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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Dissociation Channels of the 1-Buten-2-yl Radical and Its Photolytic Precursor 2-Bromo-1-butene
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Dissociation Channels of the 1-Buten-2-yl Radical and Its Photolytic Precursor 2-Bromo-1-butene

机译：1-丁-2-基自由基及其光解前体2-溴-1-丁烯的解离通道

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摘要

The work presented here is the first in a series of studies that use a molecular beam scattering technique to investigate the unimolecular reaction dynamics of C_4H_7 radical isomers.Photodissociation of the halogenated precursor 2-bromo-l-butene at 193 nm under collisionless conditions produced l-buten-2-yl radicals with a range of internal energies spanning the predicted barriers to the unimolecular reaction channels of the radical.Resolving the velocities of the stable C_4H_7 radicals,as well as those of the products,allows for the identification of the energetic onset of each dissociation channel.The data show that radicals with at least 30.7+-2 kcal/mol of internal energy underwent C-C fission to form allene+methyl,and radicals with at least 36.7+-4 kcal/mol of internal energy underwent C-H fission to form H+1-butyne and H+1,2-butadiene;both of these observed barriers agree well with the G3//B3LYP calculations of Miller.HBr elimination from the parent molecule was observed,producing vibrationally excited 1-butyne and 1,2-butadiene.In the subsequent dissociation of these C_4H_6 isomers,the major channel was C-C fission to form propargyl+methyl,and there is also evidence of at least one of the possible H+C_4H_5 channels.A minor C-Br fission channel produces l-buten-2-yl radicals in an excited electronic state and with low kinetic energy;these radicals exhibit markedly different dissociation dynamics than do the radicals produced in their ground electronic state.
机译：本文介绍的工作是使用分子束散射技术研究C_4H_7自由基异构体的单分子反应动力学的一系列研究中的第一项。卤代前体2-溴-1-丁烯在193 nm下在无碰撞条件下的光解离产生了-丁烯-2-基自由基，其内部能量范围跨越该自由基的单分子反应通道的预测障碍。解析稳定的C_4H_7自由基以及其产物的速度，即可鉴定出高能数据显示内部能量至少为30.7 + -2 kcal / mol的自由基经历CC裂变形成烯丙基+甲基，内部能量至少36.7 + -4 kcal / mol的自由基经历CH裂变裂变形成H + 1-丁炔和H + 1,2-丁二烯;这两个观察到的势垒都与Miller的G3 // B3LYP计算结果非常吻合。观察到母体分子中HBr的消除，振动激发的1-丁炔和1,2-丁二烯。在这些C_4H_6异构体的后续解离中，主要通道是CC裂变形成炔丙基+甲基，并且也有证据表明至少有一种可能的H + C_4H_5通道较小的C-Br裂变通道会产生处于激发电子态且动能较低的l-buten-2-yl自由基;这些自由基的离解动力学与在其基态电子态产生的自由基明显不同。

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