Transmission of substituent effects in polar reactions. Part 2.—Relative rates of halide displacement and ester saponification in the alkaline hydrolysis of α-haloacetate esters

Abstract

Rate coefficients and activation energies for ester saponification in the alkaline hydrolysis of the ethyl esters of the α-haloacetic acids in aqueous solution have been determined by a pH-stat method with correction for the significant competition by displacement of halide ion for the bromo- and iodo-esters. While the gross effects of the halogens relative to hydrogen may be understood by reference to the influence of direct electrostatic fields, there is evidence that the rates of ester saponification may also be enhanced by partial displacement of the halide ion in the transition state. The dissociation of methane sulphonyloxyacetic acid and the kinetic of alkaline hydrolysis of its ethyl ester have been studied in the light of this hypothesis.