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Sample records for acid catalyzed inverse-electron-demand

  1. An intramolecular inverse electron demand Diels–Alder approach to annulated α-carbolines

    Directory of Open Access Journals (Sweden)

    Zhiyuan Ma

    2012-06-01

    Full Text Available Intramolecular inverse electron demand cycloadditions of isatin-derived 1,2,4-triazines with acetylenic dienophiles tethered by amidations or transesterifications proceed in excellent yields to produce lactam- or lactone-fused α-carbolines. Beginning with various isatins and alkynyl dienophiles, a pilot-scale library of eighty-eight α-carbolines was prepared by using this robust methodology for biological evaluation.

  2. Synthesis of 3,4-dihydro-1,8-naphthyridin-2(1H-ones via microwave-activated inverse electron-demand Diels–Alder reactions

    Directory of Open Access Journals (Sweden)

    Salah Fadel

    2014-01-01

    Full Text Available Substituted 3,4-dihydro-1,8-naphthyridin-2(1H-ones have been synthesized with the inverse electron-demand Diels–Alder reaction from 1,2,4-triazines bearing an acylamino group with a terminal alkyne side chain. Alkynes were first subjected to the Sonogashira cross-coupling reaction with aryl halides, the product of which then underwent an intramolecular inverse electron-demand Diels–Alder reaction to yield 5-aryl-3,4-dihydro-1,8-naphthyridin-2(1H-ones by an efficient synthetic route.

  3. THE DIELS-ALDER-REACTION WITH INVERSE-ELECTRON-DEMAND - A REVIEW OF AN EFFICIENT & ATTRACTIVE CLICK-REACTION CONCEPT

    Directory of Open Access Journals (Sweden)

    Klaus Braun

    2013-10-01

    Full Text Available Here, we review the development of prospective image processing systems in molecular diagnostics and of pharmacologically active ingredients for patient-specific therapeutic approaches. These projects require not only high demands on quality, safety, and specificity but also, rapid, efficient and irreversible ligation routes during the synthesis of future pharmaceuticals. The Diels-Alder ligation reaction with inverse electron demand (DARinv is an eligible technology not restricted to medical applications, but valuable in selective modification by functionalization of polymers, organic and inorganic surfaces and micro arrays. Additionally, the DARinv technology is considered as an attractive strategy-platform for efficient syntheses of promising pharmacologically active components and derivatives of natural molecules with an optimized therapeutic index. We like to encourage scientists working with the brilliant concept of Sharpless’s “Click chemistry”, to intensify their research with this valuable DARinv technology able to open the door for regioselective, stereospecific, and bioorthogonal exigent syntheses of substances of highest quality inconceivable so far.

  4. The Diels-Alder-Reaction with inverse-Electron-Demand, a very efficient versatile Click-Reaction Concept for proper Ligation of variable molecular Partners

    OpenAIRE

    Manfred Wiessler, Waldemar Waldeck, Christian Kliem, Ruediger Pipkorn, Klaus Braun

    2010-01-01

    The ligation of active pharmaceutical ingredients (API) for working with image processing systems in diagnostics (MRT) attracts increasing notice and scientific interest. The Diels-Alder ligation Reaction with inverse electron demand (DARinv) turns out to be an appropriate candidate. The DARinv is characterized by a specific distribution of electrons of the diene and the corresponding dienophile counterpart. Whereas the reactants in the classical Diels-Alder Reaction feature electron-rich die...

  5. The Diels-Alder-Reaction with inverse-Electron-Demand, a very efficient versatile Click-Reaction Concept for proper Ligation of variable molecular Partners

    OpenAIRE

    Wiessler, Manfred; Waldeck, Waldemar; Kliem, Christian; Pipkorn, Ruediger; Braun, Klaus

    2009-01-01

    The ligation of active pharmaceutical ingredients (API) for working with image processing systems in diagnostics (MRT) attracts increasing notice and scientific interest. The Diels-Alder ligation Reaction with inverse electron demand (DARinv) turns out to be an appropriate candidate. The DARinv is characterized by a specific distribution of electrons of the diene and the corresponding dienophile counterpart. Whereas the reactants in the classical Diels-Alder Reaction feature electron-rich die...

  6. Activation-strain analysis reveals unexpected origin of fast reactivity in heteroaromatic azadiene inverse-electron-demand diels-alder cycloadditions.

    Science.gov (United States)

    Talbot, Austin; Devarajan, Deepa; Gustafson, Samantha J; Fernández, Israel; Bickelhaupt, F Matthias; Ess, Daniel H

    2015-01-01

    Heteroaromatic azadienes, especially 1,2,4,5-tetrazines, are extremely reactive partners with alkenes in inverse-electron-demand Diels-Alder reactions. Azadiene cycloaddition reactions are used to construct heterocycles in synthesis and are popular as bioorthogonal reactions. The origin of fast azadiene cycloaddition reactivity is classically attributed to the inverse frontier molecular orbital (FMO) interaction between the azadiene LUMO and alkene HOMO. Here, we use a combination of ab initio, density functional theory, and activation-strain model calculations to analyze physical interactions in heteroaromatic azadiene-alkene cycloaddition transition states. We find that FMO interactions do not control reactivity because, while the inverse FMO interaction becomes more stabilizing, there is a decrease in the forward FMO interaction that is offsetting. Rather, fast cycloadditions are due to a decrease in closed-shell Pauli repulsion between cycloaddition partners. The kinetic-thermodynamic relationship found for these inverse-electron-demand cycloadditions is also due to the trend in closed-shell repulsion in the cycloadducts. Cycloaddition regioselectivity, however, is the result of differences in occupied-unoccupied orbital interactions due to orbital overlap. These results provide a new predictive model and correct physical basis for heteroaromatic azadiene reactivity and regioselectivity with alkene dieneophiles.

  7. The Diels-Alder-Reaction with inverse-Electron-Demand, a very efficient versatile Click-Reaction Concept for proper Ligation of variable molecular Partners

    Directory of Open Access Journals (Sweden)

    Manfred Wiessler, Waldemar Waldeck, Christian Kliem, Ruediger Pipkorn, Klaus Braun

    2010-01-01

    Full Text Available The ligation of active pharmaceutical ingredients (API for working with image processing systems in diagnostics (MRT attracts increasing notice and scientific interest. The Diels-Alder ligation Reaction with inverse electron demand (DARinv turns out to be an appropriate candidate. The DARinv is characterized by a specific distribution of electrons of the diene and the corresponding dienophile counterpart. Whereas the reactants in the classical Diels-Alder Reaction feature electron-rich diene and electron-poor dienophile compounds, the DARinv exhibits exactly the opposite distribution of electrons. Substituents with pushing electrones increase and, with pulling electrons reduce the electron density of the dienes as used in the DARinv. We report here that the DARinv is an efficient route for coupling of multifunctional molecules like active peptides, re-formulated drugs or small molecules like the alkyalting agent temozolomide (TMZ. This is an example of our contribution to the "Click chemistry" technology. In this case TMZ is ligated by DARinv as a cargo to transporter molecules facilitating the passage across the cell membranes into cells and subsequently into subcellular components like the cell nucleus by using address molecules. With such constructs we achieved high local concentrations at the desired target site of pharmacological action. The DARinv ligation was carried out using the combination of several technologies, namely: the organic chemistry and the solid phase peptide synthesis which can produce 'tailored' solutions for questions not solely restricted to the medical diagnostics or therapy, but also result in functionalizations of various surfaces qualified amongst others also for array development. We like to acquaint you with the DARinv and we like to exemplify that all ligation products were generated after a rapid and complete reaction in organic solutions at room temperature, in high purity, but also, hurdles and difficulties on

  8. The Diels-Alder-reaction with inverse-electron-demand, a very efficient versatile click-reaction concept for proper ligation of variable molecular partners.

    Science.gov (United States)

    Wiessler, Manfred; Waldeck, Waldemar; Kliem, Christian; Pipkorn, Ruediger; Braun, Klaus

    2009-12-05

    The ligation of active pharmaceutical ingredients (API) for working with image processing systems in diagnostics (MRT) attracts increasing notice and scientific interest. The Diels-Alder ligation Reaction with inverse electron demand (DAR(inv)) turns out to be an appropriate candidate. The DAR(inv) is characterized by a specific distribution of electrons of the diene and the corresponding dienophile counterpart. Whereas the reactants in the classical Diels-Alder Reaction feature electron-rich diene and electron-poor dienophile compounds, the DAR(inv) exhibits exactly the opposite distribution of electrons. Substituents with pushing electrones increase and, with pulling electrons reduce the electron density of the dienes as used in the DAR(inv).We report here that the DAR(inv) is an efficient route for coupling of multifunctional molecules like active peptides, re-formulated drugs or small molecules like the alkyalting agent temozolomide (TMZ). This is an example of our contribution to the "Click chemistry" technology. In this case TMZ is ligated by DAR(inv) as a cargo to transporter molecules facilitating the passage across the cell membranes into cells and subsequently into subcellular components like the cell nucleus by using address molecules. With such constructs we achieved high local concentrations at the desired target site of pharmacological action. The DAR(inv) ligation was carried out using the combination of several technologies, namely: the organic chemistry and the solid phase peptide synthesis which can produce 'tailored' solutions for questions not solely restricted to the medical diagnostics or therapy, but also result in functionalizations of various surfaces qualified amongst others also for array development.We like to acquaint you with the DAR(inv) and we like to exemplify that all ligation products were generated after a rapid and complete reaction in organic solutions at room temperature, in high purity, but also, hurdles and difficulties on

  9. The Diels-Alder-Reaction with inverse-Electron-Demand, a very efficient versatile Click-Reaction Concept for proper Ligation of variable molecular Partners

    Science.gov (United States)

    Wiessler, Manfred; Waldeck, Waldemar; Kliem, Christian; Pipkorn, Ruediger; Braun, Klaus

    2010-01-01

    The ligation of active pharmaceutical ingredients (API) for working with image processing systems in diagnostics (MRT) attracts increasing notice and scientific interest. The Diels-Alder ligation Reaction with inverse electron demand (DARinv) turns out to be an appropriate candidate. The DARinv is characterized by a specific distribution of electrons of the diene and the corresponding dienophile counterpart. Whereas the reactants in the classical Diels-Alder Reaction feature electron-rich diene and electron-poor dienophile compounds, the DARinv exhibits exactly the opposite distribution of electrons. Substituents with pushing electrones increase and, with pulling electrons reduce the electron density of the dienes as used in the DARinv. We report here that the DARinv is an efficient route for coupling of multifunctional molecules like active peptides, re-formulated drugs or small molecules like the alkyalting agent temozolomide (TMZ). This is an example of our contribution to the "Click chemistry" technology. In this case TMZ is ligated by DARinv as a cargo to transporter molecules facilitating the passage across the cell membranes into cells and subsequently into subcellular components like the cell nucleus by using address molecules. With such constructs we achieved high local concentrations at the desired target site of pharmacological action. The DARinv ligation was carried out using the combination of several technologies, namely: the organic chemistry and the solid phase peptide synthesis which can produce 'tailored' solutions for questions not solely restricted to the medical diagnostics or therapy, but also result in functionalizations of various surfaces qualified amongst others also for array development. We like to acquaint you with the DARinv and we like to exemplify that all ligation products were generated after a rapid and complete reaction in organic solutions at room temperature, in high purity, but also, hurdles and difficulties on the way to the

  10. Lipase catalyzed synthesis of epoxy-fatty acids

    Institute of Scientific and Technical Information of China (English)

    CHEN, Qian; LI, Zu-Yi

    2000-01-01

    Lipase catalyzed synthesis of epoxy-fatty acidas from unsaturated carboxylic acids was investigated.Under mild conditions unsaturated arboxylic acids were convcveed to peroxide,then the unsaturated peroxycarboxylic acids epoxidised the C=C bond of themselves

  11. Modular strategy for the construction of radiometalated antibodies for positron emission tomography based on inverse electron demand Diels-Alder click chemistry.

    Science.gov (United States)

    Zeglis, Brian M; Mohindra, Priya; Weissmann, Gabriel I; Divilov, Vadim; Hilderbrand, Scott A; Weissleder, Ralph; Lewis, Jason S

    2011-10-19

    A modular system for the construction of radiometalated antibodies was developed based on the bioorthogonal cycloaddition reaction between 3-(4-benzylamino)-1,2,4,5-tetrazine and the strained dienophile norbornene. The well-characterized, HER2-specific antibody trastuzumab and the positron emitting radioisotopes (64)Cu and (89)Zr were employed as a model system. The antibody was first covalently coupled to norbornene, and this stock of norbornene-modified antibody was then reacted with tetrazines bearing the chelators 1,4,7,10-tetraazacyclo-dodecane-1,4,7,10-tetraacetic acid (DOTA) or desferrioxamine (DFO) and subsequently radiometalated with (64)Cu and (89)Zr, respectively. The modification strategy is simple and robust, and the resultant radiometalated constructs were obtained in high specific activity (2.7-5.3 mCi/mg). For a given initial stoichiometric ratio of norbornene to antibody, the (64)Cu-DOTA- and (89)Zr-DFO-based probes were shown to be nearly identical in terms of stability, the number of chelates per antibody, and immunoreactivity (>93% in all cases). In vivo PET imaging and acute biodistribution experiments revealed significant, specific uptake of the (64)Cu- and (89)Zr-trastuzumab bioconjugates in HER2-positive BT-474 xenografts, with little background uptake in HER2-negative MDA-MB-468 xenografts or other tissues. This modular system-one in which the divergent point is a single covalently modified antibody stock that can be reacted selectively with various chelators-will allow for both greater versatility and more facile cross-comparisons in the development of antibody-based radiopharmaceuticals.

  12. The Iron-Catalyzed Oxidation of Hydrazine by Nitric Acid

    Energy Technology Data Exchange (ETDEWEB)

    Karraker, D.G.

    2001-07-17

    To assess the importance of iron to hydrazine stability, the study of hydrazine oxidation by nitric acid has been extended to investigate the iron-catalyzed oxidation. This report describes those results.

  13. Palladium-Catalyzed alpha-Arylation of Tetramic Acids

    DEFF Research Database (Denmark)

    Storgaard, Morten; Dorwald, F. Z.; Peschke, B.;

    2009-01-01

    A mild, racemization-free, palladium-Catalyzed alpha-arylation of tetramic acids (2,4-pyrrolidinediones) has been developed. Various amino acid-derived tetramic acids were cleanly arylated by treatment with 2 mol % of Pd(OAc)(2), 4 mol % of a sterically demanding biaryl phosphine, 2.3 equiv of K2...

  14. Kinetic study on the acid-catalyzed hydrolysis of cellulose to levulinic acid

    NARCIS (Netherlands)

    Girisuta, B.; Janssen, L. P. B. M.; Heeres, H. J.

    2007-01-01

    A variety of interesting bulk chemicals is accessible by the acid-catalyzed hydrolysis of cellulose. An interesting example is levulinic acid, a versatile precursor for fuel additives, polymers, and resins. A detailed kinetic study on the acid-catalyzed hydrolysis of cellulose to levulinic acid is r

  15. Amino Acids Catalyzed Direct Aldol Reactions in Aqueous Micelles

    Institute of Scientific and Technical Information of China (English)

    PENG Yi-Yuan; WANG Qi; DING Qiu-Ping; HE Jia-Qi; CHENG Jin-Pei

    2003-01-01

    @@ Since the discovery of its roles as a good small-organic-molecule catalyst in intramolecular aldol reactions, pro line has drawn considerable attention in synthetic chemistry due to its similarity to the type-Ⅰ aldolases. Recently,List and others have reported some new direct asymmetric intermolecular reactions catalyzed by proline, including aldol, Mannich, Michael, and other analogous reactions. Except for two recent examples, [1,2] proline catalyzed aldol reactions in aqueous micelles have not been reported, nor have other amino acids as organocatalysts in directly catalyzing aldol reaction been reported. Herein we wish to present our recent results regarding environmentally be nign direct aldol reactions catalyzed by amino acids including proline, histidine and arginine in aqueous media.

  16. Polyphosphorous acid catalyzed cyclization in the synthesis of cryptolepine derivatives

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    11-Oxo-10,11-dihydroxy-5H-indolo[3,2,b]quinoline7-carboxylic acid was obtained specifically by polyphosphorous acid catalyzed cyclization with optimal reaction conditions. Biological assays showed that it potentially inhibits the proteasomal chymotrypsin-like activity in vitro and suppresses breast cancer cell growth.

  17. Rh-Catalyzed arylation of fluorinated ketones with arylboronic acids.

    Science.gov (United States)

    Dobson, Luca S; Pattison, Graham

    2016-09-25

    The Rh-catalyzed arylation of fluorinated ketones with boronic acids is reported. This efficient process allows access to fluorinated alcohols in high yields under mild conditions. Competition experiments suggest that difluoromethyl ketones are more reactive than trifluoromethyl ketones in this process, despite their decreased electronic activation, an effect we postulate to be steric in origin.

  18. Lipase-Catalyzed Modification of Canola Oil with Caprylic Acid

    DEFF Research Database (Denmark)

    Wang, Yingyao; Luan, Xia; Xu, Xuebing;

    Lipase-catalyzed acidolysis of canola oil with caprylic acid was performed to produce structured lipids. Six commercial lipases from different sources were screened for their ability to incorporate the caprylic acid into the canola oil. The positional distribution of FA on the glycerol backbone...... parameters studied included substrate mole ratio, enzyme load, reaction time and temperature. Incorporation of caprylic acid was higher when reactions were carried with 10% lipase of the total weight of substrates at a mole ratio of oil to caprylic acid of 1:4. The optimal time course and temperature...

  19. Acid-catalyzed kinetics of indium tin oxide etching

    International Nuclear Information System (INIS)

    We report the kinetic characterization of indium tin oxide (ITO) film etching by chemical treatment in acidic and basic electrolytes. It was observed that film etching increased under more acidic conditions, whereas basic conditions led to minimal etching on the time scale of the experiments. Quartz crystal microbalance was employed in order to track the reaction kinetics as a function of the concentration of hydrochloric acid and accordingly solution pH. Contact angle measurements and atomic force microscopy experiments determined that acid treatment increases surface hydrophilicity and porosity. X-ray photoelectron spectroscopy experiments identified that film etching is primarily caused by dissolution of indium species. A kinetic model was developed to explain the acid-catalyzed dissolution of ITO surfaces, and showed a logarithmic relationship between the rate of dissolution and the concentration of undisassociated hydrochloric acid molecules. Taken together, the findings presented in this work verify the acid-catalyzed kinetics of ITO film dissolution by chemical treatment, and support that the corresponding chemical reactions should be accounted for in ITO film processing applications. - Highlights: • Acidic conditions promoted indium tin oxide (ITO) film etching via dissolution. • Logarithm of the dissolution rate depended linearly on the solution pH. • Acid treatment increased ITO surface hydrophilicity and porosity. • ITO film etching led to preferential dissolution of indium species over tin species

  20. Acid-catalyzed oxygen-18 labeling of peptides.

    Science.gov (United States)

    Niles, Richard; Witkowska, H Ewa; Allen, Simon; Hall, Steven C; Fisher, Susan J; Hardt, Markus

    2009-04-01

    In enzymatic (18)O-labeling strategies for quantitative proteomics, the exchange of carboxyl oxygens at low pH is a common, undesired side reaction. We asked if acid-catalyzed back exchange could interfere with quantitation and whether the reaction itself could be used as method for introducing (18)O label into peptides. Several synthetic peptides were dissolved in dilute acid containing 50% (v/v) H(2)(18)O and incubated at room temperature. Aliquots were removed over a period of 3 weeks and analyzed by tandem mass spectrometry (MS/MS). (18)O-incorporation ratios were determined by linear regression analysis that allowed for multiple stable-isotope incorporations. At low pH, peptides exchanged their carboxyl oxygen atoms with the aqueous solvent. The isotope patterns gradually shifted to higher masses until they reached the expected binomial distribution at equilibrium after approximately 11 days. Reaction rates were residue- and sequence-specific. Due to its slow nature, the acid-catalyzed back exchange is expected to minimally interfere with enzymatic (18)O-labeling studies provided that storage and analysis conditions minimize low-pH exposure times. On its own, acid-catalyzed (18)O labeling is a general tagging strategy that is an alternative to the chemical, metabolic, and enzymatic isotope-labeling schemes currently used in quantitative proteomics. PMID:19243188

  1. Synthesis of Rosin Acid Starch Catalyzed by Lipase

    OpenAIRE

    Rihui Lin; He Li; Han Long; Jiating Su; Wenqin Huang

    2014-01-01

    Rosin, an abundant raw material from pine trees, was used as a starting material directly for the synthesis of rosin acid starch. The esterification reaction was catalyzed by lipase (Novozym 435) under mild conditions. Based on single factor experimentation, the optimal esterification conditions were obtained as follows: rosin acid/anhydrous glucose unit in the molar ratio 2 : 1, reaction time 4 h at 45°C, and 15% of lipase dosage. The degree of substitution (DS) reaches 0.098. Product from e...

  2. Synthesis of Rosin Acid Starch Catalyzed by Lipase

    Directory of Open Access Journals (Sweden)

    Rihui Lin

    2014-01-01

    Full Text Available Rosin, an abundant raw material from pine trees, was used as a starting material directly for the synthesis of rosin acid starch. The esterification reaction was catalyzed by lipase (Novozym 435 under mild conditions. Based on single factor experimentation, the optimal esterification conditions were obtained as follows: rosin acid/anhydrous glucose unit in the molar ratio 2 : 1, reaction time 4 h at 45°C, and 15% of lipase dosage. The degree of substitution (DS reaches 0.098. Product from esterification of cassava starch with rosin acid was confirmed by FTIR spectroscopy and iodine coloration analysis. Scanning electron microscopy and X-ray diffraction analysis showed that the morphology and crystallinity of the cassava starch were largely destroyed. Thermogravimetric analysis indicated that thermal stability of rosin acid starch decreased compared with native starch.

  3. Direct amidation of amino acid derivatives catalyzed by arylboronic acids : applications in dipeptide synthesis.

    OpenAIRE

    Liu, S.; Yang, Y.; Liu, X.; Ferdousi, F. K.; Batsanov, A.S.; Whiting, A

    2013-01-01

    The direct amidation of amino acid derivatives catalyzed by arylboronic acids has been examined. The reaction was generally slow relative to simple amine-carboxylic acid combinations though proceeded at 65–68 °C generally avoiding racemization. 3,4,5-Trifluorophenylboronic and o-nitrophenylboronic acids were found to be the best catalysts, though for slower dipeptide formations, high catalyst loadings were required and an interesting synergistic catalytic effect between two arylboronic acids ...

  4. Chiral Phosphoric Acid-Catalyzed Enantioselective Formal [3+2] Cycloaddition of Azomethine Imines with Enecarbamates.

    Science.gov (United States)

    Wang, Yang; Wang, Qian; Zhu, Jieping

    2016-06-01

    The first catalytic asymmetric inverse electron demand 1,3-dipolar cycloaddition of azomethine imines with enecarbamates has been developed. Isoquinoline-fused pyrazolidines containing two or three contiguous stereogenic centers were obtained in high yields with excellent regio-, diastereo-, and enantioselectivities. The pyrazolidine ring can be opened to install an aminal, α-amino nitrile, or homoallylamine function with an excellent control of the newly generated stereogenic center. Access to aminobenzo[a]quinolizidine is also documented. PMID:27135440

  5. Solid acid catalyzed biodiesel production from waste cooking oil

    Energy Technology Data Exchange (ETDEWEB)

    Jacobson, Kathlene; Gopinath, Rajesh; Meher, Lekha Charan; Dalai, Ajay Kumar [Catalysis and Chemical Reaction Engineering Laboratories, Department of Chemical Engineering, University of Saskatchewan, 57 Campus Drive, Saskatoon, SK, S7N 5A9 (Canada)

    2008-12-17

    Various solid acid catalysts were evaluated for the production of biodiesel from low quality oil such as waste cooking oil (WCO) containing 15 wt.% free fatty acids. The zinc stearate immobilized on silica gel (ZS/Si) was the most effective catalyst in simultaneously catalyzing the transesterification of triglycerides and esterification of free fatty acid (FFA) present in WCO to methyl esters. The optimization of reaction parameters with the most active ZS/Si catalyst showed that at 200 C, 1:18 oil to alcohol molar ratio and 3 wt.% catalysts loading, a maximum ester yield of 98 wt.% could be obtained. The catalysts were recycled and reused many times without any loss in activity. (author)

  6. MOLYBDENUM CATALYZED ACID PEROXIDE BLEACHING OF EUCALYPTUS KRAFT PULP

    OpenAIRE

    Marcos S. Rabelo; Jorge L. Colodette; Vera M. Sacon; Marcelo R. Silva; Marco A. B. Azevedo

    2008-01-01

    Molybdenum catalyzed peroxide bleaching (PMo Stage) consists of pulp treatment with hydrogen peroxide under acidic conditions in the presence of a molybdenum catalyst. Molybdenum is applied in catalytic doses (50-200 mg/kg pulp) and may originate from various sources, including (NH4)6Mo7O24.4H2O, Na2MoO4.2H2O, siliconmolybdate, etc. This work is aimed at optimizing the PMo stage and evaluating its industrial application in the OAZDP sequence. Optimum PMo stage conditions for bleaching eucalyp...

  7. An Efficient Procedure for Esterification of Aryloxyacetic Acid and Arylthioacetic Acid Catalyzed by Silica Sulfuric Acid

    Institute of Scientific and Technical Information of China (English)

    LI,Hong-Ya; LI,Ji-Tai; LI,Hui-Zhang

    2004-01-01

    @@ Aryloxyacetate and arylthioacetate are wildly used in herbicides, plant regulator and insecticides. Recently, Wille et al. have reported that methyl aryloxyacetate is an efficient agent to prevent and treat allergic contact dermatitis.[1] The most popular synthesis is by heating sodium phenoxide (mercaptide) with ethyl chloroacetate in DMF,[2] or by the esterification of acid with alcohol using concentrated H2SO4 as catalyst.[3] In this paper, synthesis of aryloxyacetate and aryl thioacetate from aryloxyacetic acid and arylthioacetic acid respectively in ether catalyzed by silica sulfuric acid in 83%~94% yields is described. The catalyst is reused for 3 times without significant loss of activity (Entry 4). Compared with common procedures, the present procedure possesses the advantages of the operational simplicity, short reaction time,less-corrosion, high yield and reusable catalyst.

  8. Acid base catalyzed transesterification kinetics of waste cooking oil

    Energy Technology Data Exchange (ETDEWEB)

    Jain, Siddharth; Sharma, M.P.; Rajvanshi, Shalini [Alternate Hydro Energy Centre, Indian Institute of Technology, Roorkee (India)

    2011-01-15

    The present study reports the results of kinetics study of acid base catalyzed two step transesterification process of waste cooking oil, carried out at pre-determined optimum temperature of 65 C and 50 C for esterification and transesterification process respectively under the optimum condition of methanol to oil ratio of 3:7 (v/v), catalyst concentration 1%(w/w) for H{sub 2}SO{sub 4} and NaOH and 400 rpm of stirring. The optimum temperature was determined based on the yield of ME at different temperature. Simply, the optimum concentration of H{sub 2}SO{sub 4} and NaOH was determined with respect to ME Yield. The results indicated that both esterification and transesterification reaction are of first order rate reaction with reaction rate constant of 0.0031 min{sup -1} and 0.0078 min{sup -1} respectively showing that the former is a slower process than the later. The maximum yield of 21.50% of ME during esterification and 90.6% from transesterification of pretreated WCO has been obtained. This is the first study of its kind which deals with simplified kinetics of two step acid-base catalyzed transesterification process carried under the above optimum conditions and took about 6 h for complete conversion of TG to ME with least amount of activation energy. Also various parameters related to experiments are optimized with respect to ME yield. (author)

  9. Cycloadditions for Studying Nucleic Acids.

    Science.gov (United States)

    Kath-Schorr, Stephanie

    2016-02-01

    Cycloaddition reactions for site-specific or global modification of nucleic acids have enabled the preparation of a plethora of previously inaccessible DNA and RNA constructs for structural and functional studies on naturally occurring nucleic acids, the assembly of nucleic acid nanostructures, therapeutic applications, and recently, the development of novel aptamers. In this chapter, recent progress in nucleic acid functionalization via a range of different cycloaddition (click) chemistries is presented. At first, cycloaddition/click chemistries already used for modifying nucleic acids are summarized, ranging from the well-established copper(I)-catalyzed alkyne-azide cycloaddition reaction to copper free methods, such as the strain-promoted azide-alkyne cycloaddition, tetrazole-based photoclick chemistry and the inverse electron demand Diels-Alder cycloaddition reaction between strained alkenes and tetrazine derivatives. The subsequent sections contain selected applications of nucleic acid functionalization via click chemistry; in particular, site-specific enzymatic labeling in vitro, either via DNA and RNA recognizing enzymes or by introducing unnatural base pairs modified for click reactions. Further sections report recent progress in metabolic labeling and fluorescent detection of DNA and RNA synthesis in vivo, click nucleic acid ligation, click chemistry in nanostructure assembly and click-SELEX as a novel method for the selection of aptamers. PMID:27572987

  10. Acid-Catalyzed Preparation of Biodiesel from Waste Vegetable Oil: An Experiment for the Undergraduate Organic Chemistry Laboratory

    Science.gov (United States)

    Bladt, Don; Murray, Steve; Gitch, Brittany; Trout, Haylee; Liberko, Charles

    2011-01-01

    This undergraduate organic laboratory exercise involves the sulfuric acid-catalyzed conversion of waste vegetable oil into biodiesel. The acid-catalyzed method, although inherently slower than the base-catalyzed methods, does not suffer from the loss of product or the creation of emulsion producing soap that plagues the base-catalyzed methods when…

  11. MOLYBDENUM CATALYZED ACID PEROXIDE BLEACHING OF EUCALYPTUS KRAFT PULP

    Directory of Open Access Journals (Sweden)

    Marcos S. Rabelo

    2008-08-01

    Full Text Available Molybdenum catalyzed peroxide bleaching (PMo Stage consists of pulp treatment with hydrogen peroxide under acidic conditions in the presence of a molybdenum catalyst. Molybdenum is applied in catalytic doses (50-200 mg/kg pulp and may originate from various sources, including (NH46Mo7O24.4H2O, Na2MoO4.2H2O, siliconmolybdate, etc. This work is aimed at optimizing the PMo stage and evaluating its industrial application in the OAZDP sequence. Optimum PMo stage conditions for bleaching eucalyptus pulp were 90 ºC, pH 3.5, 2 h, 0.1 kg/adt Mo and 5 kg/adt H2O2. The PMo stage was more efficient to remove pulp hexenuronic acids than lignin. Its efficiency decreased with increasing pH in the range of 1.5-5.5, while it increased with increasing temperature and peroxide and molybdenum doses. The application of the PMo stage as replacement for the A-stage of the AZDP sequence significantly decreased chlorine dioxide demand. The PMo stage caused a decrease of 20-30% in the generation of organically bound chlorine. The quality parameters of the pulp produced during the PMo stage mill trial were comparable to those obtained with the reference A-stage.

  12. Biodiesel Production from Spent Fish Frying Oil Through Acid-Base Catalyzed Transesterification

    OpenAIRE

    Abdalrahman B. Fadhil; Mohammed M. Dheyab; Kareem M. Ahmed; Marwa H. Yahya

    2012-01-01

    Biodiesel fuels were prepared from a special type of frying oil namely spent fish frying oil through two step transesterification viz. acid-base catalyzed transesterification. Hydrochloric acid and potassium hydroxide with methanol were used for this purpose. The oil was pre-treated with (1.0 wt% HCl) and methanol to reduce free fatty acids content of the oil. Then, conditions of the base catalyzed step such as base concentration, reaction temperature, methanol to oil molar ratio and reaction...

  13. Acid-catalyzed reactions of hexanal on sulfuric acid particles: Identification of reaction products

    Science.gov (United States)

    Garland, Rebecca M.; Elrod, Matthew J.; Kincaid, Kristi; Beaver, Melinda R.; Jimenez, Jose L.; Tolbert, Margaret A.

    While it is well established that organics compose a large fraction of the atmospheric aerosol mass, the mechanisms through which organics are incorporated into atmospheric aerosols are not well understood. Acid-catalyzed reactions of compounds with carbonyl groups have recently been suggested as important pathways for transfer of volatile organics into acidic aerosols. In the present study, we use the aerodyne aerosol mass spectrometer (AMS) to probe the uptake of gas-phase hexanal into ammonium sulfate and sulfuric acid aerosols. While both deliquesced and dry non-acidic ammonium sulfate aerosols showed no organic uptake, the acidic aerosols took up substantial amounts of organic material when exposed to hexanal vapor. Further, we used 1H-NMR, Fourier transform infrared (FTIR) spectroscopy and GC-MS to identify the products of the acid-catalyzed reaction of hexanal in acidic aerosols. Both aldol condensation and hemiacetal products were identified, with the dominant reaction products dependent upon the initial acid concentration of the aerosol. The aldol condensation product was formed only at initial concentrations of 75-96 wt% sulfuric acid in water. The hemiacetal was produced at all sulfuric acid concentrations studied, 30-96 wt% sulfuric acid in water. Aerosols up to 88.4 wt% organic/11.1 wt% H 2SO 4/0.5 wt% water were produced via these two dimerization reaction pathways. The UV-VIS spectrum of the isolated aldol condensation product, 2-butyl 2-octenal, extends into the visible region, suggesting these reactions may impact aerosol optical properties as well as aerosol composition. In contrast to previous suggestions, no polymerization of hexanal or its products was observed at any sulfuric acid concentration studied, from 30 to 96 wt% in water.

  14. Integrated Production of Xylonic Acid and Bioethanol from Acid-Catalyzed Steam-Exploded Corn Stover.

    Science.gov (United States)

    Zhu, Junjun; Rong, Yayun; Yang, Jinlong; Zhou, Xin; Xu, Yong; Zhang, Lingling; Chen, Jiahui; Yong, Qiang; Yu, Shiyuan

    2015-07-01

    High-efficiency xylose utilization is one of the restrictive factors of bioethanol industrialization. However, xylonic acid (XA) as a new bio-based platform chemical can be produced by oxidation of xylose with microbial. So, an applicable technology of XA bioconversion was integrated into the process of bioethanol production. After corn stover was pretreated with acid-catalyzed steam-explosion, solid and liquid fractions were obtained. The liquid fraction, also named as acid-catalyzed steam-exploded corn stover (ASC) prehydrolyzate (mainly containing xylose), was catalyzed with Gluconobacter oxydans NL71 to prepare XA. After 72 h of bioconversion of concentrated ASC prehydrolyzate (containing 55.0 g/L of xylose), the XA concentration reached a peak value of 54.97 g/L, the sugar utilization ratio and XA yield were 94.08 and 95.45 %, respectively. The solid fraction was hydrolyzed to produce glucose with cellulase and then fermented with Saccharomyces cerevisiae NL22 to produce ethanol. After 18 h of fermentation of concentrated enzymatic hydrolyzate (containing 86.22 g/L of glucose), the ethanol concentration reached its highest value of 41.48 g/L, the sugar utilization ratio and ethanol yield were 98.72 and 95.25 %, respectively. The mass balance showed that 1 t ethanol and 1.3 t XA were produced from 7.8 t oven dry corn stover.

  15. Solid Acid-Catalyzed Cellulose Hydrolysis Monitored by In Situ ATR-IR Spectroscopy

    NARCIS (Netherlands)

    Zakzeski, J.; Grisel, R.J.H.; Smit, A.T.; Weckhuysen, B.M.

    2012-01-01

    The solid acid-catalyzed hydrolysis of cellulose was studied under elevated temperatures and autogenous pressures using in situ ATR-IR spectroscopy. Standards of cellulose and pure reaction products, which include glucose, fructose, hydroxymethylfurfural (HMF), levulinic acid (LA), formic acid, and

  16. Selective and recyclable depolymerization of cellulose to levulinic acid catalyzed by acidic ionic liquid.

    Science.gov (United States)

    Ren, Huifang; Girisuta, Buana; Zhou, Yonggui; Liu, Li

    2015-03-01

    Cellulose depolymerization to levulinic acid (LA) was catalyzed by acidic ionic liquids (ILs) selectively and recyclably under hydrothermal conditions. The effects of reaction temperature, time, water amount and cellulose intake were investigated. Dilution effect becomes more pronounced at lower cellulose intake, dramatically improving the yield of LA to 86.1%. A kinetic model has been developed based on experimental data, whereby a good fit was obtained and kinetic parameters were derived. The relationships between IL structure, polymeric structure and depolymerization efficiency were established, shedding light on the in-depth catalytic mechanism of IL, inclusive of acidity and hydrogen bonding ability. The LA product can be readily separated through extraction by methyl isobutyl ketone (MIBK) and IL can be reused over five cycles without loss of activity. This environmentally friendly methodology can be applied to selective production of LA from versatile biomass feedstocks, including cellulose and derivatives, glucose, fructose and HMF.

  17. Degradation of acid red 14 by silver ion-catalyzed peroxydisulfate oxidation in an aqueous solution

    OpenAIRE

    RASOULIFARD, Mohammad Hossein; MOHAMMADI, Seied Mohammad Mahdi DOUST

    2012-01-01

    Silver ion (Ag1+)-catalyzed peroxydisulfate was studied for the degradation of acid red 14 (AR-14) in an aqueous medium. The effect of different parameters, such as temperature, peroxydisulfate concentration, and dye and Ag1+ concentrations, were investigated. Application of Ag1+-catalyzed peroxydisulfate, as an advanced oxidation process, introduces an effectual method for wastewater treatment. An accelerated reaction using S2O82- to destroy dyes can be achieved via chemical activat...

  18. Brønsted Acid-Catalyzed Direct Substitution of 2-Ethoxytetrahydrofuran with Trifluoroborate Salts

    Directory of Open Access Journals (Sweden)

    Kayla M. Fisher

    2016-06-01

    Full Text Available Metal-free transformations of organotrifluoroborates are advantageous since they avoid the use of frequently expensive and sensitive transition metals. Lewis acid-catalyzed reactions involving potassium trifluoroborate salts have emerged as an alternative to metal-catalyzed protocols. However, the drawbacks to these methods are that they rely on the generation of unstable boron dihalide species, thereby resulting in low functional group tolerance. Recently, we discovered that in the presence of a Brønsted acid, trifluoroborate salts react rapidly with in situ generated oxocarbenium ions. Here, we report Brønsted acid-catalyzed direct substitution of 2-ethoxytetrahydrofuran using potassium trifluoroborate salts. The reaction occurs when tetrafluoroboric acid is used as a catalyst to afford functionalized furans in moderate to excellent yields. A variety of alkenyl- and alkynyltrifluoroborate salts readily participate in this transformation.

  19. Synthesis of Tetrahydrofuran and Tetrahydropyran Derivatives Catalyzed by Tungstophosphoric Acid in Ionic Liquid

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Synthesis of tetrahydrofuran and tetrahydropyran derivatives catalyzed by tungstophosphoric acid (H3PW12O4o) were conveniently performed with high yield from the corresponding unsaturated alcohols in ionic liquid. Sufuric acid (H2SO4), trifluoromathanesulfonic acid (TfOH)and p-toluenesulfonic acid (TsOH) were also explored for preparing these products in ionic liquid.The catalysts and ionic liquid can be easily recovered and reused.

  20. GSTP1-1 stereospecifically catalyzes glutathione conjugation of ethacrynic acid

    NARCIS (Netherlands)

    Iersel, M.L.P.S. van; Lipzig, M.M.H. van; Rietjens, I.M.C.M.; Vervoort, J.; Bladeren, P.J. van

    1998-01-01

    Using 1H NMR two diastereoisomers of the ethacrynic acid glutathione conjugate (EASG) as well as ethacrynic acid (EA) could be distinguished and quantified individually. Chemically prepared EASG consists of equal amounts of both diastereoisomers. GSTP1-1 stereospecifically catalyzes formation of one

  1. Fe-Catalyzed Oxidative Cleavage of Unsaturated Fatty Acids

    OpenAIRE

    Spannring, P.

    2013-01-01

    The oxidative cleavage of unsaturated fatty acids into aldehydes or carboxylic acids gives access to valuable products. The products can be used as chemical building blocks, as emulsifiers or in the paint or polymer industry. Ozonolysis is applied industrially to cleave the fatty acid oleic acid into the aldehydes nonanal and 9-oxo-nonanoic acid or into pelargonic and azelaic acid. Considerable hazards, including explosion risks, are associated with the use of ozone, and alternative processes...

  2. Fe-Catalyzed Oxidative Cleavage of Unsaturated Fatty Acids

    NARCIS (Netherlands)

    Spannring, P.

    2013-01-01

    The oxidative cleavage of unsaturated fatty acids into aldehydes or carboxylic acids gives access to valuable products. The products can be used as chemical building blocks, as emulsifiers or in the paint or polymer industry. Ozonolysis is applied industrially to cleave the fatty acid oleic acid int

  3. Kinetics of Ethyl Acetate Synthesis Catalyzed by Acidic Resins

    Science.gov (United States)

    Antunes, Bruno M.; Cardoso, Simao P.; Silva, Carlos M.; Portugal, Ines

    2011-01-01

    A low-cost experiment to carry out the second-order reversible reaction of acetic acid esterification with ethanol to produce ethyl acetate is presented to illustrate concepts of kinetics and reactor modeling. The reaction is performed in a batch reactor, and the acetic acid concentration is measured by acid-base titration versus time. The…

  4. Modification of oligo-Ricinoleic Acid and Its Derivatives with 10-Undecenoic Acid via Lipase-Catalyzed Esterification

    Directory of Open Access Journals (Sweden)

    M. Claudia Montiel

    2012-04-01

    Full Text Available Lipases were employed under solvent-free conditions to conjugate oligo-ricinoleic acid derivatives with 10-undecenoic acid, to incorporate a reactive terminal double bond into the resultant product. First, undecenoic acid was covalently attached to oligo-ricinoleic acid using immobilized Candida antarctica lipase (CAL at a 30% yield. Thirty percent conversion also occurred for CAL-catalyzed esterification between undecenoic acid and biocatalytically-prepared polyglycerol polyricinoleate (PGPR, with attachment of undecenoic acid occurring primarily at free hydroxyls of the polyglycerol moiety. The synthesis of oligo-ricinoleyl-, undecenoyl- structured triacylglycerols comprised two steps. The first step, the 1,3-selective lipase-catalyzed interesterification of castor oil with undecenoic acid, occurred successfully. The second step, the CAL-catalyzed reaction between ricinoleyl-, undecenoyl structured TAG and ricinoleic acid, yielded approximately 10% of the desired structured triacylglycerols (TAG; however, a significant portion of the ricinoleic acid underwent self-polymerization as a side-reaction. The employment of gel permeation chromatography, normal phase HPLC, NMR, and acid value measurements was effective for characterizing the reaction pathways and products that formed.

  5. Enantioselective BINOL-phosphoric acid catalyzed Pictet-Spengler reactions of N-benzyltryptamine

    NARCIS (Netherlands)

    N.V. Sewgobind; M.J. Wanner; S. Ingemann; R. de Gelder; J.H. van Maarseveen; H. Hiemstra

    2008-01-01

    Optically active tetrahydro-beta-carbolines were synthesized via an (R)-BINOL-phosphoric acid-catalyzed asynunetric Pictet-Spengler reaction of N-benzyltryptamine with a series of aromatic and aliphatic aldehydes. The tetrahydro-beta-carbolines were obtained in yields ranging from 77% to 97% and wit

  6. Iron-Catalyzed Acylation of Polyfunctionalized Aryl- and Benzylzinc Halides with Acid Chlorides.

    Science.gov (United States)

    Benischke, Andreas D; Leroux, Marcel; Knoll, Irina; Knochel, Paul

    2016-08-01

    FeCl2 (5 mol %) catalyzes a smooth and convenient acylation of functionalized arylzinc halides at 50 °C (2-4 h) and benzylic zinc chlorides at 25 °C (0.5-4 h) with a variety of acid chlorides leading to polyfunctionalized diaryl and aryl heteroaryl ketones. PMID:27457108

  7. Palladium-catalyzed homo-coupling of boronic acids with supported reagents in supercritical carbon dioxide

    Institute of Scientific and Technical Information of China (English)

    Lei Zhou; Qiu Xiang Xu; Huan Feng Jiang

    2007-01-01

    Palladium-catalyzed homo-coupling of arylboronic acids could proceed smoothly with a commercially available resin functionlised by phosphino or amino group as the ligand in supercritical carbon dioxide thereby offering a simple and efficient protocol for the synthesis of symmetrical bi-aryl molecules and their higher homologues.

  8. Monitoring the Hydrolysis of Olive Oil Catalyzed by Lipase via Acid Value Detection

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Hydrolysis of olive oil catalyzed by Candida lipolytica lipase was investigated. The relative concentration of the components in the product was determined by using high performance liquid chromatography(HPLC). Furthermore, a novel rapid method to detect the hydrolytic process of olive oil was developed based on the relationship between the acid value and the relative concentration of the different components.

  9. Furfural production from fruit shells by acid-catalyzed hydrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Demirbas, A. [Selcuk Univ., Konya (Turkey). Dept. of Chemical Engineering

    2006-01-21

    Pentosans are hydrolyzed to pentoses by dilute mineral acid hydrolysis. The main source of pentosans is hemicelluloses. Furfural can be produced by the acid hydrolysis of pentosan from fruit shells such as hazelnut, sunflower, walnut, and almond of agricultural wastes. Further dehydration reactions of the pentoses yield furfural. The hydrolysis of each shell sample was carried out in dilute sulfuric acid (0.05 to 0.200 mol/l), at high temperature (450-525 K), and short reaction times (from 30 to 600 s). (author)

  10. Palladium-Catalyzed C–C Bond Formations via Activation of Carboxylic Acids and Their Derivatives

    OpenAIRE

    Song, Bingrui

    2013-01-01

    Applications of carboxylic acids and their derivatives in transition metal-catalyzed cross-coupling reactions regio-selectively forming Csp3-Csp2, and Csp2-Csp2 bonds were explored in this thesis. Several important organic building blocks such as aryl acetates, diaryl acetates, imines, ketones, biaryls, styrenes and polysubstituted alkenes were successfully accessed from carboxylic acids and their derivatives by the means of C–H activation and decarboxylative cross-couplings. An efficient ...

  11. On the Brønsted acid-catalyzed homogeneous hydrolysis of furans.

    Science.gov (United States)

    Nikbin, Nima; Caratzoulas, Stavros; Vlachos, Dionisios G

    2013-11-01

    Furan affairs: Electronic structure calculations of the homogeneous Brønsted acid-catalyzed hydrolysis of 2,5-dimethylfuran show that proton transfer to the β-position is rate-limiting and provides support that the hydrolysis follows general acid catalysis. By means of projected Fukui indices, we show this to be the case for unsubstituted, 2-, and 2,5-substituted furans with electron-donating groups.

  12. Copper-catalyzed intermolecular oxyamination of olefins using carboxylic acids and O-benzoylhydroxylamines

    Directory of Open Access Journals (Sweden)

    Brett N. Hemric

    2016-01-01

    Full Text Available This paper reports a novel approach for the direct and facile synthesis of 1,2-oxyamino moieties via an intermolecular copper-catalyzed oxyamination of olefins. This strategy utilizes O-benzoylhydroxylamines as an electrophilic amine source and carboxylic acids as a nucleophilic oxygen source to achieve a modular difunctionalization of olefins. The reaction proceeded in a regioselective manner with moderate to good yields, exhibiting a broad scope of carboxylic acid, amine, and olefin substrates.

  13. Tandem Aldol Condensation – Platinacycle-Catalyzed Addition Reactions of Aldehydes, Methyl Ketones and Arylboronic Acids

    OpenAIRE

    Liao, Yuan-Xi; Hu, Qiao-Sheng

    2012-01-01

    Tandem aldol condensation of aldehydes with methyl ketones followed by anionic four-electron donor-based (Type I) platinacycle-catalyzed addition reactions of arylboronic acids to form β-arylated ketones is described. Good to excellent yields of β-arylated ketones were obtained for the tandem reactions of aromatic/aliphatic aldehydes, methyl ketones and arylboronic acids, and moderate yields were observed for the tandem reaction with α, β-unsaturated aldehydes as the aldehyde source.

  14. Cu2+-Catalyzed Oscillatory Oxidation of Ascorbic Acid by O2 Flow

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A novel heterogeneous oscillator, the Cu2+-catalyzed oscillatory oxidation of ascorbic acid (Vitamin C) in aqueous solution by O2 flow was reported. Both the potential oscillations on Pt-electrode corresponding to [Cu2+] and the absorbance oscillations at l=260 nm corresponding to [ascorbic acid] were observed. Oscillations in the completely homogeneous system were also observed. Effects of several factors on the oscillations were investigated.

  15. Investigation of emulsified, acid and acid-alkali catalyzed mesoporous bioactive glass microspheres for bone regeneration and drug delivery

    International Nuclear Information System (INIS)

    Acid-catalyzed mesoporous bioactive glass microspheres (MBGMs-A) and acid-alkali co-catalyzed mesoporous bioactive glass microspheres (MBGMs-B) were successfully synthesized via combination of sol-gel and water-in-oil (W/O) micro-emulsion methods. The structural, morphological and textural properties of mesoporous bioactive glass microspheres (MBGMs) were characterized by various techniques. Results show that both MBGMs-A and MBGMs-B exhibit regularly spherical shape but with different internal porous structures, i.e., a dense microstructure for MBGMs-A and internally porous structure for MBGMs-B. 29Si NMR data reveal that MGBMs have low polymerization degree of silica network. The in vitro bioactivity tests indicate that the apatite formation rate of MBGMs-B was faster than that of MBGMs-A after soaking in simulated body fluid (SBF) solution. Furthermore, the two kinds of MBGMs have similar storage capacity of alendronate (AL), and the release behaviors of AL could be controlled due to their unique porous structure. In conclusion, the microspheres are shown to be promising candidates as bone-related drug carriers and filling materials of composite scaffold for bone repair. - Graphical abstract: The morphologies and microstructures of acid-catalyzed mesoporous bioactive glass microspheres (MBGMs-A) and acid-alkali co-catalyzed mesoporous bioactive glass microspheres (MBGMs-B) were observed by scanning electron microscope and transmission electron microscope. MBGMs-A exhibits a dense structure and a porous can be observed in MBGMs-B. The microspheres have a quick inducing-apatite formation ability and show a sustained release of alendronate (AL). Highlights: • A rapid method was reported to prepare mesoporous bioactive glass microspheres. • The addition of ammonia significantly shortens the preparation time. • Acid and acid-alkali co-catalyzed microspheres were studied for the first time. • The materials exhibited excellent in vitro bioactivity and drug

  16. Lewis Acid Catalyzed Selective Reactions of Donor-Acceptor Cyclopropanes with 2-Naphthols.

    Science.gov (United States)

    Kaicharla, Trinadh; Roy, Tony; Thangaraj, Manikandan; Gonnade, Rajesh G; Biju, Akkattu T

    2016-08-16

    Lewis acid-catalyzed reactions of 2-substituted cyclopropane 1,1-dicarboxylates with 2-naphthols is reported. The reaction exhibits tunable selectivity depending on the nature of Lewis acid employed and proceed as a dearomatization/rearomatization sequence. With Bi(OTf)3 as the Lewis acid, a highly selective dehydrative [3+2] cyclopentannulation takes place leading to the formation of naphthalene-fused cyclopentanes. Interestingly, engaging Sc(OTf)3 as the Lewis acid, a Friedel-Crafts-type addition of 2-naphthols to cyclopropanes takes place, thus affording functionalized 2-naphthols. Both reactions furnished the target products in high regioselectivity and moderate to high yields. PMID:27391792

  17. Synthesis of pteroylglutamic acid-3',5'-2H2 by trifluoroacetic acid catalyzed exchange with deuterium oxide

    International Nuclear Information System (INIS)

    Pteroylglutamic acid (PGA) was deuterated by trifluoroacetic acid catalyzed exchange with deuterium oxide. The product, pteroylglutamic acid-3',5'-2H2, was specifically deuterated in the aromatic protons of the p-aminobenzoyl (PABA) moiety; the protons on C7 and C9 and in the glutamic acid residue were not exchanged. Deuterium incorporation was measured by chemical ionization mass spectrometry (CI-MS). Pteroylglutamates were cleaved by a base-catalyzed, oxidative hydrolysis to PABA, which was converted to the methyl ester, N-trifluoroacetate for analysis by gas chromatography-chemical ionization-mass spectrometry. Products from the exchange typically contained 1 percent 2H1 and 90 percent 2H2 species. The procedure may be used to label specifically various analogs of PGA with deuterium in the PABA portion of the molecule

  18. Choline Chloride Catalyzed Amidation of Fatty Acid Ester to Monoethanolamide: A Green Approach.

    Science.gov (United States)

    Patil, Pramod; Pratap, Amit

    2016-01-01

    Choline chloride catalyzed efficient method for amidation of fatty acid methyl ester to monoethanolamide respectively. This is a solvent free, ecofriendly, 100% chemo selective and economically viable path for alkanolamide synthesis. The Kinetics of amidation of methyl ester were studied and found to be first order with respect to the concentration of ethanolamine. The activation energy (Ea) for the amidation of lauric acid methyl ester catalyzed by choline chloride was found to be 50.20 KJ mol(-1). The 98% conversion of lauric acid monoethanolamide was obtained at 110°C in 1 h with 6% weight of catalyst and 1:1.5 molar ratio of methyl ester to ethanolamine under nitrogen atmosphere. PMID:26666271

  19. Heteropoly acid catalyzed hydrolysis of glycogen to glucose

    International Nuclear Information System (INIS)

    Complete conversion of glycogen to glucose is achieved by using H3PW12O40·nH2O (HPW) and H4SiW12O40·nH2O (HSiW) as catalysts for the hydrolysis under optimized hydrothermal conditions (mass fraction of catalyst 2.4%, 373 K and 2 h reaction time). The reusability of the catalyst (HPW) was demonstrated. In addition to carrying out the glycogen hydrolysis in an autoclave, other novel methods such as microwave irradiation and sonication have also been investigated. At higher mass fraction of the heteropoly acids (10.5%), glycogen could be completely converted to glucose under microwave irradiation. Sonication of an aqueous solution of glycogen in the presence of HPW and HSiW also yielded glucose. Thus, heteropoly acids are efficient, environmentally friendly and reusable catalysts for the conversion of glycogen to glucose. - Highlights: • Hydrothermal, microwave and sonication based methods of hydrolysis. • Heteropoly acids are green catalysts for glycogen hydrolysis. • Glycogen from cyanobacteria is demonstrated as a potential feedstock for glucose

  20. Development of Fluorous Lewis Acid-Catalyzed Reactions

    Directory of Open Access Journals (Sweden)

    Joji Nishikido

    2006-08-01

    Full Text Available Organic synthetic methodology in the 21st century aims to conform to the principles of green sustainable chemistry (GSC and we may expect that in the future, the realization of GSC will be an important objective for chemical industries. An important aim of synthetic organic chemistry is to implement waste-free and environmentally-benign industrial processes using Lewis acids as versatile as aluminum choride. A key technological objective of our work in this area has been to achieve a “catalyst recycling system that utilizes the high activity and structural features of fluorous Lewis acid catalysts”. Thus, we have developed a series of novel fluorous Lewis acid catalysts, namely the ytterbium(III, scandium(III, tin(IV or hafnium(IV bis(perfluoroalkanesulfonylamides or tris(perfluoro- alkanesulfonylmethides. Our catalysts are recyclable and effective for acylations of alcohols and aromatics, Baeyer-Villiger reactions, direct esterifications and transesterifications in a fluorous biphasic system (FBS, in supercritical carbon dioxide and on fluorous silica gel supports.

  1. Palladium-Catalyzed α-Arylation of Aryl Acetic Acid Derivatives via Dienolate Intermediates with Aryl Chlorides and Bromides

    OpenAIRE

    Sha, Sheng-Chun; Zhang, Jiadi; Walsh, Patrick J.

    2015-01-01

    To date, examples of α-arylation of carboxylic acids remain scarce. Using a deprotonative cross-coupling process (DCCP), a method for palladium-catalyzed γ-arylation of aryl acetic acids with aryl halides has been developed. This protocol is applicable to a wide range of aryl bromides and chlorides. A procedure for the palladium-catalyzed α-arylation of styryl acetic acids is also described.

  2. Development of Fluorous Lewis Acid-Catalyzed Reactions

    OpenAIRE

    Joji Nishikido; Osamu Yamazaki; Xiuhua Hao; Akihiro Yoshida

    2006-01-01

    Organic synthetic methodology in the 21st century aims to conform to the principles of green sustainable chemistry (GSC) and we may expect that in the future, the realization of GSC will be an important objective for chemical industries. An important aim of synthetic organic chemistry is to implement waste-free and environmentally-benign industrial processes using Lewis acids as versatile as aluminum choride. A key technological objective of our work in this area has been to achieve a “c...

  3. Kinetics of acid-catalyzed aldol condensation reactions of aliphatic aldehydes

    Science.gov (United States)

    Casale, Mia T.; Richman, Aviva R.; Elrod, Matthew J.; Garland, Rebecca M.; Beaver, Melinda R.; Tolbert, Margaret A.

    Field observations of atmospheric aerosols have established that organic compounds compose a large fraction of the atmospheric aerosol mass. However, the physical/chemical pathway by which organic compounds are incorporated into atmospheric aerosols remains unclear. The potential role of acid-catalyzed reactions of organic compounds on acidic aerosols has been explored as a possible chemical pathway for the incorporation of organic material into aerosols. In the present study, ultraviolet-visible (UV-vis) spectroscopy was used to monitor the kinetics of formation of the products of the acid-catalyzed aldol condensation reaction of a range of aliphatic aldehydes (C 2-C 8). The experiments were carried out at various sulfuric acid concentrations and a range of temperatures in order to estimate the rate constants of such reactions on sulfuric acid aerosols under tropospheric conditions. The rate constants were generally found to decrease as the chain length of the aliphatic aldehyde increased (except for acetaldehyde, which had an unusually small rate constant), increase as a function of sulfuric acid concentration as predicted by excess acidity theory, and showed normal Arrhenius behavior as a function of temperature. While the kinetic data are generally consistent with previous laboratory reports of aldehyde reactivity in various sulfuric acid media, the aldol condensation reactions involving aliphatic aldehydes do not appear fast enough to be responsible for significant transfer of organic material into atmospheric aerosols.

  4. Kinetics of the Esterification Reaction between Pentanoic Acid and Methanol Catalyzed by Noncorrosive Cation Exchange Resin

    OpenAIRE

    Sharma, M.; Toor, A. P.; R. K. Wanchoo

    2014-01-01

    Methyl pentanoate, commonly known as methyl valerate, is the methyl ester of pentanoic acid (valeric acid) with a fruity odour. Methyl pentanoate is commonly used in fragrances, beauty care, soap, laundry detergents at levels of 0.1 – 1 %. In its very pure form (purity 99.5 %) it is used as a plasticizer in the manufacture of plastics. In the present investigation, kinetics of esterification of pentanoic acid with methanol catalyzed by heterogeneous catalyst in a batch-type reactor is reporte...

  5. Acid-Catalyzed Oxygen-18 Labeling of Peptides for Proteomics Applications

    OpenAIRE

    Niles, Richard; Witkowska, H. Ewa; Allen, Simon; Hall, Steven C.; Fisher, Susan J.; Hardt, Markus

    2009-01-01

    In enzymatic 18O-labeling strategies for quantitative proteomics, the exchange of carboxyl oxygens at low pH is a common, undesired side reaction. We asked if acid-catalyzed back exchange could interfere with quantitation and whether the reaction itself could be used as an alternative method for introducing 18O label into peptides. Several synthetic amino acid sequences were dissolved in dilute acid containing 50% (v/v) H218O and incubated at room temperature. Aliquots were removed over a per...

  6. Nickel-Catalyzed Cross-Coupling of Redox-Active Esters with Boronic Acids.

    Science.gov (United States)

    Wang, Jie; Qin, Tian; Chen, Tie-Gen; Wimmer, Laurin; Edwards, Jacob T; Cornella, Josep; Vokits, Benjamin; Shaw, Scott A; Baran, Phil S

    2016-08-01

    A transformation analogous in simplicity and functional group tolerance to the venerable Suzuki cross-coupling between alkyl-carboxylic acids and boronic acids is described. This Ni-catalyzed reaction relies upon the activation of alkyl carboxylic acids as their redox-active ester derivatives, specifically N-hydroxy-tetrachlorophthalimide (TCNHPI), and proceeds in a practical and scalable fashion. The inexpensive nature of the reaction components (NiCl2 ⋅6 H2 O-$9.5 mol(-1) , Et3 N) coupled to the virtually unlimited commercial catalog of available starting materials bodes well for its rapid adoption. PMID:27380912

  7. Organosolv liquefaction of sugarcane bagasse catalyzed by acidic ionic liquids.

    Science.gov (United States)

    Chen, Zhengjian; Long, Jinxing

    2016-08-01

    An efficient and eco-friendly process is proposed for sugarcane bagasse liquefaction under mild condition using IL catalyst and environmental friendly solvent of ethanol/H2O. The relationship between IL acidic strength and its catalytic performance is investigated. The effects of reaction condition parameters such as catalyst dosage, temperature, time and solvent are also intensively studied. The results show that ethanol/H2O has a significant promotion effect on the simultaneous liquefaction of sugarcane bagasse carbohydrate and lignin. 97.5% of the bagasse can be liquefied with 66.46% of volatile product yield at 200°C for 30min. Furthermore, the IL catalyst shows good recyclability where no significant loss of the catalytic activity is exhibited even after five runs. PMID:27115746

  8. CLAY CATALYZED SYNTHESIS OF BIO-DEGRADABLE POLY(GLYCOLIC ACID)

    Institute of Scientific and Technical Information of China (English)

    K. Durai Murugan; S. Radhika; I. Baskaran; R. Anbarasan

    2008-01-01

    Glycolic acid was polymerized under vacuum in the presence and absence of nano sized clay. The added clay catalyzed the condensation polymerization which can be confirmed by recording FT1R spectroscopy and intrinsic viscosity (Ⅳ) values. The relative intensity of C =O/CH is increased while increasing the amount of clay. DSC showed the appearance of multiple endotherms of poly(glycolic acid). TGA showed the percentage weight residue remain above 750℃ for polymer-nano composite system was 21% and hence proved the flame retardancy (char forming) nature. TEM confirmed the nano size of the clay used to catalyze the condensation reaction. The intrinsic viscosity value was increased with the increase of percentage weight of Hectorite type clay.

  9. Contribution to the study of the oxidation reaction of Np(V) by nitric acid catalyzed par nitrous acid

    International Nuclear Information System (INIS)

    The oxidation reaction kinetics of Np(V) to Np(VI) by nitric acid catalyzed by nitrous acid was studied. In a first part, a detailed bibliographical survey was made of the oxidation-reduction reactions of U, Np, Pu, Am with nitrous and nitric acids (51 references). It is shown that only when both the organic and aqueous phases are mixed up, the extraction of a reaction product (NpVI) induces an equilibrium displacement. TBP was used as solvent. It is shown that the extraction of nitrous acid from the solvent enables the nitrous acid concentration to be kept constant and in the same order of magnitude than that of Np. This enables to show that Np(V) and nitrous acid have no simple orders. The temperature and nitric acid concentration dependence was studied. It is shown that tetravalent nitrogen must play a major part in the Np(V) oxidation

  10. Stereoselectivities in α- and β-Amino Acids Catalyzed Mannich Reactions Involving Cyclohexanone

    Institute of Scientific and Technical Information of China (English)

    WANG Ying; FU Ai-ping; LI Hong-liang; TIAN Feng-hui; YUAN Shu-ping; SI Hong-zong; DUAN Yun-bo; WANG Zong-hua

    2011-01-01

    The effects of two different amino acid catalysts on the stereoselectivities in the direct Mannich reactions of cyclohexanone,p-anisidine and p-nitrobenzaldehyde were studied with the aid of density functional theory.Transition states of the stereo-determining C-C bond-forming step with the addition of enamine intermediate to the imine for the L-proline(α-amino acid) and (R)-3-pyrrolidinecarboxylic acid(β-amino acid)-catalyzed processes were reported.B3LYP/6-31G** calculations provide a good explanation for the opposite syn vs.anti diastereoselectivities of these two different kinds of catalysts(syn-selectivity for the α-amino acid catalysts,anti-selectivity for the β-amino acid catalysts).Calculated and observed diastereomeric ratio and enantiomeric excess values are in reasonable agreement.

  11. Origins of Stereoselectivities in Chiral Phosphoric Acid-Catalyzed Allylborations and Propargylations of Aldehydes

    OpenAIRE

    Wang, Hao; Jain, Pankaj; Antilla, Jon C.; Houk, K. N.

    2013-01-01

    The chiral BINOL-phosphoric acid catalyzed allylboration and propargylation reactions are studied with density functional theory (B3LYP and B3LYP-D3). Two different models were recently proposed for these reactions by Goodman and our group, respectively. In Goodman's model for allylborations, the catalyst interacts with the boronate pseudo-axial oxygen. By contrast, our model for propargylations predicts that the catalyst interacts with the boronate pseudo-equatorial oxygen. In both models, t...

  12. Enantioselective aldol reaction between isatins and cyclohexanone catalyzed by amino acid sulphonamides.

    Science.gov (United States)

    Wang, Jun; Liu, Qi; Hao, Qing; Sun, Yanhua; Luo, Yiming; Yang, Hua

    2015-04-01

    Sulphonamides derived from primary α-amino acid were successfully applied to catalyze the aldol reaction between isatin and cyclohexanone under neat conditions. More interestingly, molecular sieves, as privileged additives, were found to play a vital role in achieving high enantioselectivity. Consequently, high yields (up to 99%) along with good enantioselectivities (up to 92% ee) and diastereoselectivities (up to 95:5 dr) were obtained. In addition, this reaction was also conveniently scaled up, demonstrating the applicability of this protocol.

  13. Keto-Enol Tautomerizations Catalyzed by Water and Carboxylic Acids

    Science.gov (United States)

    da Silva, G.

    2009-12-01

    The ability of weakly-bound complexes to influence the kinetics of gas phase reactions, particularly in atmospheric chemistry, has long been speculated. This study uses quantum chemistry and statistical reaction rate theory to identify that bound water molecules can significantly reduce barriers to intramolecular hydrogen shift reactions, via a double-hydrogen-shift mechanism. The bound water molecule directly participates in the hydrogen shift reaction, exchanging a H atom with its counterpart. For the vinyl alcohol to acetaldehyde keto-enol tautomerization this mechanism cuts the reaction barrier approximately in half, reducing it by over 30 kcal mol-1. In contrast, while a non-participatory ‘bystander’ water molecule also reduces the hydrogen shift barrier, it is only by around 3 kcal/mol. When a carboxylic acid replaces water in the double-hydrogen-shift mechanism the barrier to keto-enol tautomerization is decimated, reduced to less than 6 kcal/mol (around 15 kcal/mol in the reverse direction). This results from reduced strain in the hydrogen shift transition state, and achieves enol lifetimes in the troposphere that become short on relevant timescales. Rapid enol to ketone isomerizations are currently required to explain the oxidation products of isoprene. The wider significance of rapid hydrogen shift reactions in atmospherically relevant molecules and radicals is also explored.

  14. Acetic acid-catalyzed formation of N-phenylphthalimide from phthalanilic acid: a computational study of the mechanism.

