Ab initio kinetics for the decomposition of monomethylhydrazine (CH₃NHNH₂)

The decomposition kinetics of CH3NHNH2(monomethylhydrazine) is studied with ab initio transition state theory-based master equation analyses. The simple NN and CN bond fissions to produce the radicals CH3NH + NH2or CH3+ NHNH2are expected to dominate the decomposition kinetics. The transition states for these two bond fissions are studied with variable reaction coordinate transition state theory employing directly determined CASPT2/aug-cc-pVDZ interaction energies. Orientation independent corrections for limitations in the basis set and for the effects of conserved mode geometry relaxation are included. The bond dissociation energies are evaluated at the QCISD(T)/CBS//B3LYP/6-311++G(d,p) level. The transition state theory analysis directly provides high pressure dissociation and recombination rate coefficients. Predictions for the pressure dependence and product branching in the dissociation of CH3NHNH2are obtained by solving the master equation.