Abstract
Understanding the mechanism of hydrazine oxidation reaction by OH radical accompanied by the rate constants of all possible pathways is important. They are key parameters to explain the fate of hydrazine in the atmosphere. To reach the mentioned parameters, higher-level calculations by using quantum chemical methods have been implemented comprehensively for reliable channels such as H-abstraction, SN2, and addition/elimination reactions. To estimate the barrier energies of H-abstraction channels accurately, large numbers of the CCSD(T)/X calculations (where X denotes the augmented Dunning and Pople double zeta or triple zeta basis sets) have been applied to the optimized geometries of the MP2/aug-cc-pVTZ, MP2/maug-cc-pVTZ, and M062X/maug-cc-pVTZ levels. Contributions of excited states on the computed potential energy surface have been considered by the MR-MP2 (multi-reference) method in conjunction with the large augmented quadruple zeta, aug-cc-pVQZ, basis sets. The direct dynamic calculations have been carried out using the accurate energies of the CCSD(T) method and the partition functions of the second-order MØller-Plesset perturbation theory, and also by the validated M06-2X method with the aug-cc-pVTZ, and maug-cc-pVTZ basis sets. Finally, The VTST and TST theories have been used to calculate the temperature dependence of rate constants of the considered pathways. Also, the pressure-dependent rate constants of the barrierless pathways have been investigated by the strong collision master equation/RRKM theory.
Atmospheric Reaction of Hydrazine Plus Hydroxyl Radical. I. Reliable Pathways