Kinetic rate constants for the oxidation reaction of the hydroxyl radical with CH3SH, C2H5SH, n-C3H7SH, and iso-C3H7SH under inert (Ar) conditions over the temperature range 252–430 K have been studied theoretically using density functional theory along with various exchange–correlation functionals as well as the benchmark CBS-QB3 quantum chemical approach. Bimolecular rate constants were estimated using transition state theory and the statistical Rice–Ramsperger–Kassel–Marcus theory. Comparison with experiment confirms that in the OH addition reaction pathways leading to the related products, the first bimolecular reaction steps have effective negative activation energy barriers. Effective rate constants have been calculated according to a steady-state analysis of a two-step model reaction mechanism. As a consequence of the negative activation energies, pressures higher than 104 bar are required to reach the high-pressure limit. Both from thermodynamic and kinetic viewpoints, the most favorable process here is the oxidation reaction of hydroxyl radicals with n-C3H7SH.

中文翻译：

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OH自由基与烷基取代的脂肪族硫醇之间的氧化反应机理和动力学：H-抽象途径

在惰性 (Ar) 条件下，在 252-430 K 的温度范围内，羟基自由基与 CH3SH、C2H5SH、n-C3H7SH 和 iso-C3H7SH 的氧化反应动力学速率常数已使用密度泛函理论以及各种交换进行了理论研究。 – 相关泛函以及基准 CBS-QB3 量子化学方法。使用过渡态理论和统计赖斯-拉姆斯伯格-卡塞尔-马库斯理论估计双分子速率常数。与实验比较证实，在产生相关产物的 OH 加成反应途径中，第一个双分子反应步骤具有有效的负活化能垒。根据两步模型反应机理的稳态分析计算了有效速率常数。由于负活化能，需要高于 104 bar 的压力才能达到高压极限。从热力学和动力学的角度来看，这里最有利的过程是羟基自由基与 n-C3H7SH 的氧化反应。