Theoretical study on the reaction of atomic oxygen with unsymmetrical dimethylhydrazine

Abstract

A dual-level direct dynamics method is employed to study the reaction mechanism of (CH3)2NNH2 (unsymmetrical dimethylhydrazine) with the oxygen (O) atom. The geometries and frequencies of all the stationary points are optimized at the MPW1K/6-311G (d, p) level, and the energy profiles are further refined by the interpolated single-point energies (ISPE) method at the BMC-CCSD level of theory. The rate constants of the O atom with (CH3)2NNH2 are evaluated over a wide temperature range of 200–2000 K by using the canonical variational transition-state theory (CVT) with the small curvature tunneling correction (SCT). The agreement between the theoretical and experimental rate constants is good around room temperature. The channels of H abstraction from the -NH2 position favor temperatures below 1200 K. With increasing temperature, contributions from other channels should be taken into account. The reactivity of N2H4, CH3NHNH2, and (CH3)2NNH2 toward atomic O is compared to explore the methylation effect.