-methoxy-substituted N-heterocyclic carbene ligand. Several model metathesis reactions could be conducted using only parts-per-million levels of ruthenium catalyst. The effects of the different NHC ligands on reactivity have been explored.

  7. How does the addition of steric hindrance to a typical N-heterocyclic carbene ligand affect catalytic activity in olefin metathesis?

    KAUST Repository

    Poater, Albert; Falivene, Laura; Urbina-Blanco, Cé sar A.; Manzini, Simone; Nolan, Steven P.; Cavallo, Luigi

    2013-01-01

    Density functional theory (DFT) calculations were used to predict and rationalize the effect of the modification of the structure of the prototype 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) N-heterocyclic carbene (NHC) ligand. The modification consists in the substitution of the methyl groups of ortho isopropyl substituent with phenyl groups, and here we plan to describe how such significant changes affect the metal environment and therefore the related catalytic behaviour. Bearing in mind that there is a significant structural difference between both ligands in different olefin metathesis reactions, here by means of DFT we characterize where the NHC ligand plays a more active role and where it is a simple spectator, or at least its modification does not significantly change its catalytic role/performance. © 2013 The Royal Society of Chemistry.

  8. Atroposelective Synthesis of Axially Chiral Biaryls by Palladium-Catalyzed Asymmetric C-H Olefination Enabled by a Transient Chiral Auxiliary.

    Science.gov (United States)

    Yao, Qi-Jun; Zhang, Shuo; Zhan, Bei-Bei; Shi, Bing-Feng

    2017-06-01

    Atroposelective synthesis of axially chiral biaryls by palladium-catalyzed C-H olefination, using tert-leucine as an inexpensive, catalytic, and transient chiral auxiliary, has been realized. This strategy provides a highly efficient and straightforward access to a broad range of enantioenriched biaryls in good yields (up to 98 %) with excellent enantioselectivities (95 to >99 % ee). Kinetic resolution of trisubstituted biaryls bearing sterically more demanding substituents is also operative, thus furnishing the optically active olefinated products with excellent selectivity (95 to >99 % ee, s-factor up to 600). © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Synthesis of Chiral, Enantiopure Allylic Amines by the Julia Olefination of α-Amino Esters

    Directory of Open Access Journals (Sweden)

    Fabio Benedetti

    2016-06-01

    Full Text Available The four-step conversion of a series of N-Boc-protected l-amino acid methyl esters into enantiopure N-Boc allylamines by a modified Julia olefination is described. Key steps include the reaction of a lithiated phenylalkylsulfone with amino esters, giving chiral β-ketosulfones, and the reductive elimination of related α-acetoxysulfones. The overall transformation takes place under mild conditions, with good yields, and without loss of stereochemical integrity, being in this respect superior to the conventional Julia reaction of α-amino aldehydes.

  10. Synthesis of Chiral, Enantiopure Allylic Amines by the Julia Olefination of α-Amino Esters.

    Science.gov (United States)

    Benedetti, Fabio; Berti, Federico; Fanfoni, Lidia; Garbo, Michele; Regini, Giorgia; Felluga, Fulvia

    2016-06-21

    The four-step conversion of a series of N-Boc-protected l-amino acid methyl esters into enantiopure N-Boc allylamines by a modified Julia olefination is described. Key steps include the reaction of a lithiated phenylalkylsulfone with amino esters, giving chiral β-ketosulfones, and the reductive elimination of related α-acetoxysulfones. The overall transformation takes place under mild conditions, with good yields, and without loss of stereochemical integrity, being in this respect superior to the conventional Julia reaction of α-amino aldehydes.

  11. Alkane Metathesis

    KAUST Repository

    Basset, Jean-Marie

    2015-03-29

    Catalytic activation of alkanes which directly transforms light alkanes into higher homologs is a major area in organometallic chemistry and petrochemical chemistry. This transformation is a chemical challenge considering the inertness of the sp3 carbon-hydrogen bond. It is generally accepted that this catalytic process involves the formation of olefins. This reaction is defined as alkane metathesis. To date, two catalytic systems of alkane metathesis exist: (i) a single catalytic system prepared by surface organometallic chemistry, acting as multifunctional-supported catalyst which transforms any alkanes into a mixture of their lower and higher homologs and (ii) the other catalytic systems employing a tandem strategy with two different metals, one metal for alkane (de)hydrogenation and another for olefin metathesis in which the activity of these catalysts is essentially driven by the performance of the (de)hydrogenation steps. In this book chapter, we would focus on the evolution of these two classes of catalysts by looking at their specific reactivity of the catalysts towards alkanes, comparing their performances and studying the mechanism.

  12. 1-O-vinyl glycosides via Tebbe olefination, their use as chiral auxiliaries and monomers.

    Science.gov (United States)

    Yuan, Jialong; Lindner, Kristof; Frauenrath, Holger

    2006-07-21

    A series of anomerically pure 1-O-formyl glycosides 1 was prepared and converted into the corresponding 1-O-vinyl glycosides 2 by Tebbe olefination. The unsubstituted vinyl glycosides were obtained as anomerically pure compounds in good yields, and the method of preparation was compatible with the presence of a variety of functional groups. Remarkably, the anomeric formate group was regioselectively converted into the corresponding olefin in the presence of acetate and benzoate protecting groups. With the perspective to use the 1-O-vinyl glycosides as monomers for the preparation of glycosylated poly(vinyl alcohol) derivatives with controlled tacticity, their scope as chiral auxiliaries for a stereodifferentiation in addition reactions to the olefin function was investigated by using the [2+2] cycloaddition to dichloroketene as a model reaction. In particular, vinyl 2,3,4,6-tetra-O-benzoyl-alpha-d-mannopyranoside (2i) exhibited excellent diastereoselectivity. Finally, the 1-O-vinyl glycosides were successfully subjected to radical homopolymerization in bulk or used as electron-rich comonomers in radical copolymerizations with maleic anhydride, yielding alternating, glycosylated poly(vinyl alcohol-alt-maleic anhydride).

  13. Bidirectional cross metathesis and ring-closing metathesis/ring opening of a C2-symmetric building block: a strategy for the synthesis of decanolide natural products

    Directory of Open Access Journals (Sweden)

    Bernd Schmidt

    2013-11-01

    Full Text Available Starting from the conveniently available ex-chiral pool building block (R,R-hexa-1,5-diene-3,4-diol, the ten-membered ring lactones stagonolide E and curvulide A were synthesized using a bidirectional olefin-metathesis functionalization of the terminal double bonds. Key steps are (i a site-selective cross metathesis, (ii a highly diastereoselective extended tethered RCM to furnish a (Z,E-configured dienyl carboxylic acid and (iii a Ru–lipase-catalyzed dynamic kinetic resolution to establish the desired configuration at C9. Ring closure was accomplished by macrolactonization. Curvulide A was synthesized from stagonolide E through Sharpless epoxidation.

  14. Bidirectional cross metathesis and ring-closing metathesis/ring opening of a C 2-symmetric building block: a strategy for the synthesis of decanolide natural products.

    Science.gov (United States)

    Schmidt, Bernd; Kunz, Oliver

    2013-01-01

    Starting from the conveniently available ex-chiral pool building block (R,R)-hexa-1,5-diene-3,4-diol, the ten-membered ring lactones stagonolide E and curvulide A were synthesized using a bidirectional olefin-metathesis functionalization of the terminal double bonds. Key steps are (i) a site-selective cross metathesis, (ii) a highly diastereoselective extended tethered RCM to furnish a (Z,E)-configured dienyl carboxylic acid and (iii) a Ru-lipase-catalyzed dynamic kinetic resolution to establish the desired configuration at C9. Ring closure was accomplished by macrolactonization. Curvulide A was synthesized from stagonolide E through Sharpless epoxidation.

  15. Cationic bis-N-heterocyclic carbene (NHC) ruthenium complex: Structure and application as latent catalyst in olefin metathesis

    KAUST Repository

    Rouen, Mathieu

    2014-09-11

    An unexpected cationic bis-N-heterocyclic carbene (NHC) benzylidene ether based ruthenium complex (2 a) was prepared through the double incorporation of an unsymmetrical unsaturated N-heterocyclic carbene (U2-NHC) ligand that bore an N-substituted cyclododecyl side chain. The isolation and full characterization (including X-ray diffraction studies) of key synthetic intermediates along with theoretical calculations allowed us to understand the mechanism of the overall cationization process. Finally, the newly developed complex 2 a displayed interesting latent behavior during ring-closing metathesis, which could be "switched on" under acidic conditions.

  16. Olefin cross metathesis based de novo synthesis of a partially protected L-amicetose and a fully protected L-cinerulose derivative

    Directory of Open Access Journals (Sweden)

    Bernd Schmidt

    2014-05-01

    Full Text Available Cross metathesis of a lactate derived allylic alcohol and acrolein is the entry point to a de novo synthesis of 4-benzoate protected L-amicetose and a cinerulose derivative protected at C5 and C1.

  17. Unsaturated Fatty Acid Esters Metathesis Catalyzed by Silica Supported WMe5

    KAUST Repository

    Riache, Nassima

    2015-11-14

    Metathesis of unsaturated fatty acid esters (FAEs) by silica supported multifunctional W-based catalyst is disclosed. This transformation represents a novel route towards unsaturated di-esters. Especially, the self-metathesis of ethyl undecylenate results almost exclusively on the homo-coupling product whereas with such catalyst, 1-decene gives ISOMET (isomerization and metathesis olefin) products. The olefin metathesis in the presence of esters is very selective without any secondary cross-metathesis products demonstrating that a high selective olefin metathesis could operate at 150 °C. Additionally, a cross-metathesis of unsaturated FAEs and α-olefins allowed the synthesis of the corresponding ester with longer hydrocarbon skeleton without isomerisation.

  18. Influence of the acid and basic properties of rhenium oxide supported on alumina catalyst on the catalytic performance in olefin metathesis; Influence des proprietes acido-basiques de l`oxyde de rhenium supporte sur les performances catalytiques en metathese des olefines

    Energy Technology Data Exchange (ETDEWEB)

    Nahama, F.

    1996-11-30

    The aim of this work is to study the influence of the acid-basic properties of rhenium oxide supported on alumina catalyst on the catalytic performance in olefin metathesis. The literature data indicate that the environment of the active site does possess acid properties. However, the nature of the acid sites is still matter of debate. Concerning the Re O{sub x} - Al{sub 2}O{sub 3} interactions, we have shown that perrhenate ions are electrostatically absorbed on alumina. The uptake of rhenium is favoured at acidic pH (below 4), and the absorbed rhenium is in equilibrium with rhenium in solution. The results of rhenium extraction by water strongly suggest that the surface compounds of the calcined Re{sub 2}O{sub 7}/Al{sub 2}O{sub 3} materials is aluminium perrhenate. Characterization of surface acidity of the catalyst by infrared spectroscopy reveals that the initiation of the metathesis reaction is governed essentially by Lewis acidity. This strongly supports the role of Lewis acidity, which is exalted by the increase of the rhenium content and the calcination temperature. Finally, we point out by ammonia adsorption-thermodesorption a band at 1320 cm{sup -1} characteristic of the Lewis acidity of aluminium perrhenate. This result is a second indication of the presence of aluminium perrhenate on the Re{sub 2}O{sub 7}/Al{sub 2}O{sub 3} catalyst surface. (author)

  19. "Hydro-metathesis" of olefins: A catalytic reaction using a bifunctional single-site tantalum hydride catalyst supported on fibrous silica (KCC-1) nanospheres

    KAUST Repository

    Polshettiwar, Vivek

    2011-02-18

    Tantalizing hydrocarbons: Tantalum hydride supported on fibrous silica nanospheres (KCC-1) catalyzes, in the presence of hydrogen, the direct conversion of olefins into alkanes that have higher and lower numbers of carbon atoms (see scheme). This catalyst shows remarkable catalytic activity and stability, with excellent potential of regeneration. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. "Hydro-metathesis" of olefins: A catalytic reaction using a bifunctional single-site tantalum hydride catalyst supported on fibrous silica (KCC-1) nanospheres

    KAUST Repository

    Polshettiwar, Vivek; Thivolle-Cazat, Jean; Taoufik, Mostafa; Stoffelbach, Franç ois; Norsic, Sé bastien; Basset, Jean-Marie

    2011-01-01

    Tantalizing hydrocarbons: Tantalum hydride supported on fibrous silica nanospheres (KCC-1) catalyzes, in the presence of hydrogen, the direct conversion of olefins into alkanes that have higher and lower numbers of carbon atoms (see scheme). This catalyst shows remarkable catalytic activity and stability, with excellent potential of regeneration. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Olefins metathesis, synthesis and properties of homogeneous models of the Re{sub 2}O{sub 7}/Al{sub 2}O{sub 3} catalyst; Methathese des olefines, synthese et proprietes des modeles homogenes du catalyseur Re{sub 2}O{sub 7}/Al{sub 2}O{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Doledec, G.

    1999-10-05

    The aim of this work was to synthesize and to study homogeneous models of the rhenium oxide on alumina catalyst in order to better understand the influence of the alumina environment over the activity in olefin metathesis. A series of aluminium complexes (ArO){sub 2}Al-Y have been synthesised, where ArO is a 4-substituted-2,6-di-tert-butyl-phenoxy, or (ArO){sub 2} is a CH{sub 2{sup -}} or S-ortho bridged-4,4'-di-tert-butyl-di-phenoxy, and Y is an alkyl or chlorine ligand. The reaction of (ArO){sub 2}Al-Cl with AgReO{sub 4} led to new complexes (ArO){sub 2}Al-OReO{sub 3} (A). These complexes exhibit a low to moderate activity in metathesis of 2-pentene (TOF = 0,5 min{sup -1} at 25 deg. C in a toluene solution). Complexes (ArO){sub 2}Al-R (R = iBu, Et) react with Re{sub 2}O{sub 7} in THF or dioxane giving type B complexes including oligomeric linkages like O{sub 3}Re-[Al(OAr)-O){sub 2}-ReO{sub 3}. They show a fairly high activity in the metathesis of 2-pentene, with TOF values as high as 100 min{sup -1}. As far as we know, these are the most active rhenium-based homogeneous metathesis catalysts. Complexes type A may be converted into type B complexes upon reaction with (ArO){sub 2}Al-R in an ether solvent. The high activity of B complexes is tentatively related to the Al-O-Al linkages that are molecular in the homogeneous models or present at the surface of the alumina in the heterogeneous catalyst. These results bear out again the role of the Lewis acidity in these catalysts. We used (ArO){sub 2}Al-R complexes to modify the heterogenous catalyst. It appears that it is an excellent way to reduce the rhenium loading without any loss of activity. (author)

  2. CH3-ReO3 on gamma-Al2O3: understanding its structure, initiation,and reactivity in olefin metathesis

    Energy Technology Data Exchange (ETDEWEB)

    Salameh, Alain; Joubert, Jerome; Baudouin, Anne; Lukens, Wayne; Delbecq, Francoise; Sautet, Philippe; Basset, Jean Marie; Coperet,Christophe

    2007-01-20

    Me-ReO3 on gamma-alumina: understanding the structure, theinitiation and thereactivity of a highly active olefin metathesiscatalyst Heterolytic splitting of the C-H bond of the methyl group ofCH3ReO3 on AlsO reactive sites of alumina as a way to generate the activesite of CH3ReO3 supported on gamma-Al203.

  3. Impact of electronic modification of the chelating benzylidene ligand in cis-dichloro-configured second-generation olefin metathesis catalysts on their activity

    KAUST Repository

    Pump, Eva; Poater, Albert; Zirngast, Michaela; Torvisco, Ana; Fischer, Roland C.; Cavallo, Luigi; Slugovc, Christian

    2014-01-01

    A series of electronically modified second-generation cis-dichloro ruthenium ester chelating benzylidene complexes was prepared, characterized, and benchmarked in a typical ring-opening metathesis polymerization (ROMP) experiment. The electronic tuning of the parent chelating benzylidene ligand (2-ethyl ester benzylidene) was achieved by substitution at the 4- and 5-positions with electron-withdrawing nitro or electron-donating methoxy groups. The effect of the electronic tuning on the cis-trans isomerization process was studied experimentally and theoretically. Density functional theory calculations clearly revealed the influence of electronic modification on the relative stability between the cis and trans isomers, which is decisive for the activity of the studied compounds as initiators in ROMP. © 2014 American Chemical Society.

  4. Impact of electronic modification of the chelating benzylidene ligand in cis-dichloro-configured second-generation olefin metathesis catalysts on their activity

    KAUST Repository

    Pump, Eva

    2014-06-09

    A series of electronically modified second-generation cis-dichloro ruthenium ester chelating benzylidene complexes was prepared, characterized, and benchmarked in a typical ring-opening metathesis polymerization (ROMP) experiment. The electronic tuning of the parent chelating benzylidene ligand (2-ethyl ester benzylidene) was achieved by substitution at the 4- and 5-positions with electron-withdrawing nitro or electron-donating methoxy groups. The effect of the electronic tuning on the cis-trans isomerization process was studied experimentally and theoretically. Density functional theory calculations clearly revealed the influence of electronic modification on the relative stability between the cis and trans isomers, which is decisive for the activity of the studied compounds as initiators in ROMP. © 2014 American Chemical Society.

  5. Variation of the Sterical Properties of the N-Heterocyclic Carbene Coligand in Thermally Triggerable Ruthenium-Based Olefin Metathesis Precatalysts/Initiators

    KAUST Repository

    Pump, Eva

    2015-11-09

    A series of ruthenium complexes based on the κ(C,N)-(2-(benzo[h]quinolin-10-yl)methylidene ruthenium dichloride fragment featuring different neutral coligands L (L = 1,3-bis(2,6-diisopropylphenyl)-4,5-dihydroimidazol-2-ylidene (SIPr), 1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene (SIMes), 1,3-bis(2,4-dimethylphenyl)-4,5-dihydroimidazol-2-ylidene (SIXyl), and 1,3-bis(2-methylphenyl)-4,5-dihydroimidazol-2-ylidene (SITol)) was prepared, characterized, and tested in the thermally induced ring-opening metathesis polymerization of dicyclopentadiene. In addition, the corresponding tricyclohexylphosphine derivative was investigated for comparison. All compounds were isolated as their trans-dichloro isomers. NMR spectroscopic features as well as structural features are, particularly within the NHC-bearing complexes, very similar, but their polymerization activity at elevated temperatures is distinctly different. While the SIMes derivative shows the desired properties, i.e., latency at room temperature and pronounced polymerization activity at elevated temperature, all other preinitiators do not. The preinitiator featuring the SIPr coligand is the most latent one, needing temperatures > 140 °C to show moderate activity in the polymerization of dicyclopentadiene. Compounds bearing the smaller N-heterocyclic carbene congeners are stable and latent at room temperature, but decompose upon heating, diminishing the polymerization activity at elevated temperatures. Density functional calculations show that the SIMes derivative is the easiest to activate and yields the most stable 14-electron intermediate. Finally calculations reveal a distinct influence of the nature of the N-heterocyclic carbene ligand on the position of the equilibrium of cis- and trans-dichloro isomers of the complexes. While the SIPr and the SIMes derivatives prefer the cis-configuration, all other derivatives favor, at least in solvents with low dielectric constants, the trans

  6. Metathesis of alkanes and related reactions

    KAUST Repository

    Basset, Jean-Marie

    2010-02-16

    (Figure Presented) The transformation of alkanes remains a difficult challenge because of the relative inertness of the C-H and C-C bonds. The rewards for asserting synthetic control over unfunctionalized, saturated hydrocarbons are considerable, however, because converting short alkanes into longer chain analogues is usually a value-adding process. Alkane metathesis is a novel catalytic and direct transformation of two molecules of a given alkane into its lower and higher homologues; moreover, the process proceeds at relatively low temperature (ambient conditions or higher). It was discovered through the use of a silica-supported tantalum hydride, (=SiO)2TaH, a multifunctional catalyst with a single site of action. This reaction completes the story of the metathesis reactions discovered over the past 40 years: olefin metathesis, alkyne metathesis, and ene-yne cyclizations. In this Account, we examine the fundamental mechanistic aspects of alkane metathesis as well as the novel reactions that have been derived from its study. The silica-supported tantalum hydride catalyst was developed as the result of systematic and meticulous studies of the interaction between oxide supports and organometallic complexes, a field of study denoted surface organometallic chemistry (SOMC). A careful examination of this surface-supported tantalum hydride led to the later discovery of aluminasupported tungsten hydride, W(H)3/Al 2O3, which proved to be an even better catalyst for alkane metathesis. Supported tantalum and tungsten hydrides are highly unsaturated, electron-deficient species that are very reactive toward the C-H and C-C bonds of alkanes. They show a great versatility in various other reactions, such as cross-metathesis between methane and alkanes, cross-metathesis between toluene and ethane, or even methane nonoxidative coupling. Moreover, tungsten hydride exhibits a specific ability in the transformation of isobutane into 2,3-dimethylbutane as well as in the metathesis of

  7. Metathesis of alkanes and related reactions.

    Science.gov (United States)

    Basset, Jean-Marie; Copéret, Christophe; Soulivong, Daravong; Taoufik, Mostafa; Cazat, Jean Thivolle

    2010-02-16

    The transformation of alkanes remains a difficult challenge because of the relative inertness of the C-H and C-C bonds. The rewards for asserting synthetic control over unfunctionalized, saturated hydrocarbons are considerable, however, because converting short alkanes into longer chain analogues is usually a value-adding process. Alkane metathesis is a novel catalytic and direct transformation of two molecules of a given alkane into its lower and higher homologues; moreover, the process proceeds at relatively low temperature (ambient conditions or higher). It was discovered through the use of a silica-supported tantalum hydride, ([triple bond]SiO)(2)TaH, a multifunctional catalyst with a single site of action. This reaction completes the story of the metathesis reactions discovered over the past 40 years: olefin metathesis, alkyne metathesis, and ene-yne cyclizations. In this Account, we examine the fundamental mechanistic aspects of alkane metathesis as well as the novel reactions that have been derived from its study. The silica-supported tantalum hydride catalyst was developed as the result of systematic and meticulous studies of the interaction between oxide supports and organometallic complexes, a field of study denoted surface organometallic chemistry (SOMC). A careful examination of this surface-supported tantalum hydride led to the later discovery of alumina-supported tungsten hydride, W(H)(3)/Al(2)O(3), which proved to be an even better catalyst for alkane metathesis. Supported tantalum and tungsten hydrides are highly unsaturated, electron-deficient species that are very reactive toward the C-H and C-C bonds of alkanes. They show a great versatility in various other reactions, such as cross-metathesis between methane and alkanes, cross-metathesis between toluene and ethane, or even methane nonoxidative coupling. Moreover, tungsten hydride exhibits a specific ability in the transformation of isobutane into 2,3-dimethylbutane as well as in the metathesis

  8. Development of the first well-defined tungsten oxo alkyl derivatives supported on silica by SOMC: towards a model of WO3/SiO2 olefin metathesis catalyst

    KAUST Repository

    Mazoyer, Etienne; Merle, Nicolas; Mallmann, Aimery De; Basset, Jean-Marie; Berrier, Elise; Delevoye, Laurent; Paul, Jean Franois; Nicholas, Christopher P.; Gauvin, Ré gis M.; Taoufik, Mostafa

    2010-01-01

    A well-defined, silica-supported tungsten oxo alkyl species prepared by the surface organometallic chemistry approach displays high and sustained activity in propene metathesis. Remarkably, its catalytic performances outpace those of the parent imido derivative, underlining the importance of the oxo ligand in the design of robust catalysts. © 2010 The Royal Society of Chemistry.

  9. Understanding the Hydro-metathesis Reaction of 1-decene by Using Well-defined Silica Supported W, Mo, Ta Carbene/Carbyne Complexes

    KAUST Repository

    Saidi, Aya

    2017-12-21

    Direct conversion of 1-decene to petroleum range alkanes was obtained using hydro-metathesis reaction. To understand this reaction we employed three different well-defined single site catalysts precursors; [(≡Si-O-)W(CH3)5] 1, [(≡Si-O-)Mo(≡CtBu)(CH2tBu)2] 2 and [(≡Si-O)Ta(=CHtBu)(CH2tBu)2] 3. We witnessed that in our conditions olefin metathesis/isomerization of 1-decene occurs much faster followed by reduction of the newly formed olefins rather than reduction of the 1-decene to decane, followed by metathesis of decane. We found that Mo-based catalyst favors 2+2 cycloaddition of 1-decene forming metallocarbene, followed by reduction of the newly formed olefins to alkanes. However, in the case of W and Ta-based catalysts, a rapid isomerization (migration) of the double bond followed by olefin metathesis and reduction of the newly formed olefins were observed. We witnessed that silica supported W catalyst precursor 1 and Mo catalyst precursor 2 are better catalysts for hydro-metathesis reaction with TONs of 818 and 808 than Ta-based catalyst 3 (TON of 334). This comparison of the catalysts provides us a better understanding that, if a catalyst is efficient in olefin metathesis reaction it would be a better catalyst for hydro-metathesis reaction.

  10. Hexacoordinate Ru-based olefin metathesis catalysts with pH-responsive N-heterocyclic carbene (NHC and N-donor ligands for ROMP reactions in non-aqueous, aqueous and emulsion conditions

    Directory of Open Access Journals (Sweden)

    Shawna L. Balof

    2015-10-01

    Full Text Available Three new ruthenium alkylidene complexes (PCy3Cl2(H2ITapRu=CHSPh (9, (DMAP2Cl2(H2ITapRu=CHPh (11 and (DMAP2Cl2(H2ITapRu=CHSPh (12 have been synthesized bearing the pH-responsive H2ITap ligand (H2ITap = 1,3-bis(2’,6’-dimethyl-4’-dimethylaminophenyl-4,5-dihydroimidazol-2-ylidene. Catalysts 11 and 12 are additionally ligated by two pH-responsive DMAP ligands. The crystal structure was solved for complex 12 by X-ray diffraction. In organic, neutral solution, the catalysts are capable of performing standard ring-opening metathesis polymerization (ROMP and ring closing metathesis (RCM reactions with standard substrates. The ROMP with complex 11 is accelerated in the presence of two equiv of H3PO4, but is reduced as soon as the acid amount increased. The metathesis of phenylthiomethylidene catalysts 9 and 12 is sluggish at room temperature, but their ROMP can be dramatically accelerated at 60 °C. Complexes 11 and 12 are soluble in aqueous acid. They display the ability to perform RCM of diallylmalonic acid (DAMA, however, their conversions are very low amounting only to few turnovers before decomposition. However, both catalysts exhibit outstanding performance in the ROMP of dicyclopentadiene (DCPD and mixtures of DCPD with cyclooctene (COE in acidic aqueous microemulsion. With loadings as low as 180 ppm, the catalysts afforded mostly quantitative conversions of these monomers while maintaining the size and shape of the droplets throughout the polymerization process. Furthermore, the coagulate content for all experiments stayed <2%. This represents an unprecedented efficiency in emulsion ROMP based on hydrophilic ruthenium alkylidene complexes.

  11. Carbonyl-Olefin Exchange Reaction: Present State and Outlook

    Science.gov (United States)

    Kalinova, Radostina; Jossifov, Christo

    The carbonyl-olefin exchange reaction (COER) is a new reaction between carbonyl group and olefin double bond, which has a formal similarity with the olefin metathesis (OM) - one carbon atom in the latter is replaced with an oxygen atom. Till now the new reaction is performed successfully only when the two functional groups (carbonyl group and olefin double bond) are in one molecule and are conjugated. The α, β-unsaturated carbonyl compounds (substituted propenones) are the compounds with such a structure. They polymerize giving substituted polyacetylenes. The chain propagation step of this polymerization is in fact the COER. The question arises: is it possible the COER to take place when the two functional groups are not in one molecule and are not conjugated, and could this reaction became an alternative of the existing carbonyl olefination reactions?

  12. Design and synthesis of novel bis-annulated caged polycycles via ring-closing metathesis: pushpakenediol

    Directory of Open Access Journals (Sweden)

    Sambasivarao Kotha

    2014-11-01

    Full Text Available Intricate caged molecular frameworks are assembled by an atom economical process via a Diels–Alder (DA reaction, a Claisen rearrangement, a ring-closing metathesis (RCM and an alkenyl Grignard addition. The introduction of olefinic moieties in the pentacycloundecane (PCUD framework at appropriate positions followed by RCM led to the formation of novel heptacyclic cage systems.

  13. Synthesis of Gabosine A and N from Ribose by the Use of Ring-Closing Metathesis

    DEFF Research Database (Denmark)

    Monrad, Rune Nygaard; Fanefjord, Mette; Hansen, Flemming Gundorph

    2009-01-01

    -methylallyl bromide. The functionalized octa-1,7-diene, thus obtained, is converted into the six-membered gabosine skeleton by ring-closing olefin metathesis. Subsequent protective group manipulations and oxidation gives rise to gabosine N in a total of 8 steps from ribose while the synthesis of gabosine...

  14. Tandem cross enyne metathesis (CEYM)-intramolecular Diels-Alder reaction (IMDAR). An easy entry to linear bicyclic scaffolds.

    Science.gov (United States)

    Miró, Javier; Sánchez-Roselló, María; Sanz, Álvaro; Rabasa, Fernando; Del Pozo, Carlos; Fustero, Santos

    2015-01-01

    A new tandem cross enyne metathesis (CEYM)-intramolecular Diels-Alder reaction (IMDAR) has been carried out. It involves conjugated ketones, esters or amides bearing a remote olefin and aromatic alkynes as the starting materials. The overall process enables the preparation of a small family of linear bicyclic scaffolds in a very simple manner with moderate to good levels of diastereoselectivity. This methodology constitutes one of the few examples that employ olefins differently than ethylene in tandem CEYM-IMDAR protocols.

  15. Well-Defined Silica Grafted Molybdenum Bis(imido) Catalysts for Imine Metathesis Reactions

    KAUST Repository

    Barman, Samir

    2017-04-06

    Novel site-isolated tetracoordinated molybdenum complexes possessing bis(imido) ligands, [(≡Si–O)2Mo(═NR)2] (R = t-Bu, 2,6-C6H3-i-Pr2), were immobilized on partially dehydroxylated silica (SiO2-200) by a rigorous surface organometallic chemistry protocol. The newly developed materials adorned with bis(imido) functional units, which were previously exploited mainly as spectator ligands on silica-supported olefin metathesis molybdenum catalysts, are found to be efficient heterogeneous catalytic systems for imine cross metathesis under mild conditions.

  16. Well-Defined Silica Grafted Molybdenum Bis(imido) Catalysts for Imine Metathesis Reactions

    KAUST Repository

    Barman, Samir; Merle, Nicolas; Minenkov, Yury; De Mallmann, Aimery; Samantaray, Manoja; Le Qué mé ner, Fré dé ric; Szeto, Kai C.; Abou-Hamad, Edy; Cavallo, Luigi; Taoufik, Mostafa; Basset, Jean-Marie

    2017-01-01

    Novel site-isolated tetracoordinated molybdenum complexes possessing bis(imido) ligands, [(≡Si–O)2Mo(═NR)2] (R = t-Bu, 2,6-C6H3-i-Pr2), were immobilized on partially dehydroxylated silica (SiO2-200) by a rigorous surface organometallic chemistry protocol. The newly developed materials adorned with bis(imido) functional units, which were previously exploited mainly as spectator ligands on silica-supported olefin metathesis molybdenum catalysts, are found to be efficient heterogeneous catalytic systems for imine cross metathesis under mild conditions.

  17. Synthesis of Heavy Fluorous Ruthenium Metathesis Catalysts Using the Stereoselective Addition of Polyfluoroalkyllithium to Sterically Hindered Diimines

    Czech Academy of Sciences Publication Activity Database

    Hošek, J.; Rybáčková, M.; Čejka, J.; Cvačka, Josef; Kvíčala, J.

    2015-01-01

    Roč. 34, č. 13 (2015), s. 3327 -3334 ISSN 0276-7333 Institutional support: RVO:61388963 Keywords : ring-closing metathesis * form tetrasubstituted olefins * N-heterocyclic carbene Subject RIV: CC - Organic Chemistry Impact factor: 4.186, year: 2015

  18. Simple addition of silica to an alkane solution of Wilkinson WMe6 or Schrock W alkylidyne complex give active complex for saturated and unsaturated hydrocarbons metathesis

    KAUST Repository

    Callens, Emmanuel

    2015-08-24

    Addition of PDA silica to a solution of the Wilkinson WMe6 as well as the Schrock W neopentilidyne tris neopentyl complex catalyzes linear or cyclic alkanes to produce respectively a distribution of linear alkanes from methane up to triacontane or a mixture of cyclic and macrocyclic hydrocarbons. This single catalytic system transforms also linear α-olefins into higher and lower homologues via isomerization/metathesis mechanism (ISOMET). This complex is also efficient towards functionalized olefins. Unsaturated fatty acid esters (FAEs) are converted into diesters corresponding to self-metathesis products.

  19. 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.

  20. Ultrasound-assisted self-metathesis reactions of monounsaturated fatty acids

    Directory of Open Access Journals (Sweden)

    Elmkaddem Mohammed Kamal

    2016-09-01

    Full Text Available An efficient protocol for the self-metathesis of oleic acid, using ruthenium catalysts is described. The self-metathesis reaction under ultrasonic activation allows the conversion of monoenic fatty acids such as oleic acid, elaidic acid and erucic acid into diacids and olefins with very short reaction times in the presence of Grubbs ruthenium catalysts. These yields and selectivity towards the desired products are influenced by the nature of solvents. This study demonstrated that metathesis reaction carried out in DCM or 1-butanol showed promising results, since it produced a variety of products, like n-alkenes and diacids with good yields (45–75% and high selectivities (75–95%.

  1. Insights into the decomposition of olefin metathesis precatalysts

    KAUST Repository

    Manzini, Simone

    2014-06-02

    The decomposition of a series of benzylidene, methylidene, and 3-phenylindenylidene complexes has been probed in alcohol solution in the presence of base. Tricyclohexylphosphane-containing precatalysts are shown to yield [RuCl(H)(H2)(PCy3)2] in isopropyl alcohol solutions, while 3-phenylindenylidene complexes lead to η5-(3- phenyl)indenyl products. The potential-energy surfaces for the formation of the latter species have been probed using density functional theory studies. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Factors influencing ring closure through olefin metathesis – A ...

    Indian Academy of Sciences (India)

    Unknown

    the substituents/functional groups present on the alkenes as well as at the allylic position. This article presents an overview of these ... med and (4) functional groups/substituents present in the substrate. The past several years have ..... Ackermann I, Tom D E and Furstner A 2000 Tetra- hedron 56 2196. 13. Holder S and ...

  3. Insights into the decomposition of olefin metathesis precatalysts

    KAUST Repository

    Manzini, Simone; Poater, Albert; Nelson, David J.; Cavallo, Luigi; Slawin, Alexandra M. Z.; Nolan, Steven P.

    2014-01-01

    The decomposition of a series of benzylidene, methylidene, and 3-phenylindenylidene complexes has been probed in alcohol solution in the presence of base. Tricyclohexylphosphane-containing precatalysts are shown to yield [RuCl(H)(H2)(PCy3)2] in isopropyl alcohol solutions, while 3-phenylindenylidene complexes lead to η5-(3- phenyl)indenyl products. The potential-energy surfaces for the formation of the latter species have been probed using density functional theory studies. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Catalytic Enantioselective Synthesis of Naturally Occurring Butenolides via Hetero-Allylic Alkylation and Ring Closing Metathesis

    NARCIS (Netherlands)

    Mao, Bin; Geurts, Koen; Fañanás-Mastral, Martín; Zijl, Anthoni W. van; Fletcher, Stephen P.; Minnaard, Adriaan J.; Feringa, Bernard

    2011-01-01

    An efficient catalytic asymmetric synthesis of chiral γ-butenolides was developed based on the hetero-allylic asymmetric alkylation (h-AAA) in combination with ring closing metathesis (RCM). The synthetic potential of the h-AAA-RCM protocol was illustrated with the facile synthesis of (-)-whiskey

  5. Production and use of light olefins. Preprints of the conference

    Energy Technology Data Exchange (ETDEWEB)

    Ernst, S.; Buzzoni, R.; Leitner, W.; Lercher, J.A.; Lichtscheidl, J.; Nees, F.; Santacesaria, E. (eds.)

    2009-07-01

    Within the conference of the German Society for Petroleum and Coal Science and Technology e.V. (Hamburg, Federal Republic of Germany) in Berlin (Federal Republic of Germany) at 28th to 30th September, 2009, the following lectures were held: (1) Steamcracking - State of the Art (H. Zimmermann); (2) Diversify Feedstock Options to Olefin Production (Q. Ling et al.); (3) Syngas to lower olefins (E. Schwab et al.); (4) STAR process registered for the on-purpose production of propylene (K. Bueker); (5) The catalytic activity of zinc oxide supported on aerosil for C-H activation of light alkanes (S. Arndt et al.); (6) Novel catalytic approaches for the oxidative dehydrogenation of ethane (D. Hartmann); (7) A comparison of the active sites structures of homogeneous and heterogeneous olefin polymerisation catalysts (A. Zecchina); (8) Catalytic strategies in metathesis (C. Coperet); (9) Multi-technology integrated production and consumption of olefins (J. Popp et al.); (10) Olefin oligomerization for the production of fuels and petrochemicals (H. Olivier-Bourbigou et al.); (11) Dieselization of the world - How to increase diesel yield in a refinery (A. Dueker); (12) Isomerization of butenes: LyondellBasell's Isomplus technology development (T. Zak et al.); (13) Valuable products from butadiene, carbon dioxide and further base chemicals (A. Behr); (14) The partial oxidation of propene to propylene oxide using N{sub 2}O as an oxidant (T. Thoemmes); (15) Alternative feedstocks for olefin production: What role will ethanol play? (B.R. Maughon); (16) Production of light olefins from renewable resources - The effect of deoxygenation degree on yields of light olefins (D. Kubicka et al.); (17) Recovery of low olefins from refinery offgases (M. Bender).

  6. Simple activation by acid of latent Ru-NHC-based metathesis initiators bearing 8-quinolinolate co-ligands

    KAUST Repository

    Wappel, Julia

    2016-01-28

    A straightforward synthesis utilizing the ring-opening metathesis polymerization (ROMP) reaction is described for acid-triggered N,O-chelating ruthenium-based pre-catalysts bearing one or two 8-quinolinolate ligands. The innovative pre-catalysts were tested regarding their behavior in ROMP and especially for their use in the synthesis of poly(dicyclopentadiene) (pDCPD). Bearing either the common phosphine leaving ligand in the first and second Grubbs olefin metathesis catalysts, or the Ru–O bond cleavage for the next Hoveyda-type catalysts, this work is a step forward towards the control of polymer functionalization and living or switchable polymerizations.

  7. Simple activation by acid of latent Ru-NHC-based metathesis initiators bearing 8-quinolinolate co-ligands

    KAUST Repository

    Wappel, Julia; Fischer, Roland C; Cavallo, Luigi; Slugovc, Christian; Poater, Albert

    2016-01-01

    A straightforward synthesis utilizing the ring-opening metathesis polymerization (ROMP) reaction is described for acid-triggered N,O-chelating ruthenium-based pre-catalysts bearing one or two 8-quinolinolate ligands. The innovative pre-catalysts were tested regarding their behavior in ROMP and especially for their use in the synthesis of poly(dicyclopentadiene) (pDCPD). Bearing either the common phosphine leaving ligand in the first and second Grubbs olefin metathesis catalysts, or the Ru–O bond cleavage for the next Hoveyda-type catalysts, this work is a step forward towards the control of polymer functionalization and living or switchable polymerizations.

  8. Pd(II)-Catalyzed Enantioselective C-H Olefination of Diphenylacetic Acids

    Science.gov (United States)

    Shi, Bing-Feng; Zhang, Yang-Hui; Lam, Jonathan K.; Wang, Dong-Hui; Yu, Jin-Quan

    2009-01-01

    Pd(II)-catalyzed enantioselective C-H olefination of diphenylacetic acid substrates has been achieved through the use of mono-protected chiral amino acid ligands. The absolute configuration of the resulting olefinated products is consistent with that of a proposed C-H insertion intermediate. PMID:20017549

  9. Tandem cross enyne metathesis (CEYM–intramolecular Diels–Alder reaction (IMDAR. An easy entry to linear bicyclic scaffolds

    Directory of Open Access Journals (Sweden)

    Javier Miró

    2015-08-01

    Full Text Available A new tandem cross enyne metathesis (CEYM–intramolecular Diels–Alder reaction (IMDAR has been carried out. It involves conjugated ketones, esters or amides bearing a remote olefin and aromatic alkynes as the starting materials. The overall process enables the preparation of a small family of linear bicyclic scaffolds in a very simple manner with moderate to good levels of diastereoselectivity. This methodology constitutes one of the few examples that employ olefins differently than ethylene in tandem CEYM–IMDAR protocols.

  10. Supported Catalysts Useful in Ring-Closing Metathesis, Cross Metathesis, and Ring-Opening Metathesis Polymerization

    Directory of Open Access Journals (Sweden)

    Jakkrit Suriboot

    2016-04-01

    Full Text Available Ruthenium and molybdenum catalysts are widely used in synthesis of both small molecules and macromolecules. While major developments have led to new increasingly active catalysts that have high functional group compatibility and stereoselectivity, catalyst/product separation, catalyst recycling, and/or catalyst residue/product separation remain an issue in some applications of these catalysts. This review highlights some of the history of efforts to address these problems, first discussing the problem in the context of reactions like ring-closing metathesis and cross metathesis catalysis used in the synthesis of low molecular weight compounds. It then discusses in more detail progress in dealing with these issues in ring opening metathesis polymerization chemistry. Such approaches depend on a biphasic solid/liquid or liquid separation and can use either always biphasic or sometimes biphasic systems and approaches to this problem using insoluble inorganic supports, insoluble crosslinked polymeric organic supports, soluble polymeric supports, ionic liquids and fluorous phases are discussed.

  11. 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...

  12. Stereoselective Carbonyl Olefination with Fluorosulfoximines: Facile Access to Z or E Terminal Monofluoroalkenes.

    Science.gov (United States)

    Liu, Qinghe; Shen, Xiao; Ni, Chuanfa; Hu, Jinbo

    2017-01-09

    Terminal monofluoroalkenes are important structural motifs in the design of bioactive compounds, such as homeostasis regulators and mechanism-based enzyme inhibitors. However, it is difficult to control the stereoselectivity of known carbonyl olefination reactions, and olefin metathesis is limited to disubstituted terminal monofluoroalkenes. Although sulfoximines have been used extensively in organic synthesis, reports on their use in carbonyl olefination reactions have not appeared to date. Herein, we report highly stereoselective carbonyl monofluoroolefination with a fluorosulfoximine reagent. The potential of this method is demonstrated by the synthesis of MDL 72161 and by the late-stage monofluoromethylenation of complex molecules, such as haloperidol and steroid derivatives. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Metathesis in the generation of low-temperature gas in marine shales

    Directory of Open Access Journals (Sweden)

    Jarvie Daniel M

    2010-01-01

    Full Text Available Abstract The recent report of low-temperature catalytic gas from marine shales took on additional significance with the subsequent disclosure of natural gas and low-temperature gas at or near thermodynamic equilibrium in methane, ethane, and propane. It is important because thermal cracking, the presumed source of natural gas, cannot generate these hydrocarbons at equilibrium nor can it bring them to equilibrium over geologic time. The source of equilibrium and the source of natural gas are either the same (generation under equilibrium control or closely associated. Here we report the catalytic interconversion of hydrocarbons (metathesis as the source of equilibrium in experiments with Cretaceous Mowry shale at 100°C. Focus was on two metathetic equilibria: methane, ethane, and propane, reported earlier, Q (K = [(C1*(C3]/[(C22], and between these hydrocarbons and n-butane, Q* (K = [(C1*(n-C4]/[(C2*(C3], reported here for the first time. Two observations stand out. Initial hydrocarbon products are near equilibrium and have maximum average molecular weights (AMW. Over time, products fall from equilibrium and AMW in concert. It is consistent with metathesis splitting olefin intermediates [Cn] to smaller intermediates (fission as gas generation creates open catalytic sites ([ ]: [Cn] + [ ] → [Cn-m] + [Cm]. Fission rates increasing exponentially with olefin molecular weight could contribute to these effects. AMW would fall over time, and selective fission of [C3] and [n-C4] would draw Q and Q* from equilibrium. The results support metathesis as the source of thermodynamic equilibrium in natural gas.

