Nonequilibrium solvation effects on reaction rates for model SN2 reactions in water

• DOI: 10.1063/1.455864
• Publication Date: 2002-07-26T13:10:26Z
• Authors: Bradley J. Gertner; Kent R. Wilson; James T. Hynes
• Keywords: Transition state theory; SN2 reaction

Molecular dynamics (MD) simulations of the model SN2 reaction Cl−+CH3Cl→ClCH3+Cl− in water, and variants thereof, are presented. The resulting transmission coefficients κ, that measure deviations rates from transition state theory (TST) rate predictions due to solvent-induced recrossings, used assess validity generalized Langevin equation (GLE)-based Grote–Hynes (GH) theory. GH found agree with MD results within error bars calculations for each 12 cases examined. This agreement extends nonadiabatic regime, where solvent molecule motions unimportant κ is determined by static configurations at state, into polarization caging motion critical determining κ. In contrast, Kramers fall well below simulation results. friction kernel GLE evaluate values determined, simulation, a fixed-particle time correlation function force state. When this expressed as (Fourier) spectrum frequency, marked similarities pure observed, identify water determine coefficient unity, TST value, dominated (translational reorientational) which on scale recrossings essentially configurations. frozen solvent, limit κNA hinderd rotations (librations). Finally, underlying assumptions discussed context