Hydrogen atom abstraction from HOOOCl by chlorine atom and OH radical

Gas phase reactions of HOOOCl with both Cl atom and OH radical are investigated using ab-initio methods. The structures of reactants, products, intermediates and transition states are characterized with the QCISD method. The overall mechanism for the Cl + HOOOCl and OH + HOOOCl reactions is the formation of HCl + O2 + CO and H2O + O2 + CO respectively. The rate-limiting step in each reaction is the abstraction of hydrogen from HOOOCl by either Cl or OH radicals and the barrier height is predicted to be 1.9 kcal/mol and 8.1 kcal/mol for abstraction for Cl and OH, respectively. Since both barriers for abstraction are high, the reaction is suggested to be slow. These results also suggest that an atmospheric removal mechanism for HOOOCl may result from reaction with Cl atoms rather than with OH radicals, and that photolysis of HOOOCl may be the major removal mechanism for the intermediate.