Bimolecular Reactions between Dimethylnitramine and Its Radical Decomposition Products.

Bimolecular reactions between intact nitramines and their radical decomposition products can accelerate thermal decomposition, yet the detailed mechanisms of such reactions are not well understood. We have used density functional theory at the M06/6-311++G(3df,3pd) level to locate transition structures and compute 0 K activation barriers for various gas-phase reactions that may contribute to radical-assisted decomposition of dimethylnitramine (DMNA, (CH3)2NNO2). Our calculations indicate that H abstraction from DMNA is the lowest-barrier mechanism for most radicals and a subsequent N-N β-scission in the alkyl radical 3 leads to an imine intermediate and NO2. H abstraction is thus responsible for conversion of most radicals to NO2. Also, among the nine radicals considered, NO is found to be least reactive and its reactions with DMNA yield dimethylnitrosoamine (DMNSA, (CH3)2NNO), a known product of DMNA decomposition.