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Showing papers on "Transesterification published in 1992"


Journal ArticleDOI
TL;DR: Transesterification activity increases and then decreases with increasing enzyme hydration and flexibility (which are presumably coupled through dielectric screening), suggesting that the conformation of partially hydrated subtilisin is different from that of the nearly dry enzyme--i.e., enzyme containing less than 9% water.
Abstract: Enzymes suspended in organic solvents represent a versatile system for studying the involvement of water in enzyme structure and function. Addition of less than 1% (vol/vol) water to tetrahydrofuran containing 1 M 1-propanol leads to a substantial increase in the transesterification activity of subtilisin Carlsberg (from Bacillus licheniformis) that correlates with a sharp increase in the active-site polarity and a 90% decrease in the rotational correlation time (i.e., increase in mobility) of a nitroxide spin label within the active site. Water in excess of 1% has little additional effect on active-site polarity and coincides with a further increase in spin-label mobility, yet the transesterification activity decreases dramatically. Thus, transesterification activity increases and then decreases with increasing enzyme hydration and flexibility (which are presumably coupled through dielectric screening), suggesting that the conformation of partially hydrated subtilisin is different from that of the nearly dry enzyme--i.e., enzyme containing less than 9% (wt/wt) water.

236 citations


Patent
23 Mar 1992
TL;DR: In this paper, a method for preparing polyolefins is described, in which a procatalyst composition is used, which has been prepared by contacting MgCI2, a lower alcohol, a titanium compound and a phthalic acid ester.
Abstract: The invention relates to a method for preparing polyolefins. In the polymerization, a procatalyst composition is being used, which has been prepared by contacting MgCI2, a lower alcohol, a titanium compound and a phthalic acid ester. The po-lyolefin is given the adequate coarseness by using a pracatalyst of the said type, which has been prepared by carrying out a transesterification between the lower alcohol and the phthalic acid ester and by selecting dioctyl phthalate (DOP) as phthal-ic acid ester.

228 citations


Journal ArticleDOI
TL;DR: Experimental observations clearly indicate that the substrates as well as the product (ethanol) act as dead-end inhibitors and a ping-pong bi-bi mechanism with competitive inhibition by substrates and products is proposed that predicts the experimental observation satisfactorily.

146 citations


Journal ArticleDOI
TL;DR: The kinetics of reaction are suggested to agree with a ping-pong Bi Bi mechanism in which inhibition by excess of geraniol has been identified.

146 citations


Journal ArticleDOI
TL;DR: In this article, the enantiomeric ratio of porcine pancreatic lipase and Lipase PS in transesterification between trifluoroethyl butanoate and the two unrelated alcohols (±)-sulcatol (1 ) and 3-bromo-5-hydroxymethyl isoxazoline (2 ).
Abstract: The nature of organic solvents markedly influenced the enantioselectivity, expressed as the enantiomeric ratio, of porcine pancreatic lipase and of Lipase PS in transesterification between trifluoroethyl butanoate and the two unrelated alcohols (±)-sulcatol ( 1 ) and (±)-3-bromo-5-hydroxymethyl isoxazoline ( 2 ). However, there was no correlation between enantioselectivity and such physicochemical characteristics of the solvent as hydrophobicity and dielectric constant. A rationale based on the formation of solvent-enzyme complexes is proposed to explain the results. Enzyme enantioselectivity was also affected by temperature but not by the chain length of the acylating agent nor by the removal of water from the reaction medium by molecular sieves. The effects of these parameters on transesterification rates were also investigated.

