CA1179687A - Fluorinated 3-ketoglutaroyl halides and polymers therefrom - Google Patents

Abstract

TITLE
Flourinated 3-Ketoglutaroyl Halides and Polymers Therefrom ABSTRACT OF THE DISCLOSURE
Compounds having the formula:

Description

TITLE
Fluorinated 3-Ketoglutaroyl ~alides and _ Polymers Therefrom -BACXGROUND OF THE INVENTION
_ Field of the Invention ~ ~ .
Thi.s invention relates to ce~tain ~luorinated acid halides of 3-ketoglutaric acid, to polymers there from, and to reaction products of said polymers.
Relation to Prior Art __ Copolymers of ethylenically unsaturated com-pounds and polyfluoroketones of the type o X-CF2CCF2X ' are disclosed in U.S. Patent 3,342,777 to Howard, where X and X', independently, may include F, Cl, perfluoro-alkyl, ~-halo- and ~-alkoxy-perfluoroalkyl substituents.
Ketodiethers of the type o are known in U.S. Patent 3,988,537, as is the hydrolysis o~ CF2OR groups to -CO2R, and the conversion of ether groups -CF~OCH3 to -COF by the action of SO3,D. C.
England et al, J. o~ Fluorine Chem.istry 3, 63 (1973-74).
Ketomonoesters of the type o C}~3CCF2C02R

tR = H, C2H5), and their preparation by reacting a difluoroacetate with a trifluoroacetate, are also known, McBee et al, J. Am. Chem. Soc. 75, 3152 (1953) and 75, 4090 ~1953).

'R-7825 1 7~6~37 SUMM~RY OF THE INVENTION
, . .
This invention comprises fluorinated ketones having the formula O=C(CF2COX)2 where X i5 F or Cl, copolymers o these ketones which contain the chain segment ~O-C~
~ C 2 where Y is -COOR; R is ~, alkyl of l to 8 carbon atoms, cycloalkyl of 7 to 8 carbon atoms, phenyl, alkaryl o 7 to 8 carbon atoms, an alkali metal, a metal of Group IIA or IIB, ammonium, or yuaternary ammonium, -COF, -COC1, -CN, -CONH2, -CONHR
where R1 is alkyl of l to 8 carbon atoms, cycloalkyl lS of 7 to 8 carbon atoms, phenyl, alkaryl of 7 to 8 carbon atoms, -CH2NH2, -CH2OH. Many of these co-polymers are obtained by reacting the copolymer containing the acid halide group with another compound.
The copolymers of the invention are useful or providing cure sites in elastomeric compositions, as metal pro-tective coatings, and in ionizable -COOH or -COOM forms, as electrically conductive and water-wettable, dyeable resins.
DETAILS C)F _~IE INVFNTIO
The fluorina~ed monomers o~ this invention are derivati~es of 3-ketogluta~ic acid and have the formula O=C(CF2COX)2 where X is F or Cl. These compounds are prepared by reacting bis~2-alkoxytetrafluoroethyl) ~etones with sulfur tri~xide:
o R O(CF2)2C(CF2)20R + 2SO3----~O=C(CF2COFj2 + ~R 0502F

where Rl is, independently, ~, CH3, C2H5~ CH2CH2CH3 or CH2CH2CH2CH3. Tetrafluoro 3~ketoglutaroyl fluoride may ~7~

be converted to the corre~ponding acid chloride by passage, in vapor ~orm, ovex solid calcium chloride

2 ~2 CaC12-i~ O=C(CF2COCl~2 ~ CaF , and to diesters by alcoholysis O=C(CF2COF)2 ~ 2R3H ~ O~C(CF2COOR)2 ~ 2HF
Such diesters can also be prepared by contacting bis(2-alkoxytetrafluoroethyl) ketones with strong protic acids such as c~ncentrated sulfuric acid, as described in U.S. Patent 4,304,927 of Krespan, which issued 1981 December 08:
Q o R o(CF2)2C(CF2j2oRl H RlO2CCF~CCF2CO2Rl Generally a mixture of 1-4 parts of concentrated sulfuric acid and l part o~ fl~oroether are allowed to react until exothermic reaction is complete; the product is isolated by distillation.
Bis(2-alkoxytetrafluoroethyl) ketones are prepared from ~etrafluoroethylene, a dialkyl carbonate and a metal alkoxide as described in U.S. Patent 2,988,537 (Wiley) MORl ~ CY2=CF2 + (R1O~2C~ ~ R1O~F2CF2COORl + ~1OH ~ M

