INDUSTRIAL AND ENGINEERING CHEMISTRY
March 1947
'
40 1
decanted. The fluorinated product was trclated as described, 219 and 80 grams (0.27 mole) of antimony pentachloride iwre placed grams of product being ohtaincd. Rectifica in the autoclave: the niisturc n-as heated a t 340' C. for 48 hours fractions: 49 grama of (hrptafluoroisoprop?.1) with constant agitation. T h e autoclave x-asthen cooled to room afluoroisopropyl I txxzene, and 36 temperature, and liquid products w r e decanted from solid anopropy1)bcmene. Conversion t timony salts remaining in the reaction vessel. The fluorinated material n-as ivahhed ivith dilute hydrochloric acid and steamne \vas 1 0 5 and t o (chlorohe diqtilled. TKOhundred grams of crude product vere obtained, benzene 15yc. The yield Tvas 3 5 s . dried, and rectified. Three separate fractions were obtained and T h e compounds ivcrc purified by rcctificntion in a Podbic.lili;ili identified as 43 grams of l-(heptafluoroisopropj-l!-4-(trifluoromethyl)benzene, 83 grams of l-(chlo~olieuaflnoroisoprop~l~i-4- Hyper-Cal column. The physical consrsnt-: and halogen a 1 1 ~ 1 y (trifluoroniethvl)benzene, and 35 grams of 1-(dichloropentases are given in Table I. fluoroisopropvl~-i-(trifluoromethyl)benzen~,Conversion to 1ACKSOWLEDG3IEKT (heptafluoroisopropyl)-&(trifluoromethyl)benzene was 1 3 7 ~and the yield 30c';. The authors \vis11 to ac.l;no\vlcdye the financial assiut:iiii,i, oi rent,y-four granis of a mixture composed of (dichloropentafluoroisopropyl)benzene, tlie United States Ariiiy Air Forces IIstkricl Ccnter and 1,2thyI of (trichlorotetrafluoroisoprop?-l~~enzene, Corporation and grati.fully acknon-lcdgc the annlyticnl \ v ( i i ~ k[ i f 400 gram. ( 2 . 2 moles) of powdered antimony trifluoride, and 90 -4, 11.Ribley in coiincction with thi5 paper. grams (0.3 mole) of antimony pcntachloride 71-ere placed in the ABSTRACTEDf r o m a doctoral theeis of 0 . R . Pierce, tu he s u b m i t t r d t o t h e autoclavc. The reaction was heated at 330' C. for 30 hours and faculty of Purdue University. then cooled to room trmpcrature, and the liquid products w r e
FLUORINATION OF PERHALOGEN OLEFINS R illiaiii T. JIiller. Jr.. Robert L. Ehrenfeld, James 31. Phelan', \\Taurice Prober2,and Sherman IC. Reed3 CORY1 L L L \ I \ E R S I T T
% \ D I H E S . t . \ I . L i B O R 4 T O R I F S O F THE M4\iH4TT421 PROJECT, I T H i C i ,
ELE\lEYT iR1 fluorine was applied for the fluorination of perfluoro- and chloroperfluoro-olefin3 in s y lithesizing saturated fluorocarbons. Direct fluorination of liquid mono-olefins at lo\+ temperatures y ieldecl principally simple fluorine addition and dimer addition products. P, ith a n olefin rontainiug more than one double hond the dimerization reaction could continue paat one stage to yield a series of poljiner products. Loalr temperatures faalored the dimerization reaction, whereas at higher temperatures and i n Lhe vapor phase polymer products could be largely a i oided and simple saturation carried o u t as a continuous process. Cobalt trifluoride w a s shown to be an effectiale fluorinating agent for perfluoro-olefins. This reagent, which represented a n indirect use of elementary fluorine, added fluorine to double bonds to yield saturated products w ithout the dimerization reaction characteristic of free fluorine.
E
7 LEMEXT-4Rl- fluorine was utilized as a fluorinating agent for perhalogen olefins by direct reaction and for the preparation of reactive metal fluorides. The principal products obtained iron1 the reaction of a completely halogenated liquid olefin n-ith fluorine are the normal addition product .4 and the dimer addition product B ( 2 , 7 ) .
