Process for purifying 1,1,1,5,5,5-hexafluoroacetylacetone

Abstract

The invention relates to a process for purifying a crude 1,1,1,5,5,5-hexafluoroacetylacetone. This process includes (a) hydrating the crude 1,1,1,5,5,5-hexafluoroacetylacetone to a 1,1,1,5,5,5-hexafluoroacetylacetone hydrate; and (b) dehydrating the 1,1,1,5,5,5-hexafluoroacetylacetone hydrate, thereby obtaining a purified 1,1,1,5,5,5-hexafluoroacetylacetone. Prior to the step (b), the 1,1,1,5,5,5-hexafluoroacetylacetone hydrate may be brought into contact with a poor solvent in which 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate is substantially insoluble. Furthermore, the step (a) may be conducted in a poor solvent in which 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate is substantially insoluble. It is possible by the process to easily obtain 1,1,1,5,5,5-hexafluoroacetylacetone with high purity.

Description

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a process for producing 1,1,1,5,5,5-hexafluoroacetylacetone with high purity, which is useful as an intermediate for producing medicines, agricultural chemicals and electric parts.

[0002] H. Gilman et al., J. Am. Chem. Soc., Vol. 78, pp. 2790-2792 (1956) teaches a process for producing 1,1,1,5,5,5-hexafluoroacetylacetone, which is shown by the following reaction formulas: 1

[0003] A. Henne et al., J. Amer. Chem. Soc., Vol. 69, pp. 1819-1820 (1947) discloses a process for producing anhydrous 1,1,1,5,5,5-hexafluoroacetylacetone by turning a sodium salt of 1,1,1,5,5,5-hexafluoroacetylacetone into a copper chelate compound, then recrystallizing the copper chelate compound, and then removing the copper with hydrogen sulfide.

[0004] R. Haszeldine et al., J. Chem. Soc. London, 1951, pp. 609-612 discloses that a reaction liquid is treated with dilute sulfuric acid and then extracted with ether, and the resulting organic layer is distilled to obtain distillates over the range 36-90° C. It is disclosed therein that the portion of boiling point 85-90° C. appears to be 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate.

[0005] H. Gilman et al., J. Am. Chem. Soc., Vol. 78, pp. 2790-2792 (1956) further discloses the precipitation of 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate by concentrating an organic layer extracted with ether.

[0006] In general, raw materials, including 1,1,1,5,5,5-hexafluoroacetylacetone, for producing medicines, agricultural chemicals and electronic parts are required to have higher purity, as compared with raw materials for other uses.

SUMMARY OF THE INVENTION

[0007] It is therefore an object of the present invention to provide a process for purifying a crude 1,1,1,5,5,5-hexafluoroacetylacetone.

[0008] According to the present invention, there is provided a process for purifying a crude 1,1,1,5,5,5-hexafluoroacetylacetone. This process comprises (a) hydrating said crude 1,1,1,5,5,5-hexafluoroacetylacetone; and (b) dehydrating a product of said hydrating, thereby obtaining a purified 1,1,1,5,5,5-hexafluoroacetylacetone.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] It is possible by the process to easily obtain 1,1,1,5,5,5-hexafluoroacetylacetone with high purity.

[0010] Since 1,1,1,5,5,5-hexafluoroacetylacetone is superior as a solvent or chelating agent, it may contain various impurities. Some of these impurities can be removed or decreased by distillation, but other impurities can not. According to the invention, however, it is possible to highly purify a crude 1,1,1,5,5,5-hexafluoroacetylacetone by removing even such other impurities.

[0011] The raw material of the step (a) in the process, a crude 1,1,1,5,5,5-hexafluoroacetylacetone, is not particularly limited, as long as it contains impurities dissolved or dispersed therein. The impurities may be organic matters, inorganic matters, and/or a combination of these. Their content is not limited, either. If the crude 1,1,1,5,5,5-hexafluoroacetylacetone contains a solid matter as impurities, it is preferable to remove it by filtration. This removal is, however, not necessarily required depending on the treatment conditions of the process.

