Azoxybenzene from phenylhydroxylamine and nitrosobenzene

Experiment.—Azoxybenzenefromphenylhydroxylamine and nitrosobenzene.-—Phenylhydroxylamine (1 g.) is added to a solution of 1 g. of nitrosobenzene in 10 c.c. of alcohol. The mixture is shaken while a few drops of concentrated potassium hydroxide solution (1 1) are added, and is then warmed on the water bath for a few minutes. The yellowish-red solution thus formed deposits yellow crystals of the reaction-product when cooled and rubbed with a glass rod. Since azoxybenzene melts at 36°, it has a great tendency to separate from a supersaturated solution in the form of an oil. By recrystallisation from a little alcohol or from petrol ether (retain a few crystals for inoculation) the compound is obtained as a pale yellow or almost colourless solid. 

The feeble colour of azoxybenzene, in contrast to the red of azobenzene, would appear to be more readily intelligible on the basis of the old formula, I, than on that by which Angeli has replaced it, II  

Nevertheless, the existence of asymmetrical azoxybenzenes in two isomeric forms (Angeli), 

The mechanism of the condensation described is plain, and corresponds entirely to the production of nitrones from phenylhydroxylamine and aldehydes (p. 178)  

The relationships of azoxybenzene to azo- and hydrazobenzene are discussed in the explanations given for the next preparation. 

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