Ab initio and CVTST investigation of the gas phase nucleophilic substitution CH3Cl + OH- → CH3OH + Cl-

摘要

In this work the theoretical study of the gas-phase bimolecular nucleophilic substitution reaction, CH3Cl + OH-→ CH3OH + Cl-, is introduced aiming the description of the reaction path and the calculation of rate coefficients with the canonical variational transition state (CVTST) method. The calculations were performed at the MP2/6-31+G(d) level. The calculated enthalpy difference for the reaction at 298.15 K (-49.93 kcal mol-1) is in good agreement with the literature value: -50.4 kcal mol-1. The calculated rate coefficient, 1.94 × 10-9 cm3 molecule-1 s-1 at 298.15 K, also shows good agreement with the experimental data: 1.3-1.6 × 10-9 cm3 molecule-1 s-1. Moreover, the rate coefficients show non-Arrhenius behavior, decreasing as the temperature increases, which is consistent with the experimental expectation. In this way, the performance of the variational transition state theory for this reaction can be considered satisfactory.