JPH02262528A - Production of bromine-containing perfluoro compound - Google Patents

Abstract

PURPOSE:To economically obtain the subject substance useful as a synthetic intermediate for surfactants, agricultural chemicals, medicaments, etc., X-ray contrast media, fluorocarbon-based fire extinguishers, etc., in high yield by thermally reacting a perfluorocarboxylic acid fluoride with LiBr. CONSTITUTION:A compound expressed by formula I (Rf is perfluorohydrocarbon group; (n) is 1-3) is reacted with LiBr at >=300 deg.C (preferably 320 to 400 deg.C) to afford a compound expressed by formula II ((m) is 1-3 and (n)>=(m)). The LiBr is preferably anhydrous and the amount thereof used is selected from the range of 1.2 to 1.5mol if the compound expressed by formula I is a monobasic acid, 2.5 to 3.0mol in the case of a dibasic acid and 3.5 to 4.0mol in the case of a tribasic acid. In the case of the dibasic and tribasic acids, only a part of the fluorocarbonyl groups can be substituted with Br by selecting the molar ratio to the LiBr. The compounds expressed by formula I are readily available and the above-mentioned method is advantageous.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a novel method for producing bromine-containing perfluorocompounds. More specifically, the present invention provides fluorine-containing alkyl bromides useful as synthetic intermediates for fluorine-containing products such as surfactants, agricultural chemicals, and pharmaceuticals, or as X-ray contrast agents and fluorocarbon fire extinguishing agents. The present invention relates to an economically advantageous manufacturing method with high yield using readily available raw materials.

Background of the Invention In recent years, perfluoroalkyl bromides have attracted attention as synthetic intermediates and seating materials for various fluorine-containing products.
For example, as a synthetic intermediate for surfactants, agricultural chemicals, pharmaceuticals, etc., or as fluorocarbon fire extinguishers, X-ray contrast agents, etc.
Widely used.

Conventionally, the method for producing perfluoroalkyl bromide involves mixing perfluorocarboxylic acid silver salt with bromine in a sealed tube.
[Journal of American Chemical Society (J, Amer.

Chem, 5oc) J, Volume 73, Page 4016 (
1951), Volume 74, Page 849 (195
2 years)], a method of reacting perfluorocarboxylic acid anhydride with bromine in a carbon tube filled with activated carbon (U.S. Pat. No. 2)
, 704, 776) and the like are known as methods using perfluorocarboxylic acids as raw materials.

However, in the method using such perfluorocarboxylic acid as a raw material, as a pre-reaction step,
This method requires a complicated step of converting perfluorocarboxylic acid into a metal salt or acid anhydride, which is extremely disadvantageous for industrial implementation.

Other methods include, for example, a method in which perfluoroalkyl sulfur pentafluoride is reacted with bromine in an alumina tube containing nickel chips at a high temperature of about 500°C (U.S. Pat. No. 3,456,024); A method of reacting an alkyl iosite with bromine in the presence of peroxide has been proposed (Japanese Unexamined Patent Publication Nos. 60-184033 and 61-233637).
These methods are not necessarily satisfactory either because the raw materials are not easily available or the yield is not high enough.

On the other hand, perfluorocarboxylic acid fluorides are e.g.
It is also known that it can be easily produced by electrolytic fluorination reaction of the corresponding perfluorocarboxylic acid chloride.

Therefore, when producing perfluoroalkyl bromide, if perfluorocarboxylic acid fluoride can be used as it is as a raw material, the process can be simplified and it is extremely advantageous.

Problems to be Solved by the Invention Under these circumstances, the present invention aims to obtain bromine-containing perfluoro compounds useful as synthetic intermediates for various fluorine-containing compounds from easily available perfluorocarboxylic acid fluorides. This was done for the purpose of providing a method for producing with high yield through simple operations.

Means for Solving the Problems In order to achieve the above object, the present inventors have conducted extensive research and found that a bromine-containing perfluoro compound can be produced in good yield by subjecting perfluorocarboxylic acid fluoride to a heating reaction with lithium bromide. The present inventors have found that the object can be achieved, and have completed the present invention based on this knowledge.

That is, the present invention provides - formula % formula % (1) (Rf in the formula is a perfluorohydrocarbon group, and n is 1
is an integer of 3 to 3) and lithium bromide are heated to react at a temperature of 300°C or higher. and m is 1 to 3
The present invention provides a method for producing a bromine-containing perfluoro compound represented by:

The present invention will be explained in detail below.

