380
INDUSTRIAL AND ENGINEERING CHEMISTRY
scr was replaccsd by a distilling column, and the pot temperature was gradually raised to 180" C. Heating was continued for a n additional 12 hours. Then the temperature n.as lovered to 100" C., a n d steam was introduced into the mixture whereby an additional 40 ml. of product were recovered. The entire distillatc, after washing with sodium carbonate, hydrochloric acid, and water, weighed 404 grams. Upon rectification, products similar t o those of dehalogenation in ethanol were obtained, with a somewhat higher percentage of lower boiling compounds. PREPARATION OF PERFLUOROTOLUENE
Bromine t,rifluoride was placed in the nickel reactor and c ~ o l c d to 0" C. Pentachloro(trifluoromethy1)benzene was added a t the rate of 100 grams per hour, with heating t o 85' C. after each 100-gram portion and cooling again t o 0" C. before the addition of a further portion. K h e n all of the pentachloro(trifluoromethy1)benzcne had been added, the mixture was heated at 100" C. for 4 hours. Four batches, involving the reaction of 1863 grams of bromine t,rifluoride and 1454 grams of pentachloro(trifluoromethyl) benzene, yielded 1433 grams of liquid product having the average composition C6Br2C13F6(CFJ). Fifteen hundred and ten grams of material having an avcraye composition CsBr2Cl3F6(CF,)was placed in a three-neck Pyres flask and heated t o 60-70" C. Antimony pentafluoricle (730 grams) \vas added during 6 hours with constant stirring. .Ifter heating at 120" C. for several hours, the reaction mixture \vas cooled and washed free of antimony salts with concentratcd hydrochloric acid. The product (1300 grams) was a pale yellon. liquid of average Composition C6BrC13F7(CFa). Dehalogenation of the above mixture n-as carried out in ethanol. The product was added t o a suspension of 600 granfi of zinc dust in 500 nil. of ethanol at reflux temperature. A%ddition took 8 hours, during which period another 200 ml. of ethnnol \vas
Vol. 39, No. 3
added to reduce the viscosity of the mixture. The temperatut,c: was then raised to 140" C. while ethanol and some products distilled from the mixture; the remaining products were removed by steam distillation. Ethanol was washed from the halocarbon products with xvater, and the products were dricd over Dricritcx. The dry mixture (727 grams) was rectified in a 4-foot Podbielniak Hyper-Cal column. Intermediate olefinic fractions wew rorectified in a 4-foot glass-packed column. From these rectific:itions wcre obtained 121.9 grams of perfluorotoluene, 219.4 grams of chlorotetraflnoro(trifluoromethyl)benzene, and 162.2 grams of dichlorotrifluoro(trifluoromethy1)benzene. Intcrnicsdiate fractions contained dichloroheptafluoro(trifluoromc.thr.1) c y c l o h e x c n e , trichlorohexafluoro(trifluoroniethgl)c~clolic~scnc, and some perhalo(trifluoroinethy1)cyclohexadicnea whicli ~ v c w identified from data obtained by a different process ( 3 ) . l'hysiea1 constants and analyses of compounds prepared from lxari t iichloro(trifluoromethy1)henzeiie arc givc:n iii Tal)lc~11. ACKNOWLEDGMEST
Thanks are extended t o the Ozark Chemical Company for financial assistance which made this work possible. LITERATURE CITED
H. ,
R..XlnBee, E. T., Hinds, G . E., and
Glueserikaiiili, ('.
I n . E x . CHEM.,28, 1178-81 (1936).
