Showing papers on "Transesterification published in 1985"

Enzyme-catalyzed processes in organic solvents.

Abstract: Three different lipases (porcine pancreatic, yeast, and mold) can vigorously act as catalysts in a number of nearly anhydrous organic solvents Various transesterification reactions catalyzed by porcine pancreatic lipase in hexane obey Michaelis-Menten kinetics The dependence of the catalytic activity of the enzyme in organic media on the pH of the aqueous solution from which it was recovered is bell-shaped, with the maximum coinciding with the pH optimum of the enzymatic activity in water The catalytic power exhibited by the lipases in organic solvents is comparable to that displayed in water In addition to transesterification, lipases can catalyze several other processes in organic media including esterification, aminolysis, acyl exchange, thiotransesterification, and oximolysis; some of these reactions proceed to an appreciable extent only in nonaqueous solvents

A comparison of conventional and in situ methods of transesterification of seed oil from a series of sunflower cultivars

Abstract: The cost of vegetable oil monoesters represents one of the major restrictions on their use as an alternative fuel for diesel engines. This cost can be reduced by increasing the yield of esters produced from a given quantity of oilseed.

Transesterification in situ of sunflower seed oil

Abstract: Transesterification of sunflower seed oil in situ has produced methyl and ethyl esters in yields greater than 40% of the dry seed weight. This figure compares with a typical yield of ca. 30% when the esters were prepared in the conventional manner from preextracted seed oil. 14 references.

Preparative regioselective acylation of glycols by enzymatic transesterification in organic solvents

Abstract: Porcine pancreatic lipase can catalyze transesterification reac tions in organic solvents in a highly regioselective manner. Lipase powder was suspended in solutions of various diols in ethyl carboxylates, and the mixtures were shaken at 30°C; as a result, pri mary monoesters of glycols were produced on a preparative scale.

Production of sucrose fatty acid polyester

Abstract: Sucrose fatty acid polyesters are produced by heating a molten mixture of sucrose, fatty acid lower alkyl ester, transesterification catalyst, fatty acid alkali metal soap and/or sucrose fatty acid ester. Sucrose fatty acid polyesters are purified by acidifying the reaction product and subjecting the acidified reaction product to molecular distillation whereby the sucrose fatty acid polyesters are recovered as the residue.

Process for the production of fatty acid alkyl esters

Abstract: Fatty acid alkyl esters are produced by catalytic transesterification of natural fats and oils containing free fatty acids. In a preliminary esterifying step, the free fatty acids present are reacted with a C1 -C4 alkanol (e.g., methanol) in the presence of an acidic esterification catalyst, at a temperature of about 50° to 120° C. and at substantially atmospheric pressure. The resulting reaction mixture is allowed to separate into two phases: (1) an alcohol phase containing the acidic esterification catalyst and part of the water of reaction and (2) an oil phase. These phases separately recovered. The oil phase is then extracted with an immiscible extractant, preferably comprising a mixture of glycerol and methanol, to remove residual water of reaction. In the final step the extracted oil phase is transesterified with a C1 -C4 alkanol, e.g. methanol, in the presence of an aklali catalyst and at substantially atmospheric pressure.

Method for preparing esters of acrylic acid and methacrylic acid by transesterification

Abstract: A method of preparing an ester of (meth)acrylic acid by transesterification with an alcohol, comprising, reacting a (meth)acrylic acid ester formed from an alcohol of 1 to 4 carbon atoms with a transesterifying alcohol, which is not a polybasic alcohol and which is different from the alcohol portion of said (meth)acrylic acid ester, in the presence of a catalyst system comprised of compounds A+B, wherein compound A is Li n Y, wherein Y is a halide, chlorate, carbonate, carboxylate of 1 to 6 carbon atoms, an alkoxide of 1 to 4 carbon atoms, hydroxide or oxide, and n is 1 or 2, depending on the valence of Y; and compound B is CaX q , wherein X is oxide or chloride and q is 1 or 2, depending on the valence of X, with the provision that at least one of the two anionic components Y and X is oxygen-containing.

Process for the production of fatty acid esters of short-chain alcohols

Abstract: A process for the preparation of fatty acid esters of short-chain primary and secondary alcohols with 1 to 5 carbon atoms by transesterification of glycerides with the said short-chain alcohols is described. In this process, a stream of the gaseous alcohol is passed through the liquid glyceride at temperatures of at least 210° C. and the product mixture of gylcerol and fatty acid alkyl ester is discharged from the reaction zone with this stream and is then subjected to phase separation.

Study of step-growth polymerizations using epoxy-carboxy reaction

Abstract: Due to its importance in the fields of block-polycondensation and chemical modification, we carried out a study of the epoxy-carboxy reaction on models (3-phenoxy-1,2-epoxy propane and dodecanoic acid) in the bulk; this reaction was catalyzed either by a tertiary amine (N,N-dimethyldodecylamine) or a chromium chelate (chromium diisopropylsalicylate). Whatever the catalytic system we observed an isomerization of the hydroxy-ester (secondary-primary alcohol) plus transesterification reactions when the catalyst was an amine. The contribution of transesterification reactions is limited when the catalyst is a chromium derivative.

