Ab Initio Study of the SN2 Reaction CH3Cl + Cl- → Cl- + CH3Cl in Supercritical Water with the Polarizable Continuum Model

We present some calculations for an SN2 reaction in ambient and supercritical water performed with a continuum method for solvation, the polarizable continuum model (PCM). PCM allows us to perform quantum mechanical (QM) ab initio calculations at almost all the levels of the QM theory and allows us to treat solvent-separated solutes on the same footing as a tight reacting system. Both features are here exploited. The results indicate that the standard PCM version is able to reproduce computer simulation results at a good level of accuracy, with the exception of a specific range of P−T values of supercritical water characterized by a large isothermal compressibility. For calculations in this P−T range we present a PCM formulation giving results in good agreement with results from simulations.