Analysis of the reaction force for a gas phase SN2 process:: CH3Cl+H2O→CH3OH+HCl

The reaction force F(R-c) is the negative derivative of a system's potential energy V(R,) along the intrinsic reaction coordinate of a process. If V(R,) goes through a maximum, as is commonly the case, then F(R-c) has a characteristic profile: a negative minimum followed by zero at the transition state and then a positive maximum. These features reflect four phases of the reaction: an initial one of reactant preparation, followed by two of transition to products, and then relaxation of the latter. In this study, we have analyzed, in these terms, a gas-phase S(N)2 substitution, selected to be CH3Cl + H2O -> CH3OH + HCl. We examine, at the B3LYP/6-31G* level, the geometries, energetics, and molecular surface electrostatic potentials, local ionization energies, and internal charge separation.