    Science.gov (United States)

    Takahashi, Ohgi; Kirikoshi, Ryota; Manabe, Noriyoshi

    2015-05-28

    In glacial acetic acid, phthalanilic acid and its monosubstituents are known to be converted to the corresponding phthalimides in relatively good yields. In this study, we computationally investigated the experimentally proposed two-step (addition-elimination or cyclization-dehydration) mechanism at the second-order Møller-Plesset perturbation (MP2) level of theory for the unsubstituted phthalanilic acid, with an explicit acetic acid molecule included in the calculations. In the first step, a gem-diol tetrahedral intermediate is formed by the nucleophilic attack of the amide nitrogen. The second step is dehydration of the intermediate to give N-phenylphthalimide. In agreement with experimental findings, the second step has been shown to be rate-determining. Most importantly, both of the steps are catalyzed by an acetic acid molecule, which acts both as proton donor and acceptor. The present findings, along with those from our previous studies, suggest that acetic acid and other carboxylic acids (in their undissociated forms) can catalyze intramolecular nucleophilic attacks by amide nitrogens and breakdown of the resulting tetrahedral intermediates, acting simultaneously as proton donor and acceptor. In other words, double proton transfers involving a carboxylic acid molecule can be part of an extensive bond reorganization process from cyclic hydrogen-bonded complexes.

  15. Acetic Acid Can Catalyze Succinimide Formation from Aspartic Acid Residues by a Concerted Bond Reorganization Mechanism: A Computational Study

    Directory of Open Access Journals (Sweden)

    Ohgi Takahashi

    2015-01-01

    Full Text Available Succinimide formation from aspartic acid (Asp residues is a concern in the formulation of protein drugs. Based on density functional theory calculations using Ace-Asp-Nme (Ace = acetyl, Nme = NHMe as a model compound, we propose the possibility that acetic acid (AA, which is often used in protein drug formulation for mildly acidic buffer solutions, catalyzes the succinimide formation from Asp residues by acting as a proton-transfer mediator. The proposed mechanism comprises two steps: cyclization (intramolecular addition to form a gem-diol tetrahedral intermediate and dehydration of the intermediate. Both steps are catalyzed by an AA molecule, and the first step was predicted to be rate-determining. The cyclization results from a bond formation between the amide nitrogen on the C-terminal side and the side-chain carboxyl carbon, which is part of an extensive bond reorganization (formation and breaking of single bonds and the interchange of single and double bonds occurring concertedly in a cyclic structure formed by the amide NH bond, the AA molecule and the side-chain C=O group and involving a double proton transfer. The second step also involves an AA-mediated bond reorganization. Carboxylic acids other than AA are also expected to catalyze the succinimide formation by a similar mechanism.

  16. Grape skins (Vitis vinifera L.) catalyze the in vitro enzymatic hydroxylation of p-coumaric acid to caffeic acid

    DEFF Research Database (Denmark)

    Arnous, Anis; Meyer, Anne S.

    2009-01-01

    The ability of grape skins to catalyze in vitro conversion of p-coumaric acid to the more potent antioxidant caffeic acid was studied. Addition of different concentrations of p-coumaric to red grape skins (Cabernet Sauvignon) resulted in formation of caffeic acid. This caffeic acid formation (Y......) correlated positively and linearly to p-coumaric acid consumption (X): Y = 0.5 X + 9.5; R 2 = 0.96, P skin concentrations, indicated that the grape skins harboured an o......-hydroxylation activity, proposedly a monophenol- or a flavonoid 3′-monooxygenase activity (EC 1.14.18.1 or EC 1.14.13.21). The K m of this crude o-hydroxylation activity in the red grape skin was 0.5 mM with p-coumaric acid....

  17. Solid acid-catalyzed depolymerization of barley straw driven by ball milling.

    Science.gov (United States)

    Schneider, Laura; Haverinen, Jasmiina; Jaakkola, Mari; Lassi, Ulla

    2016-04-01

    This study describes a time and energy saving, solvent-free procedure for the conversion of lignocellulosic barley straw into reducing sugars by mechanocatalytical pretreatment. The catalytic conversion efficiency of several solid acids was tested which revealed oxalic acid dihydrate as a potential catalyst with high conversion rate. Samples were mechanically treated by ball milling and subsequently hydrolyzed at different temperatures. The parameters of the mechanical treatment were optimized in order to obtain sufficient amount of total reducing sugar (TRS) which was determined following the DNS assay. Additionally, capillary electrophoresis (CE) and Fourier transform infrared spectrometry (FT-IR) were carried out. Under optimal conditions TRS 42% was released using oxalic acid dihydrate as a catalyst. This study revealed that the acid strength plays an important role in the depolymerization of barley straw and in addition, showed, that the oxalic acid-catalyzed reaction generates low level of the degradation product 5-hydroxymethylfurfural (HMF). PMID:26859328

  18. Preliminary Study on Lipase-catalyzed Synthesis of Polyesters Containing L-Malic Acid Units

    Institute of Scientific and Technical Information of China (English)

    Da Hu YAO; Guang Ji LI

    2006-01-01

    Terpolymer of 1, 8-octanediol, adipic acid, and L-malic acid was synthesized via a lipase-catalyzed direct polycondensation. The products were characterized by GPC and 1H NMR.The results indicated that the molecular weight of the prepared polymers decreased with increasing L-malic acid content in the monomer feed ratio, and that change in the L-malic acid content from 0to 20 mol % did not remarkably influenced on the molecular weight distribution Mw/Mn of the prepared samples. The 1H NMR spectra of the obtained copolymer samples showed that hydroxyl groups of L-malic acid did not take part in the polymerization reaction.

  19. Palladium-catalyzed cross-coupling reactions of aryl boronic acids with aryl halides in water.

    Science.gov (United States)

    Wang, Shaoyan; Zhang, Zhiqiang; Hu, Zhizhi; Wang, Yue; Lei, Peng; Chi, Haijun

    2009-01-01

    An efficient Suzuki cross-coupling reaction using a variety of aryl halides in neat water was developed. The Pd-catalyzed reaction between aryl bromides or chlorides and phenyl boronic acids was compatible with various functional groups and affords biphenyls in good to excellent yields without requirement of organic cosolvents. The air stability and solubility in water of the palladium-phosphinous acid complexes were considered to facilitate operation of the coupling reaction and product isolation. The reaction conditions including Pd catalyst selection, temperature, base and catalyst recoverability were also investigated. PMID:25084408

  20. Silica-supported Copper(Ⅱ) Catalyzed Coupling of Arylboronic Acids with Imidazoles

    Institute of Scientific and Technical Information of China (English)

    ZHANG Li-Yuan; WANG Lei

    2006-01-01

    Immobilized copper(Ⅱ) in organic-inorganic hybrid materials catalyzed Ar-N coupling of arylboronic acids with imidazoles has been developed. Arylboronic acids reacted with imidazoles smoothly in the presence of a 3-(2-aminoethylamino)propyl functionalized silica gel immobilized copper(Ⅱ) catalyst (10 mol%) in methanol without any additives and bases. The reactions generated the corresponding cross-coupling products in good yields.Furthermore, silica-supported copper can be recovered and recycled by a simple filtration procedure and used for five consecutive trials without decreases in activity.

  1. Acid-Catalyzed Oxygen-18 Labeling of Peptides for Proteomics Applications

    Science.gov (United States)

    Niles, Richard; Witkowska, H. Ewa; Allen, Simon; Hall, Steven C.; Fisher, Susan J.; Hardt, Markus

    2010-01-01

    In enzymatic 18O-labeling strategies for quantitative proteomics, the exchange of carboxyl oxygens at low pH is a common, undesired side reaction. We asked if acid-catalyzed back exchange could interfere with quantitation and whether the reaction itself could be used as an alternative method for introducing 18O label into peptides. Several synthetic amino acid sequences were dissolved in dilute acid containing 50% (v/v) H218O and incubated at room temperature. Aliquots were removed over a period of 3 weeks and analyzed by tandem mass spectrometry (MS/MS). 18O-incorporation ratios were determined by linear regression analysis that allowed for multiple stable isotope incorporations. At low pH, peptides exchanged their carboxyl oxygen atoms with the aqueous solvent. The isotope patterns gradually shifted to higher masses until they reached the expected binomial distribution at equilibrium after ~11 days. Reaction rates were residue and sequence specific. Due to its slow nature, the acid-based back exchange is expected to minimally interfere with enzymatic 18O-labeling studies provided that storage and analysis conditions minimize low pH exposure times. On its own, acid-catalyzed 18O labeling is a general tagging strategy that is an alternative to the chemical, metabolic and enzymatic isotope-labeling schemes currently used in quantitative proteomics. PMID:19243188

  2. Base catalyzed transesterification of acid treated vegetable oil blend for biodiesel production

    Energy Technology Data Exchange (ETDEWEB)

    Yusup, Suzana; Khan, Modhar Ali [Chemical Engineering Department, Universiti Teknologi PETRONAS, Seri Iskandar, Tronoh, Perak 31750 (Malaysia)

    2010-10-15

    Biodiesel can be produced from low cost non-edible oils and fats. However, most of these sources are of high free fatty acid content which requires two stage transesterification to reduce the acid value and produce biodiesel. The acid treatment step is usually followed by base transesterification since the latter can yield higher conversions of methyl esters at shorter reaction time when compared with acid catalyzed reaction. In the current study, base transesterification in the second stage of biodiesel synthesis is studied for a blend of crude palm/crude rubber seed oil that had been characterized and treated with acid esterification. Optimum conditions for the reaction were established and effect of each variable was investigated. The base catalyzed transesterification favored a temperature of 55 C with methanol/oil molar ratio of 8/1 and potassium hydroxide at 2% (ww{sup -1}) (oil basis). The conversion of methyl esters exceeded 98% after 5 h and the product quality was verified to match that for biodiesel with international standards. (author)

  3. Formation of linear polyenes in poly(vinyl alcohol) films catalyzed by phosphotungstic acid, aluminum chloride, and hydrochloric acid

    Science.gov (United States)

    Tretinnikov, O. N.; Sushko, N. I.; Malyi, A. B.

    2016-07-01

    Formation of linear polyenes-(CH=CH)n-via acid-catalyzed thermal dehydration of polyvinyl alcohol in 9- to 40-µm-thick films of this polymer containing hydrochloric acid, aluminum chloride, and phosphotungstic acid as dehydration catalysts was studied by electronic absorption spectroscopy. The concentration of long-chain ( n ≥ 8) polyenes in films containing phosphotungstic acid is found to monotonically increase with the duration of thermal treatment of films, although the kinetics of this process is independent of film thickness. In films containing hydrochloric acid and aluminum chloride, the formation rate of polyenes with n ≥ 8 rapidly drops as film thickness decreases and the annealing time increases. As a result, at a film thickness of less than 10-12 µm, long-chain polyenes are not formed at all in these films no matter how long thermal duration is. The reason for this behavior is that hydrochloric acid catalyzing polymer dehydration in these films evaporates from the films during thermal treatment, the evaporation rate inversely depending on film thickness.

  4. [Asymmetric synthesis of aromatic L-amino acids catalyzed by transaminase].

    Science.gov (United States)

    Xia, Wenna; Sun, Yu; Min, Cong; Han, Wei; Wu, Sheng

    2012-11-01

    Aromatic L-Amino acids are important chiral building blocks for the synthesis of many drugs, pesticides, fine chemicals and food additives. Due to the high activity and steroselectivity, enzymatic synthesis of chiral building blocks has become the main research direction in asymmetric synthesis field. Guided by the phylogenetic analysis of transaminases from different sources, two representative aromatic transaminases TyrB and Aro8 in type I subfamily, from the prokaryote Escherichia coli and eukaryote Saccharomyces cerevisia, respectively, were applied for the comparative study of asymmetric transamination reaction process and catalytic efficiency of reversely converting keto acids to the corresponding aromatic L-amino acid. Both TyrB and Aro8 could efficiently synthesize the natural aromatic amino acids phenylalanine and tyrosine as well as non-natural amino acid phenylglycine. The chiral HPLC analysis showed the produced amino acids were L-configuration and the e.e value was 100%. L-alanine was the optimal amino donor, and the transaminase TyrB and Aro8 could not use D-amino acids as amino donor. The optimal molar ratio of amino donor (L-alanine) and amino acceptor (aromatic alpha-keto acids) was 4:1. Both of the substituted group on the aromatic ring and the length of fatty acid carbon chain part in the molecular structure of aromatic substrate alpha-keto acid have the significant impact on the enzyme-catalyzed transamination efficiency. In the experiments of preparative-scale transamination synthesis of L-phenylglycine, L-phenylalanine and L-tyrosine, the specific production rate catalyzed by TryB were 0.28 g/(g x h), 0.31 g/(g x h) and 0.60 g/(g x h) and the specific production rate catalyzed by Aro8 were 0.61 g/(g x h), 0.48 g/(g x h) and 0.59 g/(g x h). The results obtained here were useful for applying the transaminases to asymmetric synthesis of L-amino acids by reversing the reaction balance in industry.

  5. Esterification of Oleic Acid for Biodiesel Production Catalyzed by SnCl2: A Kinetic Investigation

    Directory of Open Access Journals (Sweden)

    Marcio J. da Silva

    2008-09-01

    Full Text Available The production of biodiesel from low-cost raw materials which generally contain high amounts of free fatty acids (FFAs is a valuable alternative that would make their production costs more competitive than petroleum-derived fuel. Currently, the production of biodiesel from this kind of raw materials comprises a two-stage process, which requires an initial acid-catalyzed esterification of the FFA, followed by a basecatalyzed transesterification of the triglycerides. Commonly, the acid H2SO4 is the catalyst on the first step of this process. It must be said, however, that major drawbacks such as substantial reactor corrosion and the great generation of wastes, including the salts formed due to neutralization of the mineral acid, are negative and virtually unsurmountable aspects of this protocol. In this paper, tin(II chloride dihydrate (SnCl2·2H2O, an inexpensive Lewis acid, was evaluated as catalyst on the ethanolysis of oleic acid, which is the major component of several fat and vegetable oils feedstocks. Tin chloride efficiently promoted the conversion of oleic acid into ethyl oleate in ethanol solution and in soybean oil samples, under mild reaction conditions. The SnCl2 catalyst was shown to be as active as the mineral acid H2SO4. Its use has relevant advantages in comparison to mineral acids catalysts, such as less corrosion of the reactors and as well as avoiding the unnecessary neutralization of products. Herein, the effect of the principal parameters of reaction on the yield and rate of ethyl oleate production has been investigated. Kinetic measurements revealed that the esterification of oleic acid catalyzed by SnCl2·2H2O is first-order in relation to both FFAs and catalyst concentration. Experimentally, it was verified that the energy of activation of the esterification reaction of oleic acid catalyzed by SnCl2 was very close those reported for H2SO4.

  6. Synthesis of 2-monoacylglycerols and structured triacylglycerols rich in polyunsaturated fatty acids by enzyme catalyzed reactions.

    Science.gov (United States)

    Rodríguez, Alicia; Esteban, Luis; Martín, Lorena; Jiménez, María José; Hita, Estrella; Castillo, Beatriz; González, Pedro A; Robles, Alfonso

    2012-08-10

    This paper studies the synthesis of structured triacylglycerols (STAGs) by a four-step process: (i) obtaining 2-monoacylglycerols (2-MAGs) by alcoholysis of cod liver oil with several alcohols, catalyzed by lipases Novozym 435, from Candida antartica and DF, from Rhizopus oryzae, (ii) purification of 2-MAGs, (iii) formation of STAGs by esterification of 2-MAGs with caprylic acid catalyzed by lipase DF, from R. oryzae, and (iv) purification of these STAGs. For the alcoholysis of cod liver oil, absolute ethanol, ethanol 96% (v/v) and 1-butanol were compared; the conditions with ethanol 96% were then optimized and 2-MAG yields of around 54-57% were attained using Novozym 435. In these 2-MAGs, DHA accounted for 24-31% of total fatty acids. In the operational conditions this lipase maintained a stable level of activity over at least 11 uses. These results were compared with those obtained with lipase DF, which deactivated after only three uses. The alcoholysis of cod liver oil and ethanol 96% catalyzed by Novozym 435 was scaled up by multiplying the reactant amounts 100-fold and maintaining the intensity of treatment constant (IOT=3g lipase h/g oil). In these conditions, the 2-MAG yield attained was about 67%; these 2-MAGs contained 36.6% DHA. The synthesized 2-MAGs were separated and purified from the alcoholysis reaction products by solvent extraction using solvents of low toxicity (ethanol and hexane); 2-MAG recovery yield and purity of the target product were approximately 96.4% and 83.9%, respectively. These 2-MAGs were transformed to STAGs using the optimal conditions obtained in a previous work. After synthesis and purification, 93% pure STAGs were obtained, containing 38% DHA at sn-2 position and 60% caprylic acid (CA) at sn-1,3 positions (of total fatty acids at these positions), i.e. the major TAG is the STAG with the structure CA-DHA-CA.

  7. Acid-catalyzed hydrogenation of olefins. A theoretical study of the HF- and H/sub 3/O/sup +/-catalyzed hydrogenation of ethylene

    Energy Technology Data Exchange (ETDEWEB)

    Siria, J.C.; Duran, M.; Lledos, A.; Bertran, J.

    1987-12-09

    The HF- and H/sub 3/O/sup +/-catalyzed hydrogenation of ethylene and the direct addition of molecular hydrogen to ethylene have been studied theoretically by means of ab initio MO calculations using different levels of theory. The main results are that catalysis by HF lowers the potential energy barrier to a large extent, while catalysis by H/sub 3/O/sup +/ diminishes dramatically the barrier for the reaction. Entropic contributions leave these results unchanged. The mechanisms of the two acid-catalyzed hydrogenations are somewhat different. While catalysis by HF exhibits bifunctional characteristics, catalysis by H/sub 3/O/sup +/ proceeds via an initial formation of a carbocation. It is shown that catalysis by strong acids may be an alternate way for olefin hydrogenation.

  8. Biodiesel Production from Spent Fish Frying Oil Through Acid-Base Catalyzed Transesterification

    Directory of Open Access Journals (Sweden)

    Abdalrahman B. Fadhil

    2012-06-01

    Full Text Available Biodiesel fuels were prepared from a special type of frying oil namely spent fish frying oil through two step transesterification viz. acid-base catalyzed transesterification. Hydrochloric acid and potassium hydroxide with methanol were used for this purpose. The oil was pre-treated with (1.0 wt% HCl and methanol to reduce free fatty acids content of the oil. Then, conditions of the base catalyzed step such as base concentration, reaction temperature, methanol to oil molar ratio and reaction time were optimized. The study raveled that, 0.50% KOH w/w of oil; a 6:1 methanol to oil molar ratio; a reaction temperature of 60°C and a duration of 1h were the optimal conditions because they resulted in high biodiesel yield. Fuel properties of the products were assessed and found better than those of the parent oil. Furthermore, they met the specified limits according to the ASTM standards. Thin layer chromatography was used as a simple technique to monitor the transesterification of the oil. Blending of the optimal biodiesel sample with petro diesel using specified volume percentages was done as well. The results indicated that biodiesel had slight effect on the values of the assessed properties.

  9. Palladium(II)-Catalyzed Tandem Synthesis of Acenes Using Carboxylic Acids as Traceless Directing Groups.

    Science.gov (United States)

    Kim, Kiho; Vasu, Dhananjayan; Im, Honggu; Hong, Sungwoo

    2016-07-18

    A straightforward synthetic strategy for generating useful anthracene derivatives was developed involving palladium(II)-catalyzed tandem transformation with carboxylic acids as traceless directing groups. Carboxyl-directed C-H alkenylation, carboxyl-directed secondary C-H activation and rollover, intramolecular C-C bond formation, and decarboxylative aromatization are proposed as the key steps in the tandem reaction pathway. This novel synthetic route utilizes a broad range of substrates and provides a convenient synthetic tool that allows access to acenes. PMID:27244536

  10. Facile isothermal solid acid catalyzed ionic liquid pretreatments to enhance the combined sugars production from Arundo donax Linn.

    OpenAIRE

    You, Tingting; Shao, Lupeng; Wang, Ruizhen; Zhang, Liming; Feng XU

    2016-01-01

    Background Solid acid catalyzed inexpensive ionic liquid (IL) pretreatment is promising because of its effectiveness at decreasing biomass recalcitrance to subsequent enzymatic hydrolysis or in situ hydrolysis of carbohydrate oligomers. However, the conventional strategy was limited by the complex non-isothermal process and considering only one aspect of sugar recovery. In this study, facile isothermal pretreatments using Amberlyst 35DRY catalyzed 1-n-butyl-3-methylimidazolium chloride ([C4mi...

  11. 7-deoxyloganetic acid synthase catalyzes a key 3 step oxidation to form 7-deoxyloganetic acid in Catharanthus roseus iridoid biosynthesis.

    Science.gov (United States)

    Salim, Vonny; Wiens, Brent; Masada-Atsumi, Sayaka; Yu, Fang; De Luca, Vincenzo

    2014-05-01

    Iridoids are key intermediates required for the biosynthesis of monoterpenoid indole alkaloids (MIAs), as well as quinoline alkaloids. Although most iridoid biosynthetic genes have been identified, one remaining three step oxidation required to form the carboxyl group of 7-deoxyloganetic acid has yet to be characterized. Here, it is reported that virus-induced gene silencing of 7-deoxyloganetic acid synthase (7DLS, CYP76A26) in Catharanthus roseus greatly decreased levels of secologanin and the major MIAs, catharanthine and vindoline in silenced leaves. Functional expression of this gene in Saccharomyces cerevisiae confirmed its function as an authentic 7DLS that catalyzes the 3 step oxidation of iridodial-nepetalactol to form 7-deoxyloganetic acid. The identification of CYP76A26 removes a key bottleneck for expression of iridoid and related MIA pathways in various biological backgrounds. PMID:24594312

  12. Noble metal catalyzed hydrogen generation from formic acid in nitrite-containing simulated nuclear waste media

    International Nuclear Information System (INIS)

    The Hanford Waste Vitrification Plant (HWVP) is being designed by the U.S. Department of Energy to immobilize high-level nuclear waste. Simulants for the HWVP feed containing the major nonradioactive components Al, Cd, Fe, Mn, Nd, Ni, Si, Zr, Na, CO32-, NO3- and NO2- were used as media to evaluate the stability of formic acid towards hydrogen evolution by the reaction HCO2H→H2+/CO2 catalyzed by the noble metals Ru, Rh, and/or Pd found in significant quantities in uranium fission products. Small-scale experiments using 40-50 mL of feed simulant in closed glass reactors (250-550 mL total volume) at 80-100 degree C were used to study the effect of nitrite and nitrate ion on the catalytic activities of the noble metals for formic acid decomposition. Reactions were monitored using gas chromatography to analyze the CO2, H2, NO, and N2O in the gas phase as a function of time. Rhodium, which was introduced as soluble RhCl3.3H2O, was found to be the most active catalyst for hydrogen generation from formic acid above nearly 80 degree C in the presence of nitrite ion in accord with earlier observations. The apparent homogeneous nature of the nitrite-promoted Rh-catalyzed formic acid decomposition is consistent with the approximate pseudo-first-order dependence of the hydrogen production rate on Rh concentration. 24 refs., 7 figs., 2 tabs

  13. Recovery of arabinan in acetic acid-catalyzed hydrothermal pretreatment on corn stover

    DEFF Research Database (Denmark)

    Xu, Jian; Hedegaard, Mette Christina; Thomsen, Anne Belinda

    2009-01-01

    Acetic acid-catalyzed hydrothermal pretreatment was done on corn stover under 195 °C, 15 min with the acetic acid ranging from 5 × 10−3 to 0.2 g g−1 corn stover. After pretreatment, the water-insoluble solids (WISs) and liquors were collected respectively. Arabinan recoveries from both WIS...... and liquors were investigated. The results indicate that there was no detectable arabinan left in the WIS when the acetic acid of 0.1 and 0.2 g g−1 corn stover were used in the pretreatment. The arabinan contents in the other WISs were not more than 10%. However, the arabinan found in the liquors...... was not covering the amount of arabinan released from the raw corn stover. For the arabinan recovery from liquor fractions, the highest of 43.57% was obtained by the pretreatment of acetic acid of 0.01 g g−1 of corn stover and the lowest was only 26.77% when the acetic acid of 0.2 g g−1 corn stover was used...

  14. Palladium-atom catalyzed formic acid decomposition and the switch of reaction mechanism with temperature.

    Science.gov (United States)

    He, Nan; Li, Zhen Hua

    2016-04-21

    Formic acid decomposition (FAD) reaction has been an innovative way for hydrogen energy. Noble metal catalysts, especially palladium-containing nanoparticles, supported or unsupported, perform well in this reaction. Herein, we considered the simplest model, wherein one Pd atom is used as the FAD catalyst. With high-level theoretical calculations of CCSD(T)/CBS quality, we investigated all possible FAD pathways. The results show that FAD catalyzed by one Pd atom follows a different mechanism compared with that catalyzed by surfaces or larger clusters. At the initial stage of the reaction, FAD follows a dehydration route and is quickly poisoned by CO due to the formation of very stable PdCO. PdCO then becomes the actual catalyst for FAD at temperatures approximately below 1050 K. Beyond 1050 K, there is a switch of catalyst from PdCO to Pd atom. The results also show that dehydration is always favoured over dehydrogenation on either the Pd-atom or PdCO catalyst. On the Pd-atom catalyst, neither dehydrogenation nor dehydration follows the formate mechanism. In contrast, on the PdCO catalyst, dehydrogenation follows the formate mechanism, whereas dehydration does not. We also systematically investigated the performance of 24 density functional theory methods. We found that the performance of the double hybrid mPW2PLYP functional is the best, followed by the B3LYP, B3PW91, N12SX, M11, and B2PLYP functionals.

  15. An atom-economic approach to carboxylic acids via Pd-catalyzed direct addition of formic acid to olefins with acetic anhydride as a co-catalyst.

    Science.gov (United States)

    Wang, Yang; Ren, Wenlong; Shi, Yian

    2015-08-21

    An effective Pd-catalyzed hydrocarboxylation of olefins using formic acid with acetic anhydride as a co-catalyst is described. A variety of carboxylic acids are obtained in good yields with high regioselectivities under mild reaction conditions without the use of toxic CO gas.

  16. Phenylalanine Aminomutase-Catalyzed Addition of Ammonia to Substituted Cinnamic Acids : a Route to Enantiopure alpha- and beta-Amino Acids

    NARCIS (Netherlands)

    Szymanski, Wiktor; Wu, Bian; Weiner, Barbara; Wildeman, Stefaan de; Feringa, Ben L.; Janssen, Dick B.

    2009-01-01

    An approach is described for the synthesis of aromatic alpha- and beta-amino acids that Uses phenylalanine aminomutase to catalyze a highly enantioselective addition of ammonia to substituted cinnamic acids. The reaction has a broad scope and yields Substituted alpha- and beta-phenylalanines with ex

  17. Intrinsic oxidation kinetics of sulfite catalyzed by peracetic acid under different water quality and light conditions

    Institute of Scientific and Technical Information of China (English)

    WANG LiDong; ZHAO Yi; LI QiangWei; CHEN ZhouYan; LIU SongTao; MA YongLiang; HAO JiMing

    2009-01-01

    Oxidation of sulfite is an important process in wet flue gas desulfurization. Using highly purified water or distilled water as a reaction medium and a transparent or an opaque intermittent reaction apparatus, the intrinsic oxidation kinetics of sulfite catalyzed by peracetic acid was investigated under four dif-ferent conditions. The reaction order of the reagents and the activation energy were obtained. The re-sults indicate that water quality and light have no obvious effects on the reaction order and activation energy, but have an influence on the reaction rate constant. The mechanism of the intrinsic reaction is proposed. The results derived with this mechanism are in good agreement with the experimental re-sults.

  18. Intrinsic oxidation kinetics of sulfite catalyzed by peracetic acid under different water quality and light conditions

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Oxidation of sulfite is an important process in wet flue gas desulfurization.Using highly purified water or distilled water as a reaction medium and a transparent or an opaque intermittent reaction apparatus,the intrinsic oxidation kinetics of sulfite catalyzed by peracetic acid was investigated under four dif-ferent conditions.The reaction order of the reagents and the activation energy were obtained.The re-sults indicate that water quality and light have no obvious effects on the reaction order and activation energy,but have an influence on the reaction rate constant.The mechanism of the intrinsic reaction is proposed.The results derived with this mechanism are in good agreement with the experimental re-sults.

  19. Investigation of acetic acid-catalyzed hydrothermal pretreatment on corn stover

    DEFF Research Database (Denmark)

    Xu, Jian; Thomsen, Mette Hedegaard; Thomsen, Anne Belinda

    2010-01-01

    xylan recovery of 81.82% was observed by the pretreatment with 10 g AA/kg RCS. The toxic test on liquors showed that the inhibition effect happened to Baker's yeast when the acetic acid used in the pretreatment was higher than 100 g/kg RCS. The WIS obtained from the pretreatment with 15 g and 30 g....../kg RCS were subjected to enzymatic hydrolysis and more easily converted to ethanol by Baker's yeast, which gave the ethanol concentration of 33.72 g/L and 32.06 g/L, respectively, higher than 22.04 g/L which was from the non-catalyzed LHW pretreatment (195 °C, 15 min). The ethanol concentration from...

  20. Kinetics of Acid-Catalyzed Dehydration of Cyclic Hemiacetals in Organic Aerosol Particles in Equilibrium with Nitric Acid Vapor.

    Science.gov (United States)

    Ranney, April P; Ziemann, Paul J

    2016-04-28

    Previous studies have shown that 1,4-hydroxycarbonyls, which are often major products of the atmospheric oxidation of hydrocarbons, can undergo acid-catalyzed cyclization and dehydration in aerosol particles to form highly reactive unsaturated dihydrofurans. In this study the kinetics of dehydration of cyclic hemiacetals, the rate-limiting step in this process, was investigated in a series of environmental chamber experiments in which secondary organic aerosol (SOA) containing cyclic hemiacetals was formed from the reaction of n-pentadecane with OH radicals in dry air in the presence of HNO3. A particle beam mass spectrometer was used to monitor the formation and dehydration of cyclic hemiacetals in real time, and SOA and HNO3 were quantified in filter samples by gravimetric analysis and ion chromatography. Measured dehydration rate constants increased linearly with increasing concentration of HNO3 in the gas phase and in SOA, corresponding to catalytic rate constants of 0.27 h(-1) ppmv(-1) and 7.0 h(-1) M(-1), respectively. The measured Henry's law constant for partitioning of HNO3 into SOA was 3.7 × 10(4) M atm(-1), ∼25% of the value for dissolution into water, and the acid dissociation constant was estimated to be water. The results indicate that HNO3 was only weakly dissociated in the SOA and that dehydration of cyclic hemiacetals was catalyzed by molecular HNO3 rather than by H(+). The Henry's law constant and kinetics relationships measured here can be used to improve mechanisms and models of SOA formation from the oxidation of hydrocarbons in dry air in the presence of NOx, which are conditions commonly used in laboratory studies. The fate of cyclic hemiacetals in the atmosphere, where the effects of higher relative humidity, organic/aqueous phase separation, and acid catalysis by molecular H2SO4 and/or H(+) are likely to be important, is discussed.

  1. Lipase-catalyzed synthesis of fatty acid amide (erucamide) using fatty acid and urea.

    Science.gov (United States)

    Awasthi, Neeraj Praphulla; Singh, R P

    2007-01-01

    Ammonolysis of fatty acids to the corresponding fatty acid amides is efficiently catalysed by Candida antartica lipase (Novozym 435). In the present paper lipase-catalysed synthesis of erucamide by ammonolysis of erucic acid and urea in organic solvent medium was studied and optimal conditions for fatty amides synthesis were established. In this process erucic acid gave 88.74 % pure erucamide after 48 hour and 250 rpm at 60 degrees C with 1:4 molar ratio of erucic acid and urea, the organic solvent media is 50 ml tert-butyl alcohol (2-methyl-2-propanol). This process for synthesis is economical as we used urea in place of ammonia or other amidation reactant at atmospheric pressure. The amount of catalyst used is 3 %.

  2. Synthesis, isolation and characterization of methyl levulinate from cellulose catalyzed by extremely low concentration acid

    Institute of Scientific and Technical Information of China (English)

    Hui; Li; Lincai; Peng; Lu; Lin; Keli; Chen; Heng; Zhang

    2013-01-01

    A direct synthesis of methyl levulinate from cellulose alcoholysis in methanol medium under mild condition(180 210 C)catalyzed by extremely low concentration sulfuric acid(0.01 mol/L)and the product isolation were developed in this study.Effects of different process variables towards the catalytic performance were performed as a function of reaction time.The results indicated that sulfuric acid concentration,temperature and initial cellulose concentration had significant effects on the synthesis of methyl levulinate.An optimized yield of around 50%was achieved at 210 C for 120 min with sulfuric acid concentration of 0.01 mol/L and initial cellulose concentration below 100 g/L.The resulting product mixture was isolated by a distillation technique that combines an atmospheric distillation with a vacuum distillation where n-dodecane was added to help distill the heavy fraction.The light fraction including mainly methanol could be reused as the reaction medium without any substantial change in the yield of methyl levulinate.The chemical composition and structural of lower heavy fraction were characterized by GC/MS,FTIR,1H-NMR and13C-NMR techniques.Methyl levulinate was found to be a major ingredient of lower heavy fraction with the content over 96%.This pathway is efficient,environmentally benign and economical for the production of pure levulinate esters from cellulose.

  3. Acid-Catalyzed Transesterification Reaction of Beef Tallow For Biodiesel Production By Factor Variation

    Directory of Open Access Journals (Sweden)

    R.C. Ehiri

    2014-07-01

    Full Text Available Biodiesel is a diesel grade fuel made by transesterification reaction of vegetable oils and animal fats with alcohol. Three variable factors that affect the yield of biodiesel namely, reaction time, reaction temperature and catalyst concentration were studied in this work. The biodiesel was produced via a batchprocess acid-catalyzed transesterification reaction of beef tallow with methanol. Optimal conditions for the reaction were established in a three factor two-level (23 central composite design with the biodiesel pretreatment yield as the response surface. The results show that the mean yield of biodiesel was 92.04% with a standard deviation of 5.16. An optimal biodiesel yield of 96.30% occurred at 0.5% HCl catalyst concentration and at constant conditions of 1.5h reaction time, 60oC reaction temperature and 6:1 methanol: tallow volume ratio. Gas chromatographic analysis of the beef tallow identified palmitic, stearic and oleic acids in it while the fatty acid methyl esters in the biodiesel product were oleate and linoleate. Catalysis was the most significant factor in the transesterification process.

  4. (Salen)Ti(Ⅳ)-Catalyzed Asymmetric Ring-opening of meso Epoxides Using Dithiophosphorus Acid as the Nucleophile

    Institute of Scientific and Technical Information of China (English)

    Zheng Hong ZHOU; Zhao Ming LI; Bing LIU; Kang Ying LI; Li Xin WANG; Guo Feng ZHAO; Qi Lin ZHOU; Chu Chi TANG

    2006-01-01

    The asymmetric ring-opening of epoxides with dithiophosphorus acids catalyzed by a (salen)Ti(Ⅳ) complex formed in situ from the reaction of Ti(OPr-i)4 and the chiral Schiff base derived from (1R,2R)-(+)-diaminocyclohexane was realized. The resulting products were obtained with low to good enantioselectivity (up to 73% ee).

  5. Aerobic oxidation of benzylic aldehydes to acids catalyzed by iron (Ⅲ) meso-tetraphenylporphyrin chloride under ambient conditions

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Highly efficient aerobic oxidation of benzylic aldehydes to the corresponding acids catalyzed by iron (Ⅲ) meso-tetraphenylporphyrin chloride (Fe(TPP)Cl) under ambient conditions was developed. The catalyst has been proved to be an excellent catalyst for the system in the presence of molecular oxygen and isobutryaldehyde at room temperature.

  6. Selective Synthesis of Unsaturated N-Acylethanolamines by Lipase-Catalyzed N-Acylation of Ethanolamine with Unsaturated Fatty Acids

    NARCIS (Netherlands)

    Plastina, P.; Vincken, J.P.; Gruppen, H.; Witkamp, R.F.; Gabriele, B.

    2009-01-01

    The selective synthesis of unsaturated N-acylethanolamines 1b-6b by lipase-catalyzed direct condensation between unsaturated fatty acids 1a-6a and ethanolamine is reported. Reactions were carried out in hexane at 40 °C, in the presence of Candida antarctica Lipase B as the catalyst, to give the corr

  7. Ru/Me-BIPAM-Catalyzed Asymmetric Addition of Arylboronic Acids to Aliphatic Aldehydes and α-Ketoesters

    Directory of Open Access Journals (Sweden)

    Momoko Watanabe

    2011-06-01

    Full Text Available A ruthenium-catalyzed asymmetric arylation of aliphatic aldehydes and α-ketoesters with arylboronic acids has been developed, giving chiral alkyl(arylmethanols and α-hydroxy esters in good yields. The use of a chiral bidentate phosphoramidite ligand (Me-BIPAM achieved excellent enantioselectivities.

  8. Potential of phosphoric acid-catalyzed pretreatment and subsequent enzymatic hydrolysis for biosugar production from Gracilaria verrucosa.

    Science.gov (United States)

    Kwon, Oh-Min; Kim, Sung-Koo; Jeong, Gwi-Taek

    2016-07-01

    This study combined phosphoric acid-catalyzed pretreatment and enzymatic hydrolysis to produce biosugars from Gracilaria verrucosa as a potential renewable resource for bioenergy applications. We optimized phosphoric acid-catalyzed pretreatment conditions to 1:10 solid-to-liquid ratio, 1.5 % phosphoric acid, 140 °C, and 60 min reaction time, producing a 32.52 ± 0.06 % total reducing sugar (TRS) yield. By subsequent enzymatic hydrolysis, a 68.61 ± 0.90 % TRS yield was achieved. These results demonstrate the potential of phosphoric acid to produce biosugars for biofuel and biochemical production applications.

  9. Mechanistic insights into a BINOL-derived phosphoric acid-catalyzed asymmetric Pictet-Spengler reaction.

    Science.gov (United States)

    Overvoorde, Lois M; Grayson, Matthew N; Luo, Yi; Goodman, Jonathan M

    2015-03-01

    The reaction of tryptamine and (2-oxocyclohexyl)acetic acid can be catalyzed by 3,3'-bis(triphenylsilyl)-1,1'-bi-2-naphthol phosphoric acid to give an asymmetric β-carboline. This reaction was first studied by Holloway et al. ( Org. Lett. 2010 , 12 , 4720 - 4723 ), but their mechanistic work did not explain the high stereoselectivity achieved. This study uses density functional theory and hybrid quantum mechanics/molecular mechanics calculations to investigate this reaction and provide a model to explain its outcome. The step leading to diastereo- and enantioselectivity is an asymmetric Pictet-Spengler reaction involving an N-acyliminium ion bound to the catalyst in a bidentate fashion. This interaction occurs via hydrogen bonds between the two terminal oxygen atoms of the catalyst phosphate group and the hydrogen atoms at N and C2 of the substrate indole group. These bonds hold the transition structure rigidly and thus allow the catalyst triphenylsilyl groups to influence the enantioselectivity. PMID:25654215

  10. Brönsted Acid of Keggin Type Polyoxometalate Catalyzed Pinacol Rearrangement

    Directory of Open Access Journals (Sweden)

    Aldes Lesbani

    2014-07-01

    Full Text Available Keggin type polyoxometalates K4[a-SiW12O40] was synthesized and transformed to H4[a-SiW12O40]. Both catalysts have been used for pinacol rearrangement in toluene at 373 oK. The results showed that reaction of pinacol rearrangement did not proceed using K4[a-SiW12O40] as catalyst. The extent reac-tion time until 20 h also did not produce pinacolone as main product. By using H4[a-SiW12O40] as cata-lyst at 1 h reaction time gave conversion 100% with formation of pinacolone 72%. The reaction produce 27% of 2,3-dimethyl-1,3-butadiene as byproduct and 99% carbon balance for the reaction. This phe-nomenon indicated the Brönsted acid is a key role for catalytic reaction of pinacol rearrangement to pinacolone. © 2014 BCREC UNDIP. All rightsSubmitted: 21st January 2014; Revised: 21st April 2014; Accepted: 3rd May 2014[ How to Cite: Lesbani, A., Mohadi, R., (2014. Brönsted Acid of Keggin Type Polyoxometalate Catalyzed Pinacol Rearrangement. Bulletin of Chemical Reaction Engineering & Catalysis, 9 (2: 136-141. (doi:10.9767/bcrec.9.2.6074.136-141 ][ Permalink/DOI: http://dx.doi.org/10.9767/bcrec.9.2.6074.136-141

  11. Hetropolyacid-Catalyzed Oxidation of Glycerol into Lactic Acid under Mild Base-Free Conditions.

    Science.gov (United States)

    Tao, Meilin; Yi, Xiaohu; Delidovich, Irina; Palkovits, Regina; Shi, Junyou; Wang, Xiaohong

    2015-12-21

    Lactic acid (LA) is a versatile platform molecule owing to the opportunity to transform this compound into useful chemicals and materials. Therefore, efficient production of LA based on inexpensive renewable feedstocks is of utmost importance for insuring its market availability. Herein, we report the efficient conversion of glycerol into LA catalyzed by heteropolyacids (HPAs) under mild base-free conditions. The catalytic performance of molecular HPAs appears to correlate with their redox potential and Brønsted acidity. Namely, H3 PMo(12)O(40) (HPMo) exhibits the best selectivity towards LA (90 %) with 88 % conversion of glycerol. Loading of HPMo onto a carbon support (HPMo/C) further improves LA productivity resulting in 94 % selectivity at 98 % conversion under optimized reaction conditions. The reaction takes place through the formation of dihydroxyacetone/glyceraldehyde and pyruvaldehyde as intermediates. No leaching of HPMo was observed under the applied reaction conditions and HPMo/C could be recycled 5 times without significant loss of activity. PMID:26611678

  12. Origins of stereoselectivities in chiral phosphoric acid catalyzed allylborations and propargylations of aldehydes.

    Science.gov (United States)

    Wang, Hao; Jain, Pankaj; Antilla, Jon C; Houk, K N

    2013-02-01

    The chiral BINOL-phosphoric acid catalyzed allylboration and propargylation reactions are studied with density functional theory (B3LYP and B3LYP-D3). Two different models were recently proposed for these reactions by Goodman and our group, respectively. In Goodman's model for allylborations, the catalyst interacts with the boronate pseudoaxial oxygen. By contrast, our model for propargylations predicts that the catalyst interacts with the boronate pseudoequatorial oxygen. In both models, the phosphoric acid stabilizes the transition state by forming a strong hydrogen bond with the oxygen of the boronate and is oriented by a formyl hydrogen bond (Goodman model) and by other electrostatic attractions in our model. Both of these models have now been reinvestigated for both allylborations and propargylations. For the most effective catalyst for these reactions, the lowest energy transition state corresponds to Goodman's axial model, while the best transition state leading to the minor enantiomer involves the equatorial model. The high enantioselectivity observed with only the bulkiest catalyst arises from the steric interactions between the substrates and the bulky groups on the catalyst, and the resulting necessity for distortion of the catalyst in the disfavored transition state. PMID:23298338

  13. Glycolic acid-catalyzed deamidation of asparagine residues in degrading PLGA matrices: a computational study.

    Science.gov (United States)

    Manabe, Noriyoshi; Kirikoshi, Ryota; Takahashi, Ohgi

    2015-03-31

    Poly(lactic-co-glycolic acid) (PLGA) is a strong candidate for being a drug carrier in drug delivery systems because of its biocompatibility and biodegradability. However, in degrading PLGA matrices, the encapsulated peptide and protein drugs can undergo various degradation reactions, including deamidation at asparagine (Asn) residues to give a succinimide species, which may affect their potency and/or safety. Here, we show computationally that glycolic acid (GA) in its undissociated form, which can exist in high concentration in degrading PLGA matrices, can catalyze the succinimide formation from Asn residues by acting as a proton-transfer mediator. A two-step mechanism was studied by quantum-chemical calculations using Ace-Asn-Nme (Ace = acetyl, Nme = NHCH3) as a model compound. The first step is cyclization (intramolecular addition) to form a tetrahedral intermediate, and the second step is elimination of ammonia from the intermediate. Both steps involve an extensive bond reorganization mediated by a GA molecule, and the first step was predicted to be rate-determining. The present findings are expected to be useful in the design of more effective and safe PLGA devices.

  14. Cooperative Effects Between Arginine and Glutamic Acid in the Amino Acid-Catalyzed Aldol Reaction.

    Science.gov (United States)

    Valero, Guillem; Moyano, Albert

    2016-08-01

    Catalysis of the aldol reaction between cyclohexanone and 4-nitrobenzaldehyde by mixtures of L-Arg and of L-Glu in wet dimethyl sulfoxide (DMSO) takes place with higher enantioselectivity (up to a 7-fold enhancement in the anti-aldol for the 1:1 mixture) than that observed when either L-Glu or L-Arg alone are used as the catalysts. These results can be explained by the formation of a catalytically active hydrogen-bonded complex between both amino acids, and demonstrate the possibility of positive cooperative effects in catalysis by two different α-amino acids. Chirality 28:599-605, 2016. © 2016 Wiley Periodicals, Inc. PMID:27362554

  15. Kinetics of Acid-Catalyzed Dehydration of Cyclic Hemiacetals in Organic Aerosol Particles in Equilibrium with Nitric Acid Vapor.

    Science.gov (United States)

    Ranney, April P; Ziemann, Paul J

    2016-04-28

    Previous studies have shown that 1,4-hydroxycarbonyls, which are often major products of the atmospheric oxidation of hydrocarbons, can undergo acid-catalyzed cyclization and dehydration in aerosol particles to form highly reactive unsaturated dihydrofurans. In this study the kinetics of dehydration of cyclic hemiacetals, the rate-limiting step in this process, was investigated in a series of environmental chamber experiments in which secondary organic aerosol (SOA) containing cyclic hemiacetals was formed from the reaction of n-pentadecane with OH radicals in dry air in the presence of HNO3. A particle beam mass spectrometer was used to monitor the formation and dehydration of cyclic hemiacetals in real time, and SOA and HNO3 were quantified in filter samples by gravimetric analysis and ion chromatography. Measured dehydration rate constants increased linearly with increasing concentration of HNO3 in the gas phase and in SOA, corresponding to catalytic rate constants of 0.27 h(-1) ppmv(-1) and 7.0 h(-1) M(-1), respectively. The measured Henry's law constant for partitioning of HNO3 into SOA was 3.7 × 10(4) M atm(-1), ∼25% of the value for dissolution into water, and the acid dissociation constant was estimated to be <8 × 10(-4), at least a factor of 10(4) less than that for HNO3 in water. The results indicate that HNO3 was only weakly dissociated in the SOA and that dehydration of cyclic hemiacetals was catalyzed by molecular HNO3 rather than by H(+). The Henry's law constant and kinetics relationships measured here can be used to improve mechanisms and models of SOA formation from the oxidation of hydrocarbons in dry air in the presence of NOx, which are conditions commonly used in laboratory studies. The fate of cyclic hemiacetals in the atmosphere, where the effects of higher relative humidity, organic/aqueous phase separation, and acid catalysis by molecular H2SO4 and/or H(+) are likely to be important, is discussed. PMID:27043733

  16. Ion-exchange Resin Catalyzed Esterification of Lactic Acid with Isopropanol: a Kinetic Study

    Directory of Open Access Journals (Sweden)

    Amrit P. Toor

    2011-05-01

    Full Text Available The kinetic behavior of esterification of lactic acid with isopropanol over an acidic cation exchange resin, Amberlyst 15, was studied under isothermal condition. Isopropyl lactate synthesized in this reaction is an important pharmaceutical intermediate. The experiments were carried out in a stirred batch reactor in the temperature range of 323.15 to 353.15 K. The effect of various parameters such as temperature, molar ratio and catalyst loading was studied. Variation in parameters on rate of reaction demonstrated that the reaction was intrinsically controlled. Kinetic modeling was performed using Eley-Rideal model which acceptably fits the experimental data. The activation energy was found to be 22.007 kJ/mol and frequency factor was 0.036809 l2 g-1 mol-1 min-1 for forward reaction. The value of entropy for the forward reaction was found to be 182.317 J K-1 mol-1 . © 2011 BCREC UNDIP. All rights reserved(Received: 19th January 2011, Revised: 16th March 2011; Accepted: 16th March 2011[How to Cite: A.P. Toor, M. Sharma, S. Thakur, and R. K. Wanchoo. (2011. Ion-exchange Resin Catalyzed Esterification of Lactic Acid with Isopropanol: a Kinetic Study. Bulletin of Chemical Reaction Engineering and Catalysis, 6(1: 39-45. doi:10.9767/bcrec.6.1.791.39-45][How to Link / DOI: http://dx.doi.org/10.9767/bcrec.6.1.791.39-45 || or local:  http://ejournal.undip.ac.id/index.php/bcrec/article/view/791 ] | View in  

  17. Lipase-catalyzed Synthesis of Caffeic Acid Phenethyl Ester in Ionic Liquids:Effect of Specific Ions and Reaction Parameters

    Institute of Scientific and Technical Information of China (English)

    王俊; 李晶; 张磊霞; 顾双双; 吴福安

    2013-01-01

    Caffeic acid phenethyl ester (CAPE) is a rare, naturally occurring phenolic food additive. This work systematically reported fundamental data on conversion of caffeic acid (CA), yield of CAPE, and reactive selectiv-ity during the lipase-catalyzed esterification process of CA and phenylethanol (PE) in ionic liquids (ILs). Sixteen ILs were selected as the reaction media, and the relative lipase-catalyzed synthesis properties of CAPE were meas-ured in an effort to enhance the yield of CAPE with high selectivity. The results indicated that ILs containing weakly coordinating anions and cations with adequate alkyl chain length improved the synthesis of CAPE. [Emim][Tf2N] was selected as the optimal reaction media. The optimal parameters were as follows by response surface methodology (RSM):reaction temperature, 84.0 °C;mass ratio of Novozym 435 to CA, 14︰1;and molar ratio of PE to CA, 16︰1. The highest reactive selectivity of CAPE catalyzed by Novozym 435 in [Emim][Tf2N] reached 64.55%(CA conversion 98.76%and CAPE yield 63.75%, respectively). Thus, lipase-catalyzed esterifica-tion in ILs is a promising method suitable for CAPE production.

  18. Lewis acid promoted ruthenium(II)-catalyzed etherifications by selective hydrogenation of carboxylic acids/esters.

    Science.gov (United States)

    Li, Yuehui; Topf, Christoph; Cui, Xinjiang; Junge, Kathrin; Beller, Matthias

    2015-04-20

    Ethers are of fundamental importance in organic chemistry and they are an integral part of valuable flavors, fragrances, and numerous bioactive compounds. In general, the reduction of esters constitutes the most straightforward preparation of ethers. Unfortunately, this transformation requires large amounts of metal hydrides. Presented herein is a bifunctional catalyst system, consisting of Ru/phosphine complex and aluminum triflate, which allows selective synthesis of ethers by hydrogenation of esters or carboxylic acids. Different lactones were reduced in good yields to the desired products. Even challenging aromatic and aliphatic esters were reduced to the desired products. Notably, the in situ formed catalyst can be reused several times without any significant loss of activity. PMID:25728921

  19. A heteromeric membrane-bound prenyltransferase complex from hop catalyzes three sequential aromatic prenylations in the bitter acid pathway.

    Science.gov (United States)

    Li, Haoxun; Ban, Zhaonan; Qin, Hao; Ma, Liya; King, Andrew J; Wang, Guodong

    2015-03-01

    Bitter acids (α and β types) account for more than 30% of the fresh weight of hop (Humulus lupulus) glandular trichomes and are well known for their contribution to the bitter taste of beer. These multiprenylated chemicals also show diverse biological activities, some of which have potential benefits to human health. The bitter acid biosynthetic pathway has been investigated extensively, and the genes for the early steps of bitter acid synthesis have been cloned and functionally characterized. However, little is known about the enzyme(s) that catalyze three sequential prenylation steps in the β-bitter acid pathway. Here, we employed a yeast (Saccharomyces cerevisiae) system for the functional identification of aromatic prenyltransferase (PT) genes. Two PT genes (HlPT1L and HlPT2) obtained from a hop trichome-specific complementary DNA library were functionally characterized using this yeast system. Coexpression of codon-optimized PT1L and PT2 in yeast, together with upstream genes, led to the production of bitter acids, but no bitter acids were detected when either of the PT genes was expressed by itself. Stepwise mutation of the aspartate-rich motifs in PT1L and PT2 further revealed the prenylation sequence of these two enzymes in β-bitter acid biosynthesis: PT1L catalyzed only the first prenylation step, and PT2 catalyzed the two subsequent prenylation steps. A metabolon formed through interactions between PT1L and PT2 was demonstrated using a yeast two-hybrid system, reciprocal coimmunoprecipitation, and in vitro biochemical assays. These results provide direct evidence of the involvement of a functional metabolon of membrane-bound prenyltransferases in bitter acid biosynthesis in hop. PMID:25564559

  20. Manganese(II) catalyzes the bicarbonate-dependent oxidation of amino acids by hydrogen peroxide and the amino acid-facilitated dismutation of hydrogen peroxide.

    OpenAIRE

    Berlett, B S; Chock, P B; Yim, M B; Stadtman, E. R.

    1990-01-01

    In bicarbonate/CO2 buffer, Mn(II) and Fe(II) catalyze the oxidation of amino acids by H2O2 and the dismutation of H2O2. As the Mn(II)/Fe(II) ratio is increased, the yield of carbonyl compounds per mole of leucine oxidized is essentially constant, but the ratio of alpha-ketoisocaproate to isovaleraldehyde formed increases, and the fraction of H2O2 converted to O2 increases. In the absence of Fe(II), the rate of Mn(II)-catalyzed leucine oxidation is directly proportional to the H2O2, Mn(II), an...

  1. High efficient acetalization of carbonyl compounds with diols catalyzed by novel carbon-based solid strong acid catalyst

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The novel carbon-based acid catalyst has been applied to catalyzing the acetalization and ketalization. The results showed that the catalyst was very efficient with the average yield over 93%. The novel heterogeneous catalyst has the advantages of high activity, wide applicability even to 7-membered ring acetals, strikingly simple workup procedure, non-pollution, and reusability, which will contribute to the green process greatly.

  2. Probing the "additive effect" in the proline and proline hydroxamic acid catalyzed asymmetric addition of nitroalkanes to cyclic enones.

    Science.gov (United States)

    Hanessian, Stephen; Govindan, Subramaniyan; Warrier, Jayakumar S

    2005-11-01

    The effect of chirality and steric bulk of 2,5-disubstituted piperazines as additives in the conjugate addition of 2-nitropropane to cyclohexenone, catalyzed by l-proline, was investigated. Neither chirality nor steric bulk affects the enantioselectivity of addition, which gives 86-93% ee in the presence of achiral and chiral nonracemic 2,5-disubstituted piperazines. Proline hydroxamic acid is shown for the first time to be an effective organocatalyst in the same Michael reaction. PMID:16189834

  3. Tandem Suzuki-Miyaura coupling/acid-catalyzed cyclization between vinyl ether boronates and vinyl halides: a concise approach to polysubstituted furans.

    Science.gov (United States)

    Butkevich, Alexey N; Meerpoel, Lieven; Stansfield, Ian; Angibaud, Patrick; Corbu, Andrei; Cossy, Janine

    2013-08-01

    Polysubstituted 2-(ω-hydroxyalkyl)furans were prepared by tandem Suzuki-Miyaura coupling/acid-catalyzed cyclization starting from appropriately substituted 3-haloallylic alcohols and dihydrofuran-, dihydropyran- or glycal-derived pinacol boronates. PMID:23855589

  4. Acid-catalyzed conversion of mono- and poly-sugars into platform chemicals: effects of molecular structure of sugar substrate.

    Science.gov (United States)

    Hu, Xun; Wu, Liping; Wang, Yi; Song, Yao; Mourant, Daniel; Gunawan, Richard; Gholizadeh, Mortaza; Li, Chun-Zhu

    2013-04-01

    Hydrolysis/pyrolysis of lignocellulosic biomass always produces a mixture of sugars with distinct structures as intermediates or products. This study tried to elucidate the effects of molecular structure of sugars on their acid-catalyzed conversions in ethanol/water. Location of carbonyl group in sugars (fructose versus glucose) and steric configuration of hydroxyl groups (glucose versus galactose) significantly affected yields of levulinic acid/ester (fructose>glucose>galactose). The dehydration of fructose to 5-(hydroxymethyl)furfural produces much less soluble polymer than that from glucose and galactose, which results in high yields of levulinic acid/ester from fructose. Anhydrate sugar such as levoglucosan tends to undergo the undesirable decomposition to form less levulinic acid/ester. Catalytic behaviors of the poly-sugars (sucrose, maltose, raffinose, β-cyclodextrins) were determined much by their basic units. However, their big molecular sizes create the steric hindrance that significantly affects their followed conversion over solid acid catalyst. PMID:23454803

  5. The Formation of Pyrroline and Tetrahydropyridine Rings in Amino Acids Catalyzed by Pyrrolysine Synthase (PylD)

    KAUST Repository

    Quitterer, Felix

    2014-06-10

    The dehydrogenase PylD catalyzes the ultimate step of the pyrrolysine pathway by converting the isopeptide L-lysine-Nε-3R-methyl-D-ornithine to the 22nd proteinogenic amino acid. In this study, we demonstrate how PylD can be harnessed to oxidize various isopeptides to novel amino acids by combining chemical synthesis with enzyme kinetics and X-ray crystallography. The data enable a detailed description of the PylD reaction trajectory for the biosynthesis of pyrroline and tetrahydropyridine rings as constituents of pyrrolysine analogues. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

    OpenAIRE

    Greenhalgh, Mark D.; Thomas, Stephen P.

    2012-01-01

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

  7. Iodine-Catalyzed Decarboxylative Amidation of β,γ-Unsaturated Carboxylic Acids with Chloramine Salts Leading to Allylic Amides.

    Science.gov (United States)

    Kiyokawa, Kensuke; Kojima, Takumi; Hishikawa, Yusuke; Minakata, Satoshi

    2015-10-26

    The iodine-catalyzed decarboxylative amidation of β,γ-unsaturated carboxylic acids with chloramine salts is described. This method enables the regioselective synthesis of allylic amides from various types of β,γ-unsaturated carboxylic acids containing substituents at the α- and β-positions. In the reaction, N-iodo-N-chloroamides, generated by the reaction of a chloramine salt with I2 , function as a key active species. The reaction provides an attractive alternative to existing methods for the synthesis of useful secondary allylic amine derivatives. PMID:26493878

  8. Palladium(II-catalyzed Heck reaction of aryl halides and arylboronic acids with olefins under mild conditions

    Directory of Open Access Journals (Sweden)

    Tanveer Mahamadali Shaikh

    2013-08-01

    Full Text Available A series of general and selective Pd(II-catalyzed Heck reactions were investigated under mild reaction conditions. The first protocol has been developed employing an imidazole-based secondary phosphine oxide (SPO ligated palladium complex (6 as a precatalyst. The catalytic coupling of aryl halides and olefins led to the formation of the corresponding coupled products in excellent yields. A variety of substrates, both electron-rich and electron-poor olefins, were converted smoothly to the targeted products in high yields. Compared with the existing approaches employing SPO–Pd complexes in a Heck reaction, the current strategy features mild reaction conditions and broad substrate scope. Furthermore, we described the coupling of arylboronic acids with olefins, which were catalyzed by Pd(OAc2 and employed N-bromosuccinimide as an additive under ambient conditions. The resulted biaryls have been obtained in moderate to good yields.

  9. Pd-catalyzed ethylene methoxycarbonylation with Brønsted acid ionic liquids as promoter and phase-separable reaction media

    DEFF Research Database (Denmark)

    Garcia-Suarez, Eduardo J.; Khokarale, Santosh Govind; Nguyen van Buu, Olivier;

    2014-01-01

    Brønsted acid ionic liquids (BAILs) were prepared and applied as combined acid promoters and reaction media in Pd–phosphine catalyzed methoxycarbonylation of ethylene to produce methyl propionate. The BAILs served as alternatives to common mineral acids required for the reaction, e.g. methanesulf...

  10. Practical synthesis of enantiomerically pure beta2-amino acids via proline-catalyzed diastereoselective aminomethylation of aldehydes.

    Science.gov (United States)

    Chi, Yonggui; English, Emily P; Pomerantz, William C; Horne, W Seth; Joyce, Leo A; Alexander, Lane R; Fleming, William S; Hopkins, Elizabeth A; Gellman, Samuel H

    2007-05-01

    Proline-catalyzed diastereoselective aminomethylation of aldehydes using a chiral iminium ion, generated from a readily prepared precursor, provides alpha-substituted-beta-amino aldehydes with 85:15 to 90:10 dr. The alpha-substituted-beta-amino aldehydes can be reduced to beta-substituted-gamma-amino alcohols, the major diastereomer of which can be isolated via crystallization or column chromatography. The amino alcohols are efficiently transformed to protected beta2-amino acids, which are valuable building blocks for beta-peptides, natural products, and other interesting molecules. Because conditions for the aminomethylation and subsequent reactions are mild, beta2-amino acid derivatives with protected functional groups in the side chain, such as beta2-homoglutamic acid, beta2-homotyrosine, and beta2-homolysine, can be prepared in this way. The synthetic route is short, and purifications are simple; therefore, this method enables the preparation of protected beta2-amino acids in useful quantities.

  11. (+)-Tartaric Acid-Catalyzed High Regio- and Stereoselective Aminobromination of Olefins%(+)-Tartaric Acid-Catalyzed High Regio- and Stereoselective Aminobromination of Olefins

    Institute of Scientific and Technical Information of China (English)

    陈战国; 魏俊发; 李文丽; 王芸; 赵朋飞; 石先莹

    2011-01-01

    (+)-Tartaric acid-catalyzed aminobromination of α,β-unsaturated ketones, α,β-unsaturated esters and simple olefins utilizing TsNHJNBS as the nitrogen/halogen sources at room temperature without protection of inert gases achieved good yields (up to 92% yield) of vicinal haloamino products with excellent regio- and stereoselectivity, even just 10% of (+)-tartaric acid was used as catalyst. The regio- and stereochemistry was unambiguously confirmed by X-ray structural analysis of products 2b and 12e. The electron-rich and deficient olefins show significant differences in activity to the aminobromination reaction and give the opposite regioselectivities. The 21 cases have been investigated which indicated that our protocol has the advantage of a large scope of olefins. Additionally, tartaric acid as catalyst has the advantage of avoiding any hazardous metals retained in products.

  12. Influence of organic acids on oscillations and waves in the ferroin-catalyzed Belousov-Zhabotinsky reaction

    Science.gov (United States)

    Krüger, Frank; Nagy-Ungvárai, Zsuzsanna; Müller, Stefan C.

    Experiments of the influence of mesoxalic and tartronic acid on the oscillatory behavior and on the spiral tip motion in a ferroin-catalyzed Belousov-Zhabotinsky (BZ) solution are reported. The oscillations were observed in batch and CSTR systems, and for the investigations of the spiral tip motion an open gel reactor was used. A characteristic shoulder in the oscillations is associated with an additional Br - production phase. The chemical parameters for a transition from a hypocycloidal to a circular tip trajectory are found. The findings are compared with the temporal and spatial dynamic behavior, occurring during the ageing process of the solution.

  13. Lewis Acid Catalyzed Friedel-Crafts Alkylation of Alkenes with Trifluoropyruvates.

    Science.gov (United States)

    Xiang, Bin; Xu, Teng-Fei; Wu, Liang; Liu, Ren-Rong; Gao, Jian-Rong; Jia, Yi-Xia

    2016-05-01

    A Friedel-Crafts alkylation reaction of styrenes with trifluoropyruvates has been developed, which delivered allylic alcohols in excellent yields (up to 98%) using the Ni(ClO4)2·6H2O/bipyridine complex as a catalyst. The asymmetric reaction was catalyzed by the chiral Cu(OTf)2/bisoxazoline complex to afford the corresponding chiral allylic alcohols bearing trifluoromethylated quaternary stereogenic centers in moderate enantioselectivities (up to 75% ee). PMID:27028539

  14. Pd-Catalyzed Coupling of γ-C(sp(3))-H Bonds of Oxalyl Amide-Protected Amino Acids with Heteroaryl and Aryl Iodides.

    Science.gov (United States)

    Han, Jian; Zheng, Yongxiang; Wang, Chao; Zhu, Yan; Huang, Zhi-Bin; Shi, Da-Qing; Zeng, Runsheng; Zhao, Yingsheng

    2016-07-01

    Pd-catalyzed regioselective coupling of γ-C(sp(3))-H bonds of oxalyl amide-protected amino acids with heteroaryl and aryl iodides is reported. A wide variety of iodides are tolerated, giving the corresponding products in moderate to good yields. Various oxalyl amide-protected amino acids were compatible in this C-H transformation, thus representing a practical method for constructing non-natural amino acid derivatives. PMID:27286881

  15. Determination of DNA adducts by combining acid-catalyzed hydrolysis and chromatographic analysis of the carcinogen-modified nucleobases.

    Science.gov (United States)

    Leung, Elvis M K; Deng, Kailin; Wong, Tin-Yan; Chan, Wan

    2016-01-01

    The commonly used method of analyzing carcinogen-induced DNA adducts involves the hydrolysis of carcinogen-modified DNA samples by using a mixture of enzymes, followed by (32)P-postlabeling or liquid chromatography (LC)-based analyses of carcinogen-modified mononucleotides/nucleosides. In the present study, we report the development and application of a new approach to DNA adduct analysis by combining the H(+)/heat-catalyzed release of carcinogen-modified nucleobases and the use of LC-based methods to analyze DNA adducts. Results showed that heating the carcinogen-modified DNA samples at 70 °C for an extended period of 4 to 6 h in the presence of 0.05% HCl can efficiently induce DNA depurination, releasing the intact carcinogen-modified nucleobases for LC analyses. After optimizing the hydrolysis conditions, DNA samples with C8- and N (2) -modified 2'-deoxyguanosine, as well as N (6) -modified 2'-deoxyadenosine, were synthesized by reacting DNA with 1-nitropyrene, acetaldehyde, and aristolochic acids, respectively. These samples were then hydrolyzed, and the released nucleobase adducts were analyzed using LC-based analytical methods. Analysis results demonstrated a dose-dependent release of target DNA adducts from carcinogen-modified DNA samples, indicating that the developed H(+)/heat-catalyzed hydrolysis method was quantitative. Comparative studies with enzymatic digestion method on carcinogen-modified DNA samples revealed that the two hydrolysis methods did not yield systematically different results.

