氯化物与苯磺酸甲酯在不同溶剂中亲核取代反应的动力学研究

Kinetic study on nucleophilic substitution reactions of chloride with methyl benzenesulfonate as substrate in different solvents.

用动力学方法研究了不同温度下氯化物与苯磺酸甲酯在丙酮、2-丁酮、环己酮、乙腈、DMF和甲醇中的亲核取代反应.反应的动力学行为可用SN2机理来解释.在一定溶剂中不同温度(5～45℃)的反应速率常数可用Arrhenius方程很好地关联.根据Arrhenius方程和过渡态理论分别求得了活化能、指前因子、活化焓和活化熵.对溶剂效应和焓-熵补偿作用进行了讨论.在不同溶剂中以活化能作为标度的Cl-的亲核反应性顺序为:环己酮＞丙酮＞2-丁酮＞DMF＞乙腈＞甲醇.

The nucleophilic substitution reactions of chloride with methyl benzenesulfonate as substrate were investigated kinetically at different temperatures in acetone,2-butanone, acetonitrile, cyclohexanone, DMF and methanol. The reaction behavior can be explained by Sx 2 mechanism. In a given solvent the rates can be perfectly related with Arrhenius＇s equation within the experimental temperature range of 5℃ to 45℃. The activation energy and the preexponential factor according to arrhenius＇s equation, the activation enthalpy, and the activation entropy according to the transition state theory were gained. The solvent effects, the compensation of the activationenthalpy ,and the activation entropy were discussed. Taken the activation energy as the scale for nucleophilicity ,the order of the nucleophilicity of chloride in different solvents was as follows： cyclohexanone〉acetone〉2-butanone〉DMF〉 acetonitrile〉 methanol.