Method for producing perfluoro (1,3-dioxolane)-2-carboxylate, method for inhibiting decomposition, and perfluoro (1,3-dioxolane)-2-carboxylate-containing composition

Abstract

To provide a production method capable of inhibiting the decomposition of perfluoro (1,3-dioxolane)-2-carboxylate, a method for inhibiting decomposition, and a composition therefor.SOLUTION: There are provided a production method, a decomposition suppression method, and a composition thereof that can suppress the decomposition of perfluoro (1,3-dioxolane)-2-carboxylate represented by formula (4). The production method for perfluoro (1,3-dioxolane)-2-carboxylate includes a step of reacting the corresponding perfluoro (1,3-dioxolane)-2-carboxylic acid fluoride and / or the corresponding perfluoro (2-hydroxymethyl-1,3-dioxolane) salt in the presence of a difluoromethyl compound represented by formula Ar1-CF2 H to convert it into the corresponding perfluoro (1,3-dioxolane)-2-carboxylate, thereby obtaining a reaction product. In the formula, two R1's are the same and represent a fluorine atom or a perfluoroalkyl group having 1 to 6 carbon atoms, and M+ represents a counter cation.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a perfluoro(1,3-dioxolane)-2-carboxylate, a method for inhibiting decomposition, and a perfluoro(1,3-dioxolane)-2-carboxylate-containing composition. [Background technology]

[0002] Non-Patent Document 1 describes that decarboxylation proceeds when potassium 2-[perfluoro(2,4-dimethyl-1,3-dioxolane)]carboxylate is heated in a bis(2-ethoxyethyl) ether solvent. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Mikes et al. Macromolecules, 38, 10, 2005. Summary of the Invention [Problem to be solved by the invention]

[0004] The above description is found in Non-Patent Document 1. However, potassium 2-[perfluoro(2,4-dimethyl-1,3-dioxolane)]carboxylate has a stability problem because the reaction proceeds slowly even at around room temperature in the presence of a solvent.

[0005] Perfluoro(1,3-dioxolane)-2-carboxylate is used as a raw material for synthesizing polymers that are promising for use as resins for gas separation membranes, etc. However, perfluoro(1,3-dioxolane)-2-carboxylate is a compound with poor stability because it undergoes a gradual decarboxylation reaction in the presence of a solvent, leading to decomposition. While low-temperature storage is one method of suppressing decomposition and reducing the degree of productivity loss, low-temperature storage requires high energy costs. Therefore, an energy-saving method of suppressing decomposition is desired.

[0006] In view of the above, an object of the present invention is to provide a production method capable of suppressing the decomposition of perfluoro(1,3-dioxolane)-2-carboxylate, a method for suppressing the decomposition of perfluoro(1,3-dioxolane)-2-carboxylate, and a perfluoro(1,3-dioxolane)-2-carboxylate-containing composition. [Means for solving the problem]

[0007] As a result of extensive research, the present inventors have found that the decomposition of perfluoro(1,3-dioxolane)-2-carboxylate can be suppressed in the presence of a difluoromethyl compound.