  14. Acyclic Diene Metathesis (ADMET Polymerization for Precise Synthesis of Defect-Free Conjugated Polymers with Well-Defined Chain Ends

    Directory of Open Access Journals (Sweden)

    Tahmina Haque

    2015-03-01

    Full Text Available This accounts introduces unique characteristics by adopting the acyclic diene metathesis (ADMET polymerization for synthesis of conjugated polymers, poly(arylene vinylenes, known as promising molecular electronics. The method is more suitable than the other methods in terms of atom efficiency affording defect-free, stereo-regular (exclusive trans polymers with well-defined chain ends; the resultant polymers possess better property than those prepared by the conventional methods. The chain ends (vinyl group in the resultant polymer prepared by ruthenium-carbene catalyst(s can be modified by treating with molybdenum-alkylidene complex (olefin metathesis followed by addition of various aldehyde (Wittig type cleavage, affording the end-functionalized polymers exclusively. An introduction of initiating fragment, the other conjugated segment, and one-pot synthesis of end-functionalized block copolymers, star shape polymers can be achieved by adopting this methodology.

  15. Metathesis: A "Change-Your-Partners" Dance

    Indian Academy of Sciences (India)

    Organic chemistry, the chemistry of carbon compounds, is a fascinating subject. ... In general, a chemical reaction is referred to as 'metathesis' or exchange reaction, if it is of .... pounds (alcohols, ketones, aldehydes, etc.), but is stable for long.

  16. by a solid-state metathesis approach

    Indian Academy of Sciences (India)

    Wintec

    Department of Mechanical Engineering,. † ... A solid-state metathesis approach initiated by microwave energy has been successfully applied for ... and chemical properties of synthesized powders are determined by powder X-ray diffraction, ...

  17. Synthesis and characterization of chiral thorium(IV) and uranium(IV) benzamidinate complexes

    Energy Technology Data Exchange (ETDEWEB)

    Schoene, Sebastian; Maerz, Juliane; Kaden, Peter; Patzschke, Michael; Ikeda-Ohno, Atsushi [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Chemistry of the F-Elements

    2017-06-01

    Two chiral benzamidinate complexes of tetravalent actinides (Th(IV) and U(IV)) were synthesized using a salt metathesis reaction of the corresponding actinide(IV) tetrachlorides and the potassium salt of the chiral benzamidine (S,S)-N,N-Bis-(1-phenylethyl)-benzamidine ((S)-HPEBA). The structure of the complexes was determined with single crystal X-ray diffraction. These are the first examples of chiral amidinate complexes of actinides.

  18. Biofuel by isomerizing metathesis of rapeseed oil esters with (bio)ethylene for use in contemporary diesel engines.

    Science.gov (United States)

    Pfister, Kai F; Baader, Sabrina; Baader, Mathias; Berndt, Silvia; Goossen, Lukas J

    2017-06-01

    Rapeseed oil methyl ester (RME) and (bio)ethylene are converted into biofuel with an evenly rising boiling point curve, which fulfills the strict boiling specifications prescribed by the fuel standard EN 590 for modern (petro)diesel engines. Catalyzed by a Pd/Ru system, RME undergoes isomerizing metathesis in a stream of ethylene gas, leading to a defined olefin, monoester, and diester blend. This innovative refining concept requires negligible energy input (60°C) and no solvents and does not produce waste. It demonstrates that the pressing challenge of increasing the fraction of renewables in engine fuel may be addressed purely chemically rather than by motor engineering.

  19. Recent applications of ring-rearrangement metathesis in organic synthesis

    Directory of Open Access Journals (Sweden)

    Sambasivarao Kotha

    2015-10-01

    Full Text Available Ring-rearrangement metathesis (RRM involves multiple metathesis processes such as ring-opening metathesis (ROM/ring-closing metathesis (RCM in a one-pot operation to generate complex targets. RRM delivers complex frameworks that are difficult to assemble by conventional methods. The noteworthy point about this type of protocol is multi-bond formation and it is an atom economic process. In this review, we have covered literature that appeared during the last seven years (2008–2014.

  20. Olefin Autoxidation in Flow

    OpenAIRE

    Neuenschwander Ulrich; Jensen Klavs F.

    2014-01-01

    Handling hazardous multiphase reactions in flow brings not only safety advantages but also significantly improved performance due to better mass transfer characteristics. In this paper we present a continuous microreactor setup capable of performing olefin autoxidations with O2 under solvent free and catalyst free conditions. Owing to the transparent reactor design consumption of O2 can be visually followed and exhaustion of the gas bubbles marks a clear end point along the channel length coo...

  1. Phosphate Tether-Mediated Ring-Closing Metathesis for the Generation of P-Stereogenic, Z-Configured Bicyclo[7.3.1]- and Bicyclo[8.3.1]phosphates.

    Science.gov (United States)

    Markley, Jana L; Maitra, Soma; Hanson, Paul R

    2016-02-05

    A phosphate tether-mediated ring-closing metathesis (RCM) study to the synthesis of Z-configured, P-stereogenic bicyclo[7.3.1]- and bicyclo[8.3.1]phosphates is reported. Investigations suggest that C3-substitution, olefin substitution, and proximity of the forming olefin to the bridgehead carbon of the bicyclic affect the efficiency and stereochemical outcome of the RCM event. This study demonstrates the utility of phosphate tether-mediated desymmetrization of C2-symmetric, 1,3-anti-diol-containing dienes in the generation of macrocyclic phosphates with potential synthetic and biological utility.

  2. About the activity and selectivity of less well-known metathesis catalysts during ADMET polymerizations

    Directory of Open Access Journals (Sweden)

    Hatice Mutlu

    2010-12-01

    Full Text Available We report on the catalytic activity of commercially available Ru-indenylidene and “boomerang” complexes C1, C2 and C3 in acyclic diene metathesis (ADMET polymerization of a fully renewable α,ω-diene. A high activity of these catalysts was observed for the synthesis of the desired renewable polyesters with molecular weights of up to 17000 Da, which is considerably higher than molecular weights obtained using the same monomer with previously studied catalysts. Moreover, olefin isomerization side reactions that occur during the ADMET polymerizations were studied in detail. The isomerization reactions were investigated by degradation of the prepared polyesters via transesterification with methanol, yielding diesters. These diesters, representing the repeat units of the polyesters, were then quantified by GC-MS.

  3. Unearthing a Well-Defined Highly Active Bimetallic W/Ti Precatalyst Anchored on a Single Silica Surface for Metathesis of Propane

    KAUST Repository

    Samantaray, Manoja; Kavitake, Santosh Giridhar; Morlanes, Natalia Sanchez; Abou-Hamad, Edy; Hamieh, Ali Imad Ali; Dey, Raju; Basset, Jean-Marie

    2017-01-01

    Two compatible organometallic complexes, W(Me)(6) (1) and TiNp4 (2), were successively anchored on a highly dehydroxylated single silica support (SiO2-700) to synthesize the well-defined bimetallic precatalyst [(equivalent to Si-O-)W(Me)(5)(equivalent to Si-O-)Ti(Np)(3)] (4). Precatalyst 4 was characterized at the molecular level using advanced surface organometallic chemistry (SOMC) characterization techniques. The strong autocorrelation observed between methyl of W and Ti in H-1-H-1 multiple-quantum NMR spectra demonstrates that W and Ti species are in close proximity to each other. The bimetallic precatalyst 4, with a turnover number (TON) of 9784, proved to be significantly more efficient than the silica-supported monometallic catalyst [(equivalent to Si-O-)W(Me)(5)] (3), with a TON of 98, for propane metathesis at 150 degrees C in a flow reactor. The dramatic improvement in the activity signifies the cooperativity between Ti and W and indicates that the key step of alkane metathesis (C-H bond activation followed by beta-H elimination) occurs on Ti, followed by olefin metathesis, which occurs on W. We have demonstrated the influence and importance of proximity of Ti to W for achieving such a significantly high activity. This is the first report demonstrating the considerably high activity (TON = 9784) in propane metathesis at moderate temperature (150 degrees C) using a well-defined bimetallic system prepared via the SOMC approach.

  4. Unearthing a Well-Defined Highly Active Bimetallic W/Ti Precatalyst Anchored on a Single Silica Surface for Metathesis of Propane

    KAUST Repository

    Samantaray, Manoja

    2017-02-10

    Two compatible organometallic complexes, W(Me)(6) (1) and TiNp4 (2), were successively anchored on a highly dehydroxylated single silica support (SiO2-700) to synthesize the well-defined bimetallic precatalyst [(equivalent to Si-O-)W(Me)(5)(equivalent to Si-O-)Ti(Np)(3)] (4). Precatalyst 4 was characterized at the molecular level using advanced surface organometallic chemistry (SOMC) characterization techniques. The strong autocorrelation observed between methyl of W and Ti in H-1-H-1 multiple-quantum NMR spectra demonstrates that W and Ti species are in close proximity to each other. The bimetallic precatalyst 4, with a turnover number (TON) of 9784, proved to be significantly more efficient than the silica-supported monometallic catalyst [(equivalent to Si-O-)W(Me)(5)] (3), with a TON of 98, for propane metathesis at 150 degrees C in a flow reactor. The dramatic improvement in the activity signifies the cooperativity between Ti and W and indicates that the key step of alkane metathesis (C-H bond activation followed by beta-H elimination) occurs on Ti, followed by olefin metathesis, which occurs on W. We have demonstrated the influence and importance of proximity of Ti to W for achieving such a significantly high activity. This is the first report demonstrating the considerably high activity (TON = 9784) in propane metathesis at moderate temperature (150 degrees C) using a well-defined bimetallic system prepared via the SOMC approach.

  5. Isobutane/olefin-alkylation

    Energy Technology Data Exchange (ETDEWEB)

    Waitkamp, J.; Maixner, S.

    1983-11-01

    Isobutane/olefin-alkylation - technology and reaction mechanism of a refinery process for production of high octane gasoline components: The alkylation of i-butane with olefins, especially with butenes, is a process for the conversion of light byproducts of a catalytic cracker to high quality gasoline components. Alkylate is a complex mixture of i-paraffins containing 5 to ca. 12 carbon atoms. Due to their octane numbers the four trimethylpentane isomers are the most desirable product components. Indeed, under optimum process conditions these isomers are the main products. Presently, alkylation capacity in the western world amounts to more than 40x10/sup 6/ t/a. Most units are located in the USA. Two liquid-phase processes using sulfuric acid and hydrofluoric acid, respectively, are of commercial importance. At present, there is a definite trend towards HF-alkylation. The reaction mechanism which proceeds via carbocations, is extremely complex. It is composed of a great variety of individual steps. Modern mechanistic concepts are discussed.

  6. Construction of axial chirality by rhodium-catalyzed asymmetric dehydrogenative Heck coupling of biaryl compounds with alkenes.

    Science.gov (United States)

    Zheng, Jun; You, Shu-Li

    2014-11-24

    Enantioselective construction of axially chiral biaryls by direct C-H bond functionalization reactions has been realized. Novel axially chiral biaryls were synthesized by the direct C-H bond olefination of biaryl compounds, using a chiral [Cp*Rh(III)] catalyst, in good to excellent yields and enantioselectivities. The obtained axially chiral biaryls were found as suitable ligands for rhodium-catalyzed asymmetric conjugate additions. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Metylcyclohexane conversion to light olefins

    Directory of Open Access Journals (Sweden)

    SCOFIELD C.F.

    1998-01-01

    Full Text Available This study consists in the evaluation of the catalytic properties of zeolites with different structures in the conversion of methylcyclohexane to light olefins. Results obtained suggest that the steric constrictions of the catalysts used play an important role in hydrogen transfer reactions. Higher selectivities for light olefins (C3= and C4= were observed for zeolites having more closed structures, like MFI and ferrerite, when compared to those having more open ones, like beta, omega and faujasite.

  8. Metylcyclohexane conversion to light olefins

    OpenAIRE

    SCOFIELD, C.F.; BENAZZI, E.; CAUFFRIEZ, H.; MARCILLY, C.

    1998-01-01

    This study consists in the evaluation of the catalytic properties of zeolites with different structures in the conversion of methylcyclohexane to light olefins. Results obtained suggest that the steric constrictions of the catalysts used play an important role in hydrogen transfer reactions. Higher selectivities for light olefins (C3= and C4=) were observed for zeolites having more closed structures, like MFI and ferrerite, when compared to those having more open ones, like beta, omega and fa...

  9. Hydride Olefin complexes of tantalum and niobium

    NARCIS (Netherlands)

    Klazinga, Aan Hendrik

    1979-01-01

    This thesis describes investigations on low-valent tantalum and niobium hydride and alkyl complexes, particularly the dicyclopentadienyl tantalum hydride olefin complexes Cp2Ta(H)L (L=olefin). ... Zie: Summary

  10. Stereoselective synthesis of functionalized cyclic amino acid derivatives via a [2,3]-Stevens rearrangement and ring-closing metathesis.

    Science.gov (United States)

    Nash, Aaron; Soheili, Arash; Tambar, Uttam K

    2013-09-20

    Unnatural cyclic amino acids are valuable tools in biomedical research and drug discovery. A two-step stereoselective strategy for converting simple glycine-derived aminoesters into unnatural cyclic amino acid derivatives has been developed. The process includes a palladium-catalyzed tandem allylic amination/[2,3]-Stevens rearrangement followed by a ruthenium-catalyzed ring-closing metathesis. The [2,3]-rearrangement proceeds with high diastereoselectivity through an exo transition state. Oppolzer's chiral auxiliary was utilized to access an enantiopure cyclic amino acid by this approach, which will enable future biological applications.

  11. Methods for treating a metathesis feedstock with metal alkoxides

    Science.gov (United States)

    Cohen, Steven A.; Anderson, Donde R.; Wang, Zhe; Champagne, Timothy M.; Ung, Thay A.

    2018-04-17

    Various methods are provided for treating and reacting a metathesis feedstock. In one embodiment, the method includes providing a feedstock comprising a natural oil, chemically treating the feedstock with a metal alkoxide under conditions sufficient to diminish catalyst poisons in the feedstock, and, following the treating, combining a metathesis catalyst with the feedstock under conditions sufficient to metathesize the feedstock.

  12. Ru complexes of Hoveyda–Grubbs type immobilized on lamellar zeolites: activity in olefin metathesis reactions

    Czech Academy of Sciences Publication Activity Database

    Balcar, Hynek; Žilková, Naděžda; Kubů, Martin; Mazur, Michal; Bastl, Zdeněk; Čejka, Jiří

    2015-01-01

    Roč. 11, NOV 2015 (2015), s. 2087-2096 ISSN 1860-5397 Institutional support: RVO:61388955 Keywords : Hoveyda-Grubbs type catalyst * hybrid catalysts * lamellar zeolites Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.697, year: 2015

  13. Palladium-Catalyzed Enantioselective C-H Olefination of Diaryl Sulfoxides through Parallel Kinetic Resolution and Desymmetrization.

    Science.gov (United States)

    Zhu, Yu-Chao; Li, Yan; Zhang, Bo-Chao; Zhang, Feng-Xu; Yang, Yi-Nuo; Wang, Xi-Sheng

    2018-03-07

    The first example of Pd II -catalyzed enantioselective C-H olefination with non-chiral or racemic sulfoxides as directing groups was developed. A variety of chiral diaryl sulfoxides were synthesized with high enantioselectivity (up to 99 %) through both desymmetrization and parallel kinetic resolution (PKR). This is the first report of Pd II -catalyzed enantioselective C(sp 2 )-H functionalization through PKR, and it represents a novel strategy to construct sulfur chiral centers. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Direct Wittig Olefination of Alcohols.

    Science.gov (United States)

    Li, Qiang-Qiang; Shah, Zaher; Qu, Jian-Ping; Kang, Yan-Biao

    2018-01-05

    A base-promoted transition metal-free approach to substituted alkenes using alcohols under aerobic conditions using air as the inexpensive and clean oxidant is described. Aldehydes are relatively difficult to handle compared to corresponding alcohols due to their volatility and penchant to polymerize and autoxidize. Wittig ylides are easily oxidized to aldehydes and consequently form homo-olefination products. By the strategy of simultaneously in situ generation of ylides and aldehydes, for the first time, alcohols are directly transferred to olefins with no need of prepreparation of either aldehydes or ylides. Thus, the di/monocontrollable olefination of diols is accomplished. This synthetically practical method has been applied in the gram-scale synthesis of pharmaceuticals, such as DMU-212 and resveratrol from alcohols.

  15. Iron(II)-catalyzed intramolecular aminohydroxylation of olefins with functionalized hydroxylamines.

    Science.gov (United States)

    Liu, Guan-Sai; Zhang, Yong-Qiang; Yuan, Yong-An; Xu, Hao

    2013-03-06

    A diastereoselective aminohydroxylation of olefins with a functionalized hydroxylamine is catalyzed by new iron(II) complexes. This efficient intramolecular process readily affords synthetically useful amino alcohols with excellent selectivity (dr up to > 20:1). Asymmetric catalysis with chiral iron(II) complexes and preliminary mechanistic studies reveal an iron nitrenoid is a possible intermediate that can undergo either aminohydroxylation or aziridination, and the selectivity can be controlled by careful selection of counteranion/ligand combinations.

  16. Synergy between Two Metal Catalysts: A Highly Active Silica Supported Bimetallic W/Zr Catalyst for Metathesis of n-Decane

    KAUST Repository

    Samantaray, Manoja

    2016-06-01

    A well-defined, silica supported, bimetallic precatalyst [≡Si-O-W(Me)5 ≡Si-O-Zr(Np)3](4) has been synthesized for the first time via successively grafting two organometallic complexes [W(CH3)6 (1) followed by ZrNp4 (2)] on a single silica support. Surprisingly, multiple quantum NMR characterization demonstrates that W and Zr species are in close proximity to each other. Hydrogenation of this bimetallic catalyst at room temperature showed the easy formation of Zirconium hydride, probably facilitated by tungsten hydride which was formed at this temperature. This bimetallic W/Zr hydride precatalyst proved to be more efficient (TON: 1436) than the monometallic W hydride (TON: 650) in metathesis of n-decane at 150 0C. This synergy between Zr and W suggests that the slow step of alkane metathesis is the C-H bond activation which occurs on Zr. The produced olefin resulting from a ß–H elimination undergoes easy metathesis on W.

  17. Prenylcoumarins in One or Two Steps by a Microwave-Promoted Tandem Claisen Rearrangement/Wittig Olefination/Cyclization Sequence.

    Science.gov (United States)

    Schultze, Christiane; Schmidt, Bernd

    2018-05-04

    The one-pot synthesis of 8-prenylcoumarins from 1,1-dimethylallylated salicylaldehydes and the stabilized ylide [(ethoxycarbonyl)methylene]triphenylphosphorane under microwave conditions was found to have a limited scope. The sequence suffers from a difficult and sometimes low-yielding synthesis of the precursors and from a competing deprenylation upon microwave irradiation. This side reaction occurs in particular with electron rich arenes with two or more alkoxy groups at adjacent positions, a prominent substitution pattern in naturally occurring 8-prenylcoumarins. Both limitations of this one-step sequence were overcome by a two-step synthesis consisting of a microwave-promoted tandem allyl ether Claisen rearrangement/Wittig olefination and a subsequent olefin cross metathesis with 2-methyl-2-butene. The cross metathesis step proceeds with a high selectivity and yields exclusively the desired prenyl, rather than the alternative crotyl substituent. Several naturally occurring 8-prenylcoumarins that were previously inaccessible have been synthesized in good overall yields along this route.

  18. A tandem cross-metathesis/semipinacol rearrangement reaction.

    Science.gov (United States)

    Plummer, Christopher W; Soheili, Arash; Leighton, James L

    2012-05-18

    An efficient and (E)-selective synthesis of a 6-alkylidenebicyclo[3.2.1]octan-8-one has been developed. The key step is a tandem cross-metathesis/semipinacol rearrangement reaction, wherein the Hoveyda-Grubbs II catalyst, or more likely a derivative thereof, serves as the Lewis acid for the rearrangement. Despite the fact that both the starting alkene and the cross-metathesis product are viable rearrangement substrates, only the latter rearranges, suggesting that the Lewis acidic species is generated only after the cross-metathesis reaction is complete.

  19. A Sociolinguistic Analysis of Metathesis in Azeri Language

    Directory of Open Access Journals (Sweden)

    Biook Behnam

    2012-07-01

    Full Text Available This study tries to investigate the correlation between sociolinguistic parameters such as sex, age, and social class and the use of metathesis in Azeri. There have been few studies from a sociolinguistic perspective on the use of metathesis. Through studying the stigmatized forms of speech in Azeri, the present study indicates that a significant relationship exists between extralinguistic variables and metathesis as a phonological process. The subjects of the study were Azeri speakers living in different districts of Tabriz categorized by three socioeconomically different groups. The statistical analyses of data indicate that there is an intimate and reciprocal relationship between linguistic behavior and social structure.

  20. Chiral superconductors.

    Science.gov (United States)

    Kallin, Catherine; Berlinsky, John

    2016-05-01

    Chiral superconductivity is a striking quantum phenomenon in which an unconventional superconductor spontaneously develops an angular momentum and lowers its free energy by eliminating nodes in the gap. It is a topologically non-trivial state and, as such, exhibits distinctive topological modes at surfaces and defects. In this paper we discuss the current theory and experimental results on chiral superconductors, focusing on two of the best-studied systems, Sr2RuO4, which is thought to be a chiral triplet p-wave superconductor, and UPt3, which has two low-temperature superconducting phases (in zero magnetic field), the lower of which is believed to be chiral triplet f-wave. Other systems that may exhibit chiral superconductivity are also discussed. Key signatures of chiral superconductivity are surface currents and chiral Majorana modes, Majorana states in vortex cores, and the possibility of half-flux quantum vortices in the case of triplet pairing. Experimental evidence for chiral superconductivity from μSR, NMR, strain, polar Kerr effect and Josephson tunneling experiments are discussed.

  1. Preparation of Mesoporous SBA-16 Silica-Supported Biscinchona Alkaloid Ligand for the Asymmetric Dihydroxylation of Olefins

    Directory of Open Access Journals (Sweden)

    Shaheen M. Sarkar

    2014-01-01

    Full Text Available Optically active cinchona alkaloid was anchored onto mesoporous SBA-16 silica and the as-prepared complex was used as a heterogeneous chiral ligand of osmium tetraoxide for the asymmetric dihydroxylation of olefins. The prepared catalytic system provided 90–93% yield of vicinal diol with 92–99% enantioselectivity. The ordered mesoporous SBA-16 silica was found to be a valuable support for the cinchona alkaloid liganded osmium catalyst system which is frequently used in chemical industries and research laboratories for olefin functionalization.

  2. Revisiting the metathesis of 13C-monolabeled ethane

    KAUST Repository

    Maury, Olivier; Lefort, Laurent; Vidal, Vé ronique; Thivolle-Cazat, Jean; Basset, Jean-Marie

    2010-01-01

    The metathesis of 13C-monolabeled ethane leads to the parallel occurrence of degenerate and productive reactions, affording the statistical distribution of the various product isotopomers, which can be rationalized in terms of a mechanistic reaction

  3. Rh(III)-catalyzed olefination of N-sulfonyl imines: synthesis of ortho-olefinated benzaldehydes.

    Science.gov (United States)

    Zhang, Tao; Wu, Lamei; Li, Xingwei

    2013-12-20

    Rh(III)-catalyzed olefination of N-sulfonyl imines using acrylates and styrenes has been achieved for the synthesis of ortho-olefinated benaldehydes. This reaction proceeds via a chelation assisted C-H olefination/in situ hydrolysis process.

  4. Direct, enantioselective α-alkylation of aldehydes using simple olefins.

    Science.gov (United States)

    Capacci, Andrew G; Malinowski, Justin T; McAlpine, Neil J; Kuhne, Jerome; MacMillan, David W C

    2017-11-01

    Although the α-alkylation of ketones has already been established, the analogous reaction using aldehyde substrates has proven surprisingly elusive. Despite the structural similarities between the two classes of compounds, the sensitivity and unique reactivity of the aldehyde functionality has typically required activated substrates or specialized additives. Here, we show that the synergistic merger of three catalytic processes-photoredox, enamine and hydrogen-atom transfer (HAT) catalysis-enables an enantioselective α-aldehyde alkylation reaction that employs simple olefins as coupling partners. Chiral imidazolidinones or prolinols, in combination with a thiophenol, iridium photoredox catalyst and visible light, have been successfully used in a triple catalytic process that is temporally sequenced to deliver a new hydrogen and electron-borrowing mechanism. This multicatalytic process enables both intra- and intermolecular aldehyde α-methylene coupling with olefins to construct both cyclic and acyclic products, respectively. With respect to atom and step-economy ideals, this stereoselective process allows the production of high-value molecules from feedstock chemicals in one step while consuming only photons.

  5. Isotopic chirality

    Energy Technology Data Exchange (ETDEWEB)

    Floss, H.G. [Univ. of Washington, Seattle, WA (United States)

    1994-12-01

    This paper deals with compounds that are chiral-at least in part, due to isotope substitution-and their use in tracing the steric course of enzyme reaction in vitro and in vivo. There are other applications of isotopically chiral compounds (for example, in analyzing the steric course of nonenzymatic reactions and in probing the conformation of biomolecules) that are important but they will not be discussed in this context.

  6. Unsaturated Fatty Acid Esters Metathesis Catalyzed by Silica Supported WMe5

    KAUST Repository

    Riache, Nassima; Callens, Emmanuel; Talbi, Karima; Basset, Jean-Marie

    2015-01-01

    Metathesis of unsaturated fatty acid esters (FAEs) by silica supported multifunctional W-based catalyst is disclosed. This transformation represents a novel route towards unsaturated di-esters. Especially, the self-metathesis of ethyl undecylenate

  7. Reactions of Fischer carbene complexes with Electron-deficient olefins: Scope and limitations of this route to donor-acceptor-substituted cyclopropanes

    Energy Technology Data Exchange (ETDEWEB)

    Wienand, A.; Reissig, H.U. (Inst. fuer Organische Chemie der Technischen Hochschule Darmstadt (West Germany))

    1990-12-01

    The Fischer carbene complex ((CO){sub 5}Cr{double bond}C(OMe)Ph) (1) is able to transfer its carbene ligand to a variety of electron-deficient olefins and provides donor-acceptor-substituted cyclopropanes in good yields. Apt activating groups with respect to the alkene are ester, amide, nitrile, sulfone, and dialkyl phosphonate functions. Methyl vinyl ketone (19) affords products in low yield that may arise from an intermediate cyclopropane derivative. Phenyl vinyl sulfoxide (24) mainly acts as an oxidizing agent, transforming 1 into methyl benzoate. for olefin 24 and {alpha}-(N-methylanilino)acrylonitrile the authors found products that should be formed on an olefin metathesis pathway. The methyl-substituted carbene complex 48 also affords the expected donor-acceptor-substituted cyclopropanes; however, acyclic isomers are formed in higher amounts. The molybdenum and tungsten complexes 55 and 56, respectively, also furnish cyclopropane derivatives, but the yields are lower than with the chromium compound 1. Disubstituted olefins and complex 1 still give the cyclopropanes in moderate yields, while all trisubstituted and most of the difunctionalized alkenes do not react with this Fischer carbene complex. The cyclopropanes synthesized can be deprotonated and alkylated or transformed into ring-opened products. These model reactions demonstrate the synthetic potentials of donor-acceptor-substituted cyclopropanes prepared via Fischer carbene complexes.

  8. New Trends in Olefin Production

    Directory of Open Access Journals (Sweden)

    Ismaël Amghizar

    2017-04-01

    Full Text Available Most olefins (e.g., ethylene and propylene will continue to be produced through steam cracking (SC of hydrocarbons in the coming decade. In an uncertain commodity market, the chemical industry is investing very little in alternative technologies and feedstocks because of their current lack of economic viability, despite decreasing crude oil reserves and the recognition of global warming. In this perspective, some of the most promising alternatives are compared with the conventional SC process, and the major bottlenecks of each of the competing processes are highlighted. These technologies emerge especially from the abundance of cheap propane, ethane, and methane from shale gas and stranded gas. From an economic point of view, methane is an interesting starting material, if chemicals can be produced from it. The huge availability of crude oil and the expected substantial decline in the demand for fuels imply that the future for proven technologies such as Fischer-Tropsch synthesis (FTS or methanol to gasoline is not bright. The abundance of cheap ethane and the large availability of crude oil, on the other hand, have caused the SC industry to shift to these two extremes, making room for the on-purpose production of light olefins, such as by the catalytic dehydrogenation of propane.

  9. Development of neutron shielding material using metathesis-polymer matrix

    Energy Technology Data Exchange (ETDEWEB)

    Sakurai, Yoshinori E-mail: ysakurai@rri.kyoto-u.ac.jp; Sasaki, Akira; Kobayashi, Tooru

    2004-04-21

    A neutron shielding material using a metathesis-polymer matrix, which is a thermosetting resin, was developed. This shielding material has characteristics that can be controlled for different mixing ratios of neutron absorbers and for formation in the laboratory. Additionally, the elastic modulus can be changed at the hardening process, from a flexible elastoma to a mechanically tough solid. Experiments were performed at the Kyoto University Research Reactor in order to determine the important characteristics of this metathesis-polymer shielding material, such as neutron shielding performance, secondary gamma-ray generation and activation. The metathesis-polymer shielding material was shown to be practical and as effective as the other available shielding materials, which mainly consist of thermoplastic resin.

  10. Chirality invariance and 'chiral' fields

    International Nuclear Information System (INIS)

    Ziino, G.

    1978-01-01

    The new field model derived in the present paper actually gives a definite answer to three fundamental questions concerning elementary-particle physics: 1) The phenomenological dualism between parity and chirality invariance: it would be only an apparent display of a general 'duality' principle underlying the intrinsic nature itself of (spin 1/2) fermions and expressed by the anticommutativity property between scalar and pseudoscalar charges. 2) The real physical meaning of V - A current structure: it would exclusively be connected to the one (just pointed out) of chiral fields themselves. 3) The unjustified apparent oddness shown by Nature in weak interactions, for the fact of picking out only one of the two (left- and right-handed) fermion 'chiral' projections: the key to such a 'mystery' would just be provided by the consequences of the dual and partial character of the two fermion-antifermion field bases. (Auth.)

  11. Alkylation of isobutane with light olefins: Yields of alkylates for different olefins

    Energy Technology Data Exchange (ETDEWEB)

    Albright, L.F. [Purdue Univ., West Lafayette, IN (United States); Kranz, K.E.; Masters, K.R. [STRATCO, Inc., Leawood, KS (United States)

    1993-12-01

    For alkylation of isobutane with C{sub 3}-C{sub 5} olefins using sulfuric acid as the catalyst, the yields of alkylates with different olefins are compared as the operating conditions are changed. The results of recent pilot plant experiments with propylene, C{sub 4} olefins, and C{sub 5} olefins permit such comparisons. The yields expressed as weight of alkylate produced per 100 wt of olefin consumed varied from about 201:100 to 220:100. Weight ratios of the isobutane consumed per olefin consumed vary from about 101:100 to 120:100. differences of yield values are explained by the changes in the overall chemistry. The procedure employed to calculate yields with good accuracy is based on the analysis of the alkylate and the amount of conjunct polymers produced. Based on literature data, yields are also reported for alkylations using HF as the catalyst.

  12. Production of olefins from bioethanol. Catalysts, mechanism

    Directory of Open Access Journals (Sweden)

    Kusman Dossumov

    2012-12-01

    Full Text Available This review describes methods of catalytic obtaining from bioethanol of valuable industrial products – olefins, particularly ethylene. Аmong olefins, ethylene is the most popular key raw material of petrochemical synthesis. The scope of appllication of ethylene is almost unlimited in petrochemical products: polyethylene, ethylbenzene, styrene, ethylene dichloride, vinyl chloride etc. It also examines catalysts for the production of olefins and their properties. The most promising and commercially advantageous process of ethylene production by catalytic dehydration of ethanol on catalysts based on modified alumina. And this review discusses the mechanisms of catalytic conversion of ethanol to ethylene.

  13. Alternative Test Method for Olefins in Gasoline

    Science.gov (United States)

    This action proposes to allow for an additional alternative test method for olefins in gasoline, ASTM D6550-05. The allowance of this additional alternative test method will provide more flexibility to the regulated industry.

  14. Myoglobin-Catalyzed Olefination of Aldehydes.

    Science.gov (United States)

    Tyagi, Vikas; Fasan, Rudi

    2016-02-12

    The olefination of aldehydes constitutes a most valuable and widely adopted strategy for constructing carbon-carbon double bonds in organic chemistry. While various synthetic methods have been made available for this purpose, no biocatalysts are known to mediate this transformation. Reported herein is that engineered myoglobin variants can catalyze the olefination of aldehydes in the presence of α-diazoesters with high catalytic efficiency (up to 4,900 turnovers) and excellent E diastereoselectivity (92-99.9 % de). This transformation could be applied to the olefination of a variety of substituted benzaldehydes and heteroaromatic aldehydes, also in combination with different alkyl α-diazoacetate reagents. This work provides a first example of biocatalytic aldehyde olefination and extends the spectrum of synthetically valuable chemical transformations accessible using metalloprotein-based catalysts. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. (Z)-Selective Takai olefination of salicylaldehydes.

    Science.gov (United States)

    Geddis, Stephen M; Hagerman, Caroline E; Galloway, Warren R J D; Sore, Hannah F; Goodman, Jonathan M; Spring, David R

    2017-01-01

    The Takai olefination (or Takai reaction) is a method for the conversion of aldehydes to vinyl iodides, and has seen widespread implementation in organic synthesis. The reaction is usually noted for its high ( E )-selectivity; however, herein we report the highly ( Z )-selective Takai olefination of salicylaldehyde derivatives. Systematic screening of related substrates led to the identification of key factors responsible for this surprising inversion of selectivity, and enabled the development of a modified mechanistic model to rationalise these observations.

  16. Direct catalytic olefination of alcohols with sulfones.

    Science.gov (United States)

    Srimani, Dipankar; Leitus, Gregory; Ben-David, Yehoshoa; Milstein, David

    2014-10-06

    The synthesis of terminal, as well as internal, olefins was achieved by the one-step olefination of alcohols with sulfones catalyzed by a ruthenium pincer complex. Furthermore, performing the reaction with dimethyl sulfone under mild hydrogen pressure provides a direct route for the replacement of alcohol hydroxy groups by methyl groups in one step. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Metathesis synthesis and characterization of complex metal fluoride ...

    Indian Academy of Sciences (India)

    Administrator

    V MANIVANNAN*, P PARHI and JONATHAN W KRAMER. Department of Mechanical Engineering, Campus Delivery 1374, Colorado State University, Fort Collins,. CO 80523, USA. MS received 30 April 2008. Abstract. Metathesis synthesis of complex metal fluorides using mechanochemical activation has been reported.

  18. Revisiting the metathesis of 13C-monolabeled ethane

    KAUST Repository

    Maury, Olivier

    2010-12-13

    The metathesis of 13C-monolabeled ethane leads to the parallel occurrence of degenerate and productive reactions, affording the statistical distribution of the various product isotopomers, which can be rationalized in terms of a mechanistic reaction scheme combining both processes. © 2010 American Chemical Society.

  19. Metathesis synthesis and characterization of complex metal fluoride ...

    Indian Academy of Sciences (India)

    Administrator

    Sivakumar et al 2004; Mandal and Gopalakrishnan 2005). Although metathesis reactions may initiate spontane- ously .... cal lithography are needed (Sahnoun et al 2005). KMF3 materials with perovskite structures are ... (Knox 1961; Machin et al 1963; Pari et al 1994) and shown in figure 5. The KMF3 compounds are anti-.

  20. Synthesis of Mono(perfluoroalkyl) Cyclodextrins via Cross Metathesis

    Czech Academy of Sciences Publication Activity Database

    Řezanka, M.; Eignerová, Barbara; Jindřich, J.; Kotora, M.

    -, č. 32 (2010), s. 6256-6262 ISSN 1434-193X R&D Projects: GA AV ČR KAN200200651 Institutional research plan: CEZ:AV0Z40550506 Keywords : metathesis * cyclodextrins * fluorine * alkylation * amphiphiles Subject RIV: CC - Organic Chemistry Impact factor: 3.206, year: 2010

  1. Recent advances in the development of alkyne metathesis catalysts

    Directory of Open Access Journals (Sweden)

    Matthias Tamm

    2011-01-01

    Full Text Available The number of well-defined molybdenum and tungsten alkylidyne complexes that are able to catalyze alkyne metathesis reactions efficiently has been significantly expanded in recent years.The latest developments in this field featuring highly active imidazolin-2-iminato- and silanolate–alkylidyne complexes are outlined in this review.

  2. Mo-catalyzed cross-metathesis reaction of propynylferrocene

    Czech Academy of Sciences Publication Activity Database

    Bobula, T.; Hudlický, J.; Novák, P.; Gyepes, R.; Císařová, I.; Štěpnička, P.; Kotora, Martin

    -, č. 25 (2008), s. 3911-3920 ISSN 1434-1948 Grant - others:GA MŠk(CZ) LC06070 Program:LC Institutional research plan: CEZ:AV0Z40550506 Keywords : alkynes * metallocenes * metathesis * electrochemistry * X-ray diffraction Subject RIV: CC - Organic Chemistry Impact factor: 2.694, year: 2008

  3. Recent advances in efficient and selective synthesis of di-, tri-, and tetrasubstituted alkenes via Pd-catalyzed alkenylation-carbonyl olefination synergy.

    Science.gov (United States)

    Negishi, Ei-ichi; Huang, Zhihong; Wang, Guangwei; Mohan, Swathi; Wang, Chao; Hattori, Hatsuhiko

    2008-11-18

    precursor to the desired alkene is readily available as an aldehyde, the carbonyl olefination is generally the more convenient of the two. This is a particularly important factor in many cases where the desired alkene contains an allylic asymmetric carbon center, since alpha-chiral aldehydes can be prepared by a variety of known asymmetric methods and readily converted to allylically chiral alkenes via carbonyl olefination. On the other hand, a homoallylically carbon-branched asymmetric center can be readily installed by either Pd-catalyzed isoalkyl-alkenyl coupling or Zr-catalyzed asymmetric carboalumination (ZACA reaction) of 1,4-dienes. In short, it takes all kinds to make alkenes, just as it takes all kinds to make the world.

  4. Divergent Synthesis of Diastereomeric Sphingosines from a Chiral Aziridine

    Energy Technology Data Exchange (ETDEWEB)

    Kang, On-Yu; Shin, Mi-Ri; Kang, Han-Young [Chungbuk National University, Gongju (Korea, Republic of)

    2016-07-15

    All four stereoisomers of sphingosines were synthesized starting from a single intermediate, chiral aziridine (2), which was efficiently prepared by enzymatic desymmetrization in an enatiopure form. Aziridine (2) was converted to 3, which was used for the synthesis of 4. Both the advanced key intermediates, vinylaziridines 3 and 4, were successfully converted to threo-sphingosines 1a and 1b, respectively. Ring-closing metathesis (RCM) using the Grubbs II catalyst was the key reaction in the synthesis. Two erythro-sphingosines 1c and 1d were synthesized by the ring-expansion reactions of vinylaziridines 3 and 4, followed by RCM reactions. The successful divergent synthesis confirmed that chiral vinylaziridine 2 can be used as a key intermediate for the synthesis of sphingosine-related natural products.

  5. Synthesis of Fluoroolefins via Julia-Kocienski Olefination

    OpenAIRE

    Zajc, Barbara; Kumar, Rakesh

    2010-01-01

    The Julia-Kocienski olefination provides a versatile platform for the synthesis of fluorovinyl compounds. This review describes our efforts as well as those of others in the synthesis of various fluorinated aryl and heteroaryl sulfones and their utility as olefination reagents for the modular assembly of fluoroalkenes. Where data is available, the influence of the fluorine atom on the reactivity of the olefination reagents and the stereochemical outcome of the olefination are described.

  6. Synthesis of Fluoroolefins via Julia-Kocienski Olefination.

    Science.gov (United States)

    Zajc, Barbara; Kumar, Rakesh

    2010-01-01

    The Julia-Kocienski olefination provides a versatile platform for the synthesis of fluorovinyl compounds. This review describes our efforts as well as those of others in the synthesis of various fluorinated aryl and heteroaryl sulfones and their utility as olefination reagents for the modular assembly of fluoroalkenes. Where data is available, the influence of the fluorine atom on the reactivity of the olefination reagents and the stereochemical outcome of the olefination are described.

  7. Catalytic olefin polymerization with early transition metal compounds

    NARCIS (Netherlands)

    Eshuis, Johan Jan Willem

    1991-01-01

    The catalysis of organic reactions by soluble metal complexes has become a major tool in synthesis, both in the laboratory and in the chemical industry. Processes catalyzed by transition metal complexes include carbonylation, olefin polymerization, olefin addition, olefin oxidation and alkane and

  8. Olefin copolymerization using atom transfer radical polymerization (ATRP)

    NARCIS (Netherlands)

    Venkatesh, R.; Klumperman, B.

    2003-01-01

    Olefin copolymers of alpha-olefins with polar monomers with various architectures remain an ultimate goal in polyolefin engineering. The present paper is a more detailed study on the copolymn. of alpha-olefins (1-octene) with acrylates (Me acrylate). Comparison of reaction kinetics between free

  9. Chiral symmetry and chiral-symmetry breaking

    International Nuclear Information System (INIS)

    Peskin, M.E.

    1982-12-01

    These lectures concern the dynamics of fermions in strong interaction with gauge fields. Systems of fermions coupled by gauge forces have a very rich structure of global symmetries, which are called chiral symmetries. These lectures will focus on the realization of chiral symmetries and the causes and consequences of thier spontaneous breaking. A brief introduction to the basic formalism and concepts of chiral symmetry breaking is given, then some explicit calculations of chiral symmetry breaking in gauge theories are given, treating first parity-invariant and then chiral models. These calculations are meant to be illustrative rather than accurate; they make use of unjustified mathematical approximations which serve to make the physics more clear. Some formal constraints on chiral symmetry breaking are discussed which illuminate and extend the results of our more explicit analysis. Finally, a brief review of the phenomenological theory of chiral symmetry breaking is presented, and some applications of this theory to problems in weak-interaction physics are discussed

  10. Gamma radiolysis of 3-methylpentane. Effect of added olefins on the formation of C12-olefins

    International Nuclear Information System (INIS)

    Laet, M. de; Tilquin, B.

    1991-01-01

    Contributions of congruent (parent derived) olefins to the formation of unsaturated heavy products (C 12 H 24 ) are investigated. Effects of dose or of olefinic additives on the G yield values are studied by capillary gas chromatography. The dose dependence is explained by transfer of positive charge to congruent olefins (C 6 H 12 ) even though their concentrations build up linearly with dose. γ Irradiation of 3-methylpentane containing pentenes or butenes (0.2-2 mol %) provides good examples of transfer of energy, however the results are unexpected. C-H scission in the radiolysis of solid 3-methylpentane is also reviewed. (author)

  11. Exploiting Confinement Effects to Tune Selectivity in Cyclooctane Metathesis

    KAUST Repository

    Pump, Eva

    2017-08-24

    The mechanism of cyclooctane metathesis using confinement effect strategies in mesoporous silica nanoparticles (MSNs) is discussed by catalytic experiments and density functional theory (DFT) calculations. WMe6 was immobilized inside the pores of a series of MSNs having the same structure but different pore diameters (60, 30 and 25 Å). Experiments in cyclooctane metathesis suggest that confinement effects observed in smaller pores (30 and 25 Å) improve selectivity towards the dimeric cyclohexadecane. In contrast, in larger pores (60 Å) a broad product distribution dominated by ring contracted cycloalkanes was found. The catalytic cycle and potential side reactions occurring at [(≡SiO-)WMe5] were examined with DFT calculations. Analysis of the geometries for the key reaction intermediates allowed to rationalize the impact of a confined environment on the enhanced selectivity towards the dimeric product in smaller pores, while in large pores the ring contracted products are favored.

  12. (Z-Selective Takai olefination of salicylaldehydes

    Directory of Open Access Journals (Sweden)

    Stephen M. Geddis

    2017-02-01

    Full Text Available The Takai olefination (or Takai reaction is a method for the conversion of aldehydes to vinyl iodides, and has seen widespread implementation in organic synthesis. The reaction is usually noted for its high (E-selectivity; however, herein we report the highly (Z-selective Takai olefination of salicylaldehyde derivatives. Systematic screening of related substrates led to the identification of key factors responsible for this surprising inversion of selectivity, and enabled the development of a modified mechanistic model to rationalise these observations.

  13. A theoretical view on the thermodynamic cis-trans equilibrium of dihalo ruthenium olefin metathesis (pre-)catalysts

    KAUST Repository

    Pump, Eva

    2015-02-24

    Abstract: This work was conducted to provide an overview on the position of the thermodynamic cis–trans equilibrium of 85 conventional and X-chelated alkylidene-ruthenium complexes (X=O, S, Se, N, P, Cl, I, Br). The reported energies (ΔE) were obtained through single-point calculations with M06 functional and TZVP basis set from BP86/SVP-optimized cis- and trans-dichloro geometries and using the polarizable continuum model to simulate the influence of the solvent. Dichloromethane and toluene were selected as examples for solvents with high and low dielectric constants. The obtained relative stabilities of the cis- and trans-dihalo derivatives of the respective alkylidene complexes will serve for a better explanation of their catalytic activity as has been disclosed herein with selected examples.Graphical abstract: [Figure not available: see fulltext.

