Gao Yi, Zhao Yang, Guan Qingbao, Wang Fuke
Center for Combustion Energy, Key Laboratory for Thermal Science and Power Engineering of MOE, Tsinghua University Beijing 100084 China
Soft Materials, Institute of Materials Research and Engineering, Agency for Science, Technology and Research (ASTAR) 2 Fusionopolis Way, #08-03 Innovis 138634 Singapore.
RSC Adv. 2020 Sep 8;10(55):33205-33212. doi: 10.1039/d0ra05332e. eCollection 2020 Sep 7.
The existence of pre- and post-reaction complexes has been proposed to influence hydrogen abstraction reaction kinetics, but the significance still remains controversial. A theoretical study is presented to discuss the effects of complexes on hydrogen abstraction from 2-butanone by OH radicals based on the detailed PESs at the DLPNO-CCSD(T)/aug-cc-pVTZ//M06-2x-D3/may-cc-pVTZ level with five pre-reaction complexes at the entrance of the channels and four post-reaction complexes at the exit. The hydrogen bond interactions, steric effects, and contributions to the bonding orbital of the OH radical species and 2-butanone species in the complex structures were visualized and investigated by wavefunction analyses. Three kinds of mechanisms-the general bimolecular reaction, the reaction with the complexes considered, and the well-skipping reaction-were compared based on high-pressure-limit rate constants, predicted branching ratios, and fractional populations of reactants and products in the temperature range of 250-2000 K. The existence of complexes was proved to be crucial in the kinetics and mechanisms of the hydrogen abstraction from 2-butanone molecules by OH radicals.
预反应和反应后复合物的存在被认为会影响氢提取反应动力学，但其重要性仍存在争议。本文基于DLPNO-CCSD(T)/aug-cc-pVTZ//M06-2x-D3/may-cc-pVTZ水平的详细势能面，在通道入口处有五个预反应复合物，出口处有四个反应后复合物，进行了一项理论研究，以探讨复合物对OH自由基从2-丁酮中提取氢的影响。通过波函数分析，可视化并研究了复合物结构中OH自由基物种和2-丁酮物种的氢键相互作用、空间效应以及对成键轨道的贡献。基于高压极限速率常数、预测的分支比以及250-2000 K温度范围内反应物和产物的分数丰度，比较了三种机制——一般双分子反应、考虑复合物的反应和跳过势阱反应。结果证明，复合物的存在对于OH自由基从2-丁酮分子中提取氢的动力学和机制至关重要。
