Quantum theory of concerted proton transfer reactions in polar media. Linear electronic terms

Abstract

A quantum mechanical theory has been developed for concerted two-proton transfer reactions in polar media. The formulation is based on second order quantum mechanical perturbation theory; this assumes that the intermediate state, i.e., the state prevailing after the transfer of the first proton, is short-lived compared with the uncertainty time of the system. The energy of activation E_a of the overall process is determined by the value of E_a for either the first or the second proton transfer, and it is shown how, at least in principle, a distinction from a one-proton and a consecutive two-proton transfer reaction can be made. Important qualitative and semiquantitative correlations between energy of activation and overall energy of reaction are predicted, and the Brønsted coefficient and pre-exponential Arrhenius factor are discussed.