Reactions of NO2 with CH3NHNH and CH3NNH2: A direct molecular dynamics study

Reactive collisions between CH3NNH2 + NO2 and CH3NHNH + NO2 were observed via direct molecular dynamics simulations. The simulations, which are classical trajectories whose dynamics were dictated by forces derived from quantum mechanics-based calculations, were conducted: (1) to confirm the importance of reaction paths expected to play a role in the ignition and combustion of monomethylhydrazine/nitrogen tetroxide (MMH/NTO) and monomethylhydrazine/red fuming nitric acid (MMH/RFNA) systems, and (2) for their potential to identify unexpected mechanisms. A number of different H-atom abstraction paths were observed, with four isomeric (CH4N2) products being formed: CH3NNH, CH3NHN, H2CNNH2, and CH2NHNH. All abstractions were barrierless, including those from the methyl group. Reaction exothermicities, which were characterized via QCISD/6-311+G(d,p)//MPWB1K/6-31+G(d,p) calculations, ranged from 2 to 36 kcal/mol. The results suggest that finite rate chemical kinetics mechanisms for MMH/NTO and MMH/RFNA systems should include steps for the production and decomposition of CH3NHNH, H2CNNH2, CH2NHNH, and CH3NHN in addition to those for CH3NNH2 and CH3NNH.