Solvolysis of substituted benzoyl chlorides in nonionic and mixed micellar solutions.

The solvolysis of substituted benzoyl chlorides is sensitive both to substituent electronic effects and to medium effects. The solvolysis reactions of substituted benzoyl chlorides have been analyzed in the presence of nonionic micelles. The reaction is inhibited or catalyzed depending on the reaction mechanism, dissociative or associative, respectively. The micellar effects observed can be related to the low water content and low polarity of the interface as well as an increase of the nucleophilic character of the interfacial water. Moreover, the effect of the micellar surface charge on the solvolysis mechanism with high associative character was systematically studied. Mixed micelles of nonionic-ionic surfactants with a variable ionic content were prepared and characterized regarding charge and polarity. A correlation between the net charge of the micelles and the rate constants at the micellar interface was observed. The results suggest that the transient state for this mechanism is highly stabilized in a positively charged environment while the negative surface given by anionic micelles strongly inhibit the solvolysis reaction.