化学学报 ›› 1996, Vol. 54 ›› Issue (11): 1060-1064. 上一篇    下一篇

研究论文

苯甲酸乙酯皂化反应的溶剂效应和活化热力学性质研究

胡新根;林瑞森;宗汉兴   

  1. 浙江大学化学系
  • 发布日期:1996-11-15

Study on solvent effect and activation thermodynamics of saponification of ethyl benzoate

HU XINGEN;LIN RUISEN;ZONG HANXING   

  • Published:1996-11-15

用热动力学方法测定了苯甲酸乙酯25℃时在不同组成的乙醇-水混合溶剂中以及当混合溶剂组成分别为50.0%和57.7%时在不同温度下的皂化反应的速率常数。计算了反应的活化能、指前因子和三个活化热力学参数。动力学溶剂效应支持以生成四面体中间体为特征的B~A~C2机理, 活化熵的负值是判断中间体生成的重要依据。用活化熵可以合理解释指前因子。

关键词: 活化, 溶剂效应, 热动力学, 苯甲酸乙酯, 皂化反应, 热力学参数

By the method of thermokinetics, the saponification rate constants of ethyl benzoate have been measured: (1) at 25℃ in ethanol/water mixed solvents of different weight percentage compositions, and (2) at various temperatures when the compositions of the mixtures are 50.0wt% and 57.7wt% respectively. The activation energies, frequency factors, and three activation thermodynamic parameters have also been calculated. Solvent effect supports the suggestion that the reaction observes the mechanism of B~A~C2, with an intermediate. The negative activation entropy is an important evidence for the occurring of intermediate. The frequency factor can be explained from the point of view of activation entropy.

Key words: ACTIVATION, SOLVENT EFFECT, THERMODYNAMICS, ETHYL BENZOATE, SAPONIFICATION, THERMODYNOMICS PARAMETER

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