An ab initio study of the reaction of HOCO radicals with NO2: addition/elimination mechanism.

The reaction between HOCO and NO(2) has been examined using the quadratic configuration interaction method to locate the transition states and intermediates involved in the reaction. Analysis of the potential energy surface suggest that two possible intermediates are involved: HOC(O)ONO and HOC(O)NO(2). These new species proceed to form the products, HONO + CO(2) and HNO(2) + CO(2). Reaction channels leading to the formation of CO are energetically noncompetitive with those yielding CO(2). The lower energy pathways produce HONO + CO(2) representing new mechanisms for the formation of HONO, through an exchange of carbon and nitrogen centers.