138 citations


Journal Article
TL;DR: Observations demonstrate that the transesterification of cocaine in the presence of ethanol is probably the result of hepatic and possibly renal carboxylesterases localized in the endoplasmic reticulum.
Abstract: The enzyme-mediated transesterification of the 2-carboxymethyl ester of cocaine to a 2-carboxyethyl ester in the presence of ethanol has been characterized in mice by using both in vitro and in vivo systems. Hepatic subcellular fractionation of mouse livers demonstrated that cocaine transesterification activity was detectable only in the microsomal fraction. The in vitro microsomal transesterification of cocaine in the presence of ethanol was inhibited by fluoride and diisopropylfluorophosphate but was insensitive to physostigmine, thereby indicating that the reaction is specifically catalyzed by a carboxylesterase. The transesterification activity of hepatic microsomes showed saturable Michaelis-Menten kinetics in the presence of increasing concentrations of ethanol or cocaine. Cocaine transesterification specific activity in isolated mouse kidney microsomes was approximately 1.5-fold greater than that measured in the liver, suggesting that the kidney could play a significant role in ethyl ester formation. Collectively, these observations demonstrate that the transesterification of cocaine in the presence of ethanol is probably the result of hepatic and possibly renal carboxylesterases localized in the endoplasmic reticulum. The ethyl ester of cocaine was also detected in the livers of mice coadministered ethanol (3.0 g/kg intragastrically) and cocaine (50 mg/kg i.p.). Cocaine and cocaine ethyl ester displayed similar pharmacokinetic profiles, with hepatic half-lives of approximately 6.5 min. Pretreatment of the mice with 100 mg/kg tri-o-tolylphosphate completely blocked in vivo formation of the ethyl ester metabolite, further supporting the involvement of B-esterases in the transesterification of cocaine to cocaine ethyl ester.

125 citations


Patent
11 Jun 1992
TL;DR: In this article, an enzymatic transesterification method for preparing a margarine oil having both low trans- acid and low intermediate chain fatty acid content is disclosed, which includes the steps of providing a reaction mixture containing a stearic acid source material and an edible liquid vegetable oil.
Abstract: An enzymatic transesterification method for preparing a margarine oil having both low trans- acid and low intermediate chain fatty acid content is disclosed. The method includes the steps of providing a transesterification reaction mixture containing a stearic acid source material and an edible liquid vegetable oil, transesterifying the stearic acid source material and the vegetable oil using a 1-, 3-positionally specific lipase, and then finally hydrogenating the fatty acid mixture to provide a recycle stearic acid source material for a recyclic reaction with the vegetable oil. Also described is a counter-current method for preparing a transesterified oil. The method includes the steps of providing a transesterification reaction zone containing a 1-, 3-positionally specific lipase, introducing a vegetable oil into the transesterification zone, introducing a stearic acid source material, conducting a supercritical gas or subcritical liquified gas counter-current fluid, carrying out a transesterification reaction of the triglyceride stream with the stearic acid or stearic acid monoester stream in the reaction zone, withdrawing a transesterified triglyceride margarine oil stream, withdrawing a counter-current fluid phase, hydrogenating the transesterified stearic acid or stearic acid monoester to provide a hydrogenated recycle stearic acid source material, and introducing the hydrogenated recycle stearic acid source material into the reaction zone.

123 citations


Journal ArticleDOI
TL;DR: It is demonstrated that supercritical carbon dioxide is not a good solvent for the reaction between 2‐ethlhexanol and methylmethacrylate, and sulfur hexafluoride, the first anhydrous inorganic solvent in which biocatalytic activity has been reported, is a better solvent than any conventional or supercritical organic fluid tested.
Abstract: Biocatalytic transesterification of methylmethacrylate is possible in many different solvents. The reaction rate is readily controlled by variation in solvent physical properties. The reaction proceeds better in hydrophobic solvents, and activity can be restored in hydrophilic solvents by the addition of water. We have now demonstrated that supercritical carbon dioxide is not a good solvent for the reaction between 2-ethlhexanol and methylmethacrylate. It appearance that the supercritical carbon dioxide may either alter the pH of the microaqueous environment associated with the protein or reversibly form covalent complexes with free amine groups on the surface of the enzyme. Although supercritical carbon dioxide is a poor solvent for acrylate transesterification, many other supercritical fluids (ethane, ethylene, sulfur hexafluoride, and fluoroform) are better than most conventional solvents. In supercritical ethane it is possible to control the activity of the enzyme by changing pressure, and the enzyme appears to follow Michaelis-Menten Kinetics. We find that sulfur hexafluoride, the first anhydrous inorganic solvent in which biocatalytic activity has been reported, is a better solvent than any conventional or supercritical organic fluid tested.

