Electronic structure and the unimolecular reactions of imine peroixde HNOO

Summary Electronic structure and possible unimolecular reaction paths of a linear four-atom molecule HNOO to be formed by the addition of NH(^3–) toward O₂(³ _g ^– ) are investigated by the SCF and MRD-CI calculations employing the 6–31G** basis functions. HNOO in its ground state (¹ A) is an ozone-like diradicaloid, whose N–O binding energy is only 27 kJ/mol. Geometries and excitation energies of various diradical (excited) states, both singlet and triplet, are examined. The isomerization paths of the ground-state HNOO(¹ A) are traced by a multi-configuration (MC) SCF procedure and the activation barrier heights evaluated by the CI treatment. It has proved that energetically the most favorable is the 1,3-hydrogen migration to give hydroperoxynitrene NOOH(¹ A) with the barrier height of 62 kJ/mol. The nitrene should be extremely unstable; it is liable to be decomposed to NO + OH with virtually no activation barrier.Presented at the 7th International Congress on Quantum Chemistry, Menton, July 1991