AU641049B2

AU641049B2 - Synthesis of fluorinated dimethyl ethers

Info

Publication number: AU641049B2
Application number: AU84870/91A
Authority: AU
Inventors: Gerald J. O'neill
Original assignee: Hampshire Chemical Corp
Current assignee: Hampshire Chemical Corp
Priority date: 1990-10-02
Filing date: 1991-10-01
Publication date: 1993-09-09
Anticipated expiration: 2011-10-01
Also published as: KR100196480B1; MY110269A; GB2248617A; GB9120912D0; CA2052553A1; AU8487091A; KR920007966A; GB2248617B; ZA917855B

Description

AUSTRALIA

Patent Act CO0M PL E TE S PE C

(ORIGINAL)

64at04 FUCATIO4 Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority: Related Art: es..

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Names(s) of Applicant(s): Actual Inventor(s): Gerald J. O'Neill I4 0R

A

SEC.I~

4%p732 Our .4ddress for service is: PHILLIPS ORMONDE FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street MELBOURVE, Australia 3000 Complete Specification for the invention entitled: SYNTHESIS OF FLUORINATED DIMETHYL ETHERS The fcllowing statement i9 a full description of this invention, including the best method of performing it known to applicant(s): 1 080 4N b SYNTHESIS OF FLUORINATED DIMETHYL ETHERS BACKGROUND OF THE INVENTION Field of the Invention This invention relates to a process for the synthesis of fluorinated dimethyl ethers which have utility as refrigerants, as blowing agents, etc.

Bis(difluoromethyl)ether has been prepared previously by chlorination of dimethyl ether followed by isolation and fluorination of bis(dichloromathyl)ether.

The chlorination step gave a complex mixture of chlorinated dimethyl ethers some of which were unstable, e.g. to distillation, from which bis(dichloromethyl)ether was separated. Two of the ethers in the mixture, chloromethyl methyl ether and bis-(chloromethyl)ether, are potent carcinogens.

SUMMARY OF THE INVENTION 0See

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0S -7 Nr C invention to provide a process for synthesis of fluorinated dimethyl ethers which does not roduce 25 carcinogens as intermediates.

Another object of the present in tion is to provide a process for synthesis of fl rinated dimethyl ethers wherein the various require separations may be effected by distillation without st of yield and danger of explosion due to marked stability of the various intermediates.

The unstable com mixture of chlorinated ethers, some of which are arcinogens, in accordance with the prior art, is oided in the present invention by 35 employing m 1 difluoromethyl ether as a starting material. h e methyl difluoromethyl ether is chlorinated to giv chlorinated reaction mixture including at least on 6mpound of the formula CHHOCH, wCl, wherein z 3 The present invention provides a process for the preparation of fluorinated dimethyl ethers of the formula CF2HOCCx FyH3_(x+y wherein x and y are each independently 0, 1, 2 or 3 and wherein the total x+y is 2 or 3, said process including: chlorinating CF 2

HOCH

3 by reacting said

CF

2

HOCH

3 with chlorine gas to form a chlorinated admixture containing at least one compound of the formula

CF

2 HOCH3 _C1 wherein Z is 1, 2 or 3; and fluorinating said one compound of the formula

CF

2 HOCH3-ZC1 z to obtain a fluorinated adrixtlre containing at least one compound of said formula CF HOCC1 F H(x+y In a preferred aspect of the present invention there is provided a process for the preparation of fluorinated dimethyl ethers as described above which additionally includes reacting

CHF

2 C1 with an alkali metal methoxide in solvent solution to form said CHF 2

OCH

3 Accordingly, in an aspect of the present invention there is provided a process for synthesis of fluorinated dimethyl ethers which does not produce carcinogens as intermediates.

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Another aspect of the present invention provides a process for synthesis of fluorinated dimethyl ethers wherein the various required separations may be effected by distillation without lost of yield and danger of e.plosion due to a marked S instability of the various intermediates.