MORl + ~F2=CF2 t (Rlq)2co ~ RlOCF2CF2CCF2CF2O~1 + ~lo~ ~ M
where Rl is, independently, as de~ined akove. Normally the above reactions pr~ceed conc~L~rently, producing a mixture of compounds. The ketone may be separated, e.g. by distillation, from the ester product before -reaction with SO3. However, it has been found that the yield of perfluorQ-3-ketoglu~aroyl fluoride is actually improved if a mixture of compounds as pxoduced in the above reactions is reacted with SO3.

~7~6l97 Preparation o~ mixture o~ compounds requires the addition of one or t~o moles of tetrafluoroethylene to a mixture of one mole of alkali metal alkoxide and one mole of a dialkyl carbonate i~ a dry (moisture-free), inert solvent such as tetrahydrofuran, diethyl ether, 1,2-dimethoxy ethane and the like. Alkoxides of sodium are preferred, though other alkali metals are also functional. Suitable alkoxides are those of straight chain aliphatic alcohols of up to seven carbon atoms, particularly the alkoxides of shorter chain alkanols of from 1 to 4 carbon atoms such as methanol, ethanol, n-propanol and n-butanol.
Carbonate esters useful in the synthesis of the mixture of compounds are those of straight chain aliphatic alcohols of up to seven carbon atoms, pre~erably those of alkanols of from 1 to 4 carbon atoms.
The reaction of SO3 with bis~2-alkoxytetra-fluoroethyl) ketones or mixtures thereof with

3-alkoxytetrafluoropropionates is normally carried out using 1 to 10 mols of SO3, preferably 1.5 to 4 mols of SO3 per equivalent of -C~2OCH3 groups in the ketone or ketone/propionate mixture. Reaction temperatures may be about 25 to ahout 150~C, preferably 40 to 100C.
Ketones o this invention, O=C(CF~COX)2, undergo free radical initiated copolymerization by the method described in U.S. Patent 3,342,777 (Howard) with one or more ethylenic compounds selected from among the following: tetrafluoroethylene, chlorotrifluoroethylene, l,l-dichlorodifluoroethylene, vinylidene fluoride, vinyl fluoride, trifluoroethylene, ethylene, hexa-fluoropropylene, perfluoromethylvinyl ether, bromotrifluoroethylene, methyl acrylate, methyl methacrylate, vinyl aceta~e and acrylonitrile.

Copol~merization of these formula ketones ~ith one or more ethylenic comonomers, is initiaked by free radicals derived from any suitable source, particularly organic peroxides such as perfluoro~
propionyl peroxide, benzoyl peroxides, persulfates or azonitriles. Perfluoropropionyl peroxide is a pre-ferred initiator. Initiator concentration is determined by the nature of the initiator used, the nature and reactivity of the comonomers, and the desired polymer molecular weight. Perfluoropropionyl peroxide is normally used at concentrations of about 0.01 to 1 mol ~, preferably 0.05 to 0.3 mol ~.
Reaction is carried out in an oxygen-~ree atmosphere, with either an inert solvent such as 1,2,2,-trichloro-ethane or 1,2,2-trichloro-1,1,2-trifluoroethane or without added solvent, at pressures and temperatures determined by the nature and reactivity of the co-monomers and the desired product composition. A
pressure reactor is used with low-boiling monomers.
The present invention also includes the copolymers obtained by polymerizing the ketones con-taining side chain acid halide ~unctions with ethylenic compounds. Such copolymers consist essentially of recurring units of at least one ethylenic compound in a ratio o~ about 1:1 to about 20:1 to recurring units o~

--O--CI--where X is defined as above~
Acid halide functions in ~he polymers of this invention may be partially or completely hydrolyzed-by-water or aqueous al~ali to carbo~ylic acid groups; e.g. ~

1~7~D~8~7 H O
-CF2COX ~ CF2C02H
tOH ,) The acid halide functions may also be converted by alcoholysis into ester unctions CF2COX ROH ) CF2CO2R

