The photochemical reaction of trifluoroiodomethane with 1 : l-difluoroethylene yields only the compound CF,CH,*CF,I, i.e. , the trifluoromethyl radical attacks exclusively the :CH, group. Proof of constitution is given. Iodine monobromide and 1 : l-difluoroethylene yield only 1-bromo-1 : 1difluoro-2-iodoethane ; the iodo-compound is converted into 1 : 1 : 1-trifluoro-2-iodoethane by means of mercurous fluoride.THE direction of addition of a trifluoromethyl radical, derived from trifluoroiodomethane , to vinyl chloride and vinyl fluoride was shown t o be exclusively to the :CH, group (Part 11, J., 1953(Part 11, J., , 1199. The present study is concerned with the highly polarised olefin 1 : 1difluoroet hylene.Trifluoroiodomethane and 1 : l-difluoroethylene show no dark reaction, but react smoothly on exposure to light of wave-length >3000 A, with liberation of only traces of iodine, to give exclusively CF,*(C,H,F,)*I. Light of wave-length >2200 A (silica reaction vessels) appreciably increases the rate of formation of CF,*(C,H,FJ*I ; small amounts of products of higher boiling point are also formed. Infra-red spectroscopic examination shows that the two products CF,*(C,H,F,)*I are identical. The product is formed by a chain reaction of the type postulated earlier :CF,I -/ CF,.

Spectra thus designated have been deposited with the Chemical Society (cf. Proc.. 1952, 164). and photocopies may be obtained from the General Secretary. The C.S. number must be cited in such requests.

No abstract

Radical attack on trifluoroethylene is 80% on the CHF group and 20% on the CF, group ; attack by an atom is 60% on the CHF group and 40% on the CF, group. This is the first time that anything other than exclusive radical attack on one carbon of an unsymmetrical olefin has been reported. Polytrifluoroethylene thus contains units such as -CHF*CF,*CHFCF,-, -CHF*CF,*CF,*CHF-, and -CF,*CHFCHF*CF,-; each unit is flanked by itself or by one of the other units, and the last of these units in particular explains why the polymer is thermally less stable than ply-1 : l-Uuoroethylene. Proofs of structure are given for the reaction products from trifluoroiodomethane and trifluoroethylene, and for those from hydrogen bromide and trifluoroethylene. (cis + trans)-l : 2-Difluoroethylene has been prepared. Comments are made on earlier reports on the direction of radical addition to trifluoroethylene.

The product readily liberates iodine on exposure to light, and photochemical chlorination gives a high yield of the dichloride (111) : (11) would have given (IV) by this procedure. Compounds (111) (b. p. 35", n z , O 1-305) and (IV) (b. p. 34-7", ng 1-3029) cannot be distinguished by boiling point or refractive index, but comparison of the infra-red spectrum of (111) with that of a known sample of (IV), prepared from hexafluoropropene and chlorine, readily distinguishes the two isomers.* Further, with zinc and ethanol (IV) readily yields hexafluoropropene, whereas (111) does not (see below).