Direct ab initio dynamics calculations of the reaction rates for the hydrogen abstraction reaction Cl + HC(O)F → HCl + CFO

Abstract

A direct dynamics method is employed to study the kinetics of the Cl + HC(O)F hydrogen abstraction reaction. The potential energy surface (PES) information is explored from ab initio calculations. Optimized geometries and frequencies of the stationary points as well as the extra points along the minimum energy path (MEP) are calculated at the MP2/6-311+G(d,p) level of theory. In order to improve the energetics along the MEP, single-point calculations are carried out at the QCISD(T)/6-311+G(3df,2p) level of theory. Furthermore, the initial potential information is used to evaluate the rate constants using canonical variational transition-state theory (CVT) with the inclusion of small-curvature tunneling (SCT) corrections over a range of temperatures 220–1500 K. The calculated CVT/SCT rate constants are found to be in good agreement with the available experimental data. Our results show that for the title reaction the variational effect is small at all temperatures, while the tunneling effect plays an important role in the lower temperature range.