Recall that primary arylamines, upon diazotization reaction, yield arenediazonium salts. The arenediazonium salts are synthetically useful intermediates. When treated with appropriate reagents, they lose nitrogen, and the diazonium group can be replaced by the –H atom or the –OH group. For instance, to directly install a –OH group on an aromatic ring, aromatic amines are first treated with sodium nitrite and sulfuric acid to generate an arenediazonium salt, which, upon warming, then undergoes hydrolysis to yield phenols. Similarly, the conversion of aniline to substituted benzene is a classic example of using the directive effects of the –NH2 group. For example, direct halogenation of benzene to synthesize 1,3,5-tribromobenzene is not possible because halogens are o-, p- directors. In such cases, aniline is used to exploit the –NH2 group’s activating and o-, p-directing effects. Once halogenated, the –NH2 group is removed via diazotization, followed by a reaction with H3PO2.