  14. A theoretical view on the thermodynamic cis-trans equilibrium of dihalo ruthenium olefin metathesis (pre-)catalysts

    KAUST Repository

    Pump, Eva; Cavallo, Luigi; Slugovc, Christian

    2015-01-01

    obtained through single-point calculations with M06 functional and TZVP basis set from BP86/SVP-optimized cis- and trans-dichloro geometries and using the polarizable continuum model to simulate the influence of the solvent. Dichloromethane and toluene were

  15. Synthesis of anti-tumour phosphatidylinositol analogues from glucose by the use of ring-closing olefin metathesis

    DEFF Research Database (Denmark)

    Andresen, Thomas Lars; Skytte, Dorthe M.; Madsen, Robert

    2004-01-01

    A divergent strategy is described for synthesis of the novel phosphatidylinositols 1-3. The synthetic approach commences from benzyl-protected methyl 6-iodo-6-deoxy-a-D-glucopyranoside, which undergoes zinc-mediated reductive fragmentation followed by vinyl Grignard addition and ring-closing meta...

  16. Chiral mirrors

    International Nuclear Information System (INIS)

    Plum, Eric; Zheludev, Nikolay I.

    2015-01-01

    Mirrors are used in telescopes, microscopes, photo cameras, lasers, satellite dishes, and everywhere else, where redirection of electromagnetic radiation is required making them arguably the most important optical component. While conventional isotropic mirrors will reflect linear polarizations without change, the handedness of circularly polarized waves is reversed upon reflection. Here, we demonstrate a type of mirror reflecting one circular polarization without changing its handedness, while absorbing the other. The polarization-preserving mirror consists of a planar metasurface with a subwavelength pattern that cannot be superimposed with its mirror image without being lifted out of its plane, and a conventional mirror spaced by a fraction of the wavelength from the metasurface. Such mirrors enable circularly polarized lasers and Fabry-Pérot cavities with enhanced tunability, gyroscopic applications, polarization-sensitive detectors of electromagnetic waves, and can be used to enhance spectroscopies of chiral media

  17. Olefin Recovery from Chemical Industry Waste Streams

    Energy Technology Data Exchange (ETDEWEB)

    A.R. Da Costa; R. Daniels; A. Jariwala; Z. He; A. Morisato; I. Pinnau; J.G. Wijmans

    2003-11-21

    The objective of this project was to develop a membrane process to separate olefins from paraffins in waste gas streams as an alternative to flaring or distillation. Flaring these streams wastes their chemical feedstock value; distillation is energy and capital cost intensive, particularly for small waste streams.

  18. Cyclic olefin copolymer-silica nanocomposites foams

    Czech Academy of Sciences Publication Activity Database

    Pegoretti, A.; Dorigato, A.; Biani, A.; Šlouf, Miroslav

    2016-01-01

    Roč. 51, č. 8 (2016), s. 3907-3916 ISSN 0022-2461 R&D Projects: GA MŠk(CZ) LO1507 Institutional support: RVO:61389013 Keywords : cyclic olefin copolymer * nanocomposites * silica Subject RIV: CD - Macromolecular Chemistry Impact factor: 2.599, year: 2016

  19. Synthesis of pterostilbene by Julie Olefination

    Science.gov (United States)

    A simple, stereoselective route for the synthesis of the biologically active compounds trans-pterostilbene and tetramethoxy stilbene from the readily available starting materials 3,5-dimethoxy benzyl alcohol and 4-hydroxy benzaldehyde was developed using Julia olefination as a key reaction....

  20. Techno-economic analysis of the coal-to-olefins process in comparison with the oil-to-olefins process

    International Nuclear Information System (INIS)

    Xiang, Dong; Qian, Yu; Man, Yi; Yang, Siyu

    2014-01-01

    Highlights: • Present the opportunities and challenges of coal-to-olefins (CTO) development. • Conduct a techno-economic analysis on CTO compared with oil-to-olefins (OTO). • Suggest approaches for improving energy efficiency and economic performance of CTO. • Analyze effects of plant scale, feedstock price, CO 2 tax on CTO and OTO. - Abstract: Olefins are one of the most important oil derivatives widely used in industry. To reduce the dependence of olefins industry on oil, China is increasing the production of olefins from alternative energy resources, especially from coal. This study is concerned with the opportunities and obstacles of coal-to-olefins development, and focuses on making an overall techno-economic analysis of a coal-to-olefins plant with the capacity of 0.7 Mt/a olefins. Comparison is made with a 1.5 Mt/a oil-to-olefins plant based on three criteria including energy efficiency, capital investment, and product cost. It was found that the coal-based olefins process show prominent advantage in product cost because of the low price of its feedstock. However, it suffers from the limitations of higher capital investment, lower energy efficiency, and higher emissions. The effects of production scale, raw material price, and carbon tax were varied for the two production routes, and thus the operational regions were found for the coal-to-olefins process to be competitive

  1. Chiral Magnetic Spirals

    International Nuclear Information System (INIS)

    Basar, Goekce; Dunne, Gerald V.; Kharzeev, Dmitri E.

    2010-01-01

    We argue that the presence of a very strong magnetic field in the chirally broken phase induces inhomogeneous expectation values, of a spiral nature along the magnetic field axis, for the currents of charge and chirality, when there is finite baryon density or an imbalance between left and right chiralities. This 'chiral magnetic spiral' is a gapless excitation transporting the currents of (i) charge (at finite chirality), and (ii) chirality (at finite baryon density) along the direction of the magnetic field. In both cases it also induces in the transverse directions oscillating currents of charge and chirality. In heavy ion collisions, the chiral magnetic spiral possibly provides contributions both to the out-of-plane and the in-plane dynamical charge fluctuations recently observed at BNL RHIC.

  2. Introduction to Chiral Symmetry

    Energy Technology Data Exchange (ETDEWEB)

    Koch, Volker [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2017-05-09

    These lectures are an attempt to a pedagogical introduction into the elementary concepts of chiral symmetry in nuclear physics. We will also discuss some effective chiral models such as the linear and nonlinear sigma model as well as the essential ideas of chiral perturbation theory. We will present some applications to the physics of ultrarelativistic heavy ion collisionsd.

  3. Introduction to chiral symmetry

    International Nuclear Information System (INIS)

    Koch, V.

    1996-01-01

    These lectures are an attempt to a pedagogical introduction into the elementary concepts of chiral symmetry in nuclear physics. Effective chiral models such as the linear and nonlinear sigma model will be discussed as well as the essential ideas of chiral perturbation theory. Some applications to the physics of ultrarelativistic heavy ion collisions will be presented

  4. Chiral discotics; expression and amplification of chirality

    NARCIS (Netherlands)

    Brunsveld, L.; Meijer, E.W.; Rowan, A.E.; Nolte, R.J.M.; Denmark, S.E.; Nolte, R.J.M.; Meijer, E.W.

    2003-01-01

    In this contribution, chirality and discotic liquid crystals are discussed as a tool for studying the self-assembly of these molecules, both in solution and in the solid state. Therefore, the objective of this chapter is to summarize and elucidate how molecular chirality can be expressed in discotic

  5. Metathesis reactions for the synthesis of ring-fused carbazoles

    CSIR Research Space (South Africa)

    Pelly, SC

    2005-12-09

    Full Text Available stream_source_info pelly_2005.pdf.txt stream_content_type text/plain stream_size 48007 Content-Encoding ISO-8859-1 stream_name pelly_2005.pdf.txt Content-Type text/plain; charset=ISO-8859-1 Metathesis Reactions... (99). N,Nminute-Di-tert-butyldicarboxylate-2,2minute-biindolyl-3,3minute-divi- nyl 12. Into a 50-mL two-necked oven-dried flask, fitted with a dropping funnel, was placed MePPh3Br (533 mg, 1.49 mmol), and the contents of the flask were blanketed...

  6. Catalytic olefin polymerization with early transition metal compounds

    OpenAIRE

    Eshuis, Johan Jan Willem

    1991-01-01

    The catalysis of organic reactions by soluble metal complexes has become a major tool in synthesis, both in the laboratory and in the chemical industry. Processes catalyzed by transition metal complexes include carbonylation, olefin polymerization, olefin addition, olefin oxidation and alkane and arene oxidation. Traditionally, heterogeneous catalysts have been used for the production of large-scale commodity chemicals such as methanol and ammonia and in the production of high octane gasoline...

  7. Conversion of olefins to liquid motor fuels

    Science.gov (United States)

    Rabo, Jule A.; Coughlin, Peter K.

    1988-01-01

    Linear and/or branched claim C.sub.2 to C.sub.12 olefins are converted to hydrocarbon mixtures suitable for use as liquid motor fuels by contact with a catalyst capable of ensuring the production of desirable products with only a relatively minor amount of heavy products boiling beyond the diesel oil range. The catalyst having desirable stability during continuous production operations, comprises a steam stabilized zeolite Y catalyst of hydrophobic character, desirably in aluminum-extracted form. The olefins such as propylene, may be diluted with inerts, such as paraffins or with water, the latter serving to moderate the acidity of the catalyst, or to further moderate the activity of the aluminum-extracted catalyst, so as to increase the effective life of the catalyst.

  8. Thermal 18F atom addition to olefins

    International Nuclear Information System (INIS)

    Rogers, P.J.M.

    1986-01-01

    The addition of thermal 18 F atoms to olefins was investigated using various substrate molecules. The 18 F atoms were produced by the 19 F(n,2n) 18 F nuclear reaction with >10 5 eV of energy which is removed by multiple collisions with SF 6 molecules before reaction occurs with an olefin. By varying the SF 6 /substrate mole ratio it was demonstrated that the fraction of non-thermal reactions is dependent upon the frequency of non-reactive energy reducing collisions with SF 6 . The rate constants for addition and abstraction reactions with propene, cis-1-chloropropene and trans-1-chloropropene were determined. The substitution of a C1 atom for the olefinic H atom in the C 1 position does not affect the rate of 18 F bond formation but it changes the orientation of attack. The 18 F atom prefers the terminal carbon-in propene and propene-d 6 by a factor of 1.35 while the preference is less than 0.5 for the terminal carbon in cis-1-chloropropene and trans-1-chloropropene. The addition of 18 F atoms to olefins creates vibrationally excited fluoroalkyl radicals which can either decompose or stabilize by collision with another molecule. The rate constants for decomposition of excited CH 3 CHCHC1F radicals formed by 18 F addition to cis-1-chloropropene and trans-1-chloropropene are competitive with C 1 -C 2 bond rotation. The 18 F atoms add to the parent molecule with retention of geometry and a memory of the geometry persists as demonstrated by the cis-1-fluoropropene/trans-1-fluoropropene decomposition product ratio

  9. Olefin recovery from FCC off-gas can pay off

    International Nuclear Information System (INIS)

    Brahn, M.G.

    1992-01-01

    This paper reports on olefins recovery from refinery FCC offgas streams which offers an attractive cash flow from olefins from a tail-gas stream that has typically been consumed as refinery fuel. Such recovery schemes can be employed in refineries or olefins plants, and can be tailored to fit individual requirements. Mobil Chemical Co. has operated such a dephlegmator-based off-gas recovery unit at its Beaumont, Tex., olefin plant since 1987. It reported that the project was paid out within 11 months of initial start-up

  10. Rhodium-catalyzed regioselective olefination directed by a carboxylic group.

    Science.gov (United States)

    Mochida, Satoshi; Hirano, Koji; Satoh, Tetsuya; Miura, Masahiro

    2011-05-06

    The ortho-olefination of benzoic acids can be achieved effectively through rhodium-catalyzed oxidative coupling with alkenes. The carboxylic group is readily removable to allow ortho-olefination/decarboxylation in one pot. α,β-Unsaturated carboxylic acids such as methacrylic acid also undergo the olefination at the β-position. Under the rhodium catalysis, the cine-olefination of heteroarene carboxylic acids such as thiophene-2-carboxylic acid proceeds smoothly accompanied by decarboxylation to selectively produce the corresponding vinylheteroarene derivatives. © 2011 American Chemical Society

  11. Study of ethylene/2-butene cross-metathesis over W-H/Al2O 3 for propylene production: Effect of the temperature and reactant ratios on the productivity and deactivation

    KAUST Repository

    Mazoyer, Etienne

    2013-05-01

    A highly active and selective catalyst based on supported tungsten hydride for the cross-metathesis between ethylene and 2-butenes yielding propylene has been investigated at low pressure with various temperatures and feed ratios. At low temperature (120 °C), the catalyst deactivates notably with time on stream. This phenomenon was extensively examined by DRIFTS, TGA, DSC, and solid-state NMR techniques. It was found that a large amount of carbonaceous species were formed due to a side-reaction such as olefin polymerization which took place simultaneously with the metathesis reaction. However, at 150 °C, the catalyst was stable with time and thereby gave a high productivity in propylene. Importantly, the slight increase in temperature clearly disfavored the side reaction. The ratio of ethylene to trans-2-butene was also studied, and surprisingly, the W-H/Al2O3 catalyst is stable and highly selective to propylene even at substoichiometric ethylene ratios. © 2013 Elsevier Inc. All rights reserved.

  12. On chiral and non chiral 1D supermultiplets

    Energy Technology Data Exchange (ETDEWEB)

    Toppan, Francesco, E-mail: toppan@cbpf.b [Centro Brasileiro de Pesquisas Fisicas (TEO/CBPF), Rio de Janeiro, RJ (Brazil). Coordenacao de Fisica Teorica

    2011-07-01

    In this talk I discuss and clarify some issues concerning chiral and non chiral properties of the one-dimensional supermultiplets of the N-extended supersymmetry. Quaternionic chirality can be defined for N = 4, 5, 6, 7, 8. Octonionic chirality for N = 8 and beyond. Inequivalent chiralities only arise when considering several copies of N = 4 or N = 8 supermultiplets. (author)

  13. On chiral and non chiral 1D supermultiplets

    International Nuclear Information System (INIS)

    Toppan, Francesco

    2011-01-01

    In this talk I discuss and clarify some issues concerning chiral and non chiral properties of the one-dimensional supermultiplets of the N-extended supersymmetry. Quaternionic chirality can be defined for N = 4, 5, 6, 7, 8. Octonionic chirality for N = 8 and beyond. Inequivalent chiralities only arise when considering several copies of N = 4 or N = 8 supermultiplets. (author)

  14. Total Synthesis and Stereochemical Assignment of Delavatine A: Rh-Catalyzed Asymmetric Hydrogenation of Indene-Type Tetrasubstituted Olefins and Kinetic Resolution through Pd-Catalyzed Triflamide-Directed C-H Olefination.

    Science.gov (United States)

    Zhang, Zhongyin; Wang, Jinxin; Li, Jian; Yang, Fan; Liu, Guodu; Tang, Wenjun; He, Weiwei; Fu, Jian-Jun; Shen, Yun-Heng; Li, Ang; Zhang, Wei-Dong

    2017-04-19

    Delavatine A (1) is a structurally unusual isoquinoline alkaloid isolated from Incarvillea delavayi. The first and gram-scale total synthesis of 1 was accomplished in 13 steps (the longest linear sequence) from commercially available starting materials. We exploited an isoquinoline construction strategy and developed two reactions, namely Rh-catalyzed asymmetric hydrogenation of indene-type tetrasubstituted olefins and kinetic resolution of β-alkyl phenylethylamine derivatives through Pd-catalyzed triflamide-directed C-H olefination. The substrate scope of the first reaction covered unfunctionalized olefins and those containing polar functionalities such as sulfonamides. The kinetic resolution provided a collection of enantioenriched indane- and tetralin-based triflamides, including those bearing quaternary chiral centers. The selectivity factor (s) exceeded 100 for a number of substrates. These reactions enabled two different yet related approaches to a key intermediate 28 in excellent enantiopurity. In the synthesis, the triflamide served as not only an effective directing group for C-H bond activation but also a versatile functional group for further elaborations. The relative and absolute configurations of delavatine A were unambiguously assigned by the syntheses of the natural product and its three stereoisomers. Their cytotoxicity against a series of cancer cell lines was evaluated.

  15. Alternative routes to olefins. Chances and challenges

    Energy Technology Data Exchange (ETDEWEB)

    Meiswinkel, A.; Delhomme, C.; Ponceau, M. [Linde AG, Pullach (Germany)

    2013-11-01

    In the future, conventional raw materials which are used for the production of olefins will get shorter and more expensive and alternative raw materials and production routes will gain importance. Natural gas, coal, shale oil or bio-mass are potential sources for the production of olefins, especially ethylene and propylene, as major base chemicals. Several potential production routes were already developed in the past, but cost, energy and environmental considerations might make these unattractive or unfeasible in comparison to traditional processes (e.g. steam cracking). Other processes such as methanol to olefins processes were successfully developed and first commercial units are running. In addition, combination of traditional processes (e.g. coal/biomass gasification, Fischer-Tropsch and steam cracking) might enable new pathways. Besides, dehydration of ethanol is opening direct routes from biomass to 'green' ethylene. However, for these 'bio-routes', feedstock availability and potential land use conflict with food production (sugar cane, wheat,..) still need to be evaluated. finally, new oxidative routes, including processes such as oxidative coupling of methane or oxidative dehydrogenation, are still at an early development stage but present potential for future industrial applications. (orig.) (Published in summary form only)

  16. Rare-earth-metal nitridophosphates through high-pressure metathesis

    International Nuclear Information System (INIS)

    Kloss, Simon David; Schnick, Wolfgang

    2015-01-01

    Developing a synthetic method to target an broad spectrum of unknown phases can lead to fascinating discoveries. The preparation of the first rare-earth-metal nitridophosphate LiNdP_4N_8 is reported. High-pressure solid-state metathesis between LiPN_2 and NdF_3 was employed to yield a highly crystalline product. The in situ formed LiF is believed to act both as the thermodynamic driving force and as a flux to aiding single-crystal formation in dimensions suitable for crystal structure analysis. Magnetic properties stemming from Nd"3"+ ions were measured by SQUID magnetometry. LiNdP_4N_8 serves as a model system for the exploration of rare-earth-metal nitridophosphates that may even be expanded to transition metals. High-pressure metathesis enables the systematic study of these uncharted regions of nitride-based materials with unprecedented properties. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  17. Well-defined silica-supported zirconium–imido complexes mediated heterogeneous imine metathesis

    KAUST Repository

    Hamzaoui, Bilel

    2016-02-15

    Upon prolonged thermal exposure under vacuum, a well-defined single-site surface species [(≡Si-O-)Zr(NEt2)3] (1) evolves into an ethylimido complex [(≡Si-O-)Zr(=NEt)NEt2] (2). Reactions of 2 with an imine substrate result in imido/imine (=NRi, R: Et, Ph) exchange (metathesis) with the formation of [(≡Si-O-)Zr(=NPh)NEt2] (3). Compounds 2 and 3 effectively catalyze imine/imine cross-metathesis and are thus considered as the first heterogeneous catalysts active for imine metathesis. © The Royal Society of Chemistry 2016.

  18. Well-defined silica-supported zirconium–imido complexes mediated heterogeneous imine metathesis

    KAUST Repository

    Hamzaoui, Bilel; Pelletier, Jeremie; Abou-Hamad, Edy; Basset, Jean-Marie

    2016-01-01

    Upon prolonged thermal exposure under vacuum, a well-defined single-site surface species [(≡Si-O-)Zr(NEt2)3] (1) evolves into an ethylimido complex [(≡Si-O-)Zr(=NEt)NEt2] (2). Reactions of 2 with an imine substrate result in imido/imine (=NRi, R: Et, Ph) exchange (metathesis) with the formation of [(≡Si-O-)Zr(=NPh)NEt2] (3). Compounds 2 and 3 effectively catalyze imine/imine cross-metathesis and are thus considered as the first heterogeneous catalysts active for imine metathesis. © The Royal Society of Chemistry 2016.

  19. Gelation induced supramolecular chirality: chirality transfer, amplification and application.

    Science.gov (United States)

    Duan, Pengfei; Cao, Hai; Zhang, Li; Liu, Minghua

    2014-08-14

    Supramolecular chirality defines chirality at the supramolecular level, and is generated from the spatial arrangement of component molecules assembling through non-covalent interactions such as hydrogen bonding, van der Waals interactions, π-π stacking, hydrophobic interactions and so on. During the formation of low molecular weight gels (LMWGs), one kind of fascinating soft material, one frequently encounters the phenomenon of chirality as well as chiral nanostructures, either from chiral gelators or even achiral gelators. A view of gelation-induced supramolecular chirality will be very helpful to understand the self-assembly process of the gelator molecules as well as the chiral structures, the regulation of the chirality in the gels and the development of the "smart" chiral materials such as chiroptical devices, catalysts and chiral sensors. It necessitates fundamental understanding of chirality transfer and amplification in these supramolecular systems. In this review, recent progress in gelation-induced supramolecular chirality is discussed.

  20. Mechanical separation of chiral dipoles by chiral light

    International Nuclear Information System (INIS)

    Canaguier-Durand, Antoine; Hutchison, James A; Genet, Cyriaque; Ebbesen, Thomas W

    2013-01-01

    We calculate optical forces and torques exerted on a chiral dipole by chiral light fields and reveal genuine chiral forces in combining the chiral contents of both light field and dipolar matter. Here, the optical chirality is characterized in a general way through the definition of optical chirality density and chirality flow. We show, in particular, that both terms have mechanical effects associated, respectively, with reactive and dissipative components of the chiral forces. Remarkably, these chiral force components are directly related to standard observables: optical rotation for the reactive component and circular dichroism for the dissipative one. As a consequence, the resulting forces and torques are dependent on the enantiomeric form of the chiral dipole. This suggests promising strategies for using chiral light forces to mechanically separate chiral objects according to their enantiomeric form. (paper)

  1. Active chiral fluids.

    Science.gov (United States)

    Fürthauer, S; Strempel, M; Grill, S W; Jülicher, F

    2012-09-01

    Active processes in biological systems often exhibit chiral asymmetries. Examples are the chirality of cytoskeletal filaments which interact with motor proteins, the chirality of the beat of cilia and flagella as well as the helical trajectories of many biological microswimmers. Here, we derive constitutive material equations for active fluids which account for the effects of active chiral processes. We identify active contributions to the antisymmetric part of the stress as well as active angular momentum fluxes. We discuss four types of elementary chiral motors and their effects on a surrounding fluid. We show that large-scale chiral flows can result from the collective behavior of such motors even in cases where isolated motors do not create a hydrodynamic far field.

  2. Synthetic studies on taxanes: A domino-enyne metathesis/Diels ...

    Indian Academy of Sciences (India)

    Abstract. A domino enyne cross-metathesis/intramolecular Diels-Alder reaction has been successfully used to synthesize a bicyclo[5.3.1] undecene, corresponding to AB-ring of taxol without the gem dimethyl group.

  3. A cross-metathesis approach to the stereocontrolled synthesis of the AB ring segment of ciguatoxin

    OpenAIRE

    Kadota, Isao; Abe, Takashi; Uni, Miyuki; Takamura, Hiroyoshi; Yamamoto, Yoshinori

    2008-01-01

    Synthesis of the AB ring segments of ciguatoxin is described. The present synthesis includes a Lewis acid mediated cyclization of allylstannane with aldehyde, cross-metathesis reaction introducing the side chain, and Grieco-Nishizawa dehydration on the A ring.

  4. 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.

  5. Selective conversion of butane into liquid hydrocarbon fuels on alkane metathesis catalysts

    KAUST Repository

    Szeto, Kaï Chung; Hardou, Lucie; Merle, Nicolas; Basset, Jean-Marie; Thivolle-Cazat, Jean; Papaioannou, Charalambos; Taoufik, Mostafa

    2012-01-01

    We report a selective direct conversion of n-butane into higher molecular weight alkanes (C 5+) by alkane metathesis reaction catalysed by silica-alumina supported tungsten or tantalum hydrides at moderate temperature and pressure. The product

  6. Surface-enhanced light olefin yields during steam cracking

    NARCIS (Netherlands)

    Golombok, M.; Kornegoor, M.; Brink, van den P.; Dierickx, J.; Grotenbreg, R.

    2000-01-01

    Various papers have shown enhanced olefin yields during steam cracking when a catalytic surface is introduced. Our studies reveal that increased light olefin yields during catalytic steam cracking are mainly due to a surface volume effect and not to a traditional catalytic effect. Augmentation of

  7. Alkylation of isobutane with light olefins catalyzed by zeolite beta

    NARCIS (Netherlands)

    Nivarthy, G.S.; Feller, A.P.; Seshan, Kulathuiyer; Lercher, J.A.

    2000-01-01

    Alkylation of isobutane with ethene and propene was studied over an H-BEA catalyst in a well-stirred reactor. Under similar conditions of space velocity and paraffin-to-olefin feed ratio, lower initial olefin conversions were observed with ethene or propene than those reported earlier for butene.

  8. Rhodium(iii)-catalyzed ortho-olefination of aryl phosphonates.

    Science.gov (United States)

    Chary, Bathoju Chandra; Kim, Sunggak

    2013-09-25

    Rhodium(iii)-catalyzed C-H olefination of aryl phosphonic esters is reported for the first time. In this mild and efficient process, the phosphonic ester group is utilized successfully as a new directing group. In addition, mono-olefination for aryl phosphonates is observed using a phosphonic diamide directing group.

  9. 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.

  10. 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; Mazoyer, Etienne; Merle, Nicolas; Norsic, Sé bastien; Basset, Jean-Marie; Nicholas, Christopher P.; Taoufik, Mostafa

    2013-01-01

    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.

  11. Competitive chiral induction in a 2D molecular assembly: Intrinsic chirality versus coadsorber-induced chirality.

    Science.gov (United States)

    Chen, Ting; Li, Shu-Ying; Wang, Dong; Wan, Li-Jun

    2017-11-01

    Noncovalently introducing stereogenic information is a promising approach to embed chirality in achiral molecular systems. However, the interplay of the noncovalently introduced chirality with the intrinsic chirality of molecules or molecular aggregations has rarely been addressed. We report a competitive chiral expression of the noncovalent interaction-mediated chirality induction and the intrinsic stereogenic center-controlled chirality induction in a two-dimensional (2D) molecular assembly at the liquid/solid interface. Two enantiomorphous honeycomb networks are formed by the coassembly of an achiral 5-(benzyloxy)isophthalic acid (BIC) derivative and 1-octanol at the liquid/solid interface. The preferential formation of the globally homochiral assembly can be achieved either by using the chiral analog of 1-octanol, ( S )-6-methyl-1-octanol, as a chiral coadsorber to induce chirality to the BIC assembly via noncovalent hydrogen bonding or by covalently linking a chiral center in the side chain of BIC. Both the chiral coadsorber and the intrinsically chiral BIC derivative can act as a chiral seeds to induce a preferred handedness in the assembly of the achiral BIC derivatives. Furthermore, the noncovalent interaction-mediated chirality induction can restrain or even overrule the manifestation of the intrinsic chirality of the BIC molecule and dominate the handedness of the 2D molecular coassembly. This study provides insight into the interplay of intrinsically chiral centers and external chiral coadsorbers in the chiral induction, transfer, and amplification processes of 2D molecular assembly.

  12. Rhodium(I) catalysis in olefin photoreactions

    International Nuclear Information System (INIS)

    Salomon, R.G.; El Sanadi, N.

    1975-01-01

    The photorearrangement (254 nm) of 1,5-cyclooctadiene (1) in the presence of rhodium(I) chloride to give 1,4-cyclooctadiene (4) was found by deuterium labeling to involve an intramolecular [1,3] shift of hydrogen. A rate-determining cleavage of an allylic C--H bond is indicated by a deuterium isotope effect, k/sub H//k/sub D/ = 1.55 +- 0.03 for the 1 → 4 rearrangement. The acyclic 1,5-diene, 3,3-dimethyl-1,5-hexadiene (8), rearranges in the presence of rhodium(I) chloride upon uv irradiation (254 nm) to give cis-3,3-dimethyl-1,4-hexadiene (10) and the trans isomer 11 in a 1:4 ratio, respectively. This observation supports a mechanism for the photorearrangement of olefins catalyzed by rhodium(I) involving an initial photodissociation of one of two rhodium(I) coordinated carbon-carbon double bonds. This results in an increase in the coordinative unsaturation of rhodium(I) and enhances the proclivity of this d/sub s/ metal atom toward oxidative addition of an allylic C--H bond. A eta 3 -allylrhodium hydride intermediate then gives rearranged olefin by reductive elimination. Lastly, a novel photochemical, rhodium(I) catalyzed hydrogen transfer is reported which gives cyclooctene (7) from cyclooctadienes under unprecedentedly mild conditions. (auth)

  13. A method for producing lower olefins

    Energy Technology Data Exchange (ETDEWEB)

    Lemayev, N.V.; Grigorovich, V.A.; Isayev, V.A.; Liakumovich, A.G.; Mitrofanov, A.I.; Orekhov, A.I.; Trifonov, S.V.; Vernov, P.A.

    1983-01-01

    In the known method for producing lower olefins by pyrolysis of a hydrocarbon raw material in the presence of an initiator which contains ammonia, in order to increase the output of the target products, morpholine or piperidine are additionally introduced into the initiator in a volume of 0.00001 to 0.1 percent each, converted for the raw material. The compounds to be added may be introduced into the pyrolysis zone by dissolving them in the hydrocarbon raw material or in water, which forms vapors with dilution of the raw material being subjected to pyrolysis. The increase in the outputs of the lower olefins in the process through the use of additives may be explained by the synergistic effect of the mixture of ammonia, morpholine and piperidine used. With benzine pyrolysis without the additives the output of ethylene is 24.1 percent; in comparable conditions with additives of ammonia or morpholine alone, or of piperidine alone, the outputs are 24.0, 26.2 and 25.8 percent, respectively. With the joint presence of ammonia and piperidine, the output of ethylene reaches 27.2 percent and with the addition of ammonia and morpholine, it reaches 27.4 percent.

  14. Siegel's chiral boson and the chiral Schwinger model

    International Nuclear Information System (INIS)

    Berger, T.

    1992-01-01

    In this paper Siegel's proposal for a Lagrangian formulation of a chiral boson is analyzed by applying recent results on 2d chiral quantum gravity. A model is derived whose solution consists of a massive scalar and two massless chiral scalars. Therefore it is a minimally bosonized two-fermion chiral Schwinger model

  15. Observation of chiral phonons

    KAUST Repository

    Zhu, Hanyu; Yi, Jun; Li, Ming-yang; Xiao, Jun; Zhang, Lifa; Yang, Chih-Wen; Kaindl, Robert A.; Li, Lain-Jong; Wang, Yuan; Zhang, Xiang

    2018-01-01

    Chirality reveals symmetry breaking of the fundamental interaction of elementary particles. In condensed matter, for example, the chirality of electrons governs many unconventional transport phenomena such as the quantum Hall effect. Here we show that phonons can exhibit intrinsic chirality in monolayer tungsten diselenide. The broken inversion symmetry of the lattice lifts the degeneracy of clockwise and counterclockwise phonon modes at the corners of the Brillouin zone. We identified the phonons by the intervalley transfer of holes through hole-phonon interactions during the indirect infrared absorption, and we confirmed their chirality by the infrared circular dichroism arising from pseudoangular momentum conservation. The chiral phonons are important for electron-phonon coupling in solids, phonon-driven topological states, and energy-efficient information processing.

  16. Observation of chiral phonons

    KAUST Repository

    Zhu, Hanyu

    2018-02-01

    Chirality reveals symmetry breaking of the fundamental interaction of elementary particles. In condensed matter, for example, the chirality of electrons governs many unconventional transport phenomena such as the quantum Hall effect. Here we show that phonons can exhibit intrinsic chirality in monolayer tungsten diselenide. The broken inversion symmetry of the lattice lifts the degeneracy of clockwise and counterclockwise phonon modes at the corners of the Brillouin zone. We identified the phonons by the intervalley transfer of holes through hole-phonon interactions during the indirect infrared absorption, and we confirmed their chirality by the infrared circular dichroism arising from pseudoangular momentum conservation. The chiral phonons are important for electron-phonon coupling in solids, phonon-driven topological states, and energy-efficient information processing.

  17. Chiral Spirals from Discontinuous Chiral Symmetry

    Science.gov (United States)

    Kojo, Toru

    2014-09-01

    Recently phases of the inhomongeneous chiral condensates (IChC) attract renewed attentions in quark matter context. A number of theoretical studies have suggested that in some domain of moderate quark density the IChC phases are energetically more favored than the normal, chiral symmetric phase. In particular, the NJL-type model studies indicate that the phase of IChCs may mask the usual 1st order chiral phase transition line and its critical end point, and might change the conventional wisdom. In this talk, I will discuss characteristic features of the IChC phases and their potential impacts on the compact star physics. In particular, some of the IChC phases open gaps near the quark Fermi surface, suppressing back-reaction from the quark to gluon sectors. This mechanism delays the chiral restoration in the strange quark sector, forbids the emergence of the large bag constant, and as a consequence, makes the quark matter EOS very stiff. Recently phases of the inhomongeneous chiral condensates (IChC) attract renewed attentions in quark matter context. A number of theoretical studies have suggested that in some domain of moderate quark density the IChC phases are energetically more favored than the normal, chiral symmetric phase. In particular, the NJL-type model studies indicate that the phase of IChCs may mask the usual 1st order chiral phase transition line and its critical end point, and might change the conventional wisdom. In this talk, I will discuss characteristic features of the IChC phases and their potential impacts on the compact star physics. In particular, some of the IChC phases open gaps near the quark Fermi surface, suppressing back-reaction from the quark to gluon sectors. This mechanism delays the chiral restoration in the strange quark sector, forbids the emergence of the large bag constant, and as a consequence, makes the quark matter EOS very stiff. NSF Grants PHY09-69790, PHY13-05891.

  18. Geometrical approach to central molecular chirality: a chirality selection rule

    OpenAIRE

    Capozziello, S.; Lattanzi, A.

    2004-01-01

    Chirality is of primary importance in many areas of chemistry and has been extensively investigated since its discovery. We introduce here the description of central chirality for tetrahedral molecules using a geometrical approach based on complex numbers. According to this representation, for a molecule having n chiral centres, it is possible to define an index of chirality. Consequently a chirality selection rule has been derived which allows the characterization of a molecule as achiral, e...

  19. SAXS observation of structural evolution of heated olefin

    International Nuclear Information System (INIS)

    Sun Minhua; Mou Hongchen; Wang Yuxi; Li Demin; Wang Aiping; Ma Congxiao; Cheng Weidong; Wang Dan; Liu Jia

    2007-01-01

    Structural evolution of olefin during its heating process was observed with SAXS method at Beijing Synchrotron Radiation Facility. The mean square fluctuation of electron density increased from 468.5 nm -2 at 22 degree C to 2416 nm -2 at 100 degree C, while the electronic gyration radius decreased from 11.61 nm at 22 degree C to 11.16 nm at 100 degree C. Therefore, the olefin softens as a result of the increased thermal motion of the molecules, rather than the shrinking size of fundamental structural units of olefin. (authors)

  20. Reactions of dihydridotetrakis(triphenylphosphine)ruthenium(II) with olefins and isolation of new ruthenium-olefin complexes

    International Nuclear Information System (INIS)

    Komiya, Sanshiro; Yamamoto, Akio

    1976-01-01

    Dihydridotetrakis(triphenylphosphine)ruthenium (II), RuH 2 (PPh 3 ) 4 , reacts with olefins (ethylene, propylene, stylene and butadiene) to give olefin-coordinated complexes of the type, Ru(olefin)(PPh 3 ) 3 and equimolar amounts of their hydrogenation products per mol of the dihydride complex. The olefin coordinated with ruthenium can be exchanged with other olefins. Olefin-coordinated complexes easily react with molecular hydrogen to afford tetrahydridotris(triphenylphosphine)ruthenium, RuH 4 (PPh 3 ) 3 , releasing alkane at room temperature, Under hydrogen atmosphere catalytic hydrogenation of the olefins smoothly takes place with RuH 2 (PPh 3 ) 4 . (Ethylene)tris(triphenylphosphine)ruthenium(0) reacts with methyl iodide to give propylene and a trace of butadiene along with methane, ethylene, and small amounts of ethane and butenes. The formation of propylene suggests that oxidative addition involving cleavage of the C-H bond of ethylene to ruthenium giving a hydridovinyl complex may be taking place. Reactions of Ru(C 2 H 4 )(PPh 3 ) 3 with methyl-d 3 iodide and ethyl iodide, and of Ru(C 3 H 6 )(PPh 3 ) 3 with methyl iodide were examined to test the generality of this type of reaction. The reaction of Ru(C 2 H 4 )(PPh 3 ) 3 with CD 3 I released CD 4 and CD 2 H 2 together with CD 3 H suggesting the involvement of α-hydrogen abstraction. (auth.)

  1. Applications of chiral symmetry

    International Nuclear Information System (INIS)

    Pisarski, R.D.

    1995-03-01

    The author discusses several topics in the applications of chiral symmetry at nonzero temperature. First, where does the rho go? The answer: up. The restoration of chiral symmetry at a temperature T χ implies that the ρ and a 1 vector mesons are degenerate in mass. In a gauged linear sigma model the ρ mass increases with temperature, m ρ (T χ ) > m ρ (0). The author conjectures that at T χ the thermal ρ - a 1 , peak is relatively high, at about ∼1 GeV, with a width approximately that at zero temperature (up to standard kinematic factors). The ω meson also increases in mass, nearly degenerate with the ρ, but its width grows dramatically with temperature, increasing to at least ∼100 MeV by T χ . The author also stresses how utterly remarkable the principle of vector meson dominance is, when viewed from the modern perspective of the renormalization group. Secondly, he discusses the possible appearance of disoriented chiral condensates from open-quotes quenchedclose quotes heavy ion collisions. It appears difficult to obtain large domains of disoriented chiral condensates in the standard two flavor model. This leads to the last topic, which is the phase diagram for QCD with three flavors, and its proximity to the chiral critical point. QCD may be very near this chiral critical point, and one might thereby generated large domains of disoriented chiral condensates

  2. Chiral bag model

    International Nuclear Information System (INIS)

    Musakhanov, M.M.

    1980-01-01

    The chiral bag model is considered. It is suggested that pions interact only with the surface of a quark ''bag'' and do not penetrate inside. In the case of a large bag the pion field is rather weak and goes to the linearized chiral bag model. Within that model the baryon mass spectrum, β decay axial constant, magnetic moments of baryons, pion-baryon coupling constants and their form factors are calculated. It is shown that pion corrections to the calculations according to the chiral bag model is essential. The obtained results are found to be in a reasonable agreement with the experimental data

  3. The covariant chiral ring

    Energy Technology Data Exchange (ETDEWEB)

    Bourget, Antoine; Troost, Jan [Laboratoire de Physique Théorique, École Normale Supérieure, 24 rue Lhomond, 75005 Paris (France)

    2016-03-23

    We construct a covariant generating function for the spectrum of chiral primaries of symmetric orbifold conformal field theories with N=(4,4) supersymmetry in two dimensions. For seed target spaces K3 and T{sup 4}, the generating functions capture the SO(21) and SO(5) representation theoretic content of the chiral ring respectively. Via string dualities, we relate the transformation properties of the chiral ring under these isometries of the moduli space to the Lorentz covariance of perturbative string partition functions in flat space.

  4. Spectral signatures of chirality

    DEFF Research Database (Denmark)

    Pedersen, Jesper Goor; Mortensen, Asger

    2009-01-01

    We present a new way of measuring chirality, via the spectral shift of photonic band gaps in one-dimensional structures. We derive an explicit mapping of the problem of oblique incidence of circularly polarized light on a chiral one-dimensional photonic crystal with negligible index contrast...... to the formally equivalent problem of linearly polarized light incident on-axis on a non-chiral structure with index contrast. We derive analytical expressions for the first-order shifts of the band gaps for negligible index contrast. These are modified to give good approximations to the band gap shifts also...

  5. Chiral near-fields around chiral dolmen nanostructure

    International Nuclear Information System (INIS)

    Fu, Tong; Wang, Tiankun; Chen, Yuyan; Wang, Yongkai; Qu, Yu; Zhang, Zhongyue

    2017-01-01

    Discriminating the handedness of the chiral molecule is of great importance in the field of pharmacology and biomedicine. Enhancing the chiral near-field is one way to increase the chiral signal of chiral molecules. In this paper, the chiral dolmen nanostructure (CDN) is proposed to enhance the chiral near-field. Numerical results show that the CDN can increase the optical chirality of the near-field by almost two orders of magnitude compared to that of a circularly polarized incident wave. In addition, the optical chirality of the near-field of the bonding mode is enhanced more than that of the antibonding mode. These results provide an effective method for tailoring the chiral near-field for biophotonics sensors. (paper)

  6. Cobalt catalyzed hydroesterification of a wide range of olefins

    Energy Technology Data Exchange (ETDEWEB)

    Van Rensburg, H.; Hanton, M.; Tooze, R.P.; Foster, D.F. [Sasol Technology UK, St Andrews (United Kingdom)

    2011-07-01

    Petrochemical raw materials are an essential raw material for the production of detergents with a substantial portion of synthetic fatty alcohols being produced via hydroformylation of oil or coal derived olefins. Carbonylation processes other than hydroformylation have to date not been commercially employed for the production of fatty esters or alcohols. In this document we highlight the opportunities of converting olefins to esters using cobalt catalyzed alkoxycarbonylation. This process is highly versatile and applicable to a wide range of olefins, linear or branched, alpha or internal in combination with virtually any chain length primary or secondary alcohol allowing the synthesis of a diverse array of compounds such as ester ethoxylated surfactants, methyl branched detergents, lubricants and alkyl propanoates. Furthermore, alkoxycarbonylation of a broad olefin/paraffin hydrocarbon range could be used to produce the corresponding broad cut detergent alcohols. (orig.)

  7. Olefin copolymerization via reversible addition-fragmentation chain transfer

    NARCIS (Netherlands)

    Venkatesh, R.; Staal, B.B.P.; Klumperman, B.

    2004-01-01

    Successful statistical copolymn. of an a-olefin (1-octene) with an acrylate (Bu acrylate, BA) and with a methacrylate (Me methacrylate, MMA), employing reversible addn.-fragmentation chain transfer (RAFT) mediated polymn. has been accomplished

  8. Direct observation of OH production from the ozonolysis of olefins

    Science.gov (United States)

    Donahue, Neil M.; Kroll, Jesse H.; Anderson, James G.; Demerjian, Kenneth L.

    Ozone olefin reactions may be a significant source of OH in the urban atmosphere, but current evidence for OH production is indirect and contested. We report the first direct observation of OH radicals from the reaction of ozone with a series of olefins (ethene, isoprene, trans-2-butene and 2,3 dimethyl-2-butene) in 4-6 torr of nitrogen. Using LIF to directly observe the steady-state of OH produced by the initial ozone-olefin reaction and subsequently destroyed by the OH-olefin reaction, we are able to establish OH yields broadly consistent with indirect values. The identification of the OH is unequivocal, and there is no indication that it is produced by a secondary process. To support these observations, we present a complete ab-initio potential energy surface for the O3-ethene reaction, extending from the reactants to available products.

