Kinetics •of acid catalysed hydrolysis of methyl, ethyl and butyl acetates in amide, salt and surfactant environments

Abstract

The rate of the acid catalysed hydrolysis of ethyl acetate decreases in the presence of urea, substituted ureas, thiourea, acetamide and sodium chloride. The amides affect the rate through significant deactivation of the catalyst, H⁺ ion; sodium chloride does this by decreasing the activities of both H⁺ ion and water as well as by lowering the polarity of the medium. Micellar solutions of sodium dodecyl sulphate (SDS) and cetyltrimethylammonium bromide (CTAB) increase the rates of hydrolysis of methyl, ethyl and butyl acetates, the effect of the former being greater than that of the latter. At 10 times cmc of SDS, the rate enhancement for methyl and ethyl acetates at 310K are 1.07 and 2.12 folds respectively, and 5.05 folds for butyl acetate at 304K; butyl acetate is the most affected ester. The micelles lower the activation energy and act as catalyst in the hydrolytic cleavage of the esters. The rate constants and the activation parameters of butyl acetate hydrolysis in SDS medium undergo sharp changes at [SDS] equal to its cmc.