Computational study on the mechanism and thermodynamic of atmospheric oxidation of HCN with ozone

Oxidation of hydrogen cyanide with ozone on the singlet potential energy surface is carried out using the MP2 and CCSD(T)//MP2 theoretical approaches in connection with the 6-311++G(d,p) basis set. In this reaction, energy barrier of transition states are low, so the reaction of HCN with ozone can occur easily at atmospheric condition. With variety of pre-reactive complex, five types of products are obtained at the MP2 method which four types of them have enough thermodynamic stability at the standard condition. CO2 + HNO are final adducts in a process that is computed to be exothermic by −132.605 kcal/mol in standard enthalpy and spontaneous by −144.166 kcal/mol in Gibbs free energy of reaction. In kinetic viewpoint, the production of OCN + HO2 adducts path with one low level transition state is the most favored path.