INTERPOLATED VARIATIONAL TRANSITION-STATE THEORY AND SEMICLASSICAL TUNNELING CALCULATIONS OF THE RATE-CONSTANT OF THE REACTION OH+C2H6 AT 200-3000 K

Ab initio molecular orbital calculations were carried out for the reaction OH + C2H6 --> H2O + C2H5 using second-order Moller-Plesset perturbation theory and employing a very large basis set. Correlation energy is found to play an important role in determining the barrier height of the saddle point and also the geometry and the vibrational frequencies of both the transition state and the equilibrium points. The final calculated values for the forward and reverse classical barrier heights are 4.0 and 21.6 kcal/mol, respectively. These have been used to treat the kinetics of the reaction in the temperature range from 200 to 3000 K by using interpolated canonical variational transition-state theory and the centrifugal-dominant, small-curvature tunneling approximation, including information at the reactants, products, transition state, and one extra point along the minimum energy path. The calculated rate constants agree well with-experiment over a wide temperature range.