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Transesterification
Kinds of Transesterification Terms modified by Transesterification Selected AbstractsA NEW METHOD FOR EXTRACTION, ISOLATION AND TRANSESTERIFICATION OF FREE FATTY ACIDS FROM ARCHAEOLOGICAL POTTERYARCHAEOMETRY, Issue 5 2010M. W. GREGG This paper presents evidence for increased recovery of organic residues from archaeological pottery through use of a microwave-assisted liquid chromatography protocol. C16:0 and C18:0 saturated fatty acids were obtained from archaeological potsherds recovered from nine Neolithic settlements in the Middle East dating between 4700 and 7300 cal bc, including materials that had not produced evidence for the survival of any lipid species through use of ,conventional' solvent extraction techniques. Compound-specific isotopic analyses of C16:0 and C18:0 fatty acids in potsherd extracts subsequently revealed ,13C/,12C compositions consistent with modern subcutaneous fats of wild boar and goats pastured on lands adjacent to the Jordan Valley, and residues from a modern pottery vessel used in the manufacturing of butter, cheese and yogurt in central Turkey. These results are presented as an illustration of capabilities of the microwave-assisted recovery protocol. The reclamation of saturated and unsaturated fatty acids from archaeological pottery fragments recovered from a number of the earliest ceramic horizons in the Middle East is herewith reported, and the extraction methods and instrumental analytical techniques are described. [source] Micro-reactor for transesterification of plant seed oilsEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 5 2009Phattaraporn Kaewkool Abstract The fatty acid compositions of vegetable or other plant seed oils are generally determined by gas chromatography (GC). Methyl esters (the most volatile derivatives) are the preferred derivatives for GC analysis. Esters of higher alcohols are good for the separation of volatile and positional isomers. All the esters of the C1,C8 alcohols of vegetable oils were silmilarly prepared by passing the reaction mixture containing the desired alcohol, oil and tetrahydrofuran through the micro-reactor (a 3-mL dispossible syringe packed with 0.5,g of NaOH powder). The reaction products were acidified with acetic acid and the mixture was analyzed by high-performance size exclusion chromatography and GC. Transesterification was quantitative for primary alcohols, but an appreciable amount of free fatty acids was formed for secondary alcohols. Coriander seed oil was quantitatively esterified with 2-ethyl 1-hexanol with the micro-reactor in less than 1,min. Oleic and petroselinic acid 2-ethyl 1-hexyl esters are baseline separated on an Rtx-2330 capillary column (30,m×0.25,mm, 0.25,µm film thickness). [source] Silylation-Mediated Transesterification of O -Phenyl H-Phosphonothioates , A New Entry to Nucleoside H-Phosphonothioate MonoestersEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 24 2004Gaston Lavén Abstract O -Phenyl H-phosphonothioate undergoes a facile transesterification with suitably protected nucleosides upon in situ silylation with tert -butyldiphenylsilyl chloride in pyridine/ toluene to produce the corresponding 3,-H-phosphonothioates in good yields. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Silica-Supported Zirconium Complexes and their Polyoligosilsesquioxane Analogues in the Transesterification of Acrylates: Part 1.ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 13 2009Characterization, Synthesis Abstract Various silica-supported acetylacetonate and alkoxy zirconium(IV) complexes have been prepared and characterized by quantitative chemical measurements of the surface reaction products, quantitative surface microanalysis of the surface complexes, in situ infrared spectroscopy, CP-MAS 13C,NMR spectroscopy and EXAFS. The complex (SiO)Zr(acac)3 (acac=acetylacetonate ligand) (1) can be obtained by reaction of zirconium tetraacetylacetonate [Zr(acac)4] with a silica surface previously dehydroxylated at 500,°C. The complexes (SiO)3Zr(acac) (2) and (SiO)3Zr(O- n- Bu) (n- Bu=butyl ligand) (3) can be synthesized by reaction of (SiO)3ZrH with, respectively, acetylacetone and n -butanol at room temperature. The spectroscopic data, including EXAFS spectroscopy, confirm that in compound 1 the zirconium is linked to the surface by only one SiOZr bond whereas in the case of compounds 2 and 3 the zirconium is linked to 3 surface oxygen atoms which are sigma bonded. EXAFS data indicate also that the acetylacetonate ligands behave as chelating ligands leading to a hepta-coordination around the zirconium atom in 1 