  16. Influence of fatty acid on lipase-catalyzed synthesis of ascorbyl esters and their free radical scavenging capacity.

    Science.gov (United States)

    Stojanović, Marija; Carević, Milica; Mihailović, Mladen; Veličković, Dušan; Dimitrijević, Aleksandra; Milosavić, Nenad; Bezbradica, Dejan

    2015-01-01

    Fatty acid (FA) ascorbyl esters are recently emerging food, cosmetic, and pharmaceutical additives, which can be prepared in an eco-friendly way by using lipases as catalysts. Because they are amphiphilic molecules, which possess high free radical scavenging capacity, they can be applied as liposoluble antioxidants as well as emulsifiers and biosurfactants. In this study, the influence of a wide range of acyl donors on ester yield in lipase-catalyzed synthesis and ester antioxidant activity was examined. Among saturated acyl donors, higher yields and antioxidant activities of esters were achieved when short-chain FAs were used. Oleic acid gave the highest yield overall and its ester exhibited a high antioxidant activity. Optimization of experimental factors showed that the highest conversion (60.5%) in acetone was achieved with 5 g L(-1) of lipase, 50 mM of vitamin C, 10-fold molar excess of oleic acid, and 0.7 mL L(-1) of initial water. Obtained results showed that even short- and medium-chain ascorbyl esters could be synthesized with high yields and retained (or even exceeded) free radical scavenging capacity of l-ascorbic acid, indicating prospects of broadening their application in emulsions and liposomes. PMID:25224149

  17. Kinetic Study of Esterification of Acetic Acid with n-butanol and isobutanol Catalyzed by Ion Exchange Resin

    Directory of Open Access Journals (Sweden)

    Amrit Pal Toor

    2011-05-01

    Full Text Available Esters are an important pharmaceutical intermediates and very useful perfumery agents. In this study the esterification of acetic acid with n-butanol and iso-butanol over an acidic cation exchange resin, Amberlyst 15 were carried out. The effects of certain parameters such as temperature, catalyst loading, initial molar ratio between reactants on the rate of reaction were studied. The experiments were conducted in a stirred batch reactor in the temperature range of 351.15 K to 366.15K.Variation of parameters on rate of reaction demonstrated that the reaction was intrinsically controlled.The activation energy for the esterification of acetic acid with n-butanol and iso butanol is found to be 28.45 k J/mol and 23.29 kJ/mol respectively. ©2011 BCREC UNDIP. All rights reserved.(Received: 16th December 2010, Revised: 19th March 2011; Accepted: 7th April 2011[How to Cite: A.P. Toor, M. Sharma, G. Kumar, and R. K. Wanchoo. (2011. Kinetic Study of Esterification of Acetic Acid with n-butanol and isobutanol Catalyzed by Ion Exchange Resin. Bulletin of Chemical Reaction Engineering and Catalysis, 6(1: 23-30. doi:10.9767/bcrec.6.1.665.23-30][How to Link / DOI: http://dx.doi.org/10.9767/bcrec.6.1.665.23-30 || or local: http://ejournal.undip.ac.id/index.php/bcrec/article/view/665 ] | View in 

  18. The Acid Hydrolysis Mechanism of Acetals Catalyzed by a Supramolecular Assembly in Basic Solution

    Energy Technology Data Exchange (ETDEWEB)

    Pluth, Michael D.; Bergman, Robert G.; Raymond, Kenneth N.

    2008-09-24

    A self-assembled supramolecular host catalyzes the hydrolysis of acetals in basic aqueous solution. The mechanism of hydrolysis is consistent with the Michaelis-Menten kinetic model. Further investigation of the rate limiting step of the reaction revealed a negative entropy of activation ({Delta}S{double_dagger} = -9 cal mol{sup -1}K{sup -1}) and an inverse solvent isotope effect (k(H{sub 2}O)/k(D{sub 2}O) = 0.62). These data suggest that the mechanism of hydrolysis that takes place inside the assembly proceeds through an A-2 mechanism, in contrast to the A-1 mechanism operating in the uncatalyzed reaction. Comparison of the rates of acetal hydrolysis in the assembly with the rate of the reaction of unencapsulated substrates reveals rate accelerations of up to 980 over the background reaction for the substrate diethoxymethane.

  19. Effect of polyvinylpyrrolidone on mesoporous silica morphology and esterification of lauric acid with 1-butanol catalyzed by immobilized enzyme

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Jinyu; Zhou, Guowei, E-mail: guoweizhou@hotmail.com; Jiang, Bin; Zhao, Minnan; Zhang, Yan

    2014-05-01

    Mesoporous silica materials with a range of morphology evolution, i.e., from curved rod-shaped mesoporous silica to straight rod-shaped mesoporous silica, were successfully prepared using polyvinylpyrrolidone (PVP) and triblock copolymer as dual template. The effects of PVP molecular weight and concentration on mesoporous silica structure parameters were studied. Results showed that surface area and pore volume continuously decreased with increased PVP molecular weight. Mesoporous silica prepared with PVP K30 also possessed larger pore diameter, interplanar spacing (d{sub 100}), and cell parameter (a{sub 0}) than that prepared with PVP K15 and PVP K90. In addition, with increased PVP concentration, d{sub 100} and a{sub 0} continuously decreased. The mechanism of morphology evolution caused by the change in PVP concentration was investigated. The conversion rate of lauric acid with 1-butanol catalyzed by immobilized Porcine pancreatic lipase (PPL) was also evaluated. Results showed that PPL immobilized on amino-functionalized straight rod-shaped mesoporous silica maintained 50% of its esterification conversion rate even after five cycles of use with a maximum conversion rate was about 90.15%. - Graphical abstract: Curved rod-shaped mesoporous silica can be obtained at low and the highest PVP concentration, while straight rod-shaped mesoporous silica can be obtained at higher PVP concentration. - Highlights: • Mesoporous silica with morphology evolution from CRMS to SRMS were prepared. • Effects of PVP molecular weight and concentration on silica morphology were studied. • A possible mechanism for the formation of morphology evolution SiO{sub 2} was proposed. • Esterification of lauric acid with 1-butanol catalyzed by immobilized PPL.

  20. The Optimized Synthesis of Starch-g-Lactic Acid Copolymer with High Grafting Degree Catalyzed by Sulfuric Acid

    Institute of Scientific and Technical Information of China (English)

    HU Zhiying

    2014-01-01

    The starch-g-lactic acid copolymer was synthesized with catalysis of sulfuric acid by one-step process, and the structure of starch-g-lactic acid copolymer was characterized by means of IR, 13C-NMR, HMBC, XRD, and SEM. The experimental results show that the maximum grafting degree of starch can reach 75%when the starch-g-lactic acid copolymer is activated at 80℃for 2 h and reacted with lactic acid at 90℃for 4 h in vacuum.

  1. Two-step synthesis of fatty acid ethyl ester from soybean oil catalyzed by Yarrowia lipolytica lipase

    Directory of Open Access Journals (Sweden)

    Chen Jinnan

    2011-03-01

    Full Text Available Abstract Background Enzymatic biodiesel production by transesterification in solvent media has been investigated intensively, but glycerol, as a by-product, could block the immobilized enzyme and excess n-hexane, as a solution aid, would reduce the productivity of the enzyme. Esterification, a solvent-free and no-glycerol-release system for biodiesel production, has been developed, and two-step catalysis of soybean oil, hydrolysis followed by esterification, with Yarrowia lipolytica lipase is reported in this paper. Results First, soybean oil was hydrolyzed at 40°C by 100 U of lipase broth per 1 g of oil with approximately 30% to 60% (vol/vol water. The free fatty acid (FFA distilled from this hydrolysis mixture was used for the esterification of FFA to fatty acid ethyl ester by immobilized lipase. A mixture of 2.82 g of FFA and equimolar ethanol (addition in three steps were shaken at 30°C with 18 U of lipase per 1 gram of FFA. The degree of esterification reached 85% after 3 hours. The lipase membranes were taken out, dehydrated and subjected to fresh esterification so that over 82% of esterification was maintained, even though the esterification was repeated every 3 hours for 25 batches. Conclusion The two-step enzymatic process without glycerol released and solvent-free demonstrated higher efficiency and safety than enzymatic transesterification, which seems very promising for lipase-catalyzed, large-scale production of biodiesel, especially from high acid value waste oil.

  2. Mercapturic acid formation and enzyme-catalyzed conjugations with glutathione in pigeons

    NARCIS (Netherlands)

    Wit, J.G.; Leeuwangh, P.

    1969-01-01

    Pigeons are able to metabolize 3,4-dichloronitrobenzene (DCNB) and 2,3,5,6-tetrachloronitrobenzene (TCNB). The main metabolic route for DCNB is reduction of the nitro group and mercapturic acid is a minor metabolite. TCNB is converted to mercapturic acid. High-speed supernatant of pigeon liver conta

  3. C8-Selective Acylation of Quinoline N-Oxides with α-Oxocarboxylic Acids via Palladium-Catalyzed Regioselective C-H Bond Activation.

    Science.gov (United States)

    Chen, Xiaopei; Cui, Xiuling; Wu, Yangjie

    2016-08-01

    A facile and efficient protocol for palladium-catalyzed C8-selective acylation of quinoline N-oxides with α-oxocarboxylic acids has been developed. In this approach, N-oxide was utilized as a stepping stone for the remote C-H functionalization. The reactions proceeded efficiently under mild reaction conditions with excellent regioselectivity and broad functional group tolerance. PMID:27441527

  4. Kinetics and Mechanism of Ruthenium(III) Catalyzed Oxidation of Butanone and Uncatalyzed Oxidation of Cychlohexanone by Cerium(IV) in Acid Sulphate Medium

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Priyamvada; Hemkar, Shalini; Khandelwal, C. L.; Sharma, P. D. [Univ. of Rajasthan, Jaipur (India)

    2012-02-15

    The kinetics of ruthenium(III) chloride catalyzed oxidation of butanone and uncatalyzed oxidation of cyclohexanone by cerium(IV) in sulphuric acid medium have been studied. The kinetic rate law(I) in case of butanone conforms to the proposed mechanism. Kinetics and activation parameters have been evaluated conventionally. Kinetically preferred mode of reaction is via ketonic and not the enolic forms.

  5. Synthesis of Novel Monophosphoramidite Ligands Derived from L-Proline for Rh-catalyzed Asymmetric Hydrogenation of α-Dehydroamino Acid Esters

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Two novel monophosphoramidites were synthesized through a five-step transformation from commercially available L-proline. In the Ph-catalyzed asymmetric hydrogenation of α-dehydroamino acid derivatives, ligand (Sc,Ra)-1b showed good enantioselectivity and up to 91% e.e. was obtained.

  6. Synthesis of solution-phase phosphoramidite and phosphite ligand libraries and their in situ screening in the rhodium-catalyzed asymmetric addition of arylboronic acids

    NARCIS (Netherlands)

    Jagt, Richard B. C.; Toullec, Patrick Y.; Schudde, Ebe P.; de Vries, Johannes G.; Feringa, Ben L.; Minnaard, Adriaan J.

    2007-01-01

    Herein, we report the automated parallel synthesis of solution-phase libraries of phosphoramidite ligands for the development of enantioselective catalysts. The ligand libraries are screened in situ in the asymmetric rhodium-catalyzed addition of arylboronic acids to aldehydes and imines. It is show

  7. Oxidation of saturated hydrocarbons with peroxyacetic acid catalyzed by vanadium complexes

    OpenAIRE

    Gonzalez Cuervo, Laura; Kozlov, Yuriy N.; Süss-Fink, Georg; Shul’pin, Georgiy B.

    2009-01-01

    Peroxyacetic acid (PAA) oxidizes alkanes in acetonitrile or acetic acid at 60 °C if a soluble vanadium(V) salt, n-Bu4NVO3 (1), is used as a catalyst. Corresponding ketones, alcohols and alkyl hydroperoxides are the main products. Methane, ethane, propane, cyclohexane, and other higher alkanes were substrates in the oxidations. The proposed mechanism involves the formation of a complex between (1) and PAA with equilibrium constants 3.3 and 6.8 dm3 mol−1 for acetonitrile and acetic acid as solv...

  8. Acid-catalyzed steam pretreatment of lodgepole pine and subsequent enzymatic hydrolysis and fermentation to ethanol.

    Science.gov (United States)

    Ewanick, Shannon M; Bura, Renata; Saddler, John N

    2007-11-01

    Utilization of ethanol produced from biomass has the potential to offset the use of gasoline and reduce CO(2) emissions. This could reduce the effects of global warming, one of which is the current outbreak of epidemic proportions of the mountain pine beetle (MPB) in British Columbia (BC), Canada. The result of this is increasing volumes of dead lodgepole pine with increasingly limited commercial uses. Bioconversion of lodgepole pine to ethanol using SO(2)-catalyzed steam explosion was investigated. The optimum pretreatment condition for this feedstock was determined to be 200 degrees C, 5 min, and 4% SO(2) (w/w). Simultaneous saccharification and fermentation (SSF) of this material provided an overall ethanol yield of 77% of the theoretical yield from raw material based on starting glucan, mannan, and galactan, which corresponds to 244 g ethanol/kg raw material within 30 h. Three conditions representing low (L), medium (M), and high (H) severity were also applied to healthy lodgepole pine. Although the M severity conditions of 200 degrees C, 5 min, and 4% SO(2) were sufficiently robust to pretreat healthy wood, the substrate produced from beetle-killed (BK) wood provided consistently higher ethanol yields after SSF than the other substrates tested. BK lodgepole pine appears to be an excellent candidate for efficient and productive bioconversion to ethanol.

  9. Enantioselective synthesis of benzazepinoindoles bearing trifluoromethylated quaternary stereocenters catalyzed by chiral spirocyclic phosphoric acids.

    Science.gov (United States)

    Li, Xuejian; Chen, Di; Gu, Haorui; Lin, Xufeng

    2014-07-18

    The first highly enantioselective iso-Pictet-Spengler reaction of C-2-linked o-aminobenzylindoles with trifluoromethyl ketones was developed using chiral spirocyclic phosphoric acids as organocatalysts, which afforded optically active benzazepinoindoles bearing trifluoromethylated quaternary stereocenters. PMID:24890313

  10. Sulfanilic acid catalyzed solvent-free synthesis of 1,5-benzodiazepine derivatives

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Sulfanilic acid has been found to be an efficient catalyst for the synthesis of 1,5-benzodiazepines from o-phenylenediamine and ketones. This method is simple, effective and environmentally friendly and gives better yields.

  11. Acid Catalyzed Condensation of Phenylethanal Enol or Thiol Enol Ether to 2-Phenylnaphthalene

    Institute of Scientific and Technical Information of China (English)

    CHANG, Yu-An

    2007-01-01

    Treatment of enol ether or thiol enol ether of phenylethanals with sulfuric or polyphosphoric acid in toluene or xylene gave 2-phenylnaphthalene in good yield. More importantly, a one-pot reaction has been developed.

  12. Regiospecific O-methylation of naphthoic acids catalyzed by NcsB1, an O-methyltransferase involved in the biosynthesis of the enediyne antitumor antibiotic neocarzinostatin.

    Science.gov (United States)

    Luo, Yinggang; Lin, Shuangjun; Zhang, Jian; Cooke, Heather A; Bruner, Steven D; Shen, Ben

    2008-05-23

    Neocarzinostatin, a clinical anticancer drug, is the archetypal member of the chromoprotein family of enediyne antitumor antibiotics that are composed of a nonprotein chromophore and an apoprotein. The neocarzinostatin chromophore consists of a nine-membered enediyne core, a deoxyaminosugar, and a naphthoic acid moiety. We have previously cloned and sequenced the neocarzinostatin biosynthetic gene cluster and proposed that the biosynthesis of the naphthoic acid moiety and its incorporation into the neocarzinostatin chromophore are catalyzed by five enzymes NcsB, NcsB1, NcsB2, NcsB3, and NcsB4. Here we report the biochemical characterization of NcsB1, unveiling that: (i) NcsB1 is an S-adenosyl-L-methionine-dependent O-methyltransferase; (ii) NcsB1 catalyzes regiospecific methylation at the 7-hydroxy group of its native substrate, 2,7-dihydroxy-5-methyl-1-naphthoic acid; (iii) NcsB1 also recognizes other dihydroxynaphthoic acids as substrates and catalyzes regiospecific O-methylation; and (iv) the carboxylate and its ortho-hydroxy groups of the substrate appear to be crucial for NcsB1 substrate recognition and binding, and O-methylation takes place only at the free hydroxy group of these dihydroxynaphthoic acids. These findings establish that NcsB1 catalyzes the third step in the biosynthesis of the naphthoic acid moiety of the neocarzinostatin chromophore and further support the early proposal for the biosynthesis of the naphthoic acid and its incorporation into the neocarzinostatin chromophore with free naphthoic acids serving as intermediates. NcsB1 represents another opportunity that can now be exploited to produce novel neocarzinostatin analogs by engineering neocarzinostatin biosynthesis or applying directed biosynthesis strategies. PMID:18387946

  13. Alkylation of Catechol with tert-Butyl Alcohol Catalyzed by Mesoporous Acidic Montmorillonite Heterostructure Catalysts

    Institute of Scientific and Technical Information of China (English)

    周春晖; 葛忠华; 李小年; 童东绅; 李庆伟; 郭红强

    2004-01-01

    The liquid phase alkylation of catechol with tert-butyl alcohol to produce 4-tert-butyl catechol (4-TBC) was carried out over MCM-41, HZSM-5, H-exchanged montmorillonite and novel acidic porous montmorillonite heterostructures (PMHs). Upon all catalysts tested, 4-TBC is the main product and 3-tert-butyl catechol (3-TBC) and 3,5-di-tert-butyl catechol are the side products. The synthetic PMHs showed higher conversion of catechol and better selectivity to 4-TBC compared to other solid acid catalysts tested. Over the PMHs derived from H-exchanged montmorillonite through template extraction processes, the suitable reaction temperature is ca 410 K, the ratio of catechol to tert-butyl alcohol is 1:2. Increasing the amount of catalyst (lower weight hourly space velocity) can improve the conversion of catechol and influence the selectivity slightly. The reasonable reaction time is ca 8 h.The type and strength of acidity of H-montmorillonite and PMH were determined by pyridine adsorption FT-IR and ammonia temperature-programmed desorption techniques. The medium and strong acid sites are conducive to producing 4-TBC and the weak acid sites to facilitating the 3-TBC formation. The differences between the PMHs from calcination and those fi'om extraction are attributed to proton migration and acidity change in the gallery surface.

  14. 菊粉酸降解动力学研究%Kinetic Studies on Acid Catalyzed Hydrolysis of Inulin

    Institute of Scientific and Technical Information of China (English)

    许威; 罗登林; 陈瑞红; 刘建学

    2012-01-01

    通过考察温度、溶液pH值及水分含量对菊粉酸降解的影响,探索菊粉酸水解规律。结果表明:菊粉水溶液在pH 5.0~7.0、温度低于100℃时具有良好的稳定性;但当pH值低于4.0时,菊粉出现明显的水解反应。菊粉溶液在不同温度和pH值下的酸降解动力学表明,其水解反应遵循一级反应动力学方程。利用菊粉凝胶特性考察水分含量与菊粉酸降解的关系,发现相同pH值(pH=3)条件下,水分含量越高,菊粉降解速率越快,凝胶中菊粉降解速率低于菊粉水溶液降解速率。%The effects of temperature,pH and water content on inulin hydrolysis were studied to understand the acid catalyzed hydrolysis process of inulin for industrial production of high-fructose syrup.The results showed that inulin solution had a good thermal stability at a pH value in the range of 5.0-7.0 and a temperature below 100 ℃,while inulin degradation started to occur when the pH was lower than 4.0.The acid catalyzed hydrolysis dynamics of inulin at different levels of temperature and pH showed that the reaction followed the first-order kinetics well.The relation between inulin gel degradation induced by acid and water content was also investigated.At the same pH,the higher water content,the faster inulin hydrolysis,and the degradation rate of inulin was lower in gel than in aqueous solution.

  15. Synthesis of ascorbyl oleate by transesterification of olive oil with ascorbic acid in polar organic media catalyzed by immobilized lipases.

    Science.gov (United States)

    Moreno-Perez, Sonia; Filice, Marco; Guisan, Jose M; Fernandez-Lorente, Gloria

    2013-09-01

    The reaction of transesterification between oils (e.g., olive oil) and ascorbic acid in polar anhydrous media (e.g., tert-amyl alcohol) catalyzed by immobilized lipases for the preparation of natural liposoluble antioxidants (e.g., ascorbyl oleate) was studied. Three commercial lipases were tested: Candida antarctica B lipase (CALB), Thermomyces lanuginosus lipase (TLL) and Rhizomucor miehei lipase (RML). Each lipase was immobilized by three different protocols: hydrophobic adsorption, anionic exchange and multipoint covalent attachment. The highest synthetic yields were obtained with CALB adsorbed on hydrophobic supports (e.g., the commercial derivative Novozym 435). The rates and yields of the synthesis of ascorbyl oleate were higher when using the solvent dried with molecular sieves, at high temperatures (e.g. 45°C) and with a small excess of oil (2 mol of oil per mol of ascorbic acid). The coating of CALB derivatives with polyethyleneimine (PEI) improved its catalytic behavior and allowed the achievement of yields of up to 80% of ascorbyl oleate in less than 24h. CALB adsorbed on a hydrophobic support and coated with PEI was 2-fold more stable than a non-coated derivative and one hundred-fold more stable than the best TLL derivative. The best CALB derivative exhibited a half-life of 3 days at 75°C in fully anhydrous media, and this derivative maintained full activity after 28 days at 45°C in dried tert-amyl alcohol. PMID:23891831

  16. Enhancement of Lipase-catalyzed Synthesis of Caffeic Acid Phenethyl Ester in Ionic Liquid with DMSO Co-solvent☆

    Institute of Scientific and Technical Information of China (English)

    Shuangshuang Gu; Jun Wang; Xianbin Wei; Hongsheng Cui; Xiangyang Wu; Fuan Wu

    2014-01-01

    Caffeic acid phenethyl ester (CAPE) is a natural and rare ingredient with several biological activities, but its indus-trial production using lipase-catalyzed esterification of caffeic acid (CA) and 2-phenylethanol (PE) in ionic liquids (ILs) is hindered by low substrate concentrations and long reaction time. To set up a high-efficiency bioprocess for production of CAPE, a novel dimethyl sulfoxide (DMSO)–IL co-solvent system was established in this study. The 2%(by volume) DMSO–[Bmim][Tf2N] system was found to be the best medium with higher substrate solu-bility and conversion of CA. Under the optimum conditions, the substrate concentration of CA was raised 8-fold, the reaction time was reduced by half, and the conversion reached 96.23%. The kinetics follows a ping-pong bi-bi mechanism with inhibition by PE, with kinetic parameters as follows:Vmax=0.89 mmol · min−1 · g−1, Km,CA=42.9 mmol · L−1, Km,PE=165.7 mmol · L−1, and Ki,PE=146.2 mmol · L−1. The results suggest that the DMSO co-solvent effect has great potential to enhance the enzymatic synthesis efficiency of CAPE in ILs.

  17. Phenylalanine ammonia lyase catalyzed synthesis of amino acids by an MIO-cofactor independent pathway.

    Science.gov (United States)

    Lovelock, Sarah L; Lloyd, Richard C; Turner, Nicholas J

    2014-04-25

    Phenylalanine ammonia lyases (PALs) belong to a family of 4-methylideneimidazole-5-one (MIO) cofactor dependent enzymes which are responsible for the conversion of L-phenylalanine into trans-cinnamic acid in eukaryotic and prokaryotic organisms. Under conditions of high ammonia concentration, this deamination reaction is reversible and hence there is considerable interest in the development of PALs as biocatalysts for the enantioselective synthesis of non-natural amino acids. Herein the discovery of a previously unobserved competing MIO-independent reaction pathway, which proceeds in a non-stereoselective manner and results in the generation of both L- and D-phenylalanine derivatives, is described. The mechanism of the MIO-independent pathway is explored through isotopic-labeling studies and mutagenesis of key active-site residues. The results obtained are consistent with amino acid deamination occurring by a stepwise E1 cB elimination mechanism.

  18. Electro-oxidation of ascorbic acid catalyzed on cobalt hydroxide-modified glassy carbon electrode

    Directory of Open Access Journals (Sweden)

    GHASEM KARIM-NEZHAD

    2009-05-01

    Full Text Available The electrochemical behavior of ascorbic acid on a cobalt hydroxide modified glassy carbon (CHM–GC electrode in alkaline solution was investigated. The process of the involved oxidation and its kinetics were established using the cyclic voltammetry, chronoamperometry techniques, as well as by steady state polarization measurements. The results revealed that cobalt hydroxide promotes the rate of oxidation by increasing the peak current; hence ascorbic acid is oxidized at lower potentials, which is thermodynamically more favorable. The cyclic voltammograms and chronoamperometry indicate a catalytic EC mechanism is operative with the electrogeneration of Co(IV as the electrochemical process. Also, the process is diffusion-controlled and the current–time responses follow Cottrellian behavior. This result was confirmed by steady state measurements. The rate constants of the catalytic oxidation of ascorbic acid and the electron-transfer coefficient are reported.

  19. Convenient synthetic method of starch/lactic acid graft copolymer catalyzed with sodium hydroxide

    Indian Academy of Sciences (India)

    Qingling Wang; Yingmo Hu; Jianhua Zhu; Yang Liu; Xue Yang; Jing Bian

    2012-06-01

    Copolymer of starch grafted with lactic acid (LA) could be directly prepared by reaction of cornstarch with lactic acid and with sodium hydroxide (NaOH) as the catalyst. The structure of starch/LA copolymer was characterized by IR, XRD, SEM and 1H-NMR. The effects of NaOH concentration, ratios of starch and LA, reaction temperature and reaction time on the grafting degree were also investigated and the results showed that the highest grafting degree of starch could reach 33.60% when the graft copolymerization was carried out in 0.40 mol l-1 NaOH aqueous solution for 9 h at 90°C with 1: 6 ratio of starch and lactic acid.

  20. Lipase catalyzed synthesis of neutral glycerides rich in micronutrients from rice bran oil fatty acid distillate.

    Science.gov (United States)

    Nandi, Sumit; Gangopadhyay, Sarbani; Ghosh, Santinath

    2008-01-01

    Neutral glycerides with micronutrients like sterols, tocopherols and squalene may be prepared from cheap raw material like rice bran oil fatty acid distillate (RBO FAD). RBO FAD is an important byproduct of vegetable oil refining industries in the physical refining process. Glycerides like triacylglycerols (TAG), diacylglycerols (DAG) and monoacylglycerols (MAG) containing significant amounts of unsaponifiable matter like sterols, tocopherols and hydrocarbons (mainly squalene) may certainly be considered as novel functional food ingredients. Fatty acids present in RBO FAD were esterified with glycerol of varying amount (1:0.33, 1:0.5, 1:1 and 1:1.5 of FAD : glycerol ratio) for 8 h using non-specific enzyme NS 40013 (Candida antartica). After esterification the product mixture containing mono, di- and triglycerides was purified by molecular distillation to remove excess free fatty acids and also other volatile undesirable components. The purified product containing sterols, tocopherols and squalene can be utilized in various food formulations.

  1. Brønsted acid ionic liquid catalyzed formation of pyruvaldehyde dimethylacetal from triose sugars

    DEFF Research Database (Denmark)

    Shunmugavel, Saravanamurugan; Riisager, Anders

    2013-01-01

    A series of sulfonic acid functionalized ionic liquids (SO3H-ILs) have been synthesized, characterized and investigated as catalysts for the conversion of the triose sugars, 1,3-dihydroxyacetone (DHA) and glyceraldehyde (GLA), to pyruvaldehyde dimethylacetal (PADA) in methanol. Depending on the r......A series of sulfonic acid functionalized ionic liquids (SO3H-ILs) have been synthesized, characterized and investigated as catalysts for the conversion of the triose sugars, 1,3-dihydroxyacetone (DHA) and glyceraldehyde (GLA), to pyruvaldehyde dimethylacetal (PADA) in methanol. Depending...

  2. ESTERIFICATION OF ACRYLIC ACID WITH 1-BUTANOL IN LIQUID PHASE CATALYZED WITH AL-MCM-41

    OpenAIRE

    Edson Avellaneda Maytán; Gustavo Paim Valença

    2010-01-01

    This work studies the esterification of acrylic acid with 1-butanol using Al-MCM-41 as catalyst with different degrees of acidity at different temperatures. Al-MCM-41 synthesis was made from bromate Cetyl trimethyl ammonium using as router agent, NH4OH (25%), deionized H2O and Al2(SO4)3. Catalytic tests were carried out by groups and worked with temperature ranges among (333 to 348) K and a small sample was collected at predetermined intervals of time for subsequent gas chromatography analysi...

  3. Preparation of fructone catalyzed by water-soluble Br(φ)nsted acid ionic liquids

    Institute of Scientific and Technical Information of China (English)

    Yuan Yuan Wang; Rong Wang; Liang Chun Wu; Li Yi Dai

    2007-01-01

    Fructone (2-methyl-2-ethylacetoacetate-1,3-dioxolane), a flavouring material, has been synthesized from ethyl acetoacetate and glycol using five water-soluble Br(φ)nsted acid ionic liquids as catalysts for the first time. The used Br(φ)nsted acid ionic liquids include [Hmim]Tfa, [Hmim]Tsa, [Hmim]BF4, [Bmim]HSO4, [Bmim]H2PO4, and [Hmim]BF4 showed the highest catalytic activity for the preparation of fructone. After reaction, the product could be isolated from the reaction system automatically, and the ionic liquid could be directly reused without dehydration.

  4. Lipase-catalyzed synthesis of oligoesters of 2,5-furandicarboxylic acid with aliphatic diols

    NARCIS (Netherlands)

    Cruz-Izquierdo, Álvaro; Broek, van den Lambertus A.M.; Serra, Juan L.; Llama, María J.; Boeriu, Carmen G.

    2015-01-01

    2,5-Furandicarboxylic acid is a platform chemical for the production of biobased polymers and materials. This study reports the synthesis of furan oligoesters via polytransesterification of dimethyl furan-2,5-dicarboxylate and linear α, ω-aliphatic diols with chain length ranging from C2 to C12,

  5. Studies concerning the anion ex-change resins catalyzed esterification of epichlorohydrin with organic acids

    Directory of Open Access Journals (Sweden)

    E.I. Muresan

    2009-09-01

    Full Text Available The paper studies the esterification of carboxylic acids with epichlorohydrin over two macroporous strong base anion exchange resins with different polymer matrix. For both resins, the influence of reaction parameters (temperature, catalyst loading, molar ratio on the reaction rate and the yields of the two isomeric esters were investigated.

  6. Lewis-acid catalyzed depolymerization of Protobind lignin in supercritical water and ethanol

    NARCIS (Netherlands)

    Guvenatam, Burcu; Heeres, Erik H.J.; Pidko, Evgeny A.; Hensen, Ernie J. M.

    2016-01-01

    The use of metal acetates, metal chlorides and metal triflates as Lewis acid catalysts for the depolymerization of soda lignin under supercritical conditions was investigated. The reactions were carried out at 400 degrees C in water and ethanol. Lignin conversion in supercritical water led to format

  7. Tannic acid Catalyzed an Efficient Synthesis of 2,4,5-Triaryl-1H-Imidazole

    Directory of Open Access Journals (Sweden)

    Shitole Nana Vikram

    2013-05-01

    Full Text Available Tannic acid (C76H52O46 has been found to be an efficient catalyst for one-pot synthesis of 2,4,5-triaryl substituted imidazoles by the reaction of an arylaldehyde, benzyl/benzoin and an ammonium acetate. The short reaction time and excellent yields making this protocol practical and economically attractive.

  8. Nonmetal catalyzed insertion reactions of diazocarbonyls to acid derivatives in fluorinated alcohols.

    Science.gov (United States)

    Dumitrescu, Lidia; Azzouzi-Zriba, Kaouther; Bonnet-Delpon, Danièle; Crousse, Benoit

    2011-02-18

    The insertion reaction of diazocarbonyls to acids could be performed smoothly in fluorinated alcohols in the absence of metal catalyst. This new procedure allowed the chemoselective preparation of various functionalized compounds such as acyloxyesters, depsipeptides, and sulfonate, phosphonate, or boronate derivatives.

  9. Mass transfer effects in the H2SO4 catalyzed pivalic acid synthesis

    NARCIS (Netherlands)

    Brilman, D.W.F.; Meesters, N.G.; Swaaij, W.P.M. van; Versteeg, G.F.

    2001-01-01

    The synthesis of carboxylic acids from alkenes, carbon monoxide and water according to the Koch process is usually carried out in a stirred gas–liquid–liquid multiphase reactor. Due to the complex reaction system with fast, equilibrium reactions and fast, irreversible reactions the yield and product

  10. Lewis base additives improve the zeolite ferrierite-catalyzed synthesis of isostearic acid

    Science.gov (United States)

    Isostearic acid (IA) is of interest for industrial purposes especially in the area of biolubricants, such as cosmetics and slip additives for polyolefin and related copolymer films. This study was designed to develop a zeolitic catalysis process for IA production through isomerization of fatty aci...

  11. Oxalic acid catalyzed solvent-free one pot synthesis of coumarins

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Oxalic acid was found to be an efficient catalyst for Pechmann condensation, which includes the reaction between phenols and β-keto esters leading to formation of coumarin derivatives. The advantages of present methods are the use of cheap and easy available catalyst, solvent-free reaction conditions, better yields and shorter reaction time.

  12. Coupling of Carbon Dioxide with Epoxides Catalyzed by Amino Acid Hydrochloride Salts

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Using amino acid hydrochloride salt as a catalyst, the coupling reaction of CO2 with epoxides could proceed smoothly to give cyclic carbonates in very good yields and high selectivity. The reaction conditions such as the pressure of carbon dioxide, reaction temperature, time and catalyst loading were carefully investigated.

  13. INTERESTERIFICATION OF MILK-FAT WITH OLEIC-ACID CATALYZED BY IMMOBILIZED RHIZOPUS-ORYZAE LIPASE

    NARCIS (Netherlands)

    OBA, T; WITHOLT, B

    1994-01-01

    Milk fat was interesterified with oleic acid by catalysis of an immobilized lipase in a microaqueous two-phase system. A commercial lipase from Rhizopus oryzae and a controlled pore glass carrier were selected for preparation of an immobilized lipase. The prepared immobilized lipase showed a Michael

  14. Imidase catalyzing desymmetric imide hydrolysis forming optically active 3-substituted glutaric acid monoamides for the synthesis of gamma-aminobutyric acid (GABA) analogs.

    Science.gov (United States)

    Nojiri, Masutoshi; Hibi, Makoto; Shizawa, Hiroaki; Horinouchi, Nobuyuki; Yasohara, Yoshihiko; Takahashi, Satomi; Ogawa, Jun

    2015-12-01

    The recent use of optically active 3-substituted gamma-aminobutyric acid (GABA) analogs in human therapeutics has identified a need for an efficient, stereoselective method of their synthesis. Here, bacterial strains were screened for enzymes capable of stereospecific hydrolysis of 3-substituted glutarimides to generate (R)-3-substituted glutaric acid monoamides. The bacteria Alcaligenes faecalis NBRC13111 and Burkholderia phytofirmans DSM17436 were discovered to hydrolyze 3-(4-chlorophenyl) glutarimide (CGI) to (R)-3-(4-chlorophenyl) glutaric acid monoamide (CGM) with 98.1% enantiomeric excess (e.e.) and 97.5% e.e., respectively. B. phytofirmans DSM17436 could also hydrolyze 3-isobutyl glutarimide (IBI) to produce (R)-3-isobutyl glutaric acid monoamide (IBM) with 94.9% e.e. BpIH, an imidase, was purified from B. phytofirmans DSM17436 and found to generate (R)-CGM from CGI with specific activity of 0.95 U/mg. The amino acid sequence of BpIH had a 75% sequence identity to that of allantoinase from A. faecalis NBRC13111 (AfIH). The purified recombinant BpIH and AfIH catalyzed (R)-selective hydrolysis of CGI and IBI. In addition, a preliminary investigation of the enzymatic properties of BpIH and AfIH revealed that both enzymes were stable in the range of pH 6-10, with an optimal pH of 9.0, stable at temperatures below 40 °C, and were not metalloproteins. These results indicate that the use of this class of hydrolase to generate optically active 3-substituted glutaric acid monoamide could simplify the production of specific chiral GABA analogs for drug therapeutics.

  15. Kinetics of cytochrome P450 2E1-catalyzed oxidation of ethanol to acetic acid via acetaldehyde.

    Science.gov (United States)

    Bell-Parikh, L C; Guengerich, F P

    1999-08-20

    The P450 2E1-catalyzed oxidation of ethanol to acetaldehyde is characterized by a kinetic deuterium isotope effect that increases K(m) with no effect on k(cat), and rate-limiting product release has been proposed to account for the lack of an isotope effect on k(cat) (Bell, L. C., and Guengerich, F. P. (1997) J. Biol. Chem. 272, 29643-29651). Acetaldehyde is also a substrate for P450 2E1 oxidation to acetic acid, and k(cat)/K(m) for this reaction is at least 1 order of magnitude greater than that for ethanol oxidation to acetaldehyde. Acetic acid accounts for 90% of the products generated from ethanol in a 10-min reaction, and the contribution of this second oxidation has been overlooked in many previous studies. The noncompetitive intermolecular kinetic hydrogen isotope effects on acetaldehyde oxidation to acetic acid ((H)(k(cat)/K(m))/(D)(k(cat)/K(m)) = 4.5, and (D)k(cat) = 1.5) are comparable with the isotope effects typically observed for ethanol oxidation to acetaldehyde, and k(cat) is similar for both reactions, suggesting a possible common catalytic mechanism. Rapid quench kinetic experiments indicate that acetic acid is formed rapidly from added acetaldehyde (approximately 450 min(-1)) with burst kinetics. Pulse-chase experiments reveal that, at a subsaturating concentration of ethanol, approximately 90% of the acetaldehyde intermediate is directly converted to acetic acid without dissociation from the enzyme active site. Competition experiments suggest that P450 2E1 binds acetic acid and acetaldehyde with relatively high K(d) values, which preclude simple tight binding as an explanation for rate-limiting product release. The existence of a rate-determining step between product formation and release is postulated. Also proposed is a conformational change in P450 2E1 occurring during the course of oxidation and the discrimination of P450 2E1 between acetaldehyde and its hydrated form, the gem-diol. This multistep P450 reaction is characterized by kinetic

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

    Science.gov (United States)

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

    2016-05-11

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

  17. Hydrolysis of Selected Tropical Plant Wastes Catalyzed by a Magnetic Carbonaceous Acid with Microwave

    Science.gov (United States)

    Su, Tong-Chao; Fang, Zhen; Zhang, Fan; Luo, Jia; Li, Xing-Kang

    2015-12-01

    In this study, magnetic carbonaceous acids were synthesized by pyrolysis of the homogeneous mixtures of glucose and magnetic Fe3O4 nanoparticles, and subsequent sulfonation. The synthesis conditions were optimized to obtain a catalyst with both high acid density (0.75 mmol g-1) and strong magnetism [magnetic saturation, Ms = 19.5 Am2 kg-1]. The screened catalyst (C-SO3H/Fe3O4) was used to hydrolyze ball-milled cellulose in a microwave reactor with total reducing sugar (TRS) yield of 25.3% under the best conditions at 190 °C for 3.5 h. It was cycled for at least seven times with high catalyst recovery rate (92.8%), acid density (0.63 mmol g-1) and magnetism (Ms = 12.9 Am2 kg-1), as well as high TRS yield (20.1%) from the hydrolysis of ball-milled cellulose. The catalyst was further successfully tested for the hydrolysis of tropical biomass with high TRS and glucose yields of 79.8% and 58.3% for bagasse, 47.2% and 35.6% for Jatropha hulls, as well as 54.4% and 35.8% for Plukenetia hulls.

  18. Phenylsulfonic Acid Functionalized Mesoporous Silica Catalyzed Transetherification of Alcohols with Dimethoxymethane

    Institute of Scientific and Technical Information of China (English)

    杨建明; 吕剑

    2005-01-01

    Phenylsulfonic acid functionalized mesoporous silica was synthesized by condensation of tetraethylorthosilicate with phenyltrimethoxysilane, and then sulfonation using 30% fuming sulfuric acid. The material was characterized using FT-IR, DSC, XPS, TEM and N2 adsorption/desorption measurements. DSC revealed that sulfonic acid group of the catalyst was decomposed at 354.8℃, indicating that the catalyst exhibited high thermal stability. XPS showed that there existed three kinds of different silicon species on surface of the catalyst. The catalytic performance of the catalyst was evaluated using transetherification of alcohols with dimethoxymethane. It was found that among primary alcohols, the selectivities of the two long-chain alcohols for n-dedocanol and n-tetradecyl alcohol were higher than 97.0% at the conversions of 43.6% and 65.3%, respectively, while the selectivities of the short-chain alcohols except for n-hexanol were less than 90.0% at the conversions of over 80.0%. Due to steric bartier, the secondary alcohols such as /so-butanol and cyclohexanol afforded conversions of 79.4% and 60.5%, and the selectivities of the two alcohols were more than 90.0%. The sequence in conversion of the substituted phenols isas follows: p-nitrophenol>p-fluorophenol≥p-bromophenol>p-cresol>m-cresol.

  19. Asymmetric Aldol Reaction Catalyzed by L-Proline and Achiral Thiourea Fluoroboric Acid Salt

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Eun; Lee, Haney; Kim, Taek Hyeon [Chonnam National University, Gwangju (Korea, Republic of)

    2015-01-15

    Considering its ready availability and low cost, L-proline would be the first choice catalyst for preparing aldol adducts with high diastereo- and enantioselectivity. However, proline presents some major drawbacks, including poor performance in direct aldol reactions with aromatic aldehydes, limited solubility, and reactivity in nonpolar organic solvents, and side reactions that make using high catalyst loadings necessary to reach satisfactory conversions. Therefore, numerous proline-modified organo catalysts such as prolinamides, proline thioamides, sulfonamides, chiral amines, and organic salts have been designed for direct aldol reactions. An alternative is to add a readily available additive to the reactions containing proline. This last approach is clearly advantageous in avoiding tedious chemical syntheses of organo catalysts and would ultimately allow the construction of libraries of catalyst protocols by simply changing the additive. Acid additives can influence the outcome of enamine mediated reactions; however, only a few screening studies of acid additions to thiourea organo catalysts are available in the literature. The reaction between cyclohexanone and 4-nitrobenzaldehyde was selected as a standard model reaction for screening of more effective acid additives to thiourea.

  20. Phase Transfer Catalyzed Synthesis of Thiosemicarbazide Derivatives of 2-ethoxybenzoic Acid

    Institute of Scientific and Technical Information of China (English)

    WEI TaiBao; ZHANG YouMing; WU JiaWei

    2001-01-01

    @@ A series of 1,4-disubstitued thiosemicarbazides and their related heterocyclic compounds have been found to possess important biological activities[1]. Some thiosemicarbazides have been found to be useful as herbicides, insecticides and plant-growth regulators [1]. In view of these and in continuation of our earlier work on the synthesis and biological activity of thiosemicarbaides derivatives [2], we now report a convenient and efficient method for the preparation of thiosemicarbazides derivatives of 2-ethoxybenzoic acid under the condition of solid-liquid phase transfer catalysis using PEG-400 as the catalyst.

  1. Phase Transfer Catalyzed Synthesis of Thiosemicarbazide Derivatives of 2-ethoxybenzoic Acid

    Institute of Scientific and Technical Information of China (English)

    WEI; TaiBao

    2001-01-01

    A series of 1,4-disubstitued thiosemicarbazides and their related heterocyclic compounds have been found to possess important biological activities[1]. Some thiosemicarbazides have been found to be useful as herbicides, insecticides and plant-growth regulators [1]. In view of these and in continuation of our earlier work on the synthesis and biological activity of thiosemicarbaides derivatives [2], we now report a convenient and efficient method for the preparation of thiosemicarbazides derivatives of 2-ethoxybenzoic acid under the condition of solid-liquid phase transfer catalysis using PEG-400 as the catalyst.  ……

  2. Lipase-catalyzed esterification of lactic acid with straight-chain alcohols

    DEFF Research Database (Denmark)

    Rønne, Torben Harald; Xu, Xuebing; Tan, Tianwei

    2005-01-01

    Candida antarctica lipase B (Novozym 435) as well as the textile-immobilized Candida sp. lipase. A method was established to obtain ester yields in the range of 71 to 82% for the different alcohols, and the most favorable conditions for the esterification reaction using Novozym 435 were an equimolar ratio......% of Novozym 435. The immobilized Candida sp. lipase prepared in the laboratory also could be used to produce esters of lactic acid and straight-chain alcohols, but it had a much lower activity than Novozym 435 with a temperature optimum of 40°C....

  3. Self-catalyzed syntheses, structural characterization, DPPH radical scavenging-, cytotoxicity-, and DFT studies of phenoxyaliphatic acids of 1,8-dioxo-octahydroxanthene derivatives

    Science.gov (United States)

    Suresh Kumar, G. S.; Antony Muthu Prabhu, A.; Seethalashmi, P. G.; Bhuvanesh, N.; Kumaresan, S.

    2014-02-01

    One-pot, in-water syntheses of phenoxyaliphatic acids of 1,8-dioxo-octahydroxanthene derived from dimedone and formylphenoxyaliphatic acids are reported. Geometries of compounds 2b, 2c, and 5a have been examined crystallographically. The synthesized compounds showed better DPPH radical scavenging activity and cytotoxicity against A431 cancer cell line. The molecular properties of all synthesized xanthenes have been investigated using single crystal XRD and DFT method. Self-catalyzed Bronsted-Lowry acid catalytic behavior was also investigated by both experimental and theoretical methods.

  4. Effect of polyvinylpyrrolidone on mesoporous silica morphology and esterification of lauric acid with 1-butanol catalyzed by immobilized enzyme

    Science.gov (United States)

    Zhang, Jinyu; Zhou, Guowei; Jiang, Bin; Zhao, Minnan; Zhang, Yan

    2014-05-01

    Mesoporous silica materials with a range of morphology evolution, i.e., from curved rod-shaped mesoporous silica to straight rod-shaped mesoporous silica, were successfully prepared using polyvinylpyrrolidone (PVP) and triblock copolymer as dual template. The effects of PVP molecular weight and concentration on mesoporous silica structure parameters were studied. Results showed that surface area and pore volume continuously decreased with increased PVP molecular weight. Mesoporous silica prepared with PVP K30 also possessed larger pore diameter, interplanar spacing (d100), and cell parameter (a0) than that prepared with PVP K15 and PVP K90. In addition, with increased PVP concentration, d100 and a0 continuously decreased. The mechanism of morphology evolution caused by the change in PVP concentration was investigated. The conversion rate of lauric acid with 1-butanol catalyzed by immobilized Porcine pancreatic lipase (PPL) was also evaluated. Results showed that PPL immobilized on amino-functionalized straight rod-shaped mesoporous silica maintained 50% of its esterification conversion rate even after five cycles of use with a maximum conversion rate was about 90.15%.

  5. 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.

  6. Biomimetic Fenton-catalyzed lignin depolymerization to high-value aromatics and dicarboxylic acids.

    Science.gov (United States)

    Zeng, Jijiao; Yoo, Chang Geun; Wang, Fei; Pan, Xuejun; Vermerris, Wilfred; Tong, Zhaohui

    2015-03-01

    By mimicking natural lignin degradation systems, the Fenton catalyst (Fe(3+), H2O2) can effectively facilitate lignin depolymerization in supercritical ethanol (7 MPa, 250 °C) to give organic oils that consist of mono- and oligomeric aromatics, phenols, dicarboxylic acids, and their derivatives in yields up to (66.0±8.5) %. The thermal properties, functional groups, and surface chemistry of lignin before and after Fenton treatment were examined by thermogravimetric analysis, pyrolysis-gas chromatography-mass spectrometry, (31)P NMR spectroscopy, and X-ray photoelectron spectroscopy. The results suggest that the Fenton catalyst facilitates lignin depolymerization through cleavage of β-ether bonds between lignin residues. The formation of a lignin-iron chelating complex effectively depresses lignin recondensation; thus minimizing charcoal formation and enhancing the yield of liquid products.

  7. Synthesis of 5-hydroxymethylfurfural (HMF) by acid catalyzed dehydration of glucose-fructose mixtures

    DEFF Research Database (Denmark)

    Pedersen, Asbjørn Toftgaard; Ringborg, Rolf Hoffmeyer; Grotkjær, Thomas;

    2015-01-01

    -products: soluble humins, glucose dimers, anhydroglucose, and formic acid. The reaction conditions in four different reactor configurations were optimized and compared using the kinetic model. It was found that a recirculating reactor setup is preferable, where the equilibrium controlled by-products (anhydroglucose...... a detailed experimental investigation a reaction network was proposed, and subsequently the corresponding kinetic model was fitted to experimental data in order to obtain estimates of the reaction kinetic parameters. The kinetic model is capable of predicting the formation of HMF along with the important by...... and glucose dimers) are recirculated to the dehydration reactor. The model predicts an HMF selectivity of close to 70% in a recirculating reactor at conditions where HMF degradation is avoided....

  8. Hydrogenation of phenylpyruvic acid to phenylalanine catalyzed by Ni-B/SiO2

    Institute of Scientific and Technical Information of China (English)

    Qunfang Liang; Aiqing Zhang; Lin Li

    2008-01-01

    Phenylalanine(Phe)is a significant amino acid that cannot be synthesized by human themselves but must be taken from environment.It was initially found that the nanosized amorphous Ni-B/SiO2 alloy prepared by the chemical reduction method was an effective catalyst for the preparation of Phe from phenylpyruvic acid(PPA)by amination and hydrogenation.It has been found that the amorphous Ni-B/SiO2 alloy catalyst exhibits superior activity and selectivity to the traditional catalysts Raney Nj and Urushibara nickel.The effects of reaction time.amounts of catalysts and ammonia solution,reaction temperature,and H2 pressure on the reaction have been investigated systematically.The results indicated that the yield of Phe was 97.9%.and the selectivity for Phe reached 98.9%when the reaction was carried out for 3 h at 333 K and 2.0 Mpa of H2 with m(Cat.):m(PPA)=0.6:1.0 and n(NH3):n(PPA)=3:1.The catalysts were characterized by XRD,AAS,XPS,BET,and TEM.and the relationship between the catalyst structure and the catalytic activity was discussed in detail.It was found that the reason why Ni-B/SiO2 amorphous alloy catalyst was much more active for the preparation of Phe could be accounted for by the presence of electron-rich Ni due to electron donation from alloying B:the smaller size of Ni-B particles,the larger specific surface area of Ni-B/SiO2.

  9. Efficient Lewis Acids Catalyzed Aza-Michael Reactions of Enones with Carbamates

    Institute of Scientific and Technical Information of China (English)

    XIA Chun-Gu; XU Li-Wen

    2004-01-01

    The a-amino carbonyl functionality is not only a segment of biologically important natural products but also a versatile intermediate for the synthesis of nitrogen-containing compounds.1 The development of novel synthetic methods leading to a-amino ketone, a-amino acids or their derivatives has attracted much attention in organic synthesis.2 Among the traditional methods for generating a-amino carbonyl compounds, Mannich-type reaction is one of the classical and powerful methods.3 However, the classic Mannich reaction presents serious disadvantages, for example, there is still a drawback in that the silyl enolates have to be prepared from the corresponding carbonyl compounds. Alternatively, aza-Michael additions can be used to create carbon-heteroatom bonds by reaction of a,a-unsaturated carbonyl compounds with amines. Although recent advances have made this route more attractive, development of cheaper, simpler, and more efficient metal catalyst, especially which can be applied to chalcone, is highly desirable.In this paper, we demonstrated that the first aza-Michael reaction of chalcone with a less nucleophilic carbamates can be accomplished on Me3SiCFFeCl3 catalyst system under very mild conditions. Apart from experimental simplicity, the advantages of this methodology are the use of a very cheap Lewis acid catalyst and the insensitivity of the reaction mixture towards air and moisture.catalyst for aza-Michael reaction of chalcone and cyclic enones with carbamates. And with the cyclic enones with carbamates in dichloromethane at room temperature were also investigated. In this conjugate addition reaction, good to excellent yields of a-amino ketones were obtained with system could also mediates aza-Michael addition of carbamates to chalcone and derivatives.These new strategies opened efficient procedures for the synthesis of a-amino ketones under mild conditions.

  10. Sulfamic Acid-Catalyzed Lead Perovskite Formation for Solar Cell Fabrication on Glass or Plastic Substrates.

    Science.gov (United States)

    Guo, Yunlong; Sato, Wataru; Shoyama, Kazutaka; Nakamura, Eiichi

    2016-04-27

    Lead perovskite materials such as methylammonium triiodoplumbate(II) (CH3NH3PbI3, PV) are promising materials for printable solar cell (SC) applications. The preparation of PV involves a series of energetically costly cleavages of the μ-iodo bridges via conversion of a mixture of PbI2 (PI) and methylammonium iodide (CH3NH3I, MAI) in N,N-dimethylformamide (DMF) into a precursor solution containing a polymeric strip of a plumbate(II) dimer [(MA(+))2(PbI3(-))2·(DMF)2]m, which then produces a perovskite film with loss of DMF upon spin-coating and heating of the substrate. We report here that the PI-to-PV conversion and the PV crystal growth to micrometer size can be accelerated by a small amount of zwitterionic sulfamic acid (NH3SO3, SA) and that sulfamic acid facilitates electron transfer to a neighboring electron-accepting layer in an SC device. As a result, an SC device on indium tin oxide (ITO)/glass made of a 320 nm thick PV film using 0.7 wt % SA showed a higher short-circuit current, open-circuit voltage, and fill factor and hence a 22.5% higher power conversion efficiency of 16.02% compared with the device made without SA. The power conversion efficiency value was reproducible (±0.3% for 25 devices), and the device showed very small hysteresis. The device without any encapsulation showed a respectable longevity on a shelf under nitrogen under ambient light. A flexible device similarly fabricated on ITO/poly(ethylene naphthalate) showed an efficiency of 12.4%. PMID:27054265

  11. Acetalization of carbonyl compounds with 2,2,4-trimethyl-1,3-pentanedio catalyzed by novel carbon based solid acid catalyst

    Institute of Scientific and Technical Information of China (English)

    Ling Liu; Yuechang Zhao; Shan Gan; Xuezheng Liang; Jianguo Yang; Mingyuan He

    2008-01-01

    The synthesis of 2, 4-diisopropyl-5,5-dimethyl-1,3-dioxane through the acetalization of isobutyraldehyde with 2, 2,4-trimethyl-1,3-pentanediol (TMPD) catalyzed by the novel carbon based acid was first carried out. High conversion (≥98%) and specific selectivity were obtained using the novel carbon based acid, which kept high activity after it was reused 5 times.Moreover, the catalyst could be used to catalyze the acetalization and ketalization of different aldehydes and ketones with superior yield. The yield of several products was over 90%. The novel heterogeneous catalyst has the distinct advantages of high activity, strikingly simple workup procedure, non-pollution, and reusability, which will contribute to the success of the green process greatly.

  12. Ruthenium-Catalyzed Selective Hydrogenation of bis-Arylidene Tetramic Acids. Application to the Synthesis of Novel Structurally Diverse Pyrrolidine-2,4-diones

    Directory of Open Access Journals (Sweden)

    Olga Igglessi-Markopoulou

    2011-07-01

    Full Text Available Catalytic hydrogenation of 3,5-bis-arylidenetetramic acids, known for their biological activity, has been developed. The chemoselective ruthenium-catalyzed reduction of the exocyclic carbon-carbon double bonds on pyrrolidine-2,4-dione ring system, containing other reducible functions, has been investigated. Depending on the substrate the yield of the hydrogenation process can reach up to 95%. The structural elucidation has been established using NMR and HRMS spectral data.

  13. Visible-Light Photoredox-Catalyzed Giese Reaction: Decarboxylative Addition of Amino Acid Derived α-Amino Radicals to Electron-Deficient Olefins

    KAUST Repository

    Millet, Anthony

    2016-06-20

    A tin- and halide-free, visible-light photoredox-catalyzed Giese reaction was developed. Primary and secondary α-amino radicals were generated readily from amino acids in the presence of catalytic amounts of an iridium photocatalyst. The reactivity of the α-amino radicals has been evaluated for the functionalization of a variety of activated olefins. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  14. Progressive deconstruction of Arundo donax Linn. to fermentable sugars by acid catalyzed ionic liquid pretreatment.

    Science.gov (United States)

    You, Ting-Ting; Zhang, Li-Ming; Xu, Feng

    2016-01-01

    Acid enhanced ionic liquid (IL) 1-n-butyl-3-methylimidazolium chloride ([C4 mim]Cl) pretreatment has shown great potential for boosting the yield of sugars from biomass cost-effectively and environmental-friendly. Pretreatment with shorter processing time will promote the commercial viability. In this work, pretreatment of reduced Amberlyst catalysis time of 34 min was demonstrated to be the most effective among time-varying pretreatments, evidenced by partial removal of hemicellulose and cellulose crystal transformation of Arundo donax Linn. A higher fermentable sugar concentration of 10.42 g/L (2% substrate) was obtained after 72 h of saccharification than the others. Total processing time to reach 92% glucose yield was cut down to approximately 26 h. Progressive deconstruction of crop cell wall was occurred with increased catalysis time by gradual releasing of H3O(+) of Amberlyst. However, vast lignin re-deposited polymers on fibers could hinder further enzymatic hydrolysis. These discoveries provide new insights into a more economic pretreatment for bioethanol production. PMID:26363822

  15. Synthesis of acetals and ketals catalyzed by tungstosilicic acid supported on active carbon

    Institute of Scientific and Technical Information of China (English)

    YANG Shui-jin; DU Xin-xian; HE Lan; SUN Ju-tang

    2005-01-01

    Catalytic activity of activated carbon supported tungstosilicic acidin synthesizing 2-methyl-2-ethoxycarbonylmethyl1,3-dioxolane, 2,4-dimethyl-2-ethoxycarbonylmethyl-l,3-dioxolane, cyclohexanone ethylene ketal, cyclohexanone 1,2-propanediol ketal, butanone ethylene ketal, butanone 1,2-propanediol ketal, 2-phenyl-1,3-dioxolane, 4-methyl-2-phenyl-1,3-dioxolane,2-propyl-1,3-dioxolane, 4-methyl-2-propyl-1,3-dioxolane was reported. It has been demonstrated that activated carbon supported tungstosilicic acid is an excellent catalyst. Various factors involved in these reactions were investigated. The optimum conditions found were: molar ratio of aldehyde/ketone to glycol is 1/1.5, mass ratio of the catalyst used to the reactants is 1.0%, and reaction time is 1.0 h. Under these conditions, the yield of 2-methyl-2-ethoxycarbonylmethyl-l,3-dioxolane is 61.5%, of 2,4-dimethyl2-ethoxycarbonylmethyl-1,3-dioxolane is 69.1%, of cyclohexanone ethylene ketal is 74.6%, of cyclohexanone 1,2-propanediol ketal is 80.1%, of butanone ethylene ketal is 69.5%, of butanone 1,2-propanediol ketal is 78.5%, of 2-phenyl-1,3-dioxolane is 56.7%, of 4-methyl-2-phenyl- 1,3-dioxolane is 86.2%, of 2-propyl-1,3-dioxolane is 87.5%, of 4-methyl-2-propyl-1,3-dioxolane is 87.9%.

  16. Reaction kinetics for synthesis of sec-butyl alcohol catalyzed by acid-functionalized ionic liquid

    Institute of Scientific and Technical Information of China (English)

    Ting Qiu; Wenli Tang; Chenggang Li; Chengming Wu; Ling Li

    2015-01-01

    The acid-functionalized ionic liquid ([HSO3Pmim]HSO4) was synthesized by a two-step method. Nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FT-IR) show that the synthesis method is feasible and high purity of ionic liquid can be obtained. Using [HSO3Pmim]HSO4 as the catalyst, we studied the reaction kinetics of synthesizing sec-butyl alcohol from sec-butyl acetate and methanol by transesterification in a high-pressure batch reactor. The effects of temperature, initial molar ratio of methanol to ester, and catalyst concentration on the conversion of sec-butyl acetate were studied. Based on its possible reaction mechanism, a ho-mogeneous kinetic model was established. The results show that the reaction heatΔH is 10.94 × 103 J·mol−1, so the reaction is an endothermic reaction. The activation energies Ea+and Ea−are 60.38 × 103 and 49.44 × 103 J·mol−1, respectively.

  17. Glutamate 190 is a general acid catalyst in the 6-phosphogluconate-dehydrogenase-catalyzed reaction.

    Science.gov (United States)

    Karsten, W E; Chooback, L; Cook, P F

    1998-11-10

    Site-directed mutagenesis was used to change E190 of sheep liver 6-phosphogluconate dehydrogenase to A, D, H, K, Q, and R to probe its possible role as a general acid catalyst. Each of the mutant proteins was characterized with respect to the pH dependence of kinetic parameters. Mutations that eliminate a titrable group at position 190, result in pH-rate profiles with no observable pK on the basic side of the V/K6PG profile. Mutations that change the pK of the group at position 190 result in the expected pK perturbations in the V/K6PG profile. Kinetic parameters obtained at the pH optimum in the pH-rate profiles are consistent with a rate-limiting tautomerization of the 1,2-enediol of ribulose 5-phosphate consistent with the proposed role of E190. Data are also consistent with some participation of E190 in an isomerization required to form the active Michaelis complex.

  18. Super phosphoric acid catalyzed esterification of Palm Fatty Acid Distillate for biodiesel production: physicochemical parameters and kinetics

    Directory of Open Access Journals (Sweden)

    Metre Anand V.

    2015-03-01

    Full Text Available In the present study the esterification of palm fatty acid distillate (PFAD, a by-product from palm oil industry, in the presence of super phosphoric acid (SPA catalyst was studied. The effects of various physico-chemical parameters such as temperature, PFAD to methanol molar ratio and amount of catalyst on the conversion of biodiesel were investigated. The percent conversion of FFA and properties of the biodiesel were determined following standard methodologies. Percent conversion of biodiesel was found to increase with the increase in PFAD to methanol molar ratio and at 1:12 molar ratio and 70°C temperature 95% conversion was achieved. Thermodynamic parameters were also evaluated in terms of Gibbs free energy, enthalpy and entropy at different molar ratio and temperatures. Both pseudo first and second order irreversible kinetics were applied to a wide range of experimental data. However, according to regression coefficient (R2 the second order described better experimental behavior of kinetic data.

  19. Optimization of Two-Step Acid-Catalyzed Hydrolysis of Oil Palm Empty Fruit Bunch for High Sugar Concentration in Hydrolysate

    Directory of Open Access Journals (Sweden)

    Dongxu Zhang

    2014-01-01

    Full Text Available Getting high sugar concentrations in lignocellulosic biomass hydrolysate with reasonable yields of sugars is commercially attractive but very challenging. Two-step acid-catalyzed hydrolysis of oil palm empty fruit bunch (EFB was conducted to get high sugar concentrations in the hydrolysate. The biphasic kinetic model was used to guide the optimization of the first step dilute acid-catalyzed hydrolysis of EFB. A total sugar concentration of 83.0 g/L with a xylose concentration of 69.5 g/L and a xylose yield of 84.0% was experimentally achieved, which is in well agreement with the model predictions under optimal conditions (3% H2SO4 and 1.2% H3PO4, w/v, liquid to solid ratio 3 mL/g, 130°C, and 36 min. To further increase total sugar and xylose concentrations in hydrolysate, a second step hydrolysis was performed by adding fresh EFB to the hydrolysate at 130°C for 30 min, giving a total sugar concentration of 114.4 g/L with a xylose concentration of 93.5 g/L and a xylose yield of 56.5%. To the best of our knowledge, the total sugar and xylose concentrations are the highest among those ever reported for acid-catalyzed hydrolysis of lignocellulose.

  20. Molecular mechanism of acid-catalyzed hydrolysis of peptide bonds using a model compound.

    Science.gov (United States)

    Pan, Bin; Ricci, Margaret S; Trout, Bernhardt L

    2010-04-01

    The stability of peptide bonds is a critical aspect of biological chemistry and therapeutic protein applications. Recent studies found elevated nonenzymatic hydrolysis in the hinge region of antibody molecules, but no mechanism was identified. As a first step in providing a mechanistic interpretation, this computational study examines the rate-determining step of the hydrolytic reaction of a peptide bond under acidic pH by a path sampling technique using a model compound N-MAA. Most previous computational studies did not include explicit water molecules, whose effects are significant in solution chemistry, nor did they provide a dynamic picture for the reaction process in aqueous conditions. Because no single trajectory can be used to describe the reaction dynamics due to fluctuations at finite temperatures, a variant version of the transition path sampling technique, the aimless shooting algorithm, was used to sample dynamic trajectories and to generate an ensemble of transition trajectories according to their statistical weights in the trajectory space. Each trajectory was computed as the time evolution of the molecular system using the Car-Parrinello molecular dynamics technique. The likelihood maximization procedure and its modification were used in extracting dynamically relevant degrees of freedom in the system, and approximations of the reaction coordinate were compared. Its low log-likelihood score and poor p(B) histogram indicate that the C-O distance previously assumed as the reaction coordinate for the rate-determining step is inadequate in describing the dynamics of the reaction. More than one order parameter in a candidate set including millions of geometric quantities was required to produce a convergent reaction coordinate model; its involvement of many degrees of freedom suggests that this hydrolytic reaction step is very complex. In addition to affecting atoms directly involved in bond-making and -breaking processes, the water network also has

  1. Purification, molecular cloning, and expression of 2-hydroxyphytanoyl- CoA lyase, a peroxisomal thiamine pyrophosphate-dependent enzyme that catalyzes the carbon-carbon bond cleavage during à-oxidation of 3- methyl-branched fatty acids

    CERN Document Server

    Foulon, V; Croes, K; Waelkens, E

    1999-01-01

    Purification, molecular cloning, and expression of 2-hydroxyphytanoyl- CoA lyase, a peroxisomal thiamine pyrophosphate-dependent enzyme that catalyzes the carbon-carbon bond cleavage during à-oxidation of 3- methyl-branched fatty acids

  2. Amino acid-catalyzed seed regrowth synthesis of photostable high fluorescent silica nanoparticles with tunable sizes for intracellular studies

    International Nuclear Information System (INIS)

    Size-controlled fluorescence silica nanoparticles (NPs) are widely used for nanotoxicological studies, and diagnostic and targeted therapies. Such particles can be easily visualized and localized within cell environments and their interactions with cellular components can be monitored. We developed an amino acid-catalyzed seed regrowth technique (ACSRT) to synthesize spherical rhodamine-doped silica NPs with tunable sizes, low polydispersity index as well as high labeling efficiency and enhanced fluorescence photostability. Via ACSRT, fluorescent silica NPs can be obtained by introducing the fluorophore in seed formation step, while a precise control over particle size can be achieved by simply adjusting the concentration of reactants in the regrowth step. Unlike the conventional methods, the proposed ACSRT permits the synthesis of fluorescent silica NPs in a water-based system, without the use of any surfactants and co-surfactants. By this approach, additional linkers for covalent coupling of the fluorophore to silica matrix can be omitted, while a remarkable doping efficiency is achieved. The suitability of these particles for biomedical application is demonstrated by in vitro tests with normal and malignant bone cells. We show that the particles can be easily and unambiguously visualized by a conventional fluorescence microscope, localized, and distinguished within intracellular components. In addition, it is presented that the cellular uptake and cytotoxic profile of silica NPs are strongly correlated to the particle size, concentration, and cell line. The results of in vitro experiments demonstrate that tunable fluorescent silica NPs synthesized with ACSRT can be potentially used for toxicological assessments and nanomedical studies

  3. Amino acid-catalyzed seed regrowth synthesis of photostable high fluorescent silica nanoparticles with tunable sizes for intracellular studies

    Energy Technology Data Exchange (ETDEWEB)

    Shahabi, Shakiba; Treccani, Laura, E-mail: treccani@uni-bremen.de; Rezwan, Kurosch [University of Bremen, Advanced Ceramics (Germany)

    2015-06-15

    Size-controlled fluorescence silica nanoparticles (NPs) are widely used for nanotoxicological studies, and diagnostic and targeted therapies. Such particles can be easily visualized and localized within cell environments and their interactions with cellular components can be monitored. We developed an amino acid-catalyzed seed regrowth technique (ACSRT) to synthesize spherical rhodamine-doped silica NPs with tunable sizes, low polydispersity index as well as high labeling efficiency and enhanced fluorescence photostability. Via ACSRT, fluorescent silica NPs can be obtained by introducing the fluorophore in seed formation step, while a precise control over particle size can be achieved by simply adjusting the concentration of reactants in the regrowth step. Unlike the conventional methods, the proposed ACSRT permits the synthesis of fluorescent silica NPs in a water-based system, without the use of any surfactants and co-surfactants. By this approach, additional linkers for covalent coupling of the fluorophore to silica matrix can be omitted, while a remarkable doping efficiency is achieved. The suitability of these particles for biomedical application is demonstrated by in vitro tests with normal and malignant bone cells. We show that the particles can be easily and unambiguously visualized by a conventional fluorescence microscope, localized, and distinguished within intracellular components. In addition, it is presented that the cellular uptake and cytotoxic profile of silica NPs are strongly correlated to the particle size, concentration, and cell line. The results of in vitro experiments demonstrate that tunable fluorescent silica NPs synthesized with ACSRT can be potentially used for toxicological assessments and nanomedical studies.

