Modelling of micellar effects upon substitution reactions with moderately concentrated hydroxide ion

Abstract

Cationic micelles of cetyltrimethylammonium chloride and bromide (CTACl and CTABr) speed reactions of 2,4-dinitro-1-naphthyl chloride (DNNC) and p-nitrophenyl diphenyl phosphate (pNPDPP) with OH^–. The pseudophase ion-exchange model fits the data for reaction with [OH^–] < 0.05 mol dm^–3, but the reaction is faster than predicted at higher ratios of [OH^–]. The deviations from theory are largest with high ratios of [OH^–] to [Cl^–] or [Br^–] and are larger in CTABr than in CTACl. A mass-action-like model with each anion binding independently to the micelle fits the data for 10^–3–0.5 mol dm^–3 OH^–.