Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA.
J Chem Phys. 2010 Aug 21;133(7):074306. doi: 10.1063/1.3473049.
We report a study of chlorine atom reactions with a series of target monounsaturated alkene molecules: 1-pentene, 1-hexene, 2-hexene, and cyclohexene. These reactions were studied using crossed-beam dc slice ion imaging at collision energies of 4 and 7 kcal/mol. Images of the reactively scattered alkenyl radical products were obtained via single photon ionization at 157 nm. The angular distributions at low collision energy are largely isotropic, suggesting the formation of a complex that has a lifetime comparable to or longer than its rotational period, followed by HCl elimination. At high collision energy, the distributions show a sharp forward peak superimposed on the isotropic component accounting for approximately 13% of the product flux. The translational energy distributions peak near zero for the backscattered product, in sharp contrast to the results for alkanes. In the forward direction, the translational energy distributions change dramatically with collision energy. At the high collision energy, a sharp forward peak at approximately 80% of the collision energy appears, quite reminiscent of results of our recent study of Cl+pentane reactions. The scattering distributions for all target molecules are similar, suggesting similarity of the reaction dynamics among these molecules. Ab initio calculations of the energetics and ionization energies for the various product channels were performed at the CBS-QB3 level to aid in interpreting the results.
1-戊烯、1-己烯、2-己烯和环己烯。这些反应在 4 和 7 kcal/mol 的碰撞能下使用交叉束直流片离子成像进行了研究。通过在 157nm 处的单光子电离获得了反应性散射烯基自由基产物的图像。低碰撞能下的角分布基本各向同性，表明形成了一个具有与其旋转周期相当或更长寿命的复合物，随后发生 HCl 消除。在高碰撞能下，分布显示出一个尖锐的前向峰叠加在各向同性分量上，占产物通量的约 13%。后向散射产物的平动能分布在零附近达到峰值，与烷烃的结果形成鲜明对比。在向前方向，平动能分布随碰撞能急剧变化。在高碰撞能下，出现了一个约 80%碰撞能的尖锐前向峰，这与我们最近对 Cl+戊烷反应的研究结果非常相似。所有靶分子的散射分布相似，表明这些分子的反应动力学相似。在 CBS-QB3 水平上进行了各种产物通道的能量学和电离能的从头算计算，以帮助解释结果。