  9. Olefins and chemical regulation in Europe: REACH.

    Science.gov (United States)

    Penman, Mike; Banton, Marcy; Erler, Steffen; Moore, Nigel; Semmler, Klaus

    2015-11-05

    REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals) is the European Union's chemical regulation for the management of risk to human health and the environment (European Chemicals Agency, 2006). This regulation entered into force in June 2007 and required manufacturers and importers to register substances produced in annual quantities of 1000 tonnes or more by December 2010, with further deadlines for lower tonnages in 2013 and 2018. Depending on the type of registration, required information included the substance's identification, the hazards of the substance, the potential exposure arising from the manufacture or import, the identified uses of the substance, and the operational conditions and risk management measures applied or recommended to downstream users. Among the content developed to support this information were Derived No-Effect Levels or Derived Minimal Effect Levels (DNELs/DMELs) for human health hazard assessment, Predicted No Effect Concentrations (PNECs) for environmental hazard assessment, and exposure scenarios for exposure and risk assessment. Once registered, substances may undergo evaluation by the European Chemicals Agency (ECHA) or Member State authorities and be subject to requests for additional information or testing as well as additional risk reduction measures. To manage the REACH registration and related activities for the European olefins and aromatics industry, the Lower Olefins and Aromatics REACH Consortium was formed in 2008 with administrative and technical support provided by Penman Consulting. A total of 135 substances are managed by this group including 26 individual chemical registrations (e.g. benzene, 1,3-butadiene) and 13 categories consisting of 5-26 substances. This presentation will describe the content of selected registrations prepared for 2010 in addition to the significant post-2010 activities. Beyond REACH, content of the registrations may also be relevant to other European activities, for

  10. Chiral Gold Nanoclusters: Atomic Level Origins of Chirality.

    Science.gov (United States)

    Zeng, Chenjie; Jin, Rongchao

    2017-08-04

    Chiral nanomaterials have received wide interest in many areas, but the exact origin of chirality at the atomic level remains elusive in many cases. With recent significant progress in atomically precise gold nanoclusters (e.g., thiolate-protected Au n (SR) m ), several origins of chirality have been unveiled based upon atomic structures determined by using single-crystal X-ray crystallography. The reported chiral Au n (SR) m structures explicitly reveal a predominant origin of chirality that arises from the Au-S chiral patterns at the metal-ligand interface, as opposed to the chiral arrangement of metal atoms in the inner core (i.e. kernel). In addition, chirality can also be introduced by a chiral ligand, manifested in the circular dichroism response from metal-based electronic transitions other than the ligand's own transition(s). Lastly, the chiral arrangement of carbon tails of the ligands has also been discovered in a very recent work on chiral Au 133 (SR) 52 and Au 246 (SR) 80 nanoclusters. Overall, the origins of chirality discovered in Au n (SR) m nanoclusters may provide models for the understanding of chirality origins in other types of nanomaterials and also constitute the basis for the development of various applications of chiral nanoparticles. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Pure chiral optical fibres.

    Science.gov (United States)

    Poladian, L; Straton, M; Docherty, A; Argyros, A

    2011-01-17

    We investigate the properties of optical fibres made from chiral materials, in which a contrast in optical activity forms the waveguide, rather than a contrast in the refractive index; we refer to such structures as pure chiral fibres. We present a mathematical formulation for solving the modes of circularly symmetric examples of such fibres and examine the guidance and polarisation properties of pure chiral step-index, Bragg and photonic crystal fibre designs. Their behaviour is shown to differ for left- and right-hand circular polarisation, allowing circular polarisations to be isolated and/or guided by different mechanisms, as well as differing from equivalent non-chiral fibres. The strength of optical activity required in each case is quantified.

  12. Relativistic Chiral Kinetic Theory

    International Nuclear Information System (INIS)

    Stephanov, Mikhail

    2016-01-01

    This very brief review of the recent progress in chiral kinetic theory is based on the results of Refs. [J.-Y. Chen, D. T. Son, M. A. Stephanov, H.-U. Yee, Y. Yin, Lorentz Invariance in Chiral Kinetic Theory, Phys. Rev. Lett. 113 (18) (2014) 182302. doi: (10.1103/PhysRevLett.113.182302); J.-Y. Chen, D. T. Son, M. A. Stephanov, Collisions in Chiral Kinetic Theory, Phys. Rev. Lett. 115 (2) (2015) 021601. doi: (10.1103/PhysRevLett.115.021601); M. A. Stephanov, H.-U. Yee, The no-drag frame for anomalous chiral fluid, Phys. Rev. Lett. 116 (12) (2016) 122302. doi: (10.1103/PhysRevLett.116.122302)].

  13. Relativistic Chiral Kinetic Theory

    Energy Technology Data Exchange (ETDEWEB)

    Stephanov, Mikhail

    2016-12-15

    This very brief review of the recent progress in chiral kinetic theory is based on the results of Refs. [J.-Y. Chen, D. T. Son, M. A. Stephanov, H.-U. Yee, Y. Yin, Lorentz Invariance in Chiral Kinetic Theory, Phys. Rev. Lett. 113 (18) (2014) 182302. doi: (10.1103/PhysRevLett.113.182302); J.-Y. Chen, D. T. Son, M. A. Stephanov, Collisions in Chiral Kinetic Theory, Phys. Rev. Lett. 115 (2) (2015) 021601. doi: (10.1103/PhysRevLett.115.021601); M. A. Stephanov, H.-U. Yee, The no-drag frame for anomalous chiral fluid, Phys. Rev. Lett. 116 (12) (2016) 122302. doi: (10.1103/PhysRevLett.116.122302)].

  14. Baryon Chiral Dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Becher,

    2002-08-08

    After contrasting the low energy effective theory for the baryon sector with one for the Goldstone sector, I use the example of pion nucleon scattering to discuss some of the progress and open issues in baryon chiral perturbation theory.

  15. Generalized chiral perturbation theory

    International Nuclear Information System (INIS)

    Knecht, M.; Stern, J.

    1994-01-01

    The Generalized Chiral Perturbation Theory enlarges the framework of the standard χPT (Chiral Perturbation Theory), relaxing certain assumptions which do not necessarily follow from QCD or from experiment, and which are crucial for the usual formulation of the low energy expansion. In this way, experimental tests of the foundations of the standard χPT become possible. Emphasis is put on physical aspects rather than on formal developments of GχPT. (author). 31 refs

  16. Generalized chiral membrane dynamics

    International Nuclear Information System (INIS)

    Cordero, R.; Rojas, E.

    2003-01-01

    We develop the dynamics of the chiral superconducting membranes (with null current) in an alternative geometrical approach. Besides of this, we show the equivalence of the resulting description with the one known Dirac-Nambu-Goto (DNG) case. Integrability for chiral string model is obtained using a proposed light-cone gauge. In a similar way, domain walls are integrated by means of a simple Ansatz. (Author)

  17. Quenched chiral logarithms

    International Nuclear Information System (INIS)

    Sharpe, S.R.

    1992-04-01

    I develop a diagrammatic method for calculating chiral logarithms in the quenched approximation. While not rigorous, the method is based on physically reasonable assumptions, which can be tested by numerical simulations. The main results are that, at leading order in the chiral expansion, (a) there are no chiral logarithms in quenched f π m u = m d ; (b) the chiral logarithms in B K and related kaon B-parameters are, for m d = m s the same in the quenched approximation as in the full theory (c) for m π and the condensate, there are extra chiral logarithms due to loops containing the η', which lead to a peculiar non-analytic dependence of these quantities on the bare quark mass. Following the work of Gasser and Leutwyler, I discuss how there is a predictable finite volume dependence associated with each chiral logarithm. I compare the resulting predictions with numerical results: for most quantities the expected volume dependence is smaller than the errors. but for B V and B A there is an observed dependence which is consistent with the predictions

  18. Rh(III)-catalyzed oxidative olefination of N-(1-naphthyl)sulfonamides using activated and unactivated alkenes.

    Science.gov (United States)

    Li, Xuting; Gong, Xue; Zhao, Miao; Song, Guoyong; Deng, Jian; Li, Xingwei

    2011-11-04

    Rhodium(III)-catalyzed oxidative olefination of N-(1-naphthyl)sulfonamides has been achieved at the peri position. Three categories of olefins have been successfully applied. Activated olefins reacted to afford five-membered azacycles as a result of oxidative olefination-hydroamination. Unactivated olefins reacted to give the olefination product. 2-fold oxidative C-C and C-N coupling was achieved for allylbenzenes. © 2011 American Chemical Society

  19. A method for producing light olefines

    Energy Technology Data Exchange (ETDEWEB)

    Kavada, N.; Katsuno, K.

    1982-11-04

    A method is proposed for producing light olefins from MeOH in the presence of a catalyst (Kt), a crystalline silicate which includes silicon, an alkaline and or alkaline earth metal, titanium(4+) and phosphorus(5+), whose composition is described by the formula p(019 plus or minus 0.3)M2/mO with pZ4/nO2 with SiO2, where M is the alkaline or alkaline earth metal, Z = titanium(4+) or phosphorus(5+), m is the valency of the metal, n is the valency of Z and O is less than p is less than or equal to 0.1. A high selectivity of MeOH to C2 to C4 olefins is achieved in the presence of the catalyst. Silicon powder, silica gel, colloidal silicon, liquid glass or silicates of alkaline metals in a ratio of SiO2 to M2O of 1 to 5 is used as the source of the first component. Hydroxides or silicates of potassium and sodium (best sodium) and nitrates or chlorides of alkaline earth metals (best calcium) are used as the source of the second component. Water soluble compounds of titanium(4+) (best Ti(SO4)2, TiBr4 and TiI4) and phosphorus(5+) (best H3PO4, Na3PO4) are used as the source of the third component. Heterocyclic compounds (best morpholine, oxazolidine and their derivatives, which are taken in a molar ratio of crystallization agent to SiO2 of 0.01 to 50 (best at 0.1 to 10), are used as the crystallization agent (ArK). The catalyst is prepared through heating in an autoclave at a temperature of 80 to 300 degrees (best at 120 to 200 degrees) at atmospheric pressure for 10 to 50 hours with mixing of the mixture of the three components, water and the crystallization agent. The forming crystalline product is cooled, poured off, washed with water, dried for several hours at a temperature of at least 100 degrees and roasted in air for 2 to 48 hours at 300 to 700 degrees.

  20. Autoamplification of molecular chirality through the induction of supramolecular chirality

    NARCIS (Netherlands)

    van Dijken, Derk Jan; Beierle, John M.; Stuart, Marc C. A.; Szymanski, Wiktor; Browne, Wesley R.; Feringa, Ben L.

    2014-01-01

    The novel concept for the autoamplification of molecular chirality, wherein the amplification proceeds through the induction of supramolecular chirality, is presented. A solution of prochiral, ring-open diarylethenes is doped with a small amount of their chiral, ring-closed counterpart. The

  1. Algebraic study of chiral anomalies

    Indian Academy of Sciences (India)

    Chiral anomalies; gauge theories; bundles; connections; quantum field ... The algebraic structure of chiral anomalies is made globally valid on non-trivial bundles by the introduction of a fixed background connection. ... Current Issue : Vol.

  2. Silver Films with Hierarchical Chirality.

    Science.gov (United States)

    Ma, Liguo; Cao, Yuanyuan; Duan, Yingying; Han, Lu; Che, Shunai

    2017-07-17

    Physical fabrication of chiral metallic films usually results in singular or large-sized chirality, restricting the optical asymmetric responses to long electromagnetic wavelengths. The chiral molecule-induced formation of silver films prepared chemically on a copper substrate through a redox reaction is presented. Three levels of chirality were identified: primary twisted nanoflakes with atomic crystal lattices, secondary helical stacking of these nanoflakes to form nanoplates, and tertiary micrometer-sized circinates consisting of chiral arranged nanoplates. The chiral Ag films exhibited multiple plasmonic absorption- and scattering-based optical activities at UV/Vis wavelengths based on their hierarchical chirality. The Ag films showed chiral selectivity for amino acids in catalytic electrochemical reactions, which originated from their primary atomic crystal lattices. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Chiral anomalies and differential geometry

    International Nuclear Information System (INIS)

    Zumino, B.

    1983-10-01

    Some properties of chiral anomalies are described from a geometric point of view. Topics include chiral anomalies and differential forms, transformation properties of the anomalies, identification and use of the anomalies, and normalization of the anomalies. 22 references

  4. Proceedings of the DGMK-Conference 'Creating value from light olefins - production and conversion'. Authors' manuscripts

    Energy Technology Data Exchange (ETDEWEB)

    Emig, G; Kraemer, H J; Weitkamp, J [eds.

    2001-07-01

    Main topics of the conference were: production of light olefin by steamcracking and catalytic cracking processes, catalysts, methanol to olefin processes, oxidative dehydrogenation, partial oxidation, selective oxidation of alkanes with various catalysts. (uke)

  5. Primary Alcohols from Terminal Olefins: Formal Anti-Markovnikov Hydration via Triple Relay Catalysis

    KAUST Repository

    Dong, G.; Teo, P.; Wickens, Z. K.; Grubbs, R. H.

    2011-01-01

    Alcohol synthesis is critical to the chemical and pharmaceutical industries. The addition of water across olefins to form primary alcohols (anti-Markovnikov olefin hydration) would be a broadly useful reaction but has largely proven elusive

  6. Palladium-catalyzed Asymmetric Hydrosilylation of Styrene and Its Derivatives with Chiral Phosphoramidite Ligands Containing Chiral Ferrocenyl Amine

    Energy Technology Data Exchange (ETDEWEB)

    Park, Hyun-Sub; Kim, Min Young; Ahn, Hyo Jin; Han, Jin Wook [Hanyang University, Seoul (Korea, Republic of)

    2016-06-15

    Asymmetric hydrosilylation was one of the most effective methods, which provided optically active organosilanes as a synthetically useful intermediate in organic synthesis. One useful transformation is the Tamao-Fleming oxidation, which is an oxidation reaction of carbon[BOND]silicone bond to afford optically active alcohols with retention of configuration. It is demonstrated that a palladium catalyst coordinating with phosphoramidite ligand (S {sub a},R {sub c},R {sub c,})-L3a from (S)-BINOL and chiral bis((R)-1-ferrocenylethyl) amine shows a high catalytic activity and enantioselectivity up to 97% ee in asymmetric hydrosilylation of styrene and its derivatives. The hydrosilylation of various olefin substrates using these ligands is in progress.

  7. Chiral Synthons in Pesticide Syntheses

    NARCIS (Netherlands)

    Feringa, Bernard

    1988-01-01

    The use of chiral synthons in the preparation of enantiomerically pure pesticides is described in this chapter. Several routes to chiral synthons based on asymmetric synthesis or on natural products are illustrated. Important sources of chiral building blocks are reviewed. Furthermore the

  8. Holographic Chiral Magnetic Spiral

    International Nuclear Information System (INIS)

    Kim, Keun-Young; Sahoo, Bindusar; Yee, Ho-Ung

    2010-06-01

    We study the ground state of baryonic/axial matter at zero temperature chiral-symmetry broken phase under a large magnetic field, in the framework of holographic QCD by Sakai-Sugimoto. Our study is motivated by a recent proposal of chiral magnetic spiral phase that has been argued to be favored against previously studied phase of homogeneous distribution of axial/baryonic currents in terms of meson super-currents dictated by triangle anomalies in QCD. Our results provide an existence proof of chiral magnetic spiral in strong coupling regime via holography, at least for large axial chemical potentials, whereas we don't find the phenomenon in the case of purely baryonic chemical potential. (author)

  9. Tandem radical reactions and ring-closing metathesis. Application in the synthesis of cyclooctenes.

    Science.gov (United States)

    Sibi, Mukund P; Aasmul, Mona; Hasegawa, Hikaru; Subramanian, Thangaiah

    2003-08-07

    [reaction: see text] Fumarate- and acrylate-substituted oxazolidinones undergo tandem radical reaction to form dienes in moderate to good yields. The resulting dienes provide cyclooctenes in moderate to good yields after ring-closing metathesis (RCM). The role of the carbon backbone substituents and other variables in the efficiency of the eight-membered ring formation is discussed.

  10. Metathesis of cardanol over Ru catalysts supported on mesoporousmolecular sieve SBA-15

    Czech Academy of Sciences Publication Activity Database

    Shinde, Tushar; Varga, Vojtěch; Polášek, Miroslav; Horáček, Michal; Žilková, Naděžda; Balcar, Hynek

    2014-01-01

    Roč. 478, MAY 2014 (2014), s. 138-145 ISSN 0926-860X R&D Projects: GA ČR(CZ) GAP106/12/0189 Institutional support: RVO:61388955 Keywords : cardanol * metathesis * supported catalysts Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.942, year: 2014

  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. Efforts toward rapid construction of the cortistatin A carbocyclic core via enyne-ene metathesis

    KAUST Repository

    Baumgartner, Corinne

    2010-01-01

    Our efforts toward the construction of the carbocylic core of cortistatin A via an enyne-ene metathesis are disclosed. Interestingly, an attempted S N2 inversion of a secondary mesylate in our five-membered D-ring piece gave a product with retention of stereochemistry. © 2010 The Royal Society of Chemistry.

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

    KAUST Repository

    Morandi, Bill; Wickens, Zachary K.; Grubbs, Robert H.

    2013-01-01

    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.

  14. 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

  15. Synthesis of the carbocyclic core of the cornexistins by ring-closing metathesis.

    Science.gov (United States)

    Clark, J Stephen; Marlin, Frederic; Nay, Bastien; Wilson, Claire

    2003-01-09

    An advanced intermediate in the synthesis of the phytotoxins cornexistin and hydroxycornexistin has been synthesized. Sequential palladium-mediated sp(2)-sp(3) fragment coupling and ring-closing diene metathesis have been used to construct the nine-membered carbocyclic core found in the natural products. [reaction--see text

  16. Efforts toward rapid construction of the cortistatin A carbocyclic core via enyne-ene metathesis

    KAUST Repository

    Baumgartner, Corinne; Ma, Sandy; Liu, Qi; Stoltz, Brian M.

    2010-01-01

    Our efforts toward the construction of the carbocylic core of cortistatin A via an enyne-ene metathesis are disclosed. Interestingly, an attempted S N2 inversion of a secondary mesylate in our five-membered D-ring piece gave a product with retention

  17. Selective conversion of butane into liquid hydrocarbon fuels on alkane metathesis catalysts

    KAUST Repository

    Szeto, Kaï Chung

    2012-01-01

    We report a selective direct conversion of n-butane into higher molecular weight alkanes (C 5+) by alkane metathesis reaction catalysed by silica-alumina supported tungsten or tantalum hydrides at moderate temperature and pressure. The product is unprecedented, asymmetrically distributed towards heavier alkanes. This journal is © 2012 The Royal Society of Chemistry.

  18. Reactivity of olefin and allyl ligands in π-complexes of metals

    International Nuclear Information System (INIS)

    Kukushkin, Yu.N.

    1987-01-01

    The data on reactivity of olefin and allyl ligands in transition metal (Ru, W) π-complexes, published up to 1984 are presented. Metal ion coordination of olefins causes their appreciable reactivity change. Transformations of π-olefin ligands into σ-alkyl ones, interaction of π-complexes with oxygen nucleophilic reagents, amines, halogenides and pseudohalogenides are considered

  19. Palladium(II)-catalyzed ortho-olefination of arenes applying sulfoxides as remote directing groups.

    Science.gov (United States)

    Wang, Binjie; Shen, Chuang; Yao, Jinzhong; Yin, Hong; Zhang, Yuhong

    2014-01-03

    A novel palladium-catalyzed ortho-C(sp(2))-H olefination protocol has been developed by the use of sulfoxide as the directing group. Importantly, relatively remote coordination can be accessed to achieve the ortho olefination of benzyl, 2-arylethyl, and 3-arylpropenyl sulfoxide substrates, and the olefinated sulfoxide can be easily transformed to other functionalities.

  20. Kinetically based NMR method of measuring blending octane number of olefins

    NARCIS (Netherlands)

    Golombok, M.; Bruijn, J.; Morley, C.

    1995-01-01

    Olefins are highly nonlinear octane blenders so that standard GC analyses are poor predictors of blend quality. Engine rating is the only way of measuring olefin octane number nonlinearity. It is thus not possible to rapidly assess the quality of the product obtained from an olefin-producing

  1. Chiral perturbation theory

    International Nuclear Information System (INIS)

    Ecker, G.

    1996-06-01

    After a general introduction to the structure of effective field theories, the main ingredients of chiral perturbation theory are reviewed. Applications include the light quark mass ratios and pion-pion scattering to two-loop accuracy. In the pion-nucleon system, the linear σ model is contrasted with chiral perturbation theory. The heavy-nucleon expansion is used to construct the effective pion-nucleon Lagrangian to third order in the low-energy expansion, with applications to nucleon Compton scattering. (author)

  2. Asymmetric chiral colour

    International Nuclear Information System (INIS)

    Cuypers, F.

    1990-01-01

    Chiral colour is considered in a general framework where the coupling constants associated with each SU(3) component are allowed to be different. To reproduce QCD at low energy, gluons and axigluons cannot then be maximally mixed. Present data form e + e - colliders contrains the axigluon mass to values between 50 GeV and 375 GeV whilst the mixing angle is bounded by 13deg and 45deg. The lower limit of the axigluon mass is a definite bound at 90% C.L., whereas the upper limit only applies if chiral colour is to explain the anomalously high rates of hadron production at TRISTAN. (orig.)

  3. Chirality: from QCD to condensed matter

    International Nuclear Information System (INIS)

    Kharzeev, D.

    2015-01-01

    This lecture is about chirality and consists of 4 parts. In the first part a general introduction of chirality is given and its implementation in nuclear and particle physics, in particular the chiral magnetic effect, as well as Chirality in quantum materials (CME, optoelectronics, photonics) are discussed. The 2nd lecture is about the chiral magnetic effect. The 3rd lecture deals with the chiral magnetic effect and hydrodynamics and the last part with chirality and light. (nowak)

  4. Ionic liquids for separation of olefin-paraffin mixtures

    Science.gov (United States)

    Dai, Sheng; Luo, Huimin; Huang, Jing-Fang

    2013-09-17

    The invention is directed to an ionic liquid comprising (i) a cationic portion containing a complex of a silver (I) ion and one or more neutral ligands selected from organoamides, organoamines, olefins, and organonitriles, and (ii) an anionic portion having the chemical formula ##STR00001## wherein m and n are independently 0 or an integer of 1 or above, and p is 0 or 1, provided that when p is 0, the group --N--SO.sub.2--(CF.sub.2).sub.nCF.sub.3 subtended by p is replaced with an oxide atom connected to the shown sulfur atom. The invention is also directed to a method for separating an olefin from an olefin-paraffin mixture by passing the mixture through a layer of the ionic liquid described above.

  5. Allene or alkyne treatment of olefin conversion catalysts

    International Nuclear Information System (INIS)

    Banks, R.L.

    1986-01-01

    This patent describes a disproportionation process which comprises contacting at least one olefin from the group consisting of: acyclic mono- and polyenes having at least 3 up to 10 carbon atoms per molecule, and cycloalkyl and aryl derivatives thereof; cyclic mono- and polyenes having at least 4 to 10 carbon atoms per molecule, and alkyl and aryl derivatives thereof; mixtures of two or more of the above olefins; and mixtures of ethylene with one or more of the above olefins capable of undergoing disproportionation with a tungsten oxide on silica disproportionation catalyst system under disproportionation conditions, the improvement comprising contacting the catalyst with an activating amount of at least one alkyne conforming to the formula: R-C=C-R wherein each R is independently H or a C/sub 1/-C/sub 6/ carbon radical per mole of tungsten oxide

  6. Synthetic and mechanistic aspects of titanium-mediated carbonyl olefinations

    Energy Technology Data Exchange (ETDEWEB)

    Petasis, N.A.; Staszewski, J.P.; Hu, Yong-Han; Lu, Shao-Po [Univ. of Southern California, Los Angeles, CA (United States)

    1995-12-31

    A new method for the olefination of carbonyl compounds with dimethyl titanocene, and other related bishydrocarbyl titanocene derivatives has been recently developed in the author`s laboratories. This process is experimentally convenient and works with various types of carbonyl compounds, including aldehydes, ketones, esters, lactones, carbonates, anhydrides, amides, imides, lactams, thioesters, selenoesters, and acylsilanes. More recent studies have focused on the scope and utility of this reaction, including mechanistic studies and synthetic applications. In addition to varying the reaction conditions, the authors have examined several mixed titanocene derivatives and have found ways for carrying out this type of olefination at room temperature, such as the use of tris(trimethylsilyl) titanacyclobutene. The authors have also employed this reaction in the modification of carbohydrates and cyclobutenediones. This olefination was also followed-up with subsequent transformations to produce carbocycles and heterocycles, including tetrahydrofurans and tetrahydropyrans.

  7. Olefination reactions of phosphorus-stabilized carbon nucleophiles.

    Science.gov (United States)

    Gu, Yonghong; Tian, Shi-Kai

    2012-01-01

    A range of phosphorus-stabilized carbon nucleophiles have been employed for alkene synthesis with high chemo-, regio-, and stereoselectivity. The Wittig, Horner-Wadsworth-Emmons, Horner-Wittig, and Evans-Akiba reactions utilize phosphonium-, phosphonate-, phosphine oxide-, and pentacoordinated phosphorane-stabilized carbanions as nucleophiles, respectively, to undergo olefination with aldehydes or ketones, and each of these transformations has its own advantages and limitations. Modifying the structures of these nucleophiles along with optimizing reaction conditions results in the formation of a wide variety of polysubstituted alkenes in a highly stereoselective manner. The olefination of imines with phosphonium ylides has recently emerged as a useful approach to tune the stereoselectivity for alkene synthesis. This review focuses on recent advances in the stereoselective olefination of phosphorus-stabilized carbon nucleophiles.

  8. Chiral algebras for trinion theories

    International Nuclear Information System (INIS)

    Lemos, Madalena; Peelaers, Wolfger

    2015-01-01

    It was recently understood that one can identify a chiral algebra in any four-dimensional N=2 superconformal theory. In this note, we conjecture the full set of generators of the chiral algebras associated with the T n theories. The conjecture is motivated by making manifest the critical affine module structure in the graded partition function of the chiral algebras, which is computed by the Schur limit of the superconformal index for T n theories. We also explicitly construct the chiral algebra arising from the T 4 theory. Its null relations give rise to new T 4 Higgs branch chiral ring relations.

  9. Chiral forces and molecular dissymmetry

    International Nuclear Information System (INIS)

    Mohan, R.

    1992-01-01

    Chiral molecules leading to helical macromolecules seem to preserve information and extend it better. In the biological world RNA is the very paradigm for self-replication, elongation and autocatalytic editing. The nucleic acid itself is not chiral. It acquires its chirality by association with D-sugars. Although the chiral information or selectivity put in by the unit monomer is no longer of much interest to the biologists - they tend to leave it to the Darwinian selection principle to take care of it as illustrated by Frank's model - it is vital to understand the origin of chirality. There are three different approaches for the chiral origin of life: (1) Phenomenological, (2) Electromagnetic molecular and Coriolis forces and (3) Atomic or nuclear force, the neutral weak current. The phenomenological approach involves spontaneous symmetry breaking fluctuations in far for equilibrium systems or nucleation and crystallization. Chance plays a major role in the chiral molecule selected

  10. Chirality in molecular collision dynamics

    Science.gov (United States)

    Lombardi, Andrea; Palazzetti, Federico

    2018-02-01

    Chirality is a phenomenon that permeates the natural world, with implications for atomic and molecular physics, for fundamental forces and for the mechanisms at the origin of the early evolution of life and biomolecular homochirality. The manifestations of chirality in chemistry and biochemistry are numerous, the striking ones being chiral recognition and asymmetric synthesis with important applications in molecular sciences and in industrial and pharmaceutical chemistry. Chiral discrimination phenomena, due to the existence of two enantiomeric forms, very well known in the case of interaction with light, but still nearly disregarded in molecular collision studies. Here we review some ideas and recent advances about the role of chirality in molecular collisions, designing and illustrating molecular beam experiments for the demonstration of chiral effects and suggesting a scenario for a stereo-directional origin of chiral selection.

  11. Methylenation of perfluoroalkyl ketones using a Peterson olefination approach.

    Science.gov (United States)

    Hamlin, Trevor A; Kelly, Christopher B; Cywar, Robin M; Leadbeater, Nicholas E

    2014-02-07

    An operationally simple, inexpensive, and rapid route for the olefination of a wide array of trifluoromethyl ketones to yield 3,3,3-trifluoromethylpropenes is reported. Using a Peterson olefination approach, the reaction gives good to excellent yields of the alkene products and can be performed without purification of the β-hydroxysilyl intermediate. The reaction can be extended to other perfluoroalkyl substituents and is easily scaled up. The alkenes prepared can be readily transformed into a variety of other perfluoroalkyl-containing compounds.

  12. Silver-Catalyzed Aldehyde Olefination Using Siloxy Alkynes.

    Science.gov (United States)

    Sun, Jianwei; Keller, Valerie A; Meyer, S Todd; Kozmin, Sergey A

    2010-03-20

    We describe the development of a silver-catalyzed carbonyl olefination employing electron rich siloxy alkynes. This process constitutes an efficient synthesis of trisubstituted unsaturated esters, and represents an alternative to the widely utilized Horner-Wadsworth-Emmons reaction. Excellent diastereoselectivities are observed for a range of aldehydes using either 1-siloxy-1-propyne or 1-siloxy-1-hexyne. This mild catalytic process also enables chemoselective olefination of aldehydes in the presence of either ester or ketone functionality. Furthermore, since no by-products are generated, this catalytic process is perfectly suited for development of sequential reactions that can be carried out in a single flask.

  13. Insight into the chiral induction in supramolecular stacks through preferential chiral salvation

    NARCIS (Netherlands)

    George, S.J.; Tomovic, Z.; Schenning, A.P.H.J.; Meijer, E.W.

    2011-01-01

    Preferred handedness in the supramolecular chirality of self-assembled achiral oligo(p-phenylenevinylene) (OPV) derivatives is induced by chiral solvents and spectroscopic probing provides insight into the mechanistic aspects of this chiral induction through chiral solvation

  14. Electrochemistry for biofuel generation: transformation of fatty acids and triglycerides to diesel-like olefin/ether mixtures and olefins.

    Science.gov (United States)

    dos Santos, Tatiane R; Harnisch, Falk; Nilges, Peter; Schröder, Uwe

    2015-03-01

    Electroorganic synthesis can be exploited for the production of biofuels from fatty acids and triglycerides. With Coulomb efficiencies (CE) of up to 50 %, the electrochemical decarboxylation of fatty acids in methanolic and ethanolic solutions leads to the formation of diesel-like olefin/ether mixtures. Triglycerides can be directly converted in aqueous solutions by using sonoelectrochemistry, with olefins as the main products (with a CE of more than 20 %). The latter reaction, however, is terminated at around 50 % substrate conversion by the produced side-product glycerol. An energy analysis shows that the electrochemical olefin synthesis can be an energetically competitive, sustainable, and--in comparison with established processes--economically feasible alternative for the exploitation of fats and oils for biofuel production. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Poisoning Experiments Aimed at Discriminating Active and Less-Active Sites of Silica-Supported Tantalum Hydride for Alkane Metathesis

    KAUST Repository

    Saggio, Guillaume; Taoufik, Mostafa; Basset, Jean-Marie; Thivolle-Cazat, Jean

    2010-01-01

    Only 50% of the silica-supported tantalum hydride sites are active in the metathesis of propane. Indeed, more than 45% of the tantalum hydride can be eliminated by a selective oxygen poisoning of inactive sites with no significant decrease

  16. A stereoselective synthesis of (+)-physoperuvine using a tandem aza-Claisen rearrangement and ring closing metathesis reaction.

    Science.gov (United States)

    Zaed, Ahmed M; Swift, Michael D; Sutherland, Andrew

    2009-07-07

    A stereoselective synthesis of (+)-physoperuvine, a tropane alkaloid from Physalis peruviana Linne has been developed using a one-pot tandem aza-Claisen rearrangement and ring closing metathesis reaction to form the key amino-substituted cycloheptene ring.

  17. Detecting the chirality for coupled quantum dots

    International Nuclear Information System (INIS)

    Cao Huijuan; Hu Lian

    2008-01-01

    We propose a scheme to detect the chirality for a system consisting of three coupled quantum dots. The chirality is found to be determined by the frequency of the transition between chiral states under the chiral symmetry broken perturbation. The results are important to construct quantum gates and to demonstrate chiral entangle states in the triangle spin dots

  18. Catalytic asymmetric dihydroxylation of olefins with reusable OsO(4)(2-) on ion-exchangers: the scope and reactivity using various cooxidants.

    Science.gov (United States)

    Choudary, Boyapati M; Chowdari, Naidu S; Jyothi, Karangula; Kantam, Mannepalli L

    2002-05-15

    Exchanger-OsO(4) catalysts are prepared by an ion-exchange technique using layered double hydroxides and quaternary ammonium salts covalently bound to resin and silica as ion-exchangers. The ion-exchangers with different characteristics and opposite ion selectivities are specially chosen to produce the best heterogeneous catalyst that can operate using the various cooxidants in the asymmetric dihydroxylation reaction. LDH-OsO(4) catalysts composed of different compositions are evaluated for the asymmetric dihydroxylation of trans-stilbene. Resin-OsO(4) and SiO(2)-OsO(4) designed to overcome the problems associated with LDH-OsO(4) indeed show consistent activity and enantioselectivity in asymmetric dihydroxylation of olefins using K(3)Fe(CN)(6) and molecular oxygen as cooxidants. Compared to the Kobayashi heterogeneous systems, resin-OsO(4) is a very efficient catalyst for the dihydroxylation of a wide variety of aromatic, aliphatic, acyclic, cyclic, mono-, di-, and trisubstituted olefins to afford chiral vicinal diols with high yields and enantioselectivities irrespective of the cooxidant used. Resin-OsO(4) is recovered quantitatively by a simple filtration and reused for a number of cycles with consistent activity. The high binding ability of the heterogeneous osmium catalyst enables the use of an equimolar ratio of ligand to osmium to give excellent enantioselectives in asymmetric dihydroxylation in contrast to the homogeneous osmium system in which excess molar quantities of the expensive chiral ligand to osmium are invariably used. The complexation of the chiral ligand (DHQD)(2)PHAL, having very large dimension, a prerequisite to obtain higher ee, is possible only with the OsO(4)(2-) located on the surface of the supports.

  19. 1,2-Ferrocenediylazaphosphinines 3: a new class of planar chiral ligands for Cu-catalyzed cyclopropanation

    Energy Technology Data Exchange (ETDEWEB)

    Paek, Seung Hwan; Co, Thanh Thien; Lee, Dong Ho; Park, Yu Chul; Kim, Tae Jeong [Kyungpook National Univ., Daegu (Korea, Republic of)

    2002-12-01

    The synthesis and catalytic application of a new class of planar chiral ferrocenes, 1,2-ferrocenediylazaphos-phinines (1 and 2) are described. They are powerful ligands for the copper(I)-catalyzed asymmetric cyclopropanation of a range of alkenes with diazo esters to exhibit an exceptionally high degree of diastereoselectivity ({approx}100%) in favor of trans isomers, regardless the structure of the olefins and the diazo compounds. Comparative studies between 1 and 2 reveal that the former works better in terms of diastereocontrol. In contrast, however, enantioselectivity is low with both 1 and 2 as a whole although, in certain cases with a proper combination of the olefin and the diazo ester, high optical yields (up to 100% ee) can be achieved. Other reaction parameters such as the reaction temperature and the structure of the ligand do exhibit some influence, although infinitesimal, on both chemical and optical yields.

  20. 1,2-Ferrocenediylazaphosphinines 3: a new class of planar chiral ligands for Cu-catalyzed cyclopropanation

    International Nuclear Information System (INIS)

    Paek, Seung Hwan; Co, Thanh Thien; Lee, Dong Ho; Park, Yu Chul; Kim, Tae Jeong

    2002-01-01

    The synthesis and catalytic application of a new class of planar chiral ferrocenes, 1,2-ferrocenediylazaphos-phinines (1 and 2) are described. They are powerful ligands for the copper(I)-catalyzed asymmetric cyclopropanation of a range of alkenes with diazo esters to exhibit an exceptionally high degree of diastereoselectivity (∼100%) in favor of trans isomers, regardless the structure of the olefins and the diazo compounds. Comparative studies between 1 and 2 reveal that the former works better in terms of diastereocontrol. In contrast, however, enantioselectivity is low with both 1 and 2 as a whole although, in certain cases with a proper combination of the olefin and the diazo ester, high optical yields (up to 100% ee) can be achieved. Other reaction parameters such as the reaction temperature and the structure of the ligand do exhibit some influence, although infinitesimal, on both chemical and optical yields

  1. Capturing of the monoterpene olefin limonene produced in Saccharomyces cerevisiae

    NARCIS (Netherlands)

    Jongedijk, E.J.; Cankar, K.; Ranzijn, J.; Krol, van der A.R.; Bouwmeester, H.J.; Beekwilder, M.J.

    2015-01-01

    Monoterpene olefins such as limonene are plant compounds with applications as flavouring and fragrance agents, as solvents and potentially also in polymer and fuel chemistry. We engineered baker's yeast Saccharomyces cerevisiae to express a (-)-limonene synthase from Perilla frutescens and a

  2. Methanol conversion to lower olefins over RHO type zeolite

    KAUST Repository

    Masih, Dilshad; Imai, Hiroyuki; Yokoi, Toshiyuki; Kondo, Junkonomura; Tatsumi, Takashi

    2013-01-01

    Eight-membered ring small-pore zeolite of RHO-type topology has been synthesized, characterized and tested for methanol-to-olefin (MTO) reaction. The zeolite was hydrothermally crystallized from the gel with Si/Al ratio of 5.0. It showed a high BET

  3. Ozonolysis of Model Olefins-Efficiency of Antiozonants

    NARCIS (Netherlands)

    Huntink, N.M.; Datta, Rabin; Talma, Auke; Noordermeer, Jacobus W.M.

    2006-01-01

    In this study, the efficiency of several potential long lasting antiozonants was studied by ozonolysis of model olefins. 2-Methyl-2-pentene was selected as a model for natural rubber (NR) and 5-phenyl-2-hexene as a model for styrene butadiene rubber (SBR). A comparison was made between the

  4. Catalytic polymerization of olefins in supercritical carbon dioxide

    NARCIS (Netherlands)

    Kemmere, M.F.; Vries, de T.J.; Keurentjes, J.T.F.

    2004-01-01

    A novel process is being developed for the catalytic polymerization of olefins in supercritical carbon dioxide (sc CO2), for which potential applications will mainly be in the production of EPDM and other elastomers. For this purpose, the Brookhart catalyst has been tested for the homopolymerization

  5. Radiation-induced copolymerization of hexafluoroacetone with α-olefins

    International Nuclear Information System (INIS)

    Matsuda, O.; Watanabe, S.; Okamoto, J.; Machi, S.; Tabata, Y.

    1977-01-01

    The copolymerization of hexafluoroacetone with higher α-olefins above butene, such as 1-pentene (I), 1-hexene (II), 1-octene (III), 2-methyl-1-butene (IV), 2-methyl-1-pentene (V), 3-methyl-1-butene (VI), and 4-methyl-1-pentene (VII) was studied at relatively low temperatures by γ-ray irradiation. Copolymerization of II, IV, V, and VII with hexafluoroacetone was found to scarcely take place at -78 0 C in bulk, but the addition of trichlorotrifluoroethane in amounts to yield equimolar mixtures resulted in conversion of 15.7 percent for IV and of 2.1 to 4.0 percent for the other α-olefins. Higher conversion of V at -78 0 C than at 0 0 C suggest that copolymerization may take place via an ionic mechanism. The effects of various additives on the copolymerization are reported. Infrared spectral studies indicated that the double bond of the α-olefins is opened to form a polymer. The C--O double bond of the hexafluoroacetone and the α-olefin double bond are opened to form the copolymer

  6. Optical fibre Bragg grating recorded in TOPAS cyclic olefin copolymer

    DEFF Research Database (Denmark)

    Johnson, I.P.; Yuan, Scott Wu; Stefani, Alessio

    2011-01-01

    A report is presented on the inscription of a fibre Bragg grating into a microstructured polymer optical fibre fabricated from TOPAS cyclic olefin copolymer. This material offers two important advantages over poly (methyl methacrylate), which up to now has formed the basis for polymer fibre Bragg...

  7. Olefination of carbonyl compounds: modern and classical methods

    Energy Technology Data Exchange (ETDEWEB)

    Korotchenko, V N; Nenajdenko, Valentine G; Balenkova, Elizabeth S [Department of Chemistry, M.V. Lomonosov Moscow State University, Moscow (Russian Federation); Shastin, Aleksey V [Institute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka, Moscow Region (Russian Federation)

    2004-10-31

    The published data on the methods for alkene synthesis by olefination of carbonyl compounds are generalised and systematised. The main attention is given to the use of transition metals and organoelement compounds. The review covers the data on both classical and newly developed methods that are little known to chemists at large.

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

    Science.gov (United States)

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

    2017-08-30

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

  9. Olefination of carbonyl compounds: modern and classical methods

    Science.gov (United States)

    Korotchenko, V. N.; Nenajdenko, Valentine G.; Balenkova, Elizabeth S.; Shastin, Aleksey V.

    2004-10-01

    The published data on the methods for alkene synthesis by olefination of carbonyl compounds are generalised and systematised. The main attention is given to the use of transition metals and organoelement compounds. The review covers the data on both classical and newly developed methods that are little known to chemists at large.

  10. Access to Functionalized Steroid Side Chains via Modified Julia Olefination

    Science.gov (United States)

    Izgu, Enver Cagri; Burns, Aaron C.; Hoye, Thomas R.

    2011-01-01

    Various functionalized steroidal side chains were conveniently accessed by a modified Julia olefination strategy using a common sulfone donor and an appropriate α-branched aldehyde acceptor. For the coupling of these hindered classes of reaction partners (and in contrast to typically observed trends), the benzothiazolyl(BT)-sulfone anion gave superior outcomes compared to the phenyltetrazolyl(PT)-sulfone anion. PMID:21244047

  11. Non-uniform chiral phase in effective chiral quark models

    International Nuclear Information System (INIS)

    Sadzikowski, M.; Broniowski, W.

    2000-01-01

    We analyze the phase diagram in effective chiral quark models (the Nambu-Jona-Lasinio model, the σ-model with quarks) and show that at the mean-field level a phase with a periodically-modulated chiral fields separates the usual phases with broken and restored chiral symmetry. A possible signal of such a phase is the production of multipion jets travelling in opposite directions, with individual pions having momenta of the order of several hundred MeV. This signal can be interpreted in terms of disoriented chiral condensates. (author)

  12. Variation of the Sterical Properties of the N-Heterocyclic Carbene Coligand in Thermally Triggerable Ruthenium-Based Olefin Metathesis Precatalysts/Initiators

    KAUST Repository

    Pump, Eva; Leitgeb, Anita; Kozłowska, Anna; Torvisco, Ana; Falivene, Laura; Cavallo, Luigi; Grela, Karol; Slugovc, Christian

    2015-01-01

    A series of ruthenium complexes based on the κ(C,N)-(2-(benzo[h]quinolin-10-yl)methylidene ruthenium dichloride fragment featuring different neutral coligands L (L = 1,3-bis(2,6-diisopropylphenyl)-4,5-dihydroimidazol-2-ylidene (SIPr), 1,3-bis(2

  13. Highly recoverable pyridinium-tagged Hoveyda-Grubbs pre-catalyst for olefin metathesis. Design of the boomerang ligand toward the optimal compromise between activity and reusability.

    Science.gov (United States)

    Rix, Diane; Caïjo, Fréderic; Laurent, Isabelle; Gulajski, Lukasz; Grela, Karol; Mauduit, Marc

    2007-09-28

    Whereas the boomerang ligand of Hoveyda-Grubbs pre-catalysts can be modified by attachment of a pyridinium tag to its benzylidene moiety, a precise adjustment of the length of the spacer allows the optimum balance to be reached between the activity of the catalyst and its recoverability, exceeding 98% after 6 catalytic runs in the best case.

  14. Hydro-Metathesis of Long-Chain Olefin (1-decene) using Well-Defined Silica-Supported Tungsten (VI), Molybdenum (VI) and Tantalum (V) Catalysts

    KAUST Repository

    Saidi, Aya

    2016-01-01

    Nowadays, catalysis lies at the heart of economy growth mainly in the petroleum industry. Catalysis can offer real and potential solutions to the current challenges for a long-term sustainable energy, green chemistry, and environmental protection

  15. In Silico Switch from Second- to First-Row Transition Metals in Olefin Metathesis: From Ru to Fe and from Rh to Co

    Directory of Open Access Journals (Sweden)

    Jesús Antonio Luque-Urrutia

    2017-12-01

    Full Text Available Density functional theory (DFT calculations have been used to investigate the behavior of different transition metals from Groups 8 (Fe and Ru and 9 (Co and Rh in an already well-known catalytic mechanism, which is based on an Ru(SIMes(PPh3Cl2=CH(Ph complex. As expected, Ru has proven to perform better than their Fe, Co, and Rh counterparts. Even though the topographic steric maps analysis shows no difference in sterical hindrance for any of the metal centers, geometrically, the Fe-based species show a high rigidity with shorter and stronger bonds confirmed by Mayer Bond Orders. The systems bearing Co as a metallic center might present a reactivity that is, surprisingly, too high according to conceptual DFT, which would consequently be a drawback for the formation of the fundamental species of the reaction pathway: the metallacycle intermediate.

  16. Chiral magnetic effect of light

    Science.gov (United States)

    Hayata, Tomoya

    2018-05-01

    We study a photonic analog of the chiral magnetic (vortical) effect. We discuss that the vector component of magnetoelectric tensors plays a role of "vector potential," and its rotation is understood as "magnetic field" of a light. Using the geometrical optics approximation, we show that "magnetic fields" cause an anomalous shift of a wave packet of a light through an interplay with the Berry curvature of photons. The mechanism is the same as that of the chiral magnetic (vortical) effect of a chiral fermion, so that we term the anomalous shift "chiral magnetic effect of a light." We further study the chiral magnetic effect of a light beyond geometric optics by directly solving the transmission problem of a wave packet at a surface of a magnetoelectric material. We show that the experimental signal of the chiral magnetic effect of a light is the nonvanishing of transverse displacements for the beam normally incident to a magnetoelectric material.

