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Dynamics and Kinetics of Gas-Phase SN2 Nucleophilic Substitution Reactions

Trajectory simulations have shown that SN2 reactions of the type X - + CH3Y -> XCH3 + Y - have nonstatistical dynamics. RRKM theory is an inaccurate model for the X ----CH3Y and XCH3---Y - ion-dipole complexes, since they have slow intramolecular vibrational energy redistribution (IVR). Recrossing of the central barrier may be important and as a result transition state theory does not give an accurate rate constant for a reaction with a central barrier, such as Cl - + CH3Cl. Important questions remain concerning the origin of the nonstatistical dynamics for these reactions and quantitative comparisons of dynamical simulations with experiment are important.

Reaction path potentials for Cl- + CH3Cl -> ClCH3 + Cl- and Cl- + CH3Br -> ClCH3 + Br- SN2 nucleophilic substitution