Perfluoroalkyl derivatives of sulphur. Part XVII. Some reactions of perfluorovinylsulphur pentafluoride, and a re-examination of the thermal reaction between perfluoropropene and buta-1,3-diene

Abstract

Perfluorovinylsulphur pentafluoride is attacked by sodium methoxide in methanol to give 1,2,2-trifluoro-2-methoxyethylsulphur pentafluoride, and by bromine (→ SF₅·CFBr·CF₂Br), hydrogen bromide (→ SF₅·CHF·CF₂Br), and trifluoroiodomethane (→ SF₅·CFl·C₂F₅) under photochemical conditions and bromine monochloride (→ SF₅·CFCl·CF₂Br, SF₅·CFBr·CF₂Cl) under thermal conditions to yield the corresponding 1 : 1 adducts and by-products derived from C–S bond fission. Hexafluoro-1,1-di-iodopropane, a by-product of the reaction between the olefin and trifluoroiodomethane, yields perfluorohex-3-ene when irradiated in the presence of mercury, and cleavage of the dibromide SF₅·CFBr·CF₂Br with aluminium bromide gives 1,2-dibromotetrafluoroethane. Reaction of perfluorovinylsulphur pentafluoride with butadiene at 140–195 °C yields essentially a 1 : 1 mixture of cis- and trans-1,1,2-trifluoro-2-pentafluorothio-3-vinylcyclobutane; re-examination of the corresponding reaction involving perfluoropropene has shown that the major product is a mixture of cis- and trans-1,1,2-trifluoro-2-trifluoro-methyl-3-vinylcyclobutane, 4,4,5-trifluoro-5-(trifluoromethyl) cyclohexene being formed in only small amounts. Details of the preparation of copoly(perfluorovinylsulphur pentafluoride–vinylidene fluoride) and n.m.r. data for the cycloadducts named above are presented.