Diazotization

the reaction of preparing diazo compounds by the action of nitrous acid (or its derivatives) on primary amines in the presence of inorganic acids (HCl, H₂SO₄, or HNO₃) at 0°-5°C. The diazotization of aromatic amines to yield diazonium salts is the most common—for example, aniline is diazotized to phenyldiazonium chloride:

In organic synthesis, diazotization is used extensively to make various aromatic compounds through the diazonium salt, as well as to synthesize dyes, particularly azo dyes.