122 citations


Journal ArticleDOI
TL;DR: In this paper, the synthesis of poly(methyl 6-acryloyl-β-galatoside) with M w =196 000 and M n =58 000 for a polydispersity of 2.9 which was highly water soluble and soluble in polar organic solvents.
Abstract: The lipase from Pseudomonas cepacia catalyzed the transesterification of a variety of monosaccharides with vinyl acrylate in pyridine to give the 6-acryloyl esters. The acrylate esters were polymerized in DMF with AIBN to give the poly(acrylate) products. Such a synthetic strategy has led to the synthesis of poly(methyl 6-acryloyl-β-galatoside) with M w =196 000 and M n =58 000 for a polydispersity of 2.9 which was highly water soluble and soluble in polar organic solvents. Addition of ethylene glycol dimethacrylate during AIBN-initiated polymerization in DMF resulted in water insoluble polymrs that swelled in aqueous solutions

98 citations


Journal ArticleDOI
TL;DR: Porcine pancreatic lipase and Fusarium solani cutinase were used to catalyze transesterification reactions between methyl propionates, ethyl propionate, and a series of primary alcohols at high temperatures in a continuous packed-bed gas-solid reactor.
Abstract: Many products which are useful in the fine chemical, flavor, and petrochemical industries are insoluble in an aqueous phase. An obvious solution is the use of organic solvents for the solubilization of such com- poUnds~~.l~,11.~9-21 However, even if the organic solvents truly solubilize these products, they may act as dena- turants for biocatalyst a~tivity.~ Intermediate possibili- ties can be sought, such as the use of mixed aqueous- organic media, emulsions, or microemulsions.’3-’s This article describes the use of a new, original tech- nology based on the implementation of a continuous gas-solid bioreactor, in which the biocatalyst (used as a lyophilized powder) is the solid phase and the substrates are gaseous. The temperature of reactor operation depends on the particular enzymes and substrates. This type of biore- actor presents many advantages: It is a continuous reactor; substrates continuously en- ter the reactor and products continuously leave the reactor. The substrates are pure; there is no addition

96 citations


Patent
29 Oct 1992
TL;DR: In this paper, a transesterifying admixture of dimethyl terephthalate, dimethyl sulfoaryl dicarboxylate and ethylene glycol is introduced, and the resulting product of transesterification/direct esterification is polycondensed.
Abstract: Hydrosoluble/hydrodispersible polyester copolycondensates, well suited for the sizing of textile threads, comprise terephthalate, isophthalate, sulfoaryl dicarboxylate, ethylene glycol and polyoxyethylene glycol recurring structural units, have a glass transition temperature ranging from 15° to 40° C. at 85% relative humidity and the turbidity of aqueous formulations thereof are storage-stable over time; such polyester copolycondensates are conveniently prepared by (i) transesterifying admixture of dimethyl terephthalate, dimethyl sulfoaryl dicarboxylate and ethylene glycol, (ii) introducing isophthalic acid and an additional amount of ethylene glycol into the medium of transesterification and therein directly esterifying same, and (iii) polycondensing the resulting product of transesterification/direct esterification.

Patent
23 Mar 1992
TL;DR: In this paper, a method for the preparation of polyolefins by polymerizing olefin by using a procatalyst composi-tion prepared by bringing together magnesium chloride, a lower alcohol, a titanium compound, and phthalic acid ester.
Abstract: The invention relates to a method for the preparation of polyolefins by polymerizing olefin by using a procatalyst composi-tion prepared by bringing together magnesium chloride, a lower alcohol, a titanium compound, and phthalic acid ester. The in-vention also relates to the said procatalyst composition. The invention has succeeded in lowering the concentrations of titanium and phthalic acid ester in the catalyst, and thereby also in the polyolefin, and at the same time in preparing large-pore polyolefin, which is important for certain purposes. These properties have been obtained by using a procatalyst of the said type, in the pre-paration of which a transesterification has been performed between the lower alcohol and the phthalic acid ester, and the phthalic acid ester selected for the transesterification is one the alkoxy group of which has at minimum 10 carbon atoms.