  4. Highly Efficient C--N Bond Forming Reactions in Water Catalyzed by Copper(I) Iodide with Calix[4]arene Supported Amino Acid Ionic Liquid%Highly Efficient C--N Bond Forming Reactions in Water Catalyzed by Copper(I) Iodide with Calix[4]arene Supported Amino Acid Ionic Liquid

    Institute of Scientific and Technical Information of China (English)

    黄利; 金灿; 苏为科

    2012-01-01

    A novel and effective protocol has been developed for the Ullmann-type C--N coupling reaction catalyzed by calix[4]arene supported amino acid ionic liquid and copper(I) iodide in water under microwave irradiation condition The protocol uses ealix[4]arene supported amino acid ionic liquid as double function of the ligand and phase-transfer catalyst, and shows good tolerance in good to excellent yields.

  5. Synthesis of oxacyclic scaffolds via dual ruthenium hydride/Brønsted acid-catalyzed isomerization/cyclization of allylic ethers.

    Science.gov (United States)

    Ascic, Erhad; Ohm, Ragnhild G; Petersen, Rico; Hansen, Mette R; Hansen, Casper L; Madsen, Daniel; Tanner, David; Nielsen, Thomas E

    2014-03-17

    A ruthenium hydride/Brønsted acid-catalyzed tandem sequence is reported for the synthesis of 1,3,4,9-tetrahydropyrano[3,4-b]indoles (THPIs) and related oxacyclic scaffolds. The process was designed on the premise that readily available allylic ethers would undergo sequential isomerization, first to enol ethers (Ru catalysis), then to oxocarbenium ions (Brønsted acid catalysis) amenable to endo cyclization with tethered nucleophiles. This methodology provides not only an attractive alternative to the traditional oxa-Pictet-Spengler reaction for the synthesis of THPIs, but also convenient access to THPI congeners and other important oxacycles such as acetals. PMID:24616060

  6. Target-catalyzed autonomous assembly of dendrimer-like DNA nanostructures for enzyme-free and signal amplified colorimetric nucleic acids detection.

    Science.gov (United States)

    He, Hongfei; Dai, Jianyuan; Duan, Zhijuan; Meng, Yan; Zhou, Cuisong; Long, Yuyin; Zheng, Baozhan; Du, Juan; Guo, Yong; Xiao, Dan

    2016-12-15

    Self-assembly of DNA nanostructures is of great importance in nanomedicine, nanotechnology and biosensing. Herein, a novel target-catalyzed autonomous assembly pathway for the formation of dendrimer-like DNA nanostructures that only employing target DNA and three hairpin DNA probes was proposed. We use the sticky-ended Y shape DNA (Y-DNA) as the assembly monomer and it was synthesized by the catalyzed hairpin assembly (CHA) instead of the DNA strand annealing method. The formed Y-DNA was equipped with three ssDNA sticky ends and two of them were predesigned to be complementary to the third one, then the dendrimer-like DNA nanostructures can be obtained via an autonomous assembly among these sticky-ended Y-DNAs. The resulting nanostructure has been successfully applied to develop an enzyme-free and signal amplified gold nanoparticle (AuNP)-based colorimetric nucleic acids assay. PMID:27498325

  7. Additional Nucleophile-Free FeCl3-Catalyzed Green Deprotection of 2,4-Dimethoxyphenylmethyl-Protected Alcohols and Carboxylic Acids.

    Science.gov (United States)

    Sawama, Yoshinari; Masuda, Masahiro; Honda, Akie; Yokoyama, Hiroki; Park, Kwihwan; Yasukawa, Naoki; Monguchi, Yasunari; Sajiki, Hironao

    2016-01-01

    The deprotection of the methoxyphenylmethyl (MPM) ether and ester derivatives can be generally achieved by the combinatorial use of a catalytic Lewis acid and stoichiometric nucleophile. The deprotections of 2,4-dimethoxyphenylmethyl (DMPM)-protected alcohols and carboxylic acids were found to be effectively catalyzed by iron(III) chloride without any additional nucleophile to form the deprotected mother alcohols and carboxylic acids in excellent yields. Since the present deprotection proceeds via the self-assembling mechanism of the 2,4-DMPM protective group itself to give the hardly-soluble resorcinarene derivative as a precipitate, the rigorous purification process by silica-gel column chromatography was unnecessary and the sufficiently-pure alcohols and carboxylic acids were easily obtained in satisfactory yields after simple filtration. PMID:27373632

  8. Ruthenium(III) catalyzed oxidation of sulfanilic acid by diperiodatocuprate(III) in aqueous alkaline medium. A kinetic and mechanistic approach

    Science.gov (United States)

    Munavalli, D. S.; Patil, R. K.; Chimatadar, S. A.; Nandibewoor, S. T.

    2009-12-01

    The kinetics of ruthenium(III) catalyzed oxidation of sulfanilic acid by diperiodatocuprate(III) (DPC) in alkaline medium at a constant ionic strength of (0.50 mol dm-3) has been studied spectrophoto-metrically. The reaction between sulfanilic acid and DPC in alkaline medium exhibits 1: 4 stoichiometry (sulfanilic acid: DPC). The reaction is first order with respect to [DPC] and [RuIII] and has less than unit order both in [sulfanilic acid] and [alkali]. The active species of catalyst and oxidant have been identified. Intervention of free radicals was observed in the reaction. The main products were identified by spot test and IR. Probable mechanism is proposed and discussed. The reaction constants involved in the different steps of the mechanism are calculated. The activation parameters with respect to the slow step of the mechanism are computed and discussed. Thermodynamic quantities are also determined.

  9. Hydrolysis of cellooligosaccharides catalyzed by organic acid%有机酸催化水解纤维低聚糖的研究

    Institute of Scientific and Technical Information of China (English)

    马淑玲; 彭红

    2014-01-01

    The order of catalytic activity of organic acids for hydrolysis of cellooligosaccharides is oxalic acid>maleic acid>malonic acid>acetic acid>formic acid>butanedioic acid. Butanedioic acid could not catalyze the hydrolysis of cellooligosaccharides. The catalytic activity of biatomic acids is relative to their acidity. The acid with higher acidity resulted in higher conversion of cellooligosaccharides. The hydrolysis of cellooligosaccharides catalyzed by organic acid processed step by step,glucose and cellooligosaccharides with lower degree of polymerization produced first,and the produced oligosaccharides was hydrolyzed further. When cellotriose,cellotetraose,and cellopentaose were hydrolyzed under the conditions of substrate concentration 1.5 mg/mL,oxalic acid dosage 0.05 mmol/mL,reaction time 9 h,and temperature 95℃,the product concentrations of glucose were 0.51, 0.53,and 0.13 mg/mL respectively.%有机酸催化水解纤维低聚糖的能力强弱顺序为:草酸>顺丁烯二酸>丙二酸>乙酸>甲酸>丁二酸,丁二酸不能催化水解纤维低聚糖。二元羧酸水解纤维低聚糖时的能力与其水溶液酸性强弱有关,酸性越强,催化水解能力越大,低聚糖的水解率高。有机酸水解纤维低聚糖是分步进行的,先生成葡萄糖和低一级的低聚糖,低一级的低聚糖再水解生成葡萄糖和更低一级的低聚糖。在初始低聚糖浓度为1.5 mg/mL、水解时间9 h和水解温度95℃的条件下,0.05 mmol/mL草酸分别催化水解纤维三糖、纤维四糖和纤维五糖后产物葡萄糖浓度分别为0.51、0.53和0.13 mg/mL。

  10. Synthesis of bio-based methacrylic acid by decarboxylation of itaconic acid and citric acid catalyzed by solid transition-metal catalysts

    NARCIS (Netherlands)

    Notre, le J.E.L.; Witte-van Dijk, S.C.M.; Haveren, van J.; Scott, E.L.; Sanders, J.P.M.

    2014-01-01

    Methacrylic acid, an important monomer for the plastics industry, was obtained in high selectivity (up to 84%) by the decarboxylation of itaconic acid using heterogeneous catalysts based on Pd, Pt and Ru. The reaction takes place in water at 200–2508C without any external added pressure, conditions

  11. Directing Group in Decarboxylative Cross-Coupling: Copper-Catalyzed Site-Selective C-N Bond Formation from Nonactivated Aliphatic Carboxylic Acids.

    Science.gov (United States)

    Liu, Zhao-Jing; Lu, Xi; Wang, Guan; Li, Lei; Jiang, Wei-Tao; Wang, Yu-Dong; Xiao, Bin; Fu, Yao

    2016-08-01

    Copper-catalyzed directed decarboxylative amination of nonactivated aliphatic carboxylic acids is described. This intramolecular C-N bond formation reaction provides efficient access to the synthesis of pyrrolidine and piperidine derivatives as well as the modification of complex natural products. Moreover, this reaction presents excellent site-selectivity in the C-N bond formation step through the use of directing group. Our work can be considered as a big step toward controllable radical decarboxylative carbon-heteroatom cross-coupling. PMID:27439145

  12. Use of immobilized phospholipase A1-catalyzed acidolysis for the production of structured phosphatidylcholine with an elevated conjugated linoleic acid content

    OpenAIRE

    Baeza-Jiménez, R.; GonzáLez-RodríGuez, J.; Kim, In-H.; García, H. S.; Otero, C.

    2012-01-01

    Structured phosphatidylcholine (SPC) was successfully produced via immobilized phospholipase A1 (PLA1) – catalyzed acidolysis of phosphatidylcholine (PC) with conjugated linoleic acid (CLA). The effects of enzyme loading (2, 5, 10, 15 and 20%, with respect to the weight of substrates), temperature (20, 30, 40, 50 and 60 °C) and the molar ratio of substrates (1:2, 1:4, 1:6, 1:8 and 1:10, PC/CLA) were evaluated to maximize the incorporation of CLA i...

  13. Ruthenium Hydride/Brønsted Acid-Catalyzed Tandem Isomerization/N-Acyliminium Cyclization Sequence for the Synthesis of Tetrahydro-β-carbolines

    DEFF Research Database (Denmark)

    Hansen, Casper Lykke; Clausen, Janie Regitse Waël; Ohm, Ragnhild Gaard;

    2013-01-01

    This paper describes an efficient tandem sequence for the synthesis of 1,2,3,4-tetrahydro-β-carbolines (THBCs) relying on a ruthenium hydride/Brønsted acid- catalyzed isomerization of allylic amides to N-acyliminium ion intermediates which are trapped by a tethered indolenucleophile. The methodol...... the Suzuki cross-coupling reaction to the isomerization/N-acyliminium cyclization sequence. Finally, diastereo- and enantioselective versions of the title reaction have been examined using substrate control (with dr >15: 1) and asymmetric catalysis (ee up to 57%), respectively...

  14. Reaction Between U(Ⅳ)and Nitrous Acid Catalyzed by Plutonium%Pu催化HNO2氧化U(Ⅳ)的研究

    Institute of Scientific and Technical Information of China (English)

    王浩文; 周贤明; 李高亮; 兰天; 刘金平; 常尚文; 何辉; 段红卫

    2014-01-01

    The oxidation of U(Ⅳ)by nitrous acid in the present of plutonium was studied. The influence of the concentration of nitrous acid,nitric acid,plutonium on the oxidation of U(Ⅳ)was investigated.The results show that plutonium can catalyze the reaction between U(Ⅳ)and nitrous acid.And the rate equation of the reaction between U(Ⅳ)and nitrous acid catalyzed by plutonium was obtained:-dc(U(Ⅳ))/dt=kc(U(Ⅳ))c1.3 (HNO3 )c1.3 (NO-2 ), k=(0.69±0.04)L2.6/(mol2.6 ·min)when the temperature was 29 ℃.The mechanism of the oxidation of U(Ⅳ)was discussed.%研究了Pu存在条件下 HNO2氧化 U(Ⅳ)的反应,并考察了 HNO2浓度、反应温度、HNO3浓度、Pu 浓度对 U(Ⅳ)氧化速率的影响。结果表明:Pu对 HNO2氧化 U(Ⅳ)的反应具有显著催化作用;获得了 Pu催化条件下 HNO2氧化 U(Ⅳ)的动力学方程:-dc(U(Ⅳ))/dt=kc(U(Ⅳ))c1.3(HNO3)c1.3(NO-2),得到了29℃时的反应速率常数k=(0.69±0.04)L2.6/(mol2.6·min)。并对反应历程进行了探讨。

  15. Highly Efficient Esterification of an Equimolar Amount of Carboxylic Acids and Alcohols Catalyzed by ZrOCl2·8H2O

    Institute of Scientific and Technical Information of China (English)

    Sun Hong-Bin; Hua Ruimao; Yin Ying-Wu

    2004-01-01

    Esterification of carboxylic acids with alcohols is one of the most fundamental and useful transformations in organic synthesis. The most common catalysts are H2SO4 and TsOH. However,H2SO4 or TsOH-catalyzed esterification procedure has some problems such as corrosion, side reactions, difficulty in separation. Hence, recently, various solid acid catalysts such as ion-exchanged resins, molecular sieve, and heteropoly acids etc. have been employed for esterification reaction.However, the solid acid catalysts are usually not easily accessible and expensive In addition, for achieving the high yield of esters, it is usually to carry out the esterification reaction by addition of an excess of one of the reactants. Therefore it is still interesting to develop the high activity,cost-effective catalyst system.which is a commercially available and very cheap inorganic salt.The esterification was carried out in the presence of ZrOCl2. 8H2O (0.05 mol %) using equimolar amount of carboxylic acids and alcohols at room temperature or at 50℃. For example, the esterification of propionic acid with methanol at room temperature for 24 h gave methyl propionate in 81% GC yield. A higher yield of esters can be obtained by the removal of water azeotropically.The present esterification procedure has the following advantages:1) Esters can be obtained in high yield with the use of equimolar amount of carboxylic acids and alcohols.2) Esterification proceeds at room temperature, the catalyst system is suitable for the esterification of highly reactive carboxylic acids such as acrylic acid.3) It is easy to isolate and purify the esters, and the catalyst is recyclable. The complete reaction mixture becomes two phases at room temperature, the esters in the organic phase can be separated conveniently by decanting, and the catalyst in the water can be reused without any treatment.

  16. Oxidation of alkanes with m-chloroperbenzoic acid catalyzed by iron(III) chloride and a polydentate amine

    OpenAIRE

    Shul’pin, Georgiy B.; Stoeckli-Evans, Helen; Mandelli, Dalmo; Kozlov, Yuriy N.; Tesouro Vallina, Ana; Woitiski, Camile B.; Jimenez, Ricardo S.; Carvalho, Wagner A.

    2009-01-01

    Tetradentate amine N,N′-bis(2-pyridylmethylene)-1,4-diaminodiphenyl ether (compound 1) dramatically accelerates the oxidation of alkanes with MCPBA in acetonitrile catalyzed by FeCl3, whereas N,N′-bis(2-pyrrolidinmethylene)-1,4-diaminodiphenyl ether (2) does not affect the reaction. The selectivity of the reaction in the presence of 1 is noticeably higher than that in its absence. On the basis of the kinetic study and selectivity parameters a mechanism has been proposed which includes the for...

  17. Use of immobilized phospholipase A1-catalyzed acidolysis for the production of structured phosphatidylcholine with an elevated conjugated linoleic acid content

    Energy Technology Data Exchange (ETDEWEB)

    Baeza-Jimenez, R.; Gonzalez-Rodriguez, J.; Kim, I. H.; Gracia, H. S.; Otero, C.

    2012-11-01

    Structured phosphatidylcholine (SPC) was successfully produced via immobilized phospholipase A1 (PLA1) catalyzed acidolysis of phosphatidylcholine (PC) with conjugated linoleic acid (CLA). The effects of enzyme loading (2, 5, 10, 15 and 20%, with respect to the weight of substrates), temperature (20, 30, 40, 50 and 60 degree centigrade) and the molar ratio of substrates (1:2, 1:4, 1:6, 1:8 and 1:10, PC/CLA) were evaluated to maximize the incorporation of CLA into PC. The maximum incorporation of CLA achieved was ca. 90% for 24 h of reaction at 50 degree centigrade and 200 rpm, using a 1:4 substrate molar ratio and an enzyme loading of 15%. (Author) 30 refs.

  18. Long-chain ethers as solvents can amplify the enantioselectivity of the Carica papaya lipase-catalyzed transesterification of 2-(substituted phenoxy)propanoic acid esters.

    Science.gov (United States)

    Miyazawa, Toshifumi; Iguchi, Wakana

    2013-10-01

    The enantioselectivity of the transesterification of the 2,2,2-trifluoroethyl esters of 2-(substituted phenoxy)propanoic acids, as catalyzed by the lipase from Carica papaya, was greatly improved by using long-chain ethers, such as di-n-hexyl ether, as solvents instead of the conventional diisopropyl ether. Thus, for example, the E value was enhanced from 21 [in diisopropyl ether (0.8 ml)] to 57 [in di-n-hexyl ether (0.8 ml)] in the reaction of 2,2,2-trifluoroethyl(RS)-2-phenoxypropanoate (0.1 mmol) with methanol (0.4 mmol) in the presence of the plant lipase preparation (10 mg); it was also improved from 13 (in diisopropyl ether) to 44 (in di-n-hexyl ether) in the reaction of 2,2,2-trifluoroethyl(RS)-2-(2-chlorophenoxy)propanoate with methanol under the same reaction conditions.

  19. Camphor-10-sulfonic acid catalyzed condensation of 2-naphthol with aromatic/aliphatic aldehydes to 14-aryl/alkyl-14H-dibenzo[a,j]xanthenes

    Directory of Open Access Journals (Sweden)

    Kundu Kshama

    2014-01-01

    Full Text Available (±-Camphor-10-sulfonic acid (CSA catalyzed condensation of 2-naphthol with both aliphatic/aromatic aldehydes at 80°C yielded 14-alkyl/aryl-dibenzoxanthenes as the sole product in high yields. However, the same condensation with benzaldehyde at 25°C afforded a mixture of intermediate 1,1-bis-(2-hydroxynaphthylphenylmethane and 14-phenyl-dibenzoxanthene while the condensation with aliphatic aldehydes at 25°C furnished the corresponding 14-alkyl-dibenzoxanthenes as the sole product. Moreover, condensation of 2-naphthol with aromatic/aliphatic aldehydes with low catalyst loading (2 mol% was greatly accelerated under microwave irradiation to afford the corresponding 14-aryl/alkyl-dibenzoxanthenes as the sole product in high yields.

  20. 酶法生产共轭亚油酸的研究进展%Development of linoleate isomerase catalyzes forproduction of conjugated linoleic acid

    Institute of Scientific and Technical Information of China (English)

    张艳禾; 王春来; 刘思国; 张兰威

    2011-01-01

    共轭亚油酸(Conjugated linoleic acid,CLA)具有抗癌、抗动脉粥样硬化、减肥和免疫调节等生理活性.共轭亚油酸可以通过酶法异构化获得,将底物亚油酸异构形成具有生物活性物质-共轭亚油酸的异构酶称为亚油酸异构酶.因此,通过介绍亚油酸异构酶的来源、作用机制、酶学性质和基因工程菌生产等方面的研究进展,结合不断发展的基因工程技术,旨在提高亚油酸异构酶的活性、产量和异构化效率,以扩大反应底物范围,降低生产成本,从而推进共轭亚油酸的规模化、可持续性的工业生产.%CLA (Conjugated linoleic acid, CLA) possesses a wide range of biological activities including anti-cancer activity, anti-atherosclerosis activity, capability of helping reduce weight fat and regulate immune system. The fatty acid isomerase from bacteria, which catalyzes the isomerization of linoleic acid (LA) to CLA production, is a promising candidate for other approachs. This paper introduces the source of linoleate isomerase, the mechanism of its function as well as reviewing recent advances regarding the key property of this important enzyme. The preparation of linoleate isomerase and how to use it to produce high yield of isomers of conjugated linoleic acid with high purity are also demonstrated,which will help to realize sustainability and industrial scale production of conjugated linoleic acid.

  1. Conversion of nicotinic acid to trigonelline is catalyzed by N-methyltransferase belonged to motif B′ methyltransferase family in Coffea arabica

    Energy Technology Data Exchange (ETDEWEB)

    Mizuno, Kouichi, E-mail: koumno@akita-pu.ac.jp [Faculty of Bioresource Sciences, Akita Prefectural University, Akita City, Akita 010-0195 (Japan); Matsuzaki, Masahiro [Faculty of Bioresource Sciences, Akita Prefectural University, Akita City, Akita 010-0195 (Japan); Kanazawa, Shiho [Graduate School of Humanities and Sciences, Ochanomizu University, Otsuka, Bunkyo-ku, Tokyo 112-8610 (Japan); Tokiwano, Tetsuo; Yoshizawa, Yuko [Faculty of Bioresource Sciences, Akita Prefectural University, Akita City, Akita 010-0195 (Japan); Kato, Misako [Graduate School of Humanities and Sciences, Ochanomizu University, Otsuka, Bunkyo-ku, Tokyo 112-8610 (Japan)

    2014-10-03

    Graphical abstract: Trigonelline synthase catalyzes the conversion of nicotinic acid to trigonelline. We isolated and characterized trigonelline synthase gene(s) from Coffea arabica. - Highlights: • Trigonelline is a major compound in coffee been same as caffeine is. • We isolated and characterized trigonelline synthase gene. • Coffee trigonelline synthases are highly homologous with coffee caffeine synthases. • This study contributes the fully understanding of pyridine alkaloid metabolism. - Abstract: Trigonelline (N-methylnicotinate), a member of the pyridine alkaloids, accumulates in coffee beans along with caffeine. The biosynthetic pathway of trigonelline is not fully elucidated. While it is quite likely that the production of trigonelline from nicotinate is catalyzed by N-methyltransferase, as is caffeine synthase (CS), the enzyme(s) and gene(s) involved in N-methylation have not yet been characterized. It should be noted that, similar to caffeine, trigonelline accumulation is initiated during the development of coffee fruits. Interestingly, the expression profiles for two genes homologous to caffeine synthases were similar to the accumulation profile of trigonelline. We presumed that these two CS-homologous genes encoded trigonelline synthases. These genes were then expressed in Escherichiacoli, and the resulting recombinant enzymes that were obtained were characterized. Consequently, using the N-methyltransferase assay with S-adenosyl[methyl-{sup 14}C]methionine, it was confirmed that these recombinant enzymes catalyzed the conversion of nicotinate to trigonelline, coffee trigonelline synthases (termed CTgS1 and CTgS2) were highly identical (over 95% identity) to each other. The sequence homology between the CTgSs and coffee CCS1 was 82%. The pH-dependent activity curve of CTgS1 and CTgS2 revealed optimum activity at pH 7.5. Nicotinate was the specific methyl acceptor for CTgSs, and no activity was detected with any other nicotinate derivatives, or

  2. Conversion of nicotinic acid to trigonelline is catalyzed by N-methyltransferase belonged to motif B′ methyltransferase family in Coffea arabica

    International Nuclear Information System (INIS)

    Graphical abstract: Trigonelline synthase catalyzes the conversion of nicotinic acid to trigonelline. We isolated and characterized trigonelline synthase gene(s) from Coffea arabica. - Highlights: • Trigonelline is a major compound in coffee been same as caffeine is. • We isolated and characterized trigonelline synthase gene. • Coffee trigonelline synthases are highly homologous with coffee caffeine synthases. • This study contributes the fully understanding of pyridine alkaloid metabolism. - Abstract: Trigonelline (N-methylnicotinate), a member of the pyridine alkaloids, accumulates in coffee beans along with caffeine. The biosynthetic pathway of trigonelline is not fully elucidated. While it is quite likely that the production of trigonelline from nicotinate is catalyzed by N-methyltransferase, as is caffeine synthase (CS), the enzyme(s) and gene(s) involved in N-methylation have not yet been characterized. It should be noted that, similar to caffeine, trigonelline accumulation is initiated during the development of coffee fruits. Interestingly, the expression profiles for two genes homologous to caffeine synthases were similar to the accumulation profile of trigonelline. We presumed that these two CS-homologous genes encoded trigonelline synthases. These genes were then expressed in Escherichiacoli, and the resulting recombinant enzymes that were obtained were characterized. Consequently, using the N-methyltransferase assay with S-adenosyl[methyl-14C]methionine, it was confirmed that these recombinant enzymes catalyzed the conversion of nicotinate to trigonelline, coffee trigonelline synthases (termed CTgS1 and CTgS2) were highly identical (over 95% identity) to each other. The sequence homology between the CTgSs and coffee CCS1 was 82%. The pH-dependent activity curve of CTgS1 and CTgS2 revealed optimum activity at pH 7.5. Nicotinate was the specific methyl acceptor for CTgSs, and no activity was detected with any other nicotinate derivatives, or with

  3. Bispalladacycle-catalyzed Brønsted acid/base-promoted asymmetric tandem azlactone formation-Michael addition.

    Science.gov (United States)

    Weber, Manuel; Jautze, Sascha; Frey, Wolfgang; Peters, René

    2010-09-01

    Cooperative activation by a soft bimetallic catalyst, a hard Brønsted acid, and a hard Brønsted base has allowed the formation of highly enantioenriched, diastereomerically pure masked alpha-amino acids with adjacent quaternary and tertiary stereocenters in a single reaction starting from racemic N-benzoylated amino acids. The products can, for example, be used to prepare bicyclic dipeptides. PMID:20715774

  4. HPLC-ESI-MS/MS analysis of oxidized di-caffeoylquinic acids generated by metalloporphyrin-catalyzed reactions

    OpenAIRE

    Michel D. Santos; Norberto P. Lopes; Yassuko Iamamoto

    2008-01-01

    This paper reports an HPLC-ESI-MS/MS investigation on the oxidation of 3,5- and 4,5- dicaffeoylquinic acid using iron(III) tetraphenylporphyrin chloride as catalyst. Two major mono-oxidised products of the quinic acid moiety have been identified for both compounds. However, only the 4,5-derivative afforded two different tri-oxo products. Thus, it seems that the oxidation pattern depends on the number and positions of the caffeic acid moieties present in caffeoylquinic acid molecules.

  5. HPLC-ESI-MS/MS analysis of oxidized di-caffeoylquinic acids generated by metalloporphyrin-catalyzed reactions

    Directory of Open Access Journals (Sweden)

    Michel D. Santos

    2008-01-01

    Full Text Available This paper reports an HPLC-ESI-MS/MS investigation on the oxidation of 3,5- and 4,5- dicaffeoylquinic acid using iron(III tetraphenylporphyrin chloride as catalyst. Two major mono-oxidised products of the quinic acid moiety have been identified for both compounds. However, only the 4,5-derivative afforded two different tri-oxo products. Thus, it seems that the oxidation pattern depends on the number and positions of the caffeic acid moieties present in caffeoylquinic acid molecules.

  6. Enzymatic α-glucuronylation of maltooligosaccharides using α-glucuronic acid 1-phosphate as glycosyl donor catalyzed by a thermostable phosphorylase from Aquifex aeolicus VF5.

    Science.gov (United States)

    Umegatani, Yuta; Izawa, Hironori; Nawaji, Mutsuki; Yamamoto, Kazuya; Kubo, Akiko; Yanase, Michiyo; Takaha, Takeshi; Kadokawa, Jun-ichi

    2012-03-01

    This paper describes thermostable phosphorylase-catalyzed α-glucuronylation of maltooligosaccharides for the direct synthesis of anionic oligosaccharides having a glucuronic acid residue at the non-reducing end. When the reaction of α-glucuronic acid 1-phosphate (GlcA-1-P) as a glycosyl donor and maltotriose as a glycosyl acceptor was performed in the presence of thermostable phosphorylase from Aquifex aeolicus VF5, high performance anion exchange chromatography analysis of the reaction mixture suggested the production of a glucuronylated tetrasaccharide, whose structure was also confirmed by the MALDI-TOF MS measurement of the crude products. Furthermore, treatment of the crude products with glucoamylase supported that the α-glucuronic acid unit was positioned at the non-reducing end of the tetrasaccharide and (1)H NMR analysis suggested that it was bound in an α-(1→4)-linkage. When the α-glucuronylation of maltotetraose using GlcA-1-P was conducted, α-glucuronylated oligosaccharides with various degrees of polymerization were produced. On the other hand, the α-glucuronylation of maltotetraose using GlcA-1-P in the presence of potato phosphorylase did not occur at all, indicating no recognition of GlcA-1-P by potato phosphorylase. PMID:22265379

  7. DFT Study of Solvent Effects in Acid-Catalyzed Diels-Alder Cycloadditions of 2,5-Dimethylfuran and Maleic Anhydride.

    Science.gov (United States)

    Salavati-fard, Taha; Caratzoulas, Stavros; Doren, Douglas J

    2015-09-24

    Density functional theory electronic structure calculations were used to explore the mechanism for the Diels-Alder reaction between 2,5-dimethylfuran and maleic anhydride (MA). Reaction paths are reported for uncatalyzed and Lewis and Brønsted acid-catalyzed reactions in vacuum and in a broad range of solvents. The calculations show that, while the uncatalyzed Diels-Alder reaction is thermally feasible in vacuum, a Lewis acid (modeled as Na(+)) lowers the activation barrier by interacting with the dienophile (MA) and decreasing the HOMO-LUMO gap of the reactants. A Brønsted acid (modeled as a proton) can bind to a carbonyl oxygen in MA, changing the reaction mechanism from concerted to stepwise and eliminating the activation barrier. Solvation effects were studied with the SMD model. Electrostatic effects play the largest role in determining the solvation energy of the transition state, which tracks the net dipole moment at the transition state. For the uncatalyzed reaction, the dipole moment is largely determined by charge transfer between the reactants, but in the reactions with ionic catalysts, there is no simple relationship between solvation of the transition state and charge transfer between the reactants. Nonelectrostatic contributions to solvation of the reactants and transition state also make significant contributions to the activation energy. PMID:26331220

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

    NARCIS (Netherlands)

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

    2014-01-01

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

  9. Aspergillus niger lipase-catalyzed synthesis of high contentlauric acid monoglyceride%黑曲霉脂肪酶合成单月桂酸甘油酯

    Institute of Scientific and Technical Information of China (English)

    邓颖颖; 杨哪; 徐学明

    2012-01-01

    A lipase from Aspergillus niger has been found with strong catalytic activity and selectivity.In order to prove the lipase high selectivity,it was used to catalyze the fatty acids and glycerin synthetic fatty acid glyceride and optimize the reaction process parameters.The results showed that when the ratio of glycerol to lauric acid 1:1.5,the lipase dosage 0.5%(W/W),the water dosage 3%(W/W)based on the reactant which was employed in the reacting system,the conversion rate of lauric acid could reach 91.2% at 50℃ for 12h reaction.The content of lauric acid monoglycerid was about 70% in the reacting production.%从黑曲霉中提出了一种具有很高催化活性和选择性的脂肪酶,为证明这种脂肪酶的高选择性,用此酶直接催化甘油和月桂酸反应合成单月桂酸甘油酯,并且优化了反应的工艺参数。实验表明,采用甘油月桂酸摩尔比为1∶1.5,脂肪酶与底物质量比为0.5%,水与底物质量比为3%的条件在50℃下反应12h,可使月桂酸转化率达到91.2%,单酯含量高达70%。

  10. Photo-degradation of Acid-red 3B dye catalyzed by TiO2 nanotubes

    Institute of Scientific and Technical Information of China (English)

    JIANG Fang; ZHENG Shou-rong; ZHENG Zheng; XU Zhao-yi; WANG Yan-jin

    2006-01-01

    TiO2 nanotube precursor was synthesized by the hydrothermal reaction of TiO2 powders with NaOH solution and the properties of the nanotube materials were tuned using different post-treatments. Transmission electron microscopic (TEM) observation revealed that the nanotube could be obtained by either a direct rinse with acid solution or rinse with distilled water followed by acid solution. The results of X-ray diffraction (XRD) and inductively coupled plasma (ICP) analysis indicated that the nanotube material on the post-treatment. The results of the photocatalytic reaction showed that the degradation of Acid-red 3B dye fitted pseudo-zero-order kinetics and TiO2 nanotube prepared under direct rinse with acid solution exhibited a higher catalytic efficiency compared to other catalysts.

  11. Biomimetic Decarboxylation of Carboxylic Acids with PhI(OAc)2 Catalyzed by Manganese Porphyrin [Mn(TPP)OAcl

    Institute of Scientific and Technical Information of China (English)

    GHOLAM REZA Karimipour; ROXANA Ahmadpour

    2008-01-01

    Manganese(Ⅲ) meso-tetraphenylporphyrin acetate [Mn(TPP)OAc] served as an effective catalyst for the oxidative decarboxylation of carboxylic acids with (diacetoxyiodo)benzene [Phl(OAc)2] in CH2C12-H2O(95:5,volume ratio),The aryl substituted acetic acids are more reactive than the less electron rich linear carboxylic acids in the presence of catalyst Mn(TPP)OAc,In the former case,the formation of carbonyl products was complete within just a few minutes with >97% selectivities,and no further oxidation of the produced aldehydes was achieved under these catalytic conditions,This method provides a benign procedure owing to the utilization of low toxic(diacetoxyiodo)benzene,biologically relevant manganese porphyrins,and carboxylic acids.

  12. Effect of Solvent and Acid-Base on Palladium(ll)-catalyzed Dicarbonylation of Terminal Acetylenes: a General, Efficient andStereoselective Synthesis of Maleic Diesters and Maleic Anhydrides

    Institute of Scientific and Technical Information of China (English)

    JIANG, Huan-Feng; LI, JiN-Heng; CHEN, Ming-Cai

    2001-01-01

    The productions of maleic diesters and maleic anhydrises depend on the effect of solvint and acid-bade of solvent and acid-base in palladium-catalyzed dicarbonylation of terminal acetylenes. For primaryand secondary alcohol in benzene.only maleic diesters wereobtained stereospecifically from the sicabonylation ofacetylenes in the presence of PdCl2,and NaHCO3.For tERTIARy alcohols,maleic anhydrides were synthesized selectively.

  13. Synthesis of high molecular weight polylactic acid from aqueous lactic acid co-catalyzed by tin(II)chloride dihydrate and succinic anhydride

    Institute of Scientific and Technical Information of China (English)

    LEI Ziqiang; BAI Yanbin; WANG Shoufeng

    2005-01-01

    Polylactic acid was synthesized from commercial available cheap aqueous lactic acid (85%―90% w/w) using succinic anhydride and SnCl2·2H2O as catalyst in the absence of organic solvents. As a result, polylactic acid with a molecular weight of 60000 was prepared in 10 h. The new procedure is much simple, cheap and outstanding in that the start material is aqueous lactic acid; the catalytic system is environmentally benign.

  14. Evolution of diterpene metabolism: Sitka spruce CYP720B4 catalyzes multiple oxidations in resin acid biosynthesis of conifer defense against insects.

    Science.gov (United States)

    Hamberger, Björn; Ohnishi, Toshiyuki; Hamberger, Britta; Séguin, Armand; Bohlmann, Jörg

    2011-12-01

    Diterpene resin acids (DRAs) are specialized (secondary) metabolites of the oleoresin defense of conifers produced by diterpene synthases and cytochrome P450s of the CYP720B family. The evolution of DRA metabolism shares common origins with the biosynthesis of ent-kaurenoic acid, which is highly conserved in general (primary) metabolism of gibberellin biosynthesis. Transcriptome mining in species of spruce (Picea) and pine (Pinus) revealed CYP720Bs of four distinct clades. We cloned a comprehensive set of 12 different Sitka spruce (Picea sitchensis) CYP720Bs as full-length cDNAs. Spatial expression profiles, methyl jasmonate induction, and transcript enrichment in terpenoid-producing resin ducts suggested a role of CYP720B4 in DRA biosynthesis. CYP720B4 was characterized as a multisubstrate, multifunctional enzyme by the formation of oxygenated diterpenoids in metabolically engineered yeast, yeast in vivo transformation of diterpene substrates, in vitro assays with CYP720B4 protein produced in Escherichia coli, and alteration of DRA profiles in RNA interference-suppressed spruce seedlings. CYP720B4 was active with 24 different diterpenoid substrates, catalyzing consecutive C-18 oxidations in the biosynthesis of an array of diterpene alcohols, aldehydes, and acids. CYP720B4 was most active in the formation of dehydroabietic acid, a compound associated with insect resistance of Sitka spruce. We identified patterns of convergent evolution of CYP720B4 in DRA metabolism and ent-kaurene oxidase CYP701 in gibberellin metabolism and revealed differences in the evolution of specialized and general diterpene metabolism in a gymnosperm. The genomic and functional characterization of the gymnosperm CYP720B family highlights that the evolution of specialized metabolism involves substantial diversification relative to conserved, general metabolism. PMID:21994349

  15. Evolution of Diterpene Metabolism: Sitka Spruce CYP720B4 Catalyzes Multiple Oxidations in Resin Acid Biosynthesis of Conifer Defense against Insects1[C][W][OA

    Science.gov (United States)

    Hamberger, Björn; Ohnishi, Toshiyuki; Hamberger, Britta; Séguin, Armand; Bohlmann, Jörg

    2011-01-01

    Diterpene resin acids (DRAs) are specialized (secondary) metabolites of the oleoresin defense of conifers produced by diterpene synthases and cytochrome P450s of the CYP720B family. The evolution of DRA metabolism shares common origins with the biosynthesis of ent-kaurenoic acid, which is highly conserved in general (primary) metabolism of gibberellin biosynthesis. Transcriptome mining in species of spruce (Picea) and pine (Pinus) revealed CYP720Bs of four distinct clades. We cloned a comprehensive set of 12 different Sitka spruce (Picea sitchensis) CYP720Bs as full-length cDNAs. Spatial expression profiles, methyl jasmonate induction, and transcript enrichment in terpenoid-producing resin ducts suggested a role of CYP720B4 in DRA biosynthesis. CYP720B4 was characterized as a multisubstrate, multifunctional enzyme by the formation of oxygenated diterpenoids in metabolically engineered yeast, yeast in vivo transformation of diterpene substrates, in vitro assays with CYP720B4 protein produced in Escherichia coli, and alteration of DRA profiles in RNA interference-suppressed spruce seedlings. CYP720B4 was active with 24 different diterpenoid substrates, catalyzing consecutive C-18 oxidations in the biosynthesis of an array of diterpene alcohols, aldehydes, and acids. CYP720B4 was most active in the formation of dehydroabietic acid, a compound associated with insect resistance of Sitka spruce. We identified patterns of convergent evolution of CYP720B4 in DRA metabolism and ent-kaurene oxidase CYP701 in gibberellin metabolism and revealed differences in the evolution of specialized and general diterpene metabolism in a gymnosperm. The genomic and functional characterization of the gymnosperm CYP720B family highlights that the evolution of specialized metabolism involves substantial diversification relative to conserved, general metabolism. PMID:21994349

  16. Studies of manufacturing controlled-release graphene acid and catalyzing synthesis of chalcone with Claisen-Schmidt condensation reaction

    Science.gov (United States)

    Li, Jihui; Feng, Jia; Li, Mei; Wang, Qiaolian; Su, Yumin; Jia, Zhixin

    2013-07-01

    In the paper, graphene acid (GA) was manufactured, using flake graphite as raw material, and the acidity and the structure of GA were characterized as well as. Then, chalcone was synthesized in the presence of GA, using acetophenone and benzaldehyde as the reactant. The results showed that the acidity of GA was for pH = 1.12 in aqueous solution, and it was structured by the graphene sheets with the spaces between the graphene sheet and the graphene sheet and sulfuric acid (H2SO4) and acetic acid (CH3CO2H) inside the spaces. At the same time, the results also exhibited that the chalcone yield was able to reach 60.36% when GA dosage was 5 g, and the chalcone yields could attain apart 60.36, 52.05 and 31.16% when 5 g of GA was used thrice. This shows that GA is not only a high-performance catalyst, but also a controlled-release catalyst.

  17. Evidence for a transient peroxynitro acid in the reaction catalyzed by nitronate monooxygenase with propionate 3-nitronate.

    Science.gov (United States)

    Smitherman, Crystal; Gadda, Giovanni

    2013-04-16

    Nitronate monooxygenase is a flavin-dependent enzyme that catalyzes the denitrification of propionate 3-nitronate (P3N) and other alkyl nitronates. The enzyme was previously known as 2-nitropropane dioxygenase, until its reclassification in 2010 by the IUBMB. Physiologically, the monooxygenase from fungi protects the organism from the environmental occurrence of P3N, which shuts down the Krebs cycle by inactivating succinate dehydrogenase and fumarase. The inhibition of these enzymes yields severe neurological disorders or death. Here, we have used for the first time steady-state and rapid kinetics, viscosity and pH effects, and time-resolved absorbance spectroscopy of the enzyme in turnover with P3N and the substrate analogue ethyl nitronate (EN) to elucidate the mechanism of the reaction. A transient increase in absorbance at ∼300 nm, never reported before, was seen during steady-state turnover of the enzyme with P3N and oxygen, with no concomitant changes between 400 and 600 nm. The transient species was not detected when oxygen was absent. Anaerobic reduction of the enzyme with P3N yielded anionic flavosemiquinone and was fast (e.g., ≥1900 s(-1)). Steady-state kinetics demonstrated that oxygen reacts before the release of the product of P3N oxidation from the enzyme. No pH effects were seen with P3N on kcat/Km, kcat/Koxygen, and kcat; in contrast, with EN, the kcat/Km and kcat decreased with increasing pH defining two plateaus and a pKa ∼ 8.0. Solvent viscosity at the pH optima suggested product release as being partially controlling the overall rate of turnover with the physiological substrate and its analogue. A mechanism that satisfies the kinetic results is proposed. PMID:23530838

  18. The decolorization of Acid Orange II in non-homogeneous Fenton reaction catalyzed by natural vanadium-titanium magnetite

    Energy Technology Data Exchange (ETDEWEB)

    Liang Xiaoliang; Zhong Yuanhong [Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, 510640 (China); Graduate University of the Chinese Academy of Sciences, Beijing 100049 (China); Zhu Sanyuan; Zhu Jianxi; Yuan Peng [Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, 510640 (China); He Hongping, E-mail: hehp@gig.ac.cn [Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, 510640 (China); Zhang Jing [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China)

    2010-09-15

    The catalytic activity of natural vanadium-titanium magnetite was investigated in the decolorization of Acid Orange II by non-homogeneous Fenton process. The natural catalysts purified by magnetic separation were characterized using X-ray diffraction (XRD), polarizing microscope, X-ray absorption fine structure (XAFS) analysis and Moessbauer spectroscopy. The obtained results show that the natural samples after magnetic separation mainly contain titanomagnetite, with a small amount of ilmenite and chlorite. Titanomagnetite is doped with vanadium, whose the valency is mainly +3 and occupies the octahedral site. Batch decolorization studies were performed to evaluate the influences of various experimental parameters like initial pH, the amount of catalyst and initial concentration of hydrogen peroxide on the decolorization efficiency of Acid Orange II. The decolorization of the dye mainly relied on degradation. The degradation efficiency was strongly dependent on pH of the medium where it increased as the pH decreased in acid range. The increase of catalyst and hydrogen peroxide could accelerate the degradation. The catalytic property of natural vanadium-titanium magnetite in the degradation of Acid Orange II was stronger than that of synthetic magnetite (Fe{sub 3}O{sub 4}). The catalytic activity of the natural samples was greatly related to the titanomagnetite content. The degradation process was dominated by heterogeneous Fenton reaction, complying with pseudo-first-order rate law. The natural catalyst has a good catalytic stability.

  19. N-Arylation of azaheterocycles with aryl and heteroaryl halides catalyzed by iminodiacetic acid resin-chelated copper complex

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Iminodiacetic acid resin-chelated copper(Ⅱ) complex is effective in cross-coupling reactions between azaheterocycles and aryl or heteroaryl halides,providing N-arylated products in good to excellent yields.The copper catalyst is air stable and can be readily recovered and reused with minimal loss of activity for three runs.

  20. Erbium trifluoromethanesulfonate-catalyzed Friedel–Crafts acylation using aromatic carboxylic acids as acylating agents under monomode-microwave irradiation

    DEFF Research Database (Denmark)

    Tran, Phuong Hoang; Hansen, Poul Erik; Nguyen, Hai Truong;

    2015-01-01

    Erbium trifluoromethanesulfonate is found to be a good catalyst for the Friedel–Crafts acylation of arenes containing electron-donating substituents using aromatic carboxylic acids as the acylating agents under microwave irradiation. An effective, rapid and waste-free method allows the preparation...... of a wide range of aryl ketones in good yields and in short reaction times with minimum amounts of waste...

  1. SYNTHESIS OF METHYL TERT-BUTYL ETHER CATALYZED BY ACIDIC ION-EXCHANGE RESINS - INFLUENCE OF THE PROTON ACTIVITY

    NARCIS (Netherlands)

    PANNEMAN, HJ; BEENACKERS, AACM

    1995-01-01

    The catalytic activity of various strong acid ion-exchange resins on the synthesis of methyl tert-butyl ether (MtBE) from methanol and isobutene has been investigated. Relative to Amberlyst 15, Kastel CS 381 and Amberlyst CSP have similar rate constants, whereas Duolite ES 276 and Amberlyst XE 307 h

  2. Lipase-Catalyzed Production of 6-O-cinnamoyl-sorbitol from D-sorbitol and Cinnamic Acid Esters.

    Science.gov (United States)

    Kim, Jung-Ho; Bhatia, Shashi Kant; Yoo, Dongwon; Seo, Hyung Min; Yi, Da-Hye; Kim, Hyun Joong; Lee, Ju Hee; Choi, Kwon-Young; Kim, Kwang Jin; Lee, Yoo Kyung; Yang, Yung-Hun

    2015-05-01

    To overcome the poor properties of solubility and stability of cinnamic acid, cinnamate derivatives with sugar alcohols were produced using the immobilized Candida antarctica lipase with vinyl cinnamate and D-sorbitol as substrate at 45 °C. Immobilized C. antarctica lipase was found to synthesize 6-O-cinnamoyl-sorbitol and confirmed by HPLC and (1)H-NMR and had a preference for vinyl cinnamate over other esters such as allyl-, ethyl-, and isobutyl cinnamate as co-substrate with D-sorbitol. Contrary to D-sorbitol, vinyl cinnamate, and cinnamic acid, the final product 6-O-cinnamoyl-sorbitol was found to have radical scavenging activity. This would be the first report on the biosynthesis of 6-O-cinnamoyl-sorbitol with immobilized enzyme from C. antarctica.

  3. Aza-Michael addition reactions between nitroolefins and benzotriazole catalyzed by MCM-41 immobilized heteropoly acids in water

    Institute of Scientific and Technical Information of China (English)

    Shao-Lei Xie; Yong-Hai Hui; Xiang-Ju Long; Chang-Chun Wang; Zheng-Feng Xie

    2013-01-01

    MCM-41 supported heteropoly acids (HPAs) catalysts were synthesized,characterized and their catalytic activity was evaluated in an aza-Michael addition reaction between nitroolefins and benzotriazole in water at room temperature.50 wt% PW/MCM-41 showed the highest activity (up to 96% yield).The catalyst was used in six consecutive experiments without obvious loss of activity,confirming the success of the anchoring process and the catalyst stability.

  4. Efficient Synthesis of Functionalized 1-oxo-1-phenyl-2-acetic Acids through Ru(II)-catalyzed Transfer Hydrogenation

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xiaowei; Gong, Binwei; Meng, Yanqiu [Shenyang Univ. of Chemical Technology, Shenyang (Korea, Republic of); Yan, Yunnan [Gannan Medical Univ., Ganzhou (Korea, Republic of); Tang, Xiaobo; Eric Xu, H.; Yi, Wei [Chinese Academy of Sciences, Shanghai (China); Li, Qiu [Univ. of Science and Technology of China, Suzhou (China)

    2013-10-15

    A new and alternative method for the efficient synthesis of indanylacetic acid 2 has been developed. The methodology used RuCl(p-cymene)[(R,R)-TsDPEN] as the catalyst and formic acid-triethylamine as the hydrogen source at room temperature under solvent-free conditions, and the reactions have excellent chemoselectivity and good compatibility of substrates. Used our developed method as the starting step, gram scale synthesis of GR24 was achieved smoothly with an overall yield of 72%. All the results suggested that further development of such methodology may be of interest. Further work to establish the mechanistic reasons for selectivity and to further explore the synthetic scope of this mode of transfer hydrogenation is in progress. The synthetic SL analog, GR24 is a very potent germination stimulant, which is widely used in parasitic weed research to stimulate germination and as a standard for comparison of new germinating agents. Owing to the prevalence of GR24, its total synthesis constitutes a hot area of research. So far all known synthetic routes of GR24 used indanylacetic acid 2 as a key intermediate, for which very few methods of building compound 2 have been reported.

  5. Experimental and Kinetic Modeling Studies on the Sulfuric Acid Catalyzed Conversion of D-Fructose to 5-Hydroxymethylfurfural and Levulinic Acid in Water

    NARCIS (Netherlands)

    Fachri, Boy A.; Abdilla, Ria M.; van de Bovenkamp, Henk H.; Rasrendra, Carolus B.; Heeres, Hero J.

    2015-01-01

    Levulinic acid (LA) and 5-hydroxymethylfurfural (HMF) have been identified as promising biomass-derived platform chemicals. A kinetic study on the conversion of D-fructose to HMF and LA in water using sulfuric acid as the catalyst has been performed in batch setups. The experiments were carried out

  6. H8-BINOL chiral imidodiphosphoric acids catalyzed enantioselective synthesis of dihydroindolo-/-pyrrolo[1,2-a]quinoxalines.

    Science.gov (United States)

    Fan, Yan-Sen; Jiang, Yi-Jun; An, Dong; Sha, Di; Antilla, Jon C; Zhang, Suoqin

    2014-12-01

    The first enantioselective synthesis of 5,6-dihydroindolo[1,2-a]quinoxalines is achieved by using a newly developed H8-BINOL-type imidodiphosphoric acid catalyst with low catalyst loading through efficient Pictet-Spengler-type reactions of indolyl anilines with ketones. This methodology also generates phenyl-4,5-dihydropyrrolo[1,2-a]quinoxalines with high yields and excellent enantioselectivities. Moreover, this method was utilized to synthesize an HIV-1 inhibitor with high yield and good enantioselectivity through a one-step procedure. PMID:25415871

  7. One-Pot Synthesis of 5-Alkoxycarbonyl-4-aryl-3,4-dihydropyrimidin-2- ones Catalyzed by Phosphotungstic Acid

    Institute of Scientific and Technical Information of China (English)

    JIN Tong-Shou; XIAO Jin-Chong; LI Tong-Shuang

    2003-01-01

    @@ Many dihydropyrimidinones and their derivatives play an important role in medicine due to their therapeutic and pharmacological properties. [1] They have emerged as the integral backbones of several calcium channel blockers, antihypertensive agents, alpha-1α-antagonists. [2] Strategies for the synthesis of dihydropyrimidinone nucleus have varied from one-pot to multistep approaches. Although high yields can be achieved by the following complex multistep procedures, these methods lack the simplicity comparing with Biginelli protocol which firstly reported by Biginelli by one-pot condensation of aryl aldehyde, β-ketoesters and urea with catalytic acid in 1993, and these multistep methods suffer from low yields particularly for substituted aromatic aldehyde.

  8. Catalyzed Ester Synthesis Using Candida rugosa Lipase Entrapped by Poly(N-isopropylacrylamide-co-itaconic Acid) Hydrogel

    OpenAIRE

    2014-01-01

    This study reports the synthesis of polymeric matrices based on N-isopropylacrylamide and itaconic acid and its application for immobilization of lipase from Candida rugosa. The lipase was immobilized by entrapment method. Free and immobilized lipase activities, pH and temperature optima, and storage stability were investigated. The optimum temperature for free and entrapped lipase was found to be 40 and 45°C, while the optimum pH was observed at pH 7 and 8, respectively. Both hydrolytic acti...

  9. Impact of zeolite aging in hot liquid water on activity for acid-catalyzed dehydration of alcohols

    Energy Technology Data Exchange (ETDEWEB)

    Vjunov, Aleksei; Derewinski, Miroslaw A.; Fulton, John L.; Camaioni, Donald M.; Lercher, Johannes A.

    2015-08-19

    The catalytic performance of zeolite in aqueous medium depends on a multitude of factors, such as the concentration and distribution of active sites and framework integrity. Al K–edge extended X–ray absorption fine structure and 27Al MAS NMR spectroscopies in combination with DFT calculations are used to determine the distribution of tetrahedral Al sites both qualitatively and quantitatively for both parent and 48 h 160 ºC water treated HBEA catalysts. There is no evidence of Al coordination modification after aging in water. The distribution and concentration of Al T–sites, active centers for the dehydration of cyclohexanol, do not markedly impact the catalytic performance in water, because the Brønsted acidic protons are present in the form of hydrated hydronium ions and thus have very similar acid properties. The results suggest that all Brønsted acid sites are equally active in aqueous medium. The decrease of zeolite catalytic performance after water treatment is attributed to the reduced concentration of Brønsted acid sites. Increasing the stability of pore walls and decreasing the rate of Si–O–Si group hydrolysis may result in improved apparent zeolite catalytic performance in aqueous medium. Authors thank B. W. Arey (PNNL) for HIM measurements, T. Huthwelker for support during Al XAFS measurements at the Swiss Light Source (PSI, Switzerland), J. Z. Hu and S. D. Burton (PNNL) for support during NMR experiments. This work was supported by the U. S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. MD acknowledges support by the Materials Synthesis and Simulation Across Scales (MS3 Initiative) conducted under Laboratory Directed Research & Development Program at PNNL. HIM imaging and NMR experiments were performed at the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the DOE Office of Science, Office of Biological

  10. Dehydrogenative Synthesis of Carboxylic Acids from Primary Alcohols and Hydroxide Catalyzed by a Ruthenium N-Heterocyclic Carbene Complex

    DEFF Research Database (Denmark)

    Santilli, Carola; Makarov, Ilya; Fristrup, Peter;

    2016-01-01

    Primary alcohols have been reacted with hydroxide and the ruthenium complex [RuCl2(IiPr)(p-cymene)] to afford carboxylic acids and dihydrogen. The dehydrogenative reaction is performed in toluene, which allows for a simple isolation of the products by precipitation and extraction. The transformat......Primary alcohols have been reacted with hydroxide and the ruthenium complex [RuCl2(IiPr)(p-cymene)] to afford carboxylic acids and dihydrogen. The dehydrogenative reaction is performed in toluene, which allows for a simple isolation of the products by precipitation and extraction...... reaction is most likely involved in this case. The kinetic isotope effect was determined to be 0.67 using 1-butanol as the substrate. A plausible catalytic cycle was characterized by DFT/B3LYP-D3 and involved coordination of the alcohol to the metal, β-hydride elimination, hydroxide attack...... on the coordinated aldehyde, and a second β-hydride elimination to furnish the carboxylate....

  11. FAME Production from Jatropha curcas Seed Oil via Calcium Oxide Catalyzed Transesterification and its Purification using Acid Activated Bentonite

    Directory of Open Access Journals (Sweden)

    Novizar Nazir

    2013-01-01

    Full Text Available This paper presents the study of transesterification of Jatropha curcas oil (JCO via environmentally benign process using calcium oxide as heterogeneous catalyst.  Response surface methodology (RSM based on central composite design (CCD was performed to optimize three reaction variables in this study.  The transesterification process variables were reaction time, x1 (60 minutes-120 minutes,   molar ratio of methanol: oil, x2 (5:1 – 13:1, and amount of catalyst,  x3 (0.5 % –1.50 % of mass fraction.  Since water washing method is not suitable to purify CaO synthesized fatty acid methyl esters (FAME,   the purification of as-synthesized FAME with acid-activated bentonites to eliminate the remaining calcium was also investigated.   It was found that the yield of JCO FAME could reach up to 94.35 % using the following reaction conditions: 79.33 minutes reaction time, 10.41:1 methanol:oil molar ratio and 0.99 %  catalyst at reaction temperature 65oC.  Among bentonites used in the purification,   2.5% of H2SO4-activated bentonite shows a good performance as decalcifying agent for FAME purification.  The properties of purified jatropha FAME were comparable to those of diesel and satisfied the international standard.

  12. The effect of metal ions as co-catalysts on acidic ionic liquid catalyzed single-step saccharification of corn stover in water.

    Science.gov (United States)

    Wiredu, Bernard; Amarasekara, Ananda S

    2015-01-01

    The effects of adding Cr(3+), Mn(2+), Fe(3+), Co(2+) Ni(2+), Cu(2+), Zn(2+) and La(3+) chlorides as co-catalysts to 1-(1-propylsulfonic)-3-methylimidazolium chloride acidic ionic liquid catalyzed saccharification of corn stover in aqueous medium was studied at 140-170 °C, by measuring the total reducing sugar (TRS) and glucose yields. The samples with Mn(2+), Fe(3+), Co(2+) as co-catalysts produced higher TRS yields compared to the sample without the metal ions. The Mn(2+) produced the highest catalytic effect enhancements and produced TRS yields of 68.0%, 72.9%, 90.2% and 87.9% at 140, 150, 160 and 170 °C respectively; whereas the corn stover samples without the Mn(2+) produced TRS yields of 42.9%, 52.3%, 54.4% and 53.5% at the same four temperatures. At higher temperatures of 160 and 170 °C, all metal ions studied produced significant enhancements in glucose yields, except Cr(3+). The addition of La(3+) as a co-catalyst produced the highest glucose yield improvement.

  13. Kinetics of an acid-base catalyzed reaction (aspartame degradation) as affected by polyol-induced changes in buffer pH and pK values.

    Science.gov (United States)

    Chuy, S; Bell, L N

    2009-01-01

    The kinetics of an acid-base catalyzed reaction, aspartame degradation, were examined as affected by the changes in pH and pK(a) values caused by adding polyols (sucrose, glycerol) to phosphate buffer. Sucrose-containing phosphate buffer solutions had a lower pH than that of phosphate buffer alone, which contributed, in part, to reduced aspartame reactivity. A kinetic model was introduced for aspartame degradation that encompassed pH and buffer salt concentrations, both of which change with a shift in the apparent pK(a) value. Aspartame degradation rate constants in sucrose-containing solutions were successfully predicted using this model when corrections (that is, lower pH, lower apparent pK(a) value, buffer dilution from the polyol) were applied. The change in buffer properties (pH, pK(a)) from adding sucrose to phosphate buffer does impact food chemical stability. These effects can be successfully incorporated into predictive kinetic models. Therefore, pH and pK(a) changes from adding polyols to buffer should be considered during food product development.

  14. Polarity Sensitive Bioorthogonally Applicable Far-Red Emitting Labels for Postsynthetic Nucleic Acid Labeling by Copper-Catalyzed and Copper-Free Cycloaddition.

    Science.gov (United States)

    Eördögh, Ádám; Steinmeyer, Jeannine; Peewasan, Krisana; Schepers, Ute; Wagenknecht, Hans-Achim; Kele, Péter

    2016-02-17

    Two series of new, water-soluble, membrane-permeable, far-red/NIR emitting benzothiazolium-based fluorescent labels with large Stokes' shifts were synthesized that can be conjugated to alkyne-modified biomolecules through their azide moiety via azide-alkyne cycloaddition. We have used these azide bearing labels to make fluorescent DNA constructs using copper-catalyzed "click" reaction. All dyes showed good or remarkable fluorescence intensity enhancement upon conjugation to DNA. We also investigated the possibility to incorporate the benzocyclooctyne motif through rigid (ethnynyl) or flexible (ethyl) linkers into the DNA, thus enabling copper-free labeling schemes. We observed that there is a marked difference between the two linkers applied in terms of optical properties of the labeled oligonucleotides. We have also tested the in vivo labeling potential of these newly synthesized dyes on HeLa cells previously transfected with cyclooctynylated DNA. Confocal fluorescent images showed that the dyes are all able to cross the membrane and suitable for background-fluorescence free fluorescent tagging of nucleic acids. Moreover, we have observed different accumulation of the two dye series in the endosomal particles, or in the nuclei, respectively. PMID:26786593

  15. A study of the acid-catalyzed hydrolysis of cellulose dissolved in ionic liquids and the factors influencing the dehydration of glucose and the formation of humins.

    Science.gov (United States)

    Dee, Sean J; Bell, Alexis T

    2011-08-22

    An investigation was carried out into the hydrolysis of cellulose dissolved in 1-ethyl-3-methylimidazolium chloride ([Emim][Cl]) and 1-butyl-3-methylimidazolium chloride ([Bmim][Cl]) catalyzed by mineral acids. Glucose, cellobiose, and 5-hydroxymethylfurfural (5-HMF) were observed as the primary reaction products. The initial rate of glucose formation was determined to be of first order in the concentrations of dissolved glucan and protons and of zero order in the concentration of water. The absence of a dependence on water concentration suggests that cleavage of the β-1,4-glycosidic linkages near chain ends is irreversible. The apparent activation energy for glucose formation is 96 kJ mol(-1). The absence of oligosaccharides longer than cellobiose suggests that cleavage of interior glycosidic bonds is reversible due to the slow diffusional separation of cleaved chains in the highly viscous glucan/ionic liquid solution. Progressive addition of water during the course of glucan hydrolysis inhibited the rate of glucose dehydration to 5-HMF and the formation of humins. The inhibition of glucose dehydration is attributed to stronger interaction of protons with water than the 2-OH atom of the pyranose ring of glucose, the critical step in the proposed mechanism for the formation of 5-HMF. The reduction in humin formation associated with water addition is ascribed to the lowered concentration of 5-HMF, since the formation of humins is suggested to proceed through the condensation polymerization of 5-HMF with glucose. PMID:21809450

  16. Selective Oxidation of Glycerol to Glyceric Acid in Base-Free Aqueous Solution at Room Temperature Catalyzed by Platinum Supported on Carbon Activated with Potassium Hydroxide

    KAUST Repository

    Tan, Hua

    2016-04-18

    Pt supported on KOH-activated mesoporous carbon (K-AMC) was used to catalyze glycerol oxidation under base-free conditions at room temperature. To study the relationship between the carbon surface chemistry and the catalytic performance of the K-AMC-based Pt catalysts, different levels of surface oxygen functional groups (SOFGs) on the AMC supports were induced by thermal treatment at different temperatures under inert or H2 gas. A strong effect of the surface chemistry was observed on AMC-supported Pt catalysts for glycerol oxidation. The presence of carboxylic acid groups impedes the adsorption of glycerol, which leads to the reduction of catalytic activity, whereas the presence of high-desorption-temperature SOFGs, such as phenol, ether, and carbonyl/quinone groups, provide hydrophilicity to the carbon surface that improves the adsorption of glycerol molecules on Pt metal surface, which is beneficial for the catalytic activity. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Synthesis of 1,8-Dioxo-octahydroxanthene Derivatives Catalyzed by p-Dodecylbenezenesulfonic Acid in Water

    Institute of Scientific and Technical Information of China (English)

    JIN,Tong-Shou; ZHANG,Jian-She; WANG,Ai-Qing; LI,Tong-Shuang

    2004-01-01

    @@ With the increasing concerns of the environment, more and more chemists are devoted to the research of the "green synthesis" which means that the reagent, solvent and catalyst are environmentally friendly in the organic chemical reactions. The importance of aqueous reaction is now generally recognized, and development of carbon-carbon bond-forming reactions that can be carried out in aqueous media is now one of the most challenging topics in organic synthesis.[1]Herein, we report a clean synthesis of 3,3,6,6-tetramethyl-9-aryl-1,8-dioxo-octahydroxanthene derivatives from aromatic aldehyde and 5,5-dimethyl-1,3-cyclohexadione using p-dodecylbenezenesulfonic acid (DBSA) as the catalyst in water.This method provides several advantages such as high yield, simple work-up procedure and environmental friendliness and water was chosen as a green solvent. All the products were characterized by m.p., 1H NMR, IR and elemental analyses.

  18. Hydrolysis of p-Nitrophenyl Picolinate Catalyzed by Mono-and Binuclear Transition Metal Complexes with Polyether Bridged Dihydroxamic Acid

    Institute of Scientific and Technical Information of China (English)

    李建章; 李鸿波; 冯发美; 谢家庆; 李慎新; 周波; 秦圣英

    2005-01-01

    Two polyether bridged dihydroxamic acids and their mono-and binuclear manganese(Ⅱ), zinc(Ⅱ) complexes have been synthesized and employed as models to mimic hydrolase in catalytic hydrolysis of p-nitrophenyl picolinate (PNPP). The reaction kinetics and the mechanism of hydrolysis of PNPP have been investigated. The kinetic mathematical model for PNPP cleaved by the complexes has been proposed. The effects of the different central metal ion, mono-and binuclear metal, the pseudo-macrocyclic polyether constructed by polyethoxy group of the complexes, and reactive temperature on the rate for catalytic hydrolysis of PNPP have been examined. The results showed that the transition metal dthydroxamates exhibited high catalytic activity to the hydrolysis of PNPP, the catalytic activity of binuclear complexes was higher than that of mononuclear ones, and the pseudo-macrocyclic polyether might synergetically activate H20 coordinated to metal ion with central metal ion together and promote the catalytic hydrolysis of PNPP.

  19. Hydrolysis of palm oil catalyzed by acid%棕榈油的酸催化水解工艺研究

    Institute of Scientific and Technical Information of China (English)

    张玲玲; 王晖

    2015-01-01

    以棕榈油为原料进行常压酸催化水解工艺研究。考察了反应时间、反应温度、催化剂用量、油水质量比及乳化剂用量对棕榈油水解反应的影响,得出棕榈油一次酸催化水解的最佳反应条件:反应时间7 h,反应温度100℃,催化剂浓硫酸用量7.5%,油水质量比1∶1,乳化剂磺酸用量0.5%;在最佳反应条件下棕榈油水解产物酸值(KOH)为192.77 mg/g,水解率达到91.96%。并研究出一套循环水解的工艺流程,实现油脂水解产物的循环利用,提高了水相中甘油的含量。%The hydrolysis of palm oil catalyzed by acid was studied. The effects of reaction time,reaction temperature,catalyst dosage,mass ratio of oil to water and emulsifier dosage on the hydrolysis of palm oil were investigated. The optimal reaction conditions of palm oil hydrolysis were obtained as follows:reaction time 7 h,reaction temperature 100℃,mass ratio of oil to water 1∶1,dosage of sulfonic acid used as emul-sifier 0. 5% and catalyst( concentrated sulfonic acid) dosage 7. 5%. Under the optimal reaction condi-tions,the acid value of the hydrolysates was up to 192. 77 mgKOH/g and the hydrolysis rate of palm oil was 91. 96%. A circulated hydrolysis process was designed, then the recycling of hydrolysates was real-ized,and the content of glycerin in the aqueous phase increased.

