The photolysis of 1,2-di-iodotetrafluorobenzene in the presence of benzene and benzene–hexane mixtures gives products derived from the 2-iodotetrafluorophenyl radical and from tetrafluorobenzyne. The aryne product, 5,6,7,8-tetrafluoro-1,4-dihydro-1,4-ethenonaphthalene, is photoisomerised in part to tetrafluorobenzocyclooctene(2).