Thermal decomposition of energetic materials. 2. Deuterium isotope effects and isotopic scrambling in condensed-phase decomposition of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine

The products formed in the thermal decomposition of octahydro-1,3,5, 7-tetranitro-1,3,5,7-tetrazocine (HMX) have been traced to using mixtures of different isotopically labeled analogues of HMX. The isotopic analogues of HMX used in the experiments include 2H, 13C, 15NO2, 15N sub ring, and 180. The fraction of isotopic scrambling and the extent of the deuterium kinetic isotope effect (DKIE) are reported for the different thermal decomposition products. Isotopic scrambling is not observed for the N-N bond in N20 and the C-H bonds in CH20. Only one of the C-N bonds in N-methylformamide (NMFA) undergoes isotopic scrambling. The lack of complete isotopic scrambling of the N-NO bond in 1- nitroso-3,5,7-trinitro-1,3,5,7-tetrazocine (ONTNTA) is shown to imply that some HMX decomposition occurs in the lattice. The behavior of the DKIE in different mixtures of isotopic analogues of HMX suggests that water probably acts as a catalyst in the decomposition. The results demonstrate that decomposition of HMX in the condensed phase has several reaction branches.... DKIE, Isotope effect, Isotopic scrambling, HMX, NMFA, ONTNTA, Thermal decomposition.