[0012] The step (a) of the process can be conducted by charging a reaction vessel with 1 part by mole of a crude 1,1,1,5,5,5-hexafluoroacetylacetone and 2 parts by mole or greater (preferably 2 to about 50 parts by moles, more preferably 2 to about 30 parts by mole) of water for hydrolyzing the crude 1,1,1,5,5,5-hexafluoroacetylacetone. According to need, it is possible to add an acid (e.g., sulfuric acid, hydrochloric acid and nitric acid) to the reaction vessel and/or to increase the temperature of the reaction vessel in order to accelerate the hydration. It is estimated that a 1,1,1,5,5,5-hexafluoroacetylacetone hydrate is produced by the step (a). If an excessive amount of water is used in the step (a), the product of the step (a) is obtained in the form of an aqueous solution. In this case, it is possible to extract the product of the step (a) with a solvent in which a 1,1,1,5,5,5-hexafluoroacetylacetone hydrate is soluble, thereby obtaining an organic layer, and then to remove this solvent from the organic layer, thereby obtaining the 1,1,1,5,5,5-hexafluoroacetylacetone hydrate in the form of solid. This hydrate is usually 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate [CF3C(OH)2CH2C(OH)2CF3], but may be another hydrate other than dihydrate or a mixture of these hydrates. The obtained 1,1,1,5,5,5-hexafluoroacetylacetone hydrate may be dried, but the drying is not necessarily required if this hydrate is used as a raw material for producing 1,1,1,5,5,5-hexafluoroacetylacetone (anhydride). Dehydration of the 1,1,1,5,5,5-hexafluoroacetylacetone hydrate leads to the obtainment of 1,1,1,5,5,5-hexafluoroacetylacetone. Furthermore, it is optional to conduct a distillation or contact with a solid adsorbent (e.g., zeolite, alumina and silica gel) in order to further purify the obtained 1,1,1,5,5,5-hexafluoroacetylacetone.

[0013] It is possible to dehydrate a 1,1,1,5,5,5-hexafluoroacetylacetone hydrate by a conventional method, thereby obtaining its anhydride. R. Belford, J. Inorganic and Nuclear Chemistry, 1956, Vol. 2, pp. 11-31 discloses such method in which a dispersion is prepared by shaking 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate with approximately three times its volume of 98% sulfuric acid. After the dispersion has been allowed to stand overnight, dehydration of the product is repeated with a fresh batch of sulfuric acid. The resulting upper layer is siphoned off and distilled, thereby obtaining the anhydride (yield: 98%) as a distillate between 70.0-70.2° C. J. Amer. Chem. Soc., 78, 2790 (1956) discloses another method in which anhydrous calcium sulfate is mixed with 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate. Then, the resulting mixture is heated. The distillate is again treated with anhydrous calcium sulfate and distilled, thereby obtaining the anhydride of a boiling point of 68° C. (736 mm.). There is known a still another method in which 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate, together with phosphorus pentoxide, is heated in ether.

[0014] In the invention, the hydration of the step (a) may be conducted at a temperature of about 0-90° C., preferably about 20-70° C. If it is lower than 0° C., the reaction rate may become too low. If it is higher than 90° C., the yield of the 1,1,1,5,5,5-hexafluoroacetylacetone hydrate may become too low.

[0015] The above-mentioned extracting solvent, in which a 1,1,1,5,5,5-hexafluoroacetylacetone hydrate is soluble, can be selected from ethers and halogen-containing solvents. This solvent is naturally in the form of liquid upon its use. Its boiling point is not particularly limited, but is preferably about 100° C. or lower. Examples of the ethers are diethyl ether, diisopropyl ether, diisobutyl ether, dibutyl ether, t-butyl methyl ether, tetrahydrofuran, anisole, and dioxane. Examples of the halogen-containing solvents are methylene chloride, chloroform, carbon tetrachloride, 1,2-dichloroethane, 1,2-bis(trifluoromethyl)benzene, 1,3-bis(trifluoromethyl)benzene, 1,4-bis(trifluoromethyl)benzene, and 2,4-dichlorobenzotrifluoride. Of these, the ethers are preferable. Furthermore, t-butyl methyl ether is particularly preferable.

[0016] In the invention, it is possible by the step (a) to obtain a crude 1,1,1,5,5,5-hexafluoroacetylacetone hydrate. Prior to the dehydration, it is preferable to bring the crude 1,1,1,5,5,5-hexafluoroacetylacetone hydrate into contact with a poor solvent in which 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate is substantially insoluble. With this, impurities are more remarkably removed from the crude 1,1,1,5,5,5-hexafluoroacetylacetone hydrate. The way of bringing it into contact with the poor solvent is not particularly limited. For example, it is possible to disperse the crude 1,1,1,5,5,5-hexafluoroacetylacetone hydrate in the poor solvent. Then, the precipitated 1,1,1,5,5,5-hexafluoroacetylacetone hydrate can be separated by filtration. As another example, it is possible to apply the poor solvent as a washing liquid to the crude 1,1,1,5,5,5-hexafluoroacetylacetone hydrate.

