Oxidation reaction mechanism and kinetics between OH radicals and alkyl-substituted aliphatic thiols: H-abstraction pathways

IF 2.1 4区 化学 Q3 CHEMISTRY, PHYSICAL
A. Tahan, A. Shiroudi
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引用次数: 2

Abstract

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.
羟基自由基与烷基取代脂肪族硫醇之间的氧化反应机理和动力学:吸氢途径
利用密度泛函理论和各种交换相关泛函以及基准的CBS-QB3量子化学方法,从理论上研究了在惰性(Ar)条件下羟基自由基与CH3SH、C2H5SH、n-C3H7SH和iso-C3H7SH在252-430 K温度范围内的氧化反应的动力学速率常数。利用过渡态理论和统计rice - ramspberger - kassel - marcus理论估计了双分子速率常数。与实验对比证实,在生成相关产物的OH加成反应途径中,第一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,计算了反应的有效速率常数。由于活化能为负,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,最有利的过程是羟基自由基与n-C3H7SH的氧化反应。
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来源期刊
CiteScore
2.10
自引率
0.00%
发文量
5
审稿时长
2.3 months
期刊介绍: The journal covers the fields of kinetics and mechanisms of chemical processes in the gas phase and solution of both simple and complex systems.
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