He Chao, Zhao Long, Doddipatla Srinivas, Thomas Aaron M, Nikolayev Anatoliy A, Galimova Galiya R, Azyazov Valeriy N, Mebel Alexander M, Kaiser Ralf I
Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii, 96822, USA.
Samara National Research University, Samara, 443086, Russian Federation.
Chemphyschem. 2020 Jun 16;21(12):1295-1309. doi: 10.1002/cphc.202000183. Epub 2020 May 25.
The crossed molecular beam reactions of the methylidyne radical (CH; X Π) with 1,3-butadiene (CH CHCHCH ; X A ) along with their (partially) deuterated counterparts were performed at collision energies of 20.8 kJ mol under single collision conditions. Combining our laboratory data with ab initio calculations, we reveal that the methylidyne radical may add barrierlessly to the terminal carbon atom and/or carbon-carbon double bond of 1,3-butadiene, leading to doublet C H intermediates with life times longer than the rotation periods. These collision complexes undergo non-statistical unimolecular decomposition through hydrogen atom emission yielding the cyclic cis- and trans-3-vinyl-cyclopropene products with reaction exoergicities of 119±42 kJ mol . Since this reaction is barrierless, exoergic, and all transition states are located below the energy of the separated reactants, these cyclic C H products are predicted to be accessed even in low-temperature environments, such as in hydrocarbon-rich atmospheres of planets and cold molecular clouds such as TMC-1.
在单次碰撞条件下，于20.8 kJ·mol的碰撞能量下进行了次甲基自由基（CH；X Π）与1,3 - 丁二烯（CH₂CHCHCH₂；X A₁）及其（部分）氘代类似物的交叉分子束反应。将我们的实验数据与从头算计算相结合，我们发现次甲基自由基可以无障碍地加成到1,3 - 丁二烯的末端碳原子和/或碳 - 碳双键上，生成寿命长于旋转周期的双重态C₅H₅中间体。这些碰撞复合物通过氢原子发射进行非统计单分子分解，生成反应放热能为119±42 kJ·mol的环状顺式和反式 - 3 - 乙烯基 - 环丙烯产物。由于该反应无势垒、放能且所有过渡态都位于分离反应物的能量之下，预计即使在低温环境中，如在富含碳氢化合物的行星大气和诸如TMC - 1的冷分子云中，也能生成这些环状C₅H₅产物。
