Molecular Dynamics of a Model SN2 Reaction in Water.
CALIFORNIA UNIV SAN DIEGO LA JOLLA DEPT OF CHEMISTRY
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Molecular dynamics are computed for a model S sub N2 reaction C1- CH3C1 yield C1CH3 C1- in water and are found to be strongly dependent on the instantaneous local configuration of the solvent at the transition state barrier. There are significant deviations from the simple picture of passage over a free energy barrier in the reaction coordinate, and thus, a marked departure from Transition State Theory occurs in the form of barrier recrossings. Factors controlling the dynamics are discussed, and, in particular, the rate of change of atomic charge distribution along the reaction coordinate is found to have a major effect on the dynamics. A simple frozen solvent theory involving nonadiabatic solvation is presented which can predict the outcome of a particular reaction trajectory by considering only the interaction with the solvent of the reaction system at the gas-phase transition barrier. The frozen solvent theory predicts the adjustment the transmission coefficient k needed to make the transition state theory rate agree with the outcome of the molecular dynamics trajectories. Keywords Bimolecular reactions Nucleophilic reactions Substitution reactions Solvents Mathematical models.
- *REACTION KINETICS
- *MOLECULE MOLECULE INTERACTIONS
- *NUCLEOPHILIC REACTIONS
- MATHEMATICAL MODELS
- MOLECULAR PROPERTIES
- FREE ENERGY
- ATOMIC CHARGE
- SUBSTITUTION REACTIONS
- Organic Chemistry
- Atomic and Molecular Physics and Spectroscopy