Homolytic aromatic substitution

Abstract

THE experimental facts and their theoretical interpretation for aromatic substitution by heterolytic mechanisms, including both electrophilic and nucleophilic reagents, are. now well established. Although the possibility of homolytic aromatic substitution was recognized sixteen years ago1, the absence of reliable quantitative data has hitherto made any comprehensive theoretical interpretation both difficult and speculative. Examples of homolytic aromatic substitution have in recent years been considerably extended and now include as substituting agents aryl radicals (from certain diazo compounds or acyl peroxides2), methyl radicals (from acetyl peroxide3, lead tetra-acetate4, phenyliodosoacetate5 or the electrolysis of acetates4), halogen atoms (in non-catalytic high-temperature halogenation6) and hydroxyl radicals (from Fenton's reagent7, the action of ionizing radiations on aqueous solutions8, or the irradiation of aqueous solutions of ion pair complexes9). © 1951 Nature Publishing Group.