Ab initio MD simulations of a prototype of methyl chloride hydrolysis withexplicit consideration of three water molecules: a comparison of MD trajectories with the IRC path

Ab initio molecular dynamics simulations at the Hartree-Fock/6-31G level of theory are performed on methyl chloride hydrolysis with explicit considera tion of one solute and two solvent water molecules at a temperature of 298 K. The reaction involves the formation of a reactant complex and the energy surface to the transition state is found to be simple. Two types of trajec tories toward the product are observed. In the first type, the system reach es an intermediate complex (complex-P1) region after two nearly concerted p roton transfers involving the attacking water molecule and the solvent wate r molecules. These trajectories resemble the intrinsic reaction coordinate trajectory. The thermal motion of the atoms leads the system to another int ermediate complex (complex-P2) region. A second type of trajectory is found in which the system reaches the complex-P2 region directly after the proto n transfers, In both of these forward trajectories, back proton transfers l ead the system to a final complex-F region which resembles protonated metha nol.