  20. An Efficient Synthesis of 3,4-Dihydropyrimidin-2(1H-Ones and Thiones Catalyzed by a Novel Brønsted Acidic Ionic Liquid under Solvent-Free Conditions

    Directory of Open Access Journals (Sweden)

    Yonghong Zhang

    2015-02-01

    Full Text Available We report here an efficient and green method for Biginelli condensation reaction of aldehydes, β-ketoesters and urea or thiourea catalyzed by Brønsted acidic ionic liquid [Btto][p-TSA] under solvent-free conditions. Compared to the classical Biginelli reaction conditions, the present method has the advantages of giving good yields, short reaction times, near room temperature conditions and the avoidance of the use of organic solvents and metal catalyst.

  1. Catalyzed Ester Synthesis Using Candida rugosa Lipase Entrapped by Poly(N-isopropylacrylamide-co-itaconic Acid Hydrogel

    Directory of Open Access Journals (Sweden)

    Nikola Milašinović

    2014-01-01

    Full Text Available This study reports the synthesis of polymeric matrices based on N-isopropylacrylamide and itaconic acid and its application for immobilization of lipase from Candida rugosa. The lipase was immobilized by entrapment method. Free and immobilized lipase activities, pH and temperature optima, and storage stability were investigated. The optimum temperature for free and entrapped lipase was found to be 40 and 45°C, while the optimum pH was observed at pH 7 and 8, respectively. Both hydrolytic activity in an aqueous medium and esterolytic activity in an organic medium have been evaluated. Maximum reaction rate (Vmax and Michaelis-Menten constants (Km were also determined for immobilized lipase. Storage stability of lipase was increased as a result of immobilization process. Furthermore, the operational stability and reusability of the immobilized lipase in esterification reaction have been studied, and it was observed that after 10 cycles, the residual activity for entrapped lipase was as high as 50%, implying that the developed hydrogel and immobilized system could provide a promising solution for the flavor ester synthesis at the industrial scale.

  2. Advanced Model Compounds for Understanding Acid-Catalyzed Lignin Depolymerization: Identification of Renewable Aromatics and a Lignin-Derived Solvent.

    Science.gov (United States)

    Lahive, Ciaran W; Deuss, Peter J; Lancefield, Christopher S; Sun, Zhuohua; Cordes, David B; Young, Claire M; Tran, Fanny; Slawin, Alexandra M Z; de Vries, Johannes G; Kamer, Paul C J; Westwood, Nicholas J; Barta, Katalin

    2016-07-20

    The development of fundamentally new approaches for lignin depolymerization is challenged by the complexity of this aromatic biopolymer. While overly simplified model compounds often lack relevance to the chemistry of lignin, the direct use of lignin streams poses significant analytical challenges to methodology development. Ideally, new methods should be tested on model compounds that are complex enough to mirror the structural diversity in lignin but still of sufficiently low molecular weight to enable facile analysis. In this contribution, we present a new class of advanced (β-O-4)-(β-5) dilinkage models that are highly realistic representations of a lignin fragment. Together with selected β-O-4, β-5, and β-β structures, these compounds provide a detailed understanding of the reactivity of various types of lignin linkages in acid catalysis in conjunction with stabilization of reactive intermediates using ethylene glycol. The use of these new models has allowed for identification of novel reaction pathways and intermediates and led to the characterization of new dimeric products in subsequent lignin depolymerization studies. The excellent correlation between model and lignin experiments highlights the relevance of this new class of model compounds for broader use in catalysis studies. Only by understanding the reactivity of the linkages in lignin at this level of detail can fully optimized lignin depolymerization strategies be developed. PMID:27310182

  3. Advanced Model Compounds for Understanding Acid-Catalyzed Lignin Depolymerization: Identification of Renewable Aromatics and a Lignin-Derived Solvent.

    Science.gov (United States)

    Lahive, Ciaran W; Deuss, Peter J; Lancefield, Christopher S; Sun, Zhuohua; Cordes, David B; Young, Claire M; Tran, Fanny; Slawin, Alexandra M Z; de Vries, Johannes G; Kamer, Paul C J; Westwood, Nicholas J; Barta, Katalin

    2016-07-20

    The development of fundamentally new approaches for lignin depolymerization is challenged by the complexity of this aromatic biopolymer. While overly simplified model compounds often lack relevance to the chemistry of lignin, the direct use of lignin streams poses significant analytical challenges to methodology development. Ideally, new methods should be tested on model compounds that are complex enough to mirror the structural diversity in lignin but still of sufficiently low molecular weight to enable facile analysis. In this contribution, we present a new class of advanced (β-O-4)-(β-5) dilinkage models that are highly realistic representations of a lignin fragment. Together with selected β-O-4, β-5, and β-β structures, these compounds provide a detailed understanding of the reactivity of various types of lignin linkages in acid catalysis in conjunction with stabilization of reactive intermediates using ethylene glycol. The use of these new models has allowed for identification of novel reaction pathways and intermediates and led to the characterization of new dimeric products in subsequent lignin depolymerization studies. The excellent correlation between model and lignin experiments highlights the relevance of this new class of model compounds for broader use in catalysis studies. Only by understanding the reactivity of the linkages in lignin at this level of detail can fully optimized lignin depolymerization strategies be developed.

  4. Impact of Biochemical Composition on Susceptibility of Algal Biomass to Acid-Catalyzed Pretreatment for Sugar and Lipid Recovery

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Tao; Van Wychen, Stefanie; Nagle, Nick; Pienkos, Philip T.; Laurens, Lieve M. L.

    2016-09-01

    One of the major challenges associated with algal biofuels production in a biorefinery-type setting is improving biomass utilization in its entirety, increasing the process energetic yields and providing economically viable and scalable co-product concepts. We focus on the impact of compositional characteristics of biomass on the susceptibility to pretreatment in order to maximize the valorization of algal biomass conversion for biofuels and bioproducts. The release of monomeric carbohydrates in the aqueous phase and extractability of the lipid fraction was measured based a response surface methodology to find significant explanatory variables and interaction terms. We studied the effect of harvest timing on the conversion yields, using three algal strains; Chlorella vulgaris and Scenedesmus acutus and Nannochloropsis granulata representing three different nutritional metabolic phases. Four cultivation conditions of high (= 90 gallon gasoline equivalent/ton biomass) value for a combined sugar- and lipid-based biofuels process were identified. These four conditions represent either mid or late stage harvest cultivation regimes. The results indicate that acid pretreatment has potential to be applicable for a vast range of biomass samples to obtain high energy yields, but that the exact conditions and optima are dependent on the strain and likely the starting composition of the biomass.

  5. Synthesis of acetylsalicylic acid catalyzed by carbon-based solid acid%碳基固体酸催化合成乙酰水杨酸

    Institute of Scientific and Technical Information of China (English)

    占昌朝; 曹小华; 严平; 王剑波; 余祖进; 江小平

    2012-01-01

    Carbon-based solid acid catalysts synthesized from starch andp-toluene sulphonic acid were characterized by FTIR, TG, BET, SEM and EDS. Its catalytic activity and effect of conventional heat and microwave heat on yield of acetylsalicylic acid were studied. The better condition was determined with single factor tests, which is as follows: the molar ratio of acetic anhydride to salicylic acid was 1.5 : 1, the weight ratio of carbon-based solid acid to salicylic acid was 5.8%, acylation reaction temperature was 76--80 ~C, reaction time was 25 min under conventional heat. The yield of acetylsalicylic acid was 82.1% and kept 78.2% after used five times under conventional heat. The carbon-based solid acid catalyst has high catalytic activity and retrievability under conventional heat, which are better than that of microwave heat.%以淀粉和对甲苯磺酸为原料合成了碳基固体酸催化剂,并采用FTIR、TG、BET、SEM和EDS对催化剂进行了表征。研究了催化剂对乙酰水杨酸合成反应的催化活性,并比较了常规加热和微波加热方式对反应的影响。通过单因素试验确定了较佳工艺条件为:乙酸酐与水杨酸物质的量比为1.5∶1,催化剂用量为水杨酸质量的5.8%,反应时间25 min,反应温度76~80℃。常规加热条件下收率82.1%,使用5次后,收率仍保持在78.2%。碳基固体酸催化剂在常规加热条件下催化性能和重复使用性能均优于微波加热条件反应。

  6. Visual detection of trace copper ions based on copper-catalyzed reaction of ascorbic acid with oxygen

    Science.gov (United States)

    Hou, Xin Yan; Chen, Shu; Shun, Lian Ju; Zhao, Yi Ni; Zhang, Zhi Wu; Long, Yun Fei; Zhu, Li

    2015-10-01

    A visual detection method for trace Cu2+ in aqueous solutions using triangular silver nanoplates (abbreviated as TAgNPs) as the probe was developed. The method is based on that TAgNPs could be corroded in sodium thiosulfate (Na2S2O3) solutions. The absorption spectrum of TAgNPs solution changed when it is corroded by Na2S2O3. The reaction of oxygen with ascorbic acid (Vc) in the presence of a low concentration of Cu2+ generates hydrogen peroxide that reacts with Na2S2O3, which leads the concentration of Na2S2O3 in the solution to be decreased. Therefore, the reaction between TAgNPs and the reacted mixture of Na2S2O3/Vc/Cu2+ was prevented efficiently. When the Na2S2O3 concentration and reaction time are constant, the decrease in the concentration of Na2S2O3 is directly proportional to the Cu2+ concentration. Thus, morphology, color, and maximum absorption wavelength of TAgNPs changed with the change of Cu2+ concentration. The changed maximum absorption wavelength of TAgNPs (Δλ) is proportional to Cu2+ concentration in the range from 7.5 × 10-9 to 5.0 × 10-7 M with a correlation coefficient of r = 0.9956. Moreover, color change of TAgNP solution was observed clearly over a Cu2+ concentration range from 7.5 × 10-8 to 5.0 × 10-7 M. This method has been used to detect the Cu2+ content of a human hair sample, and the result is in agreement with that obtained by the atomic absorption spectroscopy (AAS) method.

  7. Sulfate radical-induced degradation of Acid Orange 7 by a new magnetic composite catalyzed peroxymonosulfate oxidation process

    International Nuclear Information System (INIS)

    Graphical abstract: Organic dyes could be absorbed on the surface of the composite or dispersed in the solution. Sulfate radicals (SO4·−) generated by the synergistic reaction between peroxymonosulfate (PMS) and the composite, attacked the organic functional groups of the dyes molecules both adsorbed on the composite surface and dispersed in the solution, which resulted in the degradation of AO7 dye. - Highlights: • A new composite was synthesized successfully via microwave hydrothermal method. • The complete degradation in the system of FLCN and PMS can be achieved. • The catalytic behavior of FLCN can be reused at least for five times. • The AO7 degradation mechanism in the system of FLCN and PMS was demonstrated. - Abstract: We synthesized a novel magnetic composite, Fe3O4/Cu(Ni)Cr-LDH, as a heterogeneous catalyst for the degradation of organic dyes in the solution using sulfate radical-based advanced oxidation processes. The physicochemical properties of the composite synthesized via two-step microwave hydrothermal method were characterized by several techniques, such as X-ray diffraction (XRD), inductively coupled plasma (ICP), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). The degradation tests were performed at 25 °C with Acid Orange 7 (AO7) initial concentration of 25 mg/L and AO7/peroxymonosulfate (PMS) molar ratio of 1:10, which showed that the complete degradation by Fe3O4/Cu1.5Ni0.5Cr-LDH could be achieved and the mineralization rate could reach 46%. PMS was activated by Cu (II) and Fe (II/III) of Fe3O4/Cu(Ni)Cr-LDH to generate sulfate radicals (SO4·−). Subsequently, the organic functional groups of AO7 molecules were destroyed by sulfate radicals (SO4·−), inducing the degradation of AO7. Moreover, the catalytic behavior of the catalysts could be reused five times. Therefore, our work suggested that the Fe3O4/Cu(Ni)Cr-LDH composite could be applied widely for the treatment of organic dyes in wastewater

  8. Sulfate radical-induced degradation of Acid Orange 7 by a new magnetic composite catalyzed peroxymonosulfate oxidation process

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Dan; Ma, Xiaolong; Zhou, Jizhi [School of Environmental and Chemical Engineering, Shanghai University, No. 99 Shangda Road, Shanghai 200444 (China); Chen, Xi [Department of Earth and Environmental Engineering, Columbia University, West 120th Street, New York, NY 10027 (United States); Qian, Guangren, E-mail: grqian@shu.edu.cn [School of Environmental and Chemical Engineering, Shanghai University, No. 99 Shangda Road, Shanghai 200444 (China)

    2014-08-30

    Graphical abstract: Organic dyes could be absorbed on the surface of the composite or dispersed in the solution. Sulfate radicals (SO{sub 4}·{sup −}) generated by the synergistic reaction between peroxymonosulfate (PMS) and the composite, attacked the organic functional groups of the dyes molecules both adsorbed on the composite surface and dispersed in the solution, which resulted in the degradation of AO7 dye. - Highlights: • A new composite was synthesized successfully via microwave hydrothermal method. • The complete degradation in the system of FLCN and PMS can be achieved. • The catalytic behavior of FLCN can be reused at least for five times. • The AO7 degradation mechanism in the system of FLCN and PMS was demonstrated. - Abstract: We synthesized a novel magnetic composite, Fe{sub 3}O{sub 4}/Cu(Ni)Cr-LDH, as a heterogeneous catalyst for the degradation of organic dyes in the solution using sulfate radical-based advanced oxidation processes. The physicochemical properties of the composite synthesized via two-step microwave hydrothermal method were characterized by several techniques, such as X-ray diffraction (XRD), inductively coupled plasma (ICP), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). The degradation tests were performed at 25 °C with Acid Orange 7 (AO7) initial concentration of 25 mg/L and AO7/peroxymonosulfate (PMS) molar ratio of 1:10, which showed that the complete degradation by Fe{sub 3}O{sub 4}/Cu{sub 1.5}Ni{sub 0.5}Cr-LDH could be achieved and the mineralization rate could reach 46%. PMS was activated by Cu (II) and Fe (II/III) of Fe{sub 3}O{sub 4}/Cu(Ni)Cr-LDH to generate sulfate radicals (SO{sub 4}·{sup −}). Subsequently, the organic functional groups of AO7 molecules were destroyed by sulfate radicals (SO{sub 4}·{sup −}), inducing the degradation of AO7. Moreover, the catalytic behavior of the catalysts could be reused five times. Therefore, our work suggested that the Fe{sub 3}O{sub 4

  9. Lewis酸性离子液体催化合成丁二酸二异丙酯%Synthesis of succinic acid diisopropyl ester catalyzed by Lewis acid ionic liquids

    Institute of Scientific and Technical Information of China (English)

    赵地顺; 葛京京; 翟建华; 张娟; 刘猛帅; 李俊盼

    2014-01-01

    采用两步法制备了9种不同的Lewis酸性离子液体,采用1H NMR、FT-IR对离子液体的结构进行了表征,并系统地考察了其对丁二酸和异丙醇酯化反应的催化性能。结果表明,离子液体随着卤化物用量增加表现出更强的酸性。其中[Bmim]Br-Fe2Cl6催化合成丁二酸二异丙酯效果良好,催化剂用量为丁二酸质量的10.0%,反应温度100℃,反应时间4 h,酸醇摩尔比为1:5,丁二酸二异丙酯收率为88.9%,酯化率达92.7%。离子液体重复使用6次后,产品收率下降1.7%。%Nine kinds of different Lewis acid ionic liquids were synthesized by two-step process and their structures were characterized with 1H NMR and FT-IR. Lewis acid ionic liquids prepared were used to catalyze the esterification reaction of succinic acid and isopropyl alcohol. With the increase of dosage of halide, the ionic liquids showed stronger acidity. [Bmim]Br-Fe2Cl6 had the best catalytic performance, and optimal conditions for the synthesis of succinic acid diisopropyl ester were obtained as follows, amount of catalyst 10.0%(g/g)of succinic acid, reaction temperature 100℃ and reaction time 4 h, succinic acid and isopropyl alcohol ratio 1:5. Under the optimal conditions, the yield of succinic acid diisopropyl ester was up to 88.9%, esterification rate was 92.7%.The catalyst was recycled 6 times, and the yield of succinic acid diisopropyl ester only decreased by 1.7%.

  10. Inhibition of lactoperoxidase-catalyzed 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) and tyrosine oxidation by tyrosine-containing random amino acid copolymers.

    Science.gov (United States)

    Clausen, Morten R; Skibsted, Leif H; Stagsted, Jan

    2008-09-24

    Oxidation of 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) by lactoperoxidase was found to be inhibited by tyrosine-containing random amino acid copolymers but not by tyrosine. Both electrostatic effects and polymer size were found to be important by comparison of negatively and positively charged copolymers of varying lengths, with poly(Glu, Tyr)4:1 ([E 4Y 1] approximately 40) as the strongest competitive inhibitor (EC 50 approximately 20 nM). This polymer did not form dityrosine in the presence of lactoperoxidase (LPO) and peroxide. Furthermore, incubation with tert-butyl hydroperoxide, as opposed to hydrogen peroxide, resulted in a peculiar long lag phase of the reaction between the redox intermediate compound II and [E 4Y 1] approximately 40, indicating a very tight association between enzyme and inhibitor. We propose that interactions between multiple positively charged areas on the surface of LPO and the polymer are required for optimal inhibition.

  11. Palladium-phosphinous acid complexes catalyzed Suzuki cross-coupling reaction of heteroaryl bromides with phenylboronic acid in water/alcoholic solvents

    Institute of Scientific and Technical Information of China (English)

    Ben Li; Cuiping Wang; Guang Chen; Zhiqiang Zhang

    2013-01-01

    Highly active,air-stable and water-soluble palladium-phosphinous acid complexes have been applied to Suzuki cross-coupling reaction of heteroaryl bromides under mild conditions in water/alcoholic solvents.Suzuki cross-coupling reaction of heteroaryl bromides with phenylboronic acid occurred efficiently using palladium phosphinous acid complexes (POPd) and phase transfer catalyst (tetrabutylammonium bromide and polyethylene glycol) in water/ethanol mixture,water/propanol mixture and neat water respectively,the corresponding yields of cross-coupling heteroaryl-aryls were satisfied.The tert-butyl substituted ligand di-tert-butylphosphino in combination with POPd was found to be more active than the same family derived catalysts dipalladium complexes POPdl and POPd2,and other two kinds of Pd-catalysts Pd(PPh3)4 and Pd2(dba)3.The mechanism of Suzuki cross-coupling reaction between heteroaryl bromides and phenylboronic acid in water was proposed with respect to the key role of phase transfer catalyst on the transmetallation step.Compared with other solid phase transfer catalysts,TBAB was tested as the ideal one.The alkalinity of base and the molar proportion between POPd and TBAB were investigated in water and alcoholic solvents.Notably,in the presence of TBAB adding alcoholic solvents into water enhanced the yields of target products.However in terms of the liquid phase transfer catalyst of PEGs,mixing water into PEGs could slightly decrease the yields with respect to the water free PEGs bulk phase,which was probably due to the homogenous liquid conditions in pure PEGs and weak interactions between PEGs and heteroaryl bromide molecules in water depending on their molecular chain lengths.

  12. Effect of acid-catalyzed formation rates of benzimidazole-linked polymers on porosity and selective CO2 capture from gas mixtures.

    Science.gov (United States)

    Altarawneh, Suha; İslamoğlu, Timur; Sekizkardes, Ali Kemal; El-Kaderi, Hani M

    2015-04-01

    Benzimidazole-linked polymers (BILPs) are emerging candidates for gas storage and separation applications; however, their current synthetic methods offer limited control over textural properties which are vital for their multifaceted use. In this study, we investigate the impact of acid-catalyzed formation rates of the imidazole units on the porosity levels of BILPs and subsequent effects on CO2 and CH4 binding affinities and selective uptake of CO2 over CH4 and N2. Treatment of 3,3'-Diaminobenzidine tetrahydrochloride hydrate with 1,2,4,5-tetrakis(4-formylphenyl)benzene and 1,3,5-(4-formylphenyl)-benzene in anhydrous DMF afforded porous BILP-15 (448 m(2) g(-1)) and BILP-16 (435 m(2) g(-1)), respectively. Alternatively, the same polymers were prepared from the neutral 3,3'-Diaminobenzidine and catalytic amounts of aqueous HCl. The resulting polymers denoted BILP-15(AC) and BILP-16(AC) exhibited optimal surface areas; 862 m(2) g(-1) and 643 m(2) g(-1), respectively, only when 2 equiv of HCl (0.22 M) was used. In contrast, the CO2 binding affinity (Qst) dropped from 33.0 to 28.9 kJ mol(-1) for BILP-15 and from 32.0 to 31.6 kJ mol(-1) for BILP-16. According to initial slope calculations at 273 K/298 K, a notable change in CO2/N2 selectivity was observed for BILP-15(AC) (61/50) compared to BILP-15 (83/63). Similarly, ideal adsorbed solution theory (IAST) calculations also show the higher specific surface area of BILP-15(AC) and BILP-16(AC) compromises their CO2/N2 selectivity.

  13. Hydrogen Isotope Measurements of Organic Acids and Alcohols by Pyrolysis-GC-MS-TC-IRMS: Application to Analysis of Experimentally Derived Hydrothermal Mineral-Catalyzed Organic Products

    Science.gov (United States)

    Socki, Richard A.; Fu, Qi; Niles, Paul B.; Gibson, Everett K., Jr.

    2012-01-01

    We report results of experiments to measure the H isotope composition of organic acids and alcohols. These experiments make use of a pyroprobe interfaced with a GC and high temperature extraction furnace to make quantitative H isotope measurements. This work compliments our previous work that focused on the extraction and analysis of C isotopes from the same compounds [1]. Together with our carbon isotope analyses our experiments serve as a "proof of concept" for making C and H isotope measurements on more complex mixtures of organic compounds on mineral surfaces in abiotic hydrocarbon formation processes at elevated temperatures and pressures. Our motivation for undertaking this work stems from observations of methane detected within the Martian atmosphere [2-5], coupled with evidence showing extensive water-rock interaction during Mars history [6-8]. Methane production on Mars could be the result of synthesis by mineral surface-catalyzed reduction of CO2 and/or CO by Fischer-Tropsch Type (FTT) reactions during serpentization [9,10]. Others have conducted experimental studies to show that FTT reactions are plausible mechanisms for low-molecular weight hydrocarbon formation in hydrothermal systems at mid-ocean ridges [11-13]. Our H isotope measurements utilize an analytical technique combining Pyrolysis-Gas Chromatograph-Mass Spectrometry-High Temperature Conversion-Isotope Ratio Mass Spectrometry (Py-GC-MS-TC-IRMS). This technique is designed to carry a split of the pyrolyzed GC-separated product to a Thermo DSQII quadrupole mass spectrometer as a means of making qualitative and semi-quantitative compositional measurements of separated organic compounds, therefore both chemical and isotopic measurements can be carried out simultaneously on the same sample.

  14. Palladium-Catalyzed Asymmetric Conjugate Addition of Arylboronic Acids to Five-, Six-, and Seven-Membered β-Substituted Cyclic Enones: Enantioselective Construction of All-Carbon Quaternary Stereocenters

    KAUST Repository

    Kikushima, Kotaro

    2011-05-11

    The first enantioselective Pd-catalyzed construction of all-carbon quaternary stereocenters via 1,4-addition of arylboronic acids to β-substituted cyclic enones is reported. Reaction of a wide range of arylboronic acids and cyclic enones using a catalyst prepared from Pd(OCOCF(3))(2) and a chiral pyridinooxazoline ligand yields enantioenriched products bearing benzylic stereocenters. Notably, this transformation is tolerant to air and moisture, providing a practical and operationally simple method of synthesizing enantioenriched all-carbon quaternary stereocenters.

  15. Understanding the Mechanism of the Hydrogen Abstraction from Arachidonic Acid Catalyzed by the Human Enzyme 15-Lipoxygenase-2. A Quantum Mechanics/Molecular Mechanics Free Energy Simulation.

    Science.gov (United States)

    Suardíaz, Reynier; Jambrina, Pablo G; Masgrau, Laura; González-Lafont, Àngels; Rosta, Edina; Lluch, José M

    2016-04-12

    Lipoxygenases (LOXs) are a family of enzymes involved in the biosynthesis of several lipid mediators. In the case of human 15-LOX, the 15-LOX-1 and 15-LOX-2 isoforms show slightly different reaction regiospecificity and substrate specificity, indicating that substrate binding and recognition may be different, a fact that could be related to their different biological role. Here, we have used long molecular dynamics simulations, QM(DFT)/MM potential energy and free energy calculations (using the newly developed DHAM method), to investigate the binding mode of the arachidonic acid (AA) substrate into 15-LOX-2 and the rate-limiting hydrogen-abstraction reaction 15-LOX-2 catalyzes. Our results strongly indicate that hydrogen abstraction from C13 in 15-LOX-2 is only consistent with the "tail-first" orientation of AA, with its carboxylate group interacting with Arg429, and that only the pro-S H13 hydrogen will be abstracted (being the pro-R H13 and H10 too far from the acceptor oxygen atom). At the B3LYP/6-31G(d) level the potential and free energy barriers for the pro-S H13 abstraction of AA by 15-LOX-2 are 18.0 and 18.6 kcal/mol, respectively. To analyze the kinetics of the hydrogen abstraction process, we determined a Markov model corresponding to the unbiased simulations along the state-discretized reaction coordinate. The calculated rates based on the second largest eigenvalue of the Markov matrices agree well with experimental measurements, and also provide the means to directly determine the pre-exponential factor for the reaction by comparing with the free energy barrier height. Our calculated pre-exponential factor is close to the value of kBT/h. On the other hand, our results suggest that the spin inversion of the complete system (including the O2 molecule) that is required to happen at some point along the full process to lead to the final hydroperoxide product, is likely to take place during the hydrogen transfer, which is a proton coupled electron transfer

  16. Process Condition Optimization of the a-linolenic Acid Catalyzed by Pichia pastoris%巴斯德毕赤酵母催化生成a-亚麻酸的工艺条件优化

    Institute of Scientific and Technical Information of China (English)

    冯康; 葛军军; 张昕欣

    2015-01-01

    利用正交实验优化了巴斯德毕赤酵母催化硬脂酸生成a-亚麻酸的工艺条件,结果显示催化时巴斯德毕赤酵母接种量对催化效率影响显著,在此基础上得到的最佳催化条件为pH值6.5,硬脂酸乙醇饱和溶液加量4 mL,巴斯德毕赤酵母接种量为1 mL。在此条件下,以a-亚麻酸甲酯气相色谱积分面积(18:3)/硬脂酸甲酯气相色谱积分面积(18:0)为标准计算出的转化率为7.16。%For a-linolenic acid production, process condition optimization of stearic acide catalyzed by Pichia pastoris was done by orthogonal design. The results indicated that there was a significant effect of the catalytic efficiency by inoculum size of Pichia pastoris. On this basis, the best catalyzed conditions were obtained:pH of 6. 5, addition amount of saturated ethanol solution of stearic acide was 4 mL, inoculum size of Pichia pastoris was 1 mL. Under the condition, conversion of stearic acide toa-linolenic acid was 7. 16.

  17. Study on Biodiesel Preparation by a Two-step Catalyzed Process from Waste Cooking Oil with a High Acid Value%两步法利用高酸值潲水油制备生物柴油研究

    Institute of Scientific and Technical Information of China (English)

    马顺; 汪勇; 唐书泽

    2011-01-01

    A two-step catalyzed process was developed to prepare biodiesel from waste cooking oil (WCO) in this study.Free fatty acid of WCO was esterified with methanol catalyzed by polyferric sulfate in the first step, and then triglyceride of WCO was transesterified with methanol catalyzed by potassium hydroxide.Results showed that polyferric sulfate had strong activity to catalyze the esterification.The optimal parameters of esterification obtained by response surface as follows :5.87 % ( of the WCO mass) of polyferric sulfate, 108.7% (of the WCO mass) of methanol,6.0 h of reaction time and 80 ℃ of reaction temperature.Under this condition, the AV reached as low as 2.20 mgKOH/g,and the esterification rate was 97.71%.The yield of purified biodiesel was 98.20% from the crude biodiesel obtained by this two-step process by molecular distillation at 110 ℃.Composition of fatty acid methyl ester of the purified biodiesel was analyzed by gas chromatography (GC).Some physical and chemical properties of purified biodiesel were detected according to national standards for biodiesel.%以潲水油为原料,采用两步催化法制备生物柴油.先用聚合硫酸铁催化潲水油中游离脂肪酸和甲醇酯转化为脂肪酸甲酯,然后再通过碱催化剩余的甘油三酯进行酯交换反应.通过响应面试验设计优化酯化反应,结果表明,在反应时间6.0 h、甲醇用量108.7%(质量比,按油质量)、催化剂用量5.87%(质量比,按油质量)、反应温度80℃下,酸值可达到2.20 mgKOH/g,即酯化率为97.71%.在¨0℃下对经两步催化得到的生物柴油进行分子蒸馏,得率为98.20%,测定了生物柴油的脂肪酸甲酯组成,按照国标检测了纯化的生物柴油的物化性质.

  18. Hydrogen Peroxide-Resistant CotA and YjqC of Bacillus altitudinis Spores Are a Promising Biocatalyst for Catalyzing Reduction of Sinapic Acid and Sinapine in Rapeseed Meal

    Science.gov (United States)

    Zhang, Yanzhou; Li, Xunhang; Hao, Zhikui; Xi, Ruchun; Cai, Yujie; Liao, Xiangru

    2016-01-01

    For the more efficient detoxification of phenolic compounds, a promising avenue would be to develop a multi-enzyme biocatalyst comprising peroxidase, laccase and other oxidases. However, the development of this multi-enzyme biocatalyst is limited by the vulnerability of fungal laccases and peroxidases to hydrogen peroxide (H2O2)-induced inactivation. Therefore, H2O2-resistant peroxidase and laccase should be exploited. In this study, H2O2-stable CotA and YjqC were isolated from the outer coat of Bacillus altitudinis SYBC hb4 spores. In addition to the thermal and alkali stability of catalytic activity, CotA also exhibited a much higher H2O2 tolerance than fungal laccases from Trametes versicolor and Trametes trogii. YjqC is a sporulation-related manganese (Mn) catalase with striking peroxidase activity for sinapic acid (SA) and sinapine (SNP). In contrast to the typical heme-containing peroxidases, the peroxidase activity of YjqC was also highly resistant to inhibition by H2O2 and heat. CotA could also catalyze the oxidation of SA and SNP. CotA had a much higher affinity for SA than B. subtilis CotA. CotA and YjqC rendered from B. altitudinis spores had promising laccase and peroxidase activities for SA and SNP. Specifically, the B. altitudinis spores could be regarded as a multi-enzyme biocatalyst composed of CotA and YjqC. The B. altitudinis spores were efficient for catalyzing the degradation of SA and SNP in rapeseed meal. Moreover, efficiency of the spore-catalyzed degradation of SA and SNP was greatly improved by the presence of 15 mM H2O2. This effect was largely attributed to synergistic biocatalysis of the H2O2-resistant CotA and YjqC toward SA and SNP. PMID:27362423

  19. Hydrogen Peroxide-Resistant CotA and YjqC of Bacillus altitudinis Spores Are a Promising Biocatalyst for Catalyzing Reduction of Sinapic Acid and Sinapine in Rapeseed Meal.

    Directory of Open Access Journals (Sweden)

    Yanzhou Zhang

    Full Text Available For the more efficient detoxification of phenolic compounds, a promising avenue would be to develop a multi-enzyme biocatalyst comprising peroxidase, laccase and other oxidases. However, the development of this multi-enzyme biocatalyst is limited by the vulnerability of fungal laccases and peroxidases to hydrogen peroxide (H2O2-induced inactivation. Therefore, H2O2-resistant peroxidase and laccase should be exploited. In this study, H2O2-stable CotA and YjqC were isolated from the outer coat of Bacillus altitudinis SYBC hb4 spores. In addition to the thermal and alkali stability of catalytic activity, CotA also exhibited a much higher H2O2 tolerance than fungal laccases from Trametes versicolor and Trametes trogii. YjqC is a sporulation-related manganese (Mn catalase with striking peroxidase activity for sinapic acid (SA and sinapine (SNP. In contrast to the typical heme-containing peroxidases, the peroxidase activity of YjqC was also highly resistant to inhibition by H2O2 and heat. CotA could also catalyze the oxidation of SA and SNP. CotA had a much higher affinity for SA than B. subtilis CotA. CotA and YjqC rendered from B. altitudinis spores had promising laccase and peroxidase activities for SA and SNP. Specifically, the B. altitudinis spores could be regarded as a multi-enzyme biocatalyst composed of CotA and YjqC. The B. altitudinis spores were efficient for catalyzing the degradation of SA and SNP in rapeseed meal. Moreover, efficiency of the spore-catalyzed degradation of SA and SNP was greatly improved by the presence of 15 mM H2O2. This effect was largely attributed to synergistic biocatalysis of the H2O2-resistant CotA and YjqC toward SA and SNP.

  20. Hydrogen Peroxide-Resistant CotA and YjqC of Bacillus altitudinis Spores Are a Promising Biocatalyst for Catalyzing Reduction of Sinapic Acid and Sinapine in Rapeseed Meal.

    Science.gov (United States)

    Zhang, Yanzhou; Li, Xunhang; Hao, Zhikui; Xi, Ruchun; Cai, Yujie; Liao, Xiangru

    2016-01-01

    For the more efficient detoxification of phenolic compounds, a promising avenue would be to develop a multi-enzyme biocatalyst comprising peroxidase, laccase and other oxidases. However, the development of this multi-enzyme biocatalyst is limited by the vulnerability of fungal laccases and peroxidases to hydrogen peroxide (H2O2)-induced inactivation. Therefore, H2O2-resistant peroxidase and laccase should be exploited. In this study, H2O2-stable CotA and YjqC were isolated from the outer coat of Bacillus altitudinis SYBC hb4 spores. In addition to the thermal and alkali stability of catalytic activity, CotA also exhibited a much higher H2O2 tolerance than fungal laccases from Trametes versicolor and Trametes trogii. YjqC is a sporulation-related manganese (Mn) catalase with striking peroxidase activity for sinapic acid (SA) and sinapine (SNP). In contrast to the typical heme-containing peroxidases, the peroxidase activity of YjqC was also highly resistant to inhibition by H2O2 and heat. CotA could also catalyze the oxidation of SA and SNP. CotA had a much higher affinity for SA than B. subtilis CotA. CotA and YjqC rendered from B. altitudinis spores had promising laccase and peroxidase activities for SA and SNP. Specifically, the B. altitudinis spores could be regarded as a multi-enzyme biocatalyst composed of CotA and YjqC. The B. altitudinis spores were efficient for catalyzing the degradation of SA and SNP in rapeseed meal. Moreover, efficiency of the spore-catalyzed degradation of SA and SNP was greatly improved by the presence of 15 mM H2O2. This effect was largely attributed to synergistic biocatalysis of the H2O2-resistant CotA and YjqC toward SA and SNP. PMID:27362423

  1. Phenylalanine Ammonia-Lyase-Catalyzed Deamination of an Acyclic Amino Acid: Enzyme Mechanistic Studies Aided by a Novel Microreactor Filled with Magnetic Nanoparticles.

    Science.gov (United States)

    Weiser, Diána; Bencze, László Csaba; Bánóczi, Gergely; Ender, Ferenc; Kiss, Róbert; Kókai, Eszter; Szilágyi, András; Vértessy, Beáta G; Farkas, Ödön; Paizs, Csaba; Poppe, László

    2015-11-01

    Phenylalanine ammonia-lyase (PAL), found in many organisms, catalyzes the deamination of l-phenylalanine (Phe) to (E)-cinnamate by the aid of its MIO prosthetic group. By using PAL immobilized on magnetic nanoparticles and fixed in a microfluidic reactor with an in-line UV detector, we demonstrated that PAL can catalyze ammonia elimination from the acyclic propargylglycine (PG) to yield (E)-pent-2-ene-4-ynoate. This highlights new opportunities to extend MIO enzymes towards acyclic substrates. As PG is acyclic, its deamination cannot involve a Friedel-Crafts-type attack at an aromatic ring. The reversibility of the PAL reaction, demonstrated by the ammonia addition to (E)-pent-2-ene-4-ynoate yielding enantiopure l-PG, contradicts the proposed highly exothermic single-step mechanism. Computations with the QM/MM models of the N-MIO intermediates from L-PG and L-Phe in PAL show similar arrangements within the active site, thus supporting a mechanism via the N-MIO intermediate.

  2. Phenylalanine Ammonia-Lyase-Catalyzed Deamination of an Acyclic Amino Acid: Enzyme Mechanistic Studies Aided by a Novel Microreactor Filled with Magnetic Nanoparticles.

    Science.gov (United States)

    Weiser, Diána; Bencze, László Csaba; Bánóczi, Gergely; Ender, Ferenc; Kiss, Róbert; Kókai, Eszter; Szilágyi, András; Vértessy, Beáta G; Farkas, Ödön; Paizs, Csaba; Poppe, László

    2015-11-01

    Phenylalanine ammonia-lyase (PAL), found in many organisms, catalyzes the deamination of l-phenylalanine (Phe) to (E)-cinnamate by the aid of its MIO prosthetic group. By using PAL immobilized on magnetic nanoparticles and fixed in a microfluidic reactor with an in-line UV detector, we demonstrated that PAL can catalyze ammonia elimination from the acyclic propargylglycine (PG) to yield (E)-pent-2-ene-4-ynoate. This highlights new opportunities to extend MIO enzymes towards acyclic substrates. As PG is acyclic, its deamination cannot involve a Friedel-Crafts-type attack at an aromatic ring. The reversibility of the PAL reaction, demonstrated by the ammonia addition to (E)-pent-2-ene-4-ynoate yielding enantiopure l-PG, contradicts the proposed highly exothermic single-step mechanism. Computations with the QM/MM models of the N-MIO intermediates from L-PG and L-Phe in PAL show similar arrangements within the active site, thus supporting a mechanism via the N-MIO intermediate. PMID:26345352

  3. Catalyzing RE Project Development

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, Kate; Elgqvist, Emma; Walker, Andy; Cutler, Dylan; Olis, Dan; DiOrio, Nick; Simpkins, Travis

    2016-09-01

    This poster details how screenings done with REopt - NREL's software modeling platform for energy systems integration and optimization - are helping to catalyze the development of hundreds of megawatts of renewable energy.

  4. Catalyzing alignment processes

    DEFF Research Database (Denmark)

    Lauridsen, Erik Hagelskjær; Jørgensen, Ulrik

    2004-01-01

    This paper describes how environmental management systems (EMS) spur the circulation of processes that support the constitution of environmental issues as specific environ¬mental objects and objectives. EMS catalyzes alignmentprocesses that produce coherence among the different elements involved ...

  5. Muon Catalyzed Fusion

    Science.gov (United States)

    Armour, Edward A.G.

    2007-01-01

    Muon catalyzed fusion is a process in which a negatively charged muon combines with two nuclei of isotopes of hydrogen, e.g, a proton and a deuteron or a deuteron and a triton, to form a muonic molecular ion in which the binding is so tight that nuclear fusion occurs. The muon is normally released after fusion has taken place and so can catalyze further fusions. As the muon has a mean lifetime of 2.2 microseconds, this is the maximum period over which a muon can participate in this process. This article gives an outline of the history of muon catalyzed fusion from 1947, when it was first realised that such a process might occur, to the present day. It includes a description of the contribution that Drachrnan has made to the theory of muon catalyzed fusion and the influence this has had on the author's research.

  6. A Novel poly {(2,5-diyl thiophene) (2-Thiophenyl Methine)} from the Acid-Catalyzed Polycondensation of thiophene and thiophene-2-carbanaldehyde

    Science.gov (United States)

    Belmokhtar, A.; Yahiaoui, A.; Hachemaoui, A.; Sahli, N.; Benyoucef, A.; Belfedal, A.; Belbachir, M.

    2012-02-01

    Conjugated poly [(thiophene methine) have been synthesized by a simple method: Condensation of thiophene-2-carbaldehyde with thiophene, catalyzed by Maghnite-H+, which is an exchanged montmorillonite sheet silicate with protons to produce Maghnite-H+ non-toxic cationic catalyst, and characterized by FT-IR and UV-Vis. The result reveals that the yield of PTTM increase with time and amount of Mag-H. The results obtained with optical measurements and analyzed by different models, show clearly that our material (PTTM) is a good semi-conductor, when the average gap around 5 eV. The effect of the amount of Mag-H+, and the time of polymer was studied.

  7. Lewis acid catalyzed cyclization of glycals/2-deoxy-D-ribose with arylamines: additional findings on product structure and reaction diastereoselectivity.

    Science.gov (United States)

    Du, Chengtang; Li, Fulong; Zhang, Xuefeng; Hu, Wenxiang; Yao, Qizheng; Zhang, Ao

    2011-11-01

    The cyclization reactions of arylamines with 2-deoxy-D-ribose or glycals were reinvestigated in the current report. In the montmorillonite KSF- or InCl(3)-initiated reactions of 2-deoxy-D-ribose with arylamines, a pair of diastereomeric tetrahydro-2H-pyran-fused tetrahydroquinolines was obtained in a nearly 1:1 ratio where the structure of one diastereomer was incorrectly assigned in the literature. Meanwhile, the diastereoselectivity in InBr(3)-catalyzed cyclization of glycals with arylamines was also incorrectly reported previously. It was found that high diastereomeric selectivity was achieved only when a C5-substituted glycal was used; otherwise, a pair of diastereomers was obtained in moderate yield with 1:1 diastereomeric ratio. Furthermore, tetrahydrofuran-fused tetrahydroquinolines 5b and 5b' were also prepared successfully by using TBDPS-protected ribose as the glycal precursor and montmorillonite KSF as the activator.

  8. Effect of low-molecular-weight organic acids on photo-degradation of phenanthrene catalyzed by Fe(III)-smectite under visible light.

    Science.gov (United States)

    Jia, Hanzhong; Chen, Hongxia; Nulaji, Gulimire; Li, Xiyou; Wang, Chuanyi

    2015-11-01

    The photolysis of polycyclic aromatic hydrocarbons (PAHs) is potentially an important process for its transformation and fate on contaminated soil surfaces. In this study, phenanthrene is employed as a model to explore PAH photodegradation with the assistance of Fe(III)-smectite under visible-light while focusing on roles played by five low-molecular-weight organic acids (LMWOAs), i.e., malic acid, oxalic acid, citric acid, ethylenediaminetetraacetic acid (EDTA), and nitrilotriacetic acid. Our results show that oxalic acid is most effective in promoting the photodegradation of phenanthrene, while only a slight increase in the rate of phenanthrene photodegradation is observed in the presence of malic acid. Electron paramagnetic resonance experiments confirm the formation of CO2(-) radicals in the presence of malic and oxalic acid, which provides strong evidence for generating OH and subsequent photoreaction pathways. The presence of EDTA or nitrilotriacetic acid significantly inhibits both Fe(II) formation and phenanthrene photodegradation because these organic anions tend to chelate with Fe(III), leading to decreases in the electron-accepting potential of Fe(III)-smectite and a weakened interaction between phenanthrene and Fe(III)-smectite. These observations provide valuable insights into the transformation and fate of PAHs in the natural soil environment and demonstrate the potential for using some LMWOAs as additives for the remediation of contaminated soil.

  9. Synthesis of 2,4-diisopropyl-5,5-dimethyl- 1,3-dioxane catalyzed by Brφnsted acidic ionic liquids

    Institute of Scientific and Technical Information of China (English)

    WANG WenJuan; WANG YouFei; CHENG WenPing; WANG Jian; YANG JianGuo; HE MingYuan

    2008-01-01

    The acetalization reactions of isobutyraldehyde with 2,2,4-trimethyl-1,3-pentanediol (TMPD) for the synthesis of 2,4-diisopropyl-5,5-dimethyl-1,3-dioxane were carried out under mild reaction conditions using four water-stable Brφnsted-acidic task-specific ionic liquids ([HMIM]BF4, -SO3H functionalized acidic ionic liquid, -COOH functionalized acidic ionic liquid, [NMP][HSO4]) as environmentally benign catalysts for the first time. The process is highly effective and very selective. The -COOH functional-ized Bronsted acidic ionic liquid with the two acid sites (IL-3) exhibited the most excellent catalytic performance under mild reaction conditions. The --COOH functionalized Brφnsted acidic ionic liquid could be conveniently separated from the product and easily recycled in subsequent runs.

  10. SYNTHESIS OF ISOAMYL SALICYLATE CATALYZED BY GERMANOTUNGSTIC ACID CATALYST%锗钨酸催化合成水杨酸异戊酯

    Institute of Scientific and Technical Information of China (English)

    蒋维

    2000-01-01

    Isoamyl salicylate was synthesized by using germanotungtic acid as catalyst.The effects of the amaunt of catalyst,the molar ratio of salicycic acid of isoamy l alcohol,the reaction temperature and the reaction time on the yield of ester w ere studied.The optimum reaction conditions were 1.3∶100 (mass ratio) of cataly st to reactants,1∶2.5 (molar ratio) of acid to alcohol,135~153℃ being satisfa ctary reaction temperature and reaction time suitable being 3h.Under such condit ion,the yield of ester was up to 94%.Germanotungtic acid catalyst can be used re peatedly.

  11. Ultrasound-assisted MnO2 catalyzed homolysis of peracetic acid for phenol degradation: The assessment of process chemistry and kinetics

    NARCIS (Netherlands)

    Rokhina, E.V.; Makarova, K.; Lathinen, M.; Golovina, E.A.; As, van H.; Virkutyte, J.

    2013-01-01

    The combination of peracetic acid (PAA) and heterogeneous catalyst (MnO2) was used for the degradation of phenol in an aqueous solution in the presence of ultrasound irradiation (US). As a relevant source of free radicals (e.g. OH), peracetic acid was comprehensively studied by means of electron spi

  12. Kinetics of phosphotungstic acid catalyzed oxidation of propan-1,3-diol and butan-1,4-diol by N-chlorosaccharin

    Directory of Open Access Journals (Sweden)

    Sanjay Kumar Singh

    2011-09-01

    Full Text Available The kinetic studies of N-chlorosaccharin (NCSA oxidation of propan-1,3-diol and butan-1,4-diol have been reported in presence of phophotungstic acid and in aqueous acetic acid medium. The reactions follow first-order in NCSA and one to zero order with respect to substrate and phosphotungstic acid. Increase in the concentration of added perchloric acid increases the rate of oxidation. A negative effect on the oxidation rate is observed for solvent whereas the ionic strength does not influence the rate of reaction. Addition of the reaction product, saccharin, exhibited retarding effect. Various activation parameters have been evaluated. The products of the reactions were identified as the corresponding aldehydes. A suitable scheme of mechanism consistent with the experimental results has been proposed.

  13. The effect of the distance between acidic site and basic site immobilized on mesoporous solid on the activity in catalyzing aldol condensation

    Science.gov (United States)

    Yu, Xiaofang; Yu, Xiaobo; Wu, Shujie; Liu, Bo; Liu, Heng; Guan, Jingqi; Kan, Qiubin

    2011-02-01

    Acid-base bifunctional heterogeneous catalysts containing carboxylic and amine groups, which were immobilized at defined distance from one another on the mesoporous solid were synthesized by immobilizing lysine onto carboxyl-SBA-15. The obtained materials were characterized by X-ray diffraction (XRD), N 2 adsorption, Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron micrographs (SEM), transmission electron micrographs (TEM), elemental analysis, and back titration. Proximal-C-A-SBA-15 with a proximal acid-base distance was more active than maximum-C-A-SBA-15 with a maximum acid-base distance in aldol condensation reaction between acetone and various aldehydes. It appears that the distance between acidic site and basic site immobilized on mesoporous solid should be an essential factor for catalysis optimization.

  14. CuO and Ag2O/CuO Catalyzed Oxidation of Aldehydes to the Corresponding Carboxylic Acids by Molecular Oxygen

    Directory of Open Access Journals (Sweden)

    Yaowu Sha

    2008-04-01

    Full Text Available Furfural was oxidized to furoic acid by molecular oxygen under catalysis by 150nm-sized Ag2O/CuO (92% or simply CuO (86.6%. When 30 nm-size catalyst was used,the main product was a furfural Diels-Alder adduct. Detailed reaction conditions andregeneration of catalysts were investigated. Under optimal conditions, a series of aromaticand aliphatic aldehydes were oxidized to the corresponding acids in good yields.

  15. Conversion of hemicellulose sugars catalyzed by formic acid: kinetics of the dehydration of D-xylose, L-arabinose, and D-glucose.

    Science.gov (United States)

    Dussan, Karla; Girisuta, Buana; Lopes, Marystela; Leahy, James J; Hayes, Michael H B

    2015-04-24

    The pre-treatment of lignocellulosic biomass produces a liquid stream of hemicellulose-based sugars, which can be further converted to high-value chemicals. Formosolv pulping and the Milox process use formic acid as the fractionating agent, which can be used as the catalyst for the valorisation of hemicellulose sugars to platform chemicals. The objective of this study was to investigate the reaction kinetics of major components in the hemicelluloses fraction of biomass, that is, D-xylose, L-arabinose and D-glucose. The kinetics experiments for each sugar were performed at temperatures between 130 and 170 °C in various formic acid concentrations (10-64 wt %). The implications of these kinetic models on the selectivity of each sugar to the desired products are discussed. The models were used to predict the reaction kinetics of solutions that resemble the liquid stream obtained from the fractionation process of biomass using formic acid. PMID:25821128

  16. Synthesis of butyl hexanoate catalyzed by solid acid catalyst%新型固体酸催化合成己酸丁酯

    Institute of Scientific and Technical Information of China (English)

    闫鹏; 郭海福; 陈志胜; 王赵志

    2011-01-01

    Butyl hexanoate was synthesized by hexanoic acid and n-butanol,using solid acid Zr( SO4 )2/SiO2 as catalyst. Effects of n(hexanoic acid):n( n-butanol), catalyst dosage and reaction time on the esterification rate were discussed by orthogonal experiment design,which showed that the influence order of esterification rate was: catalyst dosage > reaction time > n ( hexanoic acid ): n ( n- butanol ) .The optimum technical conditions were as follow: n( hexanoic acid):n(n-butanol) = 1:3, mass fraction of Zr(SO4) 2/SiO2 in hexanoic acid 4.0% and reaction time 2.5h,the esterification rate was 99.6%.%以新型固体酸zr(SO4)2/SiO2为催化荆,己酸和正丁醇为原料,催化合成葡萄酒用香料己酸丁酯.通过正交实验设计考察影响反应的因素.结果表明,在酸醇摩尔比、催化剂用量、反应时间三个因素中,其影响次序为催化剂用量>反应时间>酸醇比.适宜的工艺条件为:酸醇物质的量比为1:3,催化剂用量为4%,反应时间为2.5h,酯化率可达99.6%.

  17. The synthesis of mono- and diacetyl-9H-fluorenes. Reactivity and selectivity in the Lewis acid catalyzed Friedel-Crafts acetylation of 9H-fluorene

    DEFF Research Database (Denmark)

    Titinchi, Salam J.J.; Kamounah, Fadhil S.; Abbo, Hanna S.;

    2008-01-01

    Friedel-Crafts acetylation of 9H-fluorene is an effective route for the preparation of mono- and diacetyl-9H-fluorenes. Using acetylchloride as the reagent and aluminum chloride as the Lewis acid catalyst the effect of the solvent polarity, the temperature, the reaction time and the mode of addit......Friedel-Crafts acetylation of 9H-fluorene is an effective route for the preparation of mono- and diacetyl-9H-fluorenes. Using acetylchloride as the reagent and aluminum chloride as the Lewis acid catalyst the effect of the solvent polarity, the temperature, the reaction time and the mode...

  18. Muon catalyzed fusion

    Energy Technology Data Exchange (ETDEWEB)

    Ishida, K. [Advanced Meson Science Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Nagamine, K. [Muon Science Laboratory, IMSS-KEK, 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); Matsuzaki, T. [Advanced Meson Science Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Kawamura, N. [Muon Science Laboratory, IMSS-KEK, 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan)

    2005-12-15

    The latest progress of muon catalyzed fusion study at the RIKEN-RAL muon facility (and partly at TRIUMF) is reported. The topics covered are magnetic field effect, muon transfer to {sup 3}He in solid D/T and ortho-para effect in dd{mu} formation.

  19. Phosphotungstic Acid Catalyzed One-Pot Synthesis of 2-amino-3,5-dicarbonitrile-6-thio-pyridines in Aqueous Media

    International Nuclear Information System (INIS)

    In this study, we report the one-pot synthesis of 2-amino-3,5-dicarbonitrile-6-thio-pyridines with benzaldehyde, malononitrile, and thiophenol by using phosphotungstic acid as an efficient catalyst to aqueous media. This method has the advantages of easy separation, high storage stability, and environmental friendliness. (author)

  20. Nickel-catalyzed cross-coupling of phenols and arylboronic acids through an in situ phenol activation mediated by PyBroP.

    Science.gov (United States)

    Chen, Guo-Jun; Huang, Jie; Gao, Lian-Xun; Han, Fu-She

    2011-03-28

    A new method for the Suzuki-Miyaura cross-coupling of phenols and arylboronic acids through in situ phenol activation mediated by PyBroP is presented. The reaction proceeds efficiently by using cost-effective, markedly stable [NiCl(2)(dppp)] (dppp=1,3-bis(diphenylphosphino)propane) as the catalyst in only 5 mol % loading, as well as in the absence of extra ligands. The method exhibits broad applicability and high efficiency towards a wide range of both phenols and boronic acids, including activated, nonactivated, deactivated, and heteroaromatic coupling partners. In addition, various functional groups, such as ether, amino, cyano, ester, and ketone groups, are compatible with this transformation. Notably, arylboronic acids containing an unprotected NH(2) group and 2-heterocyclic boronic acids, which are generally problematic for coupling under conventional conditions, are also viable substrates, although moderate yields were obtained for sterically hindered substrates. Consequently, the in situ cross-coupling methodology coupled with the use of an inexpensive and stable nickel catalyst provides a rapid and efficient pathway for the assembly of biaryls and heterobiaryls with structural diversity from readily available phenol compounds.

  1. Influence of acid-base properties on the Lebedev ethanol-to-butadiene process catalyzed by SiO2-MgO materials

    NARCIS (Netherlands)

    Angelici, Carlo; Velthoen, Marjolein E. Z.; Weckhuysen, Bert M.; Bruijnincx, Pieter C. A.

    2015-01-01

    The Lebedev ethanol-to-butadiene process entails a complex chain of reactions that require catalysts to possess a subtle balance in the number and strength of acidic and basic sites. SiO2-MgO materials can be excellent Lebedev catalysts if properly prepared, as catalyst performance has been found to

  2. Synthesis of ferulic acid catalyzed by ammonium acetate%乙酸铵催化合成阿魏酸的工艺研究

    Institute of Scientific and Technical Information of China (English)

    梁红冬; 蔡庆荣

    2011-01-01

    以香草醛和丙二酸为原料,乙酸铵为催化剂,合成阿魏酸.考察反应时间、投料物质的量比、催化剂用量和溶剂体积比等因素对收率的影响.结果表明,N,N-二甲基甲酰胺作溶剂,环已烷作带水剂,在V(环己烷)∶以N,N-二甲基甲酰胺)=2∶1、催化剂用量占香草醛质量的6%、n(香草醛)∶n(丙二酸)=1∶1.3和反应时间4h条件下,阿魏酸收率为70.87%.%Ferulic acid was synthesized by using vanillic aldehyde and malonic acid as raw materials, and ammonium acetate as the catalyst. The influence of reaction time, molar ratio of reactants, catalyst dosage and volume ratio of cyclohexane to N ,N-dimethylformamide( DMF) on ferulic acid yield was investigated. The experimental results indicated that ferulic acid yield of 70. 87% was attained under the optimum reaction condition as follows;DMF as the solvent,cyclohexane as the water carrying agent,volume ratio of cyclohexane to DMF =2∶1, catalyst dosage 6% of mass of vanillic aldehyde, molar ratio of vanillic aldehyde to malonic acid 1∶1∶3, and reaction time 4 h.

  3. Synthesis of 1-tert-butoxy-4-methylbenzene with p-cresol and isobutene catalyzed by Lewis acid%Lewis酸催化对甲酚与异丁烯合成对叔丁氧基甲苯

    Institute of Scientific and Technical Information of China (English)

    林富荣; 颉林; 周永生

    2012-01-01

    1-tert-Butoxy-4-methylbenzene was prepared through O-alkylation of p-cresol and isobutene catalyzed by Lewis acid. The effects of reaction conditions such as type of catalyst, the amount of catalyst, temperature, and mole ratios between materials on O-alkylation were optimized. The yield of product can be 76% with content of 99. 6% when weight ratio of p-cresol/crystal ferric chloride is 11. 8: 1,molar ratio of isobutene/p-cresol 1.6- 1, reaction temperaturef30 ℃ , reaction time 9 h, condensed isobutene dropped with resistant and constant pressure dropping funnel. The reaction mechanism of O-alkylation catalyzed by Lewis acid was discussed. The method is characterized by excellent atom economy and high selectivity of O-alkylation.%以Lewis酸为催化剂,对甲苯酚与异丁烯经O-烷基化反应合成对叔丁氧基甲苯.考察了催化剂种类、催化剂用量、反应温度、物料比等因素对反应的影响.实验表明适宜的工艺条件是对甲酚与结晶氯化铁的质量比为11.8∶1,异丁烯与对甲酚的物质的量为1.6∶1,异丁烯通过耐压恒压滴液漏斗滴加,反应温度为30℃,反应时间为9h,收率达76%,纯度为99.6%.探讨了Lewis酸催化O-烷基化反应的机理.该方法具有原子经济性好,0-烷基化反应选择性高特点.

  4. 固体碱催化合成中碳链脂肪酸聚甘油酯%Synthesis of polyglycerol medium chain fatty acid ester catalyzed by solid base catalyst

    Institute of Scientific and Technical Information of China (English)

    曾哲灵; 邹强; 聂蓉蓉; 龙俊敏; 张驰

    2012-01-01

    以聚甘油、樟树籽仁油脂肪酸为原料,固体碱KOH/Al2O3为催化剂,催化酯化合成中碳链脂肪酸聚甘油酯.采用单因素试验研究反应温度、反应时间、聚甘油与中碳链脂肪酸质量比、催化剂用量对酯化率的影响,通过正交试验优化中碳链脂肪酸聚甘油酯的合成工艺.最优合成工艺条件为反应温度220℃、反应时间2.5h、聚甘油与中碳链脂肪酸质量比2∶1、催化剂用量4.5%,该条件下酯化率为87.5%,所得中碳链脂肪酸聚甘油酯的酸值(KOH)、皂化值(KOH)、碘值(Ⅰ)、熔点分别为1.86 mg/g、148.4 mg/g、2.9 g/100 g、47.3℃.%The solid base KOH/A12O3 was used as catalyst to catalyze esterification of polyglycerol and fatty acids of camphor tree seed kernel oil to synthesize polyglycerol medium chain fatty acid ester. The effects of reaction temperature, reaction time, mass ratio of polyglycerol to medium chain fatty acid and dosage of catalyst on esterification rate were studied by single factor tests, and the synthesis technology of polyglycerol medium chain fatty acid ester was optimized by an orthogonal test. The optimal synthesis conditions were as follows: reaction temperature 220 °C , reaction time 2. 5 h, mass ratio of polyglycerol to medium chain fatty acid 2:1, dosage of catalyst 4. 5%. Under the optimal conditions, the esterification yield reached 87. 5% , and the acid value, saponification value, iodine value, and melting point of the product were 1.86 mgKOH/g,148.4 mgKOH/g, 2.9 gl/100 g and 47. 3 °C , respectively.

  5. Computational Study on the Acid Catalyzed Reactions of Fluorine-Containing 2,4-Dialkoxy-3,4-dihydro-2H-pyrans with Aromatic Compounds

    Directory of Open Access Journals (Sweden)

    Norio Ota

    2012-02-01

    Full Text Available The reaction of 2,4-diethoxy-6-trifluoromethyl-3,4-dihydro-2H-pyran (1 with aromatic compounds in refluxing acetonitrile in the presence of p-toluenesulfonic acid gave the mixture of 4-aryl-2-trifluoromethyl-4H-pyrans (3 and 6-aryl-1,1,1-trifluorohexa-3,5-dien-2-ones (4. In contrast, the same reaction carried out in trifluoroacetic acid at ambient temperature afforded 4-aryl-2-ethoxy-6-trifluoromethyl-3,4-dihydro-2H-pyrans (2 selectively. These two types of reactions giving quite different products under each condition were studied on the basis of DFT calculations. Moreover, the proposed mechanism for the reaction of 5-trifluoroacetyl-6-trifluoromethyl-3,4-dihydro-2H-pyran (5 with aromatic compounds affording butadiene derivatives (6 exclusively was also discussed based on the calculations and comparison with the reactivity of pyrylium intermediate (7.

  6. COPOLYMERIZATION OF CARBON DIOXIDE AND CYCLOHEXENE OXIDE CATALYZED BY ALUMINUM PORPHYRIN-QUATERNARY AMMONIUM SALT IN THE PRESENCE OF BULKY LEWIS ACID

    Institute of Scientific and Technical Information of China (English)

    Yu-sheng Qin; Xian-hong Wang; Xiao-jiang Zhao; Fo-song Wang

    2008-01-01

    Chloro(5,10,15,20-tetraphenyl-porphyrinato)-aluminum/tetraethylammonium bromide (Et4NBr) in combinationwith bulky Lewis acid was used for the copolymerization of CO2 and cyclohexene oxide (CHO). Bulky Lewis acid havingsubstituents at the ortho positions of the phenolate ligands, like methylaluminum bis(2,6-di-tert-butyl-4-methylphenolate),significantly shortened the induction period and raised the catalytic activity, the corresponding turnover frequency reached44.9 h-1 in 9 h, which was 23.8% higher than that from (TPP)AICI/EtaNBr binary catalyst. The resulting polycarbonate hascarbonate linkage over 93% with number average molecular weight of (4.5-6.5)×103 and polydispersity index below 1.10.

  7. Research progress of heteropoly acid catalyzed oxidative desulfurization%杂多酸催化剂催化氧化脱硫研究进展

    Institute of Scientific and Technical Information of China (English)

    张海燕; 代跃利; 蔡蕾

    2013-01-01

    Research progress of applications of heteropoly acid catalyst in the oxidative desulfurization of fuel oil was introduced. Heteropoly acid catalysts, including those containing transition metal, alkali metal, rare earth metal, quaternary ammonium salt, ionic liquid and catalysts supported on carriers, such as carbon materials, titanium dioxide, silica, polymer materials were described and the characteristics and catalytic effects of the catalysts were summerized.Comprehensive utilization of heteropoly acid catalysts' properties and the development of novel high performance heteropoly acid catalysts with high activity, less oxygen consumption and strong reusability were important research topics for deep desulfurization through catalytic oxidation.%介绍了杂多酸催化剂在燃料油氧化脱硫中的应用研究进展.详细叙述了过渡金属、碱金属和稀土金属杂多酸催化剂、杂多酸季铵盐催化剂、杂多酸离子液体催化剂和以碳材料、二氧化钛、二氧化硅、高分子材料等为载体的负载型杂多酸催化剂,阐述了各种杂多酸催化剂的特点及脱硫效果,指出综合应用杂多酸催化剂特性开发活性高、耗氧少、重复使用性强的优良新型杂多酸催化剂是催化氧化深度脱硫的重要研究方向.

  8. VO(acac)2 catalyzed condensation of o-phenylenediamine with aromatic carboxylic acids/aldehydes under microwave radiation affording benzimidazoles

    Institute of Scientific and Technical Information of China (English)

    Madhudeepa Dey; Krishnajyoti Deb; Siddhartha Sankar Dhar

    2011-01-01

    Vanadyl acetylacetonate, VO(acac)2, has been found to be very effective catalyst for synthesis of a variety of benzimidazoles under solvent-free condition. The methodology involves the exposure of a mixture of o-phenylenediamine and a selected aromatic carboxylic acid/aldehyde to microwave radiation without the use of any solvent or supporting agents. The benzimidazoles were obtained in quick time with high yields.

  9. Thermally Stable Forms of Pure Polyaniline Catalyzed by an Acid-Exchanged Montmorillonite Clay Called Maghnite- H + as an Effective Catalyst

    OpenAIRE

    Rahmouni Abdelkader; Harrane Amine; Belbachir Mohammed

    2012-01-01

    Polyaniline salt form (PANI-ES) was synthesized by oxidative polymerization of aniline using potassium persulfate as an oxidant and an acid-exchanged montmorillonite clay called Maghnite-H+ as an effective catalyst. The clay, which was used as a catalyst, was supplied by a local company known as ENOF Maghnia (Western Algeria). The chemical stability of PANI has been investigated by thermogravimetry and differential scanning calorimetry, that a good thermal stability of PANI could be improved ...

  10. Sulphamic Acid (H2NSO3H)-Catalyzed Multicomponent Reaction of β-Naphthol: An Expeditious Synthesis of Amidoalkyl Naphthols

    Institute of Scientific and Technical Information of China (English)

    NAGAWADE Rahul R.; SHINDE Devanand B.

    2007-01-01

    Sulphamic acid (H2NSO3H) was found to be an efficient catalyst for the multicomponent condensation reaction of β-naphthol, aromatic aldehydes and urea or amides to afford the corresponding a-amidoalkyl-β-naphthols in good yields. The remarkable features of this new procedure are high conversions, short reaction time, clean reaction profiles and simple experimental and work-up procedures.

  11. Structured lipids via lipase-catalyzed incorporation of eicosapentaenoic acid into borage (Borago officinalis L.) and evening primrose (Oenothera biennis L.) oils.

    Science.gov (United States)

    Senanayake, S P J Namal; Shahidi, Fereidoon

    2002-01-30

    Enzymatic acidolysis of borage oil (BO) or evening primrose oil (EPO) with eicosapentaenoic acid (20:5n-3; EPA) was studied. Of the six lipases that were tested in the initial screening, nonspecific lipase PS-30 from Pseudomonas sp. resulted in the highest incorporation of EPA into both oils. This enzyme was further studied for the influence of enzyme load, temperature, time, type of organic solvent, and mole ratio of substrates. The products from the acidolysis reaction were analyzed by gas chromatography (GC). The highest incorporation of EPA in both oils occurred at 45-55 degrees C and at 150-250 enzyme activity units. One unit of lipase activity was defined as nanomoles of fatty acids (oleic acid equivalents) produced per minute per gram of enzyme. Time course studies indicated that EPA incorporation was increased up to 26.8 and 25.2% (after 24 h) in BO and EPO, respectively. Among the solvents examined, n-hexane served best for the acidolysis of EPA with both oils. The effect of the mole ratio of oil to EPA was studied from 1:1 to 1:3. As the mole ratio of EPA increased, the incorporation increased from 25.2-26.8 to 37.4-39.9% (after 24 h). The highest EPA incorporations of 39.9 and 37.4% in BO and EPO, respectively, occurred at the stoichiometric mole ratio of 1:3 for oil to EPA. PMID:11804516

  12. High-yield preparation of wax esters via lipase-catalyzed esterification using fatty acids and alcohols from crambe and camelina oils.