Journal ArticleDOI
TL;DR: By using a large excess of the free fatty acid (heptadecanoic acid), the hydrolysis reaction was slowed down, so a higher yield was obtained at a given degree of incorporation, and the enzyme preparation had good operational stability and position specificity.
Abstract: The incorporation of a free fatty acid into thesn-1 position of phosphatidylcholine by lipase-catalyzed transesterification was investigated. The thermodynamic water activity of both the enzyme preparation and the substrate solution was adjusted to the same value prior to the reaction. The reaction rate increased with increasing water activity but the yield of modified phosphatidylcholine decreased due to hydrolysis. By using a large excess of the free fatty acid (heptadecanoic acid), the hydrolysis reaction was slowed down, so a higher yield was obtained at a given degree of incorporation. The best results were obtained withRhizopus arrhizus lipase immobilized by adsorption on a polypropylene support. With this preparation, a yield of 60% and nearly 50% incorporation of heptadecanoic acid (100% incorporation in thesn-1 position) was obtained at a water activity of 0.064. The enzyme preparation had good operational stability and position specificity. Little incorporation (<1%) was observed in thesn-2 position, when almost all the fatty acid in thesn-1 position was exchanged.

Journal ArticleDOI
TL;DR: By using the hydrophilic alginate gel as an immobilization matrix in combination with a mobile hydrophobic phase, a two-phase liquid system was achieved with definite advantages for a continuous, enzyme-catalysed process.

Journal ArticleDOI
TL;DR: The transesterification of the 2-(4-nitrophenyl phosphate) ester of propylene glycol (1) was promoted by La 3+, Nd 3+, Eu 3+, Gd 3+, Tb 3+, and Ca 2+ at 37 o C in 0.01 M Hepes ethyl)piperazine-N'-ethanesulfonic acid.
Abstract: The transesterification of the 2-(4-nitrophenyl phosphate) ester of propylene glycol (1) was promoted by La 3+ , Nd 3+ , Eu 3+ , Gd 3+ , Tb 3+ , Yb 3+ , Lu 3+ , Pb 2+ , Zn 2+ , Cu 2+ , Ni 2+ , Co 2+ , Mn 2+ , Mg 2+ , and Ca 2+ at 37 o C in 0.01 M Hepes ethyl)piperazine-N'-ethanesulfonic acid), pH 6.85

Journal Article
01 Jan 1992-Scopus
TL;DR: The transesterification of the 2-(4-nitrophenyl phosphate) ester of propylene glycol (1) was promoted by La 3+, Nd 3+, Eu 3+, Gd 3+, Tb 3+, and Ca 2+ at 37 o C in 0.01 M Hepes ethyl)piperazine-N'-ethanesulfonic acid as mentioned in this paper.
Abstract: The transesterification of the 2-(4-nitrophenyl phosphate) ester of propylene glycol (1) was promoted by La 3+ , Nd 3+ , Eu 3+ , Gd 3+ , Tb 3+ , Yb 3+ , Lu 3+ , Pb 2+ , Zn 2+ , Cu 2+ , Ni 2+ , Co 2+ , Mn 2+ , Mg 2+ , and Ca 2+ at 37 o C in 0.01 M Hepes ethyl)piperazine-N'-ethanesulfonic acid), pH 6.85


Journal ArticleDOI
TL;DR: Very high enantiomeric ratios (E≥45) were observed in substrates 1 bearing short (R=Me or Et) and the enantioselectivity of the process was little influenced by the nature of the R chain.
Abstract: Lipase PS (from Pseudomonas cepacia) catalyzed the enantioselective transesterification of racenic γ-hydroxy- α,β-unsaturated phenyl sulfones 1 and their α,β-saturated derivatives 3 with vinyl acetate in an organic solvent (usually i Pr 2 O). Remarkably, in substrates 1 with (E)-stereochemistry, the enantioselectivity of the process was little influenced by the nature of the R chain. Hence, very high enantiomeric ratios (E≥45) were observed in substrates 1 bearing short (R=Me or Et)

