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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Ab Initio Chemical Kinetics for the CH3 + O(P-3) Reaction and Related Isomerization-Decomposition of CH3O and CH2OH Radicals
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Ab Initio Chemical Kinetics for the CH3 + O(P-3) Reaction and Related Isomerization-Decomposition of CH3O and CH2OH Radicals

机译：CH3 + O（P-3）反应的从头算化学动力学及相关的CH3O和CH2OH自由基的异构化分解

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摘要

The kinetics and mechanism of the CH3 + O reaction and related isomerization-decomposition of CH3O and CH2OH radicals have been studied by ab initio molecular orbital theory based on the CCSD(T)/aug-cc-pVTZ//CCSD/aug-cc-pVTZ, CCSD/aug-cc-pVDZ, and G2M//B3LYP/6-311+G(3df,2p) levels of theory. The predicted potential energy surface of the CH3 + O reaction shows that the CHO + H-2 products can be directly generated from CH3O by the TS3 -> LM1 -> TS7 -> LM2 -> TS4 path, in which both LM1 and LM2 are very loose and TS7 is roaming-like. The result for the CH2O + H reaction shows that there are three low-energy barrier processes including CH2O + H -> CHO + H-2 via H-abstraction and CH2O + H -> CH2OH and CH2O + H -> CH3O by addition reactions. The predicted enthalpies of formation of the CH2OH and CH3O radicals at 0 K are in good agreement with available experimental data. Furthermore, the rate constants for the forward and some key reverse reactions have been predicted at 200-3000 K under various pressures. Based on the new reaction pathway for CH3 + O, the rate constants for the CH2O + H and CHO + H-2 reactions were predicted with the microcanonical variational transition-state/Rice-Ramsperger-Kassel-Marcus (VTST/RRKM) theory. The predicted total and individual product branching ratios (i.e., CO versus CH2O) are in good agreement with experimental data. The rate constant for the hydrogen abstraction reaction of CH2O + H has been calculated by the canonical variational transition-state theory with quantum tunneling and small-curvature corrections to be k(CH2O + H -> CHO + H-2) = 2.28 x 10(-19) T-2.65 exp(-766.5/T) cm(3) molecule(-1) s(-1) for the 200-3000 K temperature range. The rate constants for the addition giving CH3O and CH2OH and the decomposition of the two radicals have been calculated by the microcanonical RRKM theory with the time-dependent master equation solution of the multiple quantum well system in the 200-3000 K temperature range at 1 Torr to 100 atm. The predicted rate constants are in good agreement with most of the available data.
机译：基于CCSD（T）/ aug-cc-pVTZ // CCSD / aug-cc-CHS的从头算分子轨道理论，研究了CH3 + O反应的动力学和机理以及相关的CH3O和CH2OH自由基的异构化分解。 pVTZ，CCSD / aug-cc-pVDZ和G2M // B3LYP / 6-311 + G（3df，2p）的理论水平。 CH3 + O反应的预测势能面表明CHO + H-2产物可以通过TS3-> LM1-> TS7-> LM2-> TS4路径从CH3O直接生成，其中LM1和LM2都是非常松散，TS7像漫游一样。 CH2O + H反应的结果表明，存在三种低能垒过程，包括通过H吸收的CH2O + H-> CHO + H-2和通过加成反应的CH2O + H-> CH2OH和CH2O + H-> CH3O 。在0 K时CH2OH和CH3O自由基形成的预测焓与可用的实验数据高度吻合。此外，在各种压力下，正向反应和一些关键逆向反应的速率常数已在200-3000 K下预测。基于CH3 + O的新反应途径，利用微经典变分过渡态/ Rice-Ramsperger-Kassel-Marcus（VTST / RRKM）理论预测了CH2O + H和CHO + H-2反应的速率常数。预测的总和单个产品支化比（即CO与CH2O）与实验数据非常吻合。 CH2O + H的氢提取反应的速率常数已通过经典的变分跃迁状态理论，量子隧穿和小曲率校正计算为k（CH2O + H-> CHO + H-2）= 2.28 x 10 200至3000 K温度范围的（-19）T-2.65 exp（-766.5 / T）cm（3）分子（-1）s（-1）。通过微规范RRKM理论，使用多量子阱系统在1 Torr时的200-3000 K温度范围内的时变主方程解，计算了添加CH3O和CH2OH以及两个自由基分解的速率常数。到100 atm预测的速率常数与大多数可用数据非常吻合。

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