[0017] The above-mentioned poor solvent can be selected from hydrocarbons and fluorine-containing solvents free from chlorine. It is needless to say that this poor solvent is in the form of liquid upon its use. This poor solvent is not particularly limited, and its boiling point is preferably not higher than about 200° C. Examples of the hydrocarbons are (1) aliphatic hydrocarbons such as n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane and isomers of these, the isomers being in liquid at about 5° C.; (2) aromatic hydrocarbons such as benzene, toluene, o-xylene, m-xylene, p-xylene, ethyl benzene, and mesitylene; (3) alicyclic hydrocarbons such as cyclopentane, cyclohexane, methylcyclopentane, methylcyclohexane, tetralin, and decalin; and (4) industrial gasolines (mixtures of hydrocarbon solvents) such as ligroin and petroleum ether. Examples of the fluorine-containing solvents are 1,2-bis(trifluoromethyl)benzene, 1,3-bis(trifluoromethyl)benzene, 1,4-bis(trifluoromethyl)benzene, 1,1,1,3,3-pentafluoropropane, 1,1,1,3,3-pentafluorobutane, heptafluorocyclopentane, and perfluorinated cyclic ethers (FLORINAT®). It is possible to use a mixture of at least two of these.

[0018] It is optional to mix the poor solvent with a small amount of a good solvent in which solubility of 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate is higher than in the poor solvent. The amount of the good solvent may be not greater than 30 parts by weight per 100 parts by weight of the poor solvent. The good solvent in the invention is not particularly limited. Its examples are ethers such as diethyl ether, dibutyl ether, t-butyl methyl ether, diisopropyl ether, and tetrahydrofuran (THF); and alcohols such as methanol, ethanol, n-propanol, isopropanol, and n-butanol.

[0019] The temperature for bringing the crude 1,1,1,5,5,5-hexafluoroacetylacetone hydrate with the poor solvent is not particularly limited. It is preferably about 0-90° C., more preferably about 20-60° C. In view of operability, it is preferably a temperature requiring no heating nor cooling.

[0020] In the invention, the hydration can also be conducted in the poor solvent by adding 2 parts by mole or greater of water to 1 part by mole of the crude 1,1,1,5,5,5-hexafluoroacetylacetone. In this hydration, it is preferable to use water in an amount of about 2-10 moles, more preferably about 2-7 moles, still more preferably about 2-5 moles, per mole of the crude 1,1,1,5,5,5-hexafluoroacetylacetone. The 1,1,1,5,5,5-hexafluoroacetylacetone hydrate obtained by this hydration is almost in the form of solid, since the hydration is conducted in the poor solvent. Even in this hydration, an aqueous layer may be formed by adding an excessive amount of water. In this case, the 1,1,1,5,5,5-hexafluoroacetylacetone hydrate is partially dissolved in the aqueous layer. It is, however, possible to collect such hydrate by extracting the aqueous layer with the above-mentioned extracting solvent. After the hydration, it is possible to obtain a 1,1,1,5,5,5-hexafluoroacetylacetone hydrate in the form of solid (crystals) by removing the poor solvent by concentration or filtration. The resulting 1,1,1,5,5,5-hexafluoroacetylacetone hydrate (dihydrate) can be dehydrated into the target 1,1,1,5,5,5-hexafluoroacetylacetone. Prior to this dehydration, it is optional to bring this hydrate into contact with the poor solvent.

[0021] In the invention, it is preferable to use a reaction vessel made of glass, fluororesin, or a material lined with one of these.

[0022] The following nonlimitative examples are illustrative of the present invention.

EXAMPLE 1

[0023] A 200-liter glass-lined reaction vessel, equipped with a thermoelectric thermometer and a stirrer, was charged with 33.0 kg of a crude 1,1,1,5,5,5-hexafluoroacetylacetone, 49.0 kg of water, and 1.7 kg of 98% sulfuric acid. This crude hexafluoroacetylacetone was found to have a purity of 97.0% by a gas chromatography (detector: FID, column: DB-1, column size: 0.25 mm×60 m). The reaction was conducted for 6 hr, while the reaction mixture was maintained at 60° C. After the reaction, the reaction liquid was cooled down to about 20° C., followed by extraction with 62.0 kg of t-butyl methyl ether. The resulting aqueous layer was extracted again with 12.7 kg of t-butyl methyl ether. The resulting two organic layers were combined together, followed by distilling t-butyl methyl ether off. To the obtained crude 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate 60.0 kg of toluene were added, followed by stirring for 2 hr at a liquid temperature of 15-20° C. The resulting crystals were separated by centrifugation, filtration and vacuum drying with a vibrating dryer, thereby obtaining 31.9 kg of 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate. Then, a 200-liter glass-lined reaction vessel, equipped with a thermoelectric thermometer and a stirrer, was charged with 31.9 kg of the obtained 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate and 63.8 kg of 98% sulfuric acid, followed by stirring for 4 hr at a temperature of 15-20° C. Then, the reaction liquid was allowed to stand still for 1 hr to have two layers separated from each other. Then, 23.8 kg of 1,1,1,5,5,5-hexafluoroacetylacetone were obtained by distillation from the organic layer. This product was found by the gas chromatography to be 1,1,1,5,5,5-hexafluoroacetylacetone having a purity of 99.9% (areal % in gas chromatography).