Acid catalyzed organic reactions

Abstract: Certain urea-sulfuric acid components, comprised of urea and sulfuric acid in a 1/4 to 7/4 molar ratio, contain a monourea adduct of sulfuric acid, which is catalytically active for promoting organic chemical reactions. The invention provides methods employing such urea-sulfuric acid components for catalyzing organic reactions such as oxidation, oxidative addition, reduction, reductive addition, esterification, transesterification, hydrogenation, isomerization (including racemization of optical isomers), alkylation, polymerization, demetallization of organometallics, nitration, Friedel-Crafts reactions, and hydrolysis. Novel catalysts are disclosed which involve combinations of the urea-sulfuric component with one or more transition metal halides and/or with one or more surfactants. The surfactant-containing compositions are particularly useful for the treatment of materials containing lipophilic substances. Novel compositions containing the urea-sulfuric acid component and one or more organic reactants are also disclosed.

Mixed polyester molding compositions

Abstract: Mixed polyester molding compositions comprising at least a pair of structurally different thermoplastic polyesters are stabilized against transesterification, whether during formulation or the downstream molding thereof, by having incorporated therein an effective amount of at least one mono-, di- or triester of orthophosphoric acid.

Electrogenerated acid as an efficient catalyst for the protection and deprotection of alcohols with dihydropyran and transesterification of glyceride

Abstract: Protection of alcohols with 3,4-dihydro-2H-pyran and hydrolysis of the resulting tetrahydropyranyl ethers are cleanly performed by using an electrogenerated acid (EG acid) as a catalyst. Transesterification of glyceride was also achieved with EG acid.

Stimulation of peptidyltransferase reactions by a soluble protein

Abstract: The requirements for peptide-bond synthesis and transesterification reactions of Escherichia coli 70S ribosomes, 50S native or reconstructed 50S subunits were examined using fMet-tRNA as donor substrate and puromycin or alpha-hydroxypuromycin as acceptors. We report that the soluble protein EF-P, purified to apparent homogeneity, stimulates the synthesis of N-formylmethionylpuromycin or N-formylmethionylhydroxypuromycin by 70S ribosomes or reassociated 30S and 50S subunits. In the presence of EF-P, 70S ribosomes are significantly more efficient than 50S particles in catalysing either peptide-bond synthesis or transesterification. The involvement of 50S subunit proteins in EF-P-stimulated peptide-bond formation and transesterification was studied. 50S subunits were dissociated by 2.0 M LiCl into core particles and 'split' proteins, several of which were purified to homogeneity. When added to 30S X A-U-G X f[35S]Met-tRNA, 50S cores or 50S cores reconstituted with L6 or L11 promoted peptide-bond synthesis or transesterification poorly. EF-P stimulated peptide-bond synthesis by both these types of core particles to approximately the same extent. On the other hand, EF-P stimulated a low level of transesterification by cores reconstituted with L6 and L11. In contrast, core particles reconstituted with L16 exhibited both peptide-bond-forming and transesterification activities and EF-P stimulated both reactions twentyfold and fortyfold respectively. Thus different proteins differentially stimulate the intrinsic or EF-P-stimulated peptide-bond and transesterification reactions of the peptidyl transferase. Ethoxyformylation of either 50S subunits or purified L16 used to reconstitute core particles, resulted in loss of peptide-bond formation and transesterification. Similarly ethoxyformylation of EF-P resulted in a 25-50% loss of its ability to stimulate both reactions. 30S subunits were resistant to treatment by this reagent. These results suggest the involvement of histidine residues in peptidyltransferase activities. The role of EF-P in the catalytic mechanism of peptidyltransferase is discussed.

Process for the production of dianhydrohexitol mixtures and the production of polymers from such mixtures

Abstract: Liquid dianhydrohexitol mixtures are prepared from diacylation products of hexitols and compounds such as organic carboxylic acids, carboxylic acid anhydrides, carboxylic acid halides, ketene and carbonic acid ester derivatives. More specifically, such diacylation products are simultaneously dehydrated and isomerized by subjecting them to a temperature of at least 130° C. in the presence of a strong acid to yield diacylated dianhydro-hexitol isomer mixtures. These isomer mixtures are then converted to dianhydro-hexitol isomer mixtures by hydrolysis or transesterification. Suitable strong acids include proton acids, Lewis acids and heterogeneous acid catalysts (e.g., ion exchange resins). The mixtures of the present invention are characterized by a minimal tendency towards crystallization. These mixtures are particularly useful as chain extending agents in the production of polyurethanes.

