Direct ab Initio Dynamics Study of the OH + HOCO Reaction

Abstract

The reaction between OH and HOCO has been examined using the coupled-cluster method to locate and optimize the critical points on the ground-state potential energy surface. The energetics are refined using the coupled-cluster method with basis set extrapolation to the complete basis set (CBS) limit. Results show that the OH + HOCO reaction produces H2O + CO2 as final products and the reaction passes through an HOC(O)OH intermediate. In addition, the OH + HOCO reaction has been studied using a direct dynamics method with a dual-level ab initio theory. Dynamics calculations show that hydrogen bonding plays an important role during the initial stages of the reaction. The thermal rate constant is estimated over the temperature range 250-800 K. The OH + HOCO reaction is found to be nearly temperature-independent at lower temperatures, and at 300 K, the thermal rate constant is predicted to be 1.03 x 10(-11) cm3 molecule(-1) s(-1). In addition, there may be an indication of a small peak in the rate constant at a temperature between 300 and 400 K.