  17. Chiral Responsive Liquid Quantum Dots.

    Science.gov (United States)

    Zhang, Jin; Ma, Junkai; Shi, Fangdan; Tian, Demei; Li, Haibing

    2017-08-01

    How to convert the weak chiral-interaction into the macroscopic properties of materials remains a huge challenge. Here, this study develops highly fluorescent, selectively chiral-responsive liquid quantum dots (liquid QDs) based on the hydrophobic interaction between the chiral chains and the oleic acid-stabilized QDs, which have been designated as (S)-1810-QDs. The fluorescence spectrum and liquidity of thermal control demonstrate the fluorescence properties and the fluidic behavior of (S)-1810-QDs in the solvent-free state. Especially, (S)-1810-QDs exhibit a highly chiral-selective response toward (1R, 2S)-2-amino-1,2-diphenyl ethanol. It is anticipated that this study will facilitate the construction of smart chiral fluidic sensors. More importantly, (S)-1810-QDs can become an attractive material for chiral separation. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Chiral colour and axigluons

    International Nuclear Information System (INIS)

    Cuypers, F.

    1989-01-01

    The authors studies the phenomenological implications of the Chiral Colour model which allow him to derive experimental bounds on the axigluon mass or to predict deviations from the Standard Model. After a short introduction to the theory, the author examines the way it modifies the standard decay of quarkonium. Comparison with the observed lifetime of the upsilon allows him to exclude the existence of axigluons lighter than 9 GeV. (Others have since extended the work and were able to increase this limit to 25 GeV.) He then studies the Chiral Colour contribution to the hadronic cross-section in the electron-positron scattering and derive a conservative lower bound of 50 GeV for the axigluon mass. Finally, he predicts observable enhancements of the lifetime and rare decay channels of the Z O in the presence of light axigluons

  19. Chiral Biomarkers in Meteorites

    Science.gov (United States)

    Hoover, Richard B.

    2010-01-01

    The chirality of organic molecules with the asymmetric location of group radicals was discovered in 1848 by Louis Pasteur during his investigations of the rotation of the plane of polarization of light by crystals of sodium ammonium paratartrate. It is well established that the amino acids in proteins are exclusively Levorotary (L-aminos) and the sugars in DNA and RNA are Dextrorotary (D-sugars). This phenomenon of homochirality of biological polymers is a fundamental property of all life known on Earth. Furthermore, abiotic production mechanisms typically yield recemic mixtures (i.e. equal amounts of the two enantiomers). When amino acids were first detected in carbonaceous meteorites, it was concluded that they were racemates. This conclusion was taken as evidence that they were extraterrestrial and produced by abiologically. Subsequent studies by numerous researchers have revealed that many of the amino acids in carbonaceous meteorites exhibit a significant L-excess. The observed chirality is much greater than that produced by any currently known abiotic processes (e.g. Linearly polarized light from neutron stars; Circularly polarized ultraviolet light from faint stars; optically active quartz powders; inclusion polymerization in clay minerals; Vester-Ulbricht hypothesis of parity violations, etc.). This paper compares the measured chirality detected in the amino acids of carbonaceous meteorites with the effect of these diverse abiotic processes. IT is concluded that the levels observed are inconsistent with post-arrival biological contamination or with any of the currently known abiotic production mechanisms. However, they are consistent with ancient biological processes on the meteorite parent body. This paper will consider these chiral biomarkers in view of the detection of possible microfossils found in the Orgueil and Murchison carbonaceous meteorites. Energy dispersive x-ray spectroscopy (EDS) data obtained on these morphological biomarkers will be

  20. On chiral bosonization

    International Nuclear Information System (INIS)

    Bastianelli, F.

    1991-01-01

    We examine the bosonization of chiral fermions in a gravitational background, using a path integral approach. The bosonic model is given by an action proposed some time ago by Floreanini and Jackiw, suitably coupled to gravity. We use a regulator for the path integral measure obtained from the general construction of Diaz, Hatsuda, Troost, van Nieuwenhuizen and Van Proeyen. We show that the effective actions are identical. (orig.)

  1. Dynamical chiral bag model

    International Nuclear Information System (INIS)

    Colanero, K.; Chu, M.-C.

    2002-01-01

    We study a dynamical chiral bag model, in which massless fermions are confined within an impenetrable but movable bag coupled to meson fields. The self-consistent motion of the bag is obtained by solving the equations of motion exactly assuming spherical symmetry. When the bag interacts with an external meson wave we find three different kinds of resonances: fermionic, geometric, and σ resonances. We discuss the phenomenological implications of our results

  2. Chiral Dynamics 2006

    Science.gov (United States)

    Ahmed, Mohammad W.; Gao, Haiyan; Weller, Henry R.; Holstein, Barry

    2007-10-01

    pt. A. Plenary session. Opening remarks: experimental tests of chiral symmetry breaking / A. M. Bernstein. [Double pie symbols] scattering / H. Leutwyler. Chiral effective field theory in a [Triangle]-resonance region / V. Pascalutsa. Some recent developments in chiral perturbation theory / Ulf-G. Mei ner. Chiral extrapolation and nucleon structure from the lattice / R.D. Young. Recent results from HAPPEX / R. Michaels. Chiral symmetries and low energy searches for new physics / M.J. Ramsey-Musolf. Kaon physics: recent experimental progress / M. Moulson. Status of the Cabibbo angle / V. Cirigliano. Lattice QCD and nucleon spin structure / J.W. Negele. Spin sum rules and polarizabilities: results from Jefferson lab / J-P Chen. Compton scattering and nucleon polarisabilities / Judith A. McGovern. Virtual compton scattering at MIT-bates / R. Miskimen. Physics results from the BLAST detector at the BATES accelerator / R.P. Redwine. The [Pie sympbol]NN system, recent progress / C. Hanhart. Application of chiral nuclear forces to light nuclei / A. Nogga. New results on few-body experiments at low energy / Y. Nagai. Few-body lattice calculations / M.J. Savage. Research opportunities at the upgraded HI?S facility / H.R. Weller -- pt. B. Goldstone boson dynamics. Working group summary: Goldstone Boson dynamics / G. Colangelo and S. Giovannella. Recent results on radiative Kaon decays from NA48 and NA48/2 / S.G. López. Cusps in K-->3 [Pie symbol] decays / B. Kubis. Recent KTeV results on radiative Kaon decays / M.C. Ronquest. The [Double pie symbols] scattering amplitude / J.R. Peláez. Determination of the Regge parameters in the [Double pie symbols] scattering amplitude / I. Caprini. e+e- Hadronic cross section measurement at DA[symbol]NE with the KLOE detector / P. Beltrame. Measurement of the form factors of e+e- -->2([Pie symbol]+[Pie symbol]-), pp and the resonant parameters of the heavy charmonia at BES / H. Hu. Measurement of e+e- multihadronic cross section below 4

  3. Identifying chiral bands in real nuclei

    International Nuclear Information System (INIS)

    Shirinda, O.; Lawrie, E.A.

    2012-01-01

    The application of the presently used fingerprints of chiral bands (originally derived for strongly broken chirality) is investigated for real chiral systems. In particular the chiral fingerprints concerning the B(M1) staggering patterns and the energy staggering are studied. It is found that both fingerprints show considerable changes for real chiral systems, a behaviour that creates a significant risk for misinterpretation of the experimental data and can lead to a failure to identify real chiral systems. (orig.)

  4. Chiral algebras of class S

    CERN Document Server

    Beem, Christopher; Rastelli, Leonardo; van Rees, Balt C.

    2015-01-01

    Four-dimensional N=2 superconformal field theories have families of protected correlation functions that possess the structure of two-dimensional chiral algebras. In this paper, we explore the chiral algebras that arise in this manner in the context of theories of class S. The class S duality web implies nontrivial associativity properties for the corresponding chiral algebras, the structure of which is best summarized in the language of generalized topological quantum field theory. We make a number of conjectures regarding the chiral algebras associated to various strongly coupled fixed points.

  5. Ring Opening Metathesis Polymerization of Cyclopentene Using a Ruthenium Catalyst Confined by a Branched Polymer Architecture

    KAUST Repository

    Mugemana, Clement; Bukhriakov, Konstantin; Bertrand, Olivier; Vu, Khanh B.; Gohy, Jean-Francois; Hadjichristidis, Nikolaos; Rodionov, Valentin

    2016-01-01

    Multi-arm polystyrene stars functionalized with Grubbs-type catalysts in their cores were synthesized and used for the ring-opening metathesis polymerization (ROMP) of cyclopentene. The spatial confinement of the catalytic sites and the nanoscale phase separation between polystyrene and the growing polypentenamer chains lead to a dramatic inhibition of the ROMP termination and chain transfer steps. Consequently, cyclopentene polymerizations proceeded fast and with a high degree of conversion even in air. The Grubbs second generation catalyst was oxidatively inactivated under the same conditions. In contrast to conventional small-molecule catalysts, the ultimate degree of conversion of cyclopentene monomer and the polydispersity of the product polypentenamer are not affected by the temperature. This indicates that spatial confinement of the catalyst resulted in a significant change in the activation parameters for the alkene metathesis ring-opening.

  6. Ring Opening Metathesis Polymerization of Cyclopentene Using a Ruthenium Catalyst Confined by a Branched Polymer Architecture

    KAUST Repository

    Mugemana, Clement

    2016-03-22

    Multi-arm polystyrene stars functionalized with Grubbs-type catalysts in their cores were synthesized and used for the ring-opening metathesis polymerization (ROMP) of cyclopentene. The spatial confinement of the catalytic sites and the nanoscale phase separation between polystyrene and the growing polypentenamer chains lead to a dramatic inhibition of the ROMP termination and chain transfer steps. Consequently, cyclopentene polymerizations proceeded fast and with a high degree of conversion even in air. The Grubbs second generation catalyst was oxidatively inactivated under the same conditions. In contrast to conventional small-molecule catalysts, the ultimate degree of conversion of cyclopentene monomer and the polydispersity of the product polypentenamer are not affected by the temperature. This indicates that spatial confinement of the catalyst resulted in a significant change in the activation parameters for the alkene metathesis ring-opening.

  7. Synthesis of novel aryl brassinosteroids through alkene cross-metathesis and preliminary biological study

    Czech Academy of Sciences Publication Activity Database

    Kořínková, Petra; Bazgier, V.; Oklešťková, Jana; Rárová, L.; Strnad, Miroslav; Kvasnica, Miroslav

    2017-01-01

    Roč. 127, NOV (2017), s. 46-55 ISSN 0039-128X R&D Projects: GA ČR GJ15-08202Y; GA MŠk(CZ) LO1204 Institutional support: RVO:61389030 Keywords : Brassinosteroids * BRI1 receptor kinase * Cross-metathesis * Molecular docking * Organic synthesis * Plant bioassays Subject RIV: CC - Organic Chemistry OBOR OECD: Organic chemistry Impact factor: 2.282, year: 2016

  8. C-84 Selective Porphyrin Macrocycle with an Adaptable Cavity Constructed Through Alkyne Metathesis

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, C. X.; Long, H.; Zhang, W.

    2012-06-21

    A bisporphyrin macrocycle was constructed from a porphyrin-based diyne monomer in one step through alkyne metathesis. The fullerene binding studies (C{sub 60}, C{sub 70} and C{sub 84}) showed the highest binding affinity of the macrocycle for C{sub 84}, which is in great contrast to its bisporphyrin four-armed cage analogue that showed the strongest binding with C{sub 70}.

  9. Construction of Eight-Membered Carbocycles with Trisubstituted Double Bonds Using the Ring Closing Metathesis Reaction

    Directory of Open Access Journals (Sweden)

    Motoo Tori

    2010-06-01

    Full Text Available Medium sized carbocycles are particularly difficult to synthesize. Ring closing metathesis reactions (RCM have recently been applied to construct eight-membered carbocycles, but trisubstituted double bonds in the eight-membered rings are more difficult to produce using RCM reactions. In this review, model examples and our own results are cited and the importance of the preparation of suitably designed precursors is discussed. Examples of RCM reactions used in the total synthesis of natural products are also outlined.

  10. Well-defined polyethylene molecular brushes by polyhomologation and ring opening metathesis polymerization

    KAUST Repository

    Zhang, Hefeng; Gnanou, Yves; Hadjichristidis, Nikolaos

    2014-01-01

    A novel strategy using polyhomologation and ring opening metathesis polymerization (ROMP) has been developed for the synthesis of well-defined polyethylene (PE) molecular brushes. Polyhomologation was used to afford an OH-terminated PE, which after transformation to the norbornyl PE macromonomer was subjected to ROMP. Kinetics of ROMP of the PE macromonomer was studied by in situ1H NMR monitoring. The brush structure was proved from HT-GPC, 1H NMR and DSC results.

  11. Synthesis of E- and Z-trisubstituted alkenes by catalytic cross-metathesis

    Science.gov (United States)

    Nguyen, Thach T.; Koh, Ming Joo; Mann, Tyler J.; Schrock, Richard R.; Hoveyda, Amir H.

    2017-12-01

    Catalytic cross-metathesis is a central transformation in chemistry, yet corresponding methods for the stereoselective generation of acyclic trisubstituted alkenes in either the E or the Z isomeric forms are not known. The key problems are a lack of chemoselectivity—namely, the preponderance of side reactions involving only the less hindered starting alkene, resulting in homo-metathesis by-products—and the formation of short-lived methylidene complexes. By contrast, in catalytic cross-coupling, substrates are more distinct and homocoupling is less of a problem. Here we show that through cross-metathesis reactions involving E- or Z-trisubstituted alkenes, which are easily prepared from commercially available starting materials by cross-coupling reactions, many desirable and otherwise difficult-to-access linear E- or Z-trisubstituted alkenes can be synthesized efficiently and in exceptional stereoisomeric purity (up to 98 per cent E or 95 per cent Z). The utility of the strategy is demonstrated by the concise stereoselective syntheses of biologically active compounds, such as the antifungal indiacen B and the anti-inflammatory coibacin D.

  12. Simplified chiral superfield propagators for chiral constant mass superfields

    International Nuclear Information System (INIS)

    Srivastava, P.P.

    1983-01-01

    Unconstrained superfield potentials are introduced to derive Feynman rules for chiral superfields following conventional procedure which is easy and instructive. Propagators for the case when the mass parameters are constant chiral superfields are derived. The propagators reported here are very simple compared to those available in literature and allow a manageable calculation of higher loops. (Author) [pt

  13. Chiral nanophotonics chiral optical properties of plasmonic systems

    CERN Document Server

    Schäferling, Martin

    2017-01-01

    This book describes the physics behind the optical properties of plasmonic nanostructures focusing on chiral aspects. It explains in detail how the geometry determines chiral near-fields and how to tailor their shape and strength. Electromagnetic fields with strong optical chirality interact strongly with chiral molecules and, therefore, can be used for enhancing the sensitivity of chiroptical spectroscopy techniques. Besides a short review of the latest results in the field of plasmonically enhanced enantiomer discrimination, this book introduces the concept of chiral plasmonic near-field sources for enhanced chiroptical spectroscopy. The discussion of the fundamental properties of these light sources provides the theoretical basis for further optimizations and is of interest for researchers at the intersection of nano-optics, plasmonics and stereochemistry. .

  14. Reactions of rhodium(I) carbonyl chloride with olefins

    International Nuclear Information System (INIS)

    Varshavskii, Yu.S.; Kiseleva, N.V.; Cherkasova, T.G.; Buzina, N.A.; Bresler, L.S.

    1987-01-01

    The reactions of [Rh(CO) 2 Cl] 2 (Y 0 ) with cyclooctene and several other olefins (1-heptene, 1-hexene, ethylene, and cyclohexene) have been studied by IR and 13 C NMR spectroscopy. The main reaction products are the binuclear complexes Rh 2 L(CO) 3 Cl 2 (Y 1 ) and [RhL(CO)Cl] 2 (Y 2 ), where L denotes the olefin. The extent of replacement of the carbonyl groups depends on the nature of the olefin and the conditions under which the reaction is carried out (the L:Rh ratio and the removal of CO from the reaction sphere). The liquid olefins form the following series according to their ability to replace the carbonyl groups: C 8 H 14 > C 7 H 14 , C 6 H 12 > C 6 H 10 . In the presence of an excess of C 8 H 14 , Y 2 disproportionates with the formation of a dicarbonyl product, which presumably corresponds to the formula Rh(C 8 H 14 ) 2 (CO) 2 Cl (a pentacoordinate complex with a trigonal-bipyramidal structure). The 13 C signal in the NMR spectrum of a solution of Y 2 in C 8 H 14 is a singlet with σ( 13 C) 180.3 ppm, which is an indication of the rapid exchange of the carbonyl groups. Rapid exchange of the CO ligands is also observed in solutions of Y 0 in the olefins (with the exception of C 6 H 10 ). For example, the 13 C signal in the spectrum of a solution of Y 0 in C 8 H 14 is a singlet with σ( 13 C) 179.8 ppm. The spectrum of Y 0 in C 6 H 10 is a doublet with σ( 13 C) = 178.5 ppm and 1 J(CRh) = 76.3 Hz. A scheme for the interaction of Y 0 with olefins based on the conception of the trans antagonism of π-acceptor ligands has been proposed

  15. Chiral Cliffs: Investigating the Influence of Chirality on Binding Affinity.

    Science.gov (United States)

    Schneider, Nadine; Lewis, Richard A; Fechner, Nikolas; Ertl, Peter

    2018-05-11

    Chirality is understood by many as a binary concept: a molecule is either chiral or it is not. In terms of the action of a structure on polarized light, this is indeed true. When examined through the prism of molecular recognition, the answer becomes more nuanced. In this work, we investigated chiral behavior on protein-ligand binding: when does chirality make a difference in binding activity? Chirality is a property of the 3D structure, so recognition also requires an appreciation of the conformation. In many situations, the bioactive conformation is undefined. We set out to address this by defining and using several novel 2D descriptors to capture general characteristic features of the chiral center. Using machine-learning methods, we built different predictive models to estimate if a chiral pair (a set of two enantiomers) might exhibit a chiral cliff in a binding assay. A set of about 3800 chiral pairs extracted from the ChEMBL23 database was used to train and test our models. By achieving an accuracy of up to 75 %, our models provide good performance in discriminating chiral cliffs from non-cliffs. More importantly, we were able to derive some simple guidelines for when one can reasonably use a racemate and when an enantiopure compound is needed in an assay. We critically discuss our results and show detailed examples of using our guidelines. Along with this publication we provide our dataset, our novel descriptors, and the Python code to rebuild the predictive models. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Lattice regularized chiral perturbation theory

    International Nuclear Information System (INIS)

    Borasoy, Bugra; Lewis, Randy; Ouimet, Pierre-Philippe A.

    2004-01-01

    Chiral perturbation theory can be defined and regularized on a spacetime lattice. A few motivations are discussed here, and an explicit lattice Lagrangian is reviewed. A particular aspect of the connection between lattice chiral perturbation theory and lattice QCD is explored through a study of the Wess-Zumino-Witten term

  17. Ternary catalyst-olefin-hydroperoxide complexes and their contribution to epoxidation

    International Nuclear Information System (INIS)

    Svitych, R.B.; Rzhevskaya, N.N.; Buchachenko, A.L.; Yablonskij, O.P.; Petukhov, A.A.; Belyaev, V.A.

    1976-01-01

    Electron and NMR spectroscopy have been used for studying the complex formation of catalysts (Mo 5+ , Mn 2+ , Co 2+ ) in double and triple systems: metal-olefin and metal-olefin-hydroperoxide. It has been established that ions of metals form complexes with olefins in the first sphere. The formation has been proved of ternary complexes metal-olefin-hydroperoxide. The structure of the complexes has been proposed with olefins in the first and hydroperoxide in the second sphere of the metal ion. The structure explains known kinetic regularities of epoxydation and the mechanism of the formation of final products, oxide and alcohol. It has been shown that the best catalysts for epoxydation of olefins with hydroperoxides must be the compounds of the metals with an electron state of ion d 0 [ru

  18. Two-chiral component microemulsion EKC - chiral surfactant and chiral oil. Part 2: diethyl tartrate.

    Science.gov (United States)

    Kahle, Kimberly A; Foley, Joe P

    2007-08-01

    In this second study on dual-chirality microemulsions containing a chiral surfactant and a chiral oil, a less hydrophobic and lower interfacial tension chiral oil, diethyl tartrate, is employed (Part 1, Foley, J. P. et al.., Electrophoresis, DOI: 10.1002/elps.200600551). Six stereochemical combinations of dodecoxycarbonylvaline (DDCV: R, S, or racemic, 2.00% w/v), racemic 2-hexanol (1.65% v/v), and diethyl tartrate (D, L, or racemic, 0.88% v/v) were examined as pseudostationary phases (PSPs) for the enantioseparation of six chiral pharmaceutical compounds: pseudoephedrine, ephedrine, N-methyl ephedrine, metoprolol, synephrine, and atenolol. Average efficiencies increased with the addition of a chiral oil to R-DDCV PSP formulations. Modest improvements in resolution and enantioselectivity (alpha(enant)) were achieved with two-chiral-component systems over the one-chiral-component microemulsion. Slight enantioselective synergies were confirmed using a thermodynamic model. Results obtained in this study are compared to those obtained in Part 1 as well as those obtained with chiral MEEKC using an achiral, low-interfacial-tension oil (ethyl acetate). Dual-chirality microemulsions with the more hydrophobic oil dibutyl tartrate yielded, relative to diethyl tartrate, higher efficiencies (100,000-134,000 vs. 80,800-94,300), but lower resolution (1.64-1.91 vs. 2.08-2.21) due to lower enantioselectivities (1.060-1.067 vs. 1.078-1.081). Atenolol enantiomers could not be separated with the dibutyl tartrate-based microemulsions but were partially resolved using diethyl tartrate microemulsions. A comparable single-chirality microemulsion based on the achiral oil ethyl acetate yielded, relative to diethyl tartrate, lower efficiency (78 300 vs. 91 600), higher resolution (1.99 vs. 1.83), and similar enantioselectivities.

  19. Pd(II)-Catalyzed Olefination of sp3 C–H Bonds

    Science.gov (United States)

    Wasa, Masayuki; Engle, Keary M.; Yu, Jin-Quan

    2010-01-01

    The first Pd(II)-catalyzed sp3 C–H olefination reaction has been developed using N-arylamide directing groups. Following olefination, the resulting intermediates were found to undergo rapid 1,4-addition to give the corresponding γ lactams. Notably, this method was effective with substrates containing α-hydrogen atoms and could be applied to effect methylene C–H olefination of cyclopropane substrates. PMID:20187642

  20. Direct olefination of fluorinated benzothiadiazoles: a new entry to optoelectronic materials.

    Science.gov (United States)

    Xiao, Yu-Lan; Zhang, Bo; He, Chun-Yang; Zhang, Xingang

    2014-04-14

    Fluorinated olefin-containing benzothiadiazoles have important applications in optoelectronic materials. Herein, we reported the direct olefination of fluorinated benzothiadiazoles, as catalyzed by palladium. The reaction proceeds under mild reaction conditions and shows high functional-group compatibility. A preliminary study of the properties of the resulting symmetrical and unsymmetrical olefin-containing fluorinated benzothiadiazoles in red-light-emitting dyes has also been conducted. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Methanol conversion to lower olefins over RHO type zeolite

    KAUST Repository

    Masih, Dilshad

    2013-07-01

    Eight-membered ring small-pore zeolite of RHO-type topology has been synthesized, characterized and tested for methanol-to-olefin (MTO) reaction. The zeolite was hydrothermally crystallized from the gel with Si/Al ratio of 5.0. It showed a high BET specific surface area (812 m2 g-1), micropore volume (0.429 cm3 g-1), and acid amount (2.53 mmol g-1). Scanning electron microscopy observations showed small crystallites of about 1 μm. The zeolite was active for MTO reaction with 100% methanol conversions at 623-723 K, whereas selectivity to lower olefins changed with time. © 2013 Elsevier B.V.

  2. Methyltrioxorhenium as catalyst of a novel aldehyde olefination

    Energy Technology Data Exchange (ETDEWEB)

    Herrmann, W.A. (Technische Univ. Muenchen, Garching (Germany). Anorganisch-Chemisches Inst.); Wang Mei (Academia Sinica, Dalian Inst. of Chemical Physics (China))

    1991-12-01

    From aldehydes or cyclic ketones, diazoalkanes, and teritiary phosphanes, olefins may be prepared with MTO as catalyst. In particular, diazoacetates and -malonates (R{sup 2}, R{sup 3} = H, CO{sub 2}Et, or 2 x CO{sub 2}Me) can be transformed into olefins with aliphatic and aromatic aldehydes (R{sup 1} = iPr, trans-PhCH=CH, Ph, 4-NO{sub 2}C{sub 6}H{sub 4}, etc.). Readily accessible starting materials, easy handling, mild reaction conditions, and good yields characterize the new synthesis method. (R' = Ph, 3-C{sub 6}H{sub 4}SO{sub 3}Na, nBu.) (orig.).

  3. A three-membered ring approach to carbonyl olefination.

    Science.gov (United States)

    Niyomchon, Supaporn; Oppedisano, Alberto; Aillard, Paul; Maulide, Nuno

    2017-10-23

    The carbon-carbon double bond, with its diverse and multifaceted reactivity, occupies a prominent position in organic synthesis. Although a variety of simple alkenes are readily available, the mild and chemoselective introduction of a unit of unsaturation into a functionalized organic molecule remains an ongoing area of research, and the olefination of carbonyl compounds is a cornerstone of such approaches. Here we show the direct olefination of hydrazones via the intermediacy of three-membered ring species generated by addition of sulfoxonium ylides, departing from the general dogma of alkenes synthesis from carbonyls. Moreover, the mild reaction conditions and operational simplicity of the transformation render the methodology appealing from a practical point of view.

  4. Flatspace chiral supergravity

    Science.gov (United States)

    Bagchi, Arjun; Basu, Rudranil; Detournary, Stéphane; Parekh, Pulastya

    2018-05-01

    We propose a holographic duality between a 2 dimensional (2d) chiral superconformal field theory and a certain theory of supergravity in 3d with flatspace boundary conditions that is obtained as a double scaling limit of a parity breaking theory of supergravity. We show how the asymptotic symmetries of the bulk theory reduce from the "despotic" super Bondi-Metzner-Sachs algebra (or equivalently the inhomogeneous super Galilean conformal algebra) to a single copy of the super-Virasoro algebra in this limit and also reproduce the same reduction from a study of null vectors in the putative 2d dual field theory.

  5. Chiral Nuclear Dynamics II

    CERN Document Server

    Rho, Mannque

    2008-01-01

    This is the sequel to the first volume to treat in one effective field theory framework the physics of strongly interacting matter under extreme conditions. This is vital for understanding the high temperature phenomena taking place in relativistic heavy ion collisions and in the early Universe, as well as the high-density matter predicted to be present in compact stars. The underlying thesis is that what governs hadronic properties in a heat bath and/or a dense medium is hidden local symmetry which emerges from chiral dynamics of light quark systems and from the duality between QCD in 4D and

  6. Decarbonisation of olefin processes using biomass pyrolysis oil

    International Nuclear Information System (INIS)

    Sharifzadeh, M.; Wang, L.; Shah, N.

    2015-01-01

    Highlights: • Decarbonization of olefin processes using biomass pyrolysis oil was proposed. • The decarbonization is based on integrated catalytic processing of bio-oil. • The retrofitted process features significant economic and environmental advantages. - Abstract: An imperative step toward decarbonisation of current industrial processes is to substitute their petroleum-derived feedstocks with biomass and biomass-derived feedstocks. For decarbonisation of the petrochemical industry, integrated catalytic processing of biomass pyrolysis oil (also known as bio-oil) is an enabling technology. This is because, under certain conditions, the reaction products form a mixture consisting of olefins and aromatics, which are very similar to the products of naphtha hydro-cracking in the conventional olefin processes. These synergies suggest that the catalytic bio-oil upgrading reactors can be seamlessly integrated to the subsequent separation network with minimal retrofitting costs. In addition, the integrated catalytic processing provides a high degree of flexibility for optimization of different products in response to market fluctuations. With the aim of assessing the techno-economic viability of this pathway, five scenarios in which different fractions of bio-oil (water soluble/water insoluble) were processed with different degrees of hydrogenation were studied in the present research. The results showed that such a retrofit is not only economically viable, but also provides a high degree of flexibility to the process, and contributes to decarbonisation of olefin infrastructures. Up to 44% reductions in greenhouse gas emissions were observed in several scenarios. In addition, it was shown that hydrogen prices lower than 6 $/kg will result in bio-based chemicals which are cheaper than equivalent petrochemicals. Alternatively, for higher hydrogen prices, it is possible to reform the water insoluble phase of bio-oil and produce bio-based chemicals, cheaper than

  7. Surface science of single-site heterogeneous olefin polymerization catalysts

    OpenAIRE

    Kim, Seong H.; Somorjai, Gabor A.

    2006-01-01

    This article reviews the surface science of the heterogeneous olefin polymerization catalysts. The specific focus is on how to prepare and characterize stereochemically specific heterogeneous model catalysts for the Ziegler–Natta polymerization. Under clean, ultra-high vacuum conditions, low-energy electron irradiation during the chemical vapor deposition of model Ziegler–Natta catalysts can be used to create a “single-site” catalyst film with a surface structure that produces only isotactic ...

  8. Retrofit with membrane the Paraffin/Olefin separation

    Energy Technology Data Exchange (ETDEWEB)

    Motelica, A.; Bruinsma, O.S.L.; Kreiter, R.; Den Exter, M.J.; Vente, J.F. [ECN Biomass and Energy Efficiency, Petten (Netherlands)

    2012-10-15

    Olefins, such as ethylene, propylene, and butadiene, are among the most produced intermediates in petrochemical industry. They are produced from a wide range of hydrocarbon feedstocks (ethane, propane, butane, naphtha, gas oil) via a cracking process. The last step in this process is the separation of olefins from other hydrocarbons, which is traditionally performed with distillation. As the physicochemical properties, such as volatility and boiling point, of the compounds are very similar, the purification becomes capital and energy intensive. For example, the top of an ethylene/ethane distillation column needs to be chilled to -30C and this requires large amount of electric energy consumption. The separation of butadiene from the C4-fraction is performed with the aid of an additional solvent. This solvent has to be regenerated at the cost of additional high temperature steam. To overcome these separation disadvantages of olefin/paraffin separation, different separation methods have been investigated and proposed in recent years. Suggested options are based on better heat integration of the overall process, or on novel separation systems such as Heat Integrated Distillation Columns, membrane separation, adsorption-desorption systems or on hybrid separation methods, for example, distillation combined with membrane separation.

  9. Life cycle assessment of energy consumption and GHG emissions of olefins production from alternative resources in China

    International Nuclear Information System (INIS)

    Xiang, Dong; Yang, Siyu; Li, Xiuxi; Qian, Yu

    2015-01-01

    Highlights: • Conduct a life cycle energy use and GHG emissions of olefins production processes. • Analyse effects of carbon capture and efficiency on alternative olefins production. • Analyse life cycle performance of Chinese olefins industry in three key periods. • Present the advantages and challenges of alternative olefins routes. - Abstract: Olefins are important platform chemicals widely used in industry. In terms of the short supply of oil resources, natural gas and coal are two significant alternative feedstocks. In this paper, energy consumption and GHG emissions of olefins production are analysed with life cycle assessment methods. Results showed the energy consumption and GHG emissions of natural gas-to-olefins are roughly equivalent to those of oil-to-olefins, while coal-to-olefins suffers from higher energy consumption and serious GHG emissions, including 5793 kg eq. CO 2 /t olefins of direct emissions and 5714 kg eq. CO 2 /t olefins of indirect emissions. To address the problem, the effect of carbon capture on coal-to-olefins is investigated. In comprehensive consideration of energy utilization, environmental impact, and economic benefit, the coal-to-olefins with 80% CO 2 capture of the direct emissions is found to be an appropriate choice. With this carbon capture configuration, the direct emissions of the coal-to-olefins are reduced to 1161 kg eq. CO 2 /t olefins. However, the indirect emissions are still not captured, which should be strictly monitored and significantly reduced. Finally, a scenario analysis is conducted to estimate resource utilization and GHG emissions of olefins production of China in 2020. Several suggestions are also proposed for policy making on the sustainable development of olefins industry

  10. Nanoscale chirality in metal and semiconductor nanoparticles.

    Science.gov (United States)

    Kumar, Jatish; Thomas, K George; Liz-Marzán, Luis M

    2016-10-18

    The field of chirality has recently seen a rejuvenation due to the observation of chirality in inorganic nanomaterials. The advancements in understanding the origin of nanoscale chirality and the potential applications of chiroptical nanomaterials in the areas of optics, catalysis and biosensing, among others, have opened up new avenues toward new concepts and design of novel materials. In this article, we review the concept of nanoscale chirality in metal nanoclusters and semiconductor quantum dots, then focus on recent experimental and theoretical advances in chiral metal nanoparticles and plasmonic chirality. Selected examples of potential applications and an outlook on the research on chiral nanomaterials are additionally provided.

  11. Chiral perturbation theory

    International Nuclear Information System (INIS)

    Harada, Masayasu

    2009-01-01

    Chiral perturbation theory has been used for great number of phenomenological analyses in low energy QCD as well as the lattice QCD analyses since the creation of the theory by Weinberg in 1979 followed by its consolidation by Gasser and Leutwyler in 1984 and 85. The theory is now the highly established one as the approach based on the effective field theory to search for Green function including quantum correlations in the frame of the systematic expansion technique using Lagrangian which includes all of the terms allowed by the symmetry. This review has been intended to describe how systematically physical quantities are calculated in the framework of the chiral symmetry. Consequently many of the various phenomenological analyses are not taken up here for which other reports are to be referred. Further views are foreseen to be developed based on the theory in addition to numbers of results reported up to the present. Finally π-π scattering is taken up to discuss to what energy scale the theory is available. (S. Funahashi)

  12. Chiral quantum optics.

    Science.gov (United States)

    Lodahl, Peter; Mahmoodian, Sahand; Stobbe, Søren; Rauschenbeutel, Arno; Schneeweiss, Philipp; Volz, Jürgen; Pichler, Hannes; Zoller, Peter

    2017-01-25

    Advanced photonic nanostructures are currently revolutionizing the optics and photonics that underpin applications ranging from light technology to quantum-information processing. The strong light confinement in these structures can lock the local polarization of the light to its propagation direction, leading to propagation-direction-dependent emission, scattering and absorption of photons by quantum emitters. The possibility of such a propagation-direction-dependent, or chiral, light-matter interaction is not accounted for in standard quantum optics and its recent discovery brought about the research field of chiral quantum optics. The latter offers fundamentally new functionalities and applications: it enables the assembly of non-reciprocal single-photon devices that can be operated in a quantum superposition of two or more of their operational states and the realization of deterministic spin-photon interfaces. Moreover, engineered directional photonic reservoirs could lead to the development of complex quantum networks that, for example, could simulate novel classes of quantum many-body systems.

  13. Stereoselective Synthesis of Functionalized 1,3-Disubstituted Isoindolines via Rh(III)-Catalyzed Tandem Oxidative Olefination-Cyclization of 4-Aryl-cyclic Sulfamidate-5-Carboxylates.

    Science.gov (United States)

    Achary, Raghavendra; Jung, In-A; Son, Se-Mi; Lee, Hyeon-Kyu

    2017-07-21

    A new method for the direct, stereoselective synthesis of highly functionalized 1,3-disubstituted isoindolines 6 from enantiomerically enriched cyclic 4-aryl-sulfamidate-5-carboxylates (5) is described. The process involves sulfamidate directed, Rh(III)-catalyzed tandem ortho C-H olefination of the 4-aryl-sulfamidate-5-carboxylates and subsequent cyclization by aza-Michael addition. In the reaction, which generates trans-1,3-disubstituted isoindolines exclusively, the configurational integrity of the stereogenic center in the starting cyclic sulfamidate is completely retained in the product. Examples are provided which show that the cyclic sulfamidate moiety not only serves as a chiral directing group but also as a versatile handle for further functionalization of the generated isoindoline ring system.

  14. Chiral perturbation theory with nucleons

    International Nuclear Information System (INIS)

    Meissner, U.G.

    1991-09-01

    I review the constraints posed on the interactions of pions, nucleons and photons by the spontaneously broken chiral symmetry of QCD. The framework to perform these calculations, chiral perturbation theory, is briefly discussed in the meson sector. The method is a simultaneous expansion of the Greens functions in powers of external moments and quark masses around the massless case, the chiral limit. To perform this expansion, use is made of a phenomenological Lagrangian which encodes the Ward-identities and pertinent symmetries of QCD. The concept of chiral power counting is introduced. The main part of the lectures of consists in describing how to include baryons (nucleons) and how the chiral structure is modified by the fact that the nucleon mass in the chiral limit does not vanish. Particular emphasis is put on working out applications to show the strengths and limitations of the methods. Some processes which are discussed are threshold photopion production, low-energy compton scattering off nucleons, πN scattering and the σ-term. The implications of the broken chiral symmetry on the nuclear forces are briefly described. An alternative approach, in which the baryons are treated as very heavy fields, is touched upon

  15. Chiral recognition in separation science: an overview.

    Science.gov (United States)

    Scriba, Gerhard K E

    2013-01-01

    Chiral recognition phenomena play an important role in nature as well as analytical separation sciences. In separation sciences such as chromatography and capillary electrophoresis, enantiospecific interactions between the enantiomers of an analyte and the chiral selector are required in order to observe enantioseparations. Due to the large structural variety of chiral selectors applied, different mechanisms and structural features contribute to the chiral recognition process. This chapter briefly illustrates the current models of the enantiospecific recognition on the structural basics of various chiral selectors.

  16. Ruthenium-catalyzed intramolecular metathesis of dienes and its application in the synthesis of bridged and spiro azabicycles

    Science.gov (United States)

    Kuznetsov, N. Yu; Bubnov, Yu N.

    2015-07-01

    The review presents a historical excursion into catalytic alkene metathesis, covering the problems of history of the discovery of this process, as well as investigations on the properties, structure and reactivity of the most popular ruthenium catalysts for metathesis, mechanism of their action and decomposition. The main part covers studies devoted to the syntheses of bridged azabicyclic and 1-azaspirocyclic compounds comprising the intramolecular metathesis of dienes as the key step. The formation of a bicyclic skeleton of a series of natural bridged (cocaine, ferruginine, calystegines, and anatoxin-a) and spiro (pinnaic acids, halichlorine, hystrionicotoxin, and cephalotaxine) azabicycles, as well as their analogues and compounds with larger rings is demonstrated. The methods for the synthesis of diene precursors and the conditions for final assembling of the bicyclic compounds are considered in detail. The generalization of the literature data allows one to efficiently carry out the mentioned process taking into account the most important features. The bibliography includes 129 references.

  17. Ruthenium-catalyzed intramolecular metathesis of dienes and its application in the synthesis of bridged and spiro azabicycles

    International Nuclear Information System (INIS)

    Kuznetsov, N Yu; Bubnov, Yu N

    2015-01-01

    The review presents a historical excursion into catalytic alkene metathesis, covering the problems of history of the discovery of this process, as well as investigations on the properties, structure and reactivity of the most popular ruthenium catalysts for metathesis, mechanism of their action and decomposition. The main part covers studies devoted to the syntheses of bridged azabicyclic and 1-azaspirocyclic compounds comprising the intramolecular metathesis of dienes as the key step. The formation of a bicyclic skeleton of a series of natural bridged (cocaine, ferruginine, calystegines, and anatoxin-a) and spiro (pinnaic acids, halichlorine, hystrionicotoxin, and cephalotaxine) azabicycles, as well as their analogues and compounds with larger rings is demonstrated. The methods for the synthesis of diene precursors and the conditions for final assembling of the bicyclic compounds are considered in detail. The generalization of the literature data allows one to efficiently carry out the mentioned process taking into account the most important features. The bibliography includes 129 references

  18. Metathesis Polymerization Reactions Induced by the Bimetallic Complex (Ph4P2[W2(μ-Br3Br6

    Directory of Open Access Journals (Sweden)

    Despoina Chriti

    2015-12-01

    Full Text Available The reactivity of the bimetallic complex (Ph4P2[W2(μ-Br3Br6] ({W 2.5 W}7+, a′2e3 towards ring opening metathesis polymerization (ROMP of norbornene (NBE and some of its derivatives, as well as the mechanistically related metathesis polymerization of phenylacetylene (PA, is presented. Our results show that addition of a silver salt (AgBF4 is necessary for the activation of the ditungsten complex. Polymerization of PA proceeds smoothly in tetrahydrofuran (THF producing polyphenylacetylene (PPA in high yields. On the other hand, the ROMP of NBE and its derivatives is more efficient in CH2Cl2, providing high yields of polymers. 13C Cross Polarization Magic Angle Spinning (CPMAS spectra of insoluble polynorbornadiene (PNBD and polydicyclopentadiene (PDCPD revealed the operation of two mechanisms (metathetic and radical for cross-linking, with the metathesis pathway prevailing.

  19. New remarks on chiral bosonization

    International Nuclear Information System (INIS)

    Souza Dutra, A. de

    1992-01-01

    We discuss a certain duality between the constraints appearing in ordinary Lagrangian density and its first order counterpart for the gauged Siegel chiral boson. It is demonstrated the equivalence, at the classical level, of the two versions of the gauged Siegel chiral boson to its corresponding gauged Floreanini-Jackiw chiral bosons. It is also argued that the most general constrained Lagrangian density, that leads to a bosonic field obeying a first order differential equation of motion and preserve simultaneously Lorentz invariance, is just the Floreanini-Jackiw one. (author)

  20. Vector mesons and chiral symmetry

    International Nuclear Information System (INIS)

    Ecker, G.

    1989-01-01

    The ambiguities in the off-shell behaviour of spin-1 exchange can be resolved to O(p 4 ) in the chiral low-energy expansion if the asymptotic behaviour of QCD is properly incorporated. As a consequence, the chiral version of vector (and axial-vector) meson dominance is model independent. Additional high-energy constraints motivated by QCD determine the V,A resonance couplings uniquely. In particular, QCD in its effective chiral realization sucessfully predicts Γ(ρ→2π). 10 refs. (Author)

  1. Nonlinear spectroscopic studies of chiral media

    International Nuclear Information System (INIS)

    Belkin, Mikhail Alexandrovich

    2004-01-01

    Molecular chirality plays an important role in chemistry, biology, and medicine. Traditional optical techniques for probing chirality, such as circular dichroism and Raman optical activity rely on electric-dipole forbidden transitions. As a result, their intrinsic low sensitivity limits their use to probe bulk chirality rather than chiral surfaces, monolayers or thin films often important for chemical or biological systems. Contrary to the traditional chirality probes, chiral signal in sum-frequency generation (SFG) is electric-dipole allowed both on chiral surface and in chiral bulk making it a much more promising tool for probing molecular chirality. SFG from a chiral medium was first proposed in 1965, but had never been experimentally confirmed until this thesis work was performed. This thesis describes a set of experiments successfully demonstrating that chiral SFG responses from chiral monolayers and liquids are observable. It shows that, with tunable inputs, SFG can be used as a sensitive spectroscopic tool to probe chirality in both electronic and vibrational resonances of chiral molecules. The monolayer sensitivity is feasible in both cases. It also discusses the relevant theoretical models explaining the origin and the strength of the chiral signal in vibrational and electronic SFG spectroscopies

  2. Effect of Support on Metathesis of n-Decane: Drastic Improvement in Alkane Metathesis with WMe5 Linked to Silica-Alumina

    KAUST Repository

    Samantaray, Manoja

    2015-03-11

    [WMe6] (1) supported on the surface of SiO2-Al2O3(500) (2) has been extensively characterized by solid-state NMR spectroscopy, elemental analysis, and gas quantification, which clearly reveal the formation of a mixture of monopodal and bipodal species with the migration of methyl from W to Al. The supported species SiO2-Al2O3(500) (2) transformed at 120°C into two types of carbynic centers, one of which is cationic and the other neutral. These species are very efficient for the metathesis of n-decane. Comparison with already-synthesized neutral bipodal tungsten indicates that the high increase in activity is due to the cationic character of the grafted tungsten.