EXAMPLE 2

[0024] A 200-liter glass-lined reaction vessel, equipped with a thermoelectric thermometer and a stirrer, was charged with 33.0 kg of a crude 1,1,1,5,5,5-hexafluoroacetylacetone (purity: 97.0%), 100 kg of toluene, 8.5 kg of water, and 0.09 kg of 98% sulfuric acid. The reaction was conducted for 5 hr, while the reaction mixture was maintained at 60° C. After the reaction, the reaction liquid was cooled down to about 20° C. The resulting crystals were separated by centrifugation, filtration and vacuum drying with a vibrating dryer, thereby obtaining 31.0 kg of 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate. Then, a 200-liter glass-lined reaction vessel, equipped with a thermoelectric thermometer and a stirrer, was charged with 31.0 kg of the obtained 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate and 62.0 kg of 98% sulfuric acid, followed by stirring for 4 hr at a temperature of 15-20° C. Then, the reaction liquid was allowed to stand still for 1 hr to have two layers separated from each other. Then, 24.2 kg of 1,1,1,5,5,5-hexafluoroacetylacetone were obtained by distillation from the organic layer. This product was found by the gas chromatography to be 1,1,1,5,5,5-hexafluoroacetylacetone having a purity of 99.9%.

EXAMPLE 3

[0025] A 200-liter glass-lined reaction vessel, equipped with a thermoelectric thermometer and a stirrer, was charged with 33.0 kg of a crude 1,1,1,5,5,5-hexafluoroacetylacetone (purity: 97.0%), 100 kg of toluene, and 8.6 kg of water. The reaction was conducted for 5 hr, while the reaction mixture was maintained at 60° C. After the reaction, the reaction liquid was cooled down to about 20° C. The resulting crystals were separated by centrifugation, filtration and vacuum drying with a vibrating dryer, thereby obtaining 32.3 kg of 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate. Then, a 200-liter glass-lined reaction vessel, equipped with a thermoelectric thermometer and a stirrer, was charged with 32.3 kg of the obtained 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate and 64.6 kg of 98% sulfuric acid, followed by stirring for 4 hr at a temperature of 15-20° C. Then, the reaction liquid was allowed to stand still for 1 hr to have two layers separated from each other. Then, 25.2 kg of 1,1,1,5,5,5-hexafluoroacetylacetone were obtained by distillation from the organic layer. This product was found by the gas chromatography to be 1,1,1,5,5,5-hexafluoroacetylacetone having a purity of 99.9%.

[0026] The entire disclosure of Japanese Patent Application No. 2000-178891 filed on Jun. 14, 2000, including specification, claims and summary, is incorporated herein by reference in its entirety.

Claims

1. A process for purifying a crude 1,1,1,5,5,5-hexafluoroacetylacetone, said process comprising:

(a) hydrating said crude 1,1,1,5,5,5-hexafluoroacetylacetone; and

(b) dehydrating a product of said hydrating, thereby obtaining a purified 1,1,1,5,5,5-hexafluoroacetylacetone.

2. A process according to claim 1, wherein said product of said hydrating comprises a 1,1,1,5,5,5-hexafluoroacetylacetone hydrate.

3. A process according to claim 2, wherein said 1,1,1,5,5,5-hexafluoroacetylacetone hydrate is 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate.

4. A process according to claim 1, wherein said hydrating is conducted by adding 2 parts by mole or greater of water to 1 part by mole of said crude 1,1,1,5,5,5-hexafluoroacetylacetone.

5. A process according to claim 4, wherein said hydrating is conducted by further adding an acid to said crude 1,1,1,5,5,5-hexafluoroacetylacetone.

6. A process according to claim 1, wherein said hydrating is conducted at a temperature of from 0 to 90° C.

7. A process according to claim 1, wherein, prior to said dehydrating, said process further comprises:

(c) extracting said product of said hydrating with a solvent in which a 1,1,1,5,5,5-hexafluoroacetylacetone hydrate is soluble, thereby obtaining an organic layer; and

(d) removing said solvent from said organic layer, thereby obtaining a product comprising said 1,1,1,5,5,5-hexafluoroacetylacetone hydrate.

