Unexpected
Primary Reactions for Thermolysis of 1,1-Diamino-2,2-dinitroethylene (FOX-7) Revealed by <i>ab Initio</i> Calculations
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Abstract
The primary thermolysis reactions
of a promising insensitive explosive
1,1-diamino-2,2-dinitroethylene (DADNE, FOX-7) have been studied in
the gas phase at a high level of theory (CCSD(T)-F12/aVTZ). Our calculations
revealed that none of the conventional reactions (C–NO<sub>2</sub> bond fission, nitro-nitrite and nitro-aci-nitro rearrangements)
dominate thermolysis of FOX-7. On the contrary, two new decomposition
pathways specific for this particular species that commenced with
enamino–imino isomerization and intramolecular cyclization
were found instead to be more feasible energetically. The activation
barriers of these primary isomerization reactions were calculated
to be 48.4 and 28.8 kcal/mol, while the activation energies of the
overall decomposition pathways are predicted to be ∼49 and
∼56 kcal/mol, respectively. The new pathways can also be relevant
for a wide series of unsaturated hydrocarbons substituted with both
nitro- and amino-groups (e.g., triaminotrinitrobenzene, TATB)