A quantum chemical approach to the water assisted neutral hydrolysis of ethyl acetate and its derivatives

A quantum chemical approach to the neutral water assisted hydrolysis of ethyl acetate and its halogenated derivatives in the gas phase is presented. Calculations of a cluster containing one ester and two water molecules were accomplished with the progam Gaussian 94 at the semi-empirical AM1 and the abinitio RHF/3-21G and RHF/6-31+G(d) computational levels. For each method the Gibbs energies of several key structures along the reaction path were calculated after full geometry optimization. For the proposed first reaction step a transition state with tetrahedral structure at the carbonyl carbon of the ester was found, thus corroborating experimental studies. The computed Gibbs energy of activation of the first reaction reveals a similar influence of polar substituents on this reaction as found by experiments in the liquid phase.