Use of polyhydric alcohols, such as ethylene glycol, results in cross-linked, intractable structures (Example 7). Some or all of the side chain -CO~H
groups or acid halide groups may be converted, by known met~ods, to derivative functions. Thus, the present invention provides novel copolymers which contain within the polymer chain segments of f CF2Y
~-C , CF2~ J
where Y is -COOR (R=H, alkyl of 1 to 8 carbon atoms, cycloalkyl of 1 to 8 carbon atoms, phenyl,alkaryl of 7 to 8 carbon atoms, an alkali metal, a metal of Group IIA or IIB, ammonium or quaternary ammonium), -COF, -COCl, ~CONH2, -CONHR1, where Rl is alkyl of 1 to 8 carbon atoms, cycloalkyl o 7 to 8 carbon atoms, phenyl, alkaryl o~ 7 to 8 carbon atoms, -CH~NH2, -CH2OH, or -CN.
Tho carboxylate salts (R-M) are obtained by treating the pol~mer in its -COOH or -C02R forms with alkali metal or Group IIA or IIB metal hydroxides, carbonates, or salts of organic acids such as acetates, formates and the like; ammonium hydroxide or quaternary ammonium hydroxide.
Primary amide functions (-CO~H2) are intro-duced by reacting the polymer in its acid halide or carboxylic ester form with concentrated a~ueous or .~,................................................................ . .~ 6 ~ ~t7~

gaseous ammonia, e.g.
--T' NH3 ~r-CF2COCl ~ ~ CF2CONH2 + ~Cl Substituted amide functions (-CONHRl) are introduced by reacting the polymer in its acid halide form with a primary amine, e.g.

CF2COF f ~2N ~ ~ CF2CoNH ~ + HF~H2N-'~
(Example 14) Amine t-CH2NH2) and a}cohol (-CH20H) functions can be introduced by catalytic hydrogenation of the amide~or nltrile, and ester forms respectively;
lithium aluminu~ hydride is a suitable reagent.
Nitrile (-CN) functions are introduced by the dehydration o~ the amide ~-CONH2) groups with a suitable dehydrating agent such as P2O5 or POC13O
Procedures for carrying out the above conversions are described i~ organo-fluorine chemistry texts including ~ovelace, Rausch & Postelnek 'tAliphatic Fluorine Compounds", Reinhold Book Corp. (1958).
The polymexs of thi~ invention, depending on the choice of side chain functionality, are useful as curing agents for elastomeric compositions, water we~table dye sites ~or catonic dyes, metal protective coatings, ion-conductive materials; all are suitable ~or conversion to ~ilms and fibers. Polymers in the form of acid salts, particularly the carboxylates o~ Zn and Mg , are unusually tough, strong thermoplastic materials (Example 13).

The following examples illustrate~ways of carrying out the present invention. All par~s and percentages are by weight unless otherwise s~ated.

~7~87 EXAMæLE 1 Preparation of 3-Ketotetra~luOrOglutaroyl Fluoride CH OCF CF2COOCH + SO --- ~ FOCCF2COOCH3 ~ C~30S02F
1* 4 ~ ~ 2 CH3OCF2CF2COCF2CF2OCH3 + 2 SO3 3 O=C(CF2COF)2 ~ CH3OSO2F
2** 3 * methyl 2,2,3,3-tetrafluoro-3-methoxy propionate ** bis~2-methoxytetra~luoroethyl) ketone A mixture (200 g, 1.20 equivalents of ~ (65~) and 2 (35~) above prepared by the reaction of tetra~
fluoroethylene with dimethyl carbonate was added dropwise lS with stirring to 8Q ml (1.91 mQl) gf sulfur trioxide in a pot attached to a still. The rate of addition was controlled to maintain a gentle reflux and when complete, the pot was heated to distill the contents. There was collected: 27 g (50~) of 3, b.p. 54 and 77 g ~70%) of

4, b.p. 82. Compound 3 codistilled with a little SO3 and 4 with about an equal amount of the by-product methyl fluoxosulfate. These contaminants were removed by passing the mix~ure over çodium fluoride pellets at 400~1 to 5 mm.
Compound 3 absorbed in the infrared at 1900 cm 1 (C=O). The 19F NMR spec~rum was obtained with a Varian* A56/60 spectrometer operating at 56~4 MHz;
chemical shifts are in ppm down~iel~ from CFC13 as internal standard: 20.3 ppm (multiplet, 2F) and -113.8 (multipletl 4F). Elemental analysis was consistent with the formula C5F6O3.

* denotes tra~e mark ,.