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io The unstable complex mixture of chlorinated ethers, some of which are carcinogens, in accordance with the prior art, is *ii avoided in the present invention by employing methyl difluoromethyl ether as a starting material. The methyl difluoromethyl ether is chlorinated to give a chlorinated reaction mixture including at least one compound of the formula CH 2

HOCH

3 zC1 z wherein z 39 -lbis 1, 2 or 3, which compound can readily be separated from the chlorinated reaction mixture. The chlorination of rethyldifluoromethyl ether can form only three derivatives, i.e. z=l, z=2 and z=3. The dichloromethyl difluoromethyl ether can readily be separated from the chlorinated reaction mixture and is then fluorinated, with or without such separation, to form the bis(difluoromethyl)ether. CF 2 H0CC1 3 may also be separated from the chlorination reaction product and fluorinated. Alternatively, the chlorination reaction product itself may be fluorinated (without prior separation) as follows: CF HOCH C1 CF> HOCH F CF HOCHC1 2 F2HOHl CF 2 HOCHF 2

(I)

(II)

Soo CFF2HHCCC12 CF 2 HOCC1 CF 2 HOCC1F 2 All of the above would find utility as refrigerants, especially mono fluo rornethyl difluoromethyl ether and (II) bis (dif luoromethyl) ether, which are considered to be sustitutes for R-11 and R-114 refrigerants, respectively.

The chlorination and fluorination steps of the present invention may be represented as follows: Cl 2 CHF 2 CH 3 CF 2 HOCH 3 -zC1 where z=l, 2 or 3

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5 S S SS

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SS

CF

2 HOCH 3 C1 2 CF 2 HOCC x F yH 3 where: x=l, 2 or 3 y=l, 2 or 3 x+y= 2 or- CF 2 HOCH 3-z Cl F 2 HOCC1 x F yH 3(y)where: x 0,-1,2 or) y 1, 2 or 3 x+y =2 or 3 3 -2a DESCRIPTION OF THE PREFERRED EMBODIMENTS The methyl difluoromethyl ether which is regarded as the starting material for the process of the present invention is a known compound which may be prepared in the manner reported by Hine and Porter in their article published in the Journal of the American Chemical Society, See "Methylene derivatives as intermediates in polar reactions. VIII. Difluoromethylene in the reaction of chlorodifluoromethane with sodium methoxide." Jack Hine and John J. Porter, J. Am. Chem. Soc. 79, 5493-6 (1957), the teachings of which are incorporated herein by reference. In their article Hine and Porter describe the production of difluoromethyl methyl ether (CH3OCHF 2 by reaction of sodium methoxide NaOMe with chlorodifluoromethane (ClF2CH), which reaction may be represented as follows: CF2HCi CHO3Na CFHOCH 3 2 3 2 3

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0 Briefly, the method involves forming an alcohol solution of sodium methoxide and bubbling the chlorodifluoromethane slowly through the reaction mixture to obtain the methyldifluoromethyl ether as a residue in the reaction mixture.

25 The starting ether, CF 2

OCH

3 might also be prepared by first reacting NaOH with CH3OH, in effect making CH3ONa, and then reacting it with CF 2 HC1.

However, water is also formed in the NaOH/CH30H reaction and the effect the water would have on the subsequent reaction to form CF 2

HOCH

3 is presently unknown.

In accordance with the present invention, methyldifluoromethyl ether is chlorinated as follows:

CF

2

HOCH

3

CF

2 HOCH3Z Cl z where z= 1, 2 or 3 It has been found that the CF 2

HOCH

3 may suitably be chlorinated by liquefying the CF 2

HOCH

3 and reacting it with chlorine gas while irradiating with a source of -3-

S.

S

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5* visible light. The chlorination of CF 2

HOCH

3 can form only three derivatives, from which CF 2 HOCHC1 2 and/or

CF

2 HOCC1 3 can be readily separated prior to fluorination or the reaction mixture can be fluorinated without separation to give an admixture of CF 2 HOCFC1 2 CF2HOCF 2 Cl CF 2

HOCH

2 F, CF 2 HOCFHC1 and

CF

2

HOCF

2 H. All separations may be effected by fractional distillation.

One method found suitable for the fluorination of the chlorination reaction product involves reaction of the halogenated dimethylether or ethers with antimony trifluoride. The reaction may be represented as follows: SbF 3

CHF

2 OCHC1 2 CHF 2

OCHF

2 On an industrial scale the antimony trifluoride reaction can be carried out in a continuous mode by a continuous regeneration of the catalyst with HF. This is done by using a mixture of SbF 3 and chlorine to give the pentavalent salt SbF 3 Cl 2 or on a small scale it can be done by using a mixture of SbF 3 and SbCl 5 as in example 2 which follows. More commonly, antimony pentachloride alone is used as follows:

HF

S 25 SbCl 5 SbC5_yFy yHC1

CF

2

HOCH

3 xCl SbCl yFy CF HOCClxFyH(x+y SbCl The mixed salt catalyst, likewise, may be continuously regenerated by the addition of HF.

