Radiolytic displacement of substituent groups in benzene by hydrogen (tritium)

Abstract

The experimental work examines the extent to which β-radiation-induced hydrogen exchange of aromatic substrates in aqueous solution with the solvent is accompanied by displacement of a substituent group in the aromatic compound. Radiation-induced substituent displacement is observed to any significant extent only for the halogenobenzenes (Phl > PhBr > PhCl). A dual function is ascribed to copper(II) ions, which act as inhibitor of both exchange and substituent displacement: they act as oxidising agent towards hydrogen atoms and substituted cyclohexadienyl radicals with attendant formation of the corresponding cations. This model explains why, in the case of bromobenzene, copper(II) ions inhibit the substituent displacement reaction more than the tritium exchange.