Computational studies of the aminolysis of oxoesters and thioesters in aqueous solution

(formula presented) X = O, S Transition state structures and energies have been investigated for concerted and stepwise mechanisms for the acyltransfer reactions of ethyl acetate and ethyl thioacetate with ammonia. Specific and general solvent effects have been evaluated. The results predict stepwise mechanisms involving water-catalyzed proton transfer for both reactions and indicate that the thioester is more reactive than the oxoester in both the addition and elimination steps.