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The mechanism of thermal decomposition of secondary nitramines

“…Many structural analogues of hexogen, e.g., trinitrosohexogen and 1,3,3,5,5-pentanitropiperazine, are also characterised by negative activation volumes in THF. 52 Other hexogen analogues, including octogen, that were studied in acetonitrile (but not in THF), which was inert in this concrete case, 55 have positive activation volumes.…”

“…The DKIE was observed in all solvents that accelerate the decomposition, and typical inhibitors of chain reactions (e.g., NO, NO 2 , p-dinitrosobenzene) bring the rate constant down to a level characteristic of inert solvents. These data altogether led to a hypothesis 53 on a chain decomposition mechanism of hexogen in solvents containing reactive C7H bonds and a monomolecular mechanism for this decomposition in inert media. Detailed kinetic schemes for both mechanisms were developed and rationalised; it was shown that they are consistent with the experimental data.…”

“…Detailed kinetic schemes for both mechanisms were developed and rationalised; it was shown that they are consistent with the experimental data. 53,55 An example of a non-chain decomposition mechanism of hexogen in solutions is given in Scheme 2.…”

“…Chain decomposition of hexogen in solution (RH is the solvent) is presented in Scheme 3. 55 Scheme 3…”

“…Despite their obvious incompleteness, the schemes of monomolecular (see Scheme 2) and chain decomposition of hexogen (see Scheme 3) in solutions 53,55 provide an explanation for the principal experimental results, e.g., the dependence of the yields of gaseous products on the concentration of hexogen, high yields of mononitrosohexogen in very dilute solutions of inert solvents, cage effects and, what is even more important, enhancing effects of some solvents and the negative activation volumes in the decomposition of hexogen in THF.…”