Steric influence of the alkyl component in the alkaline hydrolysis of acetates and propionates

Abstract

Velocities and Arrhenius activation energies have been determined for the alkaline hydrolysis of methyl, ethyl, n-propyl, n-butyl, isopropyl, s-butyl, t-butyl, isobutyl, and cyclohexyl acetates, and methyl, ethyl, n-butyl, and isopropyl propionates in 70% aqueous acetone. The parallelism between acyl and alkyl polar substituent constants noted by Taft has been used as a basis for assessing the steric influence of alkyl components during alkaline hydrolysis. The results compare with those of other published data on the hydrolysis of other series of esters involving a variation in the alkyl component. The effects noted suggest that steric influences of substituents in the alkyl component are different from those exerted by the same species in the acyl component of esters. Finally, it appears from the results that the magnitude of steric influences of substituents is more susceptible to environment than is the case for polar influences.