Nonadiabatic solvation model for S N 2 reactions in polar solvents

Abstract

An analytic theory for SN2 reactions in polar solvents in the nonadiabatic solvation limit is presented and used to interpret the computer simulation results of the preceding paper by Bergsma et al. The theory is based on the nonadiabatic solvation limit of previous studies by van der Zwan and Hynes and incorporates the solvent approximately but explicitly via a coordinate additional to the intrinsic reaction coordinate. Central results include: an explicit expression for the reaction transmission coefficient κ, the dependence of reaction probability on kinetic energy, the interpretation of κ in terms of nonequilibrium solvation entropy effects, and the deviation of the reaction coordinate from that assumed in the standard equilibrium solvation transition state theory view of the reaction.