An ab initio MO study on the hydrolysis of methyl chloride with explicit consideration of 13 water molecules

Ab initio MO calculations (HF/3-21G, HF/6-31G, HF/6-31+G* and MP2/6-31+G*) were carried out on the hydrolysis of CH3Cl in which up to 13 water solvent molecules were explicitly considered. For n⩾3, three important stationary points (cmp1, TS, and cmp2) were detected in the course of the reaction. The calculations for the n=13 system at the HF/6-31+G* level reproduced the experimental activation enthalpy and the secondary deuterium kinetic isotope effect. The two reacting bond lengths in the transition state are 1.975 Å (O–C) and 2.500 Å (C–Cl), and CH3Cl is surrounded by 13 water molecules without any apparent vacant space. The proton transfer from the attacking water to the water cluster occurs after TS is reached.