    Science.gov (United States)

    Steinke, G; Weitkamp, P; Klein, E; Mukherjee, K D

    2001-02-01

    Fatty acids obtained from seed oils of crambe (Crambe abyssinica) and camelina (Camelina sativa) via alkaline saponification or steam splitting were esterified using lipases as biocatalysts with oleyl alcohol and the alcohols derived from crambe and camelina oils via hydrogenolysis of their methyl esters. Long-chain wax esters were thus obtained in high yields when Novozym 435 (immobilized lipase B from Candida antarctica) and papaya (Carica papaya) latex lipase were used as biocatalysts and vacuum was applied to remove the water formed. The highest conversions to wax esters were obtained with Novozym 435 (> or =95%) after 4-6 h of reaction, whereas with papaya latex lipase such a high degree of conversion was attained after 24 h. Products obtained from stoichiometric amounts of substrates were almost exclusively (>95%) composed of wax esters having compositions approaching that of jojoba (Simmondsia chinensis) oil, especially when crambe fatty acids in combination with camelina alcohols or camelina fatty acids in combination with crambe alcohols were used as substrates.

  13. Effective Liquid-phase Nitration of Benzene Catalyzed by a Stable Solid Acid Catalyst: Silica Supported Cs2.5H0.5PMo12O40

    International Nuclear Information System (INIS)

    Silica supported Cs2.5H0.5PMo12O40 catalyst was prepared through sol-gel method with ethyl silicate-40 as silicon resource and characterized by X-ray diffraction, infrared spectroscopy, scanning electron microscopy, nitrogen adsorption-desorption and potentiometric titration methods. The Cs2.5H0.5PMo12O40 particles with Keggin-type structure well dispersed on the surface of silica, and the catalyst exhibited high surface area and acidity. The catalytic performance of the catalysts for benzene liquid-phase nitration was examined with 65% nitric acid as nitrating agent, and the effects of various parameters were tested, which including temperature, time and amount of catalyst, reactants ratio, especially the recycle of catalyst was emphasized. Benzene was effectively nitrated to mononitro-benzene with high conversion (95%) in optimized conditions. Most importantly, the supported catalyst was proved has excellent stability in the nitration progress, and there were no any other organic solvent and sulfuric acid were used in the reaction system, so the liquid-phase nitration of benzene that we developed was an eco-friendly and attractive alternative for the commercial technology

  14. 固体酸催化合成二氯乙酸乙酯%Synthesis of ethyl dichloroacetate catalyzed by solid acid

    Institute of Scientific and Technical Information of China (English)

    刘俊峰; 朱莹莹; 冯桂英; 王胜华; 何超

    2014-01-01

    One kind of method was introduled for the synthesis of dichloro -acetic acid ethyl ester. Dichloroacetic acid was used as staring material,the catalysis of the catalyst on dehydration of dichloroacetic acid and ethanol to produce the ether was discussed.At the same times,The effects of different water-carrying agent such as benzene,toluene,cyclohexane and their dosage on the reaction were investigated.Taking FeCl3·6H2O as catalyst,cyclohexane as dehydrant,ethanol as reaction solvent and raw materials,dichloro-acetic acid ethyl ester was product.The best reaction condition was as follows:12.9 g dichloroacetic acid,20 ml dehydrated alcohol,15 ml cyclohexane,0.5 g ferric trichloride,reaction temperature was reflux ,reaction time was 40 min. After the reaction was finished ,distilling and collecting 153 ~156 ℃ distillation to get dichloro -acetic acid ethyl ester of a colourless liquid.The yield was 85 .4% and the purity is greater than or equa 98%.After the solvent was distilled,the catalyst was reused total 240 mins.The dichloro-acetic acid ethyl ester productivities of four tests are as follows respectively:85.4%,77.1%,83.4%,78.3%.%介绍一种二氯乙酸乙酯的合成方法.以二氯乙酸为起始原料,研究了催化剂对二氯乙酸与乙醇脱水醚化反应的催化性能,同时讨论了不同带水剂苯、甲苯、环己烷及其用量对反应的影响,得到以FeCl3·6H2 O为催化剂,环己烷为带水剂,乙醇既作反应原料又为溶剂,制备二氯乙酸乙酯,最佳反应条件:二氯乙酸12.9 g,无水乙醇20 mL,环己烷15 mL,催化剂用量0.5 g,反应温度:回流,反应时间40 min.反应产物蒸馏收集153~156℃的馏分得到无色液体二氯乙酸乙酯,纯度大于98%,蒸干溶剂后,进行催化剂重复使用试验,其结果为:重复反应4次,累计反应时间为240 min,二氯乙酸乙酯产率分别为85.4%,77.1%,83.4%,78.3%.

  15. Antibody-Catalyzed Degradation of Cocaine

    Science.gov (United States)

    Landry, Donald W.; Zhao, Kang; Yang, Ginger X.-Q.; Glickman, Michael; Georgiadis, Taxiarchis M.

    1993-03-01

    Immunization with a phosphonate monoester transition-state analog of cocaine provided monoclonal antibodies capable of catalyzing the hydrolysis of the cocaine benzoyl ester group. An assay for the degradation of radiolabeled cocaine identified active enzymes. Benzoyl esterolysis yields ecgonine methyl ester and benzoic acid, fragments devoid of cocaine's stimulant activity. Passive immunization with such an artificial enzyme could provide a treatment for dependence by blunting reinforcement.

  16. Tritium catalyzed deuterium tokamaks

    International Nuclear Information System (INIS)

    A preliminary assessment of the promise of the Tritium Catalyzed Deuterium (TCD) tokamak power reactors relative to that of deuterium-tritium (D-T) and catalyzed deuterium (Cat-D) tokamaks is undertaken. The TCD mode of operation is arrived at by converting the 3He from the D(D,n)3He reaction into tritium, by neutron capture in the blanket; the tritium thus produced is fed into the plasma. There are three main parts to the assessment: blanket study, reactor design and economic analysis and an assessment of the prospects for improvements in the performance of TCD reactors (and in the promise of the TCD mode of operation, in general)

  17. Asymmetric Ring-Opening of Cyclopropyl Ketones with Thiol, Alcohol, and Carboxylic Acid Nucleophiles Catalyzed by a Chiral N,N'-Dioxide-Scandium(III) Complex.

    Science.gov (United States)

    Xia, Yong; Lin, Lili; Chang, Fenzhen; Fu, Xuan; Liu, Xiaohua; Feng, Xiaoming

    2015-11-01

    A highly efficient asymmetric ring-opening reaction of cyclopropyl ketones with a broad range of thiols, alcohols and carboxylic acids has been first realized by using a chiral N,N'-dioxide-scandium(III) complex as catalyst. The corresponding sulfides, ethers, and esters were obtained in up to 99% yield and 95% ee. This is also the first example of one catalytic system working for the ring-opening reaction of donor-acceptor cyclopropanes with three different nucleophiles, let alone in an asymmetric version. PMID:26398505

  18. Influence of acid-base properties on the Lebedev ethanol-to-butadiene process catalyzed by SiO2-MgO materials

    OpenAIRE

    Angelici, Carlo; Velthoen, Marjolein E. Z.; Weckhuysen, Bert M.; Bruijnincx, Pieter C. A.

    2015-01-01

    The Lebedev ethanol-to-butadiene process entails a complex chain of reactions that require catalysts to possess a subtle balance in the number and strength of acidic and basic sites. SiO2-MgO materials can be excellent Lebedev catalysts if properly prepared, as catalyst performance has been found to depend significantly on the synthesis method. To assess the specific requirements for butadiene production in terms of active sites and to link their presence to the specific preparation method ap...

  19. Direct and remarkably efficient conversion of methane into acetic acid catalyzed by amavadine and related vanadium complexes. A synthetic and a theoretical DFT mechanistic study.

    Science.gov (United States)

    Kirillova, Marina V; Kuznetsov, Maxim L; Reis, Patrícia M; da Silva, José A L; da Silva, João J R Fraústo; Pombeiro, Armando J L

    2007-08-29

    Vanadium(IV or V) complexes with N,O- or O,O-ligands, i.e., [VO{N(CH2CH2O)3}], Ca[V(HIDPA)2] (synthetic amavadine), Ca[V(HIDA)2], or [Bu4N]2[V(HIDA)2] [HIDPA, HIDA = basic form of 2,2'-(hydroxyimino)dipropionic or -diacetic acid, respectively], [VO(CF3SO3)2], Ba[VO(nta)(H2O)]2 (nta = nitrilotriacetate), [VO(ada)(H2O)] (ada = N-2-acetamidoiminodiacetate), [VO(Hheida)(H2O)] (Hheida = 2-hydroxyethyliminodiacetate), [VO(bicine)] [bicine = basic form of N,N-bis(2-hydroxyethyl)glycine], and [VO(dipic)(OCH2CH3)] (dipic = pyridine-2,6-dicarboxylate), are catalyst precursors for the efficient single-pot conversion of methane into acetic acid, in trifluoroacetic acid (TFA) under moderate conditions, using peroxodisulfate as oxidant. Effects on the yields and TONs of various factors are reported. TFA acts as a carbonylating agent and CO is an inhibitor for some systems, although for others there is an optimum CO pressure. The most effective catalysts (as amavadine) bear triethanolaminate or (hydroxyimino)dicarboxylates and lead, in a single batch, to CH3COOH yields > 50% (based on CH4) or remarkably high TONs up to 5.6 x 103. The catalyst can remain active upon multiple recycling of its solution. Carboxylation proceeds via free radical mechanisms (CH3* can be trapped by CBrCl3), and theoretical calculations disclose a particularly favorable process involving the sequential formation of CH3*, CH3CO*, and CH3COO* which, upon H-abstraction (from TFA or CH4), yields acetic acid. The CH3COO* radical is formed by oxygenation of CH3CO* by a peroxo-V complex via a V{eta1-OOC(O)CH3} intermediate. Less favorable processes involve the oxidation of CH3CO* by the protonated (hydroperoxo) form of that peroxo-V complex or by peroxodisulfate. The calculations also indicate that (i) peroxodisulfate behaves as a source of sulfate radicals which are methane H-abstractors, as a peroxidative and oxidizing agent for vanadium, and as an oxidizing and coupling agent for CH3CO* and that (ii) TFA is

  20. 固体酸催化合成乳酸正丁酯%Synthesis of n-Butyl Lactate Catalyzed by Solid Acid

    Institute of Scientific and Technical Information of China (English)

    苏兆祥; 邓旭忠; 杨辉荣; 谢光炎

    2000-01-01

    In the presence of roasted ferric sulfate as catalyst,lactic acid can react with n-butyl alcohol to form n-butyl lactate. The optimum conditions are follows:molar ratio of lactic acid to n-butyl alcohol = 1:4.5,reaction temperature time = 150min, weight of catalyst=2g. The yield under the optimum conditions was up to 87.4%.The catalyst has many advantages,such as being able to manufacture very easy,use repeatedly and less pollution to the environment.%以焙烧的Fe2(SO4)3为催化剂,实现了乳酸与正丁酸与正丁醇反应合成乳酸正丁酯.最佳合成条件为:以0.085mol乳酸为准,乳酸与丁醇的摩尔比是1:4,催化剂用量为2g,反应时间为150min,产率达87.4%.该催化剂具有制备易,可循环使用,不污染环境等优点.

  1. 对甲苯磺酸催化查尔酮的合成%Synthtsis of Chalcone Catalyzed by P-toluenesulfonic Acid

    Institute of Scientific and Technical Information of China (English)

    谭昌会; 郑荣选; 罗淑云; 林俏焰

    2012-01-01

    研究了查耳酮的制备方法和缩合反应的影响因素选择最佳的反应条件,实验的结果表明,合成查尔酮的缩合反应的较佳条件是:n(苯乙酮)加(间硝基苯甲醛)=1∶1,反应温度是70℃,反应的时间3h,对甲笨磺酸为3 g,乙酸用量为20 mL,在此条件下查尔酮的收率达71.6%.%Synthesis methods of chalcone were studied, affecting factors of the condensation reaction were discussed so as to select the best reaction conditions. The experimental results show that the better reaction conditions of the synthesis are as follows: n (m-nitrobenzaldehyde) / n (preparation) = 1 : 1, the reaction temperature is 70 ℃, the reaction time is 3 h, p-toluene sulfonic acid dosage and acetic acid dosage are 3 g and 20 mL , respectively. Under above conditions, the chalcone yield can reach 71.6%.

  2. Production of oleic acid ethyl ester catalyzed by crude rice bran (Oryza sativa lipase in a modified fed-batch system: problem and its solution

    Directory of Open Access Journals (Sweden)

    Indro Prastowo

    2015-01-01

    Full Text Available A fed-batch system was modified for the enzymatic production of Oleic Acid Ethyl Ester (OAEE using rice bran (Oryza sativa lipase by retaining the substrate molar ratio (ethanol/oleic acid at 2.05: 1 during the reaction. It resulted in an increase in the ester conversion up to 76.8% in the first 6 h of the reaction, and then followed by a decrease from 76.8% to 22.9% in 6 h later. Meanwhile, the production of water in the reaction system also showed a similar trend to the trend of ester production. The water was hypothesized to lead lipase to reverse the reaction which resulted in a decrease in both (water and esters in the last 6 h of the reaction. In order to overcome the problem, zeolite powders (25 and 50 mg/ml were added into the reaction system at 5 h of the reaction. As the result, final ester conversions increased drastically up to 90 - 95.7% (1.17 – 1.24 times. The addition also proved a hypothesis that the water was involved in reducing the ester conversion in the last 6 h of the reaction. Thus, the combination was effective to produce the high final ester conversion.

  3. The mechanism of Fe (Ⅲ)-catalyzed ozonation of phenol

    Institute of Scientific and Technical Information of China (English)

    竹湘锋; 徐新华

    2004-01-01

    Fe (Ⅲ)-catalyzed ozonation yielded better degradation rate and extent of COD (Chemical Oxygen Demand) or oxalic acid as compared with oxidation by ozone alone. Two parameters with strong effects on the efficiency of ozonation are pH of the solution and the catalyst (Fe3+) dosage. The existence of a critical pH value determining the catalysis of Fe (Ⅲ) in acid conditions was observed in phenol and oxalic acid systems. The best efficiency of catalysis was obtained at a moderate concentration of the catalyst. A reasonable mechanism of Fe (Ⅲ)-catalyzed ozonation of phenol was obtained based on the results and literature.

  4. Mechanism of the Enantioselective Intramolecular [2 + 2] Photocycloaddition Reaction of Coumarin Catalyzed by a Chiral Lewis Acid: Comparison with Enone Substrates.

    Science.gov (United States)

    Wang, Hongjuan; Fang, Wei-Hai; Chen, Xuebo

    2016-08-19

    The asymmetric catalysis of the intramolecular enone [2 + 2] photocycloaddition reaction relies on a complicated regulation mechanism to control its reactivity and selectivity as well as quantum yield. The multiconfiguration perturbation theory associated with energy-consistent relativistic pseudopotentials offers a mechanistic comparison between representative coumarin and enone substrates. A pair of bright ππ* states govern the unselective background reaction of the free coumarin through the direct cycloaddition in the singlet hypersurface and the elimination of the reaction channel in the triplet manifold due to the existence of anti El Sayed type singlet-triplet crossing. The opening of a reaction channel in the triplet state is repeatedly verified to depend on the presence of relativistic effects, i.e., spin-orbit coupling due to heavy atoms in the chiral Lewis acid catalyst. PMID:27322795

  5. Thermally Stable Forms of Pure Polyaniline Catalyzed by an Acid-Exchanged Montmorillonite Clay Called Maghnite-H+ as an Effective Catalyst

    Directory of Open Access Journals (Sweden)

    Rahmouni Abdelkader

    2012-01-01

    Full Text Available Polyaniline salt form (PANI-ES was synthesized by oxidative polymerization of aniline using potassium persulfate as an oxidant and an acid-exchanged montmorillonite clay called Maghnite-H+ as an effective catalyst. The clay, which was used as a catalyst, was supplied by a local company known as ENOF Maghnia (Western Algeria. The chemical stability of PANI has been investigated by thermogravimetry and differential scanning calorimetry, that a good thermal stability of PANI could be improved by combining PANI with montmorillonite. TGA results illustrated that there were two major stages for weight loss of the ES-form PANI powder sample. The different forms of PANI were characterized by infrared spectroscopy, thermal analysis, and H-NMR spectroscopy and conductivity measurements.

  6. Palladium(II)-catalyzed oxidation of L-tryptophan by hexacyanoferrate(III) in perchloric acid medium: a kinetic and mechanistic approach

    Indian Academy of Sciences (India)

    Ahmed Fawzy

    2016-02-01

    The catalytic effect of palladium(II) on the oxidation of L-tryptophan by potassium hexacyanoferrate( III) has been investigated spectrophotometrically in aqueous perchloric acid medium. A first order dependence in [hexacyanoferrate(III)] and fractional-first order dependences in both [L-tryptophan] and [palladium(II)] were obtained. The reaction exhibits fractional-second order kinetics with respect to [H+]. Reaction rate increased with increase in ionic strength and dielectric constant of the medium. The effect of temperature on the reaction rate has also been studied and activation parameters have been evaluated and discussed. Initial addition of the reaction product, hexacyanoferrate(II), does not affect the rate significantly. A plausible mechanistic scheme explaining all the observed kinetic results has been proposed. The final oxidation products are identified as indole-3-acetaldehyde, ammonium ion and carbon dioxide. The rate law associated with the reaction mechanism is derived.

  7. A propionate CoA-transferase of Ralstonia eutropha H16 with broad substrate specificity catalyzing the CoA thioester formation of various carboxylic acids.

    Science.gov (United States)

    Lindenkamp, Nicole; Schürmann, Marc; Steinbüchel, Alexander

    2013-09-01

    In this study, we have investigated a propionate CoA-transferase (Pct) homologue encoded in the genome of Ralstonia eutropha H16. The corresponding gene has been cloned into the vector pET-19b to yield a histidine-tagged enzyme which was expressed in Escherichia coli BL21 (DE3). After purification, high-performance liquid chromatography/mass spectrometry (HPLC/MS) analyses revealed that the enzyme exhibits a broad substrate specificity for carboxylic acids. The formation of the corresponding CoA-thioesters of acetate using propionyl-CoA as CoA donor, and of propionate, butyrate, 3-hydroxybutyrate, 3-hydroxypropionate, crotonate, acrylate, lactate, succinate and 4-hydroxybutyrate using acetyl-CoA as CoA donor could be shown. According to the substrate specificity, the enzyme can be allocated in the family I of CoA-transferases. The apparent molecular masses as determined by gel filtration and detected by SDS polyacrylamide gel electrophoresis were 228 and 64 kDa, respectively, and point to a quaternary structure of the native enzyme (α4). The enzyme exhibited similarities in sequence and structure to the well investigated Pct of Clostridium propionicum. It does not contain the typical conserved (S)ENG motif, but the derived motif sequence EXG with glutamate 342 to be, most likely, the catalytic residue. Due to the homo-oligomeric structure and the sequence differences with the subclasses IA-C of family I CoA-transferases, a fourth subclass of family I is proposed, comprising - amongst others - the Pcts of R. eutropha H16 and C. propionicum. A markerless precise-deletion mutant R. eutropha H16∆pct was generated. The growth and accumulation behaviour of this mutant on gluconate, gluconate plus 3,3'-dithiodipropionic acid (DTDP), acetate and propionate was investigated but resulted in no observable phenotype. Both, the wild type and the mutant showed the same growth and storage behaviour with these carbon sources. It is probable that R. eutropha H16 is upregulating

  8. Rhodotorula glutinis Phenylalanine/Tyrosine Ammonia Lyase Enzyme Catalyzed Synthesis of the Methyl Ester of para-Hydroxycinnamic Acid and its Potential Antibacterial Activity

    Science.gov (United States)

    MacDonald, Marybeth C.; Arivalagan, Pugazhendhi; Barre, Douglas E.; MacInnis, Judith A.; D’Cunha, Godwin B.

    2016-01-01

    Biotransformation of L-tyrosine methyl ester (L-TM) to the methyl ester of para- hydroxycinnamic acid (p-HCAM) using Rhodotorula glutinis yeast phenylalanine/tyrosine ammonia lyase (PTAL; EC 4.3.1.26) enzyme was successfully demonstrated for the first time; progress of the reaction was followed by spectrophotometric determination at 315 nm. The following conditions were optimized for maximal formation of p-HCAM: pH (8.5), temperature (37°C), speed of agitation (50 rpm), enzyme concentration (0.080 μM), and substrate concentration (0.50 mM). Under these conditions, the yield of the reaction was ∼15% in 1 h incubation period and ∼63% after an overnight (∼18 h) incubation period. The product (p-HCAM) of the reaction of PTAL with L-TM was confirmed using Nuclear Magnetic Resonance spectroscopy (NMR). Fourier Transform Infra-Red spectroscopy (FTIR) was carried out to rule out potential hydrolysis of p-HCAM during overnight incubation. Potential antibacterial activity of p-HCAM was tested against several strains of Gram-positive and Gram-negative bacteria. This study describes a synthetically useful transformation, and could have future clinical and industrial applications. PMID:27014206

  9. Nitric acid activation of graphite granules to increase the performance of the non-catalyzed oxygen reduction reaction (ORR) for MFC applications

    Energy Technology Data Exchange (ETDEWEB)

    Erable, Benjamin [School of Chemical Engineering and Advanced Materials, Newcastle University, Newcastle upon Tyne - NE1 7RU (United Kingdom); Laboratoire de Genie Chimique, CNRS-Universite de Toulouse, 5 rue Paulin Talabot, BP1301, 31106 Toulouse (France); Duteanu, Narcis [School of Chemical Engineering and Advanced Materials, Newcastle University, Newcastle upon Tyne - NE1 7RU (United Kingdom); Faculty of Industrial Chemistry and Environmental Engineering, University ' ' POLITEHNICA' ' Timisoara, 300006 Timisoara (Romania); Kumar, S.M. Senthil; Scott, Keith [School of Chemical Engineering and Advanced Materials, Newcastle University, Newcastle upon Tyne - NE1 7RU (United Kingdom); Feng, Yujie [State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, No. 202, Haihe Road, Harbin 150090 (China); Ghangrekar, Makarand M. [School of Chemical Engineering and Advanced Materials, Newcastle University, Newcastle upon Tyne - NE1 7RU (United Kingdom); Department of Civil Engineering, Indian Institute of Technology, Kharagpur - 721302 (India)

    2009-07-15

    Nitric acid and thermal activation of graphite granules were explored to increase the electrocatalytic performance of dissolved oxygen reduction at neutral pH for microbial fuel cell (MFC) applications. Electrochemical experiments showed an improvement of +400 mV in open circuit potential for graphite granules when they were activated. The improvement of ORR performance observed with activated granules was correlated to the increase of Brunauer-Emmett-Teller (BET) surface of the activated material and the emergence of nitrogen superficial groups revealed by X-ray photoelectron spectroscopy (XPS) analysis on its surface. The use of activated graphite granules in the cathodic compartment of a dual-chamber MFC led to a high open circuit voltage of 1050 mV, which is among one of the highest reported so far. The stable performance of this cathode material (current density of 96 A m{sup -3} at +200 mV/Ag-AgCl) over a period of 10 days demonstrated its applicability as a cathode material without any costly noble metal. (author)

  10. Sonolytic and Silent Polymerization of Methacrlyic Acid Butyl Ester Catalyzed by a New Onium Salt with bis-Active Sites in a Biphasic System — A Comparative Investigation

    Directory of Open Access Journals (Sweden)

    Perumberkandgai A. Vivekanand

    2013-02-01

    Full Text Available Currently, ingenious new analytical and process experimental techniques which are environmentally benign techniques, viz., ultrasound irradiation, have become immensely popular in promoting various reactions. In this work, a novel soluble multi-site phase transfer catalyst (PTC viz., 1,4-bis-(propylmethyleneammounium chloridebenzene (BPMACB was synthesized and its catalytic efficiency was assessed by observing the kinetics of sonolytic polymerization of methacrylic acid butyl ester (MABE using potassium persulphate (PPS as an initiator. The ultrasound–multi-site phase transfer catalysis (US-MPTC-assisted polymerization reaction was compared with the silent (non-ultrasonic polymerization reaction. The effects of the catalyst and various reaction parameters on the catalytic performance were in detail investigated by following the kinetics of polymerization of MABE in an ethyl acetate-water biphasic system. From the detailed kinetic investigation we propose a plausible mechanism. Further the kinetic results demonstrate clearly that ultrasound-assisted phase-transfer catalysis significantly increased the reaction rate when compared to silent reactions. Notably, this environmentally benign and cost-effective process has great potential to be applied in various polymer industries.

  11. Syntheses and Crystal Structures of Chiral BINOL Derivatives and Their Applications in Enantioselective Lewis Acid Catalyzed Addition of Diethylzinc to Aldehydes

    Institute of Scientific and Technical Information of China (English)

    LIU Guo-Hua; YU Han; Yang Liang-Zhun; YAO Mei; FANG Hai-Bin; XUE Yun-Ning

    2007-01-01

    Two novel chiral BINOL derivatives with bis(benzylamine) groups at the 3,3' positions have been synthesized through the condensation reaction between 2,2'-bis(methoxy- methyleneoxy)-1,1'-binaphthyl-3,3'-dicarboxylic acid and benzylamine or N-phenyl benzylamine in the presence of triethylamine. Suitable single crystal of (R)-N,N'-dibenzyl-2,2'-dihydroxy-1,1'-binaphthly-3,3'-diformamide (R)-3 for X-ray diffraction was obtained by recrystallization at room temperature from the mixture solvents. Crystallographic data of (R)-3: C40H36N2O6, Mr=640.71, monoclinic, space group P21, a=6.746(3), b=21.883(9), c=11.723(5) (A), β=104.605(7)°, Z=2, V=1674.7(12) (A)3, Dc=1.271 g/cm3, F(000)=676, R=0.0729, Wr=0.1687 and μ(MoKα)=0.086 mm-1. Two chiral BINOL ligands were found to be effective in the enantioselective addition of diethylzinc to aldehydes and much different enantioselectivity was observed both in the presence and absence of Ti(OiPr)4. In the former case, (R)-3 showed moderate enantioselectivity, which was lower than that of (R)-BINOL's; and in the latter case, (R)-4 gave the highest enantioselectivity up to 93.3% ee.*

  12. Rhodotorulaglutinis phenylalanine/tyrosine ammonia lyase enzyme catalyzed synthesis of the methyl ester of para-hydroxycinnamic acid and its potential antibacterial activity

    Directory of Open Access Journals (Sweden)

    Marybeth C MacDonald

    2016-03-01

    Full Text Available Biotransformation of L-tyrosine methyl ester (L-TM to the methyl ester of para- hydroxycinnamic acid (p-HCAM using Rhodotorula glutinis yeast phenylalanine/tyrosine ammonia lyase (PTAL; EC 4.3.1.26 enzyme was successfully demonstrated for the first time; progress of the reaction was followed by spectrophotometric determination at 315 nm. The following conditions were optimized for maximal formation of p-HCAM: pH (8.5, temperature (37 C, speed of agitation (50 rpm, enzyme concentration (0.080 µM, and substrate concentration (0.50 mM. Under these conditions, the yield of the reaction was ~15% in 1 h incubation period and ~63% after an overnight (~18 h incubation period. The product (p-HCAM of the reaction of PTAL with L-TM was confirmed using Nuclear Magnetic Resonance spectroscopy (NMR. Fourier Transform Infra-Red spectroscopy (FTIR was carried out to rule out potential hydrolysis of p-HCAM during overnight incubation. Potential antibacterial activity of p-HCAM was tested against several strains of Gram positive and Gram negative bacteria. This study describes a synthetically useful transformation, and could have future clinical and industrial applications.

  13. Rhodotorula glutinis Phenylalanine/Tyrosine Ammonia Lyase Enzyme Catalyzed Synthesis of the Methyl Ester of para-Hydroxycinnamic Acid and its Potential Antibacterial Activity.

    Science.gov (United States)

    MacDonald, Marybeth C; Arivalagan, Pugazhendhi; Barre, Douglas E; MacInnis, Judith A; D'Cunha, Godwin B

    2016-01-01

    Biotransformation of L-tyrosine methyl ester (L-TM) to the methyl ester of para- hydroxycinnamic acid (p-HCAM) using Rhodotorula glutinis yeast phenylalanine/tyrosine ammonia lyase (PTAL; EC 4.3.1.26) enzyme was successfully demonstrated for the first time; progress of the reaction was followed by spectrophotometric determination at 315 nm. The following conditions were optimized for maximal formation of p-HCAM: pH (8.5), temperature (37°C), speed of agitation (50 rpm), enzyme concentration (0.080 μM), and substrate concentration (0.50 mM). Under these conditions, the yield of the reaction was ∼15% in 1 h incubation period and ∼63% after an overnight (∼18 h) incubation period. The product (p-HCAM) of the reaction of PTAL with L-TM was confirmed using Nuclear Magnetic Resonance spectroscopy (NMR). Fourier Transform Infra-Red spectroscopy (FTIR) was carried out to rule out potential hydrolysis of p-HCAM during overnight incubation. Potential antibacterial activity of p-HCAM was tested against several strains of Gram-positive and Gram-negative bacteria. This study describes a synthetically useful transformation, and could have future clinical and industrial applications.

  14. Catalyzed Ceramic Burner Material

    Energy Technology Data Exchange (ETDEWEB)

    Barnes, Amy S., Dr.

    2012-06-29

    Catalyzed combustion offers the advantages of increased fuel efficiency, decreased emissions (both NOx and CO), and an expanded operating range. These performance improvements are related to the ability of the catalyst to stabilize a flame at or within the burner media and to combust fuel at much lower temperatures. This technology has a diverse set of applications in industrial and commercial heating, including boilers for the paper, food and chemical industries. However, wide spread adoption of catalyzed combustion has been limited by the high cost of precious metals needed for the catalyst materials. The primary objective of this project was the development of an innovative catalyzed burner media for commercial and small industrial boiler applications that drastically reduce the unit cost of the catalyzed media without sacrificing the benefits associated with catalyzed combustion. The scope of this program was to identify both the optimum substrate material as well as the best performing catalyst construction to meet or exceed industry standards for durability, cost, energy efficiency, and emissions. It was anticipated that commercial implementation of this technology would result in significant energy savings and reduced emissions. Based on demonstrated achievements, there is a potential to reduce NOx emissions by 40,000 TPY and natural gas consumption by 8.9 TBtu in industries that heavily utilize natural gas for process heating. These industries include food manufacturing, polymer processing, and pulp and paper manufacturing. Initial evaluation of commercial solutions and upcoming EPA regulations suggests that small to midsized boilers in industrial and commercial markets could possibly see the greatest benefit from this technology. While out of scope for the current program, an extension of this technology could also be applied to catalytic oxidation for volatile organic compounds (VOCs). Considerable progress has been made over the course of the grant

  15. Lipase-catalyzed synthesis of L-ascorbyl fatty acid esters and D-isoascorbyl fatty acid esters%脂肪酶催化合成L-抗坏血酸脂肪酸酯和D-异抗坏血酸脂肪酸酯

    Institute of Scientific and Technical Information of China (English)

    郑大贵; 祝显虹; 余泗莲; 彭化南; 张小兰

    2012-01-01

    The lipase-catalyzed synthesis of L.-ascorbyl fatty acid esters and D-isoascorbyl fatty acid esters were studied by direct es-terification and transesterification,respectively. The structures of products were confirmed by IR,1H NMR,13C NMR and MS. It was found that the yield of the direct esterification were higher than that of the corresponding transesterification under the similar synthetic conditions. The raw material fatty acids and fatty acid methyl esters could be recycled and reused.%用固定化脂肪酶Lipozyme 435作催化剂,分别用直接酯化法和酯交换法合成L-抗坏血酸脂肪酸酯和D-异抗坏血酸脂肪酸酯.产物结构经IR、1HNMR、13CNMR和MS表征.结果表明,对于同一目标化合物,相似条件下,直接酯化法的效果优于酯交换法,原料脂肪酸和脂肪酸甲酯均可回收循环使用.

  16. Liquefaction of wheat straw catalyzed by acidic ionic liquid and analysis of liquefied products%酸性离子液体催化麦秸液化及其产物分析

    Institute of Scientific and Technical Information of China (English)

    关倩; 蒋剑春; 徐俊明; 王奎; 冯君锋

    2016-01-01

    With the increasing energy requirements and pollution problems worldwide, energy from renewable resources has received global attention in recent decades. Biomass is one of the most abundant renewable resources. It mainly includes forest residues, agricultural wastes, industrial residues, municipal solid wastes, bagasse, aquatic plants, and algae animal wastes. Due to the advantages of abundance, non-polluting, being renewable and easy to obtain, biomass is considered as the most promising energy feedstock to replace the traditional energy. Meanwhile, it is the only resource that can be converted into solid, liquid, and gaseous products for use of fuels. Thermo-chemical conversion is an effective technology of biomass conversion. Liquefaction is the typical thermo-chemical technology for the conversion of biomass to obtain liquid biofuels and valuable chemicals, such as bio-oil and fuel additives. The conversion process is not only influenced by organic reagents but also by different catalysts. Effective catalyst is an essential factor to improve liquefaction efficiency. As catalyst, sulfuric acid has very strong corrosion and needs high-quality liquefaction equipment, and its recycling is difficult. Solid acid is used to overcome shortcomings of organic acid in the liquefaction, but it is easy to form coke to cause the deactivation of catalyst, and needs to be calcined before re-use, which increases the reaction cost. Now, it is found that the ionic liquid has non-corrosiveness, low melting point, high thermal stability and low vapor pressure, and some other merits. It has a broad application prospect used as solvents and catalysts in catalytic reactions. Ionic liquid, especially sulfonated bisulfate ionic liquid can dissolve cellulose, because it has higher acidic sites that can easily break the hydrogen bonds of biomass material, and promote the degradation and conversion of cellulose. At present, ionic liquid is usually used to catalyze carbohydrate, which is

  17. 杂交杨木纤维中碳水化合物的稀酸催化分离%Dilute Acid-catalyzed Fractionation of Carbohydrates in Hybrid Poplar Fibers

    Institute of Scientific and Technical Information of China (English)

    张春辉; Troy Runge; 詹怀宇

    2012-01-01

    In this paper, the acid-catalyzed fractionation of pentosans and hexosans from hybrid poplar fibers was studied using a circulation reactor. Kinetic models of both pentosan and hexosan hydrolysis/degradation were crea- ted to predict the hydrolysis yield of both substances. The extraction conditions were varied, including a tempera- ture range of 140 - 170℃ , a sulfuric acid concentration range of 0.1% - 0.9% wt with a constant liquor-to-wood ratio of 6: 1. The yields of both substances were favored at high acid concentration and temperature, while pentosan being considerable more reactive. Under optimal conditions, 91 percent of pentosan could be separated from the fi- ber, while more than 93 percent of hexosan was retained in the solids. This study demonstrates that pentosan and hexosans could be fractionated from poplar fibers using acid hydrolysis and converted into liquid fuel and valued chemicals separately.%本文采用循环式反应器研究了杂交杨木纤维中聚戊糖和聚己糖在稀酸条件下的催化分离,分别得出了聚戊糖和聚己糖稀酸水解/降解的动力学模型,以预测在不同反应条件下戊糖和己糖的水解得率。反应条件为温度140~170℃,硫酸浓度0.1%~0.9%wt,液比为6:1。研究发现,较高的酸浓和温度对提高戊糖和己糖的得率都有利,但相同条件下聚戊糖的反应活性更高。经动力学模型优化得出,在较佳条件下有91%的聚戊糖可以以单体、低聚体及其降解产物的形式从杨木纤维中分离出来,同时超过93%的聚己糖可以以固体的形式保留在纤维中。研究表明,在适宜的稀酸催化条件下杂交杨木纤维中的碳水化合物可以得到很好的分离,为下一步戊糖和聚己糖的分别单独转化打下了基础,不仅可以充分利用木材生物质资源,而且为反应提供了相对均一的条件,从而提高反应选择性和产物的纯度。

  18. Kinetic Study of Esterification of Lactic Acid with Isobutanol and n-Butanol Catalyzed by Ion-exchange Resins%离子交换树脂催化乳酸与异丁醇及正丁醇酯化反应的动力学研究

    Institute of Scientific and Technical Information of China (English)

    屈一新; 彭少君; 王水; 张志强; 王际东

    2009-01-01

    The esterification reactions of lactic acid with isobutanol and n-butanol have been studied in the presence of acid ion-exchange resin Weblyst D009. The influences of catalyst loading, stirrer speed, catalyst particle size, initial reactant molar ratio and temperature on the reaction rate have been examined. Experimental kinetic data were correlated by using the Pseudo-homogeneous, Langmuir-Hinshelwood and Eley-Rideal models. Nonideality of the liquid phase was taken into account by using activities instead of molar fractions. The activity coefficients were calculated according to the group contribution method UNIFAC. Provided that the nonideality of the liquid is taken into account, the esterification kinetics of lactic acid with isobutanol and n-butanol catalyzed by the acid ion-exchange resin can be described using all three models with reasonable errors.

  19. Chiral Diamine-catalyzed Asymmetric Aldol Reaction

    Institute of Scientific and Technical Information of China (English)

    LI Hui; XU Da-zhen; WU Lu-lu; WANG Yong-mei

    2012-01-01

    A highly efficient catalytic system composed of a simple and commercially available chiral primary diamine (1R,2R)-cyclohexane-1,2-diamine(6) and trifluoroacetic acid(TFA) was employed for asymmetric Aldol reaction in i-PrOH at room temperature.A loading of 10%(molar fraction) catalyst 6 with TFA as a cocatalyst could catalyze the Aldol reactions of various ketones or aldehydes with a series of aromatic aldehydes,furnishing Aldol products in moderate to high yields(up to >99%) with enantioselectivities of up to >99% and diastereoselectivities of up to 99:1.

  20. Ruthenium-catalyzed C–H activation of thioxanthones

    OpenAIRE

    Danny Wagner; Stefan Bräse

    2015-01-01

    Thioxanthones – being readily available in one step from thiosalicylic acid and arenes – were used in ruthenium-catalyzed C–H-activation reaction to produce 1-mono- or 1,8-disubstituted thioxanthones in good to excellent yields. Scope and limitation of this reaction are presented.

  1. Ruthenium-catalyzed C–H activation of thioxanthones

    Science.gov (United States)

    Wagner, Danny

    2015-01-01

    Summary Thioxanthones – being readily available in one step from thiosalicylic acid and arenes – were used in ruthenium-catalyzed C–H-activation reaction to produce 1-mono- or 1,8-disubstituted thioxanthones in good to excellent yields. Scope and limitation of this reaction are presented. PMID:25977717

  2. CU(II): catalyzed hydrazine reduction of ferric nitrate

    International Nuclear Information System (INIS)

    A method is described for producing ferrous nitrate solutions by the cupric ion-catalyzed reduction of ferric nitrate with hydrazine. The reaction is complete in about 1.5 hours at 400C. Hydrazoic acid is also produced in substantial quantities as a reaction byproduct

  3. Synthesis of DOTA-conjugated multimeric [Tyr3]octreotide peptides via a combination of Cu(I)-catalyzed "click" cycloaddition and thio acid/sulfonyl azide "sulfo-click" amidation and their in vivo evaluation.

    NARCIS (Netherlands)

    Yim, C.B.; Dijkgraaf, I.; Merkx, R.; Versluis, C.; Eek, A.; Mulder, G.E.; Rijkers, D.T.; Boerman, O.C.; Liskamp, R.M.

    2010-01-01

    Herein, we describe the design, synthesis, and biological evaluation of a series of DOTA-conjugated monomeric, dimeric, and tetrameric [Tyr(3)]octreotide-based analogues as a tool for tumor imaging and/or radionuclide therapy. These compounds were synthesized using a Cu(I)-catalyzed 1,3-dipolar cycl

  4. Lipase-catalyzed synthesis of monoacylglycerol in a homogeneous system.

    Science.gov (United States)

    Monteiro, Julieta B; Nascimento, Maria G; Ninow, Jorge L

    2003-04-01

    The 1,3-regiospecifique lipase, Lipozyme IM, catalyzed the esterification of lauric acid and glycerol in a homogeneous system. To overcome the drawback of the insolubility of glycerol in hexane, which is extensively used in enzymatic synthesis, a mixture of n-hexane/tert-butanol (1:1, v/v) was used leading to a monophasic system. The conversion of lauric acid into monolaurin was 65% in 8 h, when a molar ratio of glycerol to fatty acid (5:1) was used with the fatty acid at 0.1 M, and the phenomenon of acyl migration was minimized.

  5. Gas Chromatographic Analysis of Medium Chain Fatty Acids in Coconut Oil

    Directory of Open Access Journals (Sweden)

    Julius Pontoh

    2016-09-01

    Full Text Available Analysis of medium chain of fatty acids in coconut oil becomes important due to their roles in health issues. The present analysis methods for fatty acids present in food mainly focused to the overall fatty acid concentration. The analytical method for specific medium chain fatty acids is not so much be given attention. This research is focused to the analytical methods for these particular fatty acids in coconut oil. Several analytical methods were compared including acid catalyzed, basic catalyzed and acid boron trifluoride catalyzed derivatization. The response of each fatty acid toward the derivatization methods are different. Formation of the fatty acid methyl ester from caprylic and capric was low for acid catalyzed method compared to basic catalyzed method and acid boron trifluoride catalyzed methods. This finding shows that the kinetics of the esterification among the fatty acids are not the same. The analysis of all fatty acids in coconut oil is better using basic catalyzed than the other methods.

  6. 生物炭催化过硫酸盐脱色偶氮染料金橙Ⅱ%Biochar Catalyzed Persulfate Decoloration of Azo Dye Acid Orange 7

    Institute of Scientific and Technical Information of China (English)

    刘娜; 王柳; 邱华; Alberto Bento Charru; 王航; 王锐

    2014-01-01

    As a kind of inexpensive material-biochar,the function of soil restoration and other aspects has caused wide public concern,but its catalytic role has been studied rarely.The feasibility of persulfate (PS)catalyzed by biochar(BC)to decolor an azo dye (acid orange (AO7))was studied.Some factors influencing the decolorizing efficiency of PS/BC system were evaluated, including pH, concentration of biochar and PS/AO7 mole ratio.What’s more,the recycle effect and characteristics of biochar were studied.Results showed that the decolorizing effect of the PS/BC system was obviously better than the only PS system.The decoloration of AO7 by both reaction systems followed first order reaction kinetics. The optimum pH of PS/BC system was near-neutral. The higher the biochar concentration,the better the decolorizing effect was.Similar trend was observed for the PS/AO7 mole ratio,whereas the catalytic effect did not increase accordingly.The reused biochar could still decolor %生物炭作为一种廉价易得的材料,在土壤修复等各方面的功能已引起广泛关注,但其催化作用却鲜有研究。首次对生物炭(biochar BC)催化过硫酸盐(Na2 S2 O8 PS)使偶氮染料金橙Ⅱ(AO7)脱色的可行性进行研究,对影响催化体系脱色效率的因素(包括 pH、生物炭质量浓度和 PS/AO7摩尔比)进行探讨,同时研究了生物炭的重复利用效果及前后性质变化。结果表明:PS/BC 体系明显比单独的 PS 体系脱色效果好;两个反应体系都遵循一级反应动力学;PS/BC 体系反应的最适 pH 接近中性;生物炭质量浓度越大,脱色效果越好;PS/AO7摩尔比越大,脱色效果越好,但是催化效果却没有相应的改善;生物炭重复利用后对 AO7仍然有脱色效果;BC 的孔大多位于层状结构表面,且为小孔,重复使用后,表面孔会堵塞;除了灰分和氧元素外,其他元素(C、N、H、S)含量都有一定程度的减小;BC 表面官能团种类很多,主要

  7. Catalyzed Oxidation of Methanol on Acid/Base Modified VOx/Al2O3 Studied by Solid-state NMR%改性VOx/Al2O3催化剂催化氧化甲醇的固体核磁共振研究

    Institute of Scientific and Technical Information of China (English)

    曾丹林; 杨俊; 郑安民; 陈雷; 徐君; 叶朝辉; 邓风

    2007-01-01

    采用固体核磁共振研究了NaOH和HNO3改性的VOx/Al2O3上甲醇选择性催化氧化反应.实验结果表明:在甲醇的氧化反应中,酸位对二甲氧基甲烷的生成起了重要作用.与VOx/Al2O3催化剂相比,酸改性的VOx/Al2O3上的强的Bronsted酸位对二甲氧基甲烷的选择性较高,没有Bronsted酸位的碱改性的VOx/Al2O3上生成的不是二甲氧基甲烷而是甲酸盐.%Oxidation of methanol catalyzed by NaOH or HNO3 modified VOx/Al2O3 was studied by solid-state nuclear magnetic resonance (NMR) spectroscopy. The acid-treated VOx/Al2O3 catalyst showed stronger Bronsted acid sites compared to the unmodified VOx/Al2O3 catalyst, while the base-treated VOx/Al2O3 catalyst had no Bronsted acid sites. As a result, the former exhibited higher selectivity in producing dimethoxymethane from oxidation of methanol whereas the oxidation reaction catalyzed by the later yielded mainly formate. These results indicate that the Bronsted acid sites in VOx/Al2O3 catalysts play a key role in the oxidation reaction converting methanol to dimethoxymethane.

  8. 碱/酸两步催化法制备耐候性SiO2增透膜的研究%Preparation and Characterization of Environment-Resistant Silica Antireflective Coating by Base/Acid Two-Step Catalyzed Sol-Gel Process

    Institute of Scientific and Technical Information of China (English)

    业海平; 张欣向; 肖波; 晏良宏; 江波

    2011-01-01

    Antireflective (AR) coatings with high transmittance and abrasion-resistance were prepared by a two-step base/acid catalyzed sol-gel process using tetraethylorthosilicate (TEOS) as precursor. It was found that addition of 50% acid-catalyzed SiO2 in the sol afforded the AR coatings relatively high transmittance and enhanced abrasion-resistance. It provided the AR coating with highest transmittance while the mole ratio of nH2O/nHCl was 1∶0.001 0. The water contact angle of base/acid two-step catalyzed AR coating was 11.3°, in this work,hexamethyldisiloxane (HMDS) was further used to modify the hydrophobicity of AR coatings. After HMDS treatment, the hydroxyl groups of AR coating were replaced by -OSi (CH3)3, which greatly increases the hydrophobicity of the coating, affording HMDS modified AR coating excellent environment resistance.%以正硅酸乙酯(TEOS)为先驱体,采用碱/酸两步催化溶胶-凝胶法制备出一种兼具碱催化增透膜的高透过率和酸催化增透膜的良好耐摩擦性能的优点的SiO2增透膜.对酸碱催化SiO2相对比例及酸催化时水含量的系统研究表明,当酸催化SiO2的含量为50%时,增透膜综合性能最好,即具有高透过率和高耐摩擦性;当nH2o/nHCI=1∶0.0010时,增透膜的透过率最高.碱/酸两步催化法制备的增透膜与水的接触角仅为11.3°,本文进一步用六甲基二硅氧烷(HMDS)对增透膜表面进行了修饰,修饰后增透膜的接触角提高至52.5°,增透膜的疏水性及环境稳定性得到较大的提高.

  9. 硫酸存在时N-溴代苯二甲酰亚胺对甘露糖的胶束催化氧化%Micelle Catalyzed Oxidation of Mannose by N-Bromophthalimide in the Presence of Sulfuric Acid

    Institute of Scientific and Technical Information of China (English)

    KATRE Yokraj; SINGH Minu; PATIL Sangeeta; SINGH Ajaya K

    2009-01-01

    The kinetics of micellar-catalyzed oxidation of mannose by N-bromophthalimide was studied in the presence of sulfuric acid at 313 K. The orders of reaction with respect to [mannose], [oxidant], and [H+] were found to be fractional, first, and negative fractional order, respectively. Anionic micelles of sodium dodecyl sulfate showed a partial inhibitory effect, while cationic micelles of cetyltrimethylammonium bromide increased the reaction rate with the same kinetic behavior. The reaction was catalyzed by cationic micelles, because of favorable electrostatic/thermodynamic/ hydrophobic/hydrogen bonding between reactants and cationic micelles. Their catalytic roles are best explained by Berezin's model. A variation of [phthalimide] showed that the rate of reaction decreased with increasing [phthalimide]. It was observed that, an increase of [mercuric acetate] had no effect on reaction velocity. The influence of salts on the reaction rate was also studied. The rate constant (kw), binding constants (Ks+Ko), and corresponding activation parameters (Ea, △H#, △S#, and △G#) were determined. A detailed mechanism with associated reaction kinetics is presented and discussed.

  10. Inhibitory Effect of Ferulic Acid on Oxidation of L-DOPA Catalyzed by Mushroom Tyrosinase%阿魏酸对蘑菇酪氨酸酶的抑制效应

    Institute of Scientific and Technical Information of China (English)

    龚盛昭; 程江; 杨卓如

    2005-01-01

    The inhibitory effect of ferulic acid on the diphenolase activity of mushroom tyrosinase and the kinetic behavior were studied with L-3,4-dihydroxyphenylalanine (L-DOPA) as substrate. The inhibitor concentration from Lineweaver-Burk plots shows that ferulic acid is a competitive inhibitor and the inhibition of tyrosinase by ferulic acid is a reversible reaction. The equilibrium constant for ferulic acid binding with the tyrosinase was determined to be 0.25 mmol· L-1 for diphenolase.

  11. Stereoselective Palladium Catalyzed Cyclizations of Enediyne Compounds

    Energy Technology Data Exchange (ETDEWEB)

    Oh, Chang Ho; Rhim, Chul Yun; Jung, Hyung Hoon; Jung, Seung Hyun [Hanyang University, Seoul (Korea, Republic of)

    1999-06-15

    Hydropalladium carboxylates, formed from {pi}-allylpalladium chloride dimer plus carboxylic acids, have been shown to catalyze cyclization of structurally diverse enediynes to form the corresponding six- or five-membered rings depending upon the reaction conditions. Some enediynes having an oxygen linker in an appropriate position under the similar condition yielded the corresponding cyclopropanation products in highly stereoselective manner. A study using deuterated formic acid has proven that the alkylpalladium intermediates formed in our conditions were reduced by the pendant formate ligand. The dienediyne 10 yielded only the tricyclic product 12 in 67% yield, although it was expected to form the cyclic product 11. All these cyclizations seemed to occur via the corresponding alkylpalladium intermediates I, which could proceed to the corresponding cyclic products depending on the reaction conditions and the substrates. The study using deuterated formic acid could provide an important information to understand the present cyclization mechanism. Overall the present study could play an important role in developing new synthetic methodologies for constructing complex polycyclic compounds

  12. Gold-Catalyzed Synthesis of Heterocycles

    Science.gov (United States)

    Arcadi, Antonio

    2014-04-01

    The following sections are included: * Introduction * Synthesis of Heterocycles via Gold-Catalyzed Heteroatom Addition to Unsaturated C-C Bonds * Synthesis of Heterocyclic Derivatives through Gold-Catalyzed Cyclization of Polyunsaturated Compounds * Synthesis of Heterocyclic Compounds via α-Oxo Gold Carbenoid * Synthesis of Heterocyclic Derivatives through Gold-Catalyzed Cycloaddition Reactions * Synthesis of Heterocyclic Derivatives through Gold-Catalyzed Activation of Carbonyl Groups and Alcohols * Synthesis of Heterocyclic Compounds through Gold-Mediated C-H Bond Functionalization * Gold-Catalyzed Domino Cyclization/Oxidative Coupling Reactions * Conclusions * References

  13. Asymmetric Aldol Reaction Catalyzed by Modularly Designed Organocatalysts

    Institute of Scientific and Technical Information of China (English)

    Sinha, Debarshi; Mandal, Tanmay; Gogoi, Sanjib; Goldman, Joshua J.; 赵从贵

    2012-01-01

    The self-assembly of the precatalyst modules, which are amino acids and cinchona alkaloid derivatives, leads to the direct formation of the desired organocatalysts without any synthesis. These modularly designed organocatalysts (MDOs) may be used for catalyzed asymmetric aldol reaction the corresponding aldol products may be obtained in mediocre diastereoselectivities (up to 79 : 21 dr). Depending on structure of the aldehyde substrates, to excellent ee values (up to 92% ee) with moderate

  14. Modeling Lewis catalyzed reactions in Metal Organic Frameworks

    OpenAIRE

    Vandichel, Matthias; Cottenie, Stijn; Vermoortele, Frederik; De Vos, Dirk; Waroquier, Michel; Van Speybroeck, Veronique

    2011-01-01

    Recently, the spectrum of nanoporous materials like zeolites and zeotype structures has been further expanded through the discovery of a new class of hybrid porous solids [1]. Those materials, nowadays also known as metal organic frameworks or MOFs, consist of both inorganic and organic moieties. Certain MOFs exhibit a very interesting adsorption and even catalytic behavior [2]. Within this study, we will focus on the modeling of different Lewis acid catalyzed reactions in various MOFs: Cu co...

  15. Iodine-catalyzed coal liquefaction

    Energy Technology Data Exchange (ETDEWEB)

    Joseph, J.T.; Duffield, J.E.; Davidson, M.G. (Amoco Oil Company, Naperville, IL (USA). Research and Development Dept.)

    Coals of two different ranks were liquefied in high yields using catalytic quantities of elemental iodine or iodine compounds. Iodine monochloride was found to be especially effective for enhancing both coal conversion and product quality. It appears that enhancement in coal conversion is due to the unique ability of iodine to catalyze radical-induced bond scission and hydrogen addition to the coal macromolecule or coal-derived free radicals. The starting iodine can be fully accounted for in the reaction products as both organic-bound and water-soluble forms. Unconverted coal and the heavy product fractions contain the majority of the organic-bound iodine. The results of iodine-catalyzed coal reactions emphasize the need for efficient hydrogen atom transfer along with bond scission to achieve high conversion and product quality. 22 refs., 12 tabs.

  16. Asymmetric Stetter reactions catalyzed by thiamine diphosphate-dependent enzymes.

    Science.gov (United States)

    Kasparyan, Elena; Richter, Michael; Dresen, Carola; Walter, Lydia S; Fuchs, Georg; Leeper, Finian J; Wacker, Tobias; Andrade, Susana L A; Kolter, Geraldine; Pohl, Martina; Müller, Michael

    2014-12-01

    The intermolecular asymmetric Stetter reaction is an almost unexplored transformation for biocatalysts. Previously reported thiamine diphosphate (ThDP)-dependent PigD from Serratia marcescens is the first enzyme identified to catalyze the Stetter reaction of α,β-unsaturated ketones (Michael acceptor substrates) and α-keto acids. PigD is involved in the biosynthesis of the potent cytotoxic agent prodigiosin. Here, we describe the investigation of two new ThDP-dependent enzymes, SeAAS from Saccharopolyspora erythraea and HapD from Hahella chejuensis. Both show a high degree of homology to the amino acid sequence of PigD (39 and 51 %, respectively). The new enzymes were heterologously overproduced in Escherichia coli, and the yield of soluble protein was enhanced by co-expression of the chaperone genes groEL/ES. SeAAS and HapD catalyze intermolecular Stetter reactions in vitro with high enantioselectivity. The enzymes possess a characteristic substrate range with respect to Michael acceptor substrates. This provides support for a new type of ThDP-dependent enzymatic activity, which is abundant in various species and not restricted to prodigiosin biosynthesis in different strains. Moreover, PigD, SeAAS, and HapD are also able to catalyze asymmetric carbon-carbon bond formation reactions of aldehydes and α-keto acids, resulting in 2-hydroxy ketones.

  17. The mechanism of Fe (Ⅲ)-catalyzed ozonation of phenol

    Institute of Scientific and Technical Information of China (English)

    竹湘锋; 徐新华

    2004-01-01

    Fe (Ⅲ)-catalyzed ozonation yielded better degradation rate and extent of COD (Chemical Oxygen Demand) or oxalic acid as compared with oxidation by ozone alone. Two parameters with strong effects on the efficiency of ozonation are pH of the solution and the catalyst (Fe3+) dosage. The existence of a critical pH value determining the catalysis ofFe (Ⅲ) in acid conditions was observed in phenol and oxalic acid systems. The best efficiency of catalysis was obtained at a moderate concentration of the catalyst. A reasonable mechanism of Fe (Ⅲ)-catalyzed ozonation of phenol was obtained based on the results and literature.

  18. Efficient synthesis of spironaphthopyrano [2,3-d]pyrimidine-5,3'-indolines under solvent-free conditions catalyzed by SBA-Pr-SO3H as a nanoporous acid catalyst.

    Science.gov (United States)

    Ziarani, Ghodsi Mohammadi; Lashgari, Negar; Faramarzi, Sakineh; Badiei, Alireza

    2014-01-01

    A green, simple one-pot synthesis of spironaphthopyrano[2,3-d]pyrimidine-5,3'-indoline derivatives by a three-component reaction of isatins, 2-naphthol, and barbituric acids under solvent-free conditions in the presence of SBA-Pr-SO(3)H has been accomplished. Sulfonic acid functionalized SBA-15 (SBA-Pr-SO(3)H) as a heterogeneous nanoporous solid acid catalyst was found to be an efficient and recyclable acid catalyst in this synthesis. PMID:25286212

  19. An efficient synthesis of isocoumarins via a CuI catalyzed cascade reaction process

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    3-Alkyl isocoumarins are provided by CuI/amino acid-catalyzed Sonogashira coupling reaction of o-bromo benzoic acids and terminal alkynes and the subsequent additive cyclization. This cascade process allows synthesis of diverse isocoumarins by varying both coupling partners bearing a wide range of functional groups.

  20. The concise synthesis of chiral tfb ligands and their application to the rhodium-catalyzed asymmetric arylation of aldehydes

    OpenAIRE

    Nishimura, Takahiro; Kumamoto, Hana; Nagaosa, Makoto; Hayashi, Tamio

    2009-01-01

    New C2-symmetric tetrafluorobenzobarrelene ligands were prepared and applied successfully to the rhodium-catalyzed asymmetric addition of arylboronic acids to aromatic aldehydes giving chiral diarylmethanols in high yield with high enantioselectivity.

  1. Discussion on Synthesis and Reaction Mechanism of Chalcone Catalyzed by Acidic Ionic Liquids[BPy]HSO4 and[BMMIm]HSO4%酸性离子液体[BPy]HSO4和[BMMIm]HSO4催化合成查尔酮反应机理探讨

    Institute of Scientific and Technical Information of China (English)

    杜玉英; 韩利民; 李永栋; 竺宁; 张桂峰

    2012-01-01

    离子液体作为绿色的溶剂和催化剂具有很多独特的性质,特别是离子液体的可设计性,使其具有酸性可调的特点.分别以酸性离子液体[BPy] HSO4和[BMMIm] HSO4为催化剂,在无溶剂条件下考察了两种离子液体对Claisen-Schmidt缩合的不同催化效果,探讨了两种离子液体在查尔酮合成中可能的催化机理.%Ionic liquids (ILs) as green solvents and catalysts have unique properties such as a broad liquid range,good solvating ability,high thermal stability,and negligible vapor pressure,especially designability of ILs, which makes the acidity of ILs can be adjustable. [BPy]HSO4 and[BM-MIm]HSO4 acidic ILs catalyzing Claisen-Schmidt (CS) condensation of acetophenone with benzal-dehyde were investigated under solvent-free conditions. The plausible mechanism was elucidated for the synthesis of chalcone using the two ILs as Br0nsted acid catalysts.

  2. Fatty acid biosynthesis in actinomycetes

    OpenAIRE

    Gago, Gabriela; Diacovich, Lautaro; Arabolaza, Ana; Tsai, Shiou-Chuan; Gramajo, Hugo

    2011-01-01

    All organisms that produce fatty acids do so via a repeated cycle of reactions. In mammals and other animals, these reactions are catalyzed by a type I fatty acid synthase (FAS), a large multifunctional protein to which the growing chain is covalently attached. In contrast, most bacteria (and plants) contain a type II system in which each reaction is catalyzed by a discrete protein. The pathway of fatty acid biosynthesis in Escherichia coli is well established and has provided a foundation fo...

  3. The effects of zeolite and silica gel on synthesis of amylisobutyrate catalyzed by lipase from Candida rugosa

    OpenAIRE

    Stojaković Sanja B.; Bezbradica Dejan I.; Mijin Dušan Ž.; Knežević Zorica D.; Šiler-Marinković Slavica S.

    2008-01-01

    Lipase-catalyzed synthesis of esters has been widely investigated due to numerous advantages in comparison with the conventional chemical process catalyzed with concentrated acids since use of chemical catalysts leads to several problems. The most important disadvantages are corrosion of equipment, hazards of handling of the corrosive acids that are not reused, loss of conversion, yield and selectivity. The activity of water in reaction mixture seems to be one of the crucial factors affecting...

  4. A SABATH Methyltransferase from the moss Physcomitrella patens catalyzes

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Nan [ORNL; Ferrer, Jean-Luc [Universite Joseph Fourier, France; Moon, Hong S [Department of Plant Sciences, University of Tennessee; Kapteyn, Jeremy [Institute of Biological Chemistry, Washington State University; Zhuang, Xiaofeng [Department of Plant Sciences, University of Tennessee; Hasebe, Mitsuyasu [Laboratory of Evolutionary Biology, National Institute for Biology, 38 Nishigounaka; Stewart, Neal C. [Department of Plant Sciences, University of Tennessee; Gang, David R. [Institute of Biological Chemistry, Washington State University; Chen, Feng [University of Tennessee, Knoxville (UTK)

    2012-01-01

    Known SABATH methyltransferases, all of which were identified from seed plants, catalyze methylation of either the carboxyl group of a variety of low molecular weight metabolites or the nitrogen moiety of precursors of caffeine. In this study, the SABATH family from the bryophyte Physcomitrella patens was identified and characterized. Four SABATH-like sequences (PpSABATH1, PpSABATH2, PpSABATH3, and PpSABATH4) were identified from the P. patens genome. Only PpSABATH1 and PpSABATH2 showed expression in the leafy gametophyte of P. patens. Full-length cDNAs of PpSABATH1 and PpSABATH2 were cloned and expressed in soluble form in Escherichia coli. Recombinant PpSABATH1 and PpSABATH2 were tested for methyltransferase activity with a total of 75 compounds. While showing no activity with carboxylic acids or nitrogen-containing compounds, PpSABATH1 displayed methyltransferase activity with a number of thiols. PpSABATH2 did not show activity with any of the compounds tested. Among the thiols analyzed, PpSABATH1 showed the highest level of activity with thiobenzoic acid with an apparent Km value of 95.5 lM, which is comparable to those of known SABATHs. Using thiobenzoic acid as substrate, GC MS analysis indicated that the methylation catalyzed by PpSABATH1 is on the sulfur atom. The mechanism for S-methylation of thiols catalyzed by PpSABATH1 was partially revealed by homology-based structural modeling. The expression of PpSABATH1 was induced by the treatment of thiobenzoic acid. Further transgenic studies showed that tobacco plants overexpressing PpSABATH1 exhibited enhanced tolerance to thiobenzoic acid, suggesting that PpSABATH1 have a role in the detoxification of xenobiotic thiols.

  5. Thermodynamics of Enzyme-Catalyzed Reactions Database

    Science.gov (United States)

    SRD 74 Thermodynamics of Enzyme-Catalyzed Reactions Database (Web, free access)   The Thermodynamics of Enzyme-Catalyzed Reactions Database contains thermodynamic data on enzyme-catalyzed reactions that have been recently published in the Journal of Physical and Chemical Reference Data (JPCRD). For each reaction the following information is provided: the reference for the data, the reaction studied, the name of the enzyme used and its Enzyme Commission number, the method of measurement, the data and an evaluation thereof.

  6. Stau-catalyzed Nuclear Fusion

    OpenAIRE

    Hamaguchi, K.; Hatsuda, T.(Theoretical Research Division, Nishina Center, RIKEN, Saitama, 351-0198, Japan); Yanagida, T. T.

    2006-01-01

    We point out that the stau may play a role of a catalyst for nuclear fusions if the stau is a long-lived particle as in the scenario of gravitino dark matter. In this letter, we consider d d fusion under the influence of stau where the fusion is enhanced because of a short distance between the two deuterons. We find that one chain of the d d fusion may release an energy of O(10) GeV per stau. We discuss problems of making the stau-catalyzed nuclear fusion of practical use with the present tec...

  7. Gold-catalyzed naphthalene functionalization

    OpenAIRE

    Iván Rivilla; M. Mar Díaz-Requejo; Pedro J. Pérez

    2011-01-01

    The complexes IPrMCl (IPr = 1,3-bis(diisopropylphenyl)imidazol-2-ylidene, M = Cu, 1a; M = Au, 1b), in the presence of one equiv of NaBAr'4 (Ar' = 3,5-bis(trifluoromethyl)phenyl), catalyze the transfer of carbene groups: C(R)CO2Et (R = H, Me) from N2C(R)CO2Et to afford products that depend on the nature of the metal center. The copper-based catalyst yields exclusively a cycloheptatriene derivative from the Buchner reaction, whereas the gold analog affords a mixture of products derived either f...

  8. Stereoselectivity in (Acyloxy)borane-Catalyzed Mukaiyama Aldol Reactions.

    Science.gov (United States)

    Lee, Joshua M; Zhang, Xin; Norrby, Per-Ola; Helquist, Paul; Wiest, Olaf

    2016-07-01

    The origin of diastereo- and enantioselectivity in a Lewis acid-catalyzed Mukaiyama aldol reaction is investigated using a combination of dispersion corrected DFT calculations and transition state force fields (TSFF) developed using the quantum guided molecular mechanics (Q2MM) method. The reaction proceeds via a closed transition structure involving a nontraditional hydrogen bond that is 3.3 kJ/mol lower in energy than the corresponding open transition structure. The correct prediction of the diastereoselectivity of a Mukaiyama aldol reaction catalyzed by the conformationally flexible Yamamoto chiral (acyloxy) borane (CAB) requires extensive conformational sampling at the transition structure, which is achieved using a Q2MM-derived TSFF, followed by DFT calculations of the low energy conformational clusters. Finally, a conceptual model for the rationalization of the observed diastereo- and enantioselectivity of the reaction using a closed transition state model is proposed. PMID:27247023

  9. Mechanism of Intramolecular Rhodium- and Palladium-Catalyzed Alkene Alkoxyfunctionalizations

    KAUST Repository

    Vummaleti, Sai V. C.

    2015-11-13

    Density functional theory calculations have been used to investigate the reaction mechanism for the [Rh]-catalyzed intramolecular alkoxyacylation ([Rh] = [RhI(dppp)+] (dppp, 1,3-bis(diphenylphosphino)propane) and [Pd]/BPh3 dual catalytic system assisted intramolecular alkoxycyanation ([Pd] = Pd-Xantphos) using acylated and cyanated 2-allylphenol derivatives as substrates, respectively. Our results substantially confirm the proposed mechanism for both [Rh]- and [Pd]/ BPh3-mediated alkoxyfunctionalizations, offering a detailed geometrical and energetical understanding of all the elementary steps. Furthermore, for the [Rh]-mediated alkoxyacylation, our observations support the hypothesis that the quinoline group of the substrate is crucial to stabilize the acyl metal complex and prevent further decarbonylation. For [Pd]/BPh3-catalyzed alkoxycyanation, our findings clarify how the Lewis acid BPh3 cocatalyst accelerates the only slow step of the reaction, corresponding to the oxidative addition of the cyanate O-CN bond to the Pd center. © 2015 American Chemical Society.

