How do aromatic primary amines react with nitrous acid to form diazonium salts?

Aromatic primary amines react with nitrous acid (HNO₂) in the presence of an acid (HX) to form diazonium salts (ArN₂⁺X⁻). This process, known as diazotization, requires the reaction mixture to be kept cool, typically at 0 °C (32 °F), to prevent the loss of nitrogen.1

The general chemical equation for this reaction is:

$$ArN{H}_2+HN{O}_2+HX\to Ar{N}_2^{+}{X}^{-}+2H_{2}O$$

Unlike aliphatic primary amines, which decompose into nitrogen and other products when treated with nitrous acid, aromatic diazonium salts are stable enough to be isolated at low temperatures. These highly reactive compounds are essential in organic synthesis and are particularly significant in the dye industry for the production of azo compounds.123