~17~6~

XAMPLE ~
Preparation of 3-Ketotetrafluoroglutaroyl Fluoride 3 2 2 2 2CH3+ SO3 ~ o=c(cF2coF)~ ~ 2C~3S2F
---CH30CF2CF2oo2cH3 + SO3 ~ FCCC~2C~X~3 + CH206O~

Surflur trioxide (100 ml, 191 g~ 2.39 mol) was magnetically stirred in a round-bottom flask fitted with a dropping funnel and reflux condenser. A mixture (135 g, 0.858 equivalents of 1 (24~) and 2 (76~)) was added at a rate to maintain a gentle reflux. When addition was complete, the dropping funnel was replaced with a short still head and material boiling up to 80 was collected. This material was then washed with concentrated sulfuric acid to remove excess sulfur trioxide, and then redistilled, b.p.
54, yield, 53 g (67.5~).

Copolymers of 3-Ketotetrafluoroglutaroyl Fluoride _ and Vinylidene Fluoride =
A copolymer having the following ~ormula was prepared:
~CF2COF ~1 _ ~CH2CF2~7.3 t : ~
~CF2COFJ ~
Il A stainless steel shaker tube, dry and oxygen free was charged with a nitrogen purged solution con-sisting of 25 g OC(CF2COF)2 (0.11 molj, 30 ml of 1,1,2-trichlorotrifluoroethane (CI2CFCF2Cl) and 0.3 g perfluoropropionyl peroxide as a 10% solution in ~L~7~)6~7 Cl2CFCF2Cl. After adding 40 g CH2=CF2 (0.67 mol), the closed reactor was shaken at 35C. The temperature suddenly increased to 56C momentarily and the polymerization was resumed at 30-38C for a total of 20 hrs. The product was stirred with boiling water to remove solvent, excess monomers, and to hydrolyze the acid fluoride group to carboxylic acid. The dried product (37 g) was hot pressed at 200C to a trans-parent easily stretched strong film. Elemental analysis was consistent with the above formula.
Neutral equivalent, at 683 and 341 Infrared, strong C=O at 1750 cm strong C-F at 1250-1110 cm OH, 3770 cm l The polymer was very soluble in acetone from which a film w~s cast. The film had these physical properties (6 samples):
Tensile tmax) 1674 + 16 psi Yield Elongation 19%
Modulus, 40, 964 ~ 2353 psi The carbonyl band strength of hot pressed film was 108 absorbency ~/mil.
EXAMP~E 4 .
Copolymer of 3-Ketotetrafluoroglutaroyl ~luoride and Ethylene As in Example 3, a shaker tube was charged with 14 g OC(CF2COF)2 and 0.3 g ~enzoyl peroxide. The mixture was copolymerized with ethylene at 85C under 300 atm ethylene pressure for 2 hours and und~r 500 atm ethylene pressure for 7 hours. The total ethylene pressure drop during polymerization was 40 atm. The product was treated with boiling water for 2 hours to hydrolyze acid fluoride ~unctions and dried at 110C
und~r 0.5 mm pressure for one houx. The product (4 g) was soluble in aqueous sodium bicarbonate. Neutral 615 ~

equivalent was 153. Elemental analysis was con~
~istent with the formula:
f CF2C02H ~
- ~CH2CH2~3,5 t OC - -1 ~
CF2C02~I ~
n An infrared spectrum of a film hot pressed between NaCl plates, had the following absorptions in keeping with the above structure:
St~ong b~ad OH ~fo~ CO2H? a~ 323~-3125 c~ 1 ~txong C-~ 1725 c~-l C-F and C;O 1250-1150 cm 1 C=O at 1725 cm 1 ~ EXAMPLE 5 Copolymer of 3-Ketotetrafluoroglutaroyl Fluoride and Tetrafluoroethylene A shaker tube was ch~rged with 25 g (0~11 mole) oCtCF2CoF~2, 0~3 g perfluoropropionyl peroxide and 40 g t0.4 mol~ tetrafluoroethylene. Polymerization was exothermic and the temperature rose to 53C where the pressure was 192 psi; when cooled to 35C, the pressure dropped to 150 psi; after 35 minutes the pressure was 60 psi, and after a ~urther 9 houxs the pressure had declined to 21 psi. The air dried product was ~readed with boiling water ~or 3 hours to hydrolyze acid fluoxide functions, and dried at 110C under 0.5 ~m for 3 hours; 36 g. ~ translucent film pressed at 100C (pol~mer was not fused) had, in addition to C-F
30 infrared absorption, broad OH of a COOH group a~ 3100-3700 cm 1 and C=O band at 1780 cm 1 equal_to 7.6 absorbency ~/mil.

