ACKh-OWLEDGMENT
Acknowledgment is gratefully made to the Ethyl Corporation for defraying the expenses of this investigaticn. Thanks are extended L. A. Bigelow of Duke University for helpful suggestions regarding the C-type fluorine generator. LITERATURE CITED
Cady, G. H., Rogers, D. A., and Carlson, C. A,, ISD. C N G . CHEY.,3 4 , 4 4 3 - 8 ( 1 9 4 2 ) . (2) Cady, G . H., et al., I N D . E N G .CHEM.,3 9 , 290 (1947). (3) Calfee, J. D., and Bigelow, L. Ai.,J . .4m.Chem. Soc., 5 9 , 2072-3 (1)
(1937). (4)
Vol. 39, No. 3
INDUSTRIAL AND ENGINEERING CHEMISTRY
384
(5) (6) (7) (8)
I b i d . , 62, 267-9 ( 1 9 4 0 ) . Fowler, It. D., et al., I s u . E x . CHEY.,3 9 , 343 ( 1 9 4 7 ) .
Ibid., 3 9 , 292 ( 1 9 4 7 ) .
Fukuhara, N.. and Bigelow, L. A , , J . Am. Chem. Soc., 63, 758-91
(1941). (9) Ibid., 6 3 , 2792-5 ( 1 9 4 1 ) . (10) Hadley, E. H., and Bigelow, L. A, Ibid., 6 2 , 3302-3 ( 1 9 4 0 ) . (11) Ligett, W. B., and IZobb, It. M.,private conimunication. (12) Simons, J. H., and Block, L. P., J . Am. Chem. Soc.. 5 9 , 1407 (1937). (13) Ibid., 61, 2962-6 (1939).
PREBESTED before t h e Syniposiurn on Flutirine Chemistry as paper : 2 . Division of Industrial and Engineering Chemistry, 110th Xeeting of SOCIETS,Chicago. Ill. Abstracted from a doccoral thesis submitted by L. I). Bechtol t o the faculty of Purdue University.
A h i E R I c a s CiIEkiIcAL
Calfee, J. D., et al., I b i d . , 6 1 , 3552-4 (1939).
Preparation of
CHLOROFLUORO DERIVATIVES OF ETHYLBENZENE ETIIYLBExZENE was chlorinated E. T. McBee, H. B . Hass, G. >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 with hydrogen fluoride in t h e presence of antipentachloroethane. Phenylpentachloroethaneand (chloromony pentachloride prior to the catalytic chlorination. This pheny1)pentachloraethane were fluorinatedat atmospherir process is illustrated by Equations 4 and 5: and at superatmospheric pressures with hydrogen fluoride 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
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
(1) (2) (3)
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.
+
+
+
+
+ SbF:
~~
+ CaFI6
+ Sb salts
(0)
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
INDUSTRIAL AND ENGINEERING CHEMISTRY
March 1947
385
ethane, which precipitated upon addition of acetone, melted a t 156' C. after recrystallization from carbon tetrachloride and acetone (Table I).
30
I 0
Figure 1.
I
I 80
/60
I
I
I
240
I
I
320
n/.v/.uArf; nL.
