Isotope effects on the reaction of proton transfer to benzene anions in ethanol

A theoretical study on the reaction of proton transfer from ethanol to benzene anions was performed at the ab initio level. It was found that in the gas phase the reaction proceeds without potential energy barrier with respect to reactants held at infinite distance, even though a potential energy barrier exists when measured from the prebarrier complex formed by the reactant molecules. When restrictions on orientation of the reactant molecules in the solid phase are taken into account, the potential energy barrier found exceeds 40 kcal/mol. A theoretical estimate of the kinetic isotope effect due to the tunneling effect, κH/κD, of 9.0 × 103 is found, in good agreement with available experimental data.