JUSE,
1964
ADDITION OF FLUORINE TO HALOGENATED OLEFINS
1591
The Addition of Fluorine to Halogenated Olefins] EUGENE R. BISSELLAND DOUGLAS B. FIELDS Lawrence Radiation Laboratory, University of California, Livermore, California November 2'9, 196s The use of a mixture of lead dioxide and sulfur tetrafluoride as a reagent for the selective addition of fluorine to the double bond of halogenated olefins has been studied. This reagent generally affords higher yields under somewhat milder conditions than have been reported previously. Iodine-containing olefins have been fluorinated for the first time. Four new halocarbons, namely l,l-dichloro-1,2-difluoroethane,dl-l,2-dichloro-l,2and l-bromo-l,2-difluoroethane, have been synthesized and difluoroethane, meso-1,2-dichloro-l,2-difluoroethane, characterized.
iodine, with a mixture of lead dioxide and sulfur tetraThe selective addition of fluorine to the double bond fluoride are summarized in Table I. In most cases the of a halogen-containing olefin was first reported by yields were significantly higher than those from any of Henne and Waalkes2 in 1945. They employed lead the previously reported methods. The advantage of tetrafluoride general in situ from lead dioxide and hydrothe sulfur tetrafluoride method particularly was progen fluoride. Seven examples were cited with yields nounced in the case of reactive olefins and those conranging from 17-59%. Antimony pentafl~oride,~ cobalt taining iodine. Since the examples cited in Table I trifluoride generated in situ from cobaltic oxide and hydrogen fluoride14 preformed cobaltic f l u ~ r i d e , ~ - ~were all run under the same reaction conditions, the yield and conversion data provide an estimation of the mercuric fluoride generated in situ from mercuric oxide relative reactivity of the various olefins. and hydrogen fluoride,g chlorine trifluoride, preformed No effort vas made to maximize the yield from each manganese trifluoride,68 preformed silver difluoride18 olefin, but the reaction was studied in some detail with and preformed ceric fluoride8 all have been used for trichloroethylene. Optimum reaction temperature fluorination of double bonds. In general these methods ranged from about 40-100° with reaction times of 2-8 have not found widespread synthetic application even hr. Increasing the reaction temperature above about though the yields in some cases were quite good. 120' resulted in extensive side reactions including reThe procedures involving the in situ formation of lead placement of chlorine and carbon-carbon bond scission. tetrafluoride, cobalt trifluoride, or mercuric fluoride The optimum ratio of lead dioxide to trichlorethylen$ from the oxides and hydrogen fluoride require handling was about 1: 1.5. The particle size of the lead dioxide of large excesses of hydrogen fluoride if satisfactory had a slight but measurable effect on yield, the optiyields are to be obtained ; those employing preformed mum being about 40-60 mesh. Lead tetrafluoride is metal fluorides usually involve elemental fluorine or presumably an intermediate in the fluorination process; chlorine trifluoride which require special handling however, if the olefin was added to preformed lead tetratechniques. The olefins studied include a variety of fluoride under conditions which afforded a maximum two-, three-, and four-carbon olefins substituted by yield in the one-step process, the yields and conversions various combinations of fluorine, chlorine, and bromine, were very low. The optimum ratio of sulfur tetrabut perfluoro olefins and those containing iodine have not been investigated. The reaction