Hydrogen abstraction reactions of hydroxyl radicals with 1,1,2,2-tetrachloroethane, 1,1,1,2-tetrachloroethane and pentachloroethane studied by using semi-classical transition state theory

The hydrogen abstraction reactions by OH radicals from CHCl₂CHCl₂ (R1), CH₂ClCCl₃ (R2) and C₂HCl₅ (R3) are investigated theoretically by semi-classical transition state theory. Many high-level density functional, <i>ab initio</i> and combinatory electronic structure calculation methods are used to evaluate the energies and ro-vibrational properties of the stationary points for the title reactions. <i>x_ij</i> vibrational anharmonicity coefficients, needed for semi-classical transition state theory, are calculated at the KMLYP/cc-pVTZ level of theory. Thermal rate coefficients are computed over the temperature range from 200 to 2000 K and compared with available experimental data. The computed rate constants for the reactions R1, R2 and R3 are fitted to the equation <i>k</i>(<i>T</i>) = <i>ATⁿ</i>exp [ − <i>E</i>(<i>T</i> + <i>T</i>₀)/(<i>T</i>² + <i>T</i>²₀)].