作者:Akito Sasaki、Loïc Mahé、Akira Izuoka、Tadashi Sugawara
DOI:10.1246/bcsj.71.1259
日期:1998.6
UV photolysis of powdered crystals of several aryl azides at cryogenic temperatures afforded azo compounds predominantly. In the cases of p-(N-methylacetamido)phenyl azide and 2-azidobiphenyl, a CH insertion product or a carbazole was formed, competing with azo formation. These products can be considered to be formed through topotactic processes when the crystal structures are taken into account. The arylnitrenes generated in the azide crystals were monitored by ESR spectroscopy; they turned out to have extremely long half life-times, compared with those in the gas phase or in solution. Such high kinetic stabilities are ascribed to the inert environment around the generated nitrenes. The decay process of arylnitrenes in the initial stage obeyed a pseudo-first order kinetics; activation parameters were evaluated by Arrhenius plots. The activation enthalpies and entropies indicate that the diffusional processes of arylnitrenes may be the vital factors determining the kinetic stability and the product distribution in the crystalline environment.
在低温下对几种芳基叠氮化物粉末晶体进行UV光解反应,主要得到了偶氮化合物。在p-(N-甲基乙酰氨基)苯基叠氮化物和2-叠氮联苯的情况下,形成了CH插入产物或咔唑,这与偶氮化合物的形成竞争。考虑到晶体结构,这些产物可以认为是通过拓扑过程形成的。在叠氮晶体中生成的芳香氮烯通过电子自旋共振(ESR)光谱进行了监测;与气相或溶液中的相比,它们的半衰期非常长。这种高的动力学稳定性归因于生成的氮烯周围的惰性环境。芳香氮烯在初始阶段的衰减过程遵循伪一阶动力学;通过阿伦尼乌斯图评估了激活参数。激活焓和熵表明,芳香氮烯的扩散过程可能是决定结晶环境中动力学稳定性和产物分布的重要因素。