~.~l'7~
1~

Copolymer of 1,5~Dimethyl-3-Ketotetrafluoroglutarate and Vinylidene Fluoride ~CF 2COF~ CH OH ~CF 2CO2CH3~1 - tCH2CF2~ OC ~ 3 _~ ~CH2CP 2~ OC I _ j~F2COFJ n _ \CF2CO2CH3J n The proceduxe described in Example 3 was followed usi~g 22 5 of OC(C~2COF]2~ 0,15 g of per fluDropropionyl peroxide and 50 ml of C12CFCF2Cl as solvent~ The mixture was heated at 35C for 17 hxs under a pressure of vinylidene fluoride; initial pressure wa~ 165 psi; final pressure 120 psi, A portion of the polyme~ic product was ~teeped in 10~ ml of met~nol for 2 d~ys at room tem~e~ature~ An e~thermic react~on occurred with liberation of HF. The polymer product was ~iltered and dried at 110C under vacuum (0.5 m~
Hg) for 3 hrs, Hot pressing at 190C gave a very strong, sli~tly elastomexic fllm. IR; v. weak band at 3650 cm tcarboxyl -OH); ~trong, single caxbonyl ~and at 1770 cm 1, Copolymers o~ 1,5 dime~hyl-3-ketotetra-fluoroslutara~e and vinylldene fluoride ca~ also be prepared by directly polymer.izing the~e two monomers ~5 under similar conditions. Copolymers obtained directly or by means of esterification of the acid halide can be further reacted if desired,for example,hydrolyzed to acid groups, and con~erted to salt groups--see Example 11, EXA~PLE 7 A portion of the vinylidene fluoride~3-keto-glutaroyl fluoride copolymer prepared in Example 6 was steeped in ethylene glycol at 60C for 3 hrs, An exo~hermic reac~ion occurred with liberation o~ HF.
The polymer o~tained after filtering and drying as in . . . .
1~

~1 79687 Example 6 would not melt flow, indicating a cxoss-linked structure resulting rom glycolate formation of the type:
CP2C02C~2 CF2co2fH2 C~2C02CH2 ' I
- C--O

I

Copolymer of 3-Ketotetrafluoroglutaroyl Fluoride, - Te~rafluoroethYle-ne and Ethylene , ' ~ CF2C ~
~CF2C 2~cH2-cH2ty ~o-c- t--\ C~2COFJ n The procedure of Example 3 was repeated usins 4 g of OC~C~2COF)2, 0,2 g of perfluoropropionyl peroxide, 40 g of tetrafluoroethylene, 11 g o~ ethylene and 50 ml of Cl?CFCF2Cl a~ solvent~ Polymerization was continued ~5 or 10 hours at 35-42C; initial pressure was 3.5 psi, final pressure 78 psi. The pol~mer product was hydrolyzed in boiling water for 3 hours to corl~ert COF groups to -COOH, and dried, Yield, 42 g. A
film, pressed as in ~xample 3, was brittle. IR:
strong absorption ~t 2800-3500 cm l ~O~ from -COOH);
C-O absorbency 23%/mil.

~ ..r~6~

. EXAMPL~ 9 Copolymer of 3-Ketotetrafluoroglutaroyl Fluoride, Tetrafluoroethylene and ~inylidene Fluoride ~ CF2CF2~ ~CH2 CF

