Photochemistry of 3- and 4-Nitrophenyl Azides: Detection and Characterization of Reactive Intermediates

Article abstract of DOI:10.1021/ja00259a032

Irradiation of nitro-substituted aromatic azides initiates a complex series of chemical reactions that lead to different products depending on the details of the experiment.There is evidence that four reactive intermediates participate in product-determining reactions.These are the singlet nitrene, the triplet nitrene, the triplet azide, and the ring-expanded dehydroazepine.The chemical and physical properties of each of these species is modified by the nitro substituent.The reactivity of the singlet nitrene with nucleophilic amines is increased, the lifetime of the dehydroazepine is shortened, and the triplet nitrene becomes a powerful single-electron acceptor.Nitro-substituted aromatic azides are widely used in photolabeling experiments.The findings of this study suggest that they may be inappropriate choices as photolabeling agents in many circumstances.