KINETICS OF ALKALINE HYDROLYSIS OF QUATERNARY PHOSPHONIUM SALTS. THE DEPENDENCE OF MEDIUM EFFECTS ON THE STRUCTURE OF THE SALTS

Abstract

Third order rate constants have been determined for the alkaline hydrolysis of ethyl phenyl- and benzyl alkyl phenyl-phosphonium salts (1) and (2) in aqueous methanol and aqueous tetrahydrofuran. The hydrolyses in the low polarity medium containing tetrahydrofuran are faster than those performed in aqueous methanol of higher polarity. The differences in rate between the two solvent systems are very large when there are no, or few, ethyl groups bound to phosphorus but decreases markedly as ethyl groups replace phenyl groups. This trend is not dependent on the nature of the leaving group. The replacement of a phenyl group by a benzyl group not only increases the rates of hydrolysis in both solvent systems, but it also accentuates the difference in rates between the two media.