and a penta-coordination in 2. In order to provide a molecular analogue of 1, the synthesis of the following polyoligosilsesquioxane derivative (c -C5H9)7Si8O12(CH3)2Zr(acac)3 (1,) was achieved. The compound 1, is obtained by reacting (c -C5H9)7Si8O11(CH3)2(OH), 4, with an equimolecular amount of Zr(acac)4. In the same manner, syntheses of complexes (c -C5H9)7Si7O12Zr(acac) (2,) and of (c-C5H9)7Si7O12Zr(O- n- Bu) (3,) were achieved by reaction of the unmodified trisilanol, (c -C5H9)7Si7O9(OH)3, with respectively Zr(acac)4 and Zr(O- n- Bu)4 at 60,°C in tetrahydrofuran. Compounds 1,, 2, and 3, can be considered as good models of 1, 2 and 3 since their spectroscopic properties are comparable with those of the surface complexes. The synthetic results obtained will permit us to study the catalytic properties of these surface complexes and of their molecular analogues with the ultimate goal of delineating clear structure-activity relationships. [source] Silica-Supported Zirconium Complexes and their Polyoligosilsesquioxane Analogues in the Transesterification of Acrylates: Part 2.ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 13 2009Activity, Recycling, Regeneration Abstract The catalytic activity of both supported and soluble molecular zirconium complexes was studied in the transesterification reaction of ethyl acrylate by butanol. Two series of catalysts were employed: three well defined silica-supported acetylacetonate and n -butoxy zirconium(IV) complexes linked to the surface by one or three siloxane bonds, (SiO)Zr(acac)3 (1) (SiO)3Zr(acac) (2) and (SiO)3Zr(O- n -Bu) (3), and their soluble polyoligosilsesquioxy analogues (c -C5H9)7Si8O12(CH3)2Zr(acac)3 (1,), (c -C5H9)7Si7O12Zr(acac) (2,), and (c -C5H9)7Si7O12Zr(O- n -Bu) (3,). The reactivity of these complexes were compared to relevant molecular catalysts [zirconium tetraacetylacetonate, Zr(acac)4 and zirconium tetra- n -butoxide, Zr(O- n- Bu)4]. Strong activity relationships between the silica-supported complexes and their polyoligosilsesquioxane analogues were established. Acetylacetonate complexes were found to be far superior to alkoxide complexes. The monopodal complexes 1 and 1, were found to be the most active in their respective series. Studies on the recycling of the heterogeneous catalysts showed significant degradation of activity for the acetylacetonate complexes (1 and 2) but not for the less active tripodal alkoxide catalyst, 3. Two factors are thought to contribute to the deactivation of catalyst: the lixivation of zirconium by cleavage of surface siloxide bonds and exchange reactions between acetylacetonate ligands and alcohols in the substrate/product solution. It was shown that the addition of acetylacetone to the low activity catalyst Zr(O- n- Bu)4 produced a system that was as active as Zr(acac)4. The applicability of ligand addition to heterogeneous systems was then studied. The addition of acetylacetone to the low activity solid catalyst 3 produced a highly active catalyst and the addition of a stoichiometric quantity of acetylacetone at each successive batch catalytic run greatly reduced catalyst deactivation for the highly active catalyst 1. [source] Studies in transesterification of ethylene carbonate to dimethyl carbonate over Amberlyst A-21 catalystJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 1 2006Shekhar M Dhuri Abstract Transesterification of ethylene carbonate (EC) with methanol (MeOH) was studied in a slurry reactor using various homogeneous and heterogeneous, acidic as well as basic, catalysts. Among all catalysts studied, the weakly basic anion-exchange resin Amberlyst A-21 gave more than 95% selectivity towards dimethyl carbonate (based on EC converted). Using this Amberlyst A-21 as a catalyst, the kinetics for the transesterification reaction was studied in the range of temperature from 363 to 393 K, varying catalyst loading from 11.24 to 44.97 kg m,3 and the molar ratio MeOH:EC being varied between 4:1 and 16:1. The initial rate data were analysed using a power law model to aid process design. Copyright © 2005 Society of Chemical Industry [source] Transesterification for biodiesel production catalyzed by combined lipases: Optimization and kineticsAICHE JOURNAL, Issue 6 2010Yun Liu Abstract Preparation of biodiesel from waste cooking oil catalyzed by combined lipases in tert -butanol medium was investigated. Several crucial parameters affecting biodiesel yield were optimized by response surface methodology, such as dosage of combined lipases of Novozym 435 and Lipozyme TLIM, weight ratio of Novozym 435 to Lipozyme TLIM, amount of tert -butanol, reaction temperature, and molar ratio of oil to methanol. Under the optimized conditions, the highest biodiesel yield was up to 83.5% The proposed model on biodiesel yield had a satisfactory coefficient of R2 (= 94.02%), and was experimentally verified. The combined lipases exhibited high-operational stability. After 30 cycles (300 h) successively, the activity of combined lipases maintained 85% of its original activity. A reaction kinetic model was proposed to describe the system and deduced to be a pseudo-first-order reaction, and the calculated activation energy was 51.71 kJ/mol. