JPS6128652B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing heptafluoroisobutyric acid ester. Various highly fluorinated compounds have been known and are used for various purposes because they are very thermally stable and have low surface energy properties. For example, it is widely used in heat exchange media, solvents, lubricants, surface treatment agents, heat-resistant and chemical-resistant resin compounding agents, etc. Regarding perfluorocarboxylic acid esters, for example, U.S. Patent No.
As seen in the specification of No. 2567011, it is clear that it has the above-mentioned surface properties, and various examples of applications are also described in the specification. Conventionally, perfluorocarboxylic acid esters have generally been synthesized mainly by two methods. Namely, there is a method in which perfluorocarboxylic acid fluoride, which can be synthesized by electrolytic fluorination of carboxylic acids and their derivatives, is reacted with alcohol, and a method in which perfluorocarboxylic acid obtained by oxidation of perfluoroolefins is obtained in the presence of a concentrated sulfuric acid catalyst. This method involves esterification using an alcohol. The former synthesis method has the disadvantage of generating hydrogen fluoride, which is highly toxic and difficult to handle, and the latter synthesis method also has the disadvantage of requiring heating in the presence of a considerable amount of concentrated sulfuric acid. The present inventors have been conducting research on the synthesis of useful fluorine-containing compounds for many years, and found that heptafluoroisobutyric acid ester can be produced easily under mild conditions and with even better yields using readily available raw materials. We have now completed and provided the present invention. One type of raw material used in the present invention is a halogenated formate. The halogenated formate is a compound represented by the general formula XCOOR (where R is a hydrocarbon residue), and can be used without being limited to its production method. X in the above formula refers to fluorine, chlorine, fluorine, or iodine. In the above formula, the term "hydrocarbon residue" refers to the base side of a compound derived by replacing the hydrogen atom with another atom or atomic group in the chemical formula of a saturated or unsaturated hydrocarbon compound consisting of carbon atoms and hydrogen atoms. refers to the base of That is, in the general formula, R is not particularly limited as long as it is the above-mentioned hydrocarbon residue and can be selected as necessary, but generally it is a group having 1 carbon number such as a methyl group, ethyl group, isoamyl group, octyl group, or nonyl group.
~20 preferably 1 to 12 straight chain or branched alkyl groups; alkenyl groups such as vinyl groups and allyl groups;
Preferred are cycloalkyl groups such as cyclohexyl; aralkyl groups such as phenethyl; and phenyl. Also suitable are groups derived by substituting one or more of the hydrogen atoms in these hydrocarbon residues with other atoms or atomic groups, and the atoms or atomic groups that replace the hydrogen atoms are not particularly limited. However, those that are inert in the reaction for producing heptafluoroisobutyric acid ester are more preferable, such as halogens such as fluorine, chlorine, fluorine, and iodine; esters; sulfonic acid esters; ketones; thioketones; ethers; thioethers; aldehydes, etc. atoms or atomic groups are preferred. Hexafluoropropylene used in the present invention is a compound represented by the general formula CF ₃ CF=CF ₂ and can be used without being limited to its production method. Furthermore, as the metal fluoride, any known metal fluoride can be used without particular limitation, but industrially sodium,
Fluorides of alkali metals such as potassium and cesium or alkaline earth metals such as magnesium and zinc are preferably used. Particularly suitable are cesium fluoride and potassium fluoride. It is also possible to use a mixture of these metal fluorides. The heptafluoroisobutyric acid ester obtained in the present invention is represented by the general formula (CF ₃ ) ₂ CFCOOR. R in the general formula is determined by R of the halogenated formate, ie, XOOOR, which is one of the raw materials. Although its properties vary depending on the type of R in the general formula, the number of carbon atoms, etc., many of them usually exist as a liquid at room temperature and pressure. Also, like other organic compounds, the boiling point tends to decrease as the number of carbon atoms decreases.