Study of Exchange-reactions in Polycarbonate Polyarylcarboxylate Mixtures With Model Compounds

Abstract: The exchange reaction between a polycarbonate and a polyarylcarboxylate, both based on bisphenol A, was simulated by studying the reaction between the polycarbonate and diphenyl terephthalate or isophthalate used as model compounds of a polyarylcarboxylate. The kinetic results indicate the presence of a transesterification reaction occurring without any catalyst. Some results from reactions in the melt between both polymers also point to an exchange reaction.

Carboxylic acid esterification

Abstract: A process for the esterification of carboxylic acids such as free fatty acids present in palm oil or palm oil fractions comprises refluxing a mixture of the carboxylic acid with an alcohol in the presence of solid ammonium bisulphate which is then removable by filtration. The process has particular application to the esterification of the free fatty acid content of a mixture of free fatty acids and glycerides followed by transesterification of the glycerides using an alkaline catalyst.

Process for the polymerization of polyester-carbonates

Abstract: @ A novel process is described for the preparation of a polyester-carbonate by transesterification at temperatures in excess of the melting point of the reaction mixture.

Process for transesterification of carbonate esters and carboxylic acid esters using a cyclic amidine catalyst

Abstract: A process is provided for the transesterification of carbonate esters and carboxylic acid esters at elevated temperatures and in the presence of an effective amount of an amidine compound.

The p-Phenylazophenyloxycarbonyl Protecting Group: Selective Deblocking and Oligonucleotide Synthesis Avoiding Acid Steps

Abstract: The p-phenylazophenyloxycarbonyl group is selectively introduced at nucleoside-5′-OH by reaction with the resp. chloroformate and deblocked e.g. by transesterification/β-elimination. With it we designed a reaction cycle for oligonucleotide support synthesis, that avoids acid deprotection.

Transesterification of carboxylic or carbonic esters

Abstract: A process for the transesterification of a carboxylic or carbonic acid ester comprises reacting the carboxylic or carbonic acid ester under transesterification conditions with an alcohol in the presence, as catalyst, of either (i) a Group V element-containing Lewis base and an epoxide or (ii) a cyclic amidine. The Lewis base can be an organic compound containing trivalent phosphorus or nitrogen and can be an amine, for example an amidine. The process can be operated in the liquid phase at a temperature of from 15° to 150° C., and the catalyst is employed in solution. Preferred catalysts are those where the cyclic amidine forms part of a fused ring system containing six and five membered rings, six and seven membered rings or two six membered rings.

Kinetics of transesterification of dimethylene terephthalate with ethylene glycol

Abstract: There is a disagreement about the order of reaction of transesterification of DMT with EG. The reactivity of the two ester groups is not compared yet. The transesterification of DMT and MHET is studied to establish the kinetics of the process. Attempts are made to treat the kinetic data on a mathematical model for third-order reaction.

On the transesterification of dialkyl and diaryl phosphites with some amino alcohols and synthesis of polyurethanes

Abstract: The transesterification reaction of dialkyl and diaryl phosphites with triethanolamine, N-methyldiethanolamine and diethanolamine was examined. The transesterification process with aminoalcohols begins at considerably lower temperatures than that with aliphatic diols. A probable mechanism of the transesterification of dialkyl and diaryl phosphites with amino alcohols is suggested. Phosphorus-containing polyurethanes are obtained by using N,N-diethanolaminoethyl phosphite.

Aqueous electrodip-lacquering coating composition and its use in coating objects

Abstract: 1. Aqueous electrocoating composition which comprises an organic resin binder, water-dilutable as a result of protonization by acids and containing an organic amine-containing resin component and a crosslinking agent, which composition further comprises catalysts for the thermal crosslinking and, optionally, pigments, fillers, corrosion inhibitors, conventional paint auxiliary agents and organic solvents in an amounts of up to 20% by weight based on the total weight of the composition, characterized in that the composition contains as the binder : (A) 95 to 50% by weight, based on the total amount of the binder, of an organic non-self-crosslinking resin binder with a hydroxyl value of 50 to 400, an amine value of 30 to 150 and an average molecular mass (~Mn) from about 250 to 10,000, containing primar and/or secondary hydroxyl groups and primary, secondary and/or tertiary amino groups, and (B) 5 to 50% by weight of a mixture of crosslinking agents from (a) blocked polyisocyanates and (b) crosslinking agents capable of transesterification having at least two ester groups per molecule, which are largely stable in a neutral aqueous medium and yet in a basic medium at temperatures of above 140 degrees C are capable of transamination and/or transesterification with the component (A), (a) and (b) being present in a ratio of from 1:20 to 20:1 parts by weight, and (C) optionally, up to 30% by weight based on the total weight of the components (A) and (B), of hydroxylic resins with a hydroxyl value of from 30 to 500 and an average molecular mass (~Mn) of from 300 to 5000.