  10. Research progress of lipase-catalyzed synthesis of L-ascorbyl organic acid ester%脂肪酶催化合成L-抗坏血酸有机酸酯的研究进展

    Institute of Scientific and Technical Information of China (English)

    蒋相军; 胡燚; 刘维明; 黄和

    2011-01-01

    To broaden the applications of L-ascorbic acid, it is an economical and feasible way to convert L-aseorbic acid into L-ascorbyl organic acid ester. The recent research progress of enzymatic synthesis of L-ascorbyl organic acid ester is summarized, by focusing on enzymatic synthesis of L-ascorbyl saturated fatty acid ester, unsaturated fatty acid ester and mixed fatty acid ester in organic solvents. The types of lipase, organic solvents and methods of separation and purification in the synthesis are discussed. Furthermore, the prospect of enzymatic synthesis of L-ascorbyl organic acid ester is also presented.%为了拓宽L-抗坏血酸酯在维护人体健康中的应用,将L-抗坏血酸转化成L-抗坏血酸酯是经济可行的手段。综述了近年来酶催化L-抗坏血酸有机酸酯的研究进展,重点介绍了有机相中L-抗坏血酸饱和脂肪酸酯、不饱和脂肪酸酯、脂肪酸混合酯的酶促合成,对于酶的种类、有机溶剂的选择及分离纯化方法进行了探讨,并对酶催化L-抗坏血酸有机酸酯合成前景进行了展望。

  11. Regiospecific O-Methylation of Naphthoic Acids Catalyzed by NcsB1, an O-Methyltransferase Involved in the Biosynthesis of the Enediyne Antitumor Antibiotic Neocarzinostatin*S⃞

    OpenAIRE

    Luo, Yinggang; Lin, Shuangjun; Zhang, Jian; Cooke, Heather A.; Bruner, Steven D.; Shen, Ben

    2008-01-01

    Neocarzinostatin, a clinical anticancer drug, is the archetypal member of the chromoprotein family of enediyne antitumor antibiotics that are composed of a nonprotein chromophore and an apoprotein. The neocarzinostatin chromophore consists of a nine-membered enediyne core, a deoxyaminosugar, and a naphthoic acid moiety. We have previously cloned and sequenced the neocarzinostatin biosynthetic gene cluster and proposed that the biosynthesis of the naphthoic acid moiety and its incorporation in...

  12. PHOSPHORUS PENTOXIDE-METHANESULFONIC ACID CATALYZED EFFICIENT SYNTHESIS OF 5-SUBSTITUTED 1H-TETRAZOLE DERIVATIVES Phosphorpentoxid-Methansulfonsäure KATALYSIERTEN EFFICIENT Synthese von 5-substituierten 1H-Tetrazolderivate

    Directory of Open Access Journals (Sweden)

    Amulrao U. Borse,Mahesh N. Patil, Nilesh L. Patil, and Sandesh R. Tetgure

    2012-07-01

    Full Text Available The mixture of phosphorus pentoxide-methanesulfonic acid (Eaton’s reagent is prove to be an efficient protocol for the [3+2] cycloaddition reaction between sodium azide and organic nitriles to give the corresponding 5-substituted 1H-tetrazole derivatives in good to excellent yields. The in situ formation of hydrazoic acid helps for the [3+2] cycloaddition reaction providing 5- substituted 1H-tetrazole with short reaction time.

  13. 漆酶催化4-香豆酸与聚木糖接枝改善其强度性能的研究∗%4-coumaric acid grafted onto xylan catalyzed by laccase for improving its strength properties

    Institute of Scientific and Technical Information of China (English)

    裴继诚; 王兵; 张方东; 李中阳; 殷允北

    2015-01-01

    利用漆酶催化,使4-香豆酸与聚木糖发生接枝共聚反应,从而改善聚木糖的成膜性能.通过红外光谱(FT-IR)、核磁共振碳谱(13 C NMR)、裂解-气相色谱/质谱(Py-GC/MS)联用等分析,表明接枝反应后聚木糖与4-香豆酸之间产生化学键连接,发生了接枝共聚反应;通过聚合度测试,接枝后聚木糖的聚合度提高了17.78%;薄膜拉伸性能的测试结果得出,接枝反应后聚木糖薄膜的杨氏模量提高了25.29%,拉伸强度提高了19.41%.聚木糖与4-香豆酸之间的接枝作用在增强薄膜性能中发挥了重要的作用,接枝后聚木糖制得的薄膜具有良好强度性能.%The reaction of graft copolymerization of xylan with 4-coumaric acid by laccase-catalyzed oxidation,in a way to improve quality of filming of xylan.It was analyzed by infrared FT-IR analysis,13 C NMR analysis,Py-GC/MS analysis techniques for determining the reaction between xylan and 4-coumaric acid which were chemi-cally connected,and occurred copolymer.By testing the degree of polymerization,results showed that the de-gree of polymerization of the xylan improved 17.78%;and the films showed a significant increase in Young's modulus by 25.29%,tensile strength increased from 0.601 to 0.753 MPa and 1.020 to 1.218 MPa,respectively. The grafting between xylan and laccase-catalyzed oxidation of 4-coumaric acid played an important role in rein-forcing the films.The superior properties of the new films could have great potential applications.

  14. Synthesis of n-butyl p-hydroxyl benzoate catalyzed by dawson structure phosphotungstic acid%Dawso结构磷钨酸催化合成对羟基苯甲酸正丁酯

    Institute of Scientific and Technical Information of China (English)

    曹小华; 张杨帆; 徐常龙; 叶兴琳; 周德志

    2015-01-01

    Preparation of n-butyl p-hydroxybenzoate by the esterification of p-hydroxy benzoic acid and n-butanol using dawson structure phosphotungstic acid as catalyst was reported. The catalyst was characterized by Py-IR and NH3-TPD. The main influential factors of reaction were investigated by orthogonal experiments and the possible reaction mechanism was discussed. Py-IR results showed that both Bronsted(B)acid sites and Lewis(L)acid sites co-exist on the surface of the catalyst. The results of NH3-TPD suggested that the catalyst possessed weak,medium and strong acid sites,among which the medium acid sites accounted for the lar-gest proportion. The results obtained indicated that the esterification reaction was a Brö nsted acid-Lewis acid cooperativity catalytic reaction. Dawson structure phosphotungstic acid possessed a fairly high catalytic activity for the esterification reaction. The optimal condition could be listed as follows:the best reaction temperature was 125℃,the reaction time was 3. 0 h,the mass ratio of the cata-lyst to total reactants was 4. 9%,and the molar ratio of n-butyl alcohol to p-hydroxyl benzoic acid was 2∶1. Under these conditions, the yield of butyl p-hydroxyl benzoate could reach 91. 3%, and it was still over 70. 3%when the catalyst was reused for five times. The primary advantage of replacement of sulphuric acid to dawson structure phosphotungstic acid might be not only as the im-provement of yield and selectivity,but also the simplification of the process and the reduction of environmental pollution. The cata-lyst could be used repeatedly after being treated simply.%以对羟基苯甲酸和正丁醇为原料、Dawson结构磷钨酸( H6 P2 W18 O62·13H2 O)为催化剂,催化对合成对羟基苯甲酸正丁酯,并对催化剂进行Py-IR、NH3-TPD表征。通过正交实验考察了各因素对酯收率的影响,探索了反应机理。 Py-IR结果显示催化剂同时具有Brönsted酸中心和Lewis酸中心,NH3-TPD证实催化剂表面

  15. Unprecedentedly mild direct Pd-catalyzed arylation of oxazolo[4,5-b]pyridine

    DEFF Research Database (Denmark)

    Zhuravlev, Fedor

    2006-01-01

    Pd-catalyzed C-2 arylation of oxazolo[4,5-b]pyridine proceeds efficiently at 30 degrees C and tolerates a variety of aryl halides, including derivatized amino acids for which no racemization was observed during the reaction. Experimental evidence for facile deprotonation of oxazolo[4,5-b]pyridine......Pd-catalyzed C-2 arylation of oxazolo[4,5-b]pyridine proceeds efficiently at 30 degrees C and tolerates a variety of aryl halides, including derivatized amino acids for which no racemization was observed during the reaction. Experimental evidence for facile deprotonation of oxazolo[4,5-b...

  16. Gold-catalyzed formation of pyrrolo- and indolo-oxazin-1-one derivatives: The key structure of some marine natural products

    OpenAIRE

    Sultan Taskaya; Nurettin Menges; Metin Balci

    2015-01-01

    Various N-propargylpyrrole and indolecarboxylic acids were efficiently converted into 3,4-dihydropyrrolo- and indolo-oxazin-1-one derivatives by a gold(III)-catalyzed cyclization reaction. Some of the products underwent TFA-catalyzed double bond isomerization and some did not. Cyclization reactions in the presence of alcohol catalyzed by Au(I) resulted in the formation of hemiacetals after cascade reactions.

  17. Gold-catalyzed formation of pyrrolo- and indolo-oxazin-1-one derivatives: The key structure of some marine natural products

    Directory of Open Access Journals (Sweden)

    Sultan Taskaya

    2015-05-01

    Full Text Available Various N-propargylpyrrole and indolecarboxylic acids were efficiently converted into 3,4-dihydropyrrolo- and indolo-oxazin-1-one derivatives by a gold(III-catalyzed cyclization reaction. Some of the products underwent TFA-catalyzed double bond isomerization and some did not. Cyclization reactions in the presence of alcohol catalyzed by Au(I resulted in the formation of hemiacetals after cascade reactions.

  18. AN EFFICIENT SYNTHESIS OF 1,3-DIOXANE-4,6-DIONES CATALYZED BY BORIC ACID. Eine effiziente Synthese von 1,3-Dioxan-4 ,6-dione BY BORSÄURE katalysierten

    Directory of Open Access Journals (Sweden)

    Zhao hui XU*,Chun hua Lin ,Jian hui Xia

    2013-07-01

    Full Text Available Several kinds of 1,3-dioxane-4,6-diones have been synthesized from malonic acid and ketones using boric acid as catalyst, acetic anhydride as condensing regent at room temperature. The present method does not involve any hazardous organic solvents, it gives some notable advantages such as mild reaction conditions, short reaction time,less catalyst dosage and high yields.Further study showed that H3BO3 was reused for four times without any noticeable decrease in the catalytic activity.

  19. Can laccases catalyze bond cleavage in lignin?

    DEFF Research Database (Denmark)

    Munk, Line; Sitarz, Anna Katarzyna; Kalyani, Dayanand;

    2015-01-01

    illustrations of the putative laccase catalyzed reactions, including the possible reactions of the reactive radical intermediates taking place after the initial oxidation of the phenol-hydroxyl groups, we show that i) Laccase activity is able to catalyze bond cleavage in low molecular weight phenolic lignin...

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

    Science.gov (United States)

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

    2016-05-01

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

  1. Microwave-assisted solvent-free synthesis of 14-aryl/alkyl-14H-dibenzo[a,j]xanthenes and tetrahydrobenzo[a]xanthen-11-ones catalyzed by nano silica phosphoric acid

    OpenAIRE

    Abdolhamid Bamoniri; Bi Bi Fatemeh Mirjalili; Sedigeh Nazemian

    2013-01-01

    Nano silica phosphoric acid (nano SPA) was applied as a catalyst for synthesis of 14-aryl/alkyl-14H-dibenzo[a,j]xanthenes and tetrahydrobenzo[a]xanthen-11-ones in microwave oven under solvent free conditions. High efficiency, easy availability and reusability are some advantages of this catalyst.

  2. 微波辐射硫酸氢钠催化合成对氨基苯甲酸苄酯%Synthesis of 4-aminobenzoic acid benzyl ester catalyzed by sodium bisulfate under microwave radiation

    Institute of Scientific and Technical Information of China (English)

    杨晓军; 李西安

    2011-01-01

    在微波辐射下,以一水合硫酸氢钠为催化剂,对氨基苯甲酸和苯甲醇为原料,合成对氨基苯甲酸苄酯.结果表明,当微波辐射功率为500W,0.05mol对氨基苯甲酸为基准,催化剂的用量为1.6 g,酸醇的摩尔比为1∶1.2,反应时间14 min时,醋化率达93.8%.%The 4-aminobcnzoic acid benzyl ester was synthesized under microwave radiacion from 4-aminobenzoic acid and benzyl alcohol using sodium bisulfate as catalyst. When the power of microwave radiation was 500 W, amount of catalyst was 1. 6 g, the molar ratio of acid to alcohol was 1∶ 1.2( using 0. 05 mol of 4-aminobenzoic acid ) and reaction time was 14 min, the yield reached 93. 8% .

  3. Gold-catalyzed naphthalene functionalization

    Directory of Open Access Journals (Sweden)

    Iván Rivilla

    2011-05-01

    Full Text Available The complexes IPrMCl (IPr = 1,3-bis(diisopropylphenylimidazol-2-ylidene, M = Cu, 1a; M = Au, 1b, in the presence of one equiv of NaBAr'4 (Ar' = 3,5-bis(trifluoromethylphenyl, catalyze the transfer of carbene groups: C(RCO2Et (R = H, Me from N2C(RCO2Et to afford products that depend on the nature of the metal center. The copper-based catalyst yields exclusively a cycloheptatriene derivative from the Buchner reaction, whereas the gold analog affords a mixture of products derived either from the formal insertion of the carbene unit into the aromatic C–H bond or from its addition to a double bond. In addition, no byproducts derived from carbene coupling were observed.

  4. Catalyzed electrolytic plutonium oxide dissolution

    International Nuclear Information System (INIS)

    Catalyzed electrolytic plutonium oxide dissolution (CEPOD) was first demonstrated at Pacific Northwest Laboratory (PNL) in early 1974 in work funded by the Exxon Corporation. The work, aimed at dissolution of Pu-containing residues remaining after the dissolution of spent mixed-oxide reactor fuels, was first publicly disclosed in 1981. The process dissolves PuO2 in an anolyte containing small (catalytic) amounts of elements that form kinetically fast, strongly oxidizing ions. These are continuously regenerated at the anode. Catalysts used, in their oxidized form, include Ag2+, Ce4+, Co3+, and AmO22+. This paper reviews the chemistry involved in CEPOD and the results of its application to the dissolution of the Pu content of a variety of PuO2-containing materials such as off-standard oxide, fuels dissolution residues, incinerator ash, contaminated soils, and other scraps or wastes. Results are presented for both laboratory-scale and plant-scale dissolves

  5. Synthesis of Free Amino Acid Esters Co-catalyzed by Ionic Liquid%离子液体协同催化合成游离氨基酸酯

    Institute of Scientific and Technical Information of China (English)

    尚岩; 贾俊英; 高海鹏; 裴蕾; 仲昭琪

    2011-01-01

    以L-氨基酸和醇为原料,酸性离子液体辅以少量强酸性阳离子交换树脂作催化剂,直接酯化合成了8种游离的L-氨基酸酯,并用1HNMR对产物进行了表征.通过L-苯丙氨酸正丁酯的合成对离子液体的活性进行了考察,结果表明,所选用的11种离子液体在反应过程中均起到了一定的催化作用和助溶作用.其中,[Hmim][HSO4]效果较好,在重复使用后,显示了较好的稳定性,是氨基酸酯化反应理想的催化剂和助溶剂.%Eight kinds of free L-amino acid esters including L-phenylalanine ethyl ester, L-phenylalanine n-butyl ester, L-phenylalanine i-butyl ester, L-tyrosine n-butyl ester, L-tyrosine i-butyl ester, L-tyrosine i-amyl ester, L-aspartic n-butyl diester and L-aspartic i-butyl diester were synthesized by direct esterification of L-amino acid and alcohol with acidic ionic liquid assisted by strong acidic cation resin as catalyst. The structures of free L-amino acid esters were characterized by 1HNMR.Optimal reaction conditions were obtained when synthesizing L-phenylalanine n-butyl ester. Among eleven kinds of the acidic ionic liquids used in this case, [Hmim] [ HSO4 ] indicated excellent activity and the catalyst is easily regenerated and reused. By this token, it exhibits its potential application as catalyst and co-solvent in the esterification of amino acid.

  6. Hydrogen evolution catalyzed by cobaloximes.

    Science.gov (United States)

    Dempsey, Jillian L; Brunschwig, Bruce S; Winkler, Jay R; Gray, Harry B

    2009-12-21

    Natural photosynthesis uses sunlight to drive the conversion of energy-poor molecules (H(2)O, CO(2)) to energy-rich ones (O(2), (CH(2)O)(n)). Scientists are working hard to develop efficient artificial photosynthetic systems toward the "Holy Grail" of solar-driven water splitting. High on the list of challenges is the discovery of molecules that efficiently catalyze the reduction of protons to H(2). In this Account, we report on one promising class of molecules: cobalt complexes with diglyoxime ligands (cobaloximes). Chemical, electrochemical, and photochemical methods all have been utilized to explore proton reduction catalysis by cobaloxime complexes. Reduction of a Co(II)-diglyoxime generates a Co(I) species that reacts with a proton source to produce a Co(III)-hydride. Then, in a homolytic pathway, two Co(III)-hydrides react in a bimolecular step to eliminate H(2). Alternatively, in a heterolytic pathway, protonation of the Co(III)-hydride produces H(2) and Co(III). A thermodynamic analysis of H(2) evolution pathways sheds new light on the barriers and driving forces of the elementary reaction steps involved in proton reduction by Co(I)-diglyoximes. In combination with experimental results, this analysis shows that the barriers to H(2) evolution along the heterolytic pathway are, in most cases, substantially greater than those of the homolytic route. In particular, a formidable barrier is associated with Co(III)-diglyoxime formation along the heterolytic pathway. Our investigations of cobaloxime-catalyzed H(2) evolution, coupled with the thermodynamic preference for a homolytic route, suggest that the rate-limiting step is associated with formation of the hydride. An efficient water splitting device may require the tethering of catalysts to an electrode surface in a fashion that does not inhibit association of Co(III)-hydrides. PMID:19928840

  7. Nitroreductase catalyzed biotransformation of CL-20.

    Science.gov (United States)

    Bhushan, Bharat; Halasz, Annamaria; Hawari, Jalal

    2004-09-10

    Previously, we reported that a salicylate 1-monooxygenase from Pseudomonas sp. ATCC 29352 biotransformed CL-20 (2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaaza-isowurtzitane) (C(6)H(6)N(12)O(12)) and produced a key metabolite with mol. wt. 346 Da corresponding to an empirical formula of C(6)H(6)N(10)O(8) which spontaneously decomposed in aqueous medium to produce N(2)O, NH(4)(+), and HCOOH [Appl. Environ. Microbiol. (2004)]. In the present study, we found that nitroreductase from Escherichia coli catalyzed a one-electron transfer to CL-20 to form a radical anion (CL-20(-)) which upon initial N-denitration also produced metabolite C(6)H(6)N(10)O(8). The latter was tentatively identified as 1,4,5,8-tetranitro-1,3a,4,4a,5,7a,8,8a-octahydro-diimidazo[4,5-b:4',5'-e]pyrazine [IUPAC] which decomposed spontaneously in water to produce glyoxal (OHCCHO) and formic acid (HCOOH). The rates of CL-20 biotransformation under anaerobic and aerobic conditions were 3.4+/-0.2 and 0.25+/-0.01 nmol min(-1)mg of protein(-1), respectively. The product stoichiometry showed that each reacted CL-20 molecule produced about 1.8 nitrite ions, 3.3 molecules of nitrous oxide, 1.6 molecules of formic acid, 1.0 molecule of glyoxal, and 1.3 ammonium ions. Carbon and nitrogen products gave mass-balances of 60% and 81%, respectively. A comparative study between native-, deflavo-, and reconstituted-nitroreductase showed that FMN-site was possibly involved in the biotransformation of CL-20. PMID:15313201

  8. Reduction of nitrobenzene by the catalyzed Fe/Cu process

    Institute of Scientific and Technical Information of China (English)

    XU Wenying; LI Ping; FAN Jinhong

    2008-01-01

    The polarization behavior of the couple Fe/Cu in 100 mg/L nitrobenzene aqueous solution was studied using Evans coupling diagrams. The results indicated that the iron corrosion was limited by both anodic and cathodic half-cell reactions under the neutral conditions and cathodically controlled under the alkaline conditions. Batch experiments were performed to study the effect of solution pH, reaction duration, concentration, type of electrolyte and dissolved oxygen (DO) on the reduction of nitrobenzene by the catalyzed Fe/Cu process. This process proved effective in the pH range of 3 to 11. The conversion efficiency of nitrobenzene at pH ≈ 10.1 was almost the same as that under highly acid conditions (pH ≈ 3). The degradation of nitrobenzene fell into two phases: adsorption and surface reduction, and the influence of adsorption and mass transfer became more extensive with solution concentration. The reduction rate decreased in the presence of DO in the solution, indicating that a need for aeration was eliminated in the catalyzed Fe/Cu process. Accordingly, spending on energy consumption would be reduced. Economic analysis indicated that merely 0.05 kg was required for the treatment of a ton of nitrobenzene-containing water with pH from 3 to 11. The catalyzed Fe/Cu process is cost-effective and of practical value.

  9. Study on the synthesis of phenoxyacetic acid with the polyethylene glycol-600 by phase transfer catalyzed method%聚乙二醇-600相转移催化合成苯氧乙酸的研究

    Institute of Scientific and Technical Information of China (English)

    程冬梅; 王学明; 张铁军

    2011-01-01

    研究了用杉甲苯作反应介质,在相转移催化剂聚乙二醇-600的作用下,以苯酚、氯乙酸水溶液和氢氧化钠水溶液为原料合成苯氧乙酸的新工艺,较系统地研究了苯酚/氯乙酸摩尔比、催化剂用量、反应时间等因素对产品收率的影响.实验结果表明,最佳条件为:苯酚、氯乙酸摩尔比为1:1.2,催化剂用量占苯酚和氯乙酸的质量百分比为9.5%,在回流状态下反应2.5h.该工艺具有反应条件温和的优点,收率达到83.5%,含量在90%左右.%The new craft of the synthesis of phenoxyacetic acid, which takes phenol, chloroacetic acid and sodium hydroxide water-soluble fluid as the raw material, polyethylene glycol-600 as the phase transfer catalyst and water/toluene as the reaction medium, is studied in this paper. The effects of the molar ratio of phenol and chloroacetic acid, catalyst dosage and reaction time on the yield were studied systematically. The experiment re- suits showed that the optimal reaction conditions are as follows : the molar ratio of phenol to chloroacetic acid is 1:1.2,the quality percentage of catalyst amount in phenol and chloroacetic acid was 9.5% ,and reflux reac- tion time is 2.5 h. The reaction condition was mild, the yield can reach 83.5%, and the content was about 90%.

  10. Heterogeneous oxidation of cyclohexanone catalyzed by TS-1:Combined experimental and DFT studies

    Institute of Scientific and Technical Information of China (English)

    Changjiu Xia; Xingtian Shu; Long Ju; Yi Zhao; Hongyi Xu; Bin Zhu; Feifei Gao; Min Lin; Zhenyu Dai; Xiaodong Zou

    2015-01-01

    The reaction mechanism of the oxidation of cyclohexanone catalyzed by titanium silicate zeolite TS-1 using aqueous H2O2 as the oxidant was investigated by combining density function theory (DFT) calculations with experimental studies. DFT calculations showed that H2O2 was adsorbed and activated at the tetrahedral Ti sites. By taking into account the adsorption energy, molecular size, steric hindrance and structural information, a reaction mechanism of Baeyer-Villiger oxidation catalyzed by TS-1 that involves the activation of H2O2 was proposed. Experimental studies showed that the major products of cyclohexanone oxidation by H2O2 catalyzed by a hollow TS-1 zeolite wereε-carprolactone, 6-hydroxyhexanoic acid, and adipic acid. These products were analyzed by GC-MS and were in good agreement with the proposed mechanism. Our studies showed that the reaction mechanism on TS-1 zeolite was different from that on Sn-beta zeolite.

  11. Deoxyribonucleoside kinases: two enzyme families catalyze the same reaction

    DEFF Research Database (Denmark)

    Sandrini, Michael; Piskur, Jure

    2005-01-01

    Mammals have four deoxyribonucleoside kinases, the cytoplasmic (TK1) and mitochondrial (TK2) thymidine kinases, and the deoxycytidine (dCK) and deoxyguanosine (dGK) kinases, which salvage the precursors for nucleic acids synthesis. In addition to the native deoxyribonucleoside substrates, the kin......, the kinases can phosphorylate and thereby activate a variety of anti-cancer and antiviral prodrugs. Recently, the crystal structure of human TK1 has been solved and has revealed that enzymes with fundamentally different origins and folds catalyze similar, crucial cellular reactions....

  12. The synthesis of mono- and diacetyl-9H-fluorenes. Reactivity and selectivity in the Lewis acid catalyzed Friedel-Crafts acetylation of 9H-fluorene

    DEFF Research Database (Denmark)

    Titinchi, Salam J.J.; Kamounah, Fadhil S.; Abbo, Hanna S.;

    2008-01-01

    Friedel-Crafts acetylation of 9H-fluorene is an effective route for the preparation of mono- and diacetyl-9H-fluorenes. Using acetylchloride as the reagent and aluminum chloride as the Lewis acid catalyst the effect of the solvent polarity, the temperature, the reaction time and the mode of......-fluorene was obtained in 5-11 % yield when carbon disulfide was used as the solvent. Acetylation of 9H-fluorene in dichloroethane and carbon disulfide, using an excess of acetyl chloride and aluminum chloride at reflux temperature, gives 2,7-diacetyl-9H-fluorene exclusively in high yields (> 97%). Attempts to...

  13. Decomposition Studies of Triphenylboron, Diphenylborinic Acid and Phenylboric Acid in Aqueous Alkaline Solutions Containing Copper

    Energy Technology Data Exchange (ETDEWEB)

    Crawford, C.L. [Westinghouse Savannah River Company, AIKEN, SC (United States); Peterson, R. A.

    1997-02-11

    This report documents the copper-catalyzed chemical kinetics of triphenylboron, diphenylborinic acid and phenylboric acid (3PB, 2PB and PBA) in aqueous alkaline solution contained in carbon-steel vessels between 40 and 70 degrees C.

  14. Br(o)nsted酸性离子液体催化3,4-二氢嘧啶-2-酮衍生物的合成%Synthesis of 3,4-Dihydropyrimidin-2(1H)-ones Catalyzed by Br(o)nsted Acidic Ionic Liquid

    Institute of Scientific and Technical Information of China (English)

    刘伟华; 高书涛; 冯成; 臧晓欢; 周欣; 马晶军; 王春

    2012-01-01

    以Br(o)nsted酸性离子液体3-甲基咪唑丙烷磺酸-三氟乙酸作为催化剂,无溶剂条件下由芳香醛、乙酰乙酸乙酯和尿素合成了系列3,4-二氢嘧啶-2-酮衍生物.沸水浴中反应30~40 min,产物产率在81%~94%之间.该方法具有反应时间短、收率高、催化剂可回收重复使用等优点.产物结构经1H NMR,IR确证.%A series of 3,4-dihydropyrimidin-2(1H)-ones were prepared through the Biginelli condensation reactions of aromatic aldehydes, keto ester and urea catalyzed by Bronsted acidic ionic liquid 3-methyl-l-(3-sulfopropyl)-imidazolium trifluoroacetate under solvent free conditions. The method is simple, solvent free, high yields and environmental friendly. The catalyst could be recycled and reused. The reactions were carried out in boiling water bath for 30~40 min. The yields of the products were between 81%-4%. All the products have been characterized by 1H NMR and IR spectra.

  15. Studies on oxidative desulfurization (Part 1). Phase-transfer catalyzed oxidation of organic sulfur compounds

    Energy Technology Data Exchange (ETDEWEB)

    Toritani, Koji; Nishida, Hiroshi; Sonoda, Takaaki; Kobayashi, Hiroshi

    1987-03-25

    For application to the desulfurization of coal liquids, selective oxidations of organically bound sulfur were examined under phase-transfer catalyzed conditions. A range of inorganic oxidants were applied to phenyl sulfide, benzyl sulfide, dibenzothiophene, and benzo(b) thiophene. Peroxydisulfate in concentrated sulfuric acid was the most efficent compared to the corresponding sulfoxides and sulfur dioxides. (2 figs, 3 tabs, 12 refs)

  16. Palladium-Catalyzed Carbonylation of Aryl Bromides with N-Substituted Cyanamides

    DEFF Research Database (Denmark)

    Lian, Zhong; Friis, Stig D.; Lindhardt, Anders T.;

    2014-01-01

    The palladium(0)-catalyzed three-component coupling reaction of aryl bromides, carbon monoxide, and N-alkyl cyan­amides has been developed employing a two-chamber system with ex situ generation of carbon monoxide from a silacarboxylic acid. The reactions proceeded well and were complete with a...

  17. The Isomerization of (-)-Menthone to (+)-Isomenthone Catalyzed by an Ion-Exchange Resin

    Science.gov (United States)

    Ginzburg, Aurora L.; Baca, Nicholas A.; Hampton, Philip D.

    2014-01-01

    A traditional organic chemistry laboratory experiment involves the acid-catalyzed isomerization of (-)-menthone to (+)-isomenthone. This experiment generates large quantities of organic and aqueous waste, and only allows the final ratio of isomers to be determined. A "green" modification has been developed that replaces the mineral acid…

  18. Ruthenium-catalyzed C-H/N-O bond functionalization: green isoquinolone syntheses in water.

    OpenAIRE

    Ackermann, Lutz; Fenner, Sabine

    2011-01-01

    Ruthenium-catalyzed isoquinolone syntheses with ample scope were accomplished through carboxylate assistance in environmentally benign water as a reaction medium. The high chemoselectivity of the ruthenium(II) carboxylate complex also set the stage for the direct use of free hydroxamic acids for annulations of alkynes.

  19. 酸性离子液体中八聚钼酸盐相转移催化氧化脱硫的研究%Phase transfer catalytic oxidative desulfurization of fuels catalyzed by octamolybdate in acidic ionic liquids

    Institute of Scientific and Technical Information of China (English)

    葛建华; 周钰明; 高良敏; 胡友彪

    2013-01-01

    制备了四种八聚钼酸盐催化剂:[(C4H9)4N]4Mo8O26,[(C12H25)N(CH3)3]4Mo8O26,[(C14H29)N (CH3)3]4Mo8O26和[(C16H33)N(CH3)3]4Mo8O26.通过元素分析,TG/DSC,FT-IR和紫外-可见光谱等方法对这四种催化剂的组成和结构进行了相应表征.研究了八聚钼酸季铵盐催化剂在酸性离子液体中相转移催化氧化脱硫活性.同时考察了在不同脱硫体系和催化剂、温度(T)、时间(t)、氧化剂(H2O2)用量、催化剂用量、以及酸性离子液体的种类等因素对脱硫效果的影响.经过对反应条件优化,当在70℃下反应3h,n(H2O2)∶n(DBT)=4∶1,n(DBT)∶n(Catalyst)=10∶1,离子液体[(CH2)3SO3 HMIm] BF4用量为1mL,模拟油品中二苯并噻吩(DBT)脱除率可以达到98.3%,且循环反应6次后催化反应活性没有明显的下降,可以用来进行深度脱硫.最后,对该脱硫体系的脱硫机理进行了讨论.%Four Surfactant-type octamolybdates were synthesized and characterized,and then used as effective catalysts associated with 30% H2O2 as oxidant in the acidic ionic liquid,which has been found suitable for deep removal of organic sulfur in fuels.In this catalytic oxidation desulfurization system,the main factors affecting the desulfurization process include temperature,the reaction time,the dosage of H2O2 and catalyst,as well as the type of acidic ionic liquids.All these factors played significant roles in desulfurization efficiency,under the favorable conditions.The sulfur removal could reach almost 98.3%,which was much better than desulfurization performance by simple extraction with acidic ionic liquid.Moreover,this acidic ionic liquid can be recycled six times by distillation without obviously decrease in activity.Meanwhile,the mechanism of oxidation desulfurization was also elaborated.

  20. Ester Exchange Polymerization of 3-Hydroxyl Propionic Acid Methyl Ester Catalyzed by SO3 H-functionalized Ionic Liquids%磺酸功能化离子液体催化3-羟基丙酸甲酯酯交换聚合反应

    Institute of Scientific and Technical Information of China (English)

    徐国荣; 刘建华; 宋大勇; 陈静; 夏春谷

    2012-01-01

    Employing SO3 H-functionalized ionic liquids as catalysts, the biodegradable poly [ 3-hydroxypropionic acid] (PHP) was obtained by ester exchange polymerization of 3-Hydroxyl propionie acid methyl ester(3-HPM). The effects of various ionic liquids, reaction temperature and reaction time on the polymerization performance were discussed in detail. Meanwhile, the FFIR, NMR and TG-DSC were applied to characterize the products. The PHP with Mw above 1.0×104 and yield above 82% could be obtained when catalyzed by [ BsMIm] [ OTf] under the opti- mal reaction conditions. In addition, the catalyst in the polymer could be removed completely after washing with water, efficiently avoiding the pollution of the product.%以磺酸功能化咪唑离子液体为催化剂,以3-羟基丙酸甲酯为原料,采用自身酯交换法合成了具有生物可降解性能的聚羟基脂肪酸酯.系统考察了离子液体种类、反应温度以及聚合反应时间对反应性能的影响,同时采用红外、核磁、热分析等手段对产物进行表征.研究结果表明:阴离子为CF3SO-3的磺酸功能化离子液体在120℃的低温下催化聚合反应所得聚酯Mw可达10 159,收率82.1%;通过水洗方法可有效去除产物中的离子液体催化剂,从而避免催化剂污染产物.

  1. Conversion of Chlorella oil to biodiesel catalyzed by bronsted acid ionic liquid%离子液体酸催化小球藻油脂转化生物柴油

    Institute of Scientific and Technical Information of China (English)

    尹春华; 徐佩; 何欢聚; 贾璇; 王海鸥; 姜泽毅; 王戈; 张欣欣; 闫海

    2011-01-01

    Suitable conditions for biodiesel synthesis by the transesterification of lipid were studied by using microalgal oil extracted from Chlorella USTB-01 cells as feedstock and bronsted acid ionic liquid([C4MIm]HSO4) as a catalyst.Gas chromatograph-mass spectrometry(GC-MS) was used to determine fatty acids in the microalgal oil and its derived biodiesel.The results indicate that breaking the algae cell wall by grinding can significantly improve the extraction yield of algal lipid using Soxhlet extraction method;among the solvents tested,petroleum ether is the best solvent for the extraction.The major components of Chlorella USTB-01 oil are fatty acids containing C16 and C18.The optimum conditions for synthesizing the microalgae biodiesel are as follows: the molar ratio of methanol to the microalgae oil is 9∶1,the dosage of the catalyst accounts for 8% of the mass of the microalgae oil,the reaction temperature is 150 ℃ and the reaction time is 6 h.Under this condition,the yield of biodiesel can reach 64%.GC-MS analysis shows that biodiesel from Chlorella USTB-01 oil is mainly composed of methyl esters of saturated fatty acid(C16:0) and unsaturated fatty acid(C18:2).The product is feasible to supplement fossil diesel fuel.%以提取得到的小球藻(USTB-01)油脂为原料,采用离子液体酸([C4MIm]HSO4)为催化剂,研究了通过酯交换反应制备生物柴油的适宜条件,并采用气相色谱--质谱联用仪(GC-MS)对小球藻油脂及所制备的生物柴油的脂肪酸组成进行了分析测定.结果表明,研磨破碎藻细胞壁能显著提高索氏法提取藻脂的提取率,石油醚是最适宜的提取溶剂.提取得到的小球藻脂富含C16和C18脂肪酸.藻脂转化生物柴油的适宜条件是:醇油摩尔比为9∶1,催化剂用量占藻脂质量的8%,反应时间为6 h,反应温度为150℃.在此条件下,生物柴油的产率为64%.气质联用仪(GC-MS)分析表明该生物柴油

  2. 酸性功能化双核离子液体催化合成酯的研究%Study of Catalyzed Synthesis of Ester by Acid Functionalized Dacational Ionic Liqiud

    Institute of Scientific and Technical Information of China (English)

    石月丹; 刘春光; 王楠; 徐凛然; 梅楚鹤; 郭珊珊

    2014-01-01

    In this issue,bis-(3-methyl-1-imidazole)butylidene double bisulfate(MTEIMHS) was used as a catalyst to synthetize isoamyl isobutyrate and Isoamyl butyrate. The yield of esterification rate under the influ-ence of the reaction conditions was measured. The results showed that under the optimized conditions of isoamyl isobutyrate :n(isoamylol) ∶ n(isobutyric acid)=1. 2 ∶ 1,catalyst used dosage 2. 0g and 3. 5h,the yield of isoamyl isobutyrate reached 95 . 4%. The results showed that under the optimized conditions of Isoamyl buty-rate:n(isoamylol) ∶ n(butyric acid)=1. 6 ∶ 1,catalyst used dosage 2. 0g and 3h,the yield of isoamyl isobu-tyrate reached 97 . 9%. The reaction mixture was immiscible with MTEIMHS and could be speparated simply by separatory funnel after reaction. The ionic liquid catalyst could be reused for 6 times without noticeable lowering of activity.%以自制的双-(3-甲基-1-咪唑)亚丁基二硫酸氢盐离子液体为催化合成了异丁酸异戊酯和丁酸异戊酯,考察了反应条件对酯化率的影响。结果表明,异丁酸异戊酯最佳的合成条件为:醇酸摩尔量比1.2∶1,催化剂用量为2.0 g,反应时间3.5 h,酯化率达到95.4%。丁酸异戊酯最佳的合成条件为:醇酸摩尔量比1.6∶1,催化剂用量为2.0 g,反应时间3.5 h,酯化率达到97.9%。反应结束后反应混合物与催化剂自动分层,采用分液的方式即可分离出催化剂,简化了分离过程。离子液体重复使用6次,催化效果无明显降低。

  3. Dimethyl carbonate-mediated lipid extraction and lipase-catalyzed in situ transesterification for simultaneous preparation of fatty acid methyl esters and glycerol carbonate from Chlorella sp. KR-1 biomass.

    Science.gov (United States)

    Jo, Yoon Ju; Lee, Ok Kyung; Lee, Eun Yeol

    2014-04-01

    Fatty acid methyl esters (FAMEs) and glycerol carbonate were simultaneously prepared from Chlorella sp. KR-1 containing 40.9% (w/w) lipid using a reactive extraction method with dimethyl carbonate (DMC). DMC was used as lipid extraction agent, acyl acceptor for transesterification of the extracted triglycerides, substrate for glycerol carbonate synthesis from glycerol, and reaction medium for the solvent-free reaction system. For 1g of biomass, 367.31 mg of FAMEs and 16.73 mg of glycerol carbonate were obtained under the optimized conditions: DMC to biomass ratio of 10:1 (v/w), water content of 0.5% (v/v), and Novozyme 435 to biomass ratio of 20% (w/w) at 70°C for 24h. The amount of residual glycerol was only in the range of 1-2.5mg. Compared to conventional method, the cost of FAME production with the proposed technique could be reduced by combining lipid extraction with transesterification and omitting the extraction solvent recovery process. PMID:24583221

  4. Dimethyl carbonate-mediated lipid extraction and lipase-catalyzed in situ transesterification for simultaneous preparation of fatty acid methyl esters and glycerol carbonate from Chlorella sp. KR-1 biomass.

    Science.gov (United States)

    Jo, Yoon Ju; Lee, Ok Kyung; Lee, Eun Yeol

    2014-04-01

    Fatty acid methyl esters (FAMEs) and glycerol carbonate were simultaneously prepared from Chlorella sp. KR-1 containing 40.9% (w/w) lipid using a reactive extraction method with dimethyl carbonate (DMC). DMC was used as lipid extraction agent, acyl acceptor for transesterification of the extracted triglycerides, substrate for glycerol carbonate synthesis from glycerol, and reaction medium for the solvent-free reaction system. For 1g of biomass, 367.31 mg of FAMEs and 16.73 mg of glycerol carbonate were obtained under the optimized conditions: DMC to biomass ratio of 10:1 (v/w), water content of 0.5% (v/v), and Novozyme 435 to biomass ratio of 20% (w/w) at 70°C for 24h. The amount of residual glycerol was only in the range of 1-2.5mg. Compared to conventional method, the cost of FAME production with the proposed technique could be reduced by combining lipid extraction with transesterification and omitting the extraction solvent recovery process.

  5. Zeolite Catalyzed Aldol Condensation Reactions

    Directory of Open Access Journals (Sweden)

    Adedayo I. Inegbenebor

    2015-03-01

    Full Text Available The review is based on the description of zeolite structure, uses, synthesis, and catalytic aldol reaction in aldol condensation. An internal aldolcondensation reaction has been achieved over ZSM-5 zeolite with high silica-alumina ratio at 350oC. It therefore follows that zeolite canfunction as a catalyst in aldol type condensation reactions and that weak acid sites as well as a small number of active sites favor the aldolcondensation reaction of carbonyl compounds. However, the mixed condensation product was found to be favored at temperatures above 300oCand the self-condensation of ethanal to crotonaldehyde was favored at temperatures below 300oC. It has also been suggested that both Brønstedand Lewis acids are involved in aldol reactions with Lewis acid sites the most probable catalytic sites. The zeolite group of minerals has founduse in many chemical and allied industries.

  6. An Alternative Approach to Aldol Reactions: Gold-Catalyzed Formation of Boron Enolates from Alkynes

    OpenAIRE

    Korner, C; Starkov, P.; Sheppard, T. D.

    2010-01-01

    A new method for enolate generation via the gold-catalyzed addition of boronic acids to alkynes is reported. The formation of boron enolates from readily accessible ortho-alkynylbenzeneboronic acids proceeds rapidly with 2 mol % PPh3AuNTf2 at ambient temperature. The enolates undergo aldol reaction with an aldehyde present in the reaction mixture to give cyclic boronate esters, which can be subsequently transformed into phenols, biaryls, or dihydrobenzofurans via oxidation, Suzuki-Miyaura, or...

  7. Papain-Catalyzed Synthesis of Polyglutamate Containing a Nylon Monomer Unit

    OpenAIRE

    Kenjiro Yazawa; Keiji Numata

    2016-01-01

    Peptides have the potential to serve as an alternative for petroleum-based polymers to support a sustainable society. However, they lack thermoplasticity, owing to their strong intermolecular interactions. In contrast, nylon is famous for its thermoplasticity and chemical resistance. Here, we synthesized peptides containing a nylon unit to modify their thermal properties by using papain-catalyzed chemoenzymatic polymerization. We used l-glutamic acid alkyl ester as the amino acid monomer and ...

  8. Synthesis of ethoxy dibenzooxaphosphorin oxides through palladium-catalyzed C(sp2–H activation/C–O formation

    Directory of Open Access Journals (Sweden)

    Seohyun Shin

    2014-05-01

    Full Text Available We report an efficient Pd-catalyzed C(sp2–H activation/C–O bond formation for the synthesis of ethoxy dibenzooxaphosphorin oxides from 2-(arylarylphosphonic acid monoethyl esters under aerobic conditions.

  9. Radiochemical methods for studying lipase-catalyzed interesterification of lipids

    International Nuclear Information System (INIS)

    Reactions involving lipase-catalyzed interesterification of lipids, which are of commendable interest in biotechnology, have been monitored and assayed by radiochemical methods using 14C-labeled substrates. Medium chain (C12 plus C14) triacylglycerols were reacted in the presence of an immobilized lipase from Mucor miehei and hexane at 450C with methyl [1-14C]oleate, [1-14C]oleic acid, [carboxyl-14C]trioleoylglycerol, [1-14C]octadecenyl alcohol, and [U-14C]glycerol, each of known specific activity. The reactions were monitored and the rate of interesterification determined by radio thin layer chromatography from the incorporation of radioactivity into acyl moieties of triacylglycerols (from methyl oleate, oleic acid, and trioleoylglycerol), alkyl moieties of wax esters (from octadecenyl alcohol), and into glycerol backbone of monoacylglycerols and diacylglycerols (from glycerol). (orig.)

  10. Lipozyme TL IM 催化制备零反式脂肪酸人造奶油基料油的研究%Preparation of trans - free fatty acid margarine base oil catalyzed by Lipozyme TL IM

    Institute of Scientific and Technical Information of China (English)

    牟英; 杨宏黎; 杨天奎; 季敏; 修志龙; 黄清吉; 黄仕群

    2014-01-01

    The trans - free fatty acid margarine base oil was prepared by the transesterification of palm stearin and soybean oil with Lipozyme TL IM as catalyst, and the triacylglyceride composition,solid fat content and crystallization rate of the transesterification product were analyzed. The results indicated that the triacylglyceride composition of the transesterification product changed significantly, the solid fat con-tent decreased and the crystallization rate increased markedly. The transesterification product contained most β’ crystal by X - ray diffraction analysis and had a wide plastic range by differential scanning calo-rimetry analysis,which was suitable for preparing margarine.%以棕榈硬脂和大豆油为原料,通过 Lipozyme TL IM 催化酯交换法制备零反式脂肪酸人造奶油基料油。对酯交换产物的甘三酯组成、固体脂肪含量、结晶速度等进行了分析,结果发现酯交换产物甘三酯组成发生了较大变化,固体脂肪含量降低,结晶速度明显提高,X -射线衍射分析表明酯交换产物为β’晶型,差示扫描量热分析表明酯交换产物具有较宽的塑性范围,适合用于制备人造奶油。

  11. Palladium Catalyzed Reduction of Nitrobenzene.

    Science.gov (United States)

    Mangravite, John A.

    1983-01-01

    Compares two palladium (Pd/C) reducing systems to iron/tin-hydrochloric acid (Fe/HCl and Sn/HCl) reductions and suggests an efficient, clean, and inexpensive procedures for the conversion of nitrobenzene to aniline. Includes laboratory procedures used and discussion of typical results obtained. (JN)

  12. 二氧化硅负载高氯酸催化合成香兰素缩1,2-丙二醇%Synthesis of Vanillin 1,2-propylene glycol acetal catalyzed by silica supported perchloric acid

    Institute of Scientific and Technical Information of China (English)

    王宏社

    2013-01-01

    以二氧化硅负载高氯酸(HClO4/SiO2)为催化剂,香兰素和1,2-丙二醇经缩合反应合成香兰素缩1,2-丙二醇.考察了醛醇物质的量比、催化剂用量、反应温度和反应时间对产品收率的影响.实验表明,较佳反应条件为:当香兰素的用量为0.1 mol,1,2-丙二醇的用量为0.16 mol,即n(香兰素)∶n(1,2-丙二醇)=1∶1.6,催化剂用量1.5g,反应温度80℃,反应时间45 min,香兰素缩1,2-丙二醇的收率达87.1%以上.HClO4/SiO2是一种热稳定性好、简单易制、可循环使用的高效非均相催化剂.%Vanillin 1, 2-propylene glycol acetal was synthesized through the condensation of Vanillin with 1, 2-propylene glycol using silica supported perchloric acid (HClO4/SiO2) as a catalyst. The effects of the molar ratio of reactant, the amount of catalyst, reaction temperature and reaction time on the yield of product were discussed. The results showed that the optimized reaction conditions are as follows; the molar ratio of Vanillin (0.1 mol) to 1, 2-propylene glycol (0.16 mol) is 1:1.6; the amount of catalyst is 1.5 g, reaction temperature is 80 ℃ and the reaction time is 45 min. Under the optimum conditions mentioned above, the yield of Vanillin 1, 2-propylene glycol acetal reached more than 87.1%. HClO4/SiO2 as a heterogeneous catalyst has many advantages of high thermal stability, ease of preparation and reusability.

  13. Liquid-Phase Beckmann Rearrangement of Cyelohexanone Oxime Catalyzed by Acidic Ionic Liquid-Zinc Chloride%酸性离子液体-ZnCl2催化环己酮肟液相Beckmann重排反应

    Institute of Scientific and Technical Information of China (English)

    赵江琨; 王荷芳; 王延吉; 赵新强; 张宝泉

    2011-01-01

    在乙腈介质中,由酸性离子液体和ZnCl2组成的催化体系,可以高效地实现对环己酮肟液相Beckmann重排制己内酰胺的反应.反应过程中生成的唯一副产物环己酮,可以通过氨氧化反应生成原料环己酮肟.考察了溶剂种类、反应温度、反应时间、离子液体用量和ZnCl2用量对环己酮肟重排反应性能的影响.确定了适宜的反应条件;HSO3-b-N(CH)3]HSO4 0.5 mmol,ZnCl2 15 mmol,乙腈10 mL,环己酮肟10 mmol,反应温度80℃,反应时间4h.此条件下,环己酮肟转化率达100%,己内酰胺收率为94.9%.利用在线反应红外光谱仪(React IR IC-10)研究了该催化体系下环己酮肟重捧反应机理.%The liquid-phase Beckmann rearrangement of cyclohexanone oxime was effectively realized to prepare e-caprolactam by using acidic ionic liquid-zinc chloride(IL-ZnCl2) catalytic system in acetonitrile. The only by-product, cyclohexanone, could convert back to the raw material, cyclohexanone oxime, by ammoximation reactionThe effects of solvents, reaction temperature, reaction time, the amount of IL, the amount of ZnCl2 on the Beckmann rearrangement were studied. The optimized conditions were:[HSO3-b-N(CH3)3]HSO4 0.5mmol, ZnCl2 15 mmol, acetonitrile 10 mL, cyclohexanone oxime 10 mmol, 80℃, 4 h. The conversation of cyclohexanone oxime can reach 100%, the yield of e-caprolactam can reach 94.9%.The reaction mechanism of cyclohexanone oxime rearrangement over IL-ZnCl2 catalyst was also investigated by React IR IC-10.

  14. Improvement in biodiesel production from soapstock oil by one-stage lipase catalyzed methanolysis

    International Nuclear Information System (INIS)

    Highlights: • Soapstock is a less expensive feedstock reservoir for biodiesel production. • Addition of tert-alcohol can enhance the yield of fatty acid methyl ester significantly. • One-stage lipase catalyzed methanolysis of soapstock oil was successfully developed. • FAME yield of 95.2% was obtained with low lipase loading in a shorter reaction time. - Abstract: A major obstacle in the commercialization of biodiesel is its cost of manufacturing, primarily the raw material cost. In order to decrease the cost of biodiesel, soapstock oil was investigated as the feedstock for biodiesel production. Because the soapstock oil containing large amounts of free fatty acids (FFAs) cannot be effectively converted to biodiesel, complicated two-stage process (esterification followed by transesterification) was generally adopted. In this study, simple one-stage lipase catalyzed methanolysis of soapstock oil was developed via one-pot esterification and transesterification. Water produced by lipase catalyzed esterification of FFAs affected the lipase catalyzed transesterification of glycerides in the soapstock oil severely. Addition of tert-alcohol could overcome this problem and enhance the fatty acid methyl ester (FAME) yield from 42.8% to 76.4%. The FAME yield was further elevated to 95.2% by optimizing the methanol/oil molar ratio, lipase amount, and water absorbent. The developed process enables the simple, efficient, and green production of biodiesel from soapstock oil, providing with a potential industrial application

  15. Metabolism of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline in human hepatocytes: 2-amino-3-methylimidazo[4,5-f]quinoxaline-8-carboxylic acid is a major detoxification pathway catalyzed by cytochrome P450 1A2.

    Science.gov (United States)

    Langouët, S; Welti, D H; Kerriguy, N; Fay, L B; Huynh-Ba, T; Markovic, J; Guengerich, F P; Guillouzo, A; Turesky, R J

    2001-02-01

    Metabolic pathways of the mutagen 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) remain incompletely characterized in humans. In this study, the metabolism of MeIQx was investigated in primary human hepatocytes. Six metabolites were characterized by UV and mass spectroscopy. Novel metabolites were additionally characterized by 1H NMR spectroscopy. The carcinogenic metabolite, 2-(hydroxyamino)-3,8-dimethylimidazo[4,5-f]quinoxaline, which is formed by cytochrome P450 1A2 (P450 1A2), was found to be transformed into the N(2)-glucuronide conjugate, N(2)-(beta-1-glucosiduronyl)-2-(hydroxyamino)-3,8-dimethylimidazo[4,5-f]quinoxaline. The phase II conjugates N(2)-(3,8-dimethylimidazo[4,5-f]quinoxalin-2-yl)sulfamic acid and N(2)-(beta-1-glucosiduronyl)-2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline, as well as the 7-oxo derivatives of MeIQx and N-desmethyl-MeIQx, 2-amino-3,8-dimethyl-6-hydro-7H-imidazo[4,5-f]quinoxalin-7-one (7-oxo-MeIQx), and 2-amino-6-hydro-8-methyl-7H-imidazo[4,5-f]quinoxalin-7-one (N-desmethyl-7-oxo-MeIQx), thought to be formed exclusively by the intestinal flora, were also identified. A novel metabolite was characterized as 2-amino-3-methylimidazo[4,5-f]quinoxaline-8-carboxylic acid (IQx-8-COOH), and it was the predominant metabolite formed in hepatocytes exposed to MeIQx at levels approaching human exposure. IQx-8-COOH formation is catalyzed by P450 1A2. This metabolite is a detoxication product and does not induce umuC gene expression in Salmonella typhimurium strain NM2009. IQx-8-COOH is also the principal oxidation product of MeIQx excreted in human urine [Turesky, R., et al. (1998) Chem. Res. Toxicol. 11, 217-225]. Thus, P450 1A2 is involved in both the metabolic activation and detoxication of this procarcinogen in humans. Analogous metabolism experiments were conducted with hepatocytes of untreated rats and rats pretreated with the P450 inducer 3-methylcholanthrene. Unlike human hepatocytes, the rat cell preparations did not produce IQx-8

  16. Production of Chemoenzymatic Catalyzed Monoepoxide Biolubricant: Optimization and Physicochemical Characteristics

    Directory of Open Access Journals (Sweden)

    Jumat Salimon

    2012-01-01

    Full Text Available Linoleic acid (LA is converted to per-carboxylic acid catalyzed by an immobilized lipase from Candida antarctica (Novozym 435. This per-carboxylic acid is only intermediate and epoxidized itself in good yields and almost without consecutive reactions. Monoepoxide linoleic acid 9(12-10(13-monoepoxy 12(9-octadecanoic acid (MEOA was optimized using D-optimal design. At optimum conditions, higher yield% (82.14 and medium oxirane oxygen content (OOC (4.91% of MEOA were predicted at 15 μL of H2O2, 120 mg of Novozym 435, and 7 h of reaction time. In order to develop better-quality biolubricants, pour point (PP, flash point (FP, viscosity index (VI, and oxidative stability (OT were determined for LA and MEOA. The results showed that MEOA exhibited good low-temperature behavior with PP of −41°C. FP of MEOA increased to 128°C comparing with 115°C of LA. In a similar fashion, VI for LA was 224 generally several hundred centistokes (cSt more viscous than MEOA 130.8. The ability of a substance to resist oxidative degradation is another important property for biolubricants. Therefore, LA and MEOA were screened to measure their OT which was observed at 189 and 168°C, respectively.

  17. Zeolite Catalyzed Aldol Condensation Reactions

    OpenAIRE

    Adedayo I. Inegbenebor; Raphael C. Mordi; Oluwakayode M. Ogunwole

    2015-01-01

    The review is based on the description of zeolite structure, uses, synthesis, and catalytic aldol reaction in aldol condensation. An internal aldolcondensation reaction has been achieved over ZSM-5 zeolite with high silica-alumina ratio at 350oC. It therefore follows that zeolite canfunction as a catalyst in aldol type condensation reactions and that weak acid sites as well as a small number of active sites favor the aldolcondensation reaction of carbonyl compounds. However, the mixed condens...

  18. Dechlorination of carbon tetrachloride by the catalyzed Fe-Cu process

    Institute of Scientific and Technical Information of China (English)

    XU Wen-ying; GAO Ting-yao

    2007-01-01

    The electrochemical reduction characteristics of carbon tetrachloride (CT) were investigated using cyclic voltammetry in this study. In addition, the difference in reduction mechanisms of CT between Master Builders' iron and the catalyzed Fe-Cu process was discussed. The results showed that CT was reduced directly on the surface of copper rather than by atomic hydrogen produced at the cathode in the catalyzed Fe-Cu process. The reduction was realized largely by atomic hydrogen in Master Builders' iron. The entire CT in 350 ml aqueous solution with 320 mg/L was reduced to trichloromethane and dichloromethane in 2.25 h when 100 g of scrap iron with Fe/Cu ratio of 10:1 (w/w) were used. Moreover, the reduction rate slowed with time. CT could be reduced at acidic, neutral and alkaline pH from solution by Fe-Cu bimetallic media, but the mechanisms were different. The degradation rate was not significantly influenced by pH in the catalyzed Fe-Cu process; in Master Builders' iron it clearly increased with decreasing pH. The kinetics of the reductions followed pseudo-first order in both cases. Furthermore, the reductions under acidic conditions proceeded faster than that under the neutral and alkaline conditions. The catalyzed Fe-Cu process was superior to Master Builders' iron in treating CT-containing water and this advantage was particularly noticeable under alkaline conditions. The reduction was investigated in the cathode (Cu) and anode (Fe) compartments respectively, the results showed that the direct reduction pathway played an important role in the reduction by the catalyzed Fe-Cu process. The catalyzed Fe-Cu process is of practical value.

  19. Optimization of lipase-catalyzed synthesis of diglycerol monooleate by response surface methodology

    International Nuclear Information System (INIS)

    The optimization of the lipase-catalyzed esterification of pure diglycerol (3-(2,3-dihydroxypropoxy)propane-1,2-diol) with pure oleic acid to produce pure diglycerol monooleate (E475) which is a non-ionic surfactants, was performed. Six immobilized lipases were tested and the best oleic acid conversion was attained with Novozym 435 from Candida antarctica which was selected to optimize the reaction conditions by response surface methodology (RSM). Well-fitting quadratic polynomial regression model for acid conversion was established with regard to temperature (65 °C–75 °C) and catalyst concentration (mass fraction of 1–5%). The two factors investigated positively affected acid conversion, with catalyst concentration having the greatest effect. The regression equation obtained by central composite design of RSM predicted optimal reaction conditions of 77 °C and 5.8%. Under these optimal conditions the model obtained in this work has been tested in scale-up experiment, and the resulting acid conversion was 93.9% with an accuracy of 97.4%. Within the experimental range studied the results model give good agreement with the experimental data. - Highlights: • Lipase-catalyzed esterification of pure diglycerol with oleic in solvent-free system. • The modeling and optimization of lipase-catalyzed esterification process was successfully performed. • Under optimal conditions, the esterification process was scaled up using a stirred tank reactor

  20. Palladium-Catalyzed Amination of Bromoanthancene

    Institute of Scientific and Technical Information of China (English)

    YU Ming-Xin; CHEN Xiao-Hang; CHENG Chien-Hong

    2003-01-01

    @@ Triarylamines are an important class of compounds, because they have been used as the hole-transport layer in electroluminescent devices. [1] New palladium catalyzed methods to form arylamines have emerged recently from Hartwing and Bucchwald . [2,3] Our group have investigated unusual diboration of allenes catalyzed by palladium complex and organic iodides. [4] Here we will report that arylamines react with bromoanthrancene (or dibromoanthancene) to afford triarylamines in the presence of Ligand-palladium complex. The structures of products were de termined by 1H NMR, 13C NMR, 13C (DEPT), IR and MS (HREI and EI) spectra.

  1. Attractor Explosions and Catalyzed Vacuum Decay

    Energy Technology Data Exchange (ETDEWEB)

    Green, Daniel; Silverstein, Eva; Starr, David

    2006-05-05

    We present a mechanism for catalyzed vacuum bubble production obtained by combining moduli stabilization with a generalized attractor phenomenon in which moduli are sourced by compact objects. This leads straightforwardly to a class of examples in which the Hawking decay process for black holes unveils a bubble of a different vacuum from the ambient one, generalizing the new endpoint for Hawking evaporation discovered recently by Horowitz. Catalyzed vacuum bubble production can occur for both charged and uncharged bodies, including Schwarzschild black holes for which massive particles produced in the Hawking process can trigger vacuum decay. We briefly discuss applications of this process to the population and stability of metastable vacua.

  2. Lipase-catalyzed polyester synthesis – A green polymer chemistry

    Science.gov (United States)

    Kobayashi, Shiro

    2010-01-01

    This article is a short comprehensive review describing in vitro polyester synthesis catalyzed by a hydrolysis enzyme of lipase, most of which has been developed for these two decades. Polyesters are prepared by repeated ester bond-formation reactions; they include two major modes, ring-opening polymerization (ROP) of cyclic monomers such as cyclic esters (lactones) and condensation polymerization via the reaction between a carboxylic acid or its ester group and an alcohol group. Polyester synthesis is, therefore, a reaction in reverse way of in vivo lipase catalysis of ester bond-cleavage with hydrolysis. The lipase-catalyzed polymerizations show very high chemo-, regio-, and enantio-selectivities and involve various advantageous characteristics. Lipase is robust and compatible with other chemical catalysts, which allows novel chemo-enzymatic processes. New syntheses of a variety of functional polyesters and a plausible reaction mechanism of lipase catalysis are mentioned. The polymerization characteristics are of green nature currently demanded for sustainable society, and hence, desirable for conducting ‘green polymer chemistry’. PMID:20431260

  3. Ionic Liquid Catalyzed Electrolyte for Electrochemical Polyaniline Supercapacitors

    Science.gov (United States)

    Inamdar, A. I.; Im, Hyunsik; Jung, Woong; Kim, Hyungsang; Kim, Byungchul; Yu, Kook-Hyun; Kim, Jin-Sang; Hwang, Sung-Min

    2013-05-01

    The effect of different wt.% of ionic liquid "1,6-bis (trimethylammonium-1-yl) hexane tetrafluoroborate" in 0.5 M LiClO4+PC electrolyte on the supercapacitor properties of polyaniline (PANI) thin film are investigated. The PANI film is synthesized using electropolymerization of aniline in the presence of sulfuric acid. The electrochemical properties of the PANI thin film are studied by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy (EIS) measurements. The optimum amount of the ionic liquid is found to be 2 wt.% which provides better ionic conductivity of the electrolyte. The highest specific capacitance of 259 F/g is obtained using the 2 wt.% electrolyte. This capacitance remains at up to 208 F/g (80% capacity retention) after 1000 charge-discharge cycles at a current density of 0.5 mA/g. The PANI film in the 2 wt.% ionic liquid catalyzed 0.5 M LiClO4+PC electrolyte shows small electrochemical resistance, better rate performance and higher cyclability. The increased ionic conductivity of the 2 wt.% ionic liquid catalyzed electrolyte causes a reduction in resistance at the electrode/electrolyte interface, which can be useful in electrochemically-preferred power devices for better applicability.

  4. Horseradish peroxidase-catalyzed polymerization of cardanol in the presence of redox mediators.

    Science.gov (United States)

    Won, Keehoon; Kim, Yong Hwan; An, Eun Suk; Lee, Yeon Soo; Song, Bong Keun

    2004-01-01

    Horseradish peroxidase-catalyzed polymerization of cardanol in aqueous organic solvent was investigated in the presence of a redox mediator. Cardanol is a phenol derivative from a renewable resource mainly having a C15 unsaturated hydrocarbon chain with mostly 1-3 double bonds at a meta position. Unlike soybean peroxidase (SBP), it has been shown that horseradish peroxidase (HRP) is not able to perform oxidative polymerization of phenol derivatives having a bulky meta substituent such as cardanol. For the first time, redox mediators have been applied to enable horseradish peroxidase to polymerize cardanol. Veratryl alcohol, N-ethyl phenothiazine, and phenothiazine-10-propionic acid were tested as a mediator. It is surprising that the horseradish peroxidase-catalyzed polymerization of cardanol took place in the presence of N-ethyl phenothiazine or phenothiazine-10-propionic acid. However, veratryl alcohol showed no effect. FT-IR and GPC analysis of the product revealed that the structure and properties of polycardanol formed by HRP with a mediator were similar to those by SBP. This is the first work to apply a redox mediator to enzyme-catalyzed oxidative polymerization. Our new finding that oxidative polymerization of a poor substrate, which the enzyme is not active with, can take place in the presence of an appropriate mediator will present more opportunities for the application of enzyme-catalyzed polymerization. PMID:14715000

  5. Palladium-catalyzed Reppe carbonylation.

    Science.gov (United States)

    Kiss, G

    2001-11-01

    PdX2L2/L/HA (A = weakly coordinating anion, L = phosphine) complexes are active catalysts in the hydroesterification of alkenes, alkynes, and conjugated dienes. Shell, the only major corporate player in the field, recently developed two very active catalyst systems tailored to the hydroesterification of either alkenes or alkynes. The hydroesterification of propyne with their Pd(OAc)2/PN/HA (PN = (2-pyridyl)diphenylphosphine, HA = strong acid with weakly coordinating anion, like methanesulfonic acid) catalyst has been declared commercially ready. However, despite the significant progress in the activity of Pd-hydroesterification catalysts, further improvements are warranted. Thus, for example, activity maintenance still seems to be an issue. Homogeneous Pd catalysts are prone to a number of deactivation reactions. Activity and stability promoters are often corrosive and add to the complexity of the system, making it less attractive. Nonetheless, the versatility of the process and its tolerance toward the functional groups of substrates should appeal especially to the makers of specialty products. Although hydroesterification yields esters from alkenes, alkynes, and dienes in fewer steps than hydroformylation does, the latter has some advantages at the current state of the art. (1) Hydroformylation catalysts, particularly some recently published phosphine-modified Rh systems, can achieve very high regioselectivity for the linear product that hydroesterification catalysts cannot match yet. By analogy with hydroformylation, bulkier ligands ought to be tested in hydroesterification to increase normal-ester selectivity. (2) Hydroformylation is proven, commercial. Hydroesterification can only replace it if it can provide significant economic incentives. Similar or just marginally better performance could not justify the cost of development of a new technology. (3) Hydroesterification requires pure CO while hydroformylation uses syngas, a mixture of CO and H2. The latter

  6. Palladium catalyzed hydrogenation of bio-oils and organic compounds

    Science.gov (United States)

    Elliott, Douglas C.; Hu, Jianli; Hart, Todd R.; Neuenschwander, Gary G.

    2008-09-16

    The invention provides palladium-catalyzed hydrogenations of bio-oils and certain organic compounds. Experimental results have shown unexpected and superior results for palladium-catalyzed hydrogenations of organic compounds typically found in bio-oils.

  7. An Acid Exchanged Montmorillonite Clay-Catalyzed Synthesis of Polyepichlorhydrin

    OpenAIRE

    Ahmed Yahiaoui; Mohammed Belbachir; Aïcha Hachemaoui

    2003-01-01

    “Maghniteâ€Â, a montmorillonite sheet silicate clay, exchanged with protons to produce “H-Maghnite†is an efficient catalyst for cationic polymerisation of many heterocyclic and vinylic monomers (Belbachir, M. U.S. Patent. 066969.0101 –2001). The structural compositions of both “Maghnite†and “H-Maghnite†have already been determined. Epichlorhydrin monomer, which is polymerizable by a cationic process (Odian,G. La Polymerisation: Principes et Applicatio...

  8. An Acid Exchanged Montmorillonite Clay-Catalyzed Synthesis of Polyepichlorhydrin

    Directory of Open Access Journals (Sweden)

    Ahmed Yahiaoui

    2003-09-01

    Full Text Available “Maghnite”, a montmorillonite sheet silicate clay, exchanged with protons to produce “H-Maghnite” is an efficient catalyst for cationic polymerisation of many heterocyclic and vinylic monomers (Belbachir, M. U.S. Patent. 066969.0101 –2001. The structural compositions of both “Maghnite” and “H-Maghnite” have already been determined. Epichlorhydrin monomer, which is polymerizable by a cationic process (Odian,G. La Polymerisation: Principes et Applications; Ed.Technica: New York, 1994; pp 222-226, was used to elucidate the polymerization cationic character. The polymerization was performed under optimum conditions at 20°C. Experiments revealed that the polymerisation induced by “H-Maghnite” proceeds in bulk. In bulk polymerization, Epichlorhydrin conversion increases with increasing “H-Maghnite” concentration and temperature.

  9. Zeolite-catalyzed additions of aromatic compounds to oleic acid

    Science.gov (United States)

    There is significant research interest in developing new materials from vegetable oils and animal fats. Biobased materials can be more environmentally friendly because they tend to have good biodegradability and are derived from renewable resources. In this talk, efficient approaches for the addit...

