Ribeiro Joao Marcelo, Mebel Alexander M
Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA.
Phys Chem Chem Phys. 2017 Jun 7;19(22):14543-14554. doi: 10.1039/c7cp01873h.
Two ground-state CH radical reactions with the CH isomers allene and methylacetylene occurring along the CH potential energy surface (PES) were studied to probe the reaction mechanisms and final product distributions. The calculations were performed using a CCSD(T)-F12//B2PLYPD3 PES in combination with the 1-D chemical master equation. The reaction between the CH radical and allene was found to lead to exclusive "funneling" of the energized CH intermediates into linear CH configurations before reaching the exit channels, regardless of the specific nature of the initial bimolecular reactive encounter. In the case of the CH radical reaction with methylacetylene, energized CH three-membered ring structures underwent H loss in significant amounts resulting in the production of a cyclic CH methylenecyclopropene product, in accordance with experiments. The theoretical product distribution at room temperature for methylacetylene + CH was ∼35% methylenecyclopropene, ∼36% vinylacetylene, and ∼28% 1,2,3-butatriene, which is in agreement with the available experimental data. The distribution for allene + CH was ∼93% vinylacetylene, ∼4% 1,2,3-butatriene and ∼3% acetylene + vinyl, which overestimates the experimental yield of vinylacetylene and underestimates that of 1,2,3-butatriene by ∼10%. The possible reasons for this slight quantitative deviation of the theoretical results obtained within statistical treatment from the experiment are discussed.
研究了基态CH自由基与丙二烯和甲基乙炔这两种CH异构体沿CH势能面（PES）发生的两个反应，以探究反应机理和最终产物分布。计算使用CCSD(T)-F12//B2PLYPD3势能面结合一维化学主方程进行。发现CH自由基与丙二烯之间的反应，无论初始双分子反应碰撞的具体性质如何，在到达出口通道之前，都会使激发态的CH中间体完全“汇聚”成线性CH构型。在CH自由基与甲基乙炔的反应中，激发态的CH三元环结构大量发生氢损失，从而产生环状CH亚甲基环丙烯产物，这与实验结果一致。室温下甲基乙炔 + CH的理论产物分布约为35%亚甲基环丙烯、约36%乙烯基乙炔和约28% 1,2,3-丁三烯，这与现有实验数据相符。丙二烯 + CH的分布约为93%乙烯基乙炔、约4% 1,2,3-丁三烯和约3%乙炔 + 乙烯基，该结果高估了乙烯基乙炔的实验产率，而低估了1,2,3-丁三烯的实验产率约10%。讨论了在统计处理中获得的理论结果与实验结果存在这种轻微定量偏差的可能原因。