8. A process according to claim 7, wherein said solvent has a boiling point of not higher than about 100° C.

9. A process according to claim 7, wherein said solvent is at least one selected from the group consisting of ethers and halogen-containing organic solvents.

10. A process according to claim 9, wherein said ethers are diethyl ether, diisopropyl ether, diisobutyl ether, dibutyl ether, t-butyl methyl ether, tetrahydrofuran, anisole, and dioxane, wherein said halogen-containing organic solvents are methylene chloride, chloroform, carbon tetrachloride, 1,2-dichloroethane, 1,2-bis(trifluoromethyl)benzene, 1,3-bis(trifluoromethyl)benzene, 1,4-bis(trifluoromethyl)benzene, and 2,4-dichlorobenzotrifluoride.

11. A process according to claim 9, wherein said solvent is t-butyl methyl ether.

12. A process for purifying a crude 1,1,1,5,5,5-hexafluoroacetylacetone, said process comprising:

(a) hydrating said crude 1,1,1,5,5,5-hexafluoroacetylacetone, thereby obtaining a crude 1,1,1,5,5,5-hexafluoroacetylacetone hydrate;

(b) bringing said crude 1,1,1,5,5,5-hexafluoroacetylacetone hydrate into contact with a poor solvent in which 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate is substantially insoluble, thereby obtaining a 1,1,1,5,5,5-hexafluoroacetylacetone hydrate; and

(c) dehydrating said 1,1,1,5,5,5-hexafluoroacetylacetone hydrate into a purified 1,1,1,5,5,5-hexafluoroacetylacetone.

13. A process according to claim 12, wherein said poor solvent has a boiling point of not higher than about 200° C.

14. A process according to claim 12, wherein said poor solvent is at least one selected from the group consisting of aromatic hydrocarbons, aliphatic hydrocarbons, alicyclic hydrocarbons, industrial gasolines, and fluorine-containing solvents.

15. A process according to claim 14, wherein said aromatic hydrocarbons are benzene, toluene, o-xylene, m-xylene, p-xylene, ethyl benzene, and mesitylene,

wherein said aliphatic hydrocarbons are n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane, and isomers thereof, each of said isomers being in a liquid at about 5° C.,

wherein said alicyclic hydrocarbons are cyclopentane, cyclohexane, methylcyclopentane, methylcyclohexane, tetralin, and decalin,

wherein said industrial gasolines are ligroin and petroleum ether,

wherein said fluorine-containing solvents are 1,2-bis(trifluoromethyl)benzene, 1,3-bis(trifluoromethyl)benzene, 1,4-bis(trifluoromethyl)benzene, 1,1,1,3,3-pentafluoropropane, 1,1,1,3,3-pentafluorobutane, heptafluorocyclopentane, and perfluorinated cyclic ethers.

16. A process according to claim 12, wherein said bringing is conducted by bringing said crude 1,1,1,5,5,5-hexafluoroacetylacetone hydrate into contact with a mixture of said poor solvent and a good solvent that is in an amount of not greater than 30 parts by weight per 100 parts by weight of said poor solvent, said good solvent being such that 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate has a higher solubility in said good solvent than in said poor solvent.

17. A process according to claim 16, wherein said good solvent is at least one selected from the group consisting of ethers and alcohols.

18. A process according to claim 17, wherein each of said ethers has a boiling point of about 30-140° C.

19. A process according to claim 17, wherein said ethers are diethyl ether, dibutyl ether, t-butyl methyl ether, diisopropyl ether, and tetrahydrofuran.

20. A process according to claim 17, wherein said alcohols are methanol, ethanol, n-propanol, isopropanol, and n-butanol.

21. A process for purifying a crude 1,1,1,5,5,5-hexafluoroacetylacetone, said process comprising:

(a) hydrating said crude 1,1,1,5,5,5-hexafluoroacetylacetone in a poor solvent in which 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate is substantially insoluble, thereby obtaining a 1,1,1,5,5,5-hexafluoroacetylacetone hydrate; and

(b) dehydrating said 1,1,1,5,5,5-hexafluoroacetylacetone hydrate into a purified 1,1,1,5,5,5-hexafluoroacetylacetone.

22. A process according to claim 21, wherein, prior to said dehydrating, said 1,1,1,5,5,5-hexafluoroacetylacetone hydrate is brought into contact with a poor solvent in which 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate is substantially insoluble.