Kinetics of the reactions of phenacyl bromide and of pare-substituted phenacyl bromides with benzoate and substituted trans-cinnamate ions

Abstract

The second-order rate constants for the reactions of various para-substituted phenacyl bromides with benzoate ion and with several substituted trans-cinnamate ions have been measured in 90% acetone–10% water (v/v) mixture. Electron-releasing substituents in cinnamate ion and electron-withdrawing substituents in phenacyl bromide increase the rate of substitution reaction. Results of correlation analysis show constant selectivity in the reactions of various phenacyl bromides with a given cinnamate ion (ρca. 1.05) and also in various cinnametes with a given phenacyl bromide (ρca.–0.2). In these simple S_N2 reactions, the reactivity–selectivity effects are absent.