•In n alternative fluorination procedure the chlorinated reaction product is reacted with anhydrous hydrogen fluoride which reaction may be represented as follows: 35 CF 2 HOCC1 3 HF CF 2

HOCFCJ

2

CF

2

HOCF

2 C1 Utilizing the above reaction with hydrogen fluoride the present inventor has obtained a yield as high as 78% 39 -4- CF 2 HOCF 2 C with a small amount of CF 2 HOCFC 2 This was an unexpected result since HF does not normally replace a halogen such as chlorine, except perhaps at very high temperatures, but instead fluorinates by continuous regeneration of a fluorinating agent such as SbF 3 or SbF 3 Cl 2 Apparently, the difluoromethoxy group activates the chlorine on the alpha-carbon atom allowing it to react readily with HF.

The present invention will now be further illustrated by the following examples.

Example 1 a) Preparation of CF 2 HOCH 3 Methanol (1000 mls) was placed in a three-liter, three-necked, round-bottomed flask fitted with a magnetic stirrer, thermometer, gas dispersion tube, condenser cooled to -78 0 C and connected to a trap also cooled to -78 0 C. Sodium methoxide (2215 g) was added slowly while stirring the mixture. The temperature of the reaction flask was adjusted to 45-55C C and maintained in that range during the reaction. Chlorodifluoromethane (569 g) was bubbled slowly through the reaction mixture over a period Sao* a 6 a::e0 of 6 1/4 hours. The material recovered from the trap was 000warmed to -26 0 C for about 15 minutes to remove excess *CHF 2 Cl. The weight of residual material was 250.6 g.

GC analysis of the residue showed it to contain 85.4% CFHC a 65% yield, based on CH ONa.

b) Chlorination of CF 2 HOCH 3 Apparatus consisted of a three-necked, 250-rnl roundbottomed flask fitted with a thermometer, a gas dispersion tube, an air condenser connected in series with a dewar condenser, a cold trap (-780C) and a HCl scrubber.

The dewar condenser was cooled to about -30*C with dry ice/methanol and the reaction flask cooled in a similar fashion to -15 0 C. The apparatus was flushed with "469: 35 nitrogen for 15 minutes to remove oxygen. A mixture of .CF 2 HOCH 3 and CHF 2 C (total weight 125.9 g and a .containing 65% CF 2 HOCH 3 a s obtained from the preparation in section was condensed into the flask 39 and chlorine gas (140 g) added over a period of 1 3/4 hour while irradiating the flask with a 300-watt sunlamp. The material recovered from the cold trap (76 g) contained 90.5% CF 2 HOCHC1 2 a yield of 37%.

c) Fluorination of CHF20CHC1 2 Antimony trifluoride (9.8 g) and CF 2 HOCHC1 2 (24.9 g) were placed in a 50 ml, 3-necked, round-bottomed flask fitted with a thermometer, a magnetic stirrer and a water condenser connected in series with a cold trap. The mixture was stirred for 1/2 hour then heated to 57 0 C for minutes.

GC analysis of the material recovered from the cold trap showed it to contain 64.2% CHF 2

OCHF

2 a yield of 62.5%, The other product of the reaction, CHF 2 OCHFC1, accounted for 26.5% of the product mixture.

Example 2 CF HOCH 3 (166 was chlorinated, as in Example 1 section to give 98.8 g of product containing 9.4% CHF 2

OCIH

2 29.1% CF2HOCHC1 2 and 51.1% CHF20CC1 3 A portion (13.6 g) of this mixture was then fluorinated in an apparatus similar to that described in section of Example 1. SbF 3 (7,4 g) and SbCl 5 (0.75 g) were placed in the reaction flask and the chlorinated product slowly added to the stirred mixture.

25 The temperature of the reaction system rose to 44°C without the application of heat. C( analysis of the recovered product (9.2 g) showed it to consist of CF2HOCF2H CF 2

HOCF

2 C1 and

CF

2 HOCFC1 2 (21.89%).

Example 3 alternative fluorination step A sample of chlorinated difluoromethyl ether mixture (25 gm) containing 50% CF 2 HOCC1 3 was placed in a polyethylene flask fitted with an iniet tube for nitrogen as carrier gas, an outlet tube leading to a second 35 polyethylene flask containing NaOH solution followed by a drying tube and a p cooled in Dry Ice/MeOH.

i* An excess of anhydrous hydrogen fluoride was added 39 -6to the chlorinated ether and the mixture stirred with a magnetic stirrer. Heat was not applied, the temperature remaining at about 20 0 C. More hydrogen fluoride was added to the mixture as needed until all the organic material had reacted. The weight of material collected from the cold trap was 9.5 g.

