Effects of Medium on Nucleophilic Substitution Reactions (). Methanolysis of t-Butylbromide and Benzoylchloride in Methanol-Acetonitrile Mixtures

[摘要] A kinetic study of the methanolysis of t-butylbromide and benzoylchloride in methanol-acetonitrile mixtures is reported. First order rate constants for the methanolysis of t-butyl bromide show maximum at XMeOH = 0.75¡­0.9 and 25¡­50¡É. Apparent second order rate constants for the methanolysis of benzoylchloride also show maximum at XMeOH = 0.6¡­0.95 and 12¡­26¡É. The maximum rate is ascribed to the solvent structure change; the addition of acetonitrile to methanol perturbs the methanol structure increasing the free methanol molecules available to stabilize the transition state for the methanolysis of t-butylbromide and benzoylchloride. It has been shown that methanol acts as nucleophilic and electrophilic catalyst upon methanolysis of t-butylbromide and as electrophilic catalyst upon methanolysis of benzoylchloride.

[学科分类] 化学（综合）