Decomposition of o-nitrophenylazide

Benzofurazan oxide has been prepared by a thermal decomposition of o-nitrophenylazide 4-8 by oxidation of the dioxime of o-benzoquinone by dilute nitric acid or potassium ferricyanide in alkaline solution 4 and by oxidation of o-nitroaniline with sodium hypochlorite.9 The present synthesis is a modification of the methods of Noelting and Kohn 8 and of Zincke and Schwarz.4... 

The thermolysis of methylazide was studied first by Ramsperger 21a> who found it to be a homogenous first-order reaction. Studies of thermolyses of several other organic azides in various solvents and at different concentrations also show first-order kinetics 22-28). This led to the conclusion that free nitrene intermediates are involved. There are however thermal decompositions of azides where nitrene intermediates are not involved. For example ortho-substituted arylazides like o-nitrophenylazide 2, undergo formation of benzofurazan 3 by a concerted mechanism according to l.c.21b). 

Let us now consider, a specific case in detail where spectrophotometry has-been used for rate studies. Fagley et aV have studied the thermal decomposition of ort/to-nitrophenylazide to benzofuraxan and nitrogen. o-Nitro-phenylazide exhibits two absorption maxima at 240 mp and 320 mp and a prominent shoulder at 2S5 mp, in cyclohexanol. Benzofuraxan shows only... 

---