[0008] That is, one aspect of the present invention is as follows. [1] Formula (1): [ka] [In formula (1), two R 1 are the same and represent a fluorine atom or a perfluoroalkyl group having 1 to 6 carbon atoms (meaning 1 or more and 6 or less). and / or perfluoro(1,3-dioxolane)-2-carboxylic acid fluoride represented by the formula: Formula (2): [ka] [In formula (2), two R 1 has the same meaning as above. M + represents a counter cation.] A perfluoro(2-hydroxymethyl-1,3-dioxolane) salt represented by Formula (3) [ka] [In formula (3), Ar 1 represents an aryl group having 6 to 10 carbon atoms (meaning 6 or more and 10 or less) which may be substituted with one or more selected from the group consisting of an alkyl group having 1 to 6 carbon atoms, a fluorine atom, a chlorine atom, a bromine atom, a methoxy group, an ethoxy group, and a phenyl group.] and an organic solvent, Formula (4): [ka] [In formula (4), two R 1 and M + has the same meaning as above.] and obtaining a reaction product by converting the compound represented by the formula (I) into a perfluoro(1,3-dioxolane)-2-carboxylate represented by the formula (I). [2] A method for producing perfluoro(1,3-dioxolane)-2-carboxylate according to [1], wherein the difluoromethyl compound represented by the formula (3) is contained in an amount of 0.1 to 1 times (meaning 0.1 times or more and 1 times or less) the mass of perfluoro(1,3-dioxolane)-2-carboxylate represented by the formula (4). [3] The method for producing perfluoro(1,3-dioxolane)-2-carboxylate according to [1] or [2], wherein the difluoromethyl compound represented by the formula (3) is one or more difluoromethyl compounds selected from the group consisting of difluoromethylbenzene, 1-difluoromethyl-4-methylbenzene, 1-difluoromethyl-4-ethylbenzene, 1-difluoromethyl-4-methoxybenzene, and 1-difluoromethyl-4-ethoxybenzene. [4] The method for producing perfluoro(1,3-dioxolane)-2-carboxylate according to any one of [1] to [3], wherein the organic solvent is one or more ether solvents selected from the group consisting of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether. [5] The method for producing perfluoro(1,3-dioxolane)-2-carboxylate according to any one of [1] to [4], wherein the basic aqueous solution is an aqueous solution prepared by dissolving one or more basic compounds selected from the group consisting of alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal carbonates, alkaline earth metal carbonates, alkali metal hydrogencarbonates, and alkali metal hydrogencarbonates. [6] The method for producing perfluoro(1,3-dioxolane)-2-carboxylate according to [5], wherein the basic compound is at least one basic compound selected from the group consisting of alkali metal hydroxides and alkali metal carbonates. [7] M in the above formula (4) + The method for producing perfluoro(1,3-dioxolane)-2-carboxylate according to any one of [1] to [6], wherein is an alkali metal cation and / or an alkaline earth metal cation. [8] A method for inhibiting decomposition of perfluoro(1,3-dioxolane)-2-carboxylate, comprising the step of reacting perfluoro(1,3-dioxolane)-2-carboxylic acid fluoride represented by the above formula (1) and / or perfluoro(2-hydroxymethyl-1,3-dioxolane) salt represented by the above formula (2) with a basic aqueous solution in the presence of a difluoromethyl compound represented by the above formula (3) and an organic solvent to convert it into perfluoro(1,3-dioxolane)-2-carboxylate represented by the above formula (4), thereby obtaining a reaction product. [9] The method for inhibiting decomposition of perfluoro(1,3-dioxolane)-2-carboxylate according to [8], wherein the difluoromethyl compound represented by the formula (3) is contained in an amount of 0.1 to 1 times (meaning 0.1 times or more and 1 times or less) the mass of perfluoro(1,3-dioxolane)-2-carboxylate represented by the formula (4).

[10] The method for inhibiting decomposition of perfluoro(1,3-dioxolane)-2-carboxylate according to [8] or [9], wherein the difluoromethyl compound represented by the formula (3) is difluoromethylbenzene, 1-difluoromethyl-4-methylbenzene, 1-difluoromethyl-4-ethylbenzene, 1-difluoromethyl-4-methoxybenzene, or 1-difluoromethyl-4-ethoxybenzene.

[11] A composition comprising a perfluoro(1,3-dioxolane)-2-carboxylate represented by the above formula (4), a difluoromethyl compound represented by the above formula (3), and an organic solvent.

[12] The composition according to

[11] , comprising a difluoromethyl compound represented by the above formula (3) in an amount of 0.1 to 1 times (meaning 0.1 times or more and 1 times or less) the mass of perfluoro(1,3-dioxolane)-2-carboxylate represented by the above formula (4).

[13] The composition according to

[11] or

[12] , wherein the difluoromethyl compound represented by the formula (3) is one or more difluoromethyl compounds selected from the group consisting of difluoromethylbenzene, 1-difluoromethyl-4-methylbenzene, 1-difluoromethyl-4-ethylbenzene, 1-difluoromethyl-4-methoxybenzene, and 1-difluoromethyl-4-ethoxybenzene.

