Unusual Rate Enhancement in the Hydroxide-Ion-Catalyzed Cleavage of Acetyl Salicylate Ion (Aspirin Anion) in the Presence of Anionic Micelles

Abstract

The reaction rate studies on the hydrolytic cleavage of acetyl salicylate ion (AS-) within the [-OH] range 0.010-0.025 M reveal AS- and -OH as the reactants. The effects of micelles of sodium dodecyl sulfate (SDS) on observed pseudo-first-order rate constants (kobs) for the hydrolytic cleavage of AS- have been studied at different [OH-]. At a constant [OH-], the rate constants (kobs) follow an empirical relationship: kobs = C + F [SDS]T where [SDS]T represents total SDS concentration. The magnitudes of C and F increase with an increase in [OH-]. These data are explained in terms of the pseudophase model of the micelle.