Addition of free radicals to unsaturated systems. Part XXII. Photochemical addition of trifluoroiodomethane and iodine to perfluoro-(3-methylbut-1-ene) and photochemical dimerisation of the olefin

Abstract

Photochemical reaction of trifluoroiodomethane with the title olefin gives the 1:1 adduct (CF₃)₂CF·CFI·CF₂·CF₃ in low yield (22%), the perfluoroalkane (CF₃)₂CF·CF(CF₃)·C₂F₅, the iodo-compounds (CF₃)₂C:CF·CF₂I (VII), (CF₃)₂CF·Cl:CF₂(VIII), and (CF₃)₂CF·CFI·CF₃(IX), formed via the iodine adduct (CF₃)₂CF·CFI·CF₂I, and the unsaturated compounds (CF₃)₂C:CF·CF₂·CF₂·CF:C(CF₃)₂(IV), (CF₃)₂C:CF·CF₂·CF(CF₃)·CF(CF₃)₂(V), and (CF₃)₂C:CF·CF₂·CF(C₂F₅)·CF(CF₃)₂(VI), which are considered to arise by combination reactions involving the allyl radical (CF₃)₂C:CF·CF₂. Under comparable conditions the reaction of iodine with the olefin yields the iodo-compounds (VII), (VIII), and (IX), the alkene (V), and the diene (IV). Irradiation of the olefin alone affords mainly the dimers (V) and (CF₃)₂CF·CF(CF₃)·C[CF(CF₃)₂]:CF₂, together with small amounts of the dimer (CF₃)₂CF·CF₂·CF₂·C[CF(CF₃)₂]:CF₂ and the diene (IV); dimer formation probably involves rearrangement of intermediate dimer diradicals.