Rectification Curve for (Chloropheny1)penta(ch1orofluoro)ethanes
too high or chlorine flow \yere interrupted, the mixture became dark and further reaction was hindered. I n the other procedure, water was added t o the ethylbenzene before chlorine introduction. A quantity of water equal to about 5% by n-eight of the ethylbenzene was sufficient. When this procedure was used, the reaction temperature could be maintained at 100" C. throughout the entire chlorination xithout discoloration. Folloxing the lat,ter procedure, phenylpentachloroethane n-as prepared from ethylbenzene in 24 hours of continuous chlorination as compared \\-ith a period of several days in the former procedure. At temperatures higher than 150' C. extensive chlorinolysis occurred. Phenylpentachloroethane m s obtained from the reaction mixture by distillation a t reduced pressure. Most of the product distilled in the temperature range 128-112" c. a t 4 mm. of mercury, crystals separating from the distillate when cooled. These crystals melted a t 35" C., the reported melting point of plienylpentachloroethane ( 1 ) . When subjected to further chlorination or t o fluorination, the solid and the liquid from which the solid separated gave essentially the same reaction products, an indication that the distillate \vas substantially all phenylpentachloroethane. The undistilled material was satisfactoxy its starting material in subsequent catalytic chlorinations. C i T A L Y T I C CHLORINATION OF PHENYLPENTACHLOROETHANE
Phenylpentachloroethane was catalytically chlorinated in the apparatus described for photochemical chlorination of ethylbeiizene. One hydrogen atom in the aromatic nucleus of phenylpentachloroethane was replaced by chlorination in the presence of 0/37/f 1AT€, ML. light at 130' C. for 24 hours. Further substitution of hydrogen in the aromatic nucleus by chlorine did not occur TT-ithout the aid Figure 2. Rectification Curve for (Tetrachloropheny1)penta(ch1orofluoro)ethanes of a catalyst, usually iron 01' ferric chloride (FeCI2). (Tetraclilorophenyl)pentachloroet,hane \{-as prepared by chlorinating phenylpentachloroethane for about 11 hours in the presence of iron or ferric chloride at 140-160" C. P R O P E R T I E S O F CERTAIN POLYHALOETHTLBESZESES TABLE I. PHYSICAL Extensive chlorinolysis occurred upon naly t ical Data----Boiling Point, C . exposure of jtetrachloronlieii~1)~~eiita70 c1 Cb F .\Iol. W t . _____ At i45 .\lelting chloroethnne t o chlorine for a longer Compound m m . A t 1 m m . Point, ' C. Calcd. Obsvd. Calcd. Obsvd. Calcd. Obsvd. tinie or at higher teniperatures. Sfter C6HC11C2Cla ... 156 76.7 7 6 . 8 416 416 ... 50.6 49.8 2 i : S 2318 350 358 removal of dissolved chlorine and hydroCeHClrCzC1Fd . . . 89'92 ... CsHClrC&lzFa ,,. 106-108 ... 58.0 58.2 15.5 17.1 gen chloride hy passing air through the C ~ H ~ C I C ~ C ~ ~213 FP 52-56 ... 40.5 41.2 21.6 22.4 263:5 274 13.6 14.2 280 275 C~HaClC2Cl.zFnb 245 72-73 50.7 51.1 molten material, the product was exc ~ c , ~ c ~ c ~. . ~. E ~. . . 120l121 68.0 67.6 9.1 8.2 ... ... ... ... 65-66 61.9 61.7 1 4 . 1 14.1 ... ... tracted ITith carbon tetrachloride t o C6C1&~C12F~ The density was found t o be 1.498 a t 25' C.: refractive index, 1.4818. separate the organic compounds from iron 6 The density was found t o be 1.537 a t 25' C . ; refractive index, 1.5140. salts. (Tetrachloropheny1)pentachloroO
Q
INDUSTRIAL AND ENGINEERING CHEMISTRY
386 TABLE
Vol. 39, No. 3
chlorotetrafluoroethane and (tetrachloropheny1)dichlorotrifluoroethane, as shown by analysis of these two materials in Table 1. The degree of fluorination was increased by increasing the PRESSURE weight ratio of antimony pentachloride t o (tetrachloropheny1)E-752 E-753 E-i60-S E-F-16 pentachloroethane (,Table 111). The degree of fluorination was C ~~H, I C I C ~ C I ~ also increased by increasing the temperature. A lengthy period CsHsCgCls C6HnC2Cls C ~ H I C ~ C ~ C 150 1165 557 700 of contact of the polychloroethylbenzenes and hydrogen fluoride 1100 1200 700 2830 0 215 95 453 u p t o about 20 hours appears desirable. 160 150 164 135
11. FLUORISATIOS OF
PHESYLPEST.4CHLOROETHANE (CHLOROPHEXYL)PENTACHLOROETHASE AT ATMOSPHERIC
AND
NO.
