Theoretical studies on the kinetics of the hydrogen-abstraction reactions from 1,3,5-trioxane and 1,4-dioxane by OH radicals

IF 2.1 4区 化学 Q3 CHEMISTRY, PHYSICAL
V. Saheb, Aidin Bahadori
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引用次数: 1

Abstract

Theoretical investigations have been performed on the kinetics of bimolecular hydrogen-abstraction reactions of 1,3,5-trioxane and 1,4-dioxane cyclic ethers with OH radicals. Hydrogen abstraction from both axial and equatorial positions of 1,3,5-trioxane and 1,4-dioxane was considered. Optimization of the structures, and the calculation of energies, vibrational frequencies and moments of inertia for all the stationary points including reactants, hydrogen-bonded complexes, transition states and products were carried out using density functional theory at the M06-2X level together with the MG3S basis set. Single-point energy calculations on the optimized points were obtained at the CBS-QB3 level. The calculations show that the title reactions proceed through relatively strong hydrogen-bonded complexes due to the hydrogen bonding between the OH radicals and the oxygen atoms of the cyclic ethers. A two-transition state model (an inner tight transition state and an outer loose transition state) was employed to compute the hydrogen-abstraction rate coefficients. The rate coefficients were also computed using conventional transition state theory considering a tight transition state for the purpose of comparison. It was found that when the reactions proceed via inner transition states with relative energies higher than the reactants, the computed rate coefficients are underestimated by conventional transition state theory.
羟基自由基对1,3,5-三氧环和1,4-二氧环吸氢反应动力学的理论研究
对1,3,5-三氧环醚和1,4-二氧环醚在OH自由基作用下的双分子吸氢反应动力学进行了理论研究。考虑了1,3,5-三氧环和1,4-二氧环的轴位和平位吸氢。利用M06-2X水平的密度泛函理论,结合MG3S基集,对结构进行了优化,计算了包括反应物、氢键配合物、过渡态和产物在内的各驻点的能量、振动频率和转动惯量。在CBS-QB3水平上对优化点进行单点能量计算。计算表明,由于羟基自由基与环醚氧原子之间的氢键作用,标题反应通过较强的氢键配合物进行。采用双过渡态模型(内紧过渡态和外松过渡态)计算抽氢速率系数。为了便于比较,采用传统的过渡态理论计算了速率系数,并考虑了紧过渡态。研究发现,当反应通过相对能量高于反应物的内过渡态进行时,传统的过渡态理论低估了反应速率系数。
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
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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