Oxyazo-compounds

OXYAZO COMPOUNDS. Compounds of the type RN=NC6H4OH, containing both the azo group — N=N—, and a hydroxyl group —OH, both attached to carbon atoms in the same ring. These compounds are commonly produced by ihe action of diazo compounds upon phenols in alkaline solution. They constitute a class of dyes. See Dyes. 

Oxyazo-compounds are also obtained by action of diazo-com-pounds on the isomeric cresols [39, 41, 42]. 

That a close relationship exists between azo-compounds and hydrazides is seen from the fact that certain oxyazo-compounds obtained from diazo-compounds and phenols are identical with the hydrazides of certain quinones. Indeed all coloured hydrazides show a great similarity to the azo-compounds, and probably belong to this class. Both classes of compounds, for example, behave similarly on reduction. The hydrazine group, like the azo-group, is split, yielding two amido-groups, one of which remains in combination with the phenyl group, the other with the carbon atom. 

The azo group enters the position para to hydroxyl and if this is occupied an ortho compound is formed. The directing influence of the hydroxyl group is, thus, the same as toward atoms or simple groups. p-Hydroxyazobenzene (also called oxyazo-benzene) crystallizes in orange-colored prisms which melt at 150°. Hydroxyazo compounds are valuable dyes. 

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