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Transesterification of dimethyl oxalate with phenol over TiO2/SiO2: Catalyst screening and reaction optimizationAICHE JOURNAL, Issue 12 2008Xia Yang Abstract Physicochemical properties of silica-supported titanium oxide catalysts as well as their performances for transesterification of dimethyl oxalate (DMO) with phenol to methyl phenyl oxalate (MPO) and diphenyl oxalate (DPO) have been investigated systematically. Various wt % of TiO2 were loaded on SiO2 by a two-step wet impregnation method. The surface properties of TiO2/SiO2 catalysts were explored by various characterization techniques (BET, SEM, ICP, XPS, XRD, FTIR of pyridine adsorption, and NH3 -TPD). Catalytic performances of TiO2/SiO2 catalysts were found to be strongly dependent on TiO2 dispersion and surface acidity. Monolayer dispersion capacity of TiO2 on silica was estimated to be about 4.0 TiO2 molecules per nm2 (SiO2) and no crystalline TiO2 was detected at TiO2 loading less than 12 wt %. FTIR and TPD analysis suggested that weak Lewis acid sites on the surface of TiO2/SiO2 were responsible for their unique selectivity to the target products, MPO and DPO. An optimization of reaction conditions for the transesterification of DMO with phenol was performed over 12 wt % TiO2/SiO2 calcined at 550°C. In addition, we studied the disproportionation reaction from MPO to DPO via a catalytic distillation process, which is highly efficient to promote formation of the desired DPO. © 2008 American Institute of Chemical Engineers AIChE J, 2008 [source] Lithocholic-acid-containing poly(ester,anhydride)sPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 11-12 2003Michal Y. Krasko Abstract New degradable poly(ester-anhydride)s were prepared by melt polycondensation of poly(sebacic acid) (PSA), transesterified by different amounts (30,90%) of lithocholic acid (LCA), a natural hydroxy bile acid. Transesterification of PSA is a one-pot reaction that starts with a high-molecular-weight polymer based on anhydride bonds and yields polymer based on random anhydride,ester bonds. A systematic study of the synthesis, characterization, degradation in vitro, drug release, and stability of these polymers was performed. Polymers with molecular weights (Mw) in the range of 12,000,115,000 and melting points in the range of 55,112,°C were obtained for 30,90% of lithocholic acid content. NMR and IR spectroscopic analyses indicate the formation of ester bonds in the polyanhydride backbone. The experimental results fit the calculated molecular weight, with the highest Mw obtained for a 4:6 PSA,LCA ratio. The study shows that some of these new degradable copolymers can be potentially used as carriers for the controlled release of drugs. Copyright © 2003 John Wiley & Sons, Ltd. [source] Reaction Kinetics of Soybean Oil Transesterification Using Heterogeneous Metal Oxide CatalystsCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 12 2007K. Singh Abstract Homogeneous acid or base catalysts dissolve fully in the glycerol layer and partially in the fatty acid methyl ester (biodiesel) layer in the triglyceride transesterification process. Heterogeneous (solid) catalysts, on the other hand, can prevent catalyst contamination making product separation much simpler. In the present work, the transesterification kinetics of five different solid catalysts with soybean oil is presented. It is found that heterogeneous catalysts require much higher temperatures and pressures to achieve acceptable conversion levels compared to homogeneous catalysts. Subsequent to preliminary investigations, transesterifications were conducted for selected high performance solid catalysts, i.e., MgO, CaO, BaO, PbO, and MnO2 in a high pressure reactor up to a temperature of 215,°C. The yield of the fatty acid methyl esters and the kinetics (rate constant and order) of the reaction are estimated and are compared for each catalyst. [source] ChemInform Abstract: Sequential Coupling of the Transesterification of Cyclic Carbonates with the Selective N-Methylation of Anilines Catalyzed by Faujasites.CHEMINFORM, Issue 