( 2 ) Lcheau, P..Com71t. rend., 141, 1018-20 (1905). (3) MrBee. Linilgreri, and Ligett, unpublished data. (4) S u r t i i i g , H. .9., and Petrie, P.S,, C . 8 . Patent 1,9Gl,ti22 I. Rothrock', J. S. Newcomer, photochemically to give phenylW. V. Clipp2, Z . D. Welch, and C. I. Gochenour3 pentachloroethane and (chloropheny1)pentachloroethane; upon PURDUE USIVERSITY AND PURDUE RESEARCII FOUNDATION, LAFAYETTE, I S D . further chlorination in the presence of ferric chloride at 110-160" C., .4n alternative procedure involved the fluorination of phenylthese compounds were converted to (tetrachlorophenj-1)pentachloroethane. Phenylpentachloroethaneand (chloropentachloroethane with hydrogen fluoride in t h e presence of antipheny1)pentachloraethane were fluorinatedat atmospherir mony pentachloride prior to the catalytic chlorination. This and at superatmospheric pressures with hydrogen fluoride process is illustrated by Equations 4 and 5: in the presence of antimony pentachloride to giye compounds having 1, 2, and 3 chlorine atorns replaced by (4) C S H ~ C ~ C ~5HF : ShClj ----+ C&C:F5 5HCI fluorine. (Tetrachloropheny1)monochlorotetrafluoroethane and (tetrachloropheny1)dichlorotrifluoroethanewere (5) obtained by fluorination of (tetrachlorophenl-1)pentaCsIIhCyF; 5Clz FeCl.4 ----+CsCljCpF5 5HCl chloroethane with hydrogen fluoride in the presence of antimony pentachloride at superatmospheric pressure$. As a final step iri tile synthesis, it was proposed t h a t tpentaChlorafluoro derivatives of phenylpentachloroethaue and chloropheiiyl!i)entatiuoroethane be treated with ant,imony of (chloropheny1)peutachloroethane were converted to pentafluoride for conversion to [ ~ e r f l ~ ~ o r o e t h ~ l c y c l o h e x(CBF,6) nne (pentachlorophenyl)penta(chlorofluoro)ethaiies by chloas illustratctf i n 1,:quation 6: rination in the presence of iron. CsCI;CJ?j SbF: + C a F I 6 Sb salts (0)
+
+
+
+
+
P
ERFLCOROETHTLCTCLOHEX.4XE as considered for use in the separation of uranium isotopes by gaseous diffusion. It was desirable t h a t this material be prepared by a procesa requiring no elemental fluorine. Such a process would desirably entail the replacement of chlorine by fluorine by means of hydrogen fluoride. Accordingly, a process was proposed for the preiiaration of perfluoroethylcyclohexane from ethylbenzene involving photochemical chlorination of the side chain, subsequent catalytic chlorination of the phenylpentachloroethane to [pentachlorophenyl)pentachloroethane, and conversion of the latter compound t o (pentachlorophenyl)pentafluoroethane with hydrogen fluoride The sequence may be illustrated by the following equations:
Cp,H&,H,
+ 5c1, light -+
CsHjC2Clj
+ 5HCI
C6HjC2CIjf 5CL ' ++ C6Cl~Cyc~j - f 5HCl
+
+ 5HCl
C6clsc2c16 5HF 'E5 C6C1,C?F5 +
(1) (2) (3)
1 Present address, E. I. du Ponr de Nemours & Company, I n c . , Buffalo, N. Y. 2 Present address, Huntington Coliepe, Huntington, Ind. a Present address, Hooker Electrochemical Company, Xiagara Falls, K. Y.
~~
+
Generaily, the degree of chlorination or fluorination was not s u high as desired. dlthough the perhaloethylhenzeiies were not successfully converted t o ethylcyclohexane derivatives by ailtimony pentafluoride as originally expected, interesting anti ticsirable intermediates were obtained. The results of the prrparation and properties of these intermediates are described hci,e. PHOTOCHE>IIC4L CIILORISATION O F ETIIYLBENZE3 !I
Ethylbenzene was chlorinated in vertical Pyrex tubes, 120 cm. long and 5.1 cm. in diameter, equipped with a chlorine inlet, a thermometer well, and a reflux condenser. Chlorine \vas introduced into the niaterinl to lie chlorinat,ed a t the bot>tomof the tube through a fritted-glass dispersion disk. T h e reactor \vas illuminated by three 200-watt Mazda lamps, and )\-as heated a t the bottom by an electric heater. Turbulence produced by introduction of chlorine \?-as adequate for maintaining nearly uniform temperature throughout the liquid. Two general procedures iverr followed. In one, ethylbenzene was poured into the chlorination tube and chlorine \vas introduccd a t a rate such t h a t the i~eactioritemperature did not exceed 70" C. for the first f e n hours of chlorination; then chlorination was completed a t 100" C. Careful control of conditions was found t o be mandatory with this procedure, for if the temperature became