CXDt.
Reagents Organic Grams HF, grams SbCLbgrams T e m p , C. Time, hours Product \Vt., grams
R C1 RE
6
. . I
60.9 0
8
11
21
450 47.0 12.5
90 45.8 17.1
87 8 49,s 11.8
CII LORINATION OF (CHLOROPHENYL)CI1 LOKOPEI?FLUOROETHANES
Plienyltrichlorodifluor~~ethaneand (c1ilorophen~l)triclil~irodi-
fluoroethane \\-ere chlorinated in a manner similar t o that deTABLE111. FL~ORISATIOS OF (TETRACHLOROPHESYL)PESTAscribed for the chlorination of phenylpentachloroethane. Each CHLOROETHASE Exut. S o . (Tetrachloropheny1)pen:achloroethane, grams HF,granis SbClj, grains Weight ratio, CaHCldSbCls T e m p . , C. Time, h o u r i Pressure, Ib./sq. i n . Product
E-740
E-741
E-742
1;-F-24
270 110 90 3 0 153 12 1200
270 110 90 3 0 236 12 1500
300 110 168 1 8 250 16 1500
170 90 90 1 9 23" '20 1300
R c1 L7ck
5%
conversion
yielded the same perhalo compound (pentachlorophenyl)tric1ilorodifluoroeth:ne. Similarly, jclilorophenyl) diclilorcitrifluoloethane was converted to (~~~iitachloroplien~-l~dichlorotrifluoroc~t1i:iiie. Table I presents analytical data for these compounds. The temperature of chlorination !vas very critical, inasmuch as occurred above 160" C.; at temperatures below 150' C., conversions to the desired perhalo compounds were con,iiderabl>-less efficient. ACTIOA OF SbFs O S IIIGMLY €I.ALOCES.ATEL) ETIIY-LBEYZE3 E S
Although some replacement occurred n-hen tlie reaction was carried out in an autoclave a t autogenous presures n-ith antimony pentachloride, i t n-as found more convenient t o niix the plienylpentachloroethane ii-ith antimony pentachloride and to bubble anhydrous hl-drogen fluoride into the mixture (Table 111. The amount of fluorine in tlie product increased with an ii1crea.x in the \\-eight ratio of antimony pentachloride to plienylpentachloroethane. FLUORIS4TION OF (TETR.ACHLOROPHE3~ul-L)PE~~.ACH LOROETHAS E
Experiments >lion-edt h a t n o react ion occurred tietiveen i tetrnclilorop1ieii~l)pentacl~loroethariesand aiihydrou. liydrogeii fluoride in the absence of a catalyst, and that reaction occurred hen (tetraclilorop1ienyl)pentacliloroethane15-as treated \\ it11 lij-drogen fluoride and antimony pentachloride a t autogenous prei-ure.. ..lccordingly, (tetrachloropheny1)peiitachlo~oetliane n a s fluoi,inated with hydrogen fluoride in the presmce of antimony pentnchloride in a nickel-lined autoclave of 600-1111. capacity. The head of tlie autoclave vas attached by eompresion fittings to a nickel block fitted with a safety dirk arid a needle valve. The autoclave vas heated electrically. .4 rocking device provided agitation of the reaction mixture. Temperatures ivere determined with a thermocouple placed between heater anti autoclave. (Tetrachloro~~lieny1)pe~itachloroetl~a~~e and antimolly pentachloride were mixed in the autoclave, and hydrogen fluoride \\-a$ introduced from a small weighed cylinder; addition of hydrogen fluoride n-as facilitated by applying heat ,to the cylinder. When addition v a s complete, the reaction mixture was heated, \\-ith agitation, t o 150-200' C. After a predetermined t i p e , the autoclave n a s allon-ed to cool, and the gaseous hydrogen h l i d e s \\-ere d i d i a r g e d into a dilute solution of sodium hydroxide. The niain product, a brovnish liquid, as poured from tlie autoclave. T o ensure complete removal of organic materials, the