[14] The composition according to any one of

[11] to

[13] , wherein the organic solvent is one or more ether solvents selected from the group consisting of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether.

[15] M in the above formula (4) + is an alkali metal cation and / or an alkaline earth metal cation. [Effects of the Invention]

[0009] According to a method for producing perfluoro(1,3-dioxolane)-2-carboxylate according to one aspect of the present invention, perfluoro(1,3-dioxolane)-2-carboxylic acid fluoride and / or perfluoro(2-hydroxymethyl-1,3-dioxolane) salt is reacted with a basic aqueous solution in the presence of a specific difluoromethyl compound and an organic solvent, thereby suppressing decomposition of the perfluoro(1,3-dioxolane)-2-carboxylate. The method for producing perfluoro(1,3-dioxolane)-2-carboxylate according to one aspect of the present invention can be industrially implemented and can reduce productivity losses. According to a method for suppressing the decomposition of perfluoro(1,3-dioxolane)-2-carboxylate according to one embodiment of the present invention, the decomposition rate of perfluoro(1,3-dioxolane)-2-carboxylate in an organic solvent can be reduced by using a composition containing a difluoromethyl compound. DETAILED DESCRIPTION OF THE INVENTION

[0010] The method for producing perfluoro(1,3-dioxolane)-2-carboxylate, the method for inhibiting decomposition, and the composition according to one embodiment of the present invention will be described in further detail below.

[0011] [Manufacturing method] One aspect of the present invention relates to a method for producing perfluoro(1,3-dioxolane)-2-carboxylic acid salt, comprising a step of reacting perfluoro(1,3-dioxolane)-2-carboxylic acid fluoride represented by formula (1) and / or perfluoro(2-hydroxymethyl-1,3-dioxolane) salt represented by formula (2) with a basic aqueous solution in the presence of a difluoromethyl compound represented by formula (3) and an organic solvent to convert it into perfluoro(1,3-dioxolane)-2-carboxylic acid salt represented by formula (4) to obtain a reaction product. The perfluoro(1,3-dioxolane)-2-carboxylic acid fluoride is one or more compounds selected from the group represented by the above formula (1), the perfluoro(2-hydroxymethyl-1,3-dioxolane) salt is one or more compounds selected from the group represented by the above formula (2), the difluoromethyl compound is one or more compounds selected from the group represented by the above formula (3), and the perfluoro(1,3-dioxolane)-2-carboxylic acid salt is one or more compounds selected from the group represented by the above formula (4). In the present invention and this specification, unless otherwise specified, "to" means that the number on the left is equal to or greater than the number on the right and the number on the right is equal to or less than the number on the left.

[0012] In the present invention and this specification, the term "difluoromethyl compound" refers to a single difluoromethyl compound or a mixture of two or more difluoromethyl compounds. In the above-mentioned production method, one or more difluoromethyl compounds can be used.

[0013] The difluoromethyl compound may be a commercially available product, or may be a by-product of the production process of perfluoro(1,3-dioxolane)-2-carboxylic acid fluoride and / or perfluoro(2-hydroxymethyl-1,3-dioxolane) salt and used as is.

[0014] Perfluoro(1,3-dioxolane)-2-carboxylic acid fluoride that can be used in the above production method is represented by the following formula (1).

[0015] [ka]

[0016] In equation (1), two R 1 are the same and represent a fluorine atom or a perfluoroalkyl group having 1 to 6 carbon atoms (meaning 1 or more and 6 or less).

[0017] The perfluoroalkyl group having 1 to 6 carbon atoms may be linear or branched. The number of carbon atoms is 1 or more, and can be 2 or more. The number of carbon atoms is 6 or less, and can be 5 or less, 4 or less, or 3 or less. Specific examples of the perfluoroalkyl group include a trifluoromethyl group, a pentafluoroethyl group, a heptafluoro-n-propyl group, a heptafluoro-isopropyl group, a nonafluoro-n-butyl group, a nonafluoro-isobutyl group, a nonafluoro-sec-butyl group, a nonafluoro-tert-butyl group, a perfluoro(methoxymethyl) group, a perfluoro(ethoxymethyl) group, and the like. R 1 Among these, a trifluoromethyl group, a pentafluoroethyl group, a heptafluoro-n-propyl group, and a nonafluoro-n-butyl group are preferred, and a trifluoromethyl group and a pentafluoroethyl group are more preferred.

