7.4.2 Indicators

Azo-compounds that contain both an acidic and a basic group can be utilized as indicators since the colours of the conjugate acid and the conjugate base are different. Examples are methyl orange and methyl red which are prepared by coupling of dimethylaniline with diazotized sulfanilic acid and diazotized anthranilic acid, respectively.

7.4.3 Synthesis of Amines

Azo-compounds are susceptible to hydrogenolysis to give amines. For example, the coupling of 1-naphthol with benzenediazonium chloride gives azo-compound which could be reduced to 4-amino-1-naphthol in the presence of dithionite.

7.4.4 Synthesis of Quinones

The ortho and para diamines and aminophenols readily oxidize to give quinones. Both classes compounds can be readily prepared by diazo-coupling followed by reduction.