autoclave v a s Jvashed with carbon tetrachloride, and the vasliings were combined n-ith the niain product. The combined product \vas freed of antimony salts by washing several t inies with hydrochloric acid and of acidic substances by wishing with water. After drying, carbon tetrachloride was removed by distillation a t atmospheric pressure. The distillation residues coniprising (chloroplienyl)penta(chlorofluoro)ethanes were rect,ified a t 1-2 mni. of mercury pressure. Figure 2 shows the curve obtained by plotting rectification data for one of the products. Plateaus in t h e curve a t 89-92" and 106-108" C. are (tetracliloropheny1)-
The 1 s t step in the plan for the synthesis of perfluoroethylcycloliesaiie from ethylbenzene involved the reaction of antimony pentsfluoride n-ith a perhalogcnatcd etliylhenzene. Thew remt!ions were carried out in a three-necked fiask, equipped with a mercury-sealed stirrer, a condenser, and a thermometer placed in the reaction mixture. S o apparent reaction occurred until tlie material in the f l a k v a s n-armed to 50" C., at which time dense fumes formed in the flask and the temperature rose rapidly t o 130' C. Effective temperature control \\-as acahieved bydrop13ing tlie antinionj- pentafluoride into tlie n-eli stirred ethylbenzeiie derivative at 60-70" C. The orgaiiic product \va> sepLirated h n i the antimony salts by \\-ashirig the reaction mixture \\-it11a mixture of cracked ice and hydrochloric acid. Results from a large number of ex1)erirnents \\-it11 both ~tetr~icliloro~~heii~1)pentactiloroethaiie and iy~cntac.lilolopIieny1~diclilorotrifluoroethlne showed that antimony [ ~ n t a f l u o r i d e i cau-ed carI)on-c~irlioiicleavage. Hexachlorobenzeiie ~ v a isolated and ideutified. -41~0,compounds belie\-ed to be chlorofluoroethanes and clilorofluoiocycloliexenes v-ere obtained. Hence, clilorinoly.-i~as well as fluorinoljsis occurred. Possihly antimony peiitafluoride n'as converted t o a compound cuch as SbClzFS by replaceinelit of chlorine atoms in the side chain n-ith fluorine. Under the conditions he reaction, SbCI?FJmay have acted as an agent for clilorinol A C K S O W LEDG.\lEST
The author? \\-ish to acknon-ledge the a 'tance of J. F. Miller, .4.AI. Riblcy, M. D. Iiinzie, and RI. H. Danzig for performing the analyieb. This nork \vas initiated under the sponsorship of the Office of Scientific Researcli and Development and concluded under the auzpices of the L.S. A h m yCorps of Engineer.. LITERATURE CITED (1) (2)
Biltz, H . , A n n . , 296, 263-78 (1897). AIiller. J. I,',, Huiir, H . arid AIcBee, E. T., IZ71al. Chem., 19, 148
(1947). (3) Yinions, J. H., mid Hemian, D. F.,J . Ant. C'hem. Soc., 65, 2064-6 (1943). before the Synipoiiurii on I:luorilIe Chenlistry ad p a p e r 71, Dirisiuii of Industrial a n d Engineering Chemistry, 110th l l e e t i n g of the AXERICASCHEMICAL SOCIETI.Chicago, Ill. Thiy paper w m ab3rracted iron1 the the$]> subniirted to the faculty of I'urdue UniT-ersity by G . AI. Rothrot,k. T h e work descrlbed in this paper is covered also in a comprehenaive report of work with fluorine a n d fluorinated compounds undertaken in coiiiiection w-ith the N a n h a t t a n Project. This report is soon to be published as ToLume I of Division TI1 of the M a n h a t t a n Project Technical Series. PRESESTED