[0018] Specific examples of perfluoro(1,3-dioxolane)-2-carboxylic acid fluoride represented by formula (1) include [perfluoro(1,3-dioxolane)]-2-carboxylic acid fluoride, [perfluoro(2,4-dimethyl-1,3-dioxolane)]-2-carboxylic acid fluoride, [perfluoro(2,4-diethyl-1,3-dioxolane)]-2-carboxylic acid fluoride, [perfluoro(2,4-di-n-propyl-1,3-dioxolane)]-2-carboxylic acid fluoride, [perfluoro(2,4-di- [perfluoro(2,4-di-tert-butyl-1,3-dioxolane)]-2-carboxylic acid fluoride, [perfluoro(2,4-di-n-butyl-1,3-dioxolane)]-2-carboxylic acid fluoride, [perfluoro(2,4-di-n-pentyl-1,3-dioxolane)]-2-carboxylic acid fluoride, [perfluoro(2,4-di-n-hexyl-1,3-dioxolane)]-2-carboxylic acid fluoride, and the like.

[0019] The perfluoro(2-hydroxymethyl-1,3-dioxolane) salt that can be used in the above production method is represented by the following formula (2).

[0020] [ka]

[0021] In equation (2), two R 1 has the same meaning as above. That is, in formula (2), two R 1 are the same and represent a fluorine atom or a perfluoroalkyl group having 1 to 6 carbon atoms. M + represents a counter cation.

[0022] R in Equation (2) 1 Regarding R in Eq. (1), 1 As described above, R in formula (2) 1 For specific examples of R in formula (1), 1 As described above.

[0023] M in Equation (2) + Examples of the counter cation represented by the formula (I) include alkali metal cations, alkaline earth metal cations, and ammonium cations. Specifically, examples of the monovalent counter cation include cesium cation, potassium cation, sodium cation, tetrabutylammonium cation, and tetraethylammonium cation. Examples of the divalent counter cation include calcium cation and magnesium cation. In the case of the divalent counter cation, M + (Ca 2+ ) 1 / 2 , (Mg 2+ ) 1 / 2 It can be expressed as follows:

[0024] Specific examples of the perfluoro(2-hydroxymethyl-1,3-dioxolane) salt represented by formula (2) include perfluoro(2-hydroxymethyl-1,3-dioxolane) sodium salt, perfluoro(2-hydroxymethyl-2,4-dimethyl-1,3-dioxolane) sodium salt, perfluoro(2-hydroxymethyl-2,4-diethyl-1,3-dioxolane) sodium salt, perfluoro(2-hydroxymethyl-2,4-di-n-propyl-1,3-dioxolane) sodium salt, and perfluoro(2-hydroxymethyl-2,4-di- n-butyl-1,3-dioxolane) sodium salt, perfluoro(2-hydroxymethyl-2,4-di-sec-butyl-1,3-dioxolane) sodium salt, perfluoro(2-hydroxymethyl-2,4-di-tert-butyl-1,3-dioxolane) sodium salt, perfluoro(2-hydroxymethyl-2,4-di-n-pentyl-1,3-dioxolane) sodium salt, perfluoro(2-hydroxymethyl-2,4-di-n-hexyl-1,3-dioxolane) sodium salt, perfluoro(2-hydroxymethyl-1,3-dioxolane) sodium salt solan) potassium salt, perfluoro(2-hydroxymethyl-2,4-dimethyl-1,3-dioxolane) potassium salt, perfluoro(2-hydroxymethyl-2,4-diethyl-1,3-dioxolane) potassium salt, perfluoro(2-hydroxymethyl-2,4-di-n-propyl-1,3-dioxolane) potassium salt, perfluoro(2-hydroxymethyl-2,4-di-n-butyl-1,3-dioxolane) potassium salt, perfluoro(2-hydroxymethyl-2,4-di-sec-butyl-1,3-dioxolane) potassium salt, perfluoro (2-hydroxymethyl-2,4-di-tert-butyl-1,3-dioxolane) potassium salt, perfluoro(2-hydroxymethyl-2,4-di-n-pentyl-1,3-dioxolane) potassium salt, perfluoro(2-hydroxymethyl-2,4-di-n-hexyl-1,3-dioxolane) potassium salt, perfluoro(2-hydroxymethyl-1,3-dioxolane) cesium salt, perfluoro(2-hydroxymethyl-2,4-dimethyl-1,3-dioxolane) cesium salt, perfluoro(2-hydroxymethyl-2,4-diethyl-1,perfluoro(2-hydroxymethyl-2,4-di-n-propyl-1,3-dioxolane) cesium salt, perfluoro(2-hydroxymethyl-2,4-di-n-butyl-1,3-dioxolane) cesium salt, perfluoro(2-hydroxymethyl-2,4-di-sec-butyl-1,3-dioxolane) cesium salt, perfluoro(2-hydroxymethyl-2,4-di-tert-butyl-1,3-dioxolane) cesium salt, perfluoro(2-hydroxymethyl-2,4-di-n-pentyl-1,3-dioxolane) cesium salt, and perfluoro(2-hydroxymethyl-2,4-di-n-hexyl-1,3-dioxolane) cesium salt.