  3. Effect of Support on Metathesis of n-Decane: Drastic Improvement in Alkane Metathesis with WMe5 Linked to Silica-Alumina

    KAUST Repository

    Samantaray, Manoja; Dey, Raju; Abou-Hamad, Edy; Hamieh, Ali Imad Ali; Basset, Jean-Marie

    2015-01-01

    [WMe6] (1) supported on the surface of SiO2-Al2O3(500) (2) has been extensively characterized by solid-state NMR spectroscopy, elemental analysis, and gas quantification, which clearly reveal the formation of a mixture of monopodal and bipodal species with the migration of methyl from W to Al. The supported species SiO2-Al2O3(500) (2) transformed at 120°C into two types of carbynic centers, one of which is cationic and the other neutral. These species are very efficient for the metathesis of n-decane. Comparison with already-synthesized neutral bipodal tungsten indicates that the high increase in activity is due to the cationic character of the grafted tungsten.

  4. Palladium-Catalyzed ortho-Olefination of Phenyl Acetic and Phenyl Propylacetic Esters via C-H Bond Activation.

    Science.gov (United States)

    Hu, Jundie; Guan, Mingyu; Han, Jian; Huang, Zhi-Bin; Shi, Da-Qing; Zhao, Yingsheng

    2015-08-21

    A highly regioselective palladium-catalyzed ester-directed ortho-olefination of phenyl acetic and propionic esters with olefins via C-H bond activation has been developed. A wide variety of phenyl acetic and propionic esters were tolerated in this transformation, affording the corresponding olefinated aromatic compounds. The ortho-olefination of heterocyclic acetic and propionic esters also took place smoothly giving the products in good yields, thus proving the potential utility of this protocol in synthetic chemistry.

  5. Synthesis and Ring-Opening Metathesis Polymerization of Second-Generation Dendronized Poly(ether Monomers Initiated by Ruthenium Carbenes

    Directory of Open Access Journals (Sweden)

    Guzmán Pablo E.

    2016-03-01

    Full Text Available The Ring-Opening Metathesis Polymerization (ROMP of second-generation dendronized monomers is described. Using the highly active and fast-initiating third-generation ruthenium complex [(H2IMes(pyr2Cl2RuCHPh], moderate to high molecular weight polymers (430-2230 kDa are efficiently synthesized with low dispersities (Ð = 1.01-1.17. This study highlights the power of the metathesis approach toward polymer synthesis in a context where monomer structure can significantly impede polymerization.

  6. Deformed chiral nucleons

    Energy Technology Data Exchange (ETDEWEB)

    Price, C E; Shepard, J R [Colorado Univ., Boulder (USA). Dept. of Physics

    1991-04-18

    We compute properties of the nucleon in a hybrid chiral model based on the linear {sigma}-model with quark degrees of freedom treated explicity. In contrast to previous calculations, we do not use the hedgehog ansatz. Instead we solve self-consistently for a state with well defined spin and isospin projections. We allow this state to be deformed and find that, although d- and g-state admixtures in the predominantly s-state single quark wave functions are not large, they have profound effects on many nucleon properties including magnetic moments and g{sub A}. Our best fit parameters provide excellent agreement with experiment but are much different from those determined in hedgehog calculations. (orig.).

  7. Amino Acids and Chirality

    Science.gov (United States)

    Cook, Jamie E.

    2012-01-01

    Amino acids are among the most heavily studied organic compound class in carbonaceous chondrites. The abundance, distributions, enantiomeric compositions, and stable isotopic ratios of amino acids have been determined in carbonaceous chondrites fi'om a range of classes and petrographic types, with interesting correlations observed between these properties and the class and typc of the chondritcs. In particular, isomeric distributions appear to correlate with parent bodies (chondrite class). In addition, certain chiral amino acids are found in enantiomeric excess in some chondrites. The delivery of these enantiomeric excesses to the early Earth may have contributed to the origin of the homochirality that is central to life on Earth today. This talk will explore the amino acids in carbonaceous chondritcs and their relevance to the origin of life.

  8. Chiral fermions on the lattice

    International Nuclear Information System (INIS)

    Randjbar Daemi, S.; Strathdee, J.

    1995-01-01

    The overlap approach to chiral gauge theories on arbitrary D-dimensional lattices is studied. The doubling problem and its relation to chiral anomalies for D = 2 and 4 is examined. In each case it is shown that the doublers can be eliminated and the well known perturbative results for chiral anomalies can be recovered. We also consider the multi-flavour case and give the general criteria for the construction of anomaly free chiral gauge theories on arbitrary lattices. We calculate the second order terms in a continuum approximation to the overlap formula in D dimensions and show that they coincide with the bilinear part of the effective action of D-dimensional Weyl fermions coupled to a background gauge field. Finally, using the same formalism we reproduce the correct Lorentz, diffeomorphism and gauge anomalies in the coupling of a Weyl fermion to 2-dimensional gravitation and Maxwell fields. (author). 15 refs

  9. Switching of chirality by light

    NARCIS (Netherlands)

    Feringa, B.L.; Schoevaars, A.M; Jager, W.F.; de Lange, B.; Huck, N.P.M.

    1996-01-01

    Optically active photoresponsive molecules are described by which control of chirality is achieved by light. These chiroptical molecular switches are based on inherently dissymmetric overcrowded alkenes and the synthesis, resolution and dynamic stereochemical properties are discussed. Introduction

  10. Chiral dynamics with (nonstrange quarks

    Directory of Open Access Journals (Sweden)

    Kubis Bastian

    2017-01-01

    Full Text Available We review the results and achievements of the project B.3. Topics addressed include pion photoproduction off the proton and off deuterium, three-flavor chiral perturbation theory studies, chiral symmetry tests in Goldstone boson decays, the development of unitarized chiral perturbation theory to next-to-leading order, the two-pole structure of the Λ(1405, the dynamical generation of the lowest S11 resonances, the theory of hadronic atoms and its application to various systems, precision studies in light-meson decays based on dispersion theory, the Roy–Steiner analysis of pion–nucleon scattering, a high-precision extraction of the elusive pion–nucleon σ-term, and aspects of chiral dynamics in few-nucleon systems.

  11. Chiral topological insulator of magnons

    Science.gov (United States)

    Li, Bo; Kovalev, Alexey A.

    2018-05-01

    We propose a magnon realization of 3D topological insulator in the AIII (chiral symmetry) topological class. The topological magnon gap opens due to the presence of Dzyaloshinskii-Moriya interactions. The existence of the topological invariant is established by calculating the bulk winding number of the system. Within our model, the surface magnon Dirac cone is protected by the sublattice chiral symmetry. By analyzing the magnon surface modes, we confirm that the backscattering is prohibited. By weakly breaking the chiral symmetry, we observe the magnon Hall response on the surface due to opening of the gap. Finally, we show that by changing certain parameters, the system can be tuned between the chiral topological insulator, three-dimensional magnon anomalous Hall, and Weyl magnon phases.

  12. Review of chiral perturbation theory

    Indian Academy of Sciences (India)

    Abstract. A review of chiral perturbation theory and recent developments on the comparison of its predictions with experiment is presented. Some interesting topics with scope for further elaboration are touched upon.

  13. Spiro annulation of cage polycycles via Grignard reaction and ring-closing metathesis as key steps

    Directory of Open Access Journals (Sweden)

    Sambasivarao Kotha

    2015-08-01

    Full Text Available A simple synthetic strategy to C2-symmetric bis-spiro-pyrano cage compound 7 involving ring-closing metathesis is reported. The hexacyclic dione 10 was prepared from simple and readily available starting materials such as 1,4-naphthoquinone and cyclopentadiene. The synthesis of an unprecedented octacyclic cage compound through intramolecular Diels–Alder (DA reaction as a key step is described. The structures of three new cage compounds 7, 12 and 18 were confirmed by single crystal X-ray diffraction studies.

  14. 76 FR 5319 - Regulation of Fuel and Fuel Additives: Alternative Test Method for Olefins in Gasoline

    Science.gov (United States)

    2011-01-31

    ... Regulation of Fuel and Fuel Additives: Alternative Test Method for Olefins in Gasoline AGENCY: Environmental... gasoline. This proposed rule will provide flexibility to the regulated community by allowing an additional... A. Alternative Test Method for Olefins in Gasoline III. Statutory and Executive Order Reviews A...

  15. 76 FR 65382 - Regulation of Fuel and Fuel Additives: Alternative Test Method for Olefins in Gasoline

    Science.gov (United States)

    2011-10-21

    ... Regulation of Fuel and Fuel Additives: Alternative Test Method for Olefins in Gasoline AGENCY: Environmental... gasoline. This final rule will provide flexibility to the regulated community by allowing an additional... Method for Olefins in Gasoline III. Statutory and Executive Order Reviews A. Executive Order 12866...

  16. Oxidative cracking of n-hexane: a catalytic pathway to olefins

    NARCIS (Netherlands)

    Boyadjian, C.A.

    2010-01-01

    Steam cracking, the major, current existing route for light olefin production, is the most energy consuming process in the chemical industry. The need for an energy efficient processes, urged substantial research work for the development of new catalytic technologies for light olefin production.

  17. Rhodium-Catalyzed Regioselective C7-Olefination of Indazoles Using an N-Amide Directing Group.

    Science.gov (United States)

    Guo, Lei; Chen, Yanyu; Zhang, Rong; Peng, Qiujun; Xu, Lanting; Pan, Xianhua

    2017-02-01

    A rhodium-catalyzed regioselective C-H olefination of indazole is described. This protocol relies on the use of an efficient and removable N,N-diisopropylcarbamoyl directing group, which offers facile access to C7-olefinated indazoles with high regioselectivity, ample substrate scope and broad functional group tolerance. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Redox-Neutral Rh(III)-Catalyzed Olefination of Carboxamides with Trifluoromethyl Allylic Carbonate.

    Science.gov (United States)

    Park, Jihye; Han, Sangil; Jeon, Mijin; Mishra, Neeraj Kumar; Lee, Seok-Yong; Lee, Jong Suk; Kwak, Jong Hwan; Um, Sung Hee; Kim, In Su

    2016-11-18

    The rhodium(III)-catalyzed olefination of various carboxamides with α-CF 3 -substituted allylic carbonate is described. This reaction provides direct access to linear CF 3 -allyl frameworks with complete trans-selectivity. In particular, a rhodium catalyst provided Heck-type γ-CF 3 -allylation products via the β-O-elimination of rhodacycle intermediate and subsequent olefin migration process.

  19. Chirality-controlled crystallization via screw dislocations.

    Science.gov (United States)

    Sung, Baeckkyoung; de la Cotte, Alexis; Grelet, Eric

    2018-04-11

    Chirality plays an important role in science from enantiomeric separation in chemistry to chiral plasmonics in nanotechnology. However, the understanding of chirality amplification from chiral building blocks to ordered helical superstructures remains a challenge. Here, we demonstrate that topological defects, such as screw dislocations, can drive the chirality transfer from particle to supramolecular structure level during the crystallization process. By using a model system of chiral particles, which enables direct imaging of single particle incorporation into growing crystals, we show that the crystallization kinetic pathway is the key parameter for monitoring, via the defects, the chirality amplification of the crystalline structures from racemic to predominantly homohelical. We provide an explanation based on the interplay between geometrical frustration, racemization induced by thermal fluctuations, and particle chirality. Our results demonstrate that screw dislocations not only promote the growth, but also control the chiral morphology and therefore the functionality of crystalline states.

  20. Chiral thermodynamics of nuclear matter

    Energy Technology Data Exchange (ETDEWEB)

    Fiorilla, Salvatore

    2012-10-23

    The equation of state of nuclear matter is calculated at finite temperature in the framework of in-medium chiral perturbation theory up to three-loop order. The dependence of its thermodynamic properties on the isospin-asymmetry is investigated. The chiral quark condensate is evaluated for symmetric nuclear matter. Its behaviour as a function of density and temperature sets important nuclear physics constraints for the QCD phase diagram.

  1. Homogenization of resonant chiral metamaterials

    DEFF Research Database (Denmark)

    Andryieuski, Andrei; Menzel, C.; Rockstuhl, Carsten

    2010-01-01

    Homogenization of metamaterials is a crucial issue as it allows to describe their optical response in terms of effective wave parameters as, e.g., propagation constants. In this paper we consider the possible homogenization of chiral metamaterials. We show that for meta-atoms of a certain size...... an analytical criterion for performing the homogenization and a tool to predict the homogenization limit. We show that strong coupling between meta-atoms of chiral metamaterials may prevent their homogenization at all....

  2. Chiral thermodynamics of nuclear matter

    International Nuclear Information System (INIS)

    Fiorilla, Salvatore

    2012-01-01

    The equation of state of nuclear matter is calculated at finite temperature in the framework of in-medium chiral perturbation theory up to three-loop order. The dependence of its thermodynamic properties on the isospin-asymmetry is investigated. The chiral quark condensate is evaluated for symmetric nuclear matter. Its behaviour as a function of density and temperature sets important nuclear physics constraints for the QCD phase diagram.

  3. Macdonald index and chiral algebra

    Science.gov (United States)

    Song, Jaewon

    2017-08-01

    For any 4d N = 2 SCFT, there is a subsector described by a 2d chiral algebra. The vacuum character of the chiral algebra reproduces the Schur index of the corresponding 4d theory. The Macdonald index counts the same set of operators as the Schur index, but the former has one more fugacity than the latter. We conjecture a prescription to obtain the Macdonald index from the chiral algebra. The vacuum module admits a filtration, from which we construct an associated graded vector space. From this grading, we conjecture a notion of refined character for the vacuum module of a chiral algebra, which reproduces the Macdonald index. We test this prescription for the Argyres-Douglas theories of type ( A 1 , A 2 n ) and ( A 1 , D 2 n+1) where the chiral algebras are given by Virasoro and \\widehat{su}(2) affine Kac-Moody algebra. When the chiral algebra has more than one family of generators, our prescription requires a knowledge of the generators from the 4d.

  4. Adsorption heats of olefins on supported MoO3/Al2O3 catalists

    International Nuclear Information System (INIS)

    Grinev, V.E.; Madden, M.; Khalit, V.A.; Aptekar', E.L.; Aldag, A.; Krylov, O.V.

    1983-01-01

    Adsorption heats of C 2 H 4 , C 3 H 6 and C 4 H 8 on supported MoO 3 /Al 2 O 3 catalysts containing 6, 10 and 15 wt. % of MoO 3 at 25, 77 and 195 deg are determimed. Adsorption heat of an olefin increases with a growing length of its carbonic chain. The number of adsorbed olefin molecules grows with an increase in the MoO 3 concentration, while initial adsorption heats decrease. The number of adsorbed olefins is proportional to mean rate of molybdenum reduction in catalysts. Adsorption heats of oxygen on the surface of the catalysts with preliminarily adsorbed olefins are determined. It is shown that adsorption of oxygen and olefins proceeeds both on the same and on different centres of the surface. Mechanisms of surface interactions are discussed

  5. Synthesis of thermoplastic poly(ester-olefin elastomers

    Directory of Open Access Journals (Sweden)

    Tanasijević Branka

    2004-01-01

    Full Text Available A series of thermoplastic poly(ester-olefin elastomers, based on poly(ethylene-stat-butylene, HO-PEB-OH, as the soft segment and poly (butylene terephthalate, PBT, as the hard segment, were synthesized by a catalyzed transesterification reaction in solution. The incorporation of soft hydrogenated poly(butadiene segments into the copolyester backbone was accomplished by the polycondensation of α, ω-dihydroxyl telechelic HO-PEB-OH, (PEB Mn = 3092 g/mol with 1,4-butanediol (BD and dimethyl terephthalate (DMT in the presence of a 50 wt-% high boiling solvent i.e., 1,2,4-trichlorobenzene. The molar ratio of the starting comonomers was selected to result in a constant hard to soft weight ratio of 60:40. The synthesis was optimized in terms of both the concentration of catalyst, tetra-n-butyl-titanate (Ti(OBu4, and stabilizer, N,N'-diphenyl-p-phenylenediamine (DPPD, as well as the reaction time. It was found that the optimal catalyst concentration (Ti(OBu4 for the synthesis of these thermoplastic elastomers was 1.0 mmol/mol ester and the optimal DPPD concentration was 1.0 wt-%. The extent of the reaction was followed by measuring the inherent viscosity of the reaction mixture. The effectiveness of the incorporation of the soft segments into the copolymer chains was proved by Soxhlet extraction with chloroform. The molecular structures, composition and the size of the synthesized poly(ester-butylenes were verified by 1H NMR spectroscopy, viscometry of dilute solutions and the complex dynamic melt viscosity. The thermal properties of poly(ester-olefins were investigated by differential scanning calorimetry (DSC. The degree of crystallinity was also determined by DSC. The thermal and thermo-oxidative stability were investigated by thermogravimetric analysis (TGA. The rheological properties of poly(ester-olefins were investigated by dynamic mechanical spectroscopy in the melt and solid state.

  6. Transmissive Olefination Route to Putative “Morinol I” Lignans

    Science.gov (United States)

    Yao, Lihua; Pitta, Bhaskar; Ravikumar, P. C.; Purzycki, Matthew; Fleming, Fraser F.

    2012-01-01

    A series of morinol-type lignans were rapidly assembled using a Grignard-based transmissive olefination. In combination with palladium-catalyzed arylations, the strategy provides stereoselective access to (7Z, 7′E), (7E, 7′E), (7E, 7′Z) morinol diastereomers and the (7Z, 8′E) and (7E, 8′E) conjugated analogs. Critical for the E/Z-stereoselectivity is a new, general method for converting alkenenitriles to alkenemethanols that circumvents the enal E/Z isomerization commonly encountered during conventional i-Bu2AlH reduction. PMID:22432777

  7. Radiation chemical addition of dimethylformamide to α-olefins

    International Nuclear Information System (INIS)

    Dederichs, B.; Saus, A.; Lennertz, A.M.

    1977-10-01

    With n-hexene-1, n-octene-1 and n-decene-1 the radiation-initiated addition of demethyl formamide to α-olefins is described for the fist time. N,N-dimethyl alkane carbonic acid amides and N-methyl-N-alkyl formamides are formed in a ratio of about 50:50. The addition reaction is investigated in depencence of a solvent, of the ratio of the reaction, temperature, reaction time and dose rate. Mechanistic considerations are performed by radiolysis experiments of dimethyl formamide. (orig.) [de

  8. Iron based superconductors and related compounds synthesized by solid state metathesis and high temperature reactions

    International Nuclear Information System (INIS)

    Frankovsky, Rainer

    2013-01-01

    The results of this thesis can be divided into three major topics, which can also be seen as different approaches of solid state chemistry to reveal interesting features of known and unknown compounds and to develop alternative synthesis routes. Firstly, known compounds with related structural motifs to the superconducting iron-arsenides were investigated regarding their structural and physical properties. In case of La 3 Pd 4 Ge 4 the influence of Fe doping on the properties was studied, whereas in the series ZrMAs (M=Ti,V) the physical properties have not yet been reported at all and were investigated for the first time. Secondly, an alternative synthesis route has been developed for the synthesis of superconducting LaFeAsO 1-x F x . This solid state metathesis reaction distinctly increased the quality of the samples compared to conventionally prepared products. Furthermore, the reaction pathway was investigated and clarified, which helps to understand the processes during high temperature solid state metathesis reactions in general. Thirdly, this alternative synthesis route was expanded to other systems and new compounds like co-substituted LaFe 1-x Mn x AsO 1-y F y were prepared and thoroughly investigated. This led to a complex study of the interplay of magnetism, electronic and structural conditions and the occurrence of superconducting properties. The investigation and understanding of such complex coherences will probably be decisive for the further understanding of the superconducting mechanism in iron based superconductors.

  9. Dynamic behaviour of tantalum hydride supported on silica or MCM-41 in the metathesis of alkanes

    KAUST Repository

    Soignier, Sophie

    2014-01-01

    The metathesis of ethane and propane catalysed by tantalum hydride supported on silica or MCM-41 was studied under static and dynamic conditions. During the reaction, the rate decreased over time, indicating deactivation of the catalyst. The evolution of the catalytic system and surface species over time was monitored by various physico-chemical methods: FTIR, 13C NMR spectroscopy, elemental analysis and chemical reactivity. A carbonaceous deposit composed of unsaturated hydrocarbyl species was observed by 13C NMR. This deposit was responsible for poisoning of the catalyst. The deactivation of the catalyst proved more severe at higher temperatures and under static rather than dynamic conditions. A partial regeneration of the catalyst could be achieved during a series of repeated runs. Mechanistically, the deconvolution of the products\\' distribution over time indicated the occurrence of hydrogenolysis in the early stages of the reaction, while pure metathesis dominated later on. The hydrogen was supplied by the dehydrogenation of hydrocarbyl surface species involved in the deactivation process. © 2014 The Royal Society of Chemistry.

  10. Developing new methods for the mono-end functionalization of living ring opening metathesis polymers.

    Science.gov (United States)

    Kilbinger, Andreas F M

    2012-01-01

    In this article we present a review of our recent results in one area of research we are involved in. All research efforts in our group focus on functional polymers and new ways of gaining higher levels of control with regard to the placement of functional groups within these polymers. Here, the living ring opening metathesis polymerization (ROMP) will be reviewed for which end-functionalization methods had been rare until very recently. Polymers carrying particular functional groups only at the chain-ends are, however, very interesting for a variety of industrial and academic applications. Polymeric surfactants and polymer-protein conjugates are two examples for the former and polymer-β-sheet-peptide conjugates one example for the latter. The functionalization of macroscopic or nanoscopic surfaces often relies on mono-end functional polymers. Complex macromolecular architectures are often constructed from macromolecules carrying exactly one functional group at their chain- end. The ring opening metathesis polymerization is particularly interesting in this context as it is one of the most functional group tolerant polymerization methods known. Additionally, high molecular weight polymers are readily accessible with this technique, a feature that living radical polymerizations often struggle to achieve. Finding new ways of functionalizing the polymer chain-end of ROMP polymers has therefore been a task long overdue. Here, we present our contribution to this area of research.

  11. Dynamic behaviour of tantalum hydride supported on silica or MCM-41 in the metathesis of alkanes

    KAUST Repository

    Soignier, Sophie; Saggio, Guillaume; Taoufik, Mostafa; Basset, Jean-Marie; Thivolle-Cazat, Jean

    2014-01-01

    The metathesis of ethane and propane catalysed by tantalum hydride supported on silica or MCM-41 was studied under static and dynamic conditions. During the reaction, the rate decreased over time, indicating deactivation of the catalyst. The evolution of the catalytic system and surface species over time was monitored by various physico-chemical methods: FTIR, 13C NMR spectroscopy, elemental analysis and chemical reactivity. A carbonaceous deposit composed of unsaturated hydrocarbyl species was observed by 13C NMR. This deposit was responsible for poisoning of the catalyst. The deactivation of the catalyst proved more severe at higher temperatures and under static rather than dynamic conditions. A partial regeneration of the catalyst could be achieved during a series of repeated runs. Mechanistically, the deconvolution of the products' distribution over time indicated the occurrence of hydrogenolysis in the early stages of the reaction, while pure metathesis dominated later on. The hydrogen was supplied by the dehydrogenation of hydrocarbyl surface species involved in the deactivation process. © 2014 The Royal Society of Chemistry.

  12. Separation of Olefin/Paraffin Mixtures with Carrier Facilitated Membrane Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Merkel, T.C.; Blanc, R.; Zeid, J.; Suwarlim, A.; Firat, B.; Wijmans, H.; Asaro, M. (SRI); Greene, M.(Lummus)

    2007-03-12

    This document describes the results of a DOE funded joint effort of Membrane Technology and Research Inc. (MTR), SRI International (SRI), and ABB Lummus (ABB) to develop facilitated transport membranes for olefin/paraffin separations. Currently, olefin/paraffin separation is done by distillation—an extremely energy-intensive process because of the low relative volatilities of olefins and paraffins. If facilitated transport membranes could be successfully commercialized, the potential energy savings achievable with this membrane technology are estimated to be 48 trillion Btu per year by the year 2020. We discovered in this work that silver salt-based facilitated transport membranes are not stable even in the presence of ideal olefin/paraffin mixtures. This decline in membrane performance appears to be caused by a previously unrecognized phenomenon that we have named olefin conditioning. As the name implies, this mechanism of performance degradation becomes operative once a membrane starts permeating olefins. This project is the first study to identify olefin conditioning as a significant factor impacting the performance of facilitated olefin transport membranes. To date, we have not identified an effective strategy to mitigate the impact of olefin conditioning. other than running at low temperatures or with low olefin feed pressures. In our opinion, this issue must be addressed before further development of facilitated olefin transport membranes can proceed. In addition to olefin conditioning, traditional carrier poisoning challenges must also be overcome. Light, hydrogen, hydrogen sulfide, and acetylene exposure adversely affect membrane performance through unwanted reaction with silver ions. Harsh poisoning tests with these species showed useful membrane lifetimes of only one week. These tests demonstrate a need to improve the stability of the olefin complexing agent to develop membranes with lifetimes satisfactory for commercial application. A successful effort

  13. Chirality in adsorption on solid surfaces.

    Science.gov (United States)

    Zaera, Francisco

    2017-12-07

    In the present review we survey the main advances made in recent years on the understanding of chemical chirality at solid surfaces. Chirality is an important topic, made particularly relevant by the homochiral nature of the biochemistry of life on Earth, and many chiral chemical reactions involve solid surfaces. Here we start our discussion with a description of surface chirality and of the different ways that chirality can be bestowed on solid surfaces. We then expand on the studies carried out to date to understand the adsorption of chiral compounds at a molecular level. We summarize the work published on the adsorption of pure enantiomers, of enantiomeric mixtures, and of prochiral molecules on chiral and achiral model surfaces, especially on well-defined metal single crystals but also on other flat substrates such as highly ordered pyrolytic graphite. Several phenomena are identified, including surface reconstruction and chiral imprinting upon adsorption of chiral agents, and the enhancement or suppression of enantioselectivity seen in some cases upon adsorption of enantiomixtures of chiral compounds. The possibility of enhancing the enantiopurity of adsorbed layers upon the addition of chiral seeds and the so-called "sergeants and soldiers" phenomenon are presented. Examples are provided where the chiral behavior has been associated with either thermodynamic or kinetic driving forces. Two main approaches to the creation of enantioselective surface sites are discussed, namely, via the formation of supramolecular chiral ensembles made out of small chiral adsorbates, and by adsorption of more complex chiral molecules capable of providing suitable chiral environments for reactants by themselves, via the formation of individual adsorbate:modifier adducts on the surface. Finally, a discussion is offered on the additional effects generated by the presence of the liquid phase often required in practical applications such as enantioselective crystallization, chiral

  14. Cyclic phosphopeptides for interference with Grb2 SH2 domain signal transduction prepared by ring-closing metathesis and phosphorylation

    NARCIS (Netherlands)

    Dekker, Frank J; de Mol, Nico J; Fischer, Marcel J E; Kemmink, Johan; Liskamp, Rob M J; Dekker, Frank

    2003-01-01

    Cyclic phosphopeptides were prepared using ring-closing metathesis followed by phosphorylation. These cyclic phosphopeptides were designed to interact with the SH2 domain of Grb2, which is a signal transduction protein of importance as a target for antiproliferative drug development. Binding of

  15. Design and synthesis of fused polycycles via Diels-Alder reaction and ring-rearrangement metathesis as key steps.

    Science.gov (United States)

    Kotha, Sambasivarao; Ravikumar, Ongolu

    2015-01-01

    Atom efficient processes such as the Diels-Alder reaction (DA) and the ring-rearrangement metathesis (RRM) have been used to design new polycycles. In this regard, ruthenium alkylidene catalysts are effective in realizing the RRM of bis-norbornene derivatives prepared by DA reaction and Grignard addition. Here, fused polycycles are assembled which are difficult to produce by conventional synthetic routes.

  16. Metathesis of 2-pentene over Mo and W supported mesoporous molecular sieves MCM-41 and SBA-15

    Czech Academy of Sciences Publication Activity Database

    Ibrahim, M. A.; Akhtar, M. N.; Čejka, Jiří; Montanari, E.; Balcar, Hynek; Kubů, Martin; Al-Khattaf, S. S.

    2017-01-01

    Roč. 53, SEP 2017 (2017), s. 119-126 ISSN 1226-086X R&D Projects: GA ČR(CZ) GAP106/12/0189 Institutional support: RVO:61388955 Keywords : metathesis * MCM-41 * SBA-15 Subject RIV: CF - Physical ; Theoretical Chemistry OBOR OECD: Physical chemistry Impact factor: 4.421, year: 2016

  17. Synthesis of Heterocycles through a Ruthenium‐Catalyzed Tandem Ring‐Closing Metathesis/Isomerization/N‐Acyliminium Cyclization Sequence

    DEFF Research Database (Denmark)

    Ascic, Erhad; Jensen, Jakob Feldthusen; Nielsen, Thomas Eiland

    2011-01-01

    Tandem bicycle: In the title reaction double bonds created during ring-closing metathesis isomerize to generate reactive iminium intermediates that undergo intramolecular cyclization reactions with tethered heteroatom and carbon nucleophiles. In this way, a series of biologically interesting hete...... heterocyclic compounds can be made, including a known precursor for the total synthesis of the antiparasitic natural product harmicine....

  18. Asymmetric Synthesis of Apratoxin E.

    Science.gov (United States)

    Mao, Zhuo-Ya; Si, Chang-Mei; Liu, Yi-Wen; Dong, Han-Qing; Wei, Bang-Guo; Lin, Guo-Qiang

    2016-10-21

    An efficient method for asymmetric synthesis of apratoxin E 2 is described in this report. The chiral lactone 8, recycled from the degradation of saponin glycosides, was utilized to prepare the non-peptide fragment 6. In addition to this "from nature to nature" strategy, olefin cross-metathesis (CM) was applied as an alternative approach for the formation of the double bond. Moreover, pentafluorophenyl diphenylphosphinate was found to be an efficient condensation reagent for the macrocyclization.

  19. Chiral memory via chiral amplification and selective depolymerization of porphyrin aggregates

    NARCIS (Netherlands)

    Helmich, F.A.; Lee, C.C.; Schenning, A.P.H.J.; Meijer, E.W.

    2010-01-01

    Chiral memory at the supramolecular level is obtained via a new approach using chiral Zn porphrins and achiral Cu porphyrins. In a "sergeant-and-soldiers" experiment, the Zn "sergeant" transfers its own chirality to Cu "soldiers" and, after chiral amplification, the "sergeant" is removed from the

  20. Hydroxycarbonylation of olefins and alcohols in ionic liquids

    Energy Technology Data Exchange (ETDEWEB)

    Lapidus, A.L.; Eliseev, O.L.; Bondarenko, T.N.; Stepin, N.N. [Russian Academy of Sciences, Moscow (Russian Federation). N.D. Zelinsky Institute of Organic Chemistry

    2006-07-01

    Palladium-catalysed hydroxycarbonylation of olefins and alcohols proceeds in ionic liquid media. Terminal and internal olefins, cyclohexene, styrene, methanol, ethanol, n-butanol, cyclohexanol, benzyl alcohol and 1-phenylethanol were tested as substrates for the reaction. A number of molten salts were applied as a reaction medium and tetrabutylammonium bromide (m.p. 103 C) seemed to be the best. Carbon monoxide pressure of 2 MPa and reaction temperature of 110 C are suitable conditions to furnish the reaction in 2 hours in the presence of palladium acetate as a precursor. Triphenylphosphine added as a ligand reduces reaction rate. The critical role of counter anion in molten salt was also recognised. Yield of acids decreased in the order: Br{sup -} > Cl{sup -} > BF{sub 4} {approx}PF{sub 6}{sup -}. A two-route reaction scheme is proposed to explain the regularities of styrene and 1-phenylethanol hydroxycarbonylation. The catalytic system can be used repeatedly by simple extraction of products with diethyl ether. Nine cycles were carried out without loss of activity. (orig.)

  1. Gas phase reactions of nitrogen oxides with olefins

    Energy Technology Data Exchange (ETDEWEB)

    Altshuller, A P; Cohen, I

    1961-01-01

    The nature of the condensation products formed in the gas phase reactions of nitrogen dioxide and nitric oxide with pentene-1, 2-methylbutene-2, and 2-methylbutadiene-1,3 was investigated. The reactants were combined at partial pressures in the range of 0.1 to 2.5 mm with the total pressure at one atmosphere. The products were determined by infrared and ultraviolet spectroscopy and colorimetry. The condensates included primary and secondary nitro compounds and alkyl nitrates. Strong hydroxyl and single bond carbon to oxygen stretching vibrations indicate the presence of either nitroalcohols or simple aliphatic alcohols formed through oxidation reactions. Carbonyl stretching frequencies observable in some of the reactions support the conclusion that a portion of the reactants disappear by oxidation rather than by nitration processes. The available results do not indicate the presence of appreciable amounts of tert.-nitro compounds, conjugated nitro-olefins, or gem-dinitro-alkanes. The reactivities of the olefins with the nitrogen oxides are in the decreasing order: 2-methyl-butadiene-1,3, 2-methylbutene-2, pentene-1. 20 references.

  2. How much life is left in your olefin unit

    International Nuclear Information System (INIS)

    Baas, J.; Warner, R.

    1992-01-01

    Highly attractive economics in the olefin industry has justified increasing capacity via plant expansion and using aging olefin units beyond expected limitations. If these existing units are to operate well beyond their design life, what type of analysis and information is necessary to make this decision? What technologies or methods should be used for continued safe and controlled operation of these not so new units. This paper reports that the plant's mechanical integrity is the focal point of this analysis and decision-making method. Plant life expectancy study (PLES) looks at an operating plant's mechanical integrity from several vantage points. Four basic principles, such as plant history, process upsets and operating records, assessment of plant fires, and how to conduct records, assessment of plant fires, and how to conduct inspection and testing, provide the basis of how well a plant has been operated and maintained. Furthermore, the analysis includes a critical component inventory. These items address additional potential-failure causes, such as creep, fatigue, toughness, corrosion, erosion and carburization/oxidation

  3. Effects of chirality and surface stresses on the bending and buckling of chiral nanowires

    International Nuclear Information System (INIS)

    Wang, Jian-Shan; Shimada, Takahiro; Kitamura, Takayuki; Wang, Gang-Feng

    2014-01-01

    Due to their superior optical, elastic and electrical properties, chiral nanowires have many applications as sensors, probes, and building blocks of nanoelectromechanical systems. In this paper, we develop a refined Euler–Bernoulli beam model for chiral nanowires with surface effects and material chirality incorporated. This refined model is employed to investigate the bending and buckling of chiral nanowires. It is found that surface effects and material chirality significantly affect the elastic behaviour of chiral nanowires. This study is helpful not only for understanding the size-dependent behaviour of chiral nanowires, but also for characterizing their mechanical properties. (paper)

  4. Chiral Thirring–Wess model

    Energy Technology Data Exchange (ETDEWEB)

    Rahaman, Anisur, E-mail: anisur.rahman@saha.ac.in

    2015-10-15

    The vector type of interaction of the Thirring–Wess model was replaced by the chiral type and a new model was presented which was termed as chiral Thirring–Wess model in Rahaman (2015). The model was studied there with a Faddeevian class of regularization. Few ambiguity parameters were allowed there with the apprehension that unitarity might be threatened like the chiral generation of the Schwinger model. In the present work it has been shown that no counter term containing the regularization ambiguity is needed for this model to be physically sensible. So the chiral Thirring–Wess model is studied here without the presence of any ambiguity parameter and it has been found that the model not only remains exactly solvable but also does not lose the unitarity like the chiral generation of the Schwinger model. The phase space structure and the theoretical spectrum of this new model have been determined in the present scenario. The theoretical spectrum is found to contain a massive boson with ambiguity free mass and a massless boson.

  5. Chiral Thirring–Wess model

    International Nuclear Information System (INIS)

    Rahaman, Anisur

    2015-01-01

    The vector type of interaction of the Thirring–Wess model was replaced by the chiral type and a new model was presented which was termed as chiral Thirring–Wess model in Rahaman (2015). The model was studied there with a Faddeevian class of regularization. Few ambiguity parameters were allowed there with the apprehension that unitarity might be threatened like the chiral generation of the Schwinger model. In the present work it has been shown that no counter term containing the regularization ambiguity is needed for this model to be physically sensible. So the chiral Thirring–Wess model is studied here without the presence of any ambiguity parameter and it has been found that the model not only remains exactly solvable but also does not lose the unitarity like the chiral generation of the Schwinger model. The phase space structure and the theoretical spectrum of this new model have been determined in the present scenario. The theoretical spectrum is found to contain a massive boson with ambiguity free mass and a massless boson

  6. What's wrong with anomalous chiral gauge theory?

    International Nuclear Information System (INIS)

    Kieu, T.D.

    1994-05-01

    It is argued on general ground and demonstrated in the particular example of the Chiral Schwinger Model that there is nothing wrong with apparently anomalous chiral gauge theory. If quantised correctly, there should be no gauge anomaly and chiral gauge theory should be renormalisable and unitary, even in higher dimensions and with non-Abelian gauge groups. Furthermore, it is claimed that mass terms for gauge bosons and chiral fermions can be generated without spoiling the gauge invariance. 19 refs

  7. Chirality: a relational geometric-physical property.

    Science.gov (United States)

    Gerlach, Hans

    2013-11-01

    The definition of the term chirality by Lord Kelvin in 1893 and 1904 is analyzed by taking crystallography at that time into account. This shows clearly that chirality is a relational geometric-physical property, i.e., two relations between isometric objects are possible: homochiral or heterochiral. In scientific articles the relational term chirality is often mistaken for the two valued measure for the individual (absolute) sense of chirality, an arbitrary attributive term. © 2013 Wiley Periodicals, Inc.

  8. Extreme chirality in Swiss roll metamaterials

    International Nuclear Information System (INIS)

    Demetriadou, A; Pendry, J B

    2009-01-01

    The chiral Swiss roll metamaterial is a resonant, magnetic medium that exhibits a negative refractive band for one-wave polarization. Its unique structure facilitates huge chiral effects: a plane polarized wave propagating through this system can change its polarization by 90 deg. in less than a wavelength. Such chirality is at least 100 times greater than previous structures have achieved. In this paper, we discuss this extreme chiral behaviour with both numerical and analytical results.

  9. Techno-economic analysis and comparison of coal based olefins processes

    International Nuclear Information System (INIS)

    Xiang, Dong; Yang, Siyu; Qian, Yu

    2016-01-01

    Highlights: • The coal based Fischer–Tropsch-to-olefins (CFTO) process is proposed and analyzed. • The CFTO suffers from lower energy efficiency and serious CO 2 emissions. • Approaches for improving techno-economic performance of the CFTO are obtained. - Abstract: Traditional olefins production is heavily dependent on oil. In the background of the scarcity of oil and richness of coal in China, olefins production from coal has been attracting more attention of the chemical process industry. The first coal based methanol-to-olefins (CMTO) plant has been commercialized in China. For shorter process route and lower capital cost, Fischer–Fropsch has been put forward in the last few years. The coal based Fischer–Tropsch-to-olefins (CFTO) process is designed in this paper and then its techno-economic and environmental performance was detailed studied in this paper, in comparison with the CMTO. Results show that at the present olefins selectivity, the CFTO suffers from relative lower energy efficiency and higher CO 2 emissions. In economic aspect, the capital investment and product cost of the CFTO are roughly equivalent to that of the CMTO. Although the conversion route of the CFTO is shorter, its techno-economic performance is still inferior to that of the CMTO. It is also found that increase of olefins selectivity by cracking oil or decrease of CO 2 selectivity by improving catalyst could significantly improve the performance of the CFTO.

  10. Chiral dynamics of baryons in the perturbative chiral quark model

    Energy Technology Data Exchange (ETDEWEB)

    Pumsa-ard, K.

    2006-07-01

    In this work we develop and apply variants of a perturbative chiral quark model (PCQM) to the study of baryonic properties dominantly in the low-energy region. In a first step we consider a noncovariant form of the PCQM, where confinement is modelled by a static, effective potential and chiral corrections are treated to second order, in line with similar chiral quark models. We apply the PCQM to the study of the electromagnetic form factors of the baryon octet. We focus in particular on the low-energy observables such as the magnetic moments, the charge and magnetic radii. In addition, the electromagnetic N-delta transition is also studied in the framework of the PCQM. In the chiral loop calculations we consider a quark propagator, which is restricted to the quark ground state, or in hadronic language to nucleon and delta intermediate states, for simplicity. We furthermore include the low-lying excited states to the quark propagator. In particular, the charge radius of the neutron and the transverse helicity amplitudes of the N-delta transition are considerably improved by this additional effect. In a next step we develop a manifestly Lorentz covariant version of the PCQM, where in addition higher order chiral corrections are included. The full chiral quark Lagrangian is motivated by and in analogy to the one of Chiral Perturbation Theory (ChPT). This Lagrangian contains a set of low energy constants (LECs), which are parameters encoding short distance effects and heavy degrees of freedom. We evaluate the chiral Lagrangian to order O(p{sup 4}) and to one loop to generate the dressing of the bare quark operators by pseudoscalar mesons. In addition we include the vector meson degrees of freedom in our study. Projection of the dressed quark operators on the baryonic level serves to calculate the relevant matrix elements. In a first application of this scheme, we resort to a parameterization of the valence quark form factors in the electromagnetic sector. Constraints

  11. Chiral measurements with the Fixed-Point Dirac operator and construction of chiral currents

    International Nuclear Information System (INIS)

    Hasenfratz, P.; Hauswirth, S.; Holland, K.; Joerg, T.; Niedermayer, F.

    2002-01-01

    In this preliminary study, we examine the chiral properties of the parametrized Fixed-Point Dirac operator D FP , see how to improve its chirality via the Overlap construction, measure the renormalized quark condensate Σ-circumflex and the topological susceptibility χ t , and investigate local chirality of near zero modes of the Dirac operator. We also give a general construction of chiral currents and densities for chiral lattice actions

  12. Pion polarizability in a chiral quark model

    International Nuclear Information System (INIS)

    Volkov, M.K.; Ehbert, D.

    1980-01-01

    The pion polarizability is calculated in a chiral meson-quark model at the one-loop level. The results are in complete agreement with earlier ones obtained within a chiral meson-baryon theory. A critical discussion of a recent paper by Lanta and Tarrach is given. The results of the paper give evidence to the nonlinear chiral Lagrangian favour

  13. Quenched Chiral Perturbation Theory to one loop

    NARCIS (Netherlands)

    Colangelo, G.; Pallante, E.

    The divergences of the generating functional of quenched Chiral Perturbation theory (qCHPT) to one loop are computed in closed form. We show how the quenched chiral logarithms can be reabsorbed in the renormalization of the B0 parameter of the leading order Lagrangian. Finally, we do the chiral

  14. Variational approach to chiral quark models

    Energy Technology Data Exchange (ETDEWEB)

    Futami, Yasuhiko; Odajima, Yasuhiko; Suzuki, Akira

    1987-03-01

    A variational approach is applied to a chiral quark model to test the validity of the perturbative treatment of the pion-quark interaction based on the chiral symmetry principle. It is indispensably related to the chiral symmetry breaking radius if the pion-quark interaction can be regarded as a perturbation.

  15. A variational approach to chiral quark models

    International Nuclear Information System (INIS)

    Futami, Yasuhiko; Odajima, Yasuhiko; Suzuki, Akira.

    1987-01-01

    A variational approach is applied to a chiral quark model to test the validity of the perturbative treatment of the pion-quark interaction based on the chiral symmetry principle. It is indispensably related to the chiral symmetry breaking radius if the pion-quark interaction can be regarded as a perturbation. (author)

  16. Chirality plays important roles in radiopharmaceuticals

    International Nuclear Information System (INIS)

    Shen Yumei

    2006-01-01

    The paper introduces the basic concept of chirality, target specific selectivity and their relationship in radiopharmaceuticals. If the ligands labeled by radionuclides have chiral center, the enantiomers must be separated, or the target specific selectivity will not be good. Chirality is one of the most important factors which must be considered in the study of the structure-activity relationship of radiopharmaceuticals. (authors)

  17. Pions and the chiral bag

    International Nuclear Information System (INIS)

    Rho, M.

    1982-01-01

    As an aid to discussing the structure of nucleons and nuclei conceptual framework, heuristic arguments are presented which indicate that a hadron can be considered as a bag consisting of two different phases. The chiral structure of the phase outside the bag is discussed in terms of effective field theories and it is shown to what extent experiments in nuclei can constrain the structure of such theories. Results thus obtained are then combined to set up a set of equations for the bag structure of u and d hadrons, incorporating asymptotic freedom in the phase inside of the bag confinement of quarks and gluons by boundary conditions and spontaneously broken chiral symmetry in the outside. This set of equations which represent a chirally invariant generalization of the M.I.T. bag model is then solved. (U.K.)

  18. Fusion rules of chiral algebras

    International Nuclear Information System (INIS)

    Gaberdiel, M.

