Effect of Surfactant Micelles on the Stereochemistry and Rate of “Amsylate” Solvolytic Displacement Reactions in Water

A study of the effect of micelles on the aqueous solvolysis of alkyl p-trimethylammonium benzenesulfonates (“amsylates”) has revealed that anionic micelles strongly inhibit the rate, and in some cases modify the stereochemistry, of the reaction. The mechanism of these solvolyses has been examined in detail. The results suggest that the rate inhibition is due to the squeezing out of water from the Stern layer of the mixed cationic-anionic micelles involved and the stereochemical changes are due to direct attack of the surfactant head group upon the reactive amsylate carbon atom, leading to a short-lived covalent dialkyl sulfate intermediate.