Analysis of the recovered product by GC showed it to consist of 84.3% CF2HOCF 2 Cl, a yield of 78% based on the CF 2 HOCC1 3 content of the chlorinated mixture. A small amount of CF 2 HOCFC12 was also present.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

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Claims

1. A process for the preparation of fluorinated dimethyl ethers of the formula CF 2 HOCCxFyH 3 l wherein x and y are each indlependently 0. 1, 2 or 3 and wherein the total x+y is 2 or 3, said process including: chlorinating CF 2 HOCH 3 by reacting said CF 2 HOCH 3 with chlorine gas to form a chlorinated admixture containing at least one compound of the formula CF 2 HOCH3-zCl z wherein Z is 1, 2 or 3; and fluorinating said one compound of the formula CF 2 HOCH 3 z Cl z to obtain a fluorinated admixture containing at least one compound of said formula F2HOCCIxFyH3-(x+y)

2. A process according to claim 1 wherein the fluorinating Step is conducted in the absence of a catalyst.

3. A process according to either claim 1 or 2 wherein said fluorinating includes reacting said one compound with anhydrous HF.

4. A process according to any one of claims 1 to 3 wherein said fluorinating includes reacting said one compound with antimony trifluoride.

5. A process according to any one of claims 1 to 4 wherein said fluorinatirg includes reacting said one compound with SbCl 5 Y F. 3A ft S S,

6. A process according to any one of claims 1 to wherein said one compound of the formula CF 2 HOCH 3 Cl 3-z2 Z S" is CF 2 HOCHCI 2 and said fluorinated reaction product includes CF 2 HOCF 2 H, CF 2 HOCFC1 and CF 2 HOCF 2 C1. 2°2 2 2n2

7. A process according to any <ne of claims 1 to wherein one compound of the formula CF 2 HOCH 3Cl z is CHF 2 OCHCI 2 and said one compound of the formula l CF 2 HOCCI xyH3(x+y) is CHF 2 OCHF 2 and further A y-8-2 including separating and recovering said CHF 2 OCHF 2 from said fluorinated admixture.

8. A process according to any one of claims 1 to wherein said one compound of the formula CF 2 HOCH 3 Clz is CF 2 HOCC1 3 and said one compound of the formula CF2HOCC1xFyH3-(x+y is CF 2 HOCF 2 Cl and further including separating and recovering said CF 2 HOCF 2 Cl from solution,

9. A process according to claim 7 wherein said fluorinating involves reacting said CF 2 HOCC1 3 with anhydrous HF.

10. A process according to any one of claims 1 to 9 wherein said chlorinating is conducted at a temperature sufficiently low to maintain said CF 2 HOCH 3 in liquid state.

11. A process according to any one of claims 1 to additionally including reacting CHF 2 C1 with an alkali metal methoxide in solvent solution to form said CHF 2 OCH 3

12. A pvocess according to claim 7 wherein an admixture of CF2HOCH 3 and CHF 2 CI is subjected to said chlorinating.

13. A process uccording to either claim 7 or 11 wherein said CF 2 HOCHC a is fluorinated by reaction with antimony trifluoride and said fluorinated reaction product includes CHF2OCHF 2 and CHF 2 OCHFC1. *4

14. A process according to any one of claims 1 to 13 wherein said one compound of the formula CF 2 HOCH ,ZC1 z 3*2 2 is fluorinated by reaction with antimony trifluoride and said 6 antimony trifluoride is regenerated by r, chion with hydrogen fluoride.

C A process according to any one of claims 1 to 14, wherein said one compound of the formula CF2HOCH3-01C z is fluorinated by reaction with an admixture of antimony -9- trifluoride and antimonly pentachioride and saiid admixture of antimony trifluoride and antimony pentachioride is regenerated by reaction with hydrogen fluoride.

16. A process according to claim 1 substantially as hereinbefore described with reference to any one of the Examples. DATED: 6 July 1993 PHILLIPS ORMONDE FITZPATRICK Attorneys for: W R GRACE CC -CONN 3032SbcMc/ jAt- 4 ABSTRACT OF THE DISCLOSURE A novel process is disclosed for the synthesis of fluorinated dimethyl ethers of the formula CFHOCC1,FH,..,.,, wherein X and Y are each independently 0, 1, 2 or 3 and wherein the total X+Y is 2 or 3. The process involves chlorination of methyl difluoromethyl ether to form a chlorinated reaction product, including at least one compound of the formula CF,HOCH,.,C1,, wherein z is 1, 2 or 3, which compound is then fluorinated, with or without separation from the chlorinated reaction product, to give a fluorinated reaction product including the aforementioned fluorinated dimethyl ethers.