PHOTOREACTION OF BENZENE WITH HEXAFLUOROBENZENE

Hexafluorobenzene reacts photochemically with benzene to produce mainly 2,3,4,5,6-pentafluorobiphenyl, and with toluene analogously gives a mixture of o-, m-, and p-pentafluorophenyltoluenes. A particularly unusual feature is that naphthalene markedly sensitises these photoreactions in preference to causing the formation of pentafluorophenylnaphthalenes, but not apparently via T 1 naphthalene since heavy-atom solvents strongly inhibit the sensitised processes. In contrast, these solvents promote the unsensitised processes. Although some of the evidence suggests that intermediacy of C 6F5 radicals, the reactions show certain polar characteristics, particularly promotion by polar solvents and proton donors, and are considered to involve a dipolar intermediate formed via attack on ground state benzene by triplet C6F6, functioning as a diradical.