EFFECT OF SUBSTRATE HYDROPHOBICITY AND ELECTROLYTES UPON THE MICELLARHYDROLYSIS OF P-NITROPHENYL ESTERS

Basic hydrolysis of p-nitrophenyl acetate, propionate and butyrate was studied in the presence of micellar hexadecyltrimethylammonium bromid e. The influence of potassium bromide upon the reaction was also consi dered. The kinetics show that the overall reaction rate increases in t he micellar systems. To explain the effect of micelles upon the reacti ons, the pseudo-phase ion-exchange model was used. From the fitting of data, the solubilization and the ion-exchange constants were obtained . The micellar second-order rate constants were not greater than those in aqueous systems. Hence, the micelles affect the rate by bringing t he reactants together into a small volume, and not by providing a more favorable microenvironment for the reaction.