    1994-01-01

    Recently we showed that for the case of the WZW and the minimal models fusion can be understood as a certain ring-like tensor product of the symmetry algebra. In this paper we generalize this analysis to arbitrary chiral algebras. We define the tensor product of conformal field theory in the general case and prove that it is associative and symmetric up to equivalence. We also determine explicitly the action of the chiral algebra on this tensor product. In the second part of the paper we demonstrate that this framework provides a powerful tool for calculating restrictions for the fusion rules of chiral algebras. We exhibit this for the case of the W 3 algebra and the N=1 and N=2 NS superconformal algebras. (orig.)

  19. Physics of chiral symmetry breaking

    International Nuclear Information System (INIS)

    Shuryak, E.V.

    1991-01-01

    This subsection of the 'Modeling QCD' Workshop has included five talks. E. Shuryak spoke on 'Recent Progress in Understanding Chiral Symmetry Breaking'; below it is split into two parts: (i) a mini-review of the field and (ii) a brief presentation of the status of the theory of interacting instantons. The next sections correspond to the following talks: (iii) K. Goeke et al., 'Chiral Restoration and Medium Corrections to Nucleon in the NJL Model'; (iv) M. Takizawa and K. Kubodera, 'Study of Meson Properties and Quark Condensates in the NJL Model with Instanton Effects'; (v) G. Klein and A. G. Williams, 'Dynamical Chiral Symmetry Breaking in Dual QCD'; and (vi) R. D. Ball, 'Skyrmions and Baryons.' (orig.)

  20. Chirality and gravitational parity violation.

    Science.gov (United States)

    Bargueño, Pedro

    2015-06-01

    In this review, parity-violating gravitational potentials are presented as possible sources of both true and false chirality. In particular, whereas phenomenological long-range spin-dependent gravitational potentials contain both truly and falsely chiral terms, it is shown that there are models that extend general relativity including also coupling of fermionic degrees of freedom to gravity in the presence of torsion, which give place to short-range truly chiral interactions similar to that usually considered in molecular physics. Physical mechanisms which give place to gravitational parity violation together with the expected size of the effects and their experimental constraints are discussed. Finally, the possible role of parity-violating gravity in the origin of homochirality and a road map for future research works in quantum chemistry is presented. © 2015 Wiley Periodicals, Inc.

  1. Chiral interaction and biomolecular evolution

    International Nuclear Information System (INIS)

    Gilat, G.

    1992-01-01

    Recent developments in the concept of chiral interaction open now new options and dynamical possibilities for biomolecules which have so far been overlooked. A few of these possibilities are mentioned, such as the control mechanism of enzymatic activity and the role played by non-ergodicity in evolutionary processes. It is shown that chiral interaction, being a surface phenomenon, does not obey Barron's symmetry constraints, which are suitable for force fields present in bulk interactions. In particular, the situation at the ocean-air surface in the prebiotic era is described, as well as the possible role played by chiral interaction in conjunction with the terrestrial magnetic field normal to the ocean surface, which could have lead to a process of deracernization at the ocean-air interface. (author)

  2. In vivo and in vitro olefin cyclopropanation catalyzed by heme enzymes

    Science.gov (United States)

    Coelho, Pedro S; Brustad, Eric M; Arnold, Frances H; Wang, Zhan; Lewis, Jared C

    2015-03-31

    The present invention provides methods for catalyzing the conversion of an olefin to any compound containing one or more cyclopropane functional groups using heme enzymes. In certain aspects, the present invention provides a method for producing a cyclopropanation product comprising providing an olefinic substrate, a diazo reagent, and a heme enzyme; and admixing the components in a reaction for a time sufficient to produce a cyclopropanation product. In other aspects, the present invention provides heme enzymes including variants and fragments thereof that are capable of carrying out in vivo and in vitro olefin cyclopropanation reactions. Expression vectors and host cells expressing the heme enzymes are also provided by the present invention.

  3. Atmosphere-Controlled Chemoselectivity: Rhodium-Catalyzed Alkylation and Olefination of Alkylnitriles with Alcohols.

    Science.gov (United States)

    Li, Junjun; Liu, Yuxuan; Tang, Weijun; Xue, Dong; Li, Chaoqun; Xiao, Jianliang; Wang, Chao

    2017-10-17

    The chemoselective alkylation and olefination of alkylnitriles with alcohols have been developed by simply controlling the reaction atmosphere. A binuclear rhodium complex catalyzes the alkylation reaction under argon through a hydrogen-borrowing pathway and the olefination reaction under oxygen through aerobic dehydrogenation. Broad substrate scope is demonstrated, permitting the synthesis of some important organic building blocks. Mechanistic studies suggest that the alkylation product may be formed through conjugate reduction of an alkene intermediate by a rhodium hydride, whereas the formation of olefin product may be due to the oxidation of the rhodium hydride complex with molecular oxygen. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Ligand-Enabled γ-C(sp(3))-H Olefination of Amines: En Route to Pyrrolidines.

    Science.gov (United States)

    Jiang, Heng; He, Jian; Liu, Tao; Yu, Jin-Quan

    2016-02-17

    Pd(II)-catalyzed olefination of γ-C(sp(3))-H bonds of triflyl (Tf) and 4-nitrobenzenesulfonyl (Ns) protected amines is achieved. Subsequent aza-Wacker oxidative cyclization or conjugate addition of the olefinated intermediates provides a variety of C-2 alkylated pyrrolidines. Three pyridine- and quinoline-based ligands are developed to match different classes of amine substrates, demonstrating a rare example of ligand-enabled C(sp(3))-H olefination reactions. The use of Ns protecting group to direct C(sp(3))-H activation of alkyl amines is also a significant step toward practical C-H functionalizations of alkyl amines.

  5. Stereoselective synthesis of hydroxy stilbenoids and styrenes by atom-efficient olefination with thiophthalides.

    Science.gov (United States)

    Mitra, Prithiba; Shome, Brateen; De, Saroj Ranjan; Sarkar, Anindya; Mal, Dipakranjan

    2012-04-14

    The synthesis of stilbenoids and styryl carboxylic acids is accomplished with high E-stereoselectivity by olefination of aldehydes with thiophthalides under basic conditions. The olefination is highly atom-efficient as it only loses elemental sulfur during the reaction. This olefination, in conjunction with retro Kolbe-Schmitt reaction, allows facile synthesis of E-hydroxystilbenoids with minimal employment of protecting groups. This study also discloses two important findings: formation of i) 4-methylsulfanyl isocoumarins and ii) an 2-arylindenone. This journal is © The Royal Society of Chemistry 2012

  6. Primary Alcohols from Terminal Olefins: Formal Anti-Markovnikov Hydration via Triple Relay Catalysis

    KAUST Repository

    Dong, G.

    2011-09-15

    Alcohol synthesis is critical to the chemical and pharmaceutical industries. The addition of water across olefins to form primary alcohols (anti-Markovnikov olefin hydration) would be a broadly useful reaction but has largely proven elusive; an indirect hydroboration/oxidation sequence requiring stoichiometric borane and oxidant is currently the most practical methodology. Here, we report a more direct approach with the use of a triple relay catalysis system that couples palladium-catalyzed oxidation, acid-catalyzed hydrolysis, and ruthenium-catalyzed reduction cycles. Aryl-substituted terminal olefins are converted to primary alcohols by net reaction with water in good yield and excellent regioselectivity.

  7. Chiral soliton models for baryons

    International Nuclear Information System (INIS)

    Weigel, H.

    2008-01-01

    This concise research monograph introduces and reviews the concept of chiral soliton models for baryons. In these models, baryons emerge as (topological) defects of the chiral field. The many applications shed light on a number of baryon properties, ranging from static properties via nucleon resonances and deep inelastic scattering to even heavy ion collisions. As far as possible, the theoretical investigations are confronted with experiment. Conceived to bridge the gap between advanced graduate textbooks and the research literature, this volume also features a number of appendices to help nonspecialist readers to follow in more detail some of the calculations in the main text. (orig.)

  8. Surface defects and chiral algebras

    Energy Technology Data Exchange (ETDEWEB)

    Córdova, Clay [School of Natural Sciences, Institute for Advanced Study,1 Einstein Dr, Princeton, NJ 08540 (United States); Gaiotto, Davide [Perimeter Institute for Theoretical Physics,31 Caroline St N, Waterloo, ON N2L 2Y5 (Canada); Shao, Shu-Heng [School of Natural Sciences, Institute for Advanced Study,1 Einstein Dr, Princeton, NJ 08540 (United States)

    2017-05-26

    We investigate superconformal surface defects in four-dimensional N=2 superconformal theories. Each such defect gives rise to a module of the associated chiral algebra and the surface defect Schur index is the character of this module. Various natural chiral algebra operations such as Drinfeld-Sokolov reduction and spectral flow can be interpreted as constructions involving four-dimensional surface defects. We compute the index of these defects in the free hypermultiplet theory and Argyres-Douglas theories, using both infrared techniques involving BPS states, as well as renormalization group flows onto Higgs branches. In each case we find perfect agreement with the predicted characters.

  9. Asymmetric Synthesis via Chiral Aziridines

    DEFF Research Database (Denmark)

    Tanner, David Ackland; Harden, Adrian; Wyatt, Paul

    1996-01-01

    A series of chiral bis(aziridines) has been synthesised and evaluated as chelating ligands for a variety of asymmetric transformations mediated by metals [Os (dihydroxylation), Pd (allylic alkylation) Cu (cyclopropanation and aziridination, Li (1,2-addition of organolithiums to imines)]. In the b......A series of chiral bis(aziridines) has been synthesised and evaluated as chelating ligands for a variety of asymmetric transformations mediated by metals [Os (dihydroxylation), Pd (allylic alkylation) Cu (cyclopropanation and aziridination, Li (1,2-addition of organolithiums to imines...

  10. Chiral symmetry on the lattice

    International Nuclear Information System (INIS)

    Creutz, M.

    1994-11-01

    The author reviews some of the difficulties associated with chiral symmetry in the context of a lattice regulator. The author discusses the structure of Wilson Fermions when the hopping parameter is in the vicinity of its critical value. Here one flavor contrasts sharply with the case of more, where a residual chiral symmetry survives anomalies. The author briefly discusses the surface mode approach, the use of mirror Fermions to cancel anomalies, and finally speculates on the problems with lattice versions of the standard model

  11. Probing Stereoselectivity in Ring-Opening Metathesis Polymerization Mediated by Cyclometalated Ruthenium-Based Catalysts: A Combined Experimental and Computational Study

    OpenAIRE

    Rosebrugh, L. E.; Ahmed, T. S.; Marx, V. M.; Hartung, J.; Liu, P.; López, J. G.; Houk, K. N.; Grubbs, R. H.

    2016-01-01

    The microstructures of polymers produced by ring-opening metathesis polymerization (ROMP) with cyclometalated Ru-carbene metathesis catalysts were investigated. A strong bias for a cis,syndiotactic microstructure with minimal head-to-tail bias was observed. In instances where trans errors were introduced, it was determined that these regions were also syndiotactic. Furthermore, hypothetical reaction intermediates and transition structures were analyzed computationally. Combined experimental a...

  12. Olefin polymerization from single site catalysts confined within porous media

    Science.gov (United States)

    Kasi, Rajeswari M.

    Single Site Catalysts (SSCs) have been utilized for olefin polymerization. Altering the metal-ligand architecture in the SSCs, polyolefin properties can be enhanced in a rational manner. This influence of the ligands in the SSC on the property of polyolefins prepared can be referred to as the primary ligand influence. Extending this understanding and subsequent control of the metal-ligand framework to the interaction of SSCs within organic and inorganic supports is vital for the synthesis of polyolefins with tailored properties. The motivation behind this thesis was to explore the support influence on the reactivity of the SSC tethered to a support matrix during ethylene homo and copolymerization. In order to address this question of the support influence on the final polyolefin properties, synthetic routes to covalently bind SSCs on different matrices have been explored. Two distinct supported SSCs have been used to prepare branched polyethylenes. Branched polyethylenes can be prepared by either copolymerization (ethylene and alpha-olefin) or oligomerization/copolymerization processes (ethylene and in situ generated alpha-olefin). Synthetic routes to prepare precursor catalysts to Constrained Geometry Catalysts (CGCs) by silyl elimination chemistry have been developed (Chapter 2). Efficient synthetic protocols to assemble CGCs on aminomethylpolysytrene matrices (Chapter 3) and amine-functionalized mesoporous silica (Chapter 4) are also reported. These supported catalysts, with appropriate cocatalysts have been used to prepare ethylene homo and copolymers, the polymer thermal properties and microstructures were analyzed by various analytical techniques. Branched polyethylenes (LLDPE) can be prepared by copolymerization chemistry. It has been observed is that the influence of the support is seen in the production of lower crystalline forms of high density polyethylene (HDPE, 20--50% crystalline), while homogeneous polymerization of analogous soluble CGCs afford HDPE

  13. Reversible optical transcription of supramolecular chirality into molecular chirality

    NARCIS (Netherlands)

    Jong, Jaap J.D. de; Lucas, Linda N.; Kellogg, Richard M.; Esch, Jan H. van; Feringa, Bernard

    2004-01-01

    In nature, key molecular processes such as communication, replication, and enzyme catalysis all rely on a delicate balance between molecular and supramolecular chirality. Here we report the design, synthesis, and operation of a reversible, photoresponsive, self-assembling molecular system in which

  14. Oscillation damping of chiral string loops

    International Nuclear Information System (INIS)

    Babichev, Eugeny; Dokuchaev, Vyacheslav

    2002-01-01

    Chiral cosmic string loops tend to the stationary (vorton) configuration due to energy loss into gravitational and electromagnetic radiation. We describe the asymptotic behavior of near stationary chiral loops and their fading to vortons. General limits on the gravitational and electromagnetic energy losses by near stationary chiral loops are found. For these loops we estimate the oscillation damping time. We present solvable examples of gravitational radiation energy loss by some chiral loop configurations. The analytical dependence of string energy with time is found in the case of the chiral ring with small amplitude radial oscillations

  15. Production of jet fuel range paraffins by low temperature polymerization of gaseous light olefins using ionic liquid

    International Nuclear Information System (INIS)

    Jiang, Peiwen; Wu, Xiaoping; Zhu, Lijuan; Jin, Feng; Liu, Junxu; Xia, Tongyan; Wang, Tiejun; Li, Quanxin

    2016-01-01

    Graphical abstract: A novel catalytic transformation of light olefins into jet fuel range iso-paraffins by the low-temperature olefin polymerizations under atmospheric conditions. - Highlights: • A novel transformation of light olefins to jet fuel range paraffins was demonstrated. • The synthetic fuels can be produced by atmospheric olefin polymerizations. • C 8 –C 15 iso-paraffins from light olefins was achieved with a selectivity of 80.6%. - Abstract: This work demonstrated a novel catalytic transformation of gaseous olefins into jet fuel range iso-paraffins by the low-temperature olefin polymerizations under atmospheric conditions. The production of the desired C 8 –C 15 iso-paraffins with the selectivity of 80.6 C mol% was achieved by the room-temperature polymerizations of gaseous light olefins using the [BMIM] Al 2 Cl 7 ionic liquid. The influences of the reaction conditions on the olefinic polymerizations were investigated in detail. The properties of hydrocarbons in the synthetic fuels were determined by the GC–MS analyses combined with 1 H NMR, and 13 C NMR analyses. The formation of C 8 –C 15 hydrocarbons from gaseous light olefins was illustrated by the identified products and the functional groups. This transformation potentially provides a useful avenue for the production of the most important components of iso-paraffins required in jet fuels.

  16. Low-temperature synthesis of actinide tetraborides by solid-state metathesis reactions

    Science.gov (United States)

    Lupinetti, Anthony J [Los Alamos, NM; Garcia, Eduardo [Los Alamos, NM; Abney, Kent D [Los Alamos, NM

    2004-12-14

    The synthesis of actinide tetraborides including uranium tetraboride (UB.sub.4), plutonium tetraboride (PuB.sub.4) and thorium tetraboride (ThB.sub.4) by a solid-state metathesis reaction are demonstrated. The present method significantly lowers the temperature required to .ltoreq.850.degree. C. As an example, when UCl.sub.4 is reacted with an excess of MgB.sub.2, at 850.degree. C., crystalline UB.sub.4 is formed. Powder X-ray diffraction and ICP-AES data support the reduction of UCl.sub.3 as the initial step in the reaction. The UB.sub.4 product is purified by washing water and drying.

  17. Chiral Recognition and Separation by Chirality-Enriched Metal-Organic Frameworks.

    Science.gov (United States)

    Das, Saikat; Xu, Shixian; Ben, Teng; Qiu, Shilun

    2018-05-16

    Endowed with chiral channels and pores, chiral metal-organic frameworks (MOFs) are highly useful; however, their synthesis remains a challenge given that most chiral building blocks are expensive. Although MOFs with induced chirality have been reported to avoid this shortcoming, no study providing evidence for the ee value of such MOFs has yet been reported. We herein describe the first study on the efficiency of chiral induction in MOFs using inexpensive achiral building blocks and fully recoverable chiral dopants to control the handedness of racemic MOFs. This method yielded chirality-enriched MOFs with accessible pores. The ability of the materials to form host-guest complexes was probed with enantiomers of varying size and coordination and in solvents with varying polarity. Furthermore, mixed-matrix membranes (MMMs) composed of chirality-enriched MOF particles dispersed in a polymer matrix demonstrated a new route for chiral separation. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Chiral Induction with Chiral Conformational Switches in the Limit of Low "Sergeants to Soldiers" Ratio

    DEFF Research Database (Denmark)

    Nuermaimaiti, Ajiguli; Bombis, Christian; Knudsen, Martin Markvard

    2014-01-01

    Molecular-level insights into chiral adsorption phenomena are highly relevant within the fields of asymmetric heterogeneous catalysis or chiral separation and may contribute to understand the origins of homochirality in nature. Here, we investigate chiral induction by the "sergeants and soldiers......" mechanism for an oligo(phenylene ethynylene) based chiral conformational switch by coadsorbing it with an intrinsically chiral seed on Au(111). Through statistical analysis of scanning tunneling microscopy (STM) data we demonstrate successful chiral induction with a very low concentration of seeding...... molecules down to 3%. The microscopic mechanism for the observed chiral induction is suggested to involve nucleation of the intrinsically chiral seeds, allowing for effective transfer and amplification of chirality to large numbers of soldier target molecules....

  19. Chirality effect in disordered graphene ribbon junctions

    International Nuclear Information System (INIS)

    Long Wen

    2012-01-01

    We investigate the influence of edge chirality on the electronic transport in clean or disordered graphene ribbon junctions. By using the tight-binding model and the Landauer-Büttiker formalism, the junction conductance is obtained. In the clean sample, the zero-magnetic-field junction conductance is strongly chirality-dependent in both unipolar and bipolar ribbons, whereas the high-magnetic-field conductance is either chirality-independent in the unipolar or chirality-dependent in the bipolar ribbon. Furthermore, we study the disordered sample in the presence of magnetic field and find that the junction conductance is always chirality-insensitive for both unipolar and bipolar ribbons with adequate disorders. In addition, the disorder-induced conductance plateaus can exist in all chiral bipolar ribbons provided the disorder strength is moderate. These results suggest that we can neglect the effect of edge chirality in fabricating electronic devices based on the magnetotransport in a disordered graphene ribbon. (paper)

  20. No chiral truncation of quantum log gravity?

    Science.gov (United States)

    Andrade, Tomás; Marolf, Donald

    2010-03-01

    At the classical level, chiral gravity may be constructed as a consistent truncation of a larger theory called log gravity by requiring that left-moving charges vanish. In turn, log gravity is the limit of topologically massive gravity (TMG) at a special value of the coupling (the chiral point). We study the situation at the level of linearized quantum fields, focussing on a unitary quantization. While the TMG Hilbert space is continuous at the chiral point, the left-moving Virasoro generators become ill-defined and cannot be used to define a chiral truncation. In a sense, the left-moving asymptotic symmetries are spontaneously broken at the chiral point. In contrast, in a non-unitary quantization of TMG, both the Hilbert space and charges are continuous at the chiral point and define a unitary theory of chiral gravity at the linearized level.

  1. Radiation-chemical alkylation of olefines with adamantane

    International Nuclear Information System (INIS)

    Podkhalyuzin, A.T.; Vikulin, V.V.; Morozov, V.A.; Nazarova, M.P.; Vereshchinskii, I.V.

    1977-01-01

    Radiation-chemical alkylation of C 2 to C 4 olefines with adamantane was studied in gas phase at temperatures 270 to 430 0 C. The main reaction product is monoalkyladamantane. The reaction proceeds by a free radical chain mechanism. The effective activation energy is of the order of 8 to 10 kcal/mole. Thermal alkylation was carried out for comparison and the contribution of the thermal component to the radiation-thermal process was estimated. Liquid phase alkylation of hexafluoropropylene with adamantane was studied in the presence of solvents. Under various conditions mono- and di-substituted adamantanes are produced containing fluorine in end groups. These compounds were converted to corresponding fluoroalkenyladamantanes by dehydrofluorination. The kinetic parameters were calculated and physical-chemical data concerning some of the resulting products were determined. (author)

  2. New unit for sulfuric acid alkylation of isobutane by olefins

    Energy Technology Data Exchange (ETDEWEB)

    Khadzhiev, S.N.; Baiburskii, V.L.; Deineko, P.S.; Gruzdev, A.S.; Tagavov, I.T.

    1987-01-01

    The authors describe and illustrate a sulfuric acid alkylation unit with a horizontal contact. As a result of the use of this design solution, the isobutane/olefin ratio is 10/1 in comparison with 4/1 to 5/1 in the other types of units, namely vertical reactors and cascade tank reactors. The unit was designed to process the butane-butylene cut (BBC) and part of the propane-propylene cut (PPC) from the G-43-107 cat cracker. The unit design includes provisions for controlled caustic washing of the feed and dehydration in an electric field. The authors present the basic data obtained in the three months of unit operation after startup, in comparison with the operating indexes of a sulfuric acid alkylation unit.

  3. The FCC process as a producer of light olefins

    International Nuclear Information System (INIS)

    Yung, K.Y.; Yanik, S.; O'Connor, P.; Pouwels, C.

    1992-01-01

    To reduce emissions from the gasoline engine, aromatics content and vapor pressure of the motor gasoline pool will be reduced and a minimum amount of oxygen will be mandated. This reformulation will limit the application of high octane components like benzene, toluene and butanes and will require the use of oxygenates. To compensate for the loss in octane, the use of alkylate and, of course also oxygenates will grow. The Fluid Catalytic Cracking Unit is, as producer of (olefinic) propanes, butanes and pentanes, an important feedstock producer for alkylate and oxygenate producing process. Hence, process adjustments and FCC catalyst formations to increase the yield of above desirable light products are of prime importance and will be dealt with in this paper

  4. Rhodium-Catalyzed Enantioselective Cyclopropanation of Olefins with N-Sulfonyl 1,2,3-Triazoles

    Science.gov (United States)

    Chuprakov, Stepan; Kwok, Sen Wai; Zhang, Li; Lercher, Lukas; Fokin, Valery V.

    2009-01-01

    N-Sulfonyl 1,2,3-triazoles readily form rhodium(II) azavinyl carbenes, which react with olefins to produce cyclopropanes with excellent diastereo- and enantioselectivity and in high yield. PMID:19928917

  5. Gum forming olefinic precursors in motor gasoline: a model compound study

    Energy Technology Data Exchange (ETDEWEB)

    Nagpal, J.M.; Joshi, G.C.; Singh, J.; Rastogi, S.N. (Indian Institute of Petroleum, Dehradun (India))

    1994-01-01

    The source of the cracked components in motor gasoline are generally (Fluid Catalytic Cracking) FCC and thermal cracking naphthas incorporated in the gasoline pool. The FCC olefins are predominant in isostructures, while thermal cracking naphthas obtained from visbreaking and coking operations contain substantial amounts of cyclic structures. The contribution of various olefinic structures present in these naphthas are likely to vary. The gum forming tendencies of different types of olefinic structures have been studied by taking model compounds in a known sample matrix through potential gum measurements under accelerated test conditions. Peroxide number values have also been determined on aged sample. Cyclic and dicyclic structures have been found to contribute maximum, towards gum formation tendencies. Branching generally increases the gum formation. However, position of branching plays an important role besides the double bond. Synergistic effects of dienes with straight chain and branched olefins have also been studied. 11 refs., 10 figs., 2 tabs.

  6. Esterase-sensitive sulfur dioxide prodrugs inspired by modified Julia olefination.

    Science.gov (United States)

    Wang, Wenyi; Wang, Binghe

    2017-09-12

    Sulfur dioxide (SO 2 ) is an endogenously produced gaseous molecule, and is emerging as a potential gasotransmitter. Herein, we describe the first series of esterase-sensitive prodrugs inspired by modified Julia olefination as SO 2 donors.

  7. Palladium-catalyzed aryl C-H olefination with unactivated, aliphatic alkenes.

    Science.gov (United States)

    Deb, Arghya; Bag, Sukdev; Kancherla, Rajesh; Maiti, Debabrata

    2014-10-01

    Palladium-catalyzed coupling between aryl halides and alkenes (Mizoroki-Heck reaction) is one of the most popular reactions for synthesizing complex organic molecules. The limited availability, problematic synthesis, and higher cost of aryl halide precursors (or their equivalents) have encouraged exploration of direct olefination of aryl carbon-hydrogen (C-H) bonds (Fujiwara-Moritani reaction). Despite significant progress, the restricted substrate scope, in particular noncompliance of unactivated aliphatic olefins, has discouraged the use of this greener alternative. Overcoming this serious limitation, we report here a palladium-catalyzed chelation-assisted ortho C-H bond olefination of phenylacetic acid derivatives with unactivated, aliphatic alkenes in good to excellent yields with high regio- and stereoselectivities. The versatility of this operationally simple method has been demonstrated through drug diversification and sequential C-H olefination for synthesizing divinylbenzene derivatives.

  8. Nickel-catalysed retro-hydroamidocarbonylation of aliphatic amides to olefins

    Science.gov (United States)

    Hu, Jiefeng; Wang, Minyan; Pu, Xinghui; Shi, Zhuangzhi

    2017-05-01

    Amide and olefins are important synthetic intermediates with complementary reactivity which play a key role in the construction of natural products, pharmaceuticals and manmade materials. Converting the normally highly stable aliphatic amides into olefins directly is a challenging task. Here we show that a Ni/NHC-catalytic system has been established for decarbonylative elimination of aliphatic amides to generate various olefins via C-N and C-C bond cleavage. This study not only overcomes the acyl C-N bond activation in aliphatic amides, but also encompasses distinct chemical advances on a new type of elimination reaction called retro-hydroamidocarbonylation. This transformation shows good functional group compatibility and can serve as a powerful synthetic tool for late-stage olefination of amide groups in complex compounds.

  9. Extreme ultraviolet (EUV) degradation of poly(olefin sulfone)s: Towards applications as EUV photoresists

    International Nuclear Information System (INIS)

    Lawrie, Kirsten; Blakey, Idriss; Blinco, James; Gronheid, Roel; Jack, Kevin; Pollentier, Ivan; Leeson, Michael J.; Younkin, Todd R.; Whittaker, Andrew K.

    2011-01-01

    Poly(olefin sulfone)s, formed by the reaction of sulfur dioxide (SO 2 ) and an olefin, are known to be highly susceptible to degradation by radiation and thus have been identified as candidate materials for chain scission-based extreme ultraviolet lithography (EUVL) resist materials. In order to investigate this further, the synthesis and characterisation of two poly(olefin sulfone)s namely poly(1-pentene sulfone) (PPS) and poly(2-methyl-1-pentene sulfone) (PMPS), was achieved and the two materials were evaluated for possible chain scission EUVL resist applications. It was found that both materials possess high sensitivities to EUV photons; however; the rates of outgassing were extremely high. The only observed degradation products were found to be SO 2 and the respective olefin suggesting that depolymerisation takes place under irradiation in a vacuum environment. In addition to depolymerisation, a concurrent conversion of SO 2 moieties to a sulfide phase was observed using XPS.

  10. Structure and dynamics of olefin radical cation aggregates. Time-resolved fluorescence detected magnetic resonance

    International Nuclear Information System (INIS)

    Desrosiers, M.F.; Trifunac, A.D.

    1986-01-01

    The time-resolved EPR spectra and thus the structure and dynamics of transient hydrocarbon radical cations are obtained by the pulse radiolysis-fluorescence detected magnetic resonance (FDMR) technique. Here the authors report the observation of short-lived radical cations from olefins. FDMR-EPR spectra of radical cations from tetramethylethylene and cyclohexadiene are illustrated. The olefin radical cations, FDMR spectra are concentration-dependent, since dimerization with neutral molecules takes place at higher (>10 -2 M) olefin concentration. Rate constants for the dimerization reaction are derived and the effect of solvent viscosity on aggregate formation is demonstrated. By monitoring the further reactions of dimer cations the authors have obtained EPR evidence for previously unobserved higher-order (multimer) radical cation aggregates of olefins. 16 references, 5 figures

  11. Capturing of the monoterpene olefin limonene produced in Saccharomyces cerevisiae.

    Science.gov (United States)

    Jongedijk, Esmer; Cankar, Katarina; Ranzijn, Jorn; van der Krol, Sander; Bouwmeester, Harro; Beekwilder, Jules

    2015-01-01

    Monoterpene olefins such as limonene are plant compounds with applications as flavouring and fragrance agents, as solvents and potentially also in polymer and fuel chemistry. We engineered baker's yeast Saccharomyces cerevisiae to express a (-)-limonene synthase from Perilla frutescens and a (+)-limonene synthase from Citrus limon. Both proteins were expressed either with their native plastid targeting signal or in a truncated form in which the plastidial sorting signal was removed. The yeast host strain for expression was AE9 K197G, which expresses a mutant Erg20 enzyme. This enzyme catalyses the formation of geranyl diphosphate, which is the precursor for monoterpenes. Several methods were tested to capture limonene produced by the yeast. Extraction from the culture medium by pentane, or by the addition of CaCl2 followed by solid-phase micro-extraction, did not lead to detectable limonene, indicating that limonene is rapidly lost from the culture medium. Volatile terpenes such as limonene may also be trapped in a dodecane phase added to the medium during fermentation. This method resulted in recovery of 0.028 mg/l (+)-limonene and 0.060 mg/l (-)-limonene in strains using the truncated Citrus and Perilla synthases, respectively. Trapping the headspace during culture of the limonene synthase-expressing strains resulted in higher titres, at 0.12 mg/l (+)-limonene and 0.49 mg/l (-)-limonene. These results show that the volatile properties of the olefins produced require specific methods for efficient recovery of these molecules from biotechnological production systems. Copyright © 2014 John Wiley & Sons, Ltd.

  12. A New Twist on Chirality

    NARCIS (Netherlands)

    Feringa, Bernard

    2001-01-01

    One of the great mysteries in science is the homochirality (single handedness) of the essential molecules of life. Natural sugars are almost exclusively right-handed; natural amino acids are almost exclusively left-handed. Current life forms could not exist without the uniform chirality of these

  13. Instantons and chiral symmetry breaking

    International Nuclear Information System (INIS)

    Carneiro, C.E.I.; McDougall, N.A.

    1984-01-01

    A detailed investigation of chiral symmetry breaking due to instanton dynamics is carried out, within the framework of the dilute gas approximation, for quarks in both the fundamental and adjoint representations of SU(2). The momentum dependence of the dynamical mass is found to be very similar in each representation. (orig.)

  14. Instantons and chiral symmetry breaking

    Energy Technology Data Exchange (ETDEWEB)

    Carneiro, C.E.I.; McDougall, N.A. (Oxford Univ. (UK). Dept. of Theoretical Physics)

    1984-10-22

    A detailed investigation of chiral symmetry breaking due to instanton dynamics is carried out, within the framework of the dilute gas approximation, for quarks in both the fundamental and adjoint representations of SU(2). The momentum dependence of the dynamical mass is found to be very similar in each representation.

  15. Status of chiral perturbation theory

    International Nuclear Information System (INIS)

    Ecker, G.

    1996-10-01

    A survey is made of semileptonic and nonleptonic kaon decays in the framework of chiral perturbation theory. The emphasis is on what has been done rather than how it was done. The theoretical predictions are compared with available experimental results. (author)

  16. Principles of chiral perturbation theory

    International Nuclear Information System (INIS)

    Leutwyler, H.

    1995-01-01

    An elementary discussion of the main concepts used in chiral perturbation theory is given in textbooks and a more detailed picture of the applications may be obtained from the reviews. Concerning the foundations of the method, the literature is comparatively scarce. So, I will concentrate on the basic concepts and explain why the method works. (author)

  17. Chiral symmetry in perturbative QCD

    International Nuclear Information System (INIS)

    Trueman, T.L.

    1979-04-01

    The chiral symmetry of quantum chromodynamics with massless quarks is unbroken in perturbation theory. Dimensional regularization is used. The ratio of the vector and axial vector renormalization constante is shown to be independent of the renormalization mass. The general results are explicitly verified to fourth order in g, the QCD coupling constant

  18. Descendants of the Chiral Anomaly

    OpenAIRE

    Jackiw, R.

    2000-01-01

    Chern-Simons terms are well-known descendants of chiral anomalies, when the latter are presented as total derivatives. Here I explain that also Chern-Simons terms, when defined on a 3-manifold, may be expressed as total derivatives.

  19. Pd(II/HPMoV-Catalyzed Direct Oxidative Coupling Reaction of Benzenes with Olefins

    Directory of Open Access Journals (Sweden)

    Yasutaka Ishii

    2010-03-01

    Full Text Available The direct aerobic coupling reaction of arenes with olefins was successfully achieved by the use of Pd(OAc2/molybdovanadophosphoric acid (HPMoV as a key catalyst under 1 atm of dioxygen. This catalytic system could be extended to the coupling reaction of various substituted benzenes with olefins such as acrylates, aclrolein, and ethylene through the direct aromatic C-H bond activation.

  20. An Improved Protocol for the Aldehyde Olefination Reaction Using (bmim ( as Reaction Medium

    Directory of Open Access Journals (Sweden)

    Vivek Srivastava

    2013-01-01

    Full Text Available [Ru(CODCl2]/CuCl2·2H2O/LiCl catalytic system works efficiently in ionic liquid media for aldehyde olefination reaction. It offers good yield and selectivity with the added advantage of 5 times recyclability for [Ru(CODCl2] /CuCl2·2H2O/LiCl catalytic system. We also successfully reduced the reaction time from 12 hours to 9 hours for the aldehyde olefination reaction.

  1. Stereoselective Wittig Olefination as a Macrocyclization Tool. Synthesis of Large Carbazolophanes.

    Science.gov (United States)

    Myśliwiec, Damian; Lis, Tadeusz; Gregoliński, Janusz; Stępień, Marcin

    2015-06-19

    Z-Selective Wittig olefination was applied to the synthesis of large carbazolophanes containing up to eight heteroaromatic subunits. A number of strategies were devised and tested, showing that cyclooligomerization yields can be significantly improved by using one-component schemes involving heterobifunctional reactants. [4]- and [6]Carbazolophanes were characterized in the solid state, revealing compact, highly folded structures. Electronic and steric effects of substitution and chain length on the Wittig olefination rates and Z-selectivities were explored theoretically using DFT calculations.

  2. Ligand-Promoted C(sp(3) )-H Olefination en Route to Multi-functionalized Pyrazoles.

    Science.gov (United States)

    Yang, Weibo; Ye, Shengqing; Schmidt, Yvonne; Stamos, Dean; Yu, Jin-Quan

    2016-05-17

    A Pd-catalyzed/N-heterocycle-directed C(sp(3) )-H olefination has been developed. The monoprotected amino acid ligand (MPAA) is found to significantly promote Pd-catalyzed C(sp(3) )-H olefination for the first time. Cu(OAc)2 instead of Ag(+) salts are used as the terminal oxidant. This reaction provides a useful method for the synthesis of alkylated pyrazoles. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. On the nature of the olefination reaction involving ditungsten hexaalkoxides and aldehydes or ketones

    Energy Technology Data Exchange (ETDEWEB)

    Chisholm, M.H.; Huffman, J.C.; Lucas, E.A.; Sousa, A.; Streib, W.E. [Indiana Univ., Bloomington, IN (United States)

    1992-03-25

    Reductive coupling of aldehydes and ketones to olefins under the action of ditungsten hexaalkoxides was investigated. In these reactions, reductive cleavage of the aldehyde or ketone carbonyl is followed by formation of the olefinic C-C bond and breaking of the carbonyl C-O bond of the second aldehyde or ketone. Observations concerning the initial C-O bond cleavage and subsequent C-C bond formation are presented. 10 refs., 4 figs.

  4. Palladium catalyzed selective distal C-H olefination of biaryl systems.

    Science.gov (United States)

    Maity, Soham; Hoque, Ehtasimul; Dhawa, Uttam; Maiti, Debabrata

    2016-11-29

    Palladium catalyzed selective distal C-H activation with nitrile based templates has been of significant research interest in recent times. In this report, we disclose the distal C-H olefination of biphenyl systems with high regio- and stereo-selectivity and useful synthetic yields. The utility of this method has been demonstrated through its wide olefin scope, its operation at the gram scale and the easy removal/recovery of the directing group.

  5. Nuclear chiral dynamics and thermodynamics

    Science.gov (United States)

    Holt, Jeremy W.; Kaiser, Norbert; Weise, Wolfram

    2013-11-01

    This presentation reviews an approach to nuclear many-body systems based on the spontaneously broken chiral symmetry of low-energy QCD. In the low-energy limit, for energies and momenta small compared to a characteristic symmetry breaking scale of order 1 GeV, QCD is realized as an effective field theory of Goldstone bosons (pions) coupled to heavy fermionic sources (nucleons). Nuclear forces at long and intermediate distance scales result from a systematic hierarchy of one- and two-pion exchange processes in combination with Pauli blocking effects in the nuclear medium. Short distance dynamics, not resolved at the wavelengths corresponding to typical nuclear Fermi momenta, are introduced as contact interactions between nucleons. Apart from a set of low-energy constants associated with these contact terms, the parameters of this theory are entirely determined by pion properties and low-energy pion-nucleon scattering observables. This framework (in-medium chiral perturbation theory) can provide a realistic description of both isospin-symmetric nuclear matter and neutron matter, with emphasis on the isospin-dependence determined by the underlying chiral NN interaction. The importance of three-body forces is emphasized, and the role of explicit Δ(1232)-isobar degrees of freedom is investigated in detail. Nuclear chiral thermodynamics is developed and a calculation of the nuclear phase diagram is performed. This includes a successful description of the first-order phase transition from a nuclear Fermi liquid to an interacting Fermi gas and the coexistence of these phases below a critical temperature Tc. Density functional methods for finite nuclei based on this approach are also discussed. Effective interactions, their density dependence and connections to Landau Fermi liquid theory are outlined. Finally, the density and temperature dependences of the chiral (quark) condensate are investigated.

  6. Zeolitic imidazolate frameworks with optimized pore structure for olefin/paraffin-separation

    Energy Technology Data Exchange (ETDEWEB)

    Paula, C.; Boehme, U.; Hartmann, M. [Erlangen-Nuernberg Univ. (Germany). Erlangen Catalysis Resource Center

    2013-11-01

    In the chemical industry, the largest part of energy is spent on separation processes such as the separation of olefin/paraffin mixtures from steam cracker effluents by low-temperature rectification. A suitable alternative to this energy and cost intensive process is separation by selective adsorption with suitable microporous adsorbent. In this work, different ZIFs (Zeolitic Imidazolate Frameworks) have been explored with respect to their separation of olefins and paraffins. The studied materials (e.g. ZIF-8 (SOD-Topology), ZIF-71 (RHO-Topology)) were selected because of their low diameter of the largest pore entrance (0.29 to 4.2 nm) which is close to the kinetic diameter of the C{sub 2} to C{sub 4} olefins and paraffins under study. In contrast to other MOF- or zeolite-based adsorbents, in ZIF-8 and ZIF-71, the paraffin is preferentially adsorbed, which is evident from the single-component adsorption isotherms at different temperature. In the corresponding mixture breakthrough curves, the olefin breaks through first and the alkane even displaces the olefin from the pores. Thus, ZIF-8 and ZIF-71 are interesting candidates for the envisaged paraffin/olefin separation. Whether the observed separation behavior is due to the structural properties of the studied ZIFs or a consequence of peculiar chemical properties is subject to further studies. (orig.) (Published in summary form only)

  7. Olefins-selective asymmetric carbon molecular sieve hollow fiber membranes for hybrid membrane-distillation processes for olefin/paraffin separations

    KAUST Repository

    Xu, Liren

    2012-12-01

    In this paper, the development of asymmetric carbon molecular sieve (CMS) hollow fiber membranes and advanced processes for olefin/paraffin separations based on the CMS membranes are reported. Membrane-based olefin/paraffin separations have been pursued extensively over the past decades. CMS membranes are promising to exceed the performance upper bound of polymer materials and have demonstrated excellent stability for gas separations. Previously, a substructure collapse phenomenon was found in Matrimid ® precursor derived CMS fiber. To overcome the permeance loss due to the increased separation layer thickness, 6FDA-DAM and 6FDA/BPDA-DAM precursors were selected as potential new precursors for carbon membrane formation. Defect-free asymmetric 6FDA-DAM and 6FDA/BPDA-DAM hollow fibers were successfully fabricated from a dry-jet/wet-quench spinning process. Polymer rigidity, glass-rubber transition and asymmetric morphology were correlated. CMS hollow fiber membranes produced from 6FDA-polymer precursors showed significant improvement in permeance for ethylene/ethane and propylene/propane separations. Further studies revealed that the CMS membranes are olefins-selective, which means the membranes are able to effectively separate olefins (ethylene and propylene) from paraffins (ethane and propane). This unique feature of CMS materials enables advanced hybrid membrane-distillation process designs. By using the olefins-selective membranes, these new processes may provide advantages over previously proposed retrofitting concepts. Further applications of the membranes are explored for hydrocarbons processes. Significant energy savings and even reduced footprint may be achieved in olefins production units. © 2012 Elsevier B.V.

  8. Sequential meta-C-H olefination of synthetically versatile benzyl silanes: effective synthesis of meta-olefinated toluene, benzaldehyde and benzyl alcohols.

    Science.gov (United States)

    Patra, Tuhin; Watile, Rahul; Agasti, Soumitra; Naveen, Togati; Maiti, Debabrata

    2016-02-04

    Tremendous progress has been made towards ortho-selective C-H functionalization in the last three decades. However, the activation of distal C-H bonds and their functionalization has remained fairly underdeveloped. Herein, we report sequential meta-C-H functionalization by performing selective mono-olefination and bis-olefination with late stage modification of the C-Si as well as Si-O bonds. Temporary silyl connection was found to be advantageous due to its easy installation, easy removal and wide synthetic diversification.

  9. Catalytic allylic oxidation of internal alkenes to a multifunctional chiral building block

    Science.gov (United States)

    Bayeh, Liela; Le, Phong Q.; Tambar, Uttam K.

    2017-07-01

    The stereoselective oxidation of hydrocarbons is one of the most notable advances in synthetic chemistry over the past fifty years. Inspired by nature, enantioselective dihydroxylations, epoxidations and other oxidations of unsaturated hydrocarbons have been developed. More recently, the catalytic enantioselective allylic carbon-hydrogen oxidation of alkenes has streamlined the production of pharmaceuticals, natural products, fine chemicals and other functional materials. Allylic functionalization provides a direct path to chiral building blocks with a newly formed stereocentre from petrochemical feedstocks while preserving the olefin functionality as a handle for further chemical elaboration. Various metal-based catalysts have been discovered for the enantioselective allylic carbon-hydrogen oxidation of simple alkenes with cyclic or terminal double bonds. However, a general and selective allylic oxidation using the more common internal alkenes remains elusive. Here we report the enantioselective, regioselective and E/Z-selective allylic oxidation of unactivated internal alkenes via a catalytic hetero-ene reaction with a chalcogen-based oxidant. Our method enables non-symmetric internal alkenes to be selectively converted into allylic functionalized products with high stereoselectivity and regioselectivity. Stereospecific transformations of the resulting multifunctional chiral building blocks highlight the potential for rapidly converting internal alkenes into a broad range of enantioenriched structures that can be used in the synthesis of complex target molecules.

  10. Ene-yne Cross-Metathesis for the Preparation of 2,3-Diaryl-1,3-dienes

    Directory of Open Access Journals (Sweden)

    Meriem K. Abderrezak

    2017-11-01

    Full Text Available Ene-yne cross-metathesis from alkynes and ethylene is a useful method to produce substituted conjugated butadiene derivatives. If this method has been used with aliphatic alkynes, it has however never been used starting from diarylacetylenes as internal alkynes. We show that the ene-yne cross-metathesis catalyzed by the second generation Hoveyda ruthenium catalyst provides the 2,3-diarylbuta-1,3-dienes under 3 atm of ethylene at 100 °C. The scope and limitations of the reaction have been evaluated starting from unsymmetrical functionalized diarylacetylene derivatives hence leading to unsymmetrical 2,3-diarylbuta-1,3-dienes in a straightforward and environmentally acceptable manner.

