- Saturation vapor pressures and vaporization enthalpies of esters of ethylene glycol and lower carboxylic acids
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Saturation vapor pressures and vaporization enthalpies of ethylene glycol and C1-C5 carboxylic acid disubstituted esters of normal and branched structures are determined by the transfer method in the tem-perature range of 295 to 327 K. Dependences of vaporization enthalpies versus the number of carbon atoms in a molecule and the retention indices are determined. An analysis of existing calculation schemes is given to help predict the vaporization enthalpy of the compounds under study.
- Maslakova,Krasnykh,Levanova
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- Kinetics and quantitative structure-activity relationships for pseudomonas sp. Lipase-catalyzed hydrolysis of both monoesters and diesters of ethylene glycol
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The goal of this work is to study kinetics and quantitative structure-activity relationships for steady states of Pseudomonas sp. lipase-catalyzed hydrolysis of both diesters and monoesters of ethylene glycol. Based on the steady-state kinetics of the enzyme-catalyzed hydrolysis of the diesters of ethylene glycol, the diesters and the monoesters react simultaneously as soon as monoester has started to build up in the reaction medium. In other words, the apparent Km values of the diesters are the Km values of the diesters (KmA) plus the Km values of the monoesters (KmB), and all Vmax values are about the same. Moreover, the pH-stat titration curve of the enzyme-catalyzed hydrolysis of the diesters of ethylene glycol is initially hyperbolic, then there is a sharp falloff in the hydrolysis rate. The abrupt stoppage of the reaction (relaxation stage) may be due to the existence of two phases in the reaction medium, that is, the product (ethylene glycol) and the substrates (the diesters of ethylene glycol) are not miscible. Furthermore, quantitative structure-activity relationships for varied acyl groups of mono- and diesters of ethylene glycol are studied. The fact that both pKmA and pK mB values are linearly correlated with the hydrophobicity constant (π) but not with the electronic substituent constants (σ*) indicates that the affinity of these substrates for the enzyme depends only on the hydrophobicitv of substrates. Copyright
- Chiou, Shyh-Ying,Cheng, Yu-Ru,Lu, Chun-Ping,Lin, Yan-Fu,Lin, Long-Yau,Lin, Gialih
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- Rational engineering of Candida antarctica lipase B for selective monoacylation of diols
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The enzyme Candida antarctica lipase B was subjected to site directed mutagenesis suggested by molecular modelling. The selectivity for the enzyme increased towards a range of diols over their corresponding monoesters as an effect of the mutations. This journal is The Royal Society of Chemistry 2012.
- Hamberg, Anders,Maurer, Steffen,Hult, Karl
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supporting information
p. 10013 - 10015
(2012/10/30)
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- Ceric ammonium nitrate (CAN) - A useful catalyst for the rapid and high-yield esterification of carboxylic acids and alcohols with special reference to steroid and other multi-functional natural products
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Ceric ammonium nitrate (CAN) acts as a versatile catalyst for the esterification of carboxylic acids and alcohols, including steroids and other multi-functional natural products, in excellent yields under mild and convenient reaction conditions.
- Goswami,Chowdhury
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p. 955 - 957
(2007/10/03)
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- Unique Template Effects of Distannoxane Catalysts in Transesterification of Diol esters
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1,n-Diol diacetates (n = 2,3,4) are selectively converted into the corresponding monoacetates by distannoxane-catalyzed transesterification.Such unique selectivity is not encountered with 1,n-diol diacetates where n>/=5.A great difference in reactivity is also seen in the transesterification between methyl butyrate and 1,n-diol monoacetates: the ethylene glycol derivative sluggishly undergoes transesterification whereas higher homologs react smoothly.The unique template effects of the catalysts are discussed in terms of cooperation of two different tin atoms which are located in the proximity.
- Otera, Junzo,Dan-oh, Nobuhisa,Nozaki, Hitosi
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p. 3065 - 3074
(2007/10/02)
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- Preparation of Carboxylate Esters of Polyhydric Alcohols by Using a Sulfonated Charcoal Catalyst
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Ethane-1,2-diol, propane-1,2-diol, butane-1,4-diol and propane-1,2,3-triol are readily esterified by carboxylic acids in near quantitative yields in the presence of a sulfonated charcoal catalyst.
- Prager, Rolf H.,Yurui, Zhang
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p. 1003 - 1005
(2007/10/02)
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