Theoretical Study on the Gas‐Phase SN2 Reaction of Microhydrated Fluoride with Methyl Fluoride

Abstract

AbstractThe rate constants for the gas‐phase SN2 reaction of F−(H2O) with CH3F have been calculated using the dual‐level variational transition state theory including multidimensional tunneling from 50 to 500 K. Tunneling was found to dominate the reaction below 200 K. The deuterium, 13C, and 14C kinetic isotope effects (KIEs) and solvent (D2O) isotope effects (SKIEs) were also calculated in the same temperature range. The results indicated that the deuterium and heavy water substitutions resulted in inverse KIEs (0.6∼0.8 ) while the 13C and 14C substitutions resulted in normal KIEs (1.0∼1.2) at room temperature. The calculated carbon KIEs increased significantly below 80 K due to the differences in the magnitude of the tunneling effects for different isotopic substitutions.