Micellar catalysis of organic reactions. X. Further evidence for the partial failure of the pseudophase kinetic model of micellar catalysis for reactions of hydroxide ions

Abstract

Rates of hydrolysis for a number of amides and hydroxydehalogenation of some activated aryl halides have been determined in the presence of micelles of cetyltrimethylammonium bromide (ctab) and cetyltrimethylammonium fluoride (ctaf). The rates of reaction in micelles of ctaf are greater than in micelles of ctab in each case but the ctaflctab rate ratios are smaller than predicted by the pseudophase model of micellar catalysis. The results are discussed in terms of reactions in ctaf occurring within the micelle but reactions in ctab occurring both within the micelle and across the micellar interface. The extent of reaction across the micellar interface is shown to be dependent on the structure of the substrate. Substrates chosen were those bearing hydrophobic or hydrophilic substituents, designed to orient the substrate molecules in predictable ways within the micelles.