Mikhailov Victor A, Parkes Michael A, Simpson Matthew J, Tuckett Richard P, Mayhew Chris A
School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK.
J Phys Chem A. 2008 Sep 25;112(38):9012-22. doi: 10.1021/jp804443v. Epub 2008 Aug 28.
Data for the rate coefficients and product cations of the reactions of a large number of atomic and small molecular cations with monochloroethene, trichloroethene, and tetrachloroethene in a selected ion flow tube at 298 K are reported. The recombination energy of the ions range from 6.27 (H3O(+)) through to 21.56 (Ne(+)) eV. Collisional rate coefficients are calculated by modified average dipole orientation theory and compared with experimental values. Thermochemistry and mass balance predict the most feasible neutral products. Together with previously reported results for the three isomers of dichloroethene ( Mikhailov, V. A. ; Parkes, M. A. ; Tuckett, R. P. ; Mayhew, C. A. J. Phys. Chem. A 2006, 110, 5760 ), the fragment ion branching ratios have been compared with those from threshold photoelectron photoion coincidence spectroscopy over the photon energy range of 9-22 eV to determine the importance or otherwise of long-range charge transfer. For ions with recombination energy in excess of the ionization energy of the chloroethene, charge transfer is energetically allowed. The similarity of the branching ratios from the two experiments suggest that long-range charge transfer is dominant. For ions with recombination energy less than the ionization energy, charge transfer is not allowed; chemical reaction can only occur following formation of an ion-molecule complex, where steric effects are more significant. The products that are now formed and their percentage yields are a complex interplay between the number and position of the chlorine atoms with respect to the C=C bond, where inductive and conjugation effects can be important.
报道了在298K下，在选定的离子流动管中，大量原子和小分子阳离子与氯乙烯、三氯乙烯和四氯乙烯反应的速率系数和产物阳离子的数据。离子的重组能范围从6.27（H3O(+)）到21.56（Ne(+)）eV。碰撞速率系数通过改进的平均偶极取向理论计算，并与实验值进行比较。热化学和质量平衡预测了最可行的中性产物。连同先前报道的二氯乙烯三种异构体的结果（米哈伊洛夫，V.A.；帕克斯，M.A.；塔克特，R.P.；梅休，C.A.《物理化学杂志A》2006年，110，5760），在9-22eV的光子能量范围内，将碎片离子分支比与阈值光电子光离子符合光谱法得到的分支比进行了比较，以确定远程电荷转移的重要性。对于重组能超过氯乙烯电离能的离子，电荷转移在能量上是允许的。两个实验的分支比相似，表明远程电荷转移占主导。对于重组能小于电离能的离子，电荷转移是不允许的；化学反应只能在形成离子-分子复合物后发生，此时空间效应更为显著。现在形成的产物及其百分比产率是氯原子相对于C=C键的数量和位置之间复杂相互作用的结果，其中诱导效应和共轭效应可能很重要。