  11. Bifunctional nanocrystalline MgO for chiral epoxy ketones via Claisen-Schmidt condensation-asymmetric epoxidation reactions.

    Science.gov (United States)

    Choudary, Boyapati M; Kantam, Mannepalli L; Ranganath, Kalluri V S; Mahendar, Koosam; Sreedhar, Bojja

    2004-03-24

    Design and development of a truly nanobifunctional heterogeneous catalyst for the Claisen-Schmidt condensation (CSC) of benzaldehydes with acetophenones to yield chalcones quantitatively followed by asymmetric epoxidation (AE) to afford chiral epoxy ketones with moderate to good yields and impressive ee's is described. The nanomagnesium oxide (aerogel prepared) NAP-MgO was found to be superior over the NA-MgO and CM-MgO in terms of activity and enantioselectivity as applicable in these reactions. An elegant strategy for heterogenization of homogeneous catalysts is presented here to evolve single-site chiral catalysts for AE by a successful transfer of molecular chemistry to surface metal-organic chemistry with the retention of activity, selectivity/enantioselectivity. Brønsted hydroxyls are established as sole contributors for the epoxidation reaction, while they add on to the CSC, which is largely driven by Lewis basic O2-sites. Strong hydrogen-bond interactions between the surface -OH on MgO and -OH groups of diethyl tartrate are found inducing enantioselectivity in the AE reaction. Thus, the nanocrystalline NAP-MgO with its defined shape, size, and accessible OH groups allows the chemisorption of TBHP, DET, and olefin on its surface to accomplish single-site chiral catalysts to provide optimum ee's in AE reactions.

  12. Timoshenko beam model for chiral materials

    Science.gov (United States)

    Ma, T. Y.; Wang, Y. N.; Yuan, L.; Wang, J. S.; Qin, Q. H.

    2018-06-01

    Natural and artificial chiral materials such as deoxyribonucleic acid (DNA), chromatin fibers, flagellar filaments, chiral nanotubes, and chiral lattice materials widely exist. Due to the chirality of intricately helical or twisted microstructures, such materials hold great promise for use in diverse applications in smart sensors and actuators, force probes in biomedical engineering, structural elements for absorption of microwaves and elastic waves, etc. In this paper, a Timoshenko beam model for chiral materials is developed based on noncentrosymmetric micropolar elasticity theory. The governing equations and boundary conditions for a chiral beam problem are derived using the variational method and Hamilton's principle. The static bending and free vibration problem of a chiral beam are investigated using the proposed model. It is found that chirality can significantly affect the mechanical behavior of beams, making materials more flexible compared with nonchiral counterparts, inducing coupled twisting deformation, relatively larger deflection, and lower natural frequency. This study is helpful not only for understanding the mechanical behavior of chiral materials such as DNA and chromatin fibers and characterizing their mechanical properties, but also for the design of hierarchically structured chiral materials.

  13. Photoexcitation circular dichroism in chiral molecules

    Science.gov (United States)

    Beaulieu, S.; Comby, A.; Descamps, D.; Fabre, B.; Garcia, G. A.; Géneaux, R.; Harvey, A. G.; Légaré, F.; Mašín, Z.; Nahon, L.; Ordonez, A. F.; Petit, S.; Pons, B.; Mairesse, Y.; Smirnova, O.; Blanchet, V.

    2018-05-01

    Chiral effects appear in a wide variety of natural phenomena and are of fundamental importance in science, from particle physics to metamaterials. The standard technique of chiral discrimination—photoabsorption circular dichroism—relies on the magnetic properties of a chiral medium and yields an extremely weak chiral response. Here, we propose and demonstrate an orders of magnitude more sensitive type of circular dichroism in neutral molecules: photoexcitation circular dichroism. This technique does not rely on weak magnetic effects, but takes advantage of the coherent helical motion of bound electrons excited by ultrashort circularly polarized light. It results in an ultrafast chiral response and the efficient excitation of a macroscopic chiral density in an initially isotropic ensemble of randomly oriented chiral molecules. We probe this excitation using linearly polarized laser pulses, without the aid of further chiral interactions. Our time-resolved study of vibronic chiral dynamics opens a way to the efficient initiation, control and monitoring of chiral chemical change in neutral molecules at the level of electrons.

  14. Pharmacophore mapping in the laulimalide series: total synthesis of a vinylogue for a late-stage metathesis diversification strategy.

    Science.gov (United States)

    Wender, Paul A; Hilinski, Michael K; Skaanderup, Philip R; Soldermann, Nicolas G; Mooberry, Susan L

    2006-08-31

    An efficient synthesis of the macrocyclic core of laulimalide with a pendant vinyl group at C20 is described, allowing for late-stage introduction of various side chains through a selective and efficient cross metathesis diversification step. Representative analogues reported herein are the first to contain modifications to only the side chain dihydropyran of laulimalide and des-epoxy laulimalide. This step-economical strategy enables the rapid synthesis of new analogues using alkenes as an inexpensive, abundantly available diversification feedstock.

  15. Design and synthesis of fused polycycles via Diels–Alder reaction and ring-rearrangement metathesis as key steps

    Directory of Open Access Journals (Sweden)

    Sambasivarao Kotha

    2015-07-01

    Full Text Available Atom efficient processes such as the Diels–Alder reaction (DA and the ring-rearrangement metathesis (RRM have been used to design new polycycles. In this regard, ruthenium alkylidene catalysts are effective in realizing the RRM of bis-norbornene derivatives prepared by DA reaction and Grignard addition. Here, fused polycycles are assembled which are difficult to produce by conventional synthetic routes.

  16. Design and synthesis of polycyclic sulfones via Diels-Alder reaction and ring-rearrangement metathesis as key steps.

    Science.gov (United States)

    Kotha, Sambasivarao; Gunta, Rama

    2015-01-01

    Here, we describe a new and simple synthetic strategy to various polycyclic sulfones via Diels-Alder reaction and ring-rearrangement metathesis (RRM) as the key steps. This approach delivers tri- and tetracyclic sulfones with six (n = 1), seven (n = 2) or eight-membered (n = 3) fused-ring systems containing trans-ring junctions unlike the conventional all cis-ring junctions generally obtained during the RRM sequence. Interestingly the starting materials used are simple and commercially available.

  17. Synthesis of a natural product-inspired eight-membered ring lactam library via ring-closing metathesis.

    Science.gov (United States)

    Brown, Neil; Xie, Baohan; Markina, Nataliya; Vandervelde, David; Perchellet, Jean-Pierre H; Perchellet, Elisabeth M; Crow, Kyle R; Buszek, Keith R

    2008-09-01

    We have prepared a novel speculative eight-membered lactam demonstration library based on the skeletal structure of the potent antitumor marine natural product octalactin A. The basic scaffold was readily constructed in a convergent fashion via ring-closing metathesis chemistry from the corresponding diene amides. A cursory examination of the biological properties of the library validates the relevance and significance of these structures.

  18. Inexpensive chirality on the lattice

    International Nuclear Information System (INIS)

    Kamleh, W.; Williams, A.G.; Adams, D.

    2000-01-01

    Full text: Implementing lattice fermions that resemble as closely as possible continuum fermions is one of the main goals of the theoretical physics community. Aside from a lack of infinitely powerful computers, one of the main impediments to this is the Nielsen-Ninomiya No-Go theorem for chirality on the lattice. One of the consequences of this theorem is that exact chiral symmetry and a lack of fermion doublers cannot be simultaneously satisfied for fermions on the lattice. In the commonly used Wilson fermion formulation, chiral symmetry is explicitly sacrificed on the lattice to avoid fermion doubling. Recently, an alternative has come forward, namely, the Ginsparg-Wilson relation and one of its solutions, the Overlap fermion. The Ginsparg-Wilson relation is a statement of lattice-deformed chirality. The Overlap-Dirac operator is a member of the family of solutions of the Ginsparg-Wilson relation. In recent times, Overlap fermions have been of great interest to the community due to their excellent chiral properties. However, they are significantly more expensive to implement than Wilson fermions. This expense is primarily due to the fact that the Overlap implementation requires an evaluation of the sign function for the Wilson-Dirac operator. The sign function is approximated by a high order rational polynomial function, but this approximation is poor close to the origin. The less near-zero modes that the Wilson- Dirac operator possesses, the cheaper the Overlap operator will be to implement. A means of improving the eigenvalue properties of the Wilson-Dirac operator by the addition of a so-called 'Clover' term is put forward. Numerical results are given that demonstrate this improvement. The Nielsen-Ninomiya no-go theorem and chirality on the lattice are reviewed. The general form of solutions of the Ginsparg-Wilson relation are given, and the Overlap solution is discussed. Properties of the Overlap-Dirac operator are given, including locality and analytic

  19. Chiral heat wave and mixing of magnetic, vortical and heat waves in chiral media

    International Nuclear Information System (INIS)

    Chernodub, M.N.

    2016-01-01

    We show that a hot rotating fluid of relativistic chiral fermions possesses a new gapless collective mode associated with coherent propagation of energy density and chiral density waves along the axis of rotation. This mode, which we call the Chiral Heat Wave, emerges due to a mixed gauge-gravitational anomaly. At finite density the Chiral Heat Wave couples to the Chiral Vortical Wave while in the presence of an external magnetic field it mixes with the Chiral Magnetic Wave. The coupling of the Chiral Magnetic and Chiral Vortical Waves is also demonstrated. We find that the coupled waves — which are coherent fluctuations of the vector, axial and energy currents — have generally different velocities compared to the velocities of the individual waves.

  20. Static and dynamical anomalies caused by chiral soliton lattice in molecular-based chiral magnets

    International Nuclear Information System (INIS)

    Kishine, Jun-ichiro; Inoue, Katsuya; Kikuchi, Koichi

    2007-01-01

    Interplay of crystallographic chirality and magnetic chirality has been of great interest in both chemist's and physicist's viewpoints. Crystals belonging to chiral space groups are eligible to stabilize macroscopic chiral magnetic order. This class of magnetic order is described by the chiral XY model, where the transverse magnetic field perpendicular to the chiral axis causes the chiral soliton lattice (CSL) formation. As a clear evidence of the chiral magnetic order, the temperature dependence of the transverse magnetization exhibits sharp cusp just below the mean field ferrimagnetic transition temperature, indicating the formation of the CSL. In addition to the static anomaly, we expect the CSL formation also causes dynamical anomalies such as induction of the spin supercurrent

  1. Chiral supramolecular organization from a sheet-like achiral gel: a study of chiral photoinduction.

    Science.gov (United States)

    Royes, Jorge; Polo, Víctor; Uriel, Santiago; Oriol, Luis; Piñol, Milagros; Tejedor, Rosa M

    2017-05-31

    Chiral photoinduction in a photoresponsive gel based on an achiral 2D architecture with high geometric anisotropy and low roughness has been investigated. Circularly polarized light (CPL) was used as a chiral source and an azobenzene chromophore was employed as a chiral trigger. The chiral photoinduction was studied by evaluating the preferential excitation of enantiomeric conformers of the azobenzene units. Crystallographic data and density functional theory (DFT) calculations show how chirality is transferred to the achiral azomaterials as a result of the combination of chiral photochemistry and supramolecular interactions. This procedure could be applied to predict and estimate chirality transfer from a chiral physical source to a supramolecular organization using different light-responsive units.

  2. Determination of thermodynamic affinities of various polar olefins as hydride, hydrogen atom, and electron acceptors in acetonitrile.

    Science.gov (United States)

    Cao, Ying; Zhang, Song-Chen; Zhang, Min; Shen, Guang-Bin; Zhu, Xiao-Qing

    2013-07-19

    A series of 69 polar olefins with various typical structures (X) were synthesized and the thermodynamic affinities (defined in terms of the molar enthalpy changes or the standard redox potentials in this work) of the polar olefins obtaining hydride anions, hydrogen atoms, and electrons, the thermodynamic affinities of the radical anions of the polar olefins (X(•-)) obtaining protons and hydrogen atoms, and the thermodynamic affinities of the hydrogen adducts of the polar olefins (XH(•)) obtaining electrons in acetonitrile were determined using titration calorimetry and electrochemical methods. The pure C═C π-bond heterolytic and homolytic dissociation energies of the polar olefins (X) in acetonitrile and the pure C═C π-bond homolytic dissociation energies of the radical anions of the polar olefins (X(•-)) in acetonitrile were estimated. The remote substituent effects on the six thermodynamic affinities of the polar olefins and their related reaction intermediates were examined using the Hammett linear free-energy relationships; the results show that the Hammett linear free-energy relationships all hold in the six chemical and electrochemical processes. The information disclosed in this work could not only supply a gap of the chemical thermodynamics of olefins as one class of very important organic unsaturated compounds but also strongly promote the fast development of the chemistry and applications of olefins.

  3. QCD and the chiral critical point

    International Nuclear Information System (INIS)

    Gavin, S.; Gocksch, A.; Pisarski, R.D.

    1994-01-01

    As an extension of QCD, consider a theory with ''2+1'' flavors, where the current quark masses are held in a fixed ratio as the overall scale of the quark masses is varied. At nonzero temperature and baryon density it is expected that in the chiral limit the chiral phase transition is of first order. Increasing the quark mass from zero, the chiral transition becomes more weakly first order, and can end in a chiral critical point. We show that the only massless field at the chiral critical point is a σ meson, with the universality class that of the Ising model. Present day lattice simulations indicate that QCD is (relatively) near to the chiral critical point

  4. Asymmetric synthesis using chiral-encoded metal

    Science.gov (United States)

    Yutthalekha, Thittaya; Wattanakit, Chularat; Lapeyre, Veronique; Nokbin, Somkiat; Warakulwit, Chompunuch; Limtrakul, Jumras; Kuhn, Alexander

    2016-08-01

    The synthesis of chiral compounds is of crucial importance in many areas of society and science, including medicine, biology, chemistry, biotechnology and agriculture. Thus, there is a fundamental interest in developing new approaches for the selective production of enantiomers. Here we report the use of mesoporous metal structures with encoded geometric chiral information for inducing asymmetry in the electrochemical synthesis of mandelic acid as a model molecule. The chiral-encoded mesoporous metal, obtained by the electrochemical reduction of platinum salts in the presence of a liquid crystal phase and the chiral template molecule, perfectly retains the chiral information after removal of the template. Starting from a prochiral compound we demonstrate enantiomeric excess of the (R)-enantiomer when using (R)-imprinted electrodes and vice versa for the (S)-imprinted ones. Moreover, changing the amount of chiral cavities in the material allows tuning the enantioselectivity.

  5. Nucleon parton distributions in chiral perturbation theory

    International Nuclear Information System (INIS)

    Moiseeva, Alena

    2013-01-01

    Properties of the chiral expansion of nucleon light-cone operators have been studied. In the framework of the chiral perturbation theory we have demonstrated that convergency of the chiral expansion of nucleon parton distributions strongly depends on the value of the variable x. Three regions in x with essentially different analytical properties of the resulting chiral expansion for parton distributions were found. For each of the regions we have elaborated special power counting rules corresponding to the partial resummation of the chiral series. The nonlocal effective operators for the vector and the axial nucleon parton distributions have been constructed at the zeroth and the first chiral order. Using the derived nonlocal operators and the derived power counting rules we have obtained the second order expressions for the nucleon GPDs H(x,ξ,Δ 2 ), H(x,ξ,Δ 2 ),E(x,ξ,Δ 2 ) valid in the region x>or similar a 2 χ .

  6. Bootstrapping N=2 chiral correlators

    Science.gov (United States)

    Lemos, Madalena; Liendo, Pedro

    2016-01-01

    We apply the numerical bootstrap program to chiral operators in four-dimensional N=2 SCFTs. In the first part of this work we study four-point functions in which all fields have the same conformal dimension. We give special emphasis to bootstrapping a specific theory: the simplest Argyres-Douglas fixed point with no flavor symmetry. In the second part we generalize our setup and consider correlators of fields with unequal dimension. This is an example of a mixed correlator and allows us to probe new regions in the parameter space of N=2 SCFTs. In particular, our results put constraints on relations in the Coulomb branch chiral ring and on the curvature of the Zamolodchikov metric.

  7. Bootstrapping N=2 chiral correlators

    Energy Technology Data Exchange (ETDEWEB)

    Lemos, Madalena [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Liendo, Pedro [Humboldt-Univ. Berlin (Germany). IMIP

    2015-12-15

    We apply the numerical bootstrap program to chiral operators in four-dimensional N=2 SCFTs. In the first part of this work we study four-point functions in which all fields have the same conformal dimension. We give special emphasis to bootstrapping a specific theory: the simplest Argyres-Douglas fixed point with no flavor symmetry. In the second part we generalize our setup and consider correlators of fields with unequal dimension. This is an example of a mixed correlator and allows us to probe new regions in the parameter space of N=2 SCFTs. In particular, our results put constraints on relations in the Coulomb branch chiral ring and on the curvature of the Zamolodchikov metric.

  8. Bootstrapping N=2 chiral correlators

    Energy Technology Data Exchange (ETDEWEB)

    Lemos, Madalena [DESY Hamburg, Theory Group,Notkestrasse 85, D-22607 Hamburg (Germany); Liendo, Pedro [IMIP, Humboldt-Universität zu Berlin, IRIS Adlershof,Zum Großen Windkanal 6, 12489 Berlin (Germany)

    2016-01-07

    We apply the numerical bootstrap program to chiral operators in four-dimensional N=2 SCFTs. In the first part of this work we study four-point functions in which all fields have the same conformal dimension. We give special emphasis to bootstrapping a specific theory: the simplest Argyres-Douglas fixed point with no flavor symmetry. In the second part we generalize our setup and consider correlators of fields with unequal dimension. This is an example of a mixed correlator and allows us to probe new regions in the parameter space of N=2 SCFTs. In particular, our results put constraints on relations in the Coulomb branch chiral ring and on the curvature of the Zamolodchikov metric.

  9. Chiral Tunnelling in Twisted Graphene Bilayer

    OpenAIRE

    He, Wen-Yu; Chu, Zhao-Dong; He, Lin

    2013-01-01

    The perfect transmission in graphene monolayer and the perfect reflection in Bernal graphene bilayer for electrons incident in the normal direction of a potential barrier are viewed as two incarnations of the Klein paradox. Here we show a new and unique incarnation of the Klein paradox. Owing to the different chiralities of the quasiparticles involved, the chiral fermions in twisted graphene bilayer shows adjustable probability of chiral tunnelling for normal incidence: they can be changed fr...

  10. Enantioselective Biotransformation of Chiral Persistent Organic Pollutants.

    Science.gov (United States)

    Zhang, Ying; Ye, Jing; Liu, Min

    2017-01-01

    Enantiomers of chiral compounds commonly undergo enantioselective transformation in most biologically mediated processes. As chiral persistent organic pollutants (POPs) are extensively distributed in the environment, differences between enantiomers in biotransformation should be carefully considered to obtain exact enrichment and specific health risks. This review provides an overview of in vivo biotransformation of chiral POPs currently indicated in the Stockholm Convention and their chiral metabolites. Peer-reviewed journal articles focused on the research question were thoroughly searched. A set of inclusion and exclusion criteria were developed to identify relevant studies. We mainly compared the results from different animal models under controlled laboratory conditions to show the difference between enantiomers in terms of distinct transformation potential. Interactions with enzymes involved in enantioselective biotransformation, especially cytochrome P450 (CYP), were discussed. Further research areas regarding this issue were proposed. Limited evidence for a few POPs has been found in 30 studies. Enantioselective biotransformation of α-hexachlorocyclohexane (α-HCH), chlordane, dichlorodiphenyltrichloroethane (DDT), heptachlor, hexabromocyclododecane (HBCD), polychlorinated biphenyls (PCBs), and toxaphene, has been investigated using laboratory mammal, fish, bird, and worm models. Tissue and excreta distributions, as well as bioaccumulation and elimination kinetics after administration of racemate and pure enantiomers, have been analyzed in these studies. Changes in enantiomeric fractions have been considered as an indicator of enantioselective biotransformation of chiral POPs in most studies. Results of different laboratory animal models revealed that chiral POP biotransformation is seriously affected by chirality. Pronounced results of species-, tissue-, gender-, and individual-dependent differences are observed in in vivo biotransformation of chiral POPs

  11. Supersymmetry and the chiral Schwinger model

    International Nuclear Information System (INIS)

    Amorim, R.; Das, A.

    1998-01-01

    We have constructed the N= (1) /(2) supersymmetric general Abelian model with asymmetric chiral couplings. This leads to a N= (1) /(2) supersymmetrization of the Schwinger model. We show that the supersymmetric general model is plagued with problems of infrared divergence. Only the supersymmetric chiral Schwinger model is free from such problems and is dynamically equivalent to the chiral Schwinger model because of the peculiar structure of the N= (1) /(2) multiplets. copyright 1998 The American Physical Society

  12. Probing chirality with a femtosecond reaction microscope

    Directory of Open Access Journals (Sweden)

    Janssen M. H. M.

    2013-03-01

    Full Text Available Detection of molecular chirality with high sensitivity and selectivity is important for many analytical and practical applications. Photoionization has emerged as a very sensitive probe of chirality in molecules. We show here that a table top setup with a femtosecond laser and a single imaging detector for both photoelectrons and photoions enables detection of chirality up to 3 orders of magnitude better than the existing conventional absorption based techniques.

  13. A spectral route to determining chirality

    DEFF Research Database (Denmark)

    Pedersen, Jesper Goor; Mortensen, Asger

    2009-01-01

    We show how one-dimensional structured media can be used to measure chirality, via the spectral shift of the photonic band gap edges. Analytically, we show that a chiral contrast can, in some cases, be mapped unto an index contrast, thereby greatly simplifying the analysis of such structures. Using...... this mapping, we derive a first-order shift of the band gap edges with chirality. Potentially, this effect could be used for measuring enantiomeric excess....

  14. Higher derivative regularization and chiral anomaly

    International Nuclear Information System (INIS)

    Nagahama, Yoshinori.

    1985-02-01

    A higher derivative regularization which automatically leads to the consistent chiral anomaly is analyzed in detail. It explicitly breaks all the local gauge symmetry but preserves global chiral symmetry and leads to the chirally symmetric consistent anomaly. This regularization thus clarifies the physics content contained in the consistent anomaly. We also briefly comment on the application of this higher derivative regularization to massless QED. (author)

  15. Chiral anomaly, bosonization and fractional charge

    International Nuclear Information System (INIS)

    Mignaco, J.A.; Rego Monteiro, M.A. do.

    1984-01-01

    A method to evaluate the Jacobian of chiral rotations, regulating determinants through the proper time method and using Seeley's asymptotic expansion is presented. With this method the chiral anomaly ofr ν=4,6 dimensions is computed easily, bosonization of some massless two-dimensional models is discussed and the problem of charge fractionization is handled. Besides, the general validity of Fujikawa's approach to regulate the Jacobian of chiral rotations with non-hermitean operators is commented. (Author) [pt

  16. The chirality operators for Heisenberg spin systems

    International Nuclear Information System (INIS)

    Subrahmanyam, V.

    1994-01-01

    The ground state of closed Heisenberg spin chains with an odd number of sites has a chiral degeneracy, in addition to a two-fold Kramers degeneracy. A non-zero chirality implies that the spins are not coplanar, and is a measure of handedness. The chirality operator, which can be treated as a spin-1/2 operator, is explicitly constructed in terms of the spin operators, and is given as commutator of permutation operators. (author). 3 refs

  17. Chiral anomaly, bosonization, and fractional charge

    International Nuclear Information System (INIS)

    Mignaco, J.A.; Monteiro, M.A.R.

    1985-01-01

    We present a method to evaluate the Jacobian of chiral rotations, regulating determinants through the proper-time method and using Seeley's asymptotic expansion. With this method we compute easily the chiral anomaly for ν = 4,6 dimensions, discuss bosonization of some massless two-dimensional models, and handle the problem of charge fractionization. In addition, we comment on the general validity of Fujikawa's approach to regulate the Jacobian of chiral rotations with non-Hermitian operators

  18. Broadband reflection of polymer-stabilized chiral nematic liquid crystals induced by a chiral azobenzene compound.

    Science.gov (United States)

    Chen, Xingwu; Wang, Ling; Chen, Yinjie; Li, Chenyue; Hou, Guoyan; Liu, Xin; Zhang, Xiaoguang; He, Wanli; Yang, Huai

    2014-01-21

    A chiral nematic liquid crystal-photopolymerizable monomer-chiral azobenzene compound composite was prepared and then polymerized under UV irradiation. The reflection wavelength of the composite can be extended to cover the 1000-2400 nm range and also be adjusted to the visible light region by controlling the concentration of chiral compounds.

  19. Staggered chiral random matrix theory

    International Nuclear Information System (INIS)

    Osborn, James C.

    2011-01-01

    We present a random matrix theory for the staggered lattice QCD Dirac operator. The staggered random matrix theory is equivalent to the zero-momentum limit of the staggered chiral Lagrangian and includes all taste breaking terms at their leading order. This is an extension of previous work which only included some of the taste breaking terms. We will also present some results for the taste breaking contributions to the partition function and the Dirac eigenvalues.

  20. Homogenization of resonant chiral metamaterials

    OpenAIRE

    Andryieuski, Andrei; Menzel, Christoph; Rockstuhl, Carsten; Malureanu, Radu; Lederer, Falk; Lavrinenko, Andrei

    2010-01-01

    Homogenization of metamaterials is a crucial issue as it allows to describe their optical response in terms of effective wave parameters as e.g. propagation constants. In this paper we consider the possible homogenization of chiral metamaterials. We show that for meta-atoms of a certain size a critical density exists above which increasing coupling between neighboring meta-atoms prevails a reasonable homogenization. On the contrary, a dilution in excess will induce features reminiscent to pho...

  1. Chiral Lagrangians and the SSC

    International Nuclear Information System (INIS)

    Dawson, S.

    1991-09-01

    In the event that the SSC does not observe any resonances such as a Higgs boson or a techni-rho meson, we would like to know if the SSC can still discover something about the nature of the electroweak symmetry breaking. We will use chiral Lagrangian techniques to address this question and analyze their utility for studying events containing W and Z gauge bosons at the SSC. 20 refs., 4 figs

  2. hf alkylation in the 1980's: the role of isobutane/olefin ratio

    Energy Technology Data Exchange (ETDEWEB)

    Hutson, T. Jr.

    1978-08-01

    Research devoted to maximizing no-lead octane numbers in motor fuel is reported. Results of the studies are the basis for the following conclusions: 1. Isobutane alkylate made from either propylene, butene-2, or C/sub 3/--C/sub 4/ mixed olefins is a low sensitivity, high motor octane product. Typically, C/sub 3/--C/sub 4/ mixed olefin alkylate has a clear motor octane number of about 92.2 and a clear Research octane number of about 93.5. 2. In separate studies with propylene, butene-2 and C/sub 3/--C/sub 4/ mixed olefins, increasing the isobutane-to-olefin ratio suppressed the formation of high molecular weight residue, indicating a substantial reduction in the role of olefin polymerization to large ions. The overall result of increasing ratio was an improvement in selectivity to high-octane components in the alkylate. 3. When alkylating isobutane with propylene, increasing the ratio resulted in a decrease in the concentration of C/sub 7/-fraction (primary product) and an increase in the C/sub 8/-fraction (from chain initiation and subsequent hydrogen transfer). At the same time, the production of chain-termination-product propane also increased. 4. When alkylating isobutane with C/sub 3/--C/sub 4/ mixed olefins, increasing the ratio showed the same trend obtained in separate alkylation tests with propylene and butene-2. As the ratio increased, the concentration of C/sub 7/-fraction (primary propylene--isobutane product) decreased and the concentration of C/sub 8/-fraction increased markedly. Thus, increasing isobutane-to-olefin ratio exerted a strong effect on alkylate quality in the area of about 5 to 1 to 20 to 1; this effect diminished at ratios 20:1.

  3. Is there chirality in atomic nuclei?

    International Nuclear Information System (INIS)

    Meng Jie

    2009-01-01

    Static chiral symmetries are common in nature, for example, the macroscopic spirals of snail shells, the microscopic handedness of certain molecules, and human hands. The concept of chirality in atomic nuclei was first proposed in 1997, and since then many efforts have been made to understand chiral symmetry and its spontaneous breaking in atomic nuclei. Recent theoretical and experimental progress in the verification of chirality in atomic nuclei will be reviewed, together with a discussion of the problems that await to be solved in the future. (authors)

  4. Laser Writing of Multiscale Chiral Polymer Metamaterials

    Directory of Open Access Journals (Sweden)

    E. P. Furlani

    2012-01-01

    Full Text Available A new approach to metamaterials is presented that involves laser-based patterning of novel chiral polymer media, wherein chirality is realized at two distinct length scales, intrinsically at the molecular level and geometrically at a length scale on the order of the wavelength of the incident field. In this approach, femtosecond-pulsed laser-induced two-photon lithography (TPL is used to pattern a photoresist-chiral polymer mixture into planar chiral shapes. Enhanced bulk chirality can be realized by tuning the wavelength-dependent chiral response at both the molecular and geometric level to ensure an overlap of their respective spectra. The approach is demonstrated via the fabrication of a metamaterial consisting of a two-dimensional array of chiral polymer-based L-structures. The fabrication process is described and modeling is performed to demonstrate the distinction between molecular and planar geometric-based chirality and the effects of the enhanced multiscale chirality on the optical response of such media. This new approach to metamaterials holds promise for the development of tunable, polymer-based optical metamaterials with low loss.

  5. Self-inductance of chiral conducting nanotubes

    International Nuclear Information System (INIS)

    Miyamoto, Yoshiyuki; Rubio, Angel; Louie, Steven G.; Cohen, Marvin L.

    1998-01-01

    Chiral conductivity in nanotubes has recently been predicted theoretically. The realization and application of chiral conducting nanotubes can be of great interest from both fundamental and technological viewpoints. These chiral currents, if they are realized, can be detected by measuring the self-inductance. We have treated Maxwell's equations for chiral conducting nanotubes (nanocoils) and find that the self-inductance and the resistivity of nanocoils should depend on the frequency of the alternating current even when the capacitance of the nanocoils is not taken into account. This is in contrast to elementary treatment of ordinary coils. This fact is useful to distinguish nanocoils by electrical measurements

  6. Chiral four-membered cyclic nitrones; asymmetric induction in the (4+2)-cycloaddition reaction of chiral ynamines and nitroalkenes

    NARCIS (Netherlands)

    van Elburg, P.A.; Honig, G.W.N.; Reinhoudt, David

    1987-01-01

    Chiral four-membered cyclic nitrones were synthesized by the asymmetric (4+2)-cycloaddition of nitroalkenes 1 and chiral ynamines 2. The subsequent stereoselective addition of nucleophiles to these nitrones enabled the synthesis of chiral N-hydroxyazetidines.

  7. Two-chiral-component microemulsion electrokinetic chromatography-chiral surfactant and chiral oil: part 1. dibutyl tartrate.

    Science.gov (United States)

    Kahle, Kimberly A; Foley, Joe P

    2007-06-01

    The first simultaneous use of a chiral surfactant and a chiral oil for microemulsion EKC (MEEKC) is reported. Six stereochemical combinations of dodecoxycarbonylvaline (DDCV: R, S, or racemic, 2.00% w/v), racemic 2-hexanol (1.65% v/v), and dibutyl tartrate (D, L, or racemic, 1.23% v/v) were examined as chiral pseudostationary phases (PSPs) for the separation of six pairs of pharmaceutical enantiomers: pseudoephedrine, ephedrine, N-methyl ephedrine, metoprolol, synephrine, and atenolol. Subtle differences were observed for three chromatographic figures of merit (alpha(enant), alpha(meth), k) among the chiral microemulsions; a moderate difference was observed for efficiency (N) and elution range. Dual-chirality microemulsions provided both the largest and smallest enantioselectivities, due to small positive and negative synergies between the chiral microemulsion components. For the ephedrine family of compounds, dual-chiral microemulsions with surfactant and oil in opposite stereochemical configurations provided higher enantioselectivities than the single-chiral component microemulsion (RXX), whereas dual-chiral microemulsions with surfactant and oil in the same stereochemical configurations provided lower enantioselectivities than RXX. Slight to moderate enantioselective synergies were confirmed using a thermodynamic model. Efficiencies observed with microemulsions comprised of racemic dibutyl tartrate or dibutyl-D-tartrate were significantly higher than those obtained with dibutyl-L-tartrate, with an average difference in plate count of about 25 000. Finally, one two-chiral-component microemulsion (RXS) provided significantly better resolution than the remaining one- and two-chiral-component microemulsions for the ephedrine-based compounds, but only slightly better or equivalent resolution for non-ephedrine compounds.

  8. Chiral ferrocenes in asymmetric catalysis: synthesis and applications

    National Research Council Canada - National Science Library

    Dai, Li-Xin; Hou, Xue-Long

    2010-01-01

    .... It provides a thorough overview of the synthesis and characterization of different types of chiral ferrocene ligands, their application to various catalytic asymmetric reactions, and versatile chiral...

  9. Proceedings of the DGMK-Conference 'Creating value from light olefins - production and conversion'. Authors' manuscripts

    Energy Technology Data Exchange (ETDEWEB)

    Emig, G.; Kraemer, H.J.; Weitkamp, J. (eds.)

    2001-07-01

    Main topics of the conference were: production of light olefin by steamcracking and catalytic cracking processes, catalysts, methanol to olefin processes, oxidative dehydrogenation, partial oxidation, selective oxidation of alkanes with various catalysts. (uke)

  10. (Electro)Mechanical Properties of Olefinic Block Copolymers

    Science.gov (United States)

    Spontak, Richard

    2014-03-01

    Conventional styrenic triblock copolymers (SBCs) swollen with a midblock-selective oil have been previously shown to exhibit excellent electromechanical properties as dielectric elastomers. In this class of electroactive polymers, compliant electrodes applied as active areas to opposing surfaces of an elastomer attract each other, and thus compress the elastomer due to the onset of a Maxwell stress, upon application of an external electric field. This isochoric process is accompanied by an increase in lateral area, which yields the electroactuation strain (measuring beyond 300% in SBC systems). Performance parameters such as the Maxwell stress, transverse strain, dielectric breakdown, energy density and electromechanical efficiency are determined directly from the applied electric field and resulting electroactuation strain. In this study, the same principle used to evaluate SBC systems is extended to olefinic block copolymers (OBCs), which can be described as randomly-coupled multiblock copolymers that consist of crystallizable polyethylene hard segments and rubbery poly(ethylene-co-octene) soft segments. Considerations governing the development of a methodology to fabricate electroresponsive OBC systems are first discussed for several OBCs differing in composition and bulk properties. Evidence of electroactuation in selectively-solvated OBC systems is presented and performance metrics measured therefrom are quantitatively compared with dielectric elastomers derived from SBC and related materials.

  11. Separation of products of alkylation of isobutane by olefins

    Energy Technology Data Exchange (ETDEWEB)

    Ward, J.

    1979-03-15

    The alkylation (A1) of isobutane (I) by propylene, butylene and amylenes is carried out at 24-52 degrees, pressure sufficient to maintain the liquid phase, and a molar ratio of I to olefins (O1) 10:1-15:1. The bulk ratio of catalysts to hydrocarbons in the reaction zone was 0.5:1-10:1; when using HF-K-T as the catalysts, it should contain less than 5 percent water and greater than or equal to 65 percent titrated HF. The hydrocarbon products (UP) from the alkylation zone are added after separating the catalyst in a fractionation tower; distillation is carried out at 38-49 degrees and 1.03-1.3 NPa. The head fraction containing I and less than 50 molar percent C3H8 and also fraction I at the point below the input side of the UP which contains less than 8 molar percent C3H8 and fraction n-C4H10 at the point below the point of discharge of fraction I is drained from the tower. The alkylate is discharged at the bottom of the tower. According to the patent the tower operates at low pressure. This improves relative volatility of individual components and reduces heat consumption. The best results are obtained when a head fraction or the concentration C3H8 approximately 25 molar percent is discharged.

  12. Catalyst compositions useful for olefin isomerization and disproportionation

    International Nuclear Information System (INIS)

    Drake, C.A.

    1987-01-01

    A process is described for the double bond isomerization of an aliphatic olefinic hydrocarbon feed which comprises contacting the feed under isomerization conditions with a catalyst prepared by: (a) impregnating an alumina support having a surface area of at least 200 m/sup 2//g and a pore volume of at least 0.45 cm/sup 3//g with: 1 up to 20 wt. % of at least one magnesium compound convertible to the oxide, based on the weight of support and calculated as the metal; 0 up to 5 wt. % of at least one alkali metal compound convertible to the oxide, based on the weight of support and calculated as the metal; and 0 up to 5 wt. % of at least one zirconium compound convertible to the oxide, based on the weight of support and calculated as the metal; and (b) heating the alumina support impregnated in accordance with step (a) in an oxygen-containing atmosphere under conditions suitable to convert at least a portion of the magnesium, alkali metal, and zirconium compounds to the oxide form

  13. Radiation degradation of poly(olefin sulphone)s - Fundamental research to practical applications

    International Nuclear Information System (INIS)

    Bowden, M.J.; O'Donnell, J.H.

    1985-01-01

    The degradation of poly(olefin sulphone)s by high energy radiation, particularly by γ-rays and electron beams, provides an example of the application of fundamental science to high technology industry. Scientific interest in the radiation degradation of these polymers was first aroused by the discovery that they underwent highly specific bond scission in the backbone chain as the primary result of absorption of high energy radiation and in fact they were the first polymers in which such an effect had been demonstrated. This conclusion was initially based mainly on evidence from electron spin resonance spectroscopy and was subsequently verified by studies of molecular weight changes. These studies showed that the poly(olefin sulphone)s not only degraded by main chain scission but were also among the most radiation-sensitive polymers known. The extremely high sensitivity of poly(olefin sulphone)s to radiation-induced main-chain scission has found application in the field of microelectronics. Electron beam writing on poly(olefin sulphone) films is used to produce lithographic masks for the manufacture of integrated circuits on silicon wafers. Poly(1-butene sulphone) (PBS) is currently used in the production of a substantial proportion of the masks for the industry. The fundamental aspects of the radiation degradation of poly(olefin sulphone)s and the practical applications to high technology are reviewed. (author)

  14. Optimization of catalytic glycerol steam reforming to light olefins using Cu/ZSM-5 catalyst

    International Nuclear Information System (INIS)

    Zakaria, Z.Y.; Amin, N.A.S.; Linnekoski, J.

    2014-01-01

    Highlights: • Glycerol steam reforming to light olefin using Cu/ZSM-5 process was optimized. • Response surface methodology and multi-objective genetic algorithm were employed. • Second order polynomial model produced adequately fitted experimental data. • Thermodynamic study inferred high temperature requirement for ethylene formation. • Turn-over-frequency at optimized responses is higher than the non-optimized process. - Abstract: Response surface methodology (RSM) and multi-objective genetic algorithm was employed to optimize the process parameters for catalytic conversion of glycerol, a byproduct from biodiesel production, to light olefins using Cu/ZSM-5 catalyst. The effects of operating temperature, weight hourly space velocity (WHSV) and glycerol concentration on light olefins selectivity and yield were observed. Experimental results revealed the data adequately fitted into a second-order polynomial model. The linear temperature and quadratic WHSV terms gave significant effect on both responses. Optimization of both the responses indicated that temperature favouring high light olefin formation lied beyond the experimental design range. The trend in the temperature profile concurred commensurately with the thermodynamic analysis. Multi-objective genetic algorithm was performed to attain a single set of processing parameters that could produce both the highest light olefin selectivity and yield. The turn-over-frequency (TOF) of the optimized responses demonstrated a slightly higher value than the one which was not optimized. Combination of RSM, multi-objective response and thermodynamic is useful to determine the process optimal operating conditions for industrial applications

  15. Direct Olefination of Alcohols with Sulfones by Using Heterogeneous Platinum Catalysts.

    Science.gov (United States)

    Siddiki, S M A Hakim; Touchy, Abeda Sultana; Kon, Kenichi; Shimizu, Ken-Ichi

    2016-04-18

    Carbon-supported Pt nanoparticles (Pt/C) were found to be effective heterogeneous catalysts for the direct Julia olefination of alcohols in the presence of sulfones and KOtBu under oxidant-free conditions. Primary alcohols, including aryl, aliphatic, allyl, and heterocyclic alcohols, underwent olefination with dimethyl sulfone and aryl alkyl sulfones to give terminal and internal olefins, respectively. Secondary alcohols underwent methylenation with dimethyl sulfone. Under 2.5 bar H2, the same reaction system was effective for the transformation of alcohol OH groups to alkyl groups. Structural and mechanistic studies of the terminal olefination system suggested that Pt(0) sites on the Pt metal particles are responsible for the rate-limiting dehydrogenation of alcohols and that KOtBu may deprotonate the sulfone reagent. The Pt/C catalyst was reusable after the olefination, and this method showed a higher turnover number (TON) and a wider substrate scope than previously reported methods, which demonstrates the high catalytic efficiency of the present method. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Use of water in aiding olefin/paraffin (liquid + liquid) extraction via complexation with a silver bis(trifluoromethylsulfonyl)imide salt

    International Nuclear Information System (INIS)

    Wang, Yu; Thompson, Jillian; Zhou, Jingjing; Goodrich, Peter; Atilhan, Mert; Pensado, Alfonso S.; Kirchner, Barbara; Rooney, David; Jacquemin, Johan; Khraisheh, Majeda

    2014-01-01

    Highlights: • Silver-based ILs used as olefin extracting agents for olefin/paraffin mixtures. • Each extraction process is based on the olefin complexation and solvation. • The presence of water influences positively each extraction process. • Each extraction process was evaluated by DFT calculations, NMR, IR and Raman. • LLE data were then correlated by using the UNIQUAC model. - Abstract: This paper describes the extraction of C 5 –C 8 linear α-olefins from olefin/paraffin mixtures of the same carbon number via a reversible complexation with a silver salt (silver bis(trifluoromethylsulfonyl)imide, Ag[Tf 2 N]) to form room temperature ionic liquids [Ag(olefin) x ][Tf 2 N]. From the experimental (liquid + liquid) equilibrium data for the olefin/paraffin mixtures and Ag[Tf 2 N], 1-pentene showed the best separation performance while C 7 and C 8 olefins could only be separated from the corresponding mixtures on addition of water which also improves the selectivity at lower carbon numbers like the C 5 and C 6 , for example. Using infrared and Raman spectroscopy of the complex and Ag[Tf 2 N] saturated by olefin, the mechanism of the extraction was found to be based on both chemical complexation and the physical solubility of the olefin in the ionic liquid ([Ag(olefin) x ][Tf 2 N]). These experiments further support the use of such extraction techniques for the separation of olefins from paraffins

  17. Rh(iii)-catalyzed C-H olefination of N-pentafluoroaryl benzamides using air as the sole oxidant.

    Science.gov (United States)

    Lu, Yi; Wang, Huai-Wei; Spangler, Jillian E; Chen, Kai; Cui, Pei-Pei; Zhao, Yue; Sun, Wei-Yin; Yu, Jin-Quan

    2015-03-01

    The oxidative olefination of a broad array of arenes and heteroarenes with a variety of activated and unactivated olefins has be achieved via a rhodium(iii)-catalyzed C-H activation reaction. The use of an N -pentafluorophenyl benzamide directing group is crucial for achieving catalytic turnovers in the presence of air as the sole oxidant without using a co-oxidant.

  18. (E)-Specific direct Julia-olefination of aryl alcohols without extra reducing agents promoted by bases.

    Science.gov (United States)

    Yao, Chuan-Zhi; Li, Qiang-Qiang; Wang, Mei-Mei; Ning, Xiao-Shan; Kang, Yan-Biao

    2015-05-04

    An unprecedented base-promoted direct olefination of aryl alcohols with sulfones via a Julia-type reaction has been described. No extra reductants are needed for Julia reaction since alcohols work as double sources of aldehydes and the hydride. Generally high yields were given for both terminal and highly (E)-selective internal olefins.

  19. Pion polarizability in a chiral quark model

    International Nuclear Information System (INIS)

    Ebert, D.; Volkov, M.K.

    1981-01-01

    The pion polarizability is calculated in a chiral meson-quark model at the one-loop level. The results are in complete agreement with earlier ones obtained within a chiral meson-baryon theory. A critical discussion of a recent paper by Llanta and Tarrach is given. (orig.)

  20. Pion polarizability in a chiral quark model

    International Nuclear Information System (INIS)

    Volkov, M.K.; Ehbert, D.

    1981-01-01

    The pion polarizability is calculated in a chiral meson- quark model at the one-loop level. The results are in complete agreement with earlier ones obtained within a chiral meson-baryon theory. A critical discussion of a recent paper by Llanta and Tarrach is given [ru