Department of Chemistry-Ångström Laboratory, Uppsala University, P.O. Box 462, SE-751 20 Uppsala, Sweden.
Universitá di Perugia, Dipartimento di Chimica, Biologia e Biotecnologie, 06123 Perugia, Italy.
J Chem Phys. 2018 Apr 7;148(13):134307. doi: 10.1063/1.5005595.
The photochemistry of halomethanes is fascinating for the complex cascade reactions toward either the parent or newly synthesized molecules. Here, we address the structural rearrangement of photodissociated CHIBr in methanol and cyclohexane, probed by time-resolved X-ray scattering in liquid solution. Upon selective laser cleavage of the C-I bond, we follow the reaction cascade of the two geminate geometrical isomers, CHI-Br and CHBr-I. Both meta-stable isomers decay on different time scales, mediated by solvent interaction, toward the original parent molecule. We observe the internal rearrangement of CHBr-I to CHI-Br in cyclohexane by extending the time window up to 3 μs. We track the photoproduct kinetics of CHBr-I in methanol solution where only one isomer is observed. The effect of the polarity of solvent on the geminate recombination pathways is discussed.
卤代甲烷的光化学非常有趣，因为它会发生复杂的级联反应，生成母体或新合成的分子。在这里，我们通过在液态溶液中进行时间分辨 X 射线散射来研究光解 CHIBr 在甲醇和环己烷中的结构重排。通过选择性激光断裂 C-I 键，我们跟踪两个偕二甲基几何异构体 CHI-Br 和 CHBr-I 的反应级联。两种亚稳异构体通过溶剂相互作用以不同的时间尺度向原始母体分子衰变。我们通过将时间窗口延长至 3 μs，在环己烷中观察到 CHBr-I 向 CHI-Br 的内部重排。我们在甲醇溶液中跟踪 CHBr-I 的光产物动力学，其中仅观察到一种异构体。讨论了溶剂极性对偕二聚体复合途径的影响。
