Photolysis of 4-azidodiphenyl in solution studied by UV absorption spectroscopy

4-Azidodiphenyl was photolysed with low intensity radiation in oxygen-free and oxygen containing dichloromethane solutions. It was found that the main product is azodiphenyl when the concentration is greater than about 10−2 mol/l and oxygen is absent. In the case of oxygen containing diluted azide solutions, the triplet azide molecules are trapped by oxygen to form, probably, a nitroazodiphenyl intermediate. In both cases, the light-induced decomposition of azide can be treated approximately as a unidirectional first order (UFO) reaction, where the reactant is the only light absorbent. The deviation from such kinetics appearing at high azide conversions is mainly caused by the nitrene—solvent reaction. The concentration of unreacted azide was measured by the absorbance at 276 nm.