Nucleophilic substitution reaction of carboxylate and phosphate esters with hydroxamate ions in microemulsions

A kinetic study of the nucleophilic substitution reaction of hydroxamate ions with p-nitrophenyl acetate (carboxylate ester) and p-nitrophenyl diphenyl phosphate (phosphate ester) has been performed in cationic microemulsion prepared from combinations of weight percentage of cationic surfactants (CTAB, CTACl and CPC), co-surfactant n-butanol, n-hexane (oil) and water. The pseudo-first-order rate constants increases with increasing water content. Significant ‘microemulsion catalysis’ have been observed for the reaction of PNPDPP with the hydroxamate ions over the reactions in aqueous solution. Kinetic model for nucleophilic substitution reactions, have been discussed.