-C=C-
+ F2 --+ -C-C
f -C-C-C-C-
I
I
F F d
I F I3
F
Varying amounts of by-products from the replacement of chlorine by fluorine, in t h e case of chlorofluoro-olefins, were usually formed. The replaced chlorine was accounted for as chlorine and chlorine fluoride addition products of the starting olefin and, to a lesser extent, by dimers corresponding t o the addition of chlorine or of chlorine fluoride. The dimerization reaction was of especial interest in t h a t i t represented a distinct type of reaction for fluoPresent address, S t a n d a r d Oil Derelopment Company, B a y w a y . S . J. Present address, General Electric Company, Schenectady, S . Y . a Present address, Bucknell University, Lewisburg, Pa. 1 2
\.
I . . 41D \ F K I O R K .
\.
I.
rine among the halogens and provided a uxeful synthetic method leading to the forination of higher niolecwlar xeight compounds from low molecular weight olefins. FLUORIS.4TIOS I S THE LIQPlI) PHASE
Liquid-phase fluorinations n-ere carried out in apparatus (Figure 1) usually constructed from copper or nickel tubing and in various sizes. The general method was essentially that previously descrihed ( 7 ) . Fluorination occurred rapidly nith the simple perhaloqeii olefins, and a sharp change in fluorine absorption indicated the practical completion of reaction. Solvents such a i 1,1,2-trichlorotrifluoroetlianeor trichlorofluoromethane andlor nitrogen dilution of the fluorine were employed t o moderate reaction conditions and/or t o reduce the viscosities of liquids nt loiv temperatures in some cases. Most of the fluorine used in this work was produced by :Lsmall cylindrical nickel electrolysis cell of a design in use a t Cornel1 for some time (Figure 2). This was operated Tvvitli an electrolyte containing up t o about 1.8 moles of hydrogen fluoride per mole of potassium fluoride ( 5 ) n-ith a current efficiency of about goyG. The rate and quantity of fluorine production were determined by measuring the hydrogen output. The size of cell show1 x a r operated satisfactorily xvith an electrolysis current up to 25 amperes. The purity of fluorine produced and the smoothness of cell operation Ivere found to be essentially dependent upon maintenance of a n absolutely dry electrolyte. A special redistilled grade of anhydrous hydrogen fluoride (supplied by F. B. D o m i n g of the D u Pont Company) was w e d for charging. Fluorine compressed into tanks \vas utilized after a satisfactory technique for bottling n-as worked out (9). The temperature of fluorination had an important be;triiig upoil the t y p e of fluorination products obtained. I m v temperatures favored the formation of fluorine dimer addition products relative to the normal addition product and minimized tlie forination byproducts. Higher temperatures resulted i n proportionally higher yields of normal addition products and of ti)--products associated with the replacement of chlorine in the case of chlorofluoro-olefins. Table I lists yields of purified fractions of typical products which were isolated from the reaction of sym-dichlorodifluoro-
402
INDUSTRIAL AND ENGINEERING CHEMISTRY
established. Although it way thus indicated t h a t the effect of structure upon the dimerization process could be highly important as regards orientation and type of reaction, insufficient comparable data were available to form the basis of a satisfactory generalization. In the case of ethylenic compounds x i t h more than one double bond, fluorine gave appreciatde yields of polymers higher in molecular weight than the dimer, because the dimerizing action lvith fluorine continued past one step; that is, the first fornied dimers contained double bonds which took part in the various possible further saturation and coupling reactions. Considerable fractions of material-: witable for uie as luhricnting oil were produced by the fluorination of perfluorodienes. The proportion of dimerizing artion and hence the niolcc~ularweight distribution of product could he rontrolled approximately hy varying the temperature of fluorination. Hon-ever, complete removal of unsaturation from the viscous products ohtained by fluorinating diolefins under liquid plinse conditions alone xa.? difficult.
