Ab initio study on the mechanism of tropospheric reactions of the nitrate radical with alkenes: Propene

A mechanism for the reaction of the NO3 radical with propene is proposed on the basis of B3LYP and CASSCF; calculations. The mechanism involves initia lly both Markownikoff and contra-Markownikoff oriented addition on the doub le bond. From the initial radical adducts several interconnected pathways h ave been found, giving 1,2-epoxypropane, propanal, propenol, propanone, for maldehyde, ethanal, NO, and NO2. The geometries of the stationary points fo und on the potential energy hypersurface (PES) were obtained and characteri zed by means of density functional theory (DFT) B3LYP/6-31G* calculations. Comparison of the optimized geometries on a limited number of molecular str uctures was carried out with calculations at the CASSCF level of theory wit h the same basis set, building the active space with five electrons in six orbitals.