7 2009Maurizio Selva Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Phosphine-Catalyzed Tandem ,-O-Addition and Transesterification of Oxygen Pronucleophiles on Arylpropiolates: A New Route to Dioxygenated Heterocycles.CHEMINFORM, Issue 25 2007Sandra Gabillet Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Increased Enantioselectivity and Remarkable Acceleration of Lipase-Catalyzed Transesterification by Using an Imidazolium PEG,Alkyl Sulfate Ionic Liquid.CHEMINFORM, Issue 14 2007Toshiyuki Itoh Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Lipase-Catalyzed Irreversible Transesterification of Secondary Alcohols Using Isopropenyl Acetate.CHEMINFORM, Issue 45 2003Ashraf Ghanem Abstract For Abstract see ChemInform Abstract in Full Text. [source] Ionic Liquid Regulated Sulfamic Acid: Chemoselective Catalyst for the Transesterification of ,-Ketoesters.CHEMINFORM, Issue 40 2003Wang Bo No abstract is available for this article. [source] Lipase-Catalyzed Transesterification of Methyl 2-Substituted 3-Hydroxy-4-pentenoates and Its Synthetic Application to the Taxol Side Chain.CHEMINFORM, Issue 5 2003Tadakatsu Mandai Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: Optimum Conformational Flexibility of Subtilisin to Maximize the Enantioselectivity for Subtilisin-Catalyzed Transesterification in an Organic Solvent with an Addition of Dimethyl Sulfoxide.CHEMINFORM, Issue 44 2001Keiichi Watanabe Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Kinetics of Bis(p -nitrophenyl)phosphate (BNPP) Hydrolysis Reactions with Trivalent Lanthanide Complexes of N -Hydroxyethyl(ethylenediamine)- N,N,,N, -triacetate (HEDTA),EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 8 2009C. Allen Chang Abstract Kinetic studies of hydrolysis reactions of BNPP [sodium bis(p -nitrophenyl)phosphate] with trivalent lanthanide (Ln3+) complexes of HEDTA [HEDTA = N -hydroxyethyl(ethylenediamine)- N,N,,N, -triacetate] were performed at pH 6.96,11.34 and 25 °C by a spectrophotometric method and by HPLC analysis. The reaction rates increase with increasing atomic number of lanthanide and solution pH from PrHEDTA to EuHEDTA and then decrease for heavier LnHEDTA complexes. Plots of pseudo-first-order rate constants (kobs) vs. pH could be fitted to the equation kobs = kLnL(OH)[LnL]T/{1,+,exp[,2.303(pH,,,pKh)]}, where kLnL(OH) is the rate constant for the reaction of LnHEDTA(OH), with BNPP, Kh is the hydrolysis constant of LnHEDTA, and [LnL]T is the total concentration of LnHEDTA. The pKh values obtained by the kinetic method are in the range 8.2,10.3 and are similar to those measured by potentiometric methods. At [LnL]T = 10,70 mM and pH 10.5, most of the observed pseudo-first-order rate constants could be fitted to a simple saturation kinetic model, kobs = k1K[LnHEDTA(OH),]/{1 + K[LnHEDTA(OH),]}, where K is the equilibrium constant for the formation for LnHEDTA(OH),BNPP and is in the range 2,147 M,1. The k1 values are in the range 1.12,×,10,5,2.71,×,10,3 s,1. The kobs data for TbHEDTA and HoHEDTA were fitted to a quadratic equation. It was observed that the dinuclear species are more reactive. ESI mass spectrometry confirmed that the reaction between BNPP and EuHEDTA is a simple hydrolysis but not a transesterification, presumably because the three inner-sphere coordinated water molecules are far away from the coordinated hydroxyethyl group. Hydrolysis is likely to occur by proton transfer from one inner-sphere coordinated water molecule to the deprotonated ethyl oxide group followed by nucleophilic attack of the resulting hydroxide ion on the bonded BNPP anion.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Postprandial lipemic response to alpha-linolenic acid rich oil, butter, and olive oilEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 9 2010Julia Svensson Abstract Postprandial lipemia varies with composition of dietary fat due to partitioning of fatty acids between ,-oxidation, incorporation into TAG, and tissue lipids. Effects of alpha-linolenic acid (ALA) are poorly characterized. Lipase-catalyzed transesterification was used to produce a novel ALA-oil (35% ALA) from rapeseed and linseed oil. We hypothesized a lower postprandial lipemic response with ALA-oil than with olive oil and butter due to higher ,-oxidation of ALA. A randomized crossover study with 26 healthy men compared the effects on plasma lipids 7,h after a breakfast containing 35,g ALA-rich oil, butter fat, or olive oil. The incremental area under curve for plasma TAG was lower with butter than with olive oil (34%, p<0.05) and ALA-oil (25%, ns). After ALA-oil percentage ALA increased, in TAG to a constant level of 7,mol% and