Ab initio study of the hydrogen abstraction reaction H2O2+OH→HO2+H2O

Elementary hydrogen abstraction reaction between OH radical and H2O2 molecule to yield H2O and HO2 molecules has been investigated by ab initio molecular orbital calculations. In addition to the well known reactants and products structures we have located two stationary structures, an intermediate complex OH-H2O2 and a transition state H3O3 structures. The binding energy of OH-H2O2 and the reaction energy are predicted to be, respectively, -3.7 and -31.4 kcal mol(-1). The activated complex is found to be more stable than the reactants by 0.9 kcal mol(-1) and less stable than the intermediate complex by 2.8 kcal mol(-1). These results are used to give a tentative explanation of the observed anomalous behavior of the measured rate constant k(T) as a function of temperature T and to try for an interpretation on the physical origin of the two terms in the, non-Arrhenius, fitted expression of k(T) proposed by Hipler et al. k(T) = [2.0 x 10(12) exp(-215 K/T) +1.7 x 10(18) exp(-14,800 KIT)]cm(3) Mol(-1) S-1 for 240 less than or equal to T less than or equal to 1600 K. (C) 2003 Elsevier B.V. All rights reserved.