The reaction of NH2 (X 2B1) with O (X 3P): A theoretical study employing Gaussian 2 theory

The ground 2A″ and excited 4A′ surfaces for the reaction of NH2 (X 2B1) with O (X 3P), have been characterized by calculating energies, geometries, and frequencies for all important stationary points connecting reactants and products. The Gaussian 2 methodology was used for all calculations with further refinement for transition state properties made by calculating energies using QCISD/6–311G(d,p) geometries and frequencies. The results predict that, on the 2A″ surface, an H2NO intermediate is formed which is 87.6 kcal/mol below the separated NH2+O reactants. This intermediate may either fragment to form H+HNO or H2+NO, or undergo a 1,2 hydrogen shift to form trans-HNOH. This second intermediate may dissociate to either NH+OH or H+HNO, or isomerize to cis-HNOH which, in turn, may dissociate into the same products. The abstraction reaction NH2+O→NH+OH was found to have a transition state 6.7 kcal/mol above the energy of the separated reactants.