[0025] The perfluoro(1,3-dioxolane)-2-carboxylic acid fluoride represented by the formula (1) and / or the perfluoro(2-hydroxymethyl-1,3-dioxolane) salt represented by the formula (2) that can be used in the above production method can be produced, for example, by the method described in Macromolecules 2005, Vol. 38, pp. 4237-4245. The perfluoro(1,3-dioxolane)-2-carboxylic acid fluoride represented by the formula (1) and / or the perfluoro(2-hydroxymethyl-1,3-dioxolane) salt represented by the formula (2) can be purified before use in the reaction, and the purification method is not particularly limited. For example, the product can be purified by methods commonly used by those skilled in the art, such as distillation, solvent extraction, silica gel column chromatography, thin-layer preparative chromatography, and preparative liquid chromatography.

[0026] The above production method can be provided with one or more compounds selected from the group consisting of perfluoro(1,3-dioxolane)-2-carboxylic acid fluoride represented by the above formula (1) and perfluoro(2-hydroxymethyl-1,3-dioxolane) salt represented by the above formula (2). That is, the above production method can be provided with only one or more compounds of perfluoro(1,3-dioxolane)-2-carboxylic acid fluoride represented by the above formula (1), or with only one or more compounds of perfluoro(2-hydroxymethyl-1,3-dioxolane) salt represented by the above formula (2), or with one or more compounds of perfluoro(1,3-dioxolane)-2-carboxylic acid fluoride represented by the above formula (1) and one or more compounds of perfluoro(2-hydroxymethyl-1,3-dioxolane) salt represented by the above formula (2).

[0027] The difluoromethyl compound that can be used in the above production method is represented by the following formula (3).

[0028] [ka]

[0029] In formula (3), Ar 1 represents an aryl group having 6 to 10 carbon atoms which may be substituted with one or more groups selected from the group consisting of an alkyl group having 1 to 6 carbon atoms, a fluorine atom, a chlorine atom, a bromine atom, a methoxy group, an ethoxy group, and a phenyl group.

[0030] The alkyl group having 1 to 6 carbon atoms may be linear or branched. The number of carbon atoms is 1 or more, and can be 2 or more. The number of carbon atoms is 6 or less, and can be 5 or less, 4 or less, or 3 or less. Specific examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group.

