Rates of Hydrolysis of Carbamate and Carbonate Esters in Alkaline Solution

Abstract

The rate of the alkaline hydrolysis of several aliphatic and aromatic carbamate and and carbonate esters was studied at various temperatures. The reactions were found to be first order with respect to both hydroxyl ion and the ester. The data seemed to indicate two mechanisms for the hydrolysis of the carbamates: that initiated by an hydroxyl ion attachment on the central carbon atom followed by a carbamate ion intermediate, and that involving direct ionization of an amide hydrogen followed by formation of an isocyanate intermediate. Since the latter mechanism appears to proceed with much greater ease for carbamates of strongly electro-philic alcohols, the N-unsubstituted and N-monosubstituted carbamates of these compounds undergo cleavage at rates several orders of magnitude greater than those of the corresponding disubstituted carbamates. The rate of the alkaline hydrolysis of several aliphatic and aromatic carbamate and and carbonate esters was studied at various temperatures. The reactions were found to be first order with respect to both hydroxyl ion and the ester. The data seemed to indicate two mechanisms for the hydrolysis of the carbamates: that initiated by an hydroxyl ion attachment on the central carbon atom followed by a carbamate ion intermediate, and that involving direct ionization of an amide hydrogen followed by formation of an isocyanate intermediate. Since the latter mechanism appears to proceed with much greater ease for carbamates of strongly electro-philic alcohols, the N-unsubstituted and N-monosubstituted carbamates of these compounds undergo cleavage at rates several orders of magnitude greater than those of the corresponding disubstituted carbamates.