conditions usually fluoride to trichloroethylene was about 5: 1. The function of excess sulfur tetrafluoride is most likely that of a employed would be expected to result in extensive resolvent in which the olefin double bond can be easily placement of iodine. The recently reported preparation of metal fluorides polarized. by the reaction of the corresponding oxides with sulfur Fluorination of either cis- or trans-l,2-dichloroethyltetrafluoride" suggested the possibility of employing ene yielded both dl- and meso-l,2-dichloro-l,2-difluorothis reagent for' the in situ preparation of the metal ethane, although in slightly different ratios. It was fluoride used in the fluorination of double bonds. The shown in separate experiments that the olefins were anticipated advantage lay in the fact that water would thermally stable and were not isomerized, at the reacnot be one of the products, thus eliminating the need for tion temperature employed, by either lead dioxide or a large excess of the fluorinating agent to drive the by sulfur tetrafluoride alone. It would appear, thereformation of the metal fluoride to completion. The refore, that the two fluorines being added cannot add sults obtained on treating nineteen halogenated olefins, simultaneously, and that a cyclic intermediate cannot including four perfluoro olefins and two containing be involved. The possibility that the reaction proceeds via addi(1) T h i s work was performed under the auspices of the U. 9. Atomic tion of sulfur tetrafluoride to the double bond is not Energy Commission. ( 2 ) A. L. Henne and T. P. Waalkes, J . A m . Chem. Soc., 67, 1639 (1945). thought to be likely. The haloalkyl sulfur trifluorides (3) A. L. Henne and W. J. Zirnrnerschied, ibid.. 67, 1235 (1945). that would be formed by such an addition appear to be (4) A . F . Benning and J. D . Park, U. S. Patent 2,437,993 (March 16, 1948). stable at temperatures considerably above those em(5) C. I. Gochenour, U. S. Patent 2,554,857 ( M a y 29, 1951). ployed here. l 2 For example, heptafluoropropyl sulfur (6) G. Fuller, M . Stacey, J. C. Tatlow, and C. R. Thomas, Tetrahedron, trifluoride has been prepared12 by addition of sulfur 18, 123 (1962). (7) A. L. Dittman and J. M. Wrightson, U. S. Patent 2,690,459 (Sept. tetrafluoride to hexafluoropropene in the presence of 2 8 , 1954). cesium fluoride at 150°, whereas we found that sulfur (8) D. A. Rausch, R . A. Davis, and D . W. Osborne, J . Org. Chem., 18, tetrafluoride and hexafluoropropene in the presence of 494 (1963). (9) A. L. Henne a n d K . A . Latif, J . A m . Chem. SOC.,76, 610 (1954). lead dioxide a t 100' gave octafluoropropane in 63% (IO) J. Muray, British Patent 878,585 (Oct. 4, 1961). (11) A. L. Oppegard, W. C . Smith, E . L. Muetterties, and V. A. Engelhardt, J. Am. Chem. S O C .81, , 3835 (1960).
(12) R . M . Rosenberg and E. I. Muetterties, Inorg. Chem.. 1, 756 (1962).
BISSELLAND FIELDS
1592
VOL. 29
TABLEI LE.4D DIOXIDE-SULFCR TETRAFLUORIDE FLUORIXATION O F HALOGENATED OLEFIXS
_--Olefin
CFz=CF,
Product(s)
IC& CzFa
C4Fioh C3F8 C4FIO C~CIO-C~F~ CFaCFzCl CF3CF2Br CFZCFzI CFBCFClL CFzCF2CFzCFClCFCP L L -A CFClzCFClz CC1,==CC1~ CFClzCFzCI CClz-CFC1 CF?=CHF CFICHFI CFCIXHFCI CClz=CHCl CHF=CFCl CHFzCF2CI CFSCHFI CFz-CHI CFaCH2F CFz=CHz CCI*=CH, CFClzCHzF ( dl-CHFCICHFCI czs-CHCl=CHCl meso-CHFClCHFCI dl-CHFClCHFCl trans-CHCl=CHCl meso-CHFClCHFCl CH2FCHFBr CHz=CHBr a See under Chromatography in the Experimental section. isomers. CFICF =CF, CF8CF =CFCF3 Cyclo-C'r Fg CFz=C FC1 CR- C FBr CFI=CFI CF,= CCl? CFzCFzCFzCCl=CCI
1
1
% yield
% conversion
2 5 6 63
1 8 7 0
23 60 57 65 87 46
0 0
2 5 6 42
