From the primary amines are derived the diazo compounds and azo compounds; closely related are the hydrazines (q.v.).
The acid finds considerable use in organic chemistry, being employed to discriminate between the different types of alcohols and of amines, and also in the production of diazo, azo and diazo-amino compounds.
The diazo group takes up the para position with regard to the hydroxyl group, and if this be prevented it then goes into the ortho position.
The constitution of the isomeric diazo hydroxides has given rise to much discussion.
According to Hantzsch the isomeric diazo hydroxides are structurally identical, and the differences in behaviour are due to stereo-chemica l relations, the isomerism being comparable with that of the oximes.