Addition of free radicals to unsaturated systems. Part XVIII. The direction of radical addition to 1,3,3,3-tetrafluoropropene

Abstract

The photochemical reaction of trifluoroiodomethane with 1,3,3,3-tetrafluoropropene gives the 1 : 1 adducts 1,1,1,2,4,4,4-heptafluoro-3-iodobutane and 1,1,1,3-tetrafluoro-3-iodo-2-trifluoromethylpropane in high yield in the ratio of 75 : 25. The 1,1,1,2,4,4,4-heptafluoro-3-iodobutane is a mixture of the erythro- and threo-forms in the approximate ratio 2 : 1 and treatment of these separately with potassium hydroxide gives, in each case, hexafluorobut-2-yne and trans-1,1,1,2,4,4,4-heptafluorobut-2-ene. Similar treatment of 1,1,1,3-tetrafluoro-3-iodo-2-trifluoromethylpropane gives 1,1,1,3-tetrafluoro-2-trifluoromethylpropene in high yield. Photochemical reaction of 1,3,3,3-tetrafluoropropene with hydrogen bromide gives the adducts 1-bromo-1,3,3,3-tetrafluoropropane and 2-bromo-1,3,3,3-tetrafluoropropane in ratios varying between 42 : 58 and 62 : 38, but appreciable amounts of erythro- and threo-1,2-dibromo-1,3,3,3-tetrafluoropropane are also produced. The dibromides are the major products of the photochemical reaction of bromine with the tetrafluoropropene.