Mikhailov Victor A, Parkes Michael A, Tuckett Richard P, Mayhew Chris A
School of Physics and Astronomy, and School of Chemistry, University of Birmingham, Edgbaston, UK.
J Phys Chem A. 2006 May 4;110(17):5760-71. doi: 10.1021/jp060093s.
A study of the reactions of a series of gas-phase cations (NH(4)(+), H(3)O(+), SF(3)(+), CF(3)(+), CF(+), SF(5)(+), SF(2)(+), SF(+), CF(2)(+), SF(4)(+), O(2)(+), Xe(+), N(2)O(+), CO(2)(+), Kr(+), CO(+), N(+), N(2)(+), Ar(+), F(+), and Ne(+)) with the three structural isomers of dichloroethene, i.e., 1,1-C(2)H(2)Cl(2), cis-1,2-C(2)H(2)Cl(2), and trans-1,2-C(2)H(2)Cl(2) is reported. The recombination energy (RE) of these ions spans the range of 4.7-21.6 eV. Reaction rate coefficients and product branching ratios have been measured at 298 K in a selected ion flow tube (SIFT). Collisional rate coefficients are calculated by modified average dipole orientation (MADO) theory and compared with experimental data. Thermochemistry and mass balance have been used to predict the most feasible neutral products. Threshold photoelectron-photoion coincidence spectra have also been obtained for the three isomers of C(2)H(2)Cl(2) with photon energies in the range of 10-23 eV. The fragment ion branching ratios have been compared with those of the flow tube study to determine the importance of long-range charge transfer. A strong influence of the isomeric structure of dichloroethene on the products of ion-molecule reactions has been observed for H(3)O(+), CF(3)(+), and CF(+). For 1,1-C(2)H(2)Cl(2) the reaction with H(3)O(+) proceeds at the collisional rate with the only ionic product being 1,1-C(2)H(2)Cl(2)H(+). However, the same reaction yields two more ionic products in the case of cis-1,2- and trans-1,2-C(2)H(2)Cl(2), but only proceeds with 14% and 18% efficiency, respectively. The CF(3)(+) reaction proceeds with 56-80% efficiency, the only ionic product for 1,1-C(2)H(2)Cl(2) being C(2)H(2)Cl(+) formed via Cl(-) abstraction, whereas the only ionic product for both 1,2-isomers is CHCl(2)(+) corresponding to a breaking of the C=C double bond. Less profound isomeric effects, but still resulting in different products for 1,1- and 1,2-C(2)H(2)Cl(2) isomers, have been found in the reactions of SF(+), CO(2)(+), CO(+), N(2)(+), and Ar(+). Although these five ions have REs above the ionization energy (IE) of any of the C(2)H(2)Cl(2) isomers, and hence the threshold for long-range charge transfer, the results suggest that the formation of a collision complex at short range between these ions and C(2)H(2)Cl(2) is responsible for the observed effects.
报道了一系列气相阳离子（NH₄⁺、H₃O⁺、SF₃⁺、CF₃⁺、CF⁺、SF₅⁺、SF₂⁺、SF⁺、CF₂⁺、SF₄⁺、O₂⁺、Xe⁺、N₂O⁺、CO₂⁺、Kr⁺、CO⁺、N⁺、N₂⁺、Ar⁺、F⁺和Ne⁺）与二氯乙烯的三种结构异构体，即1,1-C₂H₂Cl₂、顺式-1,2-C₂H₂Cl₂和反式-1,2-C₂H₂Cl₂的反应。这些离子的重组能（RE）范围为4.7 - 21.6 eV。在选定离子流管（SIFT）中于298 K测量了反应速率系数和产物分支比。通过修正平均偶极取向（MADO）理论计算了碰撞速率系数并与实验数据进行比较。利用热化学和质量平衡来预测最可行的中性产物。还获得了光子能量在10 - 23 eV范围内的C₂H₂Cl₂三种异构体的阈值光电子 - 光离子符合光谱。将碎片离子分支比与流管研究的结果进行比较以确定远程电荷转移的重要性。对于H₃O⁺、CF₃⁺和CF⁺，已观察到二氯乙烯的异构结构对离子 - 分子反应产物有强烈影响。对于1,1-C₂H₂Cl₂，与H₃O⁺的反应以碰撞速率进行，唯一的离子产物是1,1-C₂H₂Cl₂H⁺。然而，在顺式-1,2-和反式-1,2-C₂H₂Cl₂的情况下，相同反应产生另外两种离子产物，但效率分别仅为14%和18%。CF₃⁺反应的效率为56 - 80%，1,1-C₂H₂Cl₂的唯一离子产物是通过Cl⁻夺取形成的C₂H₂Cl⁺，而两种1,2-异构体的唯一离子产物是对应于C = C双键断裂的CHCl₂⁺。在SF⁺、CO₂⁺、CO⁺、N₂⁺和Ar⁺的反应中发现了不太显著的异构效应，但对于1,1-和1,2-C₂H₂Cl₂异构体仍产生不同产物。尽管这五种离子的重组能高于任何一种C₂H₂Cl₂异构体的电离能（IE），因此高于远程电荷转移的阈值，但结果表明这些离子与C₂H₂Cl₂在短程形成碰撞复合物是观察到这些效应的原因。
