Ab initio calculation on the rate constants of the reaction H2O2Â +Â Cl

Ab initio calculations followed by transition state theory (TST) treatment are performed to investigate the gas phase elementary bimolecular reaction of hydrogen peroxide with chlorine atom H2O2 + Cl. The electronic structure calculations are done using the post Hartree-Fock MCQDPT2//CASSCF approach and the aug-cc-pVTZ basis set. Two reaction pathways are considered: the H-abstraction path (denoted as path1) and the OH-abstraction one (denoted as path2). For each path, the activated complex is located. The zero point vibrational energy corrected values of the classical barrier heights were predicted to be 3.2 and 10.4 kcal/mol for path1 and path2, respectively. Reaction rate constants are calculated for the temperature range 200-2500 K using the transition state theory (TST) incorporating a Zero-Curvature Tunneling correction. The results of theoretical rate constants for path1 are in good agreement with the available experimental data. The calculated branching ratios show that the H-abstraction path is the most probable process occurring for temperatures below 1500 K confirming hence the experimental findings. The contribution of path2 to the reaction dominates at higher temperatures.