Charge-transfer nitration of naphthalene and the methylnaphthalenes. Part 1. Direct comparison with electrophilic aromatic nitrations

The various nitronaphthalenes formed in high yields from the selective photoexcitation of the EDA complexes of the naphthalene and methylnaphthalene donors (ArH) with the N-nitropyridinium and tetranitromethane acceptors are ascribed to charge-transfer nitration, arising as they do from the cation-radiqal pairs [ArH˙+, NO2]. The nitration products from such an electron-transfer pathway are quantitatively compared with those from the electrophilic nitration(thermal), under otherwise the same conditions. The mechanistic implications to electrophilic aromatic substitution are discussed.