[0031] Specific examples of the difluoromethyl compound represented by formula (3) include difluoromethylbenzene, 1-difluoromethyl-3-methylbenzene, 1-difluoromethyl-4-methylbenzene, 1-difluoromethyl-3-ethylbenzene, 1-difluoromethyl-4-ethylbenzene, 1-difluoromethyl-3-n-propylbenzene, 1-difluoromethyl-4-n-propylbenzene, 1-difluoromethyl-3-n-butylbenzene, 1-difluoromethyl-4-n-butylbenzene, 1-difluoromethyl-3-sec-butylbenzene, 1-difluoromethyl-4-sec-butylbenzene, 1-difluoromethyl-3-tert-butylbenzene, 1-difluoromethyl-4-tert-butylbenzene, 1-difluoromethyl-3-n-pentylbenzene, 1-difluoromethyl-4-n-pentylbenzene, 1-difluoromethyl-3-n-hexylbenzene, 1-difluoromethyl-4-n-pentylbenzene, 1-difluoromethyl-3-n-hexylbenzene, 1-difluoromethyl-4-n-propylbenzene, 1-difluoromethyl-3-n-butylbenzene, 1-difluoromethyl-4-n-butylbenzene, 1-difluoromethyl-3-n-pentylbenzene, 1-difluoromethyl-4-n-pentylbenzene, 1-difluoromethyl-3-n-hexylbenzene, 1-difluoromethyl-4-n-propylbenzene, 1-difluoromethyl-3-n-butylbenzene, 1-difluoromethyl-4 ... Examples thereof include fluoromethyl-4-n-hexylbenzene, 1-difluoromethyl-2-fluorobenzene, 1-difluoromethyl-3-fluorobenzene, 1-difluoromethyl-4-fluorobenzene, 1-difluoromethyl-2-chlorobenzene, 1-difluoromethyl-3-chlorobenzene, 1-difluoromethyl-4-chlorobenzene, 1-difluoromethyl-2-bromobenzene, 1-difluoromethyl-3-bromobenzene, 1-difluoromethyl-4-bromobenzene, 1-difluoromethyl-2-methoxybenzene, 1-difluoromethyl-3-methoxybenzene, 1-difluoromethyl-4-methoxybenzene, 1-difluoromethyl-2-ethoxybenzene, 1-difluoromethyl-3-ethoxybenzene, 1-difluoromethyl-4-ethoxybenzene, 2-difluoromethylbiphenyl, 3-difluoromethylbiphenyl, and 4-difluoromethylbiphenyl. Among these, preferred are difluoromethylbenzene, 1-difluoromethyl-4-methylbenzene, 1-difluoromethyl-4-ethylbenzene, 1-difluoromethyl-4-methoxybenzene, 1-difluoromethyl-4-ethoxybenzene, etc. One or more difluoromethyl compounds can be selected and subjected to the above production method.The difluoromethyl compound represented by formula (3) is preferably difluoromethylbenzene, 1-difluoromethyl-4-methylbenzene, 1-difluoromethyl-4-ethylbenzene, 1-difluoromethyl-4-methoxybenzene, or 1-difluoromethyl-4-ethoxybenzene, and one or more of these can be selected and subjected to the above-mentioned production method.

[0032] The perfluoro(1,3-dioxolane)-2-carboxylate applicable to the above production method is represented by the following formula (4).

[0033] [ka]

[0034] In equation (4), two R 1 has the same meaning as above. That is, in formula (4), two R 1 are the same and represent a fluorine atom or a perfluoroalkyl group having 1 to 6 carbon atoms. M + represents a counter cation.

[0035] R in Equation (4) 1 Regarding R in Eq. (1), 1 As described above, R in formula (4) 1 For specific examples of R in formula (1), 1 As described above, M in equation (4) + Regarding M in Eq. (2), + As described above, M in formula (4) + For specific examples of M in formula (2), + As described above.