COPPER INLET TUBE
RUBBER STOPPER
S I L V E R SOLDER JOINTS
ethylene and undiluted fluorine. The temperatures indicnteti are liquid bath temperatures maintained around the metal reaction vessel. K h e n this reaction was carried out a t -78" C.: a 447, yield of the fluorine dimer addition product C.:ClIF, resulted. Similarly pure products were isolated from the fluorination of 2-chloroperfluoropropene (Table 11). In run 1 the reactor n-as surrounded by c r u h e d dry ice, and the pure olefin was eniployed. The temperature inside the reactor Tras - 5 2 " C. before starting t h e reaction. In run 2 trichlorofluoromet~iane was employed as a solvent, the molar ratio of olefin t o solvent was 1.6 t o 1.0. and t h e reactor v a s immersed in a dry ice-acetone hath which provided more efficient cooling than did the solid dry ice packing. Both reactions \!-ere carried essentially to completion. The mole per cent of reacted 2-chloropcrfluoropropene v h i c h n-as accounted for by each product is li4etl. Fluorine addition and dimerization were the main renctioiis, with dimerization predominating. The fluorine dimer addition products have heen a>signed 1,4 structures as regards the positions of the entering fluorine a t o m ( 7 ) . Ot,her structures require the rearrangement of groupings already present and would be inconsistent with dechlorination results, such as the preparation of 1,3-perfluorobutadiene from the Only one l,4-fluorine dimer addition product of CFCl=CFCl. dimer addition product may be obtained from symmetrical olefins. For unsymmetrical olefins there are three possible products. However, preferred orientation was indicated, and in certain cases one dimer could be shown t o be the principal product. For example, the fluorine addition dimer fraction CdF6C12, obtained by the low temperature fluorination of trifluorochloroethylene, vias dechlorinated t o yield 52.47, of 2-perfluorobutene; this indicated a preponderance of t h e 2,3-dichloro dimer structure CFFCFC1CFClCF3. Similarly a highly preferred orientation was indicated for the dimerization of 2-chloroperfluoropropene. Dechlorination of t h e dimer addition product yielded 92% of perfluorohexene, which would be formed from only one dimer product.
Liquid-phase fluor inat ions irith mono-olefins also included CClz=CCl2 (7), CF ICC1=CC12, CFICI-CF=CF-CFzC1, and CFaCFzCF=CF,; in the-e cases normal reactions leading t o typical product.; as illustmted above were obFerved. From the reaction with (CF,)?C=C(CF,\, at 0 " C., however, little if any dimer product could be isolated. Addition-\vas t h e only reaction
Vol. 39, No. 3
T-IBLI; I.
LQt-m-PH.xsE
FLUORIX~TIOS OF CFCl=CFCl
_ _ _ _l i_e l_d s_of~Pure Products 1aol:i:ed"
Temp. of
Reaction,
~
C.
0 - 55
I?I'~CF~CI 13.0 8.0
CF9ClCF2Cl 19.0 17.4
CFsCICT'Clr 14 8 10 5
Yields of P u r e ProductIwlnteda _ ~ CFCl9CFC1g C4ClrF6 C,CljFj CdCkI!'; 0 3.4 6.5 7.2 4.4 - 55 1.1 30.0 3.8 9.1 Expressed as mole per cent of reacted CFC!=CFCl. Teiilp of Reaction, O C .
a
T.\BLE 11. LIQL-ID-PHISFLCORIXATIOS OF CF, has a number of inherent advantages as compared t o the complete CALCIUM FLUORIDE C E M E N T 7
NICKEL ANODE HOLDER
SILVER SOLDER NICKEL CATHI HOLDER
-
(4-BOLTS 1
0
7 of Product in Fractions Boiling a t : -_ -~ 100 (760 niiii.)-20O0 C . ( 10 I11111 " 21 5 43.8
m-t. C$F,?, >roles F?/ Grams Mole C ~ F I ?90-10O0 C . " 403.7C 0 46d 64 7 171.1'' 2 0 35.6 a Largely composed of Cs fraction. b Largely compo-ed of C.s a n d C24 fractions. C Reaction a t - 7 8 ' . d Reaction discontinued considerably before completion e Reaction a t 0'.
COPPER [ GASKETS
3
Residue
r-
5.0 24.1
ST-L RING' (3'BOLTS 1
/
-'
TABLE 1.. Run S o .
; 3 4
FLI-ORIS-LTIOS O F P E R F I . L ~ O R O B T ~ T . I I ) I B S ETRIMER
TTt CI2F.., Moles Fd Grains Mole ClzFia 303 C 0 59 :3Oc 0.65 -96c 0 56 35id
1.2
c; of Product _____
i:i
rrnctions Boiling a t :
