Decomposition of 5-Nitro-2,4-dihydro-3H-1,2,4-triazol-3-one (NTO): Energetics Associated with Several Proposed Initiation Routes

Initial steps for several proposed decomposition mechanisms of NTO have been studied theoretically in order to determine the energies of various reaction intermediates. The methods applied were restricted Hartree−Fock self-consistent field (SCF), single- and double-excitation configuration interaction (CISD), CISD corrected for unlinked quadruple excitations (CISD+Q), and coupled cluster including all single and double substitutions (CCSD) with a double-ζ plus polarization (DZP) basis set. Harmonic vibrational frequencies were computed to characterize the species at the stationary points. The previously reported mechanisms examined include decomposition initiated by C−NO 2 homolysis, migration of ring substituents, and ring-opening processes. On the basis of the energetics of the various schemes, our computations suggest that C−NO 2 bond homolysis is the most probable initial step for unimolecular decomposition of NTO.