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首页> 外文期刊>The Journal of Chemical Physics >Investigation of the O+allyl addition/elimination reaction pathways from the OCH2CHCH2 radical intermediate
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Investigation of the O+allyl addition/elimination reaction pathways from the OCH2CHCH2 radical intermediate

机译：OCH2CHCH2自由基中间体对O +烯丙基加成/消除反应途径的研究

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These experiments study the preparation of and product channels resulting from OCH2CHCH2, a key radical intermediate in the O+allyl bimolecular reaction. The data include velocity map imaging and molecular beam scattering results to probe the photolytic generation of the radical intermediate and the subsequent pathways by which the radicals access the energetically allowed product channels of the bimolecular reaction. The photodissociation of epichlorohydrin at 193.3 nm produces chlorine atoms and c-OCH2CHCH2 radicals; these undergo a facile ring opening to the OCH2CHCH2 radical intermediate. State-selective resonance-enhanced multiphoton ionization (REMPI) detection resolves the velocity distributions of ground and spin-orbit excited state chlorine independently, allowing for a more accurate determination of the internal energy distribution of the nascent radicals. We obtain good agreement detecting the velocity distributions of the Cl atoms with REMPI, vacuum ultraviolet (VUV) photoionization at 13.8 eV, and electron bombardment ionization; all show a bimodal distribution of recoil kinetic energies. The dominant high recoil kinetic energy feature peaks near 33 kcal/mol. To elucidate the product channels resulting from the OCH2CHCH2 radical intermediate, the crossed laser-molecular beam experiment uses VUV photoionization and detects the velocity distribution of the possible products. The data identify the three dominant product channels as C3H4O (acrolein) + H, C2H4+ HCO (formyl radical), and H2CO (formaldehyde)+ C2H3. A small signal from C2H2O (ketene) product is also detected. The measured velocity distributions and relative signal intensities at m/e= 27, 28, and 29 at two photoionization energies show that the most exothermic product channel, C2H5+CO, does not contribute significantly to the product branching. The higher internal energy onset of the acrolein+H product channel is consistent with the relative barriers en route to each of these product channels calculated at the CCSD(T)/aug-cc-pVQZ level of theory, although a clean determination of the barrier energy to H+acrolein is precluded by the substantial partitioning into rotational energy during the photolytic production of the nascent radicals. We compare the measured branching fraction to the H+acrolein product channel with a statistical prediction based on the calculated transition states. (c) 2008 American Institute of Physics.
机译：这些实验研究了OCH2CHCH2（O +烯丙基双分子反应中的关键自由基中间体）的制备和产物通道。数据包括速度图成像和分子束散射结果，以探测自由基中间体的光解生成以及自由基进入双分子反应的能量允许产物通道的后续途径。表氯醇在193.3 nm处发生光离解，产生氯原子和c-OCH2CHCH2自由基;它们经历了向OCH2CHCH2自由基中间体的容易的开环。状态选择共振增强多光子电离（REMPI）检测可独立解析基态和自旋轨道激发态氯的速度分布，从而可以更准确地确定新生自由基的内部能量分布。我们通过REMPI，13.8 eV真空紫外（VUV）光电离和电子轰击电离检测Cl原子的速度分布获得了良好的一致性。都显示出反冲动能的双峰分布。高反冲动能占主导地位的峰值在33 kcal / mol附近。为了阐明OCH2CHCH2自由基中间体产生的产物通道，交叉激光分子束实验使用VUV光电离并检测可能产物的速度分布。数据确定了三个主要产物通道，分别为C3H4O（丙烯醛）+ H，C2H4 + HCO（甲酰基）和H2CO（甲醛）+ C2H3。还检测到来自C2H2O（乙烯酮）产物的小信号。在两个光电离能下，在m / e = 27、28和29时测得的速度分布和相对信号强度表明，最放热的产物通道C2H5 + CO对产物分支的贡献不大。丙烯醛+ H产物通道较高的内能起始与在理论上以CCSD（T）/ aug-cc-pVQZ水平计算的通往这些产物通道的相对壁垒一致，尽管该壁垒的确定是明确的在新生自由基的光解过程中，由于大量分配为旋转能而排除了H +丙烯醛的能量。我们将测得的分支分数与H +丙烯醛产物通道进行比较，并基于计算的过渡态进行统计预测。 （c）2008年美国物理研究所。

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