[0036] Specific examples of the perfluoro(1,3-dioxolane)-2-carboxylic acid salt represented by formula (4) include perfluoro(1,3-dioxolane) sodium salt, perfluoro(2,4-dimethyl-1,3-dioxolane) sodium salt, perfluoro(2,4-diethyl-1,3-dioxolane) sodium salt, perfluoro(2,4-di-n-propyl-1,3-dioxolane) sodium salt, perfluoro(2,4-di-n-butyl-1,3-dioxolane) sodium salt, and perfluoro(2,4-di-sec-butyl-1,3-dioxolane) Sodium salt, perfluoro(2,4-di-tert-butyl-1,3-dioxolane) sodium salt, perfluoro(2,4-di-n-pentyl-1,3-dioxolane) sodium salt, perfluoro(2,4-di-n-hexyl-1,3-dioxolane) sodium salt, perfluoro(1,3-dioxolane) potassium salt, perfluoro(2,4-dimethyl-1,3-dioxolane) potassium salt, perfluoro(2,4-diethyl-1,3-dioxolane) potassium salt, perfluoro(2,4-di-n-propyl-1,3-dioxolane) potassium salt sodium salt, perfluoro(2,4-di-n-butyl-1,3-dioxolane) potassium salt, perfluoro(2,4-di-sec-butyl-1,3-dioxolane) potassium salt, perfluoro(2,4-di-tert-butyl-1,3-dioxolane) potassium salt, perfluoro(2,4-di-n-pentyl-1,3-dioxolane) potassium salt, perfluoro(2,4-di-n-hexyl-1,3-dioxolane) potassium salt, perfluoro(1,3-dioxolane) cesium salt, perfluoro(2,4-dimethyl-1,3-dioxolane) cesium salt perfluoro(2,4-diethyl-1,3-dioxolane) cesium salt, perfluoro(2,4-di-n-propyl-1,3-dioxolane) cesium salt, perfluoro(2,4-di-n-butyl-1,3-dioxolane) cesium salt, perfluoro(2,4-di-sec-butyl-1,3-dioxolane) cesium salt, perfluoro(2,4-di-tert-butyl-1,3-dioxolane) cesium salt, perfluoro(2,4-di-n-pentyl-1,3-dioxolane) cesium salt, perfluoro(2,4-di-n-hexyl-1,3-dioxolane) cesium salt, etc.

[0037] The amount of the difluoromethyl compound represented by formula (3) used is preferably 0.1 to 1 times the total mass of the perfluoro(1,3-dioxolane)-2-carboxylic acid fluoride represented by formula (1) and / or the perfluoro(2-hydroxymethyl-1,3-dioxolane) salt represented by formula (2) used in the reaction.

[0038] It is presumed that the difluoromethyl compound represented by formula (3) does not participate in the reaction in the step of obtaining the reaction product. Therefore, the difluoromethyl compound represented by formula (3) can be contained in the composition after the reaction, i.e., in the composition containing the perfluoro(1,3-dioxolane)-2-carboxylate represented by formula (4). The content of the difluoromethyl compound represented by formula (3) in the composition containing the perfluoro(1,3-dioxolane)-2-carboxylate represented by formula (4) obtained after the reaction is preferably 0.1 to 1 times the mass of the perfluoro(1,3-dioxolane)-2-carboxylate represented by formula (4).

[0039] The perfluoro(1,3-dioxolane)-2-carboxylic acid fluoride represented by formula (1) and / or the perfluoro(2-hydroxymethyl-1,3-dioxolane) salt represented by formula (2) is reacted with the basic aqueous solution at a temperature of -10°C to 100°C, preferably 0°C to 50°C. The reaction is carried out at this temperature range, preferably for 1 hour to 24 hours, to produce the perfluoro(1,3-dioxolane)-2-carboxylic acid salt represented by formula (4). In the present invention and this specification, the temperature described in relation to the reaction is the liquid temperature of the reaction liquid, unless otherwise specified.

