Theoretical studies of the NTO unimolecular decomposition

This work studies 39 decomposition paths among 18 intermediates and 14 transition states. Three types of intra-molecular proton migration and the direct scission of C–NO₂ were regarded as the initial steps of the unimolecular decomposition of NTO. The activation energies of the radicalization C–NO₂ homolysis step are 79.158, 79.781 and 80.652 kcal mol⁻¹. The activation energies of the ionization C–NO⁻¹₂ scission step are 262.488, 263.138 and 272.278 kcal mol⁻¹. The bottle neck activation energies of the C–NO₂H cleavage are 54.936, 63.257 and 71.247 kcal mol⁻¹. Two paths have the smallest bottle neck activation energy. Both of them have two proton migration steps and one internal rotation step prior to C–NO₂H cleavage. At lower temperatures, energy accumulated slowly. When the energy is high enough and reaction time is long enough for structure transformation, these two mechanisms should be the most probable decomposition paths. At high temperatures, the shortest (four steps) mechanism which goes through radicalization C–NO₂ scission should be the dominant path. There are five tautomers found in this study. Four of them are intra-molecular proton migration tautomers. The other one is an internal rotational tautomer. Their energy barriers for structure transfer are lower than any of the activation energies of the decomposition reactions. It may be regarded as one explanation of the insensitive property of NTO.