Photoreaction of benzene with hexafluorobenzene

Abstract

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 pentatluorophenylnaphthalenes, but not apparently via T₁ 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 C₆F₅ radicals, the reactions show certain polar characteristics, particularly promotion by polar solvents and proton donors, and are considered to involve a dlipolar intermediate formed via attack on ground state benzene by triplet C₆F₆ functioning as a diradical.