Bourgalais Jeremy, Caster Kacee L, Durif Olivier, Osborn David L, Le Picard Sebastien D, Goulay Fabien
LATMOS/IPSL , UVSQ Université Paris-Saclay , Sorbonne Université, CNRS, 78280 Guyancourt , France.
Department of Chemistry , West Virginia University , Morgantown , West Virginia 26506 , United States.
J Phys Chem A. 2019 Mar 21;123(11):2178-2193. doi: 10.1021/acs.jpca.8b11688. Epub 2019 Mar 8.
Reactions of the methylidyne (CH) radical with ammonia (NH), methylamine (CHNH), dimethylamine ((CH)NH), and trimethylamine ((CH)N) have been investigated under multiple collision conditions at 373 K and 4 Torr. The reaction products are detected by using soft photoionization coupled to orthogonal acceleration time-of-flight mass spectrometry at the Advanced Light Source (ALS) synchrotron. Kinetic traces are employed to discriminate between CH reaction products and products from secondary or slower reactions. Branching ratios for isomers produced at a given mass and formed by a single reaction are obtained by fitting the observed photoionization spectra to linear combinations of pure compound spectra. The reaction of the CH radical with ammonia is found to form mainly imine, HN═CH, in line with an addition-elimination mechanism. The singly methyl-substituted imine is detected for the CH reactions with methylamine, dimethylamine, and trimethylamine. Dimethylimine isomers are formed by the reaction of CH with dimethylamine, while trimethylimine is formed by the CH reaction with trimethylamine. Overall, the temporal profiles of the products are not consistent with the formation of aminocarbene products in the reaction flow tube. In the case of the reactions with methylamine and dimethylamine, product formation is assigned to an addition-elimination mechanism similar to that proposed for the CH reaction with ammonia. However, this mechanism cannot explain the products detected by the reaction with trimethylamine. A C-H insertion pathway may become more probable as the number of methyl groups increases.
在373 K和4托的多碰撞条件下，研究了次甲基（CH）自由基与氨（NH₃）、甲胺（CH₃NH₂）、二甲胺（(CH₃)₂NH）和三甲胺（(CH₃)₃N）的反应。使用与先进光源（ALS）同步加速器的正交加速飞行时间质谱联用的软光电离来检测反应产物。利用动力学曲线来区分CH反应产物与二级反应或较慢反应的产物。通过将观察到的光电离光谱拟合为纯化合物光谱的线性组合，获得给定质量下由单一反应产生的异构体的分支比。发现CH自由基与氨的反应主要生成亚胺，HN═CH，这与加成-消除机理一致。在CH与甲胺、二甲胺和三甲胺的反应中检测到单甲基取代的亚胺。CH与二甲胺反应生成二甲基亚胺异构体，而CH与三甲胺反应生成三甲基亚胺。总体而言，产物的时间分布与反应流管中氨基卡宾产物的形成不一致。在与甲胺和二甲胺的反应中，产物形成归因于类似于CH与氨反应所提出的加成-消除机理。然而，这种机理无法解释与三甲胺反应检测到的产物。随着甲基数量的增加，C-H插入途径可能变得更有可能。
