Kinetic study of the hydrogen abstraction reaction H 2O 2+H→H 2+HO 2 by ab initio and density functional theory calculations

Abstract

A theoretical kinetic study of the elementary chemical reaction involving hydrogen atom abstraction from hydrogen peroxide by hydrogen atom leading to H 2 molecule and HO 2 radical was reported. Rate constants were calculated using transition state theory. The values of the kinetic parameters, the classical barrier height and the pre-exponential factor, were derived from ab initio (MP2//CASSCF) and density functional theory calculations of the electronic structure of each chemical species implied in the title reaction using the aug-cc-pVTZ basis set. Two hybrid BHHLYP and B3LYP functionals were used. The ZPE and BSSE corrected classical barrier height was predicted to be 9.31 and 2.34 kcal mol −1, respectively, for the two used DFT methods and 8.08 kcal mol −1 for the ab initio calculation. The experimental value derived from fitted Arrhenius expressions ranges from 3.75 to 9.44 kcal mol −1. The rate constants based on the ab initio and on the BHHLYP calculations were found to be in reasonable agreement with the available observed ones. However, those based on the B3LYP calculation were found to be far from accurately predicted.