Hydrolysis of Diaryliodonium Salts

Nucleophilic substitution by S_Nl -type mechanisms is familiar in aliphatic compounds but is uncommon with aromatic compounds because of the general difficulty of generating vinyl cations. There is only one class of aromatic compounds for which an S_Nl-mechanism has been well established, namely diazonium salts. The evidence is persuasive that diazonium salts decompose in aqueous solution to form first an aryl cation which subsequently reacts rapidly with available nucleophiles (e.g. water or halide ions) to form the reaction products.