Structure-kinetics relationships of thermodestruction of some framework nitramines

Thermal decomposition of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (HNIW, CL-20) and its oxa-analogs containing four and three nitramine fragments, in the gas phase and in solution predominantly follows the first order kinetics, whereas in the solid phase it proceeds with acceleration. Replacement of the two nitramine groups in the five-membered cycles of the molecule CL-20 by oxa groups practically does not affect the rate of decomposition of oxanitroderivatives in the solid phase. Substitution of the nitro group in one of oxa-nitroderivatives by R = H, NO, COCH₃, CH₂N(NO₂)CH₃ differently affects the rate of decomposition. For R = H the rate of decomposition increases; when R = COCH₃, CH₂N(NO₂)CH₃, it decreases; for R = NO, the rate of decomposition remains constant. For the studied compounds the activation parameters of thermal decomposition are determined in the solution, the gas phase, and the solid phase. In general, the reactivity of nitramines depends on the length of the weakest bond N-NO₂, which is affected by the conformation of the nitro group.