The procedure o~ Example 3 was repeated using 22 g of OC(CF2COF)2, 0.1 g of perfluoropropionyl per-10 oxide, 25 g of tetrafluoroethylene, 16 g o vinylidene fluoride and 40 ml of C12CFCF2Cl as solvent, Polymeri-zation was continued for 10 hours at 35-40C; initial pressure ~s 242 psi, final press~re 40 psi. ~fter hydrolysis in boilin~ water and drying 'yield 43 g~, 15 a pressed film was tough, IR: C=O absorbency 52%/mil.
Inherent viscosity of the hydrolyzed polymer in acetone was 2,37.
EX~LE l~
Copolymer of 3 Ketotetrafluoroglutaroyl Fluoride, Hexafluoropropylene -and Vinylidene Fluoride ~CF 2COF~
~2 CF ~x ~CH2-CF2t~ toC - )- _ CF3 ~C~2COF.J ~
The procedure of Example 4 w~s repeated using 22 g of OCtCF2COF)2, 150 g o~ hexafluoropropene, 26 g of ~inylidene ~luoride~ 0,2 g of perfluoropropionyl peroxide and 150 ml of Cl2CFCF2Cl as solvent~
Polymerization time, 9 hours at 35C. Initial pressure: 13~ psi; final pressure: 82 psi, ~fter hydrolysis in boiling water and drying, a pressed film was rubbery. Yield 57 g~ IR: strong absorption at 2900-3500 cm l (OH from -COOH); C-O absorbency 30%/mil.

EXAMPLE ll Copol~mer of 3-Ketotetrafluoroglutaric acid (zinc salt) and Vinylidene Fluoride 20 g of 3-ketotetrafluoroglutaric acid/
vinylidene fluoride copolymer having neutral equivalent of 1470 and an inherent viscosity in acetone of 0.653 was dissolved at 40C in 300 ml of acetone. To the stirred, filtered solution at 25C, a solution of 2 g of zinc acetate Zn(O2CCH3)2-2H2O in 40 ml o~ methanol was added. The solution viscosity increased from water-Iike to that of mineral oil. The solvent was removed by vacuum evaporation and dried at 100C;
yield, 15.3 g.
The product was swollen by acetone but not dissolved. A sample was pressed at 190C to give a to~gh, ~lexible ilm that after being drawn to four times its length, recovered to a three-fold extension with no further shrinkage. The IR spectrum showed the following differences ~rom that obtained before treatment with zinc ~cetate, T~ carbonyl band shifted to 1690 cm 1 and a new, broad peak ~as present at 1579 to 1590 cm 1, The sharp OH peak at 3650 cm 1 had disappeared ~nd the 3150 cm 1 peak was weaker, Another sample was heated at 190C ~or 2 ~inutes~ ~en pressed at 1000 psi for 1 minute into yellow-coloxed test bars and tested in duplicate.
Tensile Initial Elongation Strenyth Modulus (break) (yield)

5~si) _ (%) (%) __ Base polymer 3590 131,000 24 17 3698 159,000 3~ i8 Zn salt 3431 126,000314 11 3505 112,000172 1 ~7~87 Copolymer of 3-Ketotetrafluoroglutaric acid (anilide), Vlnylidene Fluoride a-nd ~etrafluoroethylene A copolymer in the acid fluoride form was prepared as described in Example 9, using 44 g o~
OC(CF2COF)2, 0.2 g of perfluoropropionyl peroxide, 50 g of ~inylidenefluoride, 40 g of tetrafluoroethylene and lO0 ml of Cl2CFCF2Cl as solvent. The mixture was polymerized at 35C for 8 hours. The product (35 g) was washed with Cl~CFCF2Cl to remove unreacted ketone, then suspended in 25 ml C12CFCF2Cl. 10 g of aniline was added and the mixture was stored overnight. The pale yellow mixture was filtered, washed with C12CFCF2Cl, then water, and dried. A solution of the product in acetone was ~iltered; the polymer was reprecipitated by slow addition of the solution to cyclohexane. The product was dried at 110C and 0.5 mm pressure for 2 hours (yield/ 3 g), and pressed at 190C to give a strong, flexible, cold-drawable film 20 that creased without cracking. Its IR spectrum had NH bands at 3420 cm l and 1610 cm 1, a strong C=O
band at 1725 cm 1 (22 absorbency ~jmil). Anal:
Nitrogen, 0.58, 0.59~, corresponding to 3.8% by weight of C6H5N- in the polymer.
This application is a division o~ copending Canadian Application Serial No. 364,624, filed November 13, 1980 .0 , ,

Claims (3)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. The compound having the formula:
O=C(CF2COX)2 where X is selected from the class consisting of F and Cl.

2. A process for the preparation of the compound O=C(CF2COF)2 which comprises reacting bis(2-methoxytetrafluoroethyl) ketone with sulfur trioxide.

3. The process of Claim 2 in which the bis(2-methoxytetrafluoroethyl) ketone is contained in a mixture with methyl 2,2,3,3-tetrafluoro-3-methoxy propionate.