Isotope effects in proton transfer reactions

Abstract

The reason why the more symmetrical a transition state is, the larger is the isotope effect for a proton transfer reaction, is a matter of controversy. The simplest explanation involving the stretching frequencies of a 3-centre model has been held to be inadequate. In this paper the isotope effect for the simple 3-centre model is calculated for all possible values of the force constants between the 3 centres. The calculated isotope effect is displayed on a simple diagram which shows its variation with transition state structure.