Abstract
The low-lying electronic states of dioxirane (1), their ring opening to dioxymethane (2), and the dissociation of 2 into CO2 and H2 have been investigated by means of CASSCF and MRD-CI+Q quantum chemistry calculations. The ground state of 1 is a singlet with 4π electrons, 11A1(4π), while the ground state of 2 is a 2π-electron singlet, 11A1(2π), lying 5.8 kcal/mol higher than 1 in energy. A 0 K activation energy of 21.4 kcal/mol is predicted for the thermal ring opening of 1 into 2, which takes place via a transition structure approximately corresponding to the crossing between the lower 1A1(4π) and 1A1(2π) states of both molecules. Twelve excited states have been calculated for 1 with vertical excitation energies ranging from 3.07 to 13.11 eV. The energy ordering of these states changes dramatically upon relaxation of the molecular geometries. The optimum geometries of these excited states show an ∠OCO in the 106.3−120.1° range, so they should be considered as excited states of 2. Minimum energy points of...
Published Version
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