  10. 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...

  11. Palladium Catalyzed Allylic C-H Alkylation

    DEFF Research Database (Denmark)

    Engelin, Casper Junker; Fristrup, Peter

    2011-01-01

    The atom-efficiency of one of the most widely used catalytic reactions for forging C-C bonds, the Tsuji-Trost reaction, is limited by the need of preoxidized reagents. This limitation can be overcome by utilization of the recently discovered palladium-catalyzed C-H activation, the allylic C...

  12. Mechanochemical ruthenium-catalyzed olefin metathesis.

    Science.gov (United States)

    Do, Jean-Louis; Mottillo, Cristina; Tan, Davin; Štrukil, Vjekoslav; Friščić, Tomislav

    2015-02-25

    We describe the development of a mechanochemical approach for Ru-catalyzed olefin metathesis, including cross-metathesis and ring-closing metathesis. The method uses commercially available catalysts to achieve high-yielding, rapid, room-temperature metathesis of solid or liquid olefins on a multigram scale using either no or only a catalytic amount of a liquid.

  13. Data, Leadership, and Catalyzing Culture Change

    Science.gov (United States)

    Benson, R. Todd; Trower, Cathy A.

    2012-01-01

    It is crucial to understand today's tenure-track workers so that colleges and universities can continue to attract and retain a large subset of them by understanding and supporting their satisfaction and success at work. In this article, the authors talk about data, leadership, and catalyzing culture change. They discuss data use in the academy…

  14. Pinacol Coupling Reactions Catalyzed by Active Zinc

    Institute of Scientific and Technical Information of China (English)

    Hui ZHAO; Wei DENG; Qing Xiang GUO

    2005-01-01

    Pinacol coupling reactions catalyzed by active zinc revealed high activity and extensive suitability. The efficiency of the reaction was improved apparently owing to decreasing reductive potential of zinc. In addition, the results indicated that the zinc activity has a direct relation to the coupling reactivity compared to untreated zinc or other general active zinc.

  15. Rhodium-catalyzed restructuring of carbon frameworks.

    Science.gov (United States)

    Murakami, Masahiro

    2010-10-01

    Metal-catalyzed reactions involving an elementary step which cleaves a carbon-carbon bond provide unique organic transformations. Restructuring reactions recently developed in our laboratory, through which the carbon framework of a starting substance is restructured into a totally different carbon framework, are discussed, with the possibility of applying such methods to the synthesis of natural products.

  16. Mechanochemical ruthenium-catalyzed olefin metathesis.

    Science.gov (United States)

    Do, Jean-Louis; Mottillo, Cristina; Tan, Davin; Štrukil, Vjekoslav; Friščić, Tomislav

    2015-02-25

    We describe the development of a mechanochemical approach for Ru-catalyzed olefin metathesis, including cross-metathesis and ring-closing metathesis. The method uses commercially available catalysts to achieve high-yielding, rapid, room-temperature metathesis of solid or liquid olefins on a multigram scale using either no or only a catalytic amount of a liquid. PMID:25668586

  17. Zeolite 5A Catalyzed Etherification of Diphenylmethanol

    Science.gov (United States)

    Cooke, Jason; Henderson, Eric J.; Lightbody, Owen C.

    2009-01-01

    An experiment for the synthetic undergraduate laboratory is described in which zeolite 5A catalyzes the room temperature dehydration of diphenylmethanol, (C[subscript 6]H[subscript 5])[subscript 2]CHOH, producing 1,1,1',1'-tetraphenyldimethyl ether, (C[subscript 6]H[subscript 5])[subscript 2]CHOCH(C[subscript 6]H[subscript 5])[subscript 2]. The…

  18. Biodiesel production by enzyme-catalyzed transesterification

    Directory of Open Access Journals (Sweden)

    Stamenković Olivera S.

    2005-01-01

    Full Text Available The principles and kinetics of biodiesel production from vegetable oils using lipase-catalyzed transesterification are reviewed. The most important operating factors affecting the reaction and the yield of alkyl esters, such as: the type and form of lipase, the type of alcohol, the presence of organic solvents, the content of water in the oil, temperature and the presence of glycerol are discussed. In order to estimate the prospects of lipase-catalyzed transesterification for industrial application, the factors which influence the kinetics of chemically-catalysed transesterification are also considered. The advantages of lipase-catalyzed transesterification compared to the chemically-catalysed reaction, are pointed out. The cost of down-processing and ecological problems are significantly reduced by applying lipases. It was also emphasized that lipase-catalysed transesterification should be greatly improved in order to make it commercially applicable. The further optimization of lipase-catalyzed transesterification should include studies on the development of new reactor systems with immobilized biocatalysts and the addition of alcohol in several portions, and the use of extra cellular lipases tolerant to organic solvents, intracellular lipases (i.e. whole microbial cells and genetically-modified microorganisms ("intelligent" yeasts.

  19. Interfacial Behavior of Fatty-Acylated Sericin Prepared by Lipase-Catalyzed Solid-Phase Synthesis

    OpenAIRE

    Ogino, Masato; Tanaka, Rie; 服部, 誠; Yoshida, Tadashi; 横手, よし子; 高橋, 幸資

    2006-01-01

    Fatty-acylated sericin {1:0.7 molar ratio of sericin (Mr 18,700) to oleic acid} was prepared by lipase-catalyzed solid-phase synthesis in n-hexane containing oleic acid to endow sericin with interfacial properties. Acylation with oleic acid was confirmed by 1H-NMR. The fatty-acylated sericin exhibited superior emulsifying activity index and emulsion stability in the presence of 0?0.5 M NaCl, in a temperature range of 30?80 °C and pH range of 2?7, as compared with the control sericin. The fatt...

  20. Continuous-Flow Processes in Heterogeneously Catalyzed Transformations of Biomass Derivatives into Fuels and Chemicals

    Directory of Open Access Journals (Sweden)

    Antonio A. Romero

    2012-07-01

    Full Text Available Continuous flow chemical processes offer several advantages as compared to batch chemistries. These are particularly relevant in the case of heterogeneously catalyzed transformations of biomass-derived platform molecules into valuable chemicals and fuels. This work is aimed to provide an overview of key continuous flow processes developed to date dealing with a series of transformations of platform chemicals including alcohols, furanics, organic acids and polyols using a wide range of heterogeneous catalysts based on supported metals, solid acids and bifunctional (metal + acidic materials.

  1. Condensation reaction of formaldehyde and methyl formate catalyzed by a composite catalyst system

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The condensation reaction of formaldehyde and methyl formate to form methyl glycolate and methyl methoxy acetate catalyzed by p-toluenesulfonic acid and different Lewis acid compounds has been investigated. The composite catalytic system consisting of p-toluenesulfonic acid and NiX2 (X = Cl, Br, I), especially NiI2, exhibited a high catalytic performance for the condensation reaction, the total yield of MG and MMAc was up to 72.37%.(C) 2007 Gong Ying Wang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

  2. Kinetics of aggregation growth with competition between catalyzed birth and catalyzed death

    Institute of Scientific and Technical Information of China (English)

    Wang Hai-Feng; Lin Zhen-Quan; Gao Yan

    2008-01-01

    An aggregation growth model of three species A, B and C with the competition between catalyzed birth and catalyzed death is proposed. Irreversible aggregation occurs between any two aggregates of the like species with the constant rate kernels In(n = 1, 2, 3). Meanwhile, a monomer birth of an A species aggregate of size k occurs under the catalysis of a B species aggregate of size j with the catalyzed birth rate kernel K(k,j) = Kkjv, and a monomer death of an A species aggregate of size k occurs under the catalysis of a C species aggregate of size j with the catalyzed death rate kernel L(k, j) = Lkjv, where v is a parameter reflecting the dependence of the catalysis reaction rates of birth and death on the size of catalyst aggregate. The kinetic evolution behaviours of the three species are investigated by the rate equation approach based on the mean-field theory. The form of the aggregate size distribution of A species ak(t) is found to be dependent crucially on the competition between the catalyzed birth and death of A species, as well as the irreversible aggregation processes of the three species: (1) In the v < 0 case, the irreversible aggregation dominates the process, and ak(t) satisfies the conventional scaling form; (2) In the v ≥ 0 case, the competition between the catalyzed birth and death dominates the process. When the catalyzed birth controls the process, ak(t) takes the conventional or generalized scaling form. While the catalyzed death controls the process, the scaling description of the aggregate size distribution breaks down completely.

  3. Biofuel-Promoted Polychlorinated Dibenzodioxin/furan Formation in an Iron-Catalyzed Diesel Particle Filter.

    Science.gov (United States)

    Heeb, Norbert V; Rey, Maria Dolores; Zennegg, Markus; Haag, Regula; Wichser, Adrian; Schmid, Peter; Seiler, Cornelia; Honegger, Peter; Zeyer, Kerstin; Mohn, Joachim; Bürki, Samuel; Zimmerli, Yan; Czerwinski, Jan; Mayer, Andreas

    2015-08-01

    Iron-catalyzed diesel particle filters (DPFs) are widely used for particle abatement. Active catalyst particles, so-called fuel-borne catalysts (FBCs), are formed in situ, in the engine, when combusting precursors, which were premixed with the fuel. The obtained iron oxide particles catalyze soot oxidation in filters. Iron-catalyzed DPFs are considered as safe with respect to their potential to form polychlorinated dibenzodioxins/furans (PCDD/Fs). We reported that a bimetallic potassium/iron FBC supported an intense PCDD/F formation in a DPF. Here, we discuss the impact of fatty acid methyl ester (FAME) biofuel on PCDD/F emissions. The iron-catalyzed DPF indeed supported a PCDD/F formation with biofuel but remained inactive with petroleum-derived diesel fuel. PCDD/F emissions (I-TEQ) increased 23-fold when comparing biofuel and diesel data. Emissions of 2,3,7,8-TCDD, the most toxic congener [toxicity equivalence factor (TEF) = 1.0], increased 90-fold, and those of 2,3,7,8-TCDF (TEF = 0.1) increased 170-fold. Congener patterns also changed, indicating a preferential formation of tetra- and penta-chlorodibenzofurans. Thus, an inactive iron-catalyzed DPF becomes active, supporting a PCDD/F formation, when operated with biofuel containing impurities of potassium. Alkali metals are inherent constituents of biofuels. According to the current European Union (EU) legislation, levels of 5 μg/g are accepted. We conclude that risks for a secondary PCDD/F formation in iron-catalyzed DPFs increase when combusting potassium-containing biofuels.

  4. Efficient Hydration of Olefins Catalyzed by Wool-Supported Palladium Complex

    Institute of Scientific and Technical Information of China (English)

    Dan-Ni SUI; Si-Qian WANG; Xin WANG; Mei-Yu HUANG; Ying-Yan JIANG

    2005-01-01

    @@ 1Introduction The hydration of olefins is one of the most important prxesses for the production of alcohols[1]. Both transition metal complexes[2] and enzymes[3] have been reported to catalyze the hydration of alkenes, but their catalysts are usually tither unstable or difficult to prepare, expensive and sometimes can not be easily recovered.In our previous papers, some natural biopolymer-metal complexes[4-6] have been used as effective catalysts in hydration to overcome above disadvantages. Recently, wool-Palladium complex(Wool-Pd) has been prepared and found to be able to effficiently catalyze the hydration of olefins to alcohols, such as cinnamyl alcohol(1a) to 1-phenyl-1,3-propanediol(1b), acrylic acid(2a) to lactic acid(2b), 4-vinyl pyridine(3a) to α-methyl-4-pyridinemethanol (3b) and acrylamide(4a) to 1-hydroxyethylamide(4b) respectively in high yields under mild conditions. See scheme 1.

  5. Kinetics of non-catalyzed hydrolysis of tannin in high temperature liquid water

    Institute of Scientific and Technical Information of China (English)

    Li-li LU; Xiu-yang LU; Nan MA

    2008-01-01

    High temperature liquid water (HTLW) has drawn increasing attention as an environmentally benign medium for organic chemical reactions,especially acid-/base-catalyzed reactions.Non-catalyzed hydrolyses of gallotannin and tara tannin in HTLW for the simultaneous preparation of gallic acid (GA) and pyrogallol (PY) are under investigation in our laboratory.In this study,the hydrolysis kinetics of gallotannin and tara tannin were determined.The reaction is indicated to be a typical consecutive first-order one in which GA has formed as a main intermediate and PY as the final product.Selective decomposition of tannin in HTLW was proved to be possible by adjusting reaction temperature and time.The present results provide an important basic data and reference for the green preparation of GA and PY.

  6. The Esterification of Salicylic Acid Catalyzed by Solid Super Acid SO4^2--La2O3-TiO2%SO4^2--La2O3-TiO2固体超强酸催化水杨酸的酯化反应

    Institute of Scientific and Technical Information of China (English)

    张霞

    2012-01-01

    首次以SO4^2--La2O3-TiO2为非均相催化剂,以水杨酸为原料,合成了水杨酸甲酯和乙酰水杨酸。考察了影响反应的条件,获得优化实验条件:n水杨酸:n甲醇为1:12,催化剂用量40g/mol酸,反应5h时,水杨酸甲酯的收率可达86%;n水杨酸:n乙酸酐为1:4,催化剂用量6g/mol酸时,乙酰水杨酸的收率可达87%,同时催化剂回收再生容易,重复使用4次催化活性无明显降低,是一种环境友好的催化剂。%Solid super acid SO4^2--La2O3-TiO2 is first applied to esteriflcation of Salicylic Acid with methyl alcohol and acetic anbyolride. Reaction eanditions are studied. The optimum condition is in the following: molar ratio of Salicylic Acid to methyl alcohol being 1:12 ,the quantity of catalyst being 40g/mol acid, and the reaction time being 5h, the yield of Methyl Salicylate reaching over 86% ; molar ratio of Salicylic Acid to acetic anbyolride being 1:4, the quantity of catalyst being 6g/mol acid, the yield of Aacetyl Salicylic Acid could reaching over 86%. The catalyst could be easily re - cycled at least four times without the obvious loss of catalytic activity. It is an envionmentally friendly catalyst.

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

    Science.gov (United States)

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

    2016-05-11

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

  8. Heterogeneous Palladium Chloride Catalyzed Ligand-free Suzuki-Miyaura Coupling Reactions at Ambient Temperature

    Institute of Scientific and Technical Information of China (English)

    WANG Min; WANG Lei

    2008-01-01

    A mild and efficient ligand-free Suzuki-Miyaura coupling reaction catalyzed by heterogeneous palladium chloride was developed at room temperature in a short reaction time under air atmosphere.Various phenyl iodides,bromides and activated chlorides were coupled with sodium tetraphenylborate or phenylboronic acids efficiently to afford the corresponding cross-coupled products in good to excellent yields.Furthermore,the catalyst could be recycled up to four times without loss of its activity.

  9. Lipase-catalyzed highly enantioselective kinetic resolution of boron-containing chiral alcohols.

    Science.gov (United States)

    Andrade, Leandro H; Barcellos, Thiago

    2009-07-16

    The first application of enzymes as catalysts to obtain optically pure boron compounds is described. The kinetic resolution of boron-containing chiral alcohols via enantioselective transesterification catalyzed by lipases was studied. Aromatic, allylic, and aliphatic secondary alcohols containing a boronate ester or boronic acid group were resolved by lipase from Candida antartica (CALB), and excellent E values (E > 200) and high enantiomeric excesses (up to >99%) of both remaining substrates and acetylated product were obtained.

  10. Parameters critical to muon-catalyzed fusion

    International Nuclear Information System (INIS)

    We have demonstrated that muon catalysis cycling rates increase rapidly with increasing deuterium-tritium gas temperatures and densities. Furthermore, muon-capture losses are significantly smaller than predicted before the experiments. There remains a significant gap between observation and theoretical expectation for the muon-alpha sticking probability in dense d-t mixtures. We have been able to achieve muon-catalyzed yields of 150 fusion/muon (average). While the fusion energy thereby released significantly exceeds expectations, enhancements by nearly a factor of twenty would be needed to realize energy applications for a pure (non-hybrid) muon-catalyzed fusion reactor. The process could be useful in tritium-breeding schemes. We have also explored a new form of cold nuclear fusion which occurs when hydrogen isotopes are loaded into metals. 22 refs., 10 figs

  11. Palladium-Catalyzed Environmentally Benign Acylation.

    Science.gov (United States)

    Suchand, Basuli; Satyanarayana, Gedu

    2016-08-01

    Recent trends in research have gained an orientation toward developing efficient strategies using innocuous reagents. The earlier reported transition-metal-catalyzed carbonylations involved either toxic carbon monoxide (CO) gas as carbonylating agent or functional-group-assisted ortho sp(2) C-H activation (i.e., ortho acylation) or carbonylation by activation of the carbonyl group (i.e., via the formation of enamines). Contradicting these methods, here we describe an environmentally benign process, [Pd]-catalyzed direct carbonylation starting from simple and commercially available iodo arenes and aldehydes, for the synthesis of a wide variety of ketones. Moreover, this method comprises direct coupling of iodoarenes with aldehydes without activation of the carbonyl and also without directing group assistance. Significantly, the strategy was successfully applied to the synthesis n-butylphthalide and pitofenone. PMID:27377566

  12. Biorefining: heterogeneously catalyzed reactions of carbohydrates for the production of furfural and hydroxymethylfurfural.

    Science.gov (United States)

    Karinen, Reetta; Vilonen, Kati; Niemelä, Marita

    2011-08-22

    Furfurals are important intermediates in the chemical industry. They are typically produced by homogeneous catalysis in aqueous solutions. However, heterogeneously catalyzed processes would be beneficial in view of the principles of green chemistry: the elimination of homogeneous mineral acids makes the reaction mixtures less corrosive, produces less waste, and facilitates easy separation and recovery of the catalyst. Finding an active and stable water-tolerant solid acid catalyst still poses a challenge for the production of furfural (furan-2-carbaldehyde) and 5-(hydroxymethyl)-2-furaldehyde (HMF). Furfural is produced in the dehydration of xylose, and HMF is formed from glucose and fructose in the presence of an acidic catalyst. Bases are not active in dehydration reaction but do catalyze the isomerization of monosaccharides, which is favorable when using glucose as a raw material. In addition to the desired dehydration of monosaccharides, many undesired side reactions take place, reducing the selectivity and deactivating the catalyst. In addition, the catalyst properties play an important role in the selectivity. In this Review, catalytic conversion approaches are summarized, focusing on the heterogeneously catalyzed formation of furfural. The attractiveness of catalytic concepts is evaluated, keeping in mind productivity, sustainability, and environmental footprint. PMID:21728248

  13. A review on biodiesel production using catalyzed transesterification

    Energy Technology Data Exchange (ETDEWEB)

    Leung, Dennis Y.C.; Wu, Xuan; Leung, M.K.H. [Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong (China)

    2010-04-15

    Biodiesel is a low-emissions diesel substitute fuel made from renewable resources and waste lipid. The most common way to produce biodiesel is through transesterification, especially alkali-catalyzed transesterification. When the raw materials (oils or fats) have a high percentage of free fatty acids or water, the alkali catalyst will react with the free fatty acids to form soaps. The water can hydrolyze the triglycerides into diglycerides and form more free fatty acids. Both of the above reactions are undesirable and reduce the yield of the biodiesel product. In this situation, the acidic materials should be pre-treated to inhibit the saponification reaction. This paper reviews the different approaches of reducing free fatty acids in the raw oil and refinement of crude biodiesel that are adopted in the industry. The main factors affecting the yield of biodiesel, i.e. alcohol quantity, reaction time, reaction temperature and catalyst concentration, are discussed. This paper also described other new processes of biodiesel production. For instance, the Biox co-solvent process converts triglycerides to esters through the selection of inert co-solvents that generates a one-phase oil-rich system. The non-catalytic supercritical methanol process is advantageous in terms of shorter reaction time and lesser purification steps but requires high temperature and pressure. For the in situ biodiesel process, the oilseeds are treated directly with methanol in which the catalyst has been preciously dissolved at ambient temperatures and pressure to perform the transesterification of oils in the oilseeds. This process, however, cannot handle waste cooking oils and animal fats. (author)

  14. Copper Catalyzed Oceanic Methyl Halide Production

    OpenAIRE

    Robin Kim, Jae Yun; Rhew, Robert

    2014-01-01

    Methyl halides are found in all of Earth’s biomes, produced naturally or through manmade means. Their presence in the atmosphere is problematic, as they catalyze depletion of stratospheric ozone. To understand the full environmental impact of these compounds, it is important to identify their chemical cycling processes. Iron increases methyl halide production in soils and oceans, yet copper’s influence remains unknown despite its similar chemical oxidation properties to iron. I experimentally...

  15. Palladium-Catalyzed Cross-Coupling Reactions of Perfluoro Organic Compounds

    Directory of Open Access Journals (Sweden)

    Masato Ohashi

    2014-09-01

    Full Text Available In this review, we summarize our recent development of palladium(0-catalyzed cross-coupling reactions of perfluoro organic compounds with organometallic reagents. The oxidative addition of a C–F bond of tetrafluoroethylene (TFE to palladium(0 was promoted by the addition of lithium iodide, affording a trifluorovinyl palladium(II iodide. Based on this finding, the first palladium-catalyzed cross-coupling reaction of TFE with diarylzinc was developed in the presence of lithium iodide, affording α,β,β-trifluorostyrene derivatives in excellent yield. This coupling reaction was expanded to the novel Pd(0/PR3-catalyzed cross-coupling reaction of TFE with arylboronates. In this reaction, the trifluorovinyl palladium(II fluoride was a key reaction intermediate that required neither an extraneous base to enhance the reactivity of organoboronates nor a Lewis acid additive to promote the oxidative addition of a C–F bond. In addition, our strategy utilizing the synergetic effect of Pd(0 and lithium iodide could be applied to the C–F bond cleavage of unreactive hexafluorobenzene (C6F6, leading to the first Pd(0-catalyzed cross-coupling reaction of C6F6 with diarylzinc compounds.

  16. Formylation of Alcohol with Formic Acid under Solvent-Free and Neutral Conditions Catalyzed by Free I2 or I2 Generated in Situ from Fe(NO3)3·9H2O/NaI%无溶剂中性条件下分子I2或Fe(NO3)3·9H2O/NaI原位生成的I2催化醇与甲酸甲酰化反应

    Institute of Scientific and Technical Information of China (English)

    Rostami AMIN; Khazaei ARDESHIR; Alavi-Nik HEIDAR ALI; Toodeh-Roosta ZAHRA

    2011-01-01

    Different alcohols were formylated by formic acid under solvent-free conditions in the presence of iodine as the catalyst with good-to-high yields at room temperature.I2 generated in situ from Fe(NO3)3·9H2O/NaI also catalyzed the formylation of the alcohols under solvent-free conditions.This gives a green and efficient reaction at room temperature,in which the use of toxic and corrosive molecular I2 is avoided.

  17. A free-standing condensation enzyme catalyzing ester bond formation in C-1027 biosynthesis.

    Science.gov (United States)

    Lin, Shuangjun; Van Lanen, Steven G; Shen, Ben

    2009-03-17

    Nonribosomal peptide synthetases (NRPSs) catalyze the biosynthesis of many biologically active peptides and typically are modular, with each extension module minimally consisting of a condensation, an adenylation, and a peptidyl carrier protein domain responsible for incorporation of an amino acid into the growing peptide chain. C-1027 is a chromoprotein antitumor antibiotic whose enediyne chromophore consists of an enediyne core, a deoxy aminosugar, a benzoxazolinate, and a beta-amino acid moiety. Bioinformatics analysis suggested that the activation and incorporation of the beta-amino acid moiety into C-1027 follows an NRPS mechanism whereby biosynthetic intermediates are tethered to the peptidyl carrier protein SgcC2. Here, we report the biochemical characterization of SgcC5, an NRPS condensation enzyme that catalyzes ester bond formation between the SgcC2-tethered (S)-3-chloro-5-hydroxy-beta-tyrosine and (R)-1-phenyl-1,2-ethanediol, a mimic of the enediyne core. SgcC5 uses (S)-3-chloro-5-hydroxy-beta-tyrosyl-SgcC2 as the donor substrate and exhibits regiospecificity for the C-2 hydroxyl group of the enediyne core mimic as the acceptor substrate. Remarkably, SgcC5 is also capable of catalyzing amide bond formation, albeit with significantly reduced efficiency, between (S)-3-chloro-5-hydroxy-beta-tyrosyl-(S)-SgcC2 and (R)-2-amino-1-phenyl-1-ethanol, an alternative enediyne core mimic bearing an amine at its C-2 position. Thus, SgcC5 is capable of catalyzing both ester and amide bond formation, providing an evolutionary link between amide- and ester-forming condensation enzymes. PMID:19246381

  18. Gold-catalyzed direct alkynylation of tryptophan in peptides using TIPS-EBX

    Science.gov (United States)

    Tolnai, Gergely L; Brand, Jonathan P

    2016-01-01

    Summary The selective functionalization of peptides containing only natural amino acids is important for the modification of biomolecules. In particular, the installation of an alkyne as a useful handle for bioconjugation is highly attractive, but the use of a carbon linker is usually required. Herein, we report the gold-catalyzed direct alkynylation of tryptophan in peptides using the hypervalent iodine reagent TIPS-EBX (1-[(triisopropylsilyl)ethynyl]-1,2-benziodoxol-3(1H)-one). The reaction proceeded in 50–78% yield under mild conditions and could be applied to peptides containing other nucleophilic and aromatic amino acids, such as serine, phenylalanine or tyrosine. PMID:27340466

  19. Ruthenium(III) catalyzed oxidation of sugar alcohols by dichloroisocyanuric acid—A kinetic study

    Science.gov (United States)

    Lakshman Kumar, Y.; Venkata Nadh, R.; Radhakrishnamurti, P. S.

    2016-02-01

    Kinetics of ruthenium(III) catalyzed oxidation of biologically important sugar alcohols (myo-inositol, D-sorbitol, and D-mannitol) by dichloroisocyanuric acid was carried out in aqueous acetic acid—perchloric medium. The reactions were found to be first order in case of oxidant and ruthenium(III). Zero order was observed with the concentrations of sorbitol and mannitol whereas, a positive fractional order was found in the case of inositol concentration. An inverse fractional order was observed with perchloric acid in oxidation of three substrates. Arrhenius parameters were calculated and a plausible mechanism was proposed.

  20. Lipase-catalyzed modification of lard to produce human milk fat substitutes

    DEFF Research Database (Denmark)

    Yang, Tiankui; Xu, Xuebing; He, C.;

    2003-01-01

    The objective of the present work was to modify lard into human milk fat substitutes (HMFS) by Lipozyme RM IM-catalyzed acidolysis. Lard and soybean fatty acids were esterified in a solvent-free system. The reaction substrates for HMFS production were specially chosen to mimic human milk fats.......7%, and time 1.0 h), were similar to the fat in Chinese mothers' milk. The results showed that it was possible to produce human milk fat substitutes from lard through enzymatic acidolysis with soybean fatty acids....

  1. Temperature dependence of turnover in a Sc(OTf)3-catalyzed intramolecular Schmidt reaction

    Science.gov (United States)

    Fehl, Charlie; Hirt, Erin E.; Li, Sze-Wan; Aubé, Jeffrey

    2015-01-01

    The intramolecular Schmidt reaction of ketones and tethered azides is an efficient method for the generation of amides and lactams. This reaction is catalyzed by Lewis acids, which tightly bind the strongly basic amide product and result in product inhibition. We report herein conditions to achieve a catalytic Schmidt reaction using substoichiometric amounts of the heat-stable Lewis acid Sc(OTf)3. This species was shown to effectively release products of the Schmidt reaction in a temperature-dependent fashion. Thus, heat was able to promote catalyst turnover. A brief substrate scope was conducted using these conditions. PMID:26085693

  2. Kinetics of the Esterification Reaction Catalyzed by Lipase in W/O Microemulsions of Alkyl Polyglucoside

    Institute of Scientific and Technical Information of China (English)

    Jin Ling CHAI; Shou Qing WANG; Gan Zuo LI; Qing XU; Yan Hong GAO

    2004-01-01

    A novel kinetic mechanism of esterification reaction of 1-hexanoic acid with 1-butanol, catalyzed by lipase, was studied in water-in-oil microemulsions. The microemulsions were formed by alkyl polyglucoside C10G1.54 /1-butanol / cyclohexane/phosphate buffer solution. The result shows that when the ratio of mol concentration of 1-butanol to 1-hexanoic acid is about 3.0, the initial rate V0 get the maximum values. This phenomenon was explained by the modified fishlike phase diagrams.

  3. Importance of Vanadium-Catalyzed Oxidation of SO2to SO3in Two-Stroke Marine Diesel Engines

    DEFF Research Database (Denmark)

    Colom, Juan M.; Alzueta, María U.; Christensen, Jakob Munkholt;

    2016-01-01

    Low-speed marine diesel engines are mostly operated on heavy fuel oils, which have a high content of sulfur andash, including trace amounts of vanadium, nickel, and aluminum. In particular, vanadium oxides could catalyze in-cylinderoxidation of SO2 to SO3, promoting the formation of sulfuric acid...... of the catalyticspecies within the engine. Experiments with different particle compositions (vanadium/sodium ratio) and temperatures (300−800 °C) show that both the temperature and sodium content have a major impact on the oxidation rate. Kinetic parameters forthe catalyzed reaction are determined, and the proposed...

  4. Calcium-Catalyzed, Dehydrative, Ring-Opening Cyclizations of Cyclopropyl Carbinols Derived from Donor-Acceptor Cyclopropanes.

    Science.gov (United States)

    Sandridge, Matthew J; France, Stefan

    2016-09-01

    A calcium-catalyzed, dehydrative, ring-opening cyclization of (hetero)aryl cyclopropyl carbinols is reported. The cyclopropyl carbinols are prepared directly from the corresponding donor-acceptor (D-A) cyclopropanes. The calcium catalyst catalyzes the formation of putative (hetero)aryl cyclopropyl carbinyl cations that undergo ring-opening to allylcarbinyl cations. Subsequent intramolecular Friedel-Crafts reaction affords (hetero)aryl-fused cyclohexa-1,3-dienes in up to 97% yield. This approach represents the first example of catalysis for this intramolecular, dehydrative ring-opening cyclization and outperforms the previous reports using stoichiometric Lewis acids. PMID:27517711

  5. Mechanism of maltal hydration catalyzed by β-amylase: Role of protein structure in controlling the steric outcome of reactions catalyzed by a glycosylase

    International Nuclear Information System (INIS)

    Crystalline (monomeric) soybean and (tetrameric) sweet potato β-amylase were shown to catalyze the cis hydration of maltal (α-D-glucopyranosyl-2-deoxy-D-arabino-hex-1-enitol) to form β-2-deoxymaltose. As reported earlier with the sweet potato enzyme, maltal hydration in D2O by soybean β-amylase was found to exhibit an unusually large solvent deuterium kinetic isotope effect (VH/VD=6.5), a reaction rate linearly dependent on the mole fraction of deuterium, and 2-deoxy-[2(a)-2H]maltose as product. These results indicate (for each β-amylase) that protonation is the rate-limiting step in a reaction involving a nearly symmetric one-proton transition state and that maltal is specifically protonated from above the double bond. That maltal undergoes cis hydration provides evidence in support of a general-acid-catalyzed, carbonium ion mediated reaction. Of fundamental significance is that β-amylase protonates maltal from a direction opposite that assumed for protonating strach, yet creates products of the same anomeric configuration from both. Such stereochemical dichotomy argues for the overriding role of protein structures is dictating the steric outcome of reactions catalyzed by a glycosylase, by limiting the approach and orientation of water or other acceptors to the reaction center

  6. Papain-Catalyzed Synthesis of Polyglutamate Containing a Nylon Monomer Unit

    Directory of Open Access Journals (Sweden)

    Kenjiro Yazawa

    2016-05-01

    Full Text Available Peptides have the potential to serve as an alternative for petroleum-based polymers to support a sustainable society. However, they lack thermoplasticity, owing to their strong intermolecular interactions. In contrast, nylon is famous for its thermoplasticity and chemical resistance. Here, we synthesized peptides containing a nylon unit to modify their thermal properties by using papain-catalyzed chemoenzymatic polymerization. We used l-glutamic acid alkyl ester as the amino acid monomer and nylon 1, 3, 4, and 6 alkyl esters as the nylon unit. Papain catalyzed the copolymerization of glutamic acid with nylon 3, 4, and 6 alkyl esters, whereas the nylon 1 unit could not be copolymerized. Other proteases used in this study, namely, bromelain, proteinase K, and Candida antarctica lipase (CALB, were not able to copolymerize with any nylon units. The broad substrate specificity of papain enabled the copolymerization of l-glutamic acid with a nylon unit. The peptides with nylon units demonstrated different thermal profiles from that of oligo(l-glutamic acid. Therefore, the resultant peptides with various nylon units are expected to form fewer intermolecular hydrogen bonds, thus altering their thermal properties. This finding is expected to broaden the applications of peptide materials and chemoenzymatic polymerization.

  7. Ligand Intermediates in Metal-Catalyzed Reactions

    Energy Technology Data Exchange (ETDEWEB)

    Gladysz, John A.

    1999-07-31

    The longest-running goal of this project has been the synthesis, isolation, and physical chemical characterization of homogeneous transition metal complexes containing ligand types believed to be intermediates in the metal-catalyzed conversion of CO/H{sub 2}, CO{sub 2}, CH{sub 4}, and similar raw materials to organic fuels, feedstocks, etc. In the current project period, complexes that contain unusual new types of C{sub x}(carbide) and C{sub x}O{sub y} (carbon oxide) ligands have been emphasized. A new program in homogeneous fluorous phase catalysis has been launched as described in the final report.

  8. Autoinduced catalysis and inverse equilibrium isotope effect in the frustrated Lewis pair catalyzed hydrogenation of imines.

    Science.gov (United States)

    Tussing, Sebastian; Greb, Lutz; Tamke, Sergej; Schirmer, Birgitta; Muhle-Goll, Claudia; Luy, Burkhard; Paradies, Jan

    2015-05-26

    The frustrated Lewis pair (FLP)-catalyzed hydrogenation and deuteration of N-benzylidene-tert-butylamine (2) was kinetically investigated by using the three boranes B(C6F5)3 (1), B(2,4,6-F3-C6H2)3 (4), and B(2,6-F2-C6H3)3 (5) and the free activation energies for the H2 activation by FLP were determined. Reactions catalyzed by the weaker Lewis acids 4 and 5 displayed autoinductive catalysis arising from a higher free activation energy (2 kcal mol(-1)) for the H2 activation by the imine compared to the amine. Surprisingly, the imine reduction using D2 proceeded with higher rates. This phenomenon is unprecedented for FLP and resulted from a primary inverse equilibrium isotope effect.

  9. Palladium-Catalyzed Arylation of Fluoroalkylamines

    Science.gov (United States)

    Brusoe, Andrew T.; Hartwig, John F.

    2015-01-01

    We report the synthesis of fluorinated anilines by palladium-catalyzed coupling of fluoroalkylamines with aryl bromides and aryl chlorides. The products of these reactions are valuable because anilines typically require the presence of an electron-withdrawing substituent on nitrogen to suppress aerobic or metabolic oxidation, and the fluoroalkyl groups have steric properties and polarity distinct from those of more common electron-withdrawing amide and sulfonamide units. The fluoroalkylaniline products are unstable under typical conditions for C–N coupling reactions (heat and strong base). However, the reactions conducted with the weaker base KOPh, which has rarely been used in cross-coupling to form C–N bonds, occurred in high yield in the presence of a catalyst derived from commercially available AdBippyPhos and [Pd(allyl)Cl]2. Under these conditions, the reactions occur with low catalyst loadings (<0.50 mol % for most substrates) and tolerate the presence of various functional groups that react with the strong bases that are typically used in Pd-catalyzed C–N cross-coupling reactions of aryl halides. The resting state of the catalyst is the phenoxide complex, (BippyPhosPd(Ar)OPh); due to the electron-withdrawing property of the fluoroalkyl substituent, the turnover-limiting step of the reaction is reductive elimination to form the C–N bond. PMID:26065341

  10. Process Technology for Immobilized LipaseProcess Technology for Immobilized Lipase-catalyzed

    DEFF Research Database (Denmark)

    Xu, Yuan

    -down experimental work is described in this thesis. The methodology uses economic targets to test options characterized via a set of tools. In order to validate the methodology, two processes based on immobilized lipase-catalysis have been studied: transesterification and esterification of vegetable oils...... for the production of biodiesel. The two processes are focused on the conversion of the two main components of vegetable oil materials, glyceride esters and free fatty acids respectively, into fatty acid alkyl esters. Although biodiesel is conventionally prepared via chemical-catalyzed transesterification...... of vegetable oils with methanol to produce fatty acid methyl esters (FAME), this work has been focused on the production of fatty acid ethyl esters (FAEE) with bioethanol due to the expected improved sustainability of this type of biodiesel. A key reaction characteristic of the immobilized lipase...

  11. Microbial transformations of isocupressic acid.

    Science.gov (United States)

    Lin, S J; Rosazza, J P

    1998-07-01

    Microbial transformations of the labdane-diterpene isocupressic acid (1) with different microorganisms yielded several oxygenated metabolites that were isolated and characterized by MS and NMR spectroscopic analyses. Nocardia aurantia (ATCC 12674) catalyzed the cleavage of the 13,14-double bond to yield a new nor-labdane metabolite, 2. Cunninghamella elegans (-) (NRRL 1393) gave 7beta-hydroxyisocupressic acid (3) and labda-7,13(E)-diene-6beta,15, 17-triol-19-oic acid (4), and Mucor mucedo (ATCC 20094) gave 2alpha-hydroxyisocupressic acid (5) and labda-8(17),14-diene-2alpha, 13-diol-19-oic acid (6).

  12. Common Inorganic Salts Catalyze the Transformations of Organic Compounds in Atmospheric Aerosols

    Science.gov (United States)

    Noziere, B.; Dziedzic, P.; Cordova, A.

    2008-12-01

    This presentation reports the discovery that inorganic salts that are ubiquitous in atmospheric aerosols are efficient catalysts for the transformations of organic compounds in these aerosols, by reactions such as aldol condensation or acetal formation.1 For some of these salts, these catalytic properties were not even known in chemistry.2 Kinetic and product studies of these reactions will be presented for carbonyl compounds such as acetaldehyde, acetone, and glyoxal,1,3 and compared with previously known catalysts such as the recently discovered amino acids.4,5 These studies show that these salts make the reactions as fast in typical tropospheric aerosols as in concentrated sulfuric acid. These reactions produce secondary "fulvic" compounds that absorb light in the near UV and visible and would affect the optical properties of aerosols.1,5 They would also account for the depletion of glyoxal recently reported in Mexico city.3 Thus, while acid catalysis is several orders of magnitudes too slow to be significant in tropospheric aerosols, this work identifies new processes that should be ubiquitous in these aerosols and important for atmospheric chemistry. Refs. 1Noziere, B., Dziedzic, P., Cordova, A., Common inorganic ions catalyze chemical reactions of organic compounds in atmospheric aerosols, Submitted, 2008. 2 Noziere, B., Cordova, A., A novel catalyst for aldol condensation reaction, patent pending 02/10/2007. 3Noziere, B., Dziedzic, P., Cordova, A., Products and kinetics of the liquid-phase reaction of glyoxal catalyzed by inorganic ions, Submitted to J. Phys. Chem. A, 2008. 4Noziere, B., and Cordova, A., A Kinetic and Mechanistic Study of the Amino Acid-Catalyzed Aldol Condensation of Acetaldehyde in Aqueous and Salt Solutions, J. Phys. Chem. A, 112, 2827, 2008. 5Noziere, B., Dziedzic, P., and Cordova, A., The Formation of Secondary Light-Absorbing "fulvic-like" Oligomers: A Common Process in Aqueous and Ionic Atmospheric Particles?, Geophys. Res. Lett., 34

  13. Lactic Acid Production from Pretreated Hydrolysates of Corn Stover by a Newly Developed Bacillus coagulans Strain

    OpenAIRE

    Ting Jiang; Hui Qiao; Zhaojuan Zheng; Qiulu Chu; Xin Li; Qiang Yong; Jia Ouyang

    2016-01-01

    An inhibitor-tolerance strain, Bacillus coagulans GKN316, was developed through atmospheric and room temperature plasma (ARTP) mutation and evolution experiment in condensed dilute-acid hydrolysate (CDH) of corn stover. The fermentabilities of other hydrolysates with B. coagulans GKN316 and the parental strain B. coagulans NL01 were assessed. When using condensed acid-catalyzed steam-exploded hydrolysate (CASEH), condensed acid-catalyzed liquid hot water hydrolysate (CALH) and condensed acid-...

  14. Synthetic applications of gold-catalyzed ring expansions

    Directory of Open Access Journals (Sweden)

    Cristina Nevado

    2011-06-01

    Full Text Available The development of new methodologies catalyzed by late transition metals involving cycloisomerizations of strained rings can open new venues for the synthesis of structurally complex molecules with interesting biological activities. Herein we summarize, from both a synthetic as well as a mechanistic point of view, the most recent developments in gold-catalyzed ring expansions.

  15. The renaissance of palladium(II)-catalyzed oxidation chemistry

    OpenAIRE

    Sigman, Matthew S.; Schultz, Mitchell J.

    2004-01-01

    Palladium(II)-catalyzed oxidations constitute a paramount reaction class but have remained immature over the past few decades. Recently, this field has reappeared at the forefront of organometallic catalysis. This emerging area article outlines recent developments in palladium(II)-catalyzed oxidation chemistry with discussion of potential future growth.

  16. Toward Efficient Palladium-Catalyzed Allylic C-H Alkylation

    DEFF Research Database (Denmark)

    Jensen, Thomas; Fristrup, Peter

    2009-01-01

    Recent breakthroughs have proved that direct palladium (II)-catalyzed allylic C-H alkylation can be achieved. This new procedure shows that the inherent requirement for a leaving group in the Tsuji-Trost palladium-catalyzed allylic alkylation can be lifted. These initial reports hold great promise...

  17. Carbon Isotope Measurements of Experimentally-Derived Hydrothermal Mineral-Catalyzed Organic Products by Pyrolysis-Isotope Ratio Mass Spectrometry

    Science.gov (United States)

    Socki, Richard A.; Fu, Qi; Niles, Paul B.

    2011-01-01

    We report results of experiments to measure the C isotope composition of mineral catalyzed organic compounds derived from high temperature and high pressure synthesis. These experiments make use of an innovative pyrolysis technique designed to extract and measure C isotopes. To date, our experiments have focused on the pyrolysis and C isotope ratio measurements of low-molecular weight intermediary hydrocarbons (organic acids and alcohols) and serve as a proof of concept for making C and H isotope measurements on more complicated mixtures of solid-phase hydrocarbons and intermediary products produced during high temperature and high pressure synthesis on mineral-catalyzed surfaces. The impetus for this work stems from recently reported observations of methane detected within the Martian atmosphere [1-4], coupled with evidence showing extensive water-rock interaction during Martian history [5-7]. Methane production on Mars could be the result of synthesis by mineral surface-catalyzed reduction of CO2 and/or CO by Fischer-Tropsch Type (FTT) reactions during serpentization reactions [8,9]. Others have conducted experimental studies to show that FTT reactions are plausible mechanisms for low-molecular weight hydrocarbon formation in hydrothermal systems at mid-ocean ridges [10-12]. Further, recent experiments by Fu et al. [13] focus on examining detailed C isotope measurements of hydrocarbons produced by surface-catalyzed mineral reactions. Work described in this paper details the experimental techniques used to measure intermediary organic reaction products (alcohols and organic acids).

  18. Transition Metal Catalyzed Synthesis of Aryl Sulfides

    Directory of Open Access Journals (Sweden)

    Chad C. Eichman

    2011-01-01

    Full Text Available The presence of aryl sulfides in biologically active compounds has resulted in the development of new methods to form carbon-sulfur bonds. The synthesis of aryl sulfides via metal catalysis has significantly increased in recent years. Historically, thiolates and sulfides have been thought to plague catalyst activity in the presence of transition metals. Indeed, strong coordination of thiolates and thioethers to transition metals can often hinder catalytic activity; however, various catalysts are able to withstand catalyst deactivation and form aryl carbon-sulfur bonds in high-yielding transformations. This review discusses the metal-catalyzed arylation of thiols and the use of disulfides as metal-thiolate precursors for the formation of C-S bonds.

  19. Theoretical survey of muon catalyzed fusion

    International Nuclear Information System (INIS)

    The main steps in the muon-catalyzed d-t fusion cycle are given in this report. Most of the stages are very fast, and therefore do not contribute significantly to the cycling time. Thus at liquid H2 densities (/phi/ = 1 in the standard convention) the time for stopping the negative muon, its subsequent capture and deexcitation to the ground state is estimated to be /approximately/ 10/sup/minus/11/ sec.1 The muon spends essentially all of its time in either the (dμ) ground state, waiting for transfer to a (tμ) ground state to occur, or in the (tμ) ground state, writing for molecular formation to occur. Following the formation of this ''mesomolecule'' (actually a muonic molecular ion), deexcitation and fusion are again fast. Then the muon is (usually) liberated to go around again. We will discuss these steps in some detail. 5 refs., 3 figs

  20. Catalyzed deuterium fueled tandem mirror reactor assessment

    International Nuclear Information System (INIS)

    This study was part of a Department of Energy supported alternate fusion fuels program at Science Applications International Corp. The purpose of this portion of the study is to perform an assessment of a conceptual tandem mirror reactor (TMR) that is fueled by the catalyzed-deuterium (Cat-d) fuel cycle with respect to the physics, technology, safety, and cost. Achievable stable betas and magnet configurations are found to be comparable for the Cat-d and d-t fueled TMR. A comparison with respect to cost, reactor performance, and technology requirements for a Cat-d fueled reactor and a comparable d-t fueled reactor such as MARS is also made

  1. Gallium-Catalyzed Silicon Oxide Nanowire Growth

    Institute of Scientific and Technical Information of China (English)

    Zheng Wei Pan; Sheng Dai; Douglas H.Lowndes

    2005-01-01

    Silicon oxide nanowires tend to assemble into various complex morphologies through a metalcatalyzed vapor-liquid-solid (VLS) growth process. This article summarizes our recent efforts in the controlled growth of silicon oxide nanowire assemblies by using molten gallium as the catalyst and silicon wafer,SiO powder, or silane (SiH4) as the silicon sources. Silicon oxide nanowire assemblies with morphologies of carrotlike, cometlike, gourdlike, spindlelike, badmintonlike, sandwichlike, etc. were obtained. Although the morphologies of the nanowire assemblies are temperature- and silicon source-dependent, they share similar structural and compositional features: all the assemblies contain a microscale spherical liquid Ga ball and a highly aligned, closely packed amorphous silicon oxide nanowire bunch. The Ga-catalyzed silicon oxide nanowire growth reveals several interesting new nanowire growth phenomena that expand our knowledge of the conventional VLS nanowire growth mechanism.

  2. Direct conversion of muon catalyzed fusion energy

    International Nuclear Information System (INIS)

    In this paper a method of direct conversion of muon catalyzed fusion (MCF) energy is proposed in order to reduce the cost of muon production. This MCF concept is based on a pellet composed of many thin solid deuterium-tritium (DT) rods encircled by a metallic circuit immersed in a magnetic field. The direct energy conversion is the result of the heating of the pellet by beam injection and fusion alphas. The expanding DT rods causes the change of magnetic flux linked by the circuit. Our calculation shows that the direct conversion method reduces the cost of one muon by a factor of approximately 2.5 over the previous methods. The present method is compatible with a reactor using the pellet concept, where the muon sticking is reduced by the ion cyclotron resonance heating and the confinement of the exploding pellet is handled by magnetic fields and the coronal plasma. 17 refs., 6 figs

  3. Heterogeneously Catalyzed Oxidation Reactions Using Molecular Oxygen

    DEFF Research Database (Denmark)

    Beier, Matthias Josef

    . Compared to alcohol oxidation the epoxidation of olefins with molecular oxygen is more difficult. Using N,N-dimethylformamide (DMF) as a solvent the Co-based metal-organic framework (MOF) STA-12(Co) catalyzed the epoxidation of styrene, (E)- and (Z)-stilbene. While the stilbene isomers were converted....... XAS revealed that silver was in the metallic state. Silver particle sizes estimated from XAS were significantly smaller (2- 3 nm) than from transmission electron microscopy (TEM) and X-ray diffraction (XRD; ca. 30 nm). It was proposed that silver-oxygen species might cause local disorder which would...... of silver was observed with the impregnated silver catalyst. By using silver supported on CeO2-SiO2 prepared by flame spray pyrolysis, leaching could be limited significantly. XAS investigation revealed that the active catalyst is most likely metallic silver. Compared to silver on silica calcined at 500 °C...

  4. Enzyme-catalyzed degradation of carbon nanomaterials

    Science.gov (United States)

    Kotchey, Gregg P.

    Carbon nanotubes and graphene, the nanoscale sp 2 allotropes of carbon, have garnered widespread attention as a result of their remarkable electrical, mechanical, and optical properties and the promise of new technologies that harness these properties. Consequently, these carbon nanomaterials (CNMs) have been employed for diverse applications such as electronics, sensors, composite materials, energy conversion devices, and nanomedicine. The manufacture and eventual disposal of these products may result in the release of CNMs into the environment and subsequent exposure to humans, animals, and vegetation. Given the possible pro-inflammatory and toxic effects of CNMs, much attention has been focused on the distribution, toxicity, and persistence of CNMs both in living systems and the environment. This dissertation will guide the reader though recent studies aimed at elucidating fundamental insight into the persistence of CNMs such as carbon nanotubes (CNTs) and graphene derivatives (i.e., graphene oxide and reduced graphene oxide). In particular, in-testtube oxidation/degradation of CNMs catalyzed by peroxidase enzymes will be examined, and the current understanding of the mechanisms underlying these processes will be discussed. Finally, an outlook of the current field including in vitro and in vivo biodegradation experiments, which have benefits in terms of human health and environmental safety, and future directions that could have implications for nanomedical applications such as imaging and drug delivery will be presented. Armed with an understanding of how and why CNMs undergo enzyme-catalyzed oxidation/biodegradation, researchers can tailor the structure of CNMs to either promote or inhibit these processes. For example, in nanomedical applications such as drug delivery, the incorporation of carboxylate functional groups could facilitate biodegradation of the nanomaterial after delivery of the cargo. Also, the incorporation of CNMs with defect sites in consumer

  5. Mammalian-like Purple Acid Phosphatases in Plants

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    @@ Introduction Purple acid phosphatases (PAPs) comprise of a family of binuclear metal-containing hydrolases, some members of which have been isolated and characterized from animal, plant and fungal sources[1]. PAPs not only catalyze the hydrolyses of a wide range of phosphate esters and anhydrides under acidic reaction conditions,but also catalyze the generation of hydroxyl radicals in a Fenton-like reaction, by virtue of the presence of a redox-active binuclear metal center.

  6. Enhanced Acid/Base Catalysis in High Temperature Liquid Water

    Institute of Scientific and Technical Information of China (English)

    Xiu Yang LU; Qi JING; Zhun LI; Lei YUAN; Fei GAO; Xin LIU

    2006-01-01

    Two novel and environmentally benign solvent systems, organic acids-enriched high temperature liquid water (HTLW) and NH3-enriched HTLW, were developed, which can enhance the reaction rate of acid/base-catalyzed organic reactions in HTLW. We investigated the decomposition of fructose in organic acids-enriched HTLW, hydrolysis of cinnamaldehyde and aldol condensation of phenylaldehyde with acetaldehyde in NH3-enriched HTLW. The experimental results demonstrated that organic acids-enriched or NH3-enriched HTLW can greatly accelerate acid/base-catalyzed organic reactions in HTLW.

  7. Ammonia and hydrazine. Transition-metal-catalyzed hydroamination and metal-free catalyzed functionalization

    Energy Technology Data Exchange (ETDEWEB)

    Bertrand, Guy [Univ. of California, San Diego, CA (United States)

    2012-06-29

    high temperatures and long reaction times. To address this issue, we have developed several new families of carbon- and boron-based ligands, which are even better donors. The corresponding metal complexes (particularly gold, rhodium, iridium, and ruthenium) of all these species will be tested in the Markovnikov and anti-Markovnikov hydroamination of alkynes, allenes, and also alkenes with ammonia and hydrazine. We will also develop metal-free catalytic processes for the functionalization of ammonia and hydrazine. By possessing both a lone pair of electrons and an accessible vacant orbital, singlet carbenes resemble and can mimic the chemical behavior of transition metals. Our preliminary results demonstrate that specially designed carbenes can split the N–H bond of ammonia by an initial nucleophilic activation that prevents the formation of Lewis acid-base adducts, which is the major hurdle for the transition metal catalyzed functionalization of NH3. The use of purely organic compounds as catalysts will eliminate the major drawbacks of transition-metal-catalysis technology, which are the excessive cost of metal complexes (metal + ligands) and in many cases the toxicity of the metal.

  8. Effect of Ozone Produced from Antibody-catalyzed Water Oxidation on Pathogenesis of Atherosclerosis

    Institute of Scientific and Technical Information of China (English)

    Ke-Jun PENG; Yu-Shan HUANG; Li-Na AN; Xiao-Qun HAN; Jing-Ge ZHANG; Qiu-Lin WANG; Jing SUN; Shu-Ren WANG

    2006-01-01

    Recent studies have suggested that antibodies can catalyze the generation of unknown oxidants including hydrogen peroxide (H2O2) and ozone (O3) from singlet oxygen (1O2) and water. This study is aimedto detect the effect of antibody-catalyzed water oxidation on atherosclerosis. Our results showed that both H2O2 and O3 were produced in human leukemia THP- 1 monocytes incubated with human immunoglobulin G and phorbol myristate acetate. In the THP-1 monocytes incubated with human immunoglobulin G, phorbol myristate acetate and low density lipoprotein, the intracellular total cholesterol, free cholesterol, cholesteryl ester and lipid peroxides clearly increased, and a larger number of foam cells were observed by oil red O staining. The accumulation of all intracellular lipids was significantly inhibited by vinylbenzoic acid, and only slightly affected by catalase. These findings suggested that the production of O3, rather than H2O2, might be involved in the pathogenesis of atherosclerosis through the antibody-catalyzed water oxidation pathway.

  9. Versatile Oxidation Methods for Organic and Inorganic Substrates Catalyzed by Platinum-Group Metals on Carbons.

    Science.gov (United States)

    Sawama, Yoshinari; Asai, Shota; Monguchi, Yasunari; Sajiki, Hironao

    2016-02-01

    Platinum-group metals on activated carbon catalysts, represented by Pd/C, Ru/C, Rh/C, etc., are widely utilized to accomplish green and sustainable organic reactions due to their favorable features, such as easy handling, recoverability, and reusability. The efficient oxidation methods of various organic compounds using heterogeneous platinum-group metals on carbons with or without added oxidants are summarized in this Personal Account. The oxidation of internal alkynes into diketones was effectively catalyzed by Pd/C in the presence of dimethyl sulfoxide and molecular oxygen or pyridine N-oxide. The Pd/C-catalyzed mild combustion of gaseous hydrogen with molecular oxygen provided hydrogen peroxide, which could be directly utilized for the oxidation of sulfide derivatives into sulfoxides. Furthermore, the Ru/C-catalyzed aerobic oxidation of primary and secondary alcohols gave the corresponding aldehydes and ketones, respectively. On the other hand, the dehydrogenative oxidation of secondary alcohols into ketones was achieved using Rh/C in water, and primary alcohols were effectively dehydrogenated by Pd/C in water under mildly reduced pressure to produce carboxylic acids. PMID:26666634

  10. Multistep divergent synthesis of benzimidazole linked benzoxazole/benzothiazole via copper catalyzed domino annulation.

    Science.gov (United States)

    Liao, Jen-Yu; Selvaraju, Manikandan; Chen, Chih-Hau; Sun, Chung-Ming

    2013-04-21

    An efficient, facile synthesis of structurally diverse benzimidazole integrated benzoxazole and benzothiazoles has been developed. In a multi-step synthetic sequence, 4-fluoro-3-nitrobenzoic acid was converted into benzimidazole bis-heterocycles, via the intermediacy of benzimidazole linked ortho-chloro amines. The amphiphilic reactivity of this intermediate was designed to achieve the title compounds by the reaction of various acid chlorides and isothiocyanates in a single step through the in situ formation of ortho-chloro anilides and thioureas under microwave irradiation. A versatile one pot domino annulation reaction was developed to involve the reaction of benzimidazole linked ortho-chloro amines with acid chlorides and isothiocyanates. The initial acylation and urea formation followed by copper catalyzed intramolecular C-O and C-S cross coupling reactions furnished the angularly oriented bis-heterocycles which bear a close resemblance to the streptomyces antibiotic UK-1.

  11. Lipase-catalyzed Kinetic Resolution of Racemic 1-Trimethylsilylethanol in Organic Solvent

    Institute of Scientific and Technical Information of China (English)

    吴虹; 宗敏华; 王菊芳; 罗涤衡; 娄文勇

    2004-01-01

    The enantioselective esterification of racemic 1-trimethylsilylethanol with acids catalyzed by lipase in organic solvent was successfully performed. The influence of some factors on the reaction was investigated. Among the four lipases explored, Candlda rugosa lipase (CRL) showed the highest activity and enantioselectivity. Octanoic acid was the best acyl donor among the eleven acids studied and n-hexane was the most suitable medium for the reaction. The optimum shaking rate and temperature were found to be 150 r-rain-i and 20~(3 to 30~C, respectively.The enantiomeric excess of the remaining (S)-(-)-1-trimethylsilylethanol was 93% when substrate conversion was 53% upon incubation of the reaction mixture at 30~C, 150 r-rain-i for 12 h.

  12. Precision Synthesis of Functional Polysaccharide Materials by Phosphorylase-Catalyzed Enzymatic Reactions

    Directory of Open Access Journals (Sweden)

    Jun-ichi Kadokawa

    2016-04-01

    Full Text Available In this review article, the precise synthesis of functional polysaccharide materials using phosphorylase-catalyzed enzymatic reactions is presented. This particular enzymatic approach has been identified as a powerful tool in preparing well-defined polysaccharide materials. Phosphorylase is an enzyme that has been employed in the synthesis of pure amylose with a precisely controlled structure. Similarly, using a phosphorylase-catalyzed enzymatic polymerization, the chemoenzymatic synthesis of amylose-grafted heteropolysaccharides containing different main-chain polysaccharide structures (e.g., chitin/chitosan, cellulose, alginate, xanthan gum, and carboxymethyl cellulose was achieved. Amylose-based block, star, and branched polymeric materials have also been prepared using this enzymatic polymerization. Since phosphorylase shows a loose specificity for the recognition of substrates, different sugar residues have been introduced to the non-reducing ends of maltooligosaccharides by phosphorylase-catalyzed glycosylations using analog substrates such as α-d-glucuronic acid and α-d-glucosamine 1-phosphates. By means of such reactions, an amphoteric glycogen and its corresponding hydrogel were successfully prepared. Thermostable phosphorylase was able to tolerate a greater variance in the substrate structures with respect to recognition than potato phosphorylase, and as a result, the enzymatic polymerization of α-d-glucosamine 1-phosphate to produce a chitosan stereoisomer was carried out using this enzyme catalyst, which was then subsequently converted to the chitin stereoisomer by N-acetylation. Amylose supramolecular inclusion complexes with polymeric guests were obtained when the phosphorylase-catalyzed enzymatic polymerization was conducted in the presence of the guest polymers. Since the structure of this polymeric system is similar to the way that a plant vine twines around a rod, this polymerization system has been named

  13. CYP71B15 (PAD3) Catalyzes the Final Step in Camalexin Biosynthesis1

    Science.gov (United States)

    Schuhegger, Regina; Nafisi, Majse; Mansourova, Madina; Petersen, Bent Larsen; Olsen, Carl Erik; Svatoš, Aleš; Halkier, Barbara Ann; Glawischnig, Erich

    2006-01-01

    Camalexin represents the main phytoalexin in Arabidopsis (Arabidopsis thaliana). The camalexin-deficient phytoalexin deficient 3 (pad3) mutant has been widely used to assess the biological role of camalexin, although the exact substrate of the cytochrome P450 enzyme 71B15 encoded by PAD3 remained elusive. 2-(Indol-3-yl)-4,5-dihydro-1,3-thiazole-4-carboxylic acid (dihydrocamalexic acid) was identified as likely intermediate in camalexin biosynthesis downstream of indole-3-acetaldoxime, as it accumulated in leaves of silver nitrate-induced pad3 mutant plants and it complemented the camalexin-deficient phenotype of a cyp79b2/cyp79b3 double-knockout mutant. Recombinant CYP71B15 heterologously expressed in yeast catalyzed the conversion of dihydrocamalexic acid to camalexin with preference of the (S)-enantiomer. Arabidopsis microsomes isolated from leaves of CYP71B15-overexpressing and induced wild-type plants were capable of the same reaction but not microsomes from induced leaves of pad3 mutants. In conclusion, CYP71B15 catalyzes the final step in camalexin biosynthesis. PMID:16766671

  14. One-pot conversion of disaccharide into 5-hydroxymethylfurfural catalyzed by imidazole ionic liquid.

    Science.gov (United States)

    Qu, Yongshui; Li, Li; Wei, Quanyuan; Huang, Chongpin; Oleskowicz-Popiel, Piotr; Xu, Jian

    2016-01-01

    Conversion of carbohydrate into 5-hydroxymethylfurfural (5- HMF), a versatile, key renewable platform compound is regarded as an important transformation in biomass-derived carbohydrate chemistry. A variety of ILs, not only acidic but also alkaline ILs, were synthesized and used as catalyst in the production of 5-HMF from disaccharide. Several factors including reaction temperature, IL dosage, solvent and reaction time,were found to influence the yield of 5-HMF from cellobiose. Of the ILs tested, hydroxy-functionalized ionic liquid (IL), 1-hydroxyethyl-3-methylimidazolium tetrafluoroborate ([AEMIM]BF4) showed the highest catalytic activity and selectivity. 5-HMF yield of 68.71% from sucrose was obtained after 6 hrs at 160 °C. At the same condition with cellobiose as substrate, 5-HMF yield was 24.73%. In addition, 5-HMF also exhibited good stablity in this reaction system. Moreover, a kinetic analysis was carried out in both acidic and alkaline IL-catalyzed system, suggesting main side reaction in the conversion of fructose catalyzed by acidic and alkaline IL was polymerization of fructose and 5-HMF degradation, respectively. PMID:27181523

  15. Oligomerization of Glycine and Alanine Catalyzed by Iron Oxides: Implications for Prebiotic Chemistry

    Science.gov (United States)

    Shanker, Uma; Bhushan, Brij; Bhattacharjee, G.; Kamaluddin

    2012-02-01

    Iron oxide minerals are probable constituents of the sediments present in geothermal regions of the primitive earth. They might have adsorbed different organic monomers (amino acids, nucleotides etc.) and catalyzed polymerization processes leading to the formation of the first living cell. In the present work we tested the catalytic activity of three forms of iron oxides (Goethite, Akaganeite and Hematite) in the intermolecular condensation of each of the amino acids glycine and L-alanine. The effect of zinc oxide and titanium dioxide on the oligomerization has also been studied. Oligomerization studies were performed for 35 days at three different temperatures 50, 90 and 120°C without applying drying/wetting cycling. The products formed were characterized by HPLC and ESI-MS techniques. All three forms of iron oxides catalyzed peptide bond formation (23.2% of gly2 and 10.65% of ala2). The reaction was monitored every 7 days. Formation of peptides was observed to start after 7 days at 50°C. Maximum yield of peptides was found after 35 days at 90°C. Reaction at 120°C favors formation of diketopiperazine derivatives. It is also important to note that after 35 days of reaction, goethite produced dimer and trimer with the highest yield among the oxides tested. We suggest that the activity of goethite could probably be due to its high surface area and surface acidity.

  16. DFT Study on the (S)-Proline-catalyzed Direct Aldol Reaction between Acetone and 4-Nitrobenzaldehyde

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    DFT/6-31G* calculations were applied to study the direct aldol reaction between acetone and 4-nitrobenzaldehyde catalyzed by (S)-proline. Four transition states associated with the stereo-controlling step, corresponding to syn and anti arrangements of methylene moiety related to the carboxylic acid group in enamine intermediate and re and si attacks to the aldehyde carbonyl carbon have been obtained. The solvent effect of DMSO was investigated with polarized continuum model. The computed energies of transition states reveal the stereo-selectivity of the reaction.

  17. [Development of novel methods for synthesis of heterocyclic compounds catalyzed by transition metals in fluorinated alcohols].

    Science.gov (United States)

    Saito, Akio

    2008-08-01

    New possibilities for catalytic syntheses of lactone derivatives and nitrogen-containing heterocyclic compounds in fluorinated alcohols are described. The cationic Rh(I) catalyst in fluorinated alcohol solvents (hexafluoroisopropanol: HFIP, trifluoroethanol: TFE) brought about not only mild cycloaddition reactions of ester-tethered compounds but also a facile formation of indole derivatives by the aromatic amino-Claisen rearrangement of N-propargyl aniline derivatives. The use of HFIP as an additive exerted a remarkable effect on the Pictet-Spengler reaction catalyzed by the fluorinated surfactant-combined Brønsted acid catalyst in water.

  18. Chemo-enzymatic epoxidation of fatty compounds – Focus on processes involving a lipase-catalyzed perhydrolysis step

    Directory of Open Access Journals (Sweden)

    Tiran Céline

    2008-05-01

    Full Text Available At the industrial scale, the chemical Prileshajev reaction is currently the only method applied to produce epoxidized plant oils. Using enzymes could be an alternative way allowing an environmentally benign and more selective epoxidation reaction. P450 monooxygenases, diiron-center oxygenases, lipoxygenases, peroxygenases, and hydrolases performing perhydrolysis are enzyme classes involved in free fatty acid and glyceride epoxidation. After a brief description of these biocatalysts, this review focuses on the chemo-enzymatic epoxidation of unsaturated fatty acyd chains, where a lipase-catalyzed peroxy acid formation is followed by an uncatalyzed “self-epoxidation”. The molecular bases of lipase-catalyzed perhydrolysis as well as the different parameters influencing the epoxidation reaction are reviewed and described in details.

  19. An approach to the synthesis of dimeric resveratrol natural products via a palladium-catalyzed domino reaction

    OpenAIRE

    Jeffrey, Jenna L.; Sarpong, Richmond

    2009-01-01

    A route for the rapid assembly of the carbon framework of several resveratrol natural products is presented. A palladium-catalyzed domino reaction of bromostilbene derivative 6 and tolane 7, involving two sequential Heck coupling reactions, provides access to the benzofulvene-based core of various resveratrol-derived natural products. The carbon skeleton of pallidol and its congeners is achieved by a Lewis acid-induced Nazarov-type oxidative cyclization of 9.

  20. Rhodium-Catalyzed Acyloxy Migration of Propargylic Esters in Cycloadditions, Inspiration from Recent “Gold Rush”

    OpenAIRE

    Shu, Xing-Zhong; Shu, Dongxu; Schienebeck, Casi M.; TANG, WEIPING

    2012-01-01

    Transition metal-catalyzed acyloxy migration of propargylic esters offers versatile entries to allene and vinyl carbene intermediates for various fascinating subsequent transformations. Most π-acidic metals (e.g. gold and platinum) are capable of facilitating these acyloxy migration events. However, very few of these processes involve redox chemistry, which are well-known for most other transition metals such as rhodium. The coupling of acyloxy migration of propargylic esters with oxidative a...