临界溶剂化作用对水解反应动力学的影响

用过渡态及Kirkwood介电模型考察近临界水中醋酸甲酯(MeAc)水解动力学.实验结果表明,临界溶剂化作用使本体系在623K附近出现反应活化体积(ΔV^≠)极负值现象,同时反应表观活化能降低至(23.5±8.29)kJ/mol.利用lnkc与反应场的线性关系可修正压力因素对水解动力学的影响,并证实了近临界水介质中MeAc水解S_N2反应机理的可靠性.

Effects of Critical Solvation on Hydrolysis Kinetics

The work presented in this paper focuses on employing Transition State Theory and Kirkwood dielectric model to interpret the solvation effects on hydrolysis of methyl acetate under near or supercritical conditions. The experimental data show that the apparent activation energy of hydrolysis is (23.5±8.29) kJ/mol, which is much lower than that obtained by using the conventional technique, the intricate solvation effects observed in the experiment may cause a minimum activation volume at the temperature near to the critical temperature, and the reaction field shows a good linear relationship with ln kc, which can be utilized to correct the effect of pressure on reaction kinetics, also SN2 reaction mechanism can be validated from several aspects.