Vicarious nucleophilic substitution
= Vicarious nucleophilic substitution
<Vicarious nucleophilic substitution> replaces aromatic <hydrogen> using a <nucleophile> that carries its own leaving group. In nitroarenes, reversible carbanion addition gives a <sigma-H adduct>; base-induced elimination of the <hydrogen> and the <nucleophile>-borne leaving group, followed by <protonation>, gives substitution without expelling hydride.