ACID HYDROLYZES OF HYDROPHOBIC DIOXOLANES IN CATIONIC MICELLES - A QUANTITATIVE TREATMENT BASED ON THE POISSON-BOLTZMANN EQUATION

Acid hydrolyses of hydrophobic dioxolanes, 1a and 1b, are inhibited by cationic micelles of myristyl- and cetyltrimethylammonium halides, MTAX and CTAX, respectively (X = Cl, Br), but at surfactant concentrations sufficient to bind all the substrate, first-order rate constants, k-psi, at constant [HX], increase with increasing [surfactant] and on addition of NaX. In the absence of added NaX k-psi increases linearly with [MTAX] and [CTACl], but at constant [surfactant] there are breaks in plots of k-psi against [NaX]. These results can be explained quantitatively in terms of a pseudophase model in which hydrogen ion concentrations at micellar surfaces are calculated by solution of the Poisson-Boltzmann equation.