DFT study of the rate constants of the reactions CHClmF3−m + Cl = CClmF3−m + HCl (m = 3 − 1)

Abstract

A DFT method was used to study the dynamics of the hydrogen abstraction reactions CHCl_mF_3−m + Cl = CCl_mF_3−m + HCl (m = 3 − 1). The rate constants were evaluated with the improved canonical variational transition state theory incorporating the small-curvature tunneling corrections using the general polyatomic rate constant code Polyrate 8.2. The BHandHLYP/6-311G(d, p) method was performed to determine the structures and generalized frequencies at the stationary points and selected points along the minimum energy paths (MEPs). Energetic information was further refined at the BHandHLYP/6-311++G(3df, 2p) level of theory. The reaction barrier heights were predicted at the BHandHLYP/6-311++G(3df, 2p)//BHandHLYP/6-311G(d, p) level of theory to be 1.95, 3.51 and 6.09 kcal mol⁻¹ for m = 3,2 and 1. The calculated results show that the rate constants at various temperatures are in satisfactory agreement with the experimental values. The variational effect is significant for the calculation of the rate constants for the reaction CHCl₃ + Cl = CCl₃ + HCl.