Journal ArticleDOI
TL;DR: The detailed information generated indicates that once the substrate has bound to the enzyme, the catalytic machinery can work at rates equivalent to those in water, which will enable a clearer understanding of how changing solvent can predictably affect the activity and specificity of the enzyme.
Abstract: We report here the first determinations of individual rate constants and equilibrium constants for enzymatic reactions in essentially anhydrous organic solvents. Using the added nucleophile method we have measured the effect of changing solvent on the binding and catalytic steps for subtilisin-catalyzed transesterification of N-protected amino acid esters. The detailed information generated indicates that once the substrate has bound to the enzyme, the catalytic machinery can work at rates equivalent to those in water. The decreased overall rates for subtilisin suspended in anhydrous solvents are merely the result of extremely high values for Ks, in most cases, coupled with low concentrations of nucleophile (∼1.0M in organic solvents, and 55M in water). The method described, which is generally applicable, and straightforward experimentally, will, we believe, enable a clearer understanding of how changing solvent can predictably affect the activity and specificity of the enzyme. © 1992 John Wiley & Sons, Inc.

Journal ArticleDOI
TL;DR: In this article, the kinetics of batch melt transesterification of diphenyl carbonate with 2,2-bis(4-hydroxyphenyl)propane to polycarbonate have been studied in the presence and absence of LiOH.
Abstract: The kinetics of batch melt transesterification of diphenyl carbonate with 2,2-bis(4-hydroxyphenyl)propane to polycarbonate have been studied in the presence and absence of LiOH.H 2 O catalyst in the temperature range of 180-250 o C. The effects of reaction temperature and catalyst concentration on conversion and oligomer formation are analyzed. For quantification of the reaction kinetics, a detailed molecular species model has been developed and solved. Quite satisfactory agreement between the model predictions and experimental data has been obtained

Journal ArticleDOI
TL;DR: In this article, the authors showed that under low power (60 W) microwave irradiation, transesterification of phospholipids and triglycerides can be achieved in 50 s and 60 s, respectively.

Journal ArticleDOI
TL;DR: The irreversible transesterification of racemic 2-methyl-1,3-propanediol derivatives, the monoethers, 3a, 3b, 5a, and the monobenzoate 5b, with vinyl acetate catalyzed by Pseudomonas fluorescens lipase in chloroform affords enantiomerically pure chiral synthons as discussed by the authors.

Patent
13 Apr 1992
TL;DR: In this article, a diaryl carbonate is produced by transesterification of a dialkyl carbonates with an aromatic hydroxy compound, such as phenol, in three successive reaction zones.
Abstract: A diaryl carbonate is produced by transesterification of a dialkyl carbonate, such as dimethyl carbonate, with an aromatic hydroxy compound, such as phenol, in three successive reaction zones. A transesterification catalyst, such as a titanate ester or ester mixture is used in each zone. Conditions are selected to maximise formation of alkyl aryl carbonate in the first and second reaction zones, whilst conversion to diaryl carbonate is favoured in the third reaction zone. The vaporous mixture from the first two reaction zones is a mixture containing alkyl alcohol, dialkyl carbonate, alkyl aryl carbonate and aromatic hydroxy compound. This mixture is separated in an alkyl alcohol recovery zone by distillation in the distillation columns to produce useful recycle streams. The second of these distillation columns can be operated at a lower pressure than the first, thus enabling the heat of vaporisation of this mixture to be used as the source of heat for the reboiler of the second distillation column of the alkyl alcohol recovery zone.