In the method of the present invention, perfluorocarboxylic acid fluoride represented by the above formula (I) is used as a raw material. Rf in formula (I) is a perfluorohydrocarbon group, that is, a hydrocarbon group in which all hydrogen atoms are substituted with fluorine atoms, and this hydrocarbon has 1 carbon number.
5 or less is preferable. In addition, this hydrocarbon group may optionally bond oxygen or hexavalent sulfur (-3F, --5FS) to a carbon other than chlorine or σ-carbon as a petro atom. Further, it may be linear, branched, or cyclic, and may contain a heterocycle.

Specific examples of such perfluorocarboxylic acid fluorides include trifluoroacetyl fluoride, chlorodifluoroacetyl fluoride, perfluoroprobionyl fluoride, perfluoro-n-butyl fluoride,
perfluoro-n-cabroyl fluoride, perfluoro-n-cabroyl fluoride, perfluoro-3-proboxybrohionyl fluoride, perfluoromalonyl fluoride, perfluorosuccinoyl fluoride, perfluoroglutaryl fluoride, Perfluorocyclohexylcarbonyl fluoride, perfluoro(1,4
-di(fluorocarbonyl)cyclohexane], perfluoro(1,3,5-)su(fluorocarbonyl)cyclohexane], and the like.

On the other hand, in the method of the present invention, lithium bromide used as another raw material may be anhydrous or hydrated, but the yield and purity of the obtained bromine-containing perfluoro compound are Therefore, the anhydride is preferable.

When replacing all of the fluorocarbonyl groups with bromine atoms, the amount of lithium bromide to be used is desirably slightly stoichiometrically excessive with respect to the fluorocarbonyl group, for example, 1 mole of perfluorocarboxylic acid fluoride. -1.2 to 1.5 mol for basic acid fluoride, 2.5 to 3.0 mol for dibasic acid fluoride, and 3.5 to 4 mol for tribasic acid fluoride. Advantageously, it is chosen in the range .0 mol.

Furthermore, when dibasic or tribasic perfluorocarboxylic acid fluoride is used as a raw material, by selecting the molar ratio of the raw material carboxylic acid fluoride and lithium bromide, only some of the fluorocarbonyl groups can be removed. It is possible to convert with bromine atom.

For example, as shown in the following formula, from bifunctional perfluorodicarboxylic acid fluoride (I[[), perfluoro(
ω, ω-dibromoalkane) (V), perfluoro(ω-promoalkanoyl fluoride) (■)
It is possible to manufacture

(V) In the method of the present invention, the reaction temperature is usually 300 to 50
0°C5, preferably selected in the range of 320 to 400°C. If this temperature is less than 300°C, the conversion rate is too low to be practical, and if it exceeds 500°C, side reactions such as decomposition will occur, which is not preferred. The reaction time depends on the reaction temperature and cannot be determined unconditionally, but it is generally
It is about seconds to 24 hours.

Furthermore, this reaction can be carried out under reduced pressure, atmospheric pressure, or increased pressure, and can be carried out either batchwise or continuously. In addition, in the reaction, depending on the reaction form, an inert gas such as nitrogen, helium, or argon, or an inert liquid such as perfluorocarbon that does not react with lithium bromide may be used as a diluting agent. In this case, the dilution ratio is preferably 100 times or less.

When the reaction is carried out in a continuous manner, the raw material perfluorocarboxylic acid fluoride is continuously supplied to a bed filled with lithium bromide maintained at a predetermined temperature, and the corresponding bromine-containing perfluoride is easily reacted. compound can be obtained. There are no particular restrictions on the material of the reaction vessel, but stainless steel or Hastelloy is usually used. Further, there is no particular restriction on the type of the packed bed, and any type such as a fixed bed, moving bed, or fluidized bed can be used.

Effects of the Invention According to the method of the present invention, a compatible fluorine-containing alkyl bromide can be produced in high yield by using an easily available fluorine-containing carboxylic acid fluoride and subjecting it to a thermal reaction with lithium bromide. Obtainable. This product is useful as a synthetic intermediate for fluorine-containing products such as surfactants, agricultural chemicals, and pharmaceuticals, and as an X-ray contrast agent.

Examples Next, the present invention will be explained in more detail with reference to examples.
The present invention is not limited in any way by these examples.

Example 1 In a Pyrex thick-walled ampoule V (inner diameter 14 mm, length 270 mm) containing 0.68 g of anhydrous lithium bromide,
15. Trifluoroacetyl bromide was added at 1 atm by vacuum line operation. After weighing and charging OmQ (0.67 mmol), it was reacted in an electric furnace at 330°C for 5 hours.

After the reaction is complete, the product is cooled in a liquid nitrogen and dry ice-ethanol bath and purified by fractional condensation using a trap. 14. From a cold trap at -196°C.
3 mC (0.64 mmol) of product gas (1 atm) was obtained. When this gas was analyzed by F-NMR and IR, it was found to be a mixture of trifluoromethane bromide and trifluoroacetyl bromide (molar ratio 32:68).

