Steric substituent effect on the resin catalyzed hydrolysis of alkyl acetate esters

Abstract

The rates of hydrolysis of seven acetate esters substituted in the alkyl group have been studied in the presence of a sulfonated cation exchange resin in 70% aqueous acetone solution. the slower hydrolysis rates with increasing size of substituent are related to increasing steric influence, as determined by decreasing values of the steric substituent parameter, Es. The efficiency of the resin catalyst is related to the entropy of substituents. Influence caused by steric hindrance on reaction rates accounts satisfactorily for observed variations of the enthalpies and entropies of activation with alkyl group substituents. The entropy, ΔSx, values increase in the order: n-octyl-<ethyl-<methyl acetate, which represents the sequence of probability for the formation of the activated complex on the exchange resin.