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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Potential Energy Surface and Product Branching Ratios for the Reaction of Dicarbon,C_2(X~1SIGMA_g~+),with Methylacetylene,CH_3CCH(X~1A_1):An Ab Initio/RRKM Study
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Potential Energy Surface and Product Branching Ratios for the Reaction of Dicarbon,C_2(X~1SIGMA_g~+),with Methylacetylene,CH_3CCH(X~1A_1):An Ab Initio/RRKM Study

机译：二碳C_2（X〜1SIGMA_g〜+）与甲基乙炔，CH_3CCH（X〜1A_1）反应的势能面和产物支化比：从头算/ RRKM研究

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Ab initio calculations of the potential energy surface for the C_2(X~1SIGMA_g~+)+ CH_3CCH(X~1A_1)reaction have been carried at the G2M level of theory.The calculations show that the dicarbon molecule in the ground singlet electronic state can add to methylacetylene without a barrier producing a three-member or a four-member ring intermediate,which can rapidly rearrange to the most stable H_3CCCCCH isomer on the C_5H_4 singlet surface.This isomer can then lose a hydrogen atom(H)or molecular hydrogen(H_2)from the CH_3 group with the formation of H_2CCCCCH and HCCCCCH,respectively.Alternatively,H atom migrations and three-member-ring closure/opening rearrangements followed by H and H_2 losses can lead to other isomers of the C_5H_3 and C_5H_2 species.According to the calculated energetics,the C_2(X~1SIGMA_g~+)+ CH_3CCH reaction is likely to be a major source of the C_5H_3 radicals(in particular,the most stable H_2CCCCCH and HCCCHCCH isomers,which are relevant to the formation of benzene through the reactions with CH_3).Among heavy-fragment product channels,only C_3H_3,+ C_2H and c-C_3H_2 + C_2H_2 might compete with C_5H_3 + H and C_5H_2 + H_2.RRKM calculations of reaction rate constants and product branching ratios depending on the reactive collision energy showed that the major reaction products are expected to be H_2CCCCCH + H(64-66%)and HCCCHCCH + H(34-30%),with minor contributions from HCCCCCH + H_2(1-2%),HCCCHCC + H_2(up to 1%),C_3H_3 + C_2H(up to 1%),and c-C_3H_2 + C_2H_2(up to 0.1%)if the energy randomization is complete.The calculations also indicate that the C_2(X~1SIGMA_g~+)+ CH_3CCH(X~1A_1)reaction can proceed by direct H-abstraction of a methyl hydrogen to form C_3H_3 + C_2H almost without a barrier.
机译：C_2（X〜1SIGMA_g〜+）+ CH_3CCH（X〜1A_1）反应的势能面从头算进行了计算，从理论上计算表明，基态单重态电子态的二碳分子可以无障碍地添加到甲基乙炔中，生成三元或四元环中间体，该中间体可以快速重排至C_5H_4单重态表面上最稳定的H_3CCCCCH异构体，然后该异构体会失去氢原子（H）或分子氢（ H_2）分别来自CH_3基团并形成H_2CCCCCH和HCCCCCH。或者，H原子迁移和三元环闭环/开环重排以及随后的H和H_2丢失会导致C_5H_3和C_5H_2物种的其他异构体。对于计算出的能量，C_2（X〜1SIGMA_g〜+）+ CH_3CCH反应可能是C_5H_3自由基的主要来源（特别是最稳定的H_2CCCCCH和HCCCHCCH异构体，它们与苯的生成有关通过CH_3反应）。在重片段产物通道中，只有C_3H_3，+ C_2H和c-C_3H_2 + C_2H_2可能与C_5H_3 + H和C_5H_2 + H_2竞争.RRKM根据反应性计算反应速率常数和产物支化比碰撞能量表明，主要反应产物预计为H_2CCCCCH + H（64-66％）和HCCCHCCH + H（34-30％），其中HCCCCCH + H_2（1-2％），HCCCHCC + H_2（如果能量随机化完成，则C_3H_3 + C_2H（最高1％）和c-C_3H_2 + C_2H_2（最高0.1％）。计算还表明C_2（X〜1SIGMA_g〜+）+ CH_3CCH（X〜1A_1）反应可以通过直接H吸收甲基氢来进行，形成C_3H_3 + C_2H几乎没有任何障碍。

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