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

摘要

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 x 10(-13) and 6.79 x 10(-13) cm(3) mol(-1) s(-1), respectively, at 298 K. Enthalpies (a dagger H) and Gibbs free energies (a dagger 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.