Theoretical Study of Extensive Hydrogen Abstraction Reactions for 2-Hydroxyethylhydrazine (HEH)

Energetic ionic liquids have a high potential to replace the traditional monopropellant hydrazine as a high-energy green propellant and can be widely used in aerospace technology. A high-energy ionic liquid─HEHN has also gained extensive attention from researchers. To explore the reaction mechanism of HEHN and establish a chemical kinetic model for high-energy ionic liquid propellants, 28 hydrogen abstraction reactions of HEH, which is the main decomposition product of HEHN, were investigated in this study. Seven abstractors were involved, including ^•H, ^•OH, NO₂, HO₂^•, ^•CH₃, CH₃O^•, and CH₃O₂^•. In the case of ab initio calculations, the M06-2X/6311++G(d,p) approach was utilized for geometry optimization, determination of vibrational frequencies, and dihedral scans. The CCSD/cc-pVXZ (X = T, Q) level of theory was used to calculate the single-point energies (SPEs). The rate coefficients of all 28 reactions and the thermochemical parameters of all involved species were determined. The results indicate that the rate of hydrogen abstraction at the -NH site is faster than that at other sites at relatively low temperatures. For all four abstraction sites, HEH + ^•H, ^•OH, and CH₃O^• have higher reaction rates than HEH + CH₃O₂^• and HO₂^•. In particular, NO₂ systems at the -NH and -NH₂ sites even begin to show higher reactivity than the ^•H, ^•OH, and CH₃O^• systems when the temperature is above ∼1100 K.