Patent
16 Sep 1992
TL;DR: In this paper, a process for the preparation of esters of acrylic or methacrylic acid with alcohols is described, where the preformed ester of a C 1 -C 4 monohydric alcohol having only one oxygen function under transesterification conditions with a second alcohol having at least two carbon atoms and at least 2 oxygen functions in the presence of a catalyst comprising (a) an oxide, hydroxide or nitrate of calcium or barium and (b) a lithium compound LiX wherein X is nitrate, sulphite or carboxylate having
Abstract: This invention relates to a process for the preparation of esters of acrylic or methacrylic acid with alcohols. The process comprises reacting the preformed ester of a C 1 -C 4 monohydric alcohol having only one oxygen function under transesterification conditions with a second alcohol having at least two carbon atoms and at least two oxygen functions in the presence of a catalyst comprising (a) an oxide, hydroxide or nitrate of calcium or barium and (b) a lithium compound LiX wherein X is nitrate, sulphite or carboxylate having more than six carbon atoms such that both (a) and (b) are not nitrate in the same catalyst.

Journal ArticleDOI
TL;DR: The transesterification rate in near-critical carbon dioxide proved to be much lower than in hexane at comparable conditions of temperature, water content, and substrate and enzyme concentration.

Journal ArticleDOI
01 Jan 1992-Polymer
TL;DR: In this article, the degree of randomness and average sequence length of poly(butylene terephthalate) (PBT) units for a number of melt processed PBT/polyarylate blends were determined.

Journal ArticleDOI
TL;DR: A simple method to overcome low equilibrium conversion in lipase catalysed resolution of alcohols by transesterification was developed by applying reduced pressure, forcing the co-product ethanol to evaporate during the reaction.
Abstract: A simple method to overcome low equilibrium conversion in lipase catalysed resolution of alcohols by transesterification was developed. Ethyl octanoate was used as acyl donor as well as solvent and ...

Journal ArticleDOI
TL;DR: In this paper, a series of monoorganotin(IV) compounds were investigated as transesterification catalysts for the reaction of butyl propionate with methanol.
Abstract: A series of monoorganotin(IV) compounds has been investigated as transesterification catalysts for the reaction of butyl propionate with methanol. The most active catalysts were found to be those which contain tin-halogen bonds, e.g. monobutyltin trichloride (BuSnCl3), and the least effective were the coordinatively saturated monoorganotin derivatives. Certain of the mono(2-carboalkoxyethyl)tin compounds were found to undergo a facile autocatalysed transesterification reaction with alcohols. Coordination of the carbonyl group in the ester to the tin catalyst is an important factor influencing its activity. A study of the catalysis of the esterification of propionic acid by BuSnCl3 is reported.

Journal ArticleDOI
TL;DR: A new practical procedure for the enzymatic resolution of 1,2-diols 1a–e has been developed by lipase-catalysed regio- and enantio-selective esterification using anhydrides as acylating agents in organic solvents.
Abstract: A new practical procedure for the enzymatic resolution of 1,2-diols 1a–e has been developed by lipase-catalysed regio- and enantio-selective esterification using anhydrides as acylating agents in organic solvents.

Patent
19 Jun 1992
TL;DR: In this paper, a mixture of methanol or ethanol and an alkaline catalyst is used for the separation of a light, ester-rich phase and a heavy, glycerine-rich one.
Abstract: Oils or fats, in particular of vegetable, but also of animal origin, are reacted with methanol or ethanol and an alkaline catalyst in the liquid phase. Glycerine and methyl esters of fatty acids or ethyl esters of fatty acids are formed. The reaction is carried out using at least two reaction steps, each reaction step having a mixing reactor and a separator for the separation of a light, ester-rich phase and a heavy, glycerine-rich phase. The oil or the fat, the alcohol and the catalyst are added to the mixing reactor in the first reaction step and these substances are intensively mixed. The alcohol and the catalyst as well as the light, ester-rich phase obtained in the preceding reaction step are added for intensive mixing to the mixing reactor in the second and each further reaction step. A heavy phase is separated in the separator in the second to last reaction step and at least partly fed back to the mixing reactor in the first reaction step. Methyl esters of fatty acids or ethyl esters of fatty acids are obtained from the light, ester-rich phase separated in the last reaction step by at least one further separation treatment. The process is preferably carried out using two reaction steps.