Understanding the mechanism of hydrazine oxidation reaction by OH radical along with the rate constants of all possible pathways leads to explain the fate of hydrazine in the atmosphere. In this article, the comprehensive mechanisms and kinetics of the hydrazine plus hydroxyl radical reaction have been investigated theoretically at different temperatures and pressures. To achieve the main goals, a series of high levels of quantum chemical calculations have been widely implemented in reliable channels of the H-abstraction, S_N2, and addition/elimination reactions. The energy profile of all pathways accompanied by the molecular properties of the involved stationary points has been characterized at the MP2, M06-2X, and CCSD(T)/CBS levels. To estimate accurate barrier energies of the H-abstraction channels, large numbers of the CCSD (T) calculations in conjunction with various augmented basis sets have been implemented. The direct dynamic calculations have been carried out using the validated M06-2X/maug-cc-pVTZ level, and also by the CCSD(T) (energies) + MP2 (partition functions) level. The pressure-dependent rate constants of the barrierless pathways have been investigated by the strong collision approach. Therefore, the main behaviors of the N₂H₄ + OH reaction have been explored according to the influences of temperature and pressure on the computed rate coefficients within the well-behaved theoretical frameworks of the TST, VTST, and RRKM theories. It has been found that the H-abstraction mechanism (to form N₂H₃) is dominant relative to the S_N2 reaction and OH-addition to the N center of N₂H₄ moiety (to form H₂NOH + NH₂). The computed high pressure limit rate constant of the main reaction pathway, k(298.15) = 7.31 × 10^–11 cm³ molecule⁻¹ s⁻¹, has an excellent agreement with the experimental value (k (298.15) = (6.50 ± 1.3) × 10^–11 cm³ molecule⁻¹ s⁻¹) recommended by Vaghjiani. Also, the atmospheric lifetime of hydrazine degradation by OH radicals has been demonstrated to be 32.80 to 1161.11 h at the altitudes of 0–50 km. Finally, the disagreement in the calculated rate constants between the previous theoretical study and experimental results has been rectified.

了解 OH 自由基氧化肼的机理以及所有可能途径的速率常数，可以解释肼在大气中的命运。本文从理论上研究了肼加羟基自由基反应在不同温度和压力下的综合机理和动力学。为了实现主要目标，一系列高水平的量子化学计算已在 H 抽象的可靠通道中广泛实施，S _N2、加成/消去反应。所有通路的能量分布以及所涉及的静止点的分子特性已在 MP2、M06-2X 和 CCSD(T)/CBS 水平上进行了表征。为了估计 H 抽象通道的准确势垒能量，已经实施了大量 CCSD (T) 计算以及各种增强基组。已经使用经过验证的 M06-2X/maug-cc-pVTZ 级别以及 CCSD(T)（能量）+ MP2（分区函数）级别进行了直接动态计算。通过强碰撞方法研究了无障碍路径的压力相关速率常数。因此，N ₂ H ₄的主要行为 在 TST、VTST 和 RRKM 理论的良好理论框架内，根据温度和压力对计算的速率系数的影响，探索了 + OH 反应。已经发现的是，H-抽象机制（以形成N- ₂ ħ ₃）相对于主导向S _Ñ 2反应和OH加成到N的N中心₂ ħ ₄部分（以生成H ₂ NOH + NH ₂）。计算出的主要反应途径的高压极限速率常数，k(298.15) = 7.31 × 10 ^–11  cm ³分子^-1  s ^-1, 与Vaghjiani 推荐的实验值 (k (298.15) = (6.50 ± 1.3) × 10 ^–11  cm ³分子^-1  s ^-1 ) 具有极好的一致性。此外，在海拔 0-50 公里处，OH 自由基降解肼的大气寿命已被证明为 32.80 至 1161.11 小时。最后，纠正了先前理论研究和实验结果之间计算速率常数的分歧。