in NEFA to 6% after 7,h. Since total NEFA increased with time the amount of exogenous ALA in NEFA also increased. Butter resulted in lower postprandial lipemia than the oils, the difference exceeding what is expected from the presence of short and medium chain fatty acids in butter. There was a considerable recirculation of ALA into the NEFA pool available for oxidation. Practical application: Enzymatic transesterification was used to produce a dietary oil rich in ALA. By randomizing the partitioning of ALA more evenly between the TAG molecules the risk of oxidation could be reduced. Analyses showed that the ALA-oil was stable during storage for at least 3 months. Enzymatic transesterification could be used as an advantageous method to design an ALA rich dietary oil with new properties regarding fatty acid composition, susceptibility to oxidation, and effects on blood lipids. [source] Quantification of free and esterified steryl glucosides in vegetable oils and biodieselEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 8 2009Florence Lacoste Dr. Abstract Steryl glucosides (SG) are minor components that dramatically modify the low temperature performance of fatty acid methyl esters (FAME) used as biodiesel. SG are naturally present in vegetable oils but they may also be the result of the transesterification of esterified steryl glucosides (ESG). These are present in vegetable oils at a level of a few hundred milligrams per kilogram, depending on the nature of the feedstock. We developed an analytical method to quantify SG and ESG in vegetable oils and in FAME. The purification of SG and ESG was performed by liquid chromatography on silica gel, and the analysis of the trimethylsilyl derivatives was achieved by gas chromatography and flame ionization detection. The filterability of biodiesel is affected when the SG content is higher than 20,mg/kg. Therefore, the sensitivity of this new method is adapted for this purpose since the quantification limit is 10,mg/kg of SG and ESG. The recoveries are acceptable, between 75% and 90% depending on the species and content, and the reproducibility relative standard deviation, evaluated at 10%, is comparable to other studies. [source] Micro-reactor for transesterification of plant seed oilsEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 5 2009Phattaraporn Kaewkool Abstract The fatty acid compositions of vegetable or other plant seed oils are generally determined by gas chromatography (GC). Methyl esters (the most volatile derivatives) are the preferred derivatives for GC analysis. Esters of higher alcohols are good for the separation of volatile and positional isomers. All the esters of the C1,C8 alcohols of vegetable oils were silmilarly prepared by passing the reaction mixture containing the desired alcohol, oil and tetrahydrofuran through the micro-reactor (a 3-mL dispossible syringe packed with 0.5,g of NaOH powder). The reaction products were acidified with acetic acid and the mixture was analyzed by high-performance size exclusion chromatography and GC. Transesterification was quantitative for primary alcohols, but an appreciable amount of free fatty acids was formed for secondary alcohols. Coriander seed oil was quantitatively esterified with 2-ethyl 1-hexanol with the micro-reactor in less than 1,min. Oleic and petroselinic acid 2-ethyl 1-hexyl esters are baseline separated on an Rtx-2330 capillary column (30,m×0.25,mm, 0.25,µm film thickness). [source] Simplification of separation of the reaction mixture after transesterification of vegetable oilEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 4 2008Martin Hájek Abstract A heterogeneous reaction mixture is formed by transesterification of vegetable oils. The reaction mixture contains mainly methyl esters of higher fatty acids and glycerol. From this mixture, biodiesel is gained by spontaneous sedimentation in the gravitational field. The sedimentation can be considerably accelerated by controlled addition of water. It was found that addition of small amounts of water to the crude reaction mixture significantly affected the mixture, and substantial changes in the speed of the separation took place. Considerable differences in the composition and quality of the ester and glycerol phases occurred. The optical properties (transmittance and refractive indices) of the heterogeneous reaction mixture are changed after addition of water; this change can be observed spectrophotometrically. This method is applicable to all types of vegetable oils including waste frying oils. [source] Functionalized Poly(D,L -lactide) for Pulmonary Epithelial Cell CultureADVANCED ENGINEERING MATERIALS, Issue 