The yield of trifluoromethane bromide was 31 mol % based on the charged trifluoroacetyl bromide.

Example 2 The reaction was carried out in the same manner as in Example 1, except that pentafluoropropionyl bromide was used as the raw material.

That is, 0.82 g of anhydrous lithium bromide and 0.76 mmol of pentafluoropropionyl bromide were reacted in a Pyrex ampoule at 330°C for 15 hours to form I6
．． A product gas of 4rRQ (0.73 mmol) was obtained.

When this was analyzed by F-NMR and IR in the same manner as in Example 1, it was found that it was a mixture of bromopentafluoroethane and pentafluoropropionyl bromide (molar ratio 37:63).
). The yield of bromopentafluoroethane was 36 mol % based on the starting materials.

Implementation side 3 Perfluoro(3-(n-propoxy)propionyl fluoride) as perfluorocarboxylic acid fluoride]
The reaction was carried out almost in the same manner as in Example 1, except that .

That is, perfluoro[:3-(n-propoxy)propionyl fluoride) 1.48i+(4
, 46 mmol), and the reaction mixture was heated at 350°
The reaction was carried out at C for 4 hours. After the reaction was completed, the ampoule was cooled with liquid nitrogen to remove volatile gas (carbon monoxide as soil). The contents were then warmed to room temperature, transferred via vacuum line operation, and weighed to yield 1.539 g of a clear light orange liquid.

This substance is subjected to gas chromatography [carrier gas:
He, liquid phase: 1,6-bis(1,1,1,2-trihydroperfluorododecyloxy)hexane, carrier:
60-80) n'/j, '7 omo'/-buP
When analyzed by AW), IR1'F-NMR, Mass, etc., perfluoro(2-bromoethyl-n
-propyl ether) 1.419 were obtained. The yield was 87 mol% based on the supplied raw materials.

The compound is a transparent liquid at room temperature, and its physicochemical properties are boiling point 68.5-69.5°CSn', '1.2
g23,d"1.8066.

Example 4 The reaction was carried out in the same manner as in Example 3, except that perfluoroglutaryl fluoride, a dibasic acid, was used as the heptad-containing carboxylic acid fluoride, and a 75mα stainless steel reaction tube was used as the reaction vessel. I went.

That is, perfluoroglutaryl fluoride 2.03
When 0.709 g (8.32 mmol) of anhydrous lithium bromide (8.20 mmol) was reacted at 350°C for 5 and a half hours, 2.09 g of a transparent reddish-purple liquid was produced which fumed in the air. Obtained. This product was analyzed in the same manner as in Example 3 [gas chromatography: column used: liquid phase: KeLF #90, carrier: 60-80 mesh chromosorb PAW], and it was found that perfluoro(3-promobutyryl fluoride) 0.7h and perfluoro(l,3
-dibromopropane) 0.43 g was obtained. Their yield is 45 mol% each based on the consumed raw material.
and 21 mol%.

Perfluoro(3-promobutyryl fluorite) has a boiling point of 132 physicochemical properties as a methyl ester.
．． 5-133.5°C, n;'1.3536, d;01
．． 7690", and its infrared absorption spectrum characteristic absorption is based on Go!Je is y (C-0) 1787
cm-'.

Example 5 Example 4 except that the molar ratio of raw materials perfluoroglutaryl fluoride and anhydrous lithium bromide was changed to 1:2.
The reaction was carried out in the same manner.

That is, perfluoroglutaryl fluoride 1.00
When a reaction mixture of 9 (4,10 mmol) and 0.76 g (8,75 mmol) of anhydrous lithium bromide, which is approximately twice the molar amount, was reacted in a Pyrex ampoule at 350°C for 15 hours, a pale transparent reddish-purple liquid 1 was obtained. .17g was obtained. When this product was analyzed in the same manner as in Example 4,
Perfluoro(1,3-dibromopropane) 1.00
g was obtained. The yield was 79 mol% based on the charged raw materials.

The compound is a clear liquid at room temperature and has a boiling point of 71.5-
It had physicochemical properties of 72.5°C, n1o1.3582, d''2.1334.

Claims (1)

[Claims] 1 General formula ▲ Numerical formula, chemical formula, table, etc. ▼ (In the formula, Rf is a perfluorohydrocarbon group, and n is 1
There are general formulas ▲ mathematical formulas, chemical formulas, tables, etc. ▼ (formula Rf and n have the same meanings as above, and m is 1 to 3.
an integer of n≧m).