When a phenyl group or the like is bonded, the boiling point also tends to increase. Furthermore, the heptafluoroisobutyric acid ester obtained in the present invention is generally colorless and has an ester odor. Additionally, those that are soluble in organic solvents such as alcohol, ether, chloroform, ethyl acetate, and benzene are generally used. X in the halogenated formate ester represented by the general formula XCOOR may be fluorine, chlorine, silium, or iodine, but the reaction mechanism is somewhat different between fluorine and other halogens. That is, when a fluoroformate is used, the metal fluoride acts as a catalyst and reacts directly with hexafluoropropylene to obtain the heptafluoroisobutyrate, which is the object of the present invention. However, when using a chloroformate, a promoformate, or an iodoformate, these esters first react with a metal fluoride to form a fluoroformate, and then the fluoroformate reacts with hexafluoropropylene. It is presumed that the reaction occurs through a step reaction mechanism. Therefore, in the latter case, as will be described in detail later, it is necessary to use a large amount of metal fluoride commensurate with the reaction. The production of heptafluoroisobutyric acid ester in the present invention is generally carried out in the presence of a solvent. The solvent is not particularly limited as long as it is a polar nonaqueous solvent that does not react with the raw materials, but typical examples include diglyme, triglyme, tetraglyme, sulfolane, hexamethylphosphotriamide, dimethylformamide, dimethylsulfoxide, and acetonitrile. , benzonitrile,
Dioxane, N-methylpyrrolidone, etc. are preferred, and glyme-based solvents are particularly preferred. When selecting the solvent, it is advantageous for the isolation operation to select a solvent that has a boiling point that is significantly different from the boiling point of the product. The reaction temperature can generally be selected from the range of -80°C to 200°C, but generally room temperature may be used as it is convenient for operation. Although the pressure may be increased, normal pressure, or reduced pressure, it is industrially convenient to carry out the reaction under natural pressure with the reactants charged. Note that the reaction atmosphere may or may not be replaced with an inert gas. The reaction time is not particularly limited and can be selected from several minutes to several days, but generally several hours is sufficient. The container may be made of glass or metal. The molar ratio of hexafluoropropylene and halogenated formate may be selected within a suitable range depending on the structure and reactivity of the latter, but it is usually better to use more hexafluoropropylene during the isolation process. This is very convenient. As mentioned above, the amount of metal fluoride used as a catalyst varies depending on the type of halogenated formate. That is, when using a fluoroformate, the metal fluoride is
It is preferable to use between 0.1 and 100 mol%. Furthermore, when chloro, promo, or iodoformate is used as the halogenated formate, the metal fluoride reacts with these halogenated formates to produce fluoroformate, so an excess of metal fluoride is needed to compensate for this reaction. It is necessary to use a compound. In this case, the metal fluoride is generally used in an amount of 1 mole or more based on the halogenated formate. Regardless of the type of halogenated formate, it is a preferred embodiment to use stirring as a means of uniformly dispersing the metal fluoride during the reaction. EXAMPLES Examples are shown below to explain the present invention more specifically, but the present invention is not limited to these Examples. In addition, the reaction yield in the examples was calculated based on the weight of the corresponding heptafluoroisobutyric acid ester isolated by distillation from the reaction mixture with respect to the weight of the halogenated formic acid ester used as the raw material. Example 1 Cesium fluoride (2.2 g), nonyl fluoroformate (6.58 g), and tetraglyme (20 ml) were placed in a 300 ml glass autoclave and cooled to -78°C in a dry ice-methanol bath. Next, hexafluoropropylene (20 ml) was added, and the mixture was gradually warmed to room temperature (23°C) over about 20 minutes while stirring. The reaction was allowed to proceed at room temperature for 6 hours with stirring. The obtained reaction mixture was transferred to a 100 ml eggplant-shaped flask and subjected to fractional distillation under reduced pressure to obtain the target product having a boiling point of 82-84°C/6 mmHg. The yield was 6.24g (reaction yield 53.0
%). The structure of this product was determined by various measurements described below. (a) Infrared absorption spectrum (IR) CH absorption at 2950, 2910, and 2840 cm ^-1 , and 1790 and
Carbonyl of ester group (C=O) at 1770cm ^-1
absorption and CF absorption between 1400 and 1000 cm ^-1 . (b) ^19F- nuclear magnetic resonance spectrum ( ^19F−
nmr) (CFCl ₃ standard, δppm) The peak based on CF ₃ at −7.51 ppm is the coupling constant J
Appears as a double line at =7.4Hz, -181.0ppm
The presence of the heptafluoroisopropyl group [(CF ₃ ) ₂ CF] is confirmed by the appearance of a heptafluoroisopropyl group [(CF 3 ) 2 CF] at a coupling constant J of 7.4 Hz. (c) ¹³ carbon nuclear magnetic resonance spectrum ( ¹³ C−nmr)
(tetramethylsilane standard, δppm, ^1H and
¹⁹ F-Dekatu Spring) C F ₃ to 119.7 ppm,
CF at 88.9ppm, C =O at 158ppm, 68.9ppm
In addition to the peaks based on each carbon, O C H ₂ at 13.8 ppm and C H ₃ at 13.8 ppm, 32.5, 29.9, 29.7, 29.6,
It shows seven peaks based on C H ₂ carbon at 28.8, 26.0 and 23.1 ppm, (CF ₃ ) ₂ CF group, C-O
The presence of a group and a nonyl group [CH ₂ (CH ₂ ) ₇ CH ₃ ] was confirmed. (d) Mass spectrometry (m/e value) As a result of measurement at 20 eV, the following peaks were observed. 255 _{( C3F7COOCH2CH2CH2 ) , 197}
( _C3F7CO ), ₁₆₉ ( _C3F7 ) _. (E) Elemental analysis values H5.45%, C45.50%, F39.38%, theoretical values for C ₁₃ H ₁₉ F ₇ O ₂ (340.29)
It matched well with H5.63%, C45.88%, and F39.08%. From the above various measurement results, the structure of the target product obtained in the above reaction is (CF ₃ ) ₂ CFCOOCH ₂
It was confirmed that it was (CH ₂ ) ₇ CH ₃ . Example 2 Table 1 was used instead of nonyl fluoroformate in Example 1.
The reaction was carried out in the same manner as in Example 1, except that the metal fluoride shown in Table 1 was used instead of cesium fluoride and the reaction conditions were changed as shown in Table 1, and the product heptafluoroisobutyric acid was The structure of the ester was also determined in the same manner as in Example 1. The yield and boiling point of the isolated heptafluoroisobutyric acid ester were as shown in Table 1.

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Claims (1)

[Scope of Claims] 1. A method for producing heptafluoroisobutyric acid ester, which comprises reacting hexafluoropropylene and fluoroformic acid ester in the presence of a metal fluoride. 2 Heptafluoroisobutyrate ester characterized by reacting at least one halogenated formate selected from the group consisting of hexafluoropropylene, chloroformate, bromoformate and iodoformate and a metal fluoride. Production method.