Semiclassical Transition State Theory (SCTST) Rate Coefficients for the Unimolecular Decomposition of the Ethoxy (CH₃CH₂O) Radical.

IF 2.7 2区化学 Q3 CHEMISTRY, PHYSICAL

The Journal of Physical Chemistry A Pub Date : 2024-11-21 Epub Date: 2024-11-12 DOI:10.1021/acs.jpca.4c05775

Thanh Lam Nguyen, Gregory H Jones, Bryan Changala, Binod Raj Giri, John R Barker, John F Stanton

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Abstract

The thermal unimolecular decay of ethoxy is important in high-temperature combustion environments where the ethoxy radical is a key reactive intermediate. Two dissociation pathways of ethoxy, including the β-C-C scission to yield CH₃ + CH₂O and the H-elimination to make H + CH₃CHO, were characterized using a high-level coupled-cluster-based composite quantum chemical method (mHEAT-345(Q_Λ)). The former route is found to be dominant while the latter is insignificant, in agreement with previous experimental and theoretical studies. Thermal rate coefficients are calculated for P = 0.001-658 atm (of air) and T = 300-2500 K using semiclassical transition state theory (SCTST) in combination with a pragmatic two-dimensional E,J-resolved master equation (2DME). The effects of tunneling and anharmonicity on the calculated rate constants are also examined. The tunneling factor is found to be inversely dependent on pressure, contrary to previous observations of pressure-dependent tunneling in entrance channels.

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乙氧基 (CH3CH2O) 自由基单分子分解的半经典过渡态理论 (SCTST) 速率系数。

乙氧基的单分子热衰变在高温燃烧环境中非常重要，因为乙氧基自由基是一种关键的反应中间体。利用基于高水平耦合簇的复合量子化学方法（mHEAT-345(QΛ)）表征了乙氧基的两种解离途径，包括β-C-C 裂解生成 CH3 + CH2O 和 H-消除生成 H + CH3CHO。结果发现前一种途径占主导地位，而后一种途径并不重要，这与之前的实验和理论研究结果一致。在 P = 0.001-658 atm（空气）和 T = 300-2500 K 的条件下，使用半经典过渡态理论（SCTST）结合实用的二维 E、J 分辨主方程（2DME）计算了热速率系数。此外，还考察了隧穿和非谐波对计算速率常数的影响。研究发现隧道因子与压力成反比，这与之前在入口通道中观察到的压力依赖性隧道效应相反。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

The Journal of Physical Chemistry A 化学-物理：原子、分子和化学物理

CiteScore

5.20

自引率

10.30%

发文量

922

审稿时长

1.3 months

期刊介绍： The Journal of Physical Chemistry A is devoted to reporting new and original experimental and theoretical basic research of interest to physical chemists, biophysical chemists, and chemical physicists.