4 2010Yuan-Min Lin Functional groups on a material surface affect the response of many cell types. As part of our strategy aimed at engineering lung tissue, we introduced functional groups into the surface of Poly(D,L -lactide) (PDLLA) films to improve its suitability for the culture of mature pulmonary epithelial cells (A549 line) using two different methods. The first method, aminolysis, can introduce primary amines into PDLLA films by transesterification using 1,15% of ethylenediamine in isopropanol. The second method, a branching modification, can generate amine-terminated or carboxylic acid-terminated tree-like branched architectures. All modified PDLLA surfaces exhibited lower water contact angles, i.e. are more hydrophilic than unmodified PDLLA. PDLLA treated with 15% ethylenediamine exhibited a rougher surface than the control, and PDLLA with branching modification had a droplet-like surface topography as visualized by atomic force microscopy (AFM). PDLLA treated with 15% ethylenediamine and branching modification with two and three generations enhanced the attachment of pulmonary epithelial cells measured using Hoechst dye. Immunostaining demonsatrated that amine-terminated branched architectures allowed for better focal adhesion point formation than the control 24,h after cell seeding. Furthermore, they also induced higher A549 cell populations and levels of activity after 4 days in culture measured using Hoechst dye and WST1 cell proliferation reagents, respectively. In contrast, carboxylic acid-terminated branching architectures were found to reduce the cell population size after 4 days. It was concluded that the concentration, type and distribution of surface functional groups can affect significantly the behavior of pulmonary epithelial cells growing on a PDLLA surface, and PDLLA film modified with two or three generations of amine-terminated branched architectures is a suitable 2D scaffold for the culture of of pulmonary epithelial cells. [source] Silylation-Mediated Transesterification of O -Phenyl H-Phosphonothioates , A New Entry to Nucleoside H-Phosphonothioate MonoestersEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 24 2004Gaston Lavén Abstract O -Phenyl H-phosphonothioate undergoes a facile transesterification with suitably protected nucleosides upon in situ silylation with tert -butyldiphenylsilyl chloride in pyridine/ toluene to produce the corresponding 3,-H-phosphonothioates in good yields. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Biodiesel fuel production via transesterification of oils using lipase biocatalystGCB BIOENERGY, Issue 2 2009MAN XIAO Abstract Biodiesel has gained widespread importance in recent years as an alternative, renewable liquid transportation fuel. It is derived from natural triglycerides in the presence of an alcohol and an alkali catalyst via a transesterification reaction. To date, transesterification based on the use of chemical catalysts has been predominant for biodiesel production at the industrial scale due to its high conversion efficiency at reasonable cost. Recently, biocatalytic transesterification has received considerable attention due to its favorable conversion rate and relatively simple downstream processing demands for the recovery of by-products and purification of biodiesel. Biocatalysis of the transesterification reaction using commercially purified lipase represents a major cost constraint. However, more cost-effective techniques based on the immobilization of both extracellular and intracellular lipases on support materials facilitate the reusability of the catalyst. Other variables, including the presence of alcohol, glycerol and the activity of water can profoundly affect lipase activity and stability during the reaction. This review evaluates the current status for lipase biocatalyst-mediated production of biodiesel, and identifies the key parameters affecting lipase activity and stability. Pioneer studies on reactor-based lipase conversion of triglycerides are presented. [source] Novel routes to aminophosphonic acids: Interaction of dimethyl H-phosphonate with hydroxyalkyl carbamatesHETEROATOM CHEMISTRY, Issue 2 2008K. Troev It was found that the reaction of dimethyl H-phosphonate (1) with 2-hydroxyalkyl- N -2,-hydroxyalkyl carbamates at 135°C includes several chemical reaction steps: (i) chemical transformations of 1-methyl-2-hydroxyethyl- N -2,-hydroxyethyl carbamate (2) and 2-methyl-2-hydroxyethyl- N -2,-hydroxyethyl carbamate (3); (ii) transesterification of dimethyl H -phosphonate with 2 and 3, and with secondary hydroxyl-containing compounds that are formed during the course of the chemical transformation of 2-hydroxyalkyl- N -2,-hydroxyalkyl carbamates; (iii) hydrolysis of 1 and dialkyl H-phosphonates, formed via transesterification of 1 with secondary hydroxyl-containing compounds. The interaction was studied by means of 1H, 13C, 31P NMR, and FAB mass spectroscopy. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:119,124, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20404 [source] Kinetic study of transesterification of methyl acetate with n -butanol catalyzed by NKC-9INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 2 2009Baoyun Xu The transesterification of methyl acetate and n -butanol catalyzed by cation-exchange resin, NKC-9, was studied in this work to obtain the reaction kinetics. The experiments were carried out in a stirred batch reactor at different temperatures (328.15, 333.15, 338.15, 343.15, 345.15 K) under atmospheric pressure. The effects of temperature, molar ratio of reactants, and catalyst loading on the reaction rate were researched under the condition of eliminating the effect of diffusion. The experimental data were correlated with a kinetic model based on the pseudo-homogeneous catalysis. The kinetic equation describing the reaction catalyzed by NKC-9 was developed. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 41: 101,106, 2009 [source] Production of zero trans Iranian vanaspati using chemical transesterification and blending techniques from palm olein, rapeseed and sunflower oilsINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 3 2008Jamshid Farmani Summary Chemical transesterification and blending techniques were used for producing zero trans fats suitable for use as Iranian vanaspati. Triple blends of palm olein (POo), rapeseed (RSO) and sunflower oil (SFO) were subjected to two different treatments: (i) blending and then transesterification (BT) and (ii) transesterification of pure POo before blending with RSO and SFO (TB). The changes in slip melting point (SMP), solid fat content (SFC), carbon number (CN) triacylglycerol (TAG) composition, induction period (IP) of oxidation at 120 °C and IP of crystallisation at 20 °C of blends before and after treatments were investigated. Both BT and TB methods resulted in an increase in the CN48 TAG molecules, SMP and SFC, and a decrease in the IP of oxidation and crystallisation of initial blends. Samples made by TB method had higher CN48 TAG content, SMP, SFC and IP of oxidation, and lower IP of crystallisation than those made by BT method. Correlation between SFC at 20 °C and saturated fatty acid (SFA) content of the treated blends indicated that the SFA must be higher than 33.1% and 26.8% for BT and TB methods, respectively, to obtain fats suitable for use as vanaspati. [source] Imidazolium-2-Carboxylate as an Efficient, Expeditious and Eco-Friendly Organocatalyst for Glycerol Carbonate SynthesisADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2009Prashant Abstract An improved and greener approach towards the synthesis of glycerol carbonate, via transesterification, using 1- n -butyl-3-methylimidazolium-2-carboxylate as catalyst is described. The catalyst loading as low as 1% was sufficient to yield quantitative conversions. A plausible mechanism is proposed for the catalytic cycle leading to product formation. [source] Bioreactors Based on Monolith-Supported Ionic Liquid Phase for Enzyme Catalysis in Supercritical Carbon DioxideADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 7 2007Pedro Lozano Abstract Bioreactors with covalently supported ionic liquid phases (SILP) were prepared as polymeric monoliths based on styrene,divinylbenzene or 2-hydroxyethyl methacrylate,ethylene dimethacrylate, and with imidazolium units loadings ranging from 54.7 to 39.8,% wt IL per gram of polymer. The SILPs were able to absorb Candida antarctica lipase B (CALB), leading to highly efficient and robust heterogeneous biocatalysts. The bioreactors were prepared as macroporous monolithic mini-flow systems and tested for the continuous flow synthesis of citronellyl propionate in supercritical carbon dioxide (scCO2) by transesterification. The catalytic activity of these mini-flow-bioreactors remained practically unchanged for seven operational cycles of 5,h each in different supercritical conditions. The best results were obtained when the most hydrophobic monolith, M-SILP- 8 -CALB, was assayed at 80,°C and 10,MPa, reaching a total turnover number (TON) of 35.8×104 mol product/mol enzyme. The results substantially exceeded those obtained for packed-bed reactors with supported silica-CALB-Si-4 catalyst under the same experimental conditions. [source] | |||||||||||||||||||||||||||||||