Quantum chemical and theoretical kinetics studies on the reaction of hydroperoxyl radical with chlorine atom

Abstract

The singlet and triplet potential energy surfaces for the reaction of HO2 radical with Cl atom are explored by using high-level combination W1BD and W1U methods. Statistical rate theories are employed to compute the rate coefficients of the main product channels including HCl + O2( $$ ^{1} \Sigma _{u}^{ - } $$ ), HCl + O2( $$ ^{3} \Sigma _{g}^{ + } $$ ), OH + ClO and HOOCl as a function of pressure and temperature. It is found that the rate coefficients for the product channels OH + ClO and HOOCl are strongly depended on temperature and pressure. At lower pressures and higher temperatures, the product OH + ClO is important, while at higher pressures and lower temperatures, HOOCl is the dominant product. At some moderate temperatures and pressures, the rate coefficients for the formation of OH + ClO and HOOCl could be equal. The product channel HCl + O2( $$ ^{3} \Sigma _{g}^{ + } $$ ) proceeds via formation of a van der Waals complex Cl..HOO and, next, passes through a saddle point structure with a negative energy of − 5.0 kJ mol−1 relative to the reactants. It is shown that a two transition state model suitably describes the kinetics of this product channel.