Kinetics, mechanism and thermodynamics of reactions of hydrazine with CH₃ and OOH radicals

Abstract

Reactions of hydrazine with CH₃ and OOH radicals including hydrogen abstractions and substitution reactions were studied using computational methods. Activation energies of the reactions were calculated by MP2, M062X and B3LYP methods. M062X activation energies of hydrogen abstraction from N₂H₄ by CH₃ and OOH radicals were 21.89 and 25.24 kJ mol⁻¹, respectively. Generally, activation energies of the hydrogen abstractions were smaller than those of substitution reactions. Rate constants of the reactions were calculated using the transition state theory and M062X method in a temperature range of 200–2500 K. Rate constants of hydrogen abstraction from hydrazine by CH₃ and OOH radicals were 3.47 × 10⁻¹³ and 6.79 × 10⁻¹³ cm³ mol⁻¹ s⁻¹, respectively, at 298 K. Enthalpies (∆H) and Gibbs free energies (∆G) of the reactions were calculated employing CBS-Q, MP2 and B3LYP methods. Hydrogen abstractions were exothermic while almost all the substitution reactions were endothermic. One of the NH₂ groups of N₂H₄ can be replaced with CH₃ or OOH radicals, which leads to NH₂CH₃ or NH₂OOH products, respectively. Formation of NH₂CH₃ was exothermic while production of NH₂OOH was an endothermic reaction.