[0040] The basic aqueous solution can be prepared by dissolving one or more basic compounds selected from the group consisting of alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal carbonates, alkaline earth metal carbonates, alkali metal bicarbonates, and alkaline earth metal bicarbonates in water. Examples of the basic compound include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, and cesium hydroxide; alkaline earth metal hydroxides such as magnesium hydroxide and calcium hydroxide; alkali metal carbonates such as sodium carbonate, potassium carbonate, and cesium carbonate; alkaline earth metal carbonates such as magnesium carbonate and calcium carbonate; alkali metal bicarbonates such as sodium bicarbonate, potassium bicarbonate, and cesium bicarbonate; and alkaline earth metal bicarbonates such as magnesium bicarbonate and calcium bicarbonate. The basic compound is preferably an alkali metal hydroxide or an alkali metal carbonate. The amount of the basic compound used is preferably 0.1 to 5.0 molar amounts, more preferably 0.8 to 3 molar amounts, relative to the total amount of perfluoro(1,3-dioxolane)-2-carboxylic acid fluoride represented by formula (1) and / or perfluoro(2-hydroxymethyl-1,3-dioxolane) salt represented by formula (2). The water used to dissolve the basic compound is not particularly limited, and may be, for example, tap water, ion-exchanged water, or distilled water.

[0041] The organic solvent is not particularly limited as long as it is inert to the reaction. Examples of the organic solvent include aromatic solvents such as toluene, ethylbenzene, xylene, and mesitylene, and ether solvents such as ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether. The organic solvent may be used alone or in a mixture of two or more in any ratio. Among these, it is preferable to use ether solvents such as ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether alone or in a mixture of two or more in any ratio. The amount of the organic solvent used is not particularly limited. For example, the organic solvent can be used in an amount of 0.3 to 10.0 parts by mass relative to the total mass of perfluoro(1,3-dioxolane)-2-carboxylic acid fluoride represented by formula (1) and / or perfluoro(2-hydroxymethyl-1,3-dioxolane) salt represented by formula (2) used in the reaction.

[0042] The perfluoro(1,3-dioxolane)-2-carboxylate represented by the above formula (4) can be converted to perfluoro(2-methylene-4-methyl-1,3-dioxolane) by reacting it according to the description in US Pat. No. 3,308,107.

[0043] [Decomposition suppression method] A method for inhibiting decomposition according to one embodiment of the present invention relates to a method for inhibiting decomposition of perfluoro(1,3-dioxolane)-2-carboxylate, comprising the step of reacting perfluoro(1,3-dioxolane)-2-carboxylic acid fluoride represented by formula (1) and / or perfluoro(2-hydroxymethyl-1,3-dioxolane) salt represented by formula (2) with a basic aqueous solution in the presence of a difluoromethyl compound represented by formula (3) and an organic solvent to convert it into perfluoro(1,3-dioxolane)-2-carboxylate represented by formula (4), thereby obtaining a reaction product.

[0044] The perfluoro(1,3-dioxolane)-2-carboxylic acid fluoride represented by formula (1), the perfluoro(2-hydroxymethyl-1,3-dioxolane) salt represented by formula (2), the difluoromethyl compound represented by formula (3), the perfluoro(1,3-dioxolane)-2-carboxylic acid salt represented by formula (4), the organic solvent, and the basic aqueous solution in the above-mentioned decomposition suppression method are as described above in relation to the above-mentioned production method.

[0045] In the above-mentioned decomposition suppression method, the difluoromethyl compound represented by the above-mentioned formula (3) is preferably contained in an amount of 0.1 to 1 times (meaning 0.1 times or more and 1 times or less) the mass of the perfluoro(1,3-dioxolane)-2-carboxylate represented by the above-mentioned formula (4).

[0046] Furthermore, in the above-mentioned decomposition suppression method, it is particularly preferable that the difluoromethyl compound represented by formula (3) is one or more difluoromethyl compounds selected from the group consisting of difluoromethylbenzene, 1-difluoromethyl-4-methylbenzene, 1-difluoromethyl-4-ethylbenzene, 1-difluoromethyl-4-methoxybenzene, and 1-difluoromethyl-4-ethoxybenzene.

[0047] [Composition] One aspect of the present invention relates to a composition containing a perfluoro(1,3-dioxolane)-2-carboxylate represented by the above formula (4), a difluoromethyl compound represented by the above formula (3), and an organic solvent.

[0048] The perfluoro(1,3-dioxolane)-2-carboxylate represented by formula (4), the difluoromethyl compound represented by formula (3), and the organic solvent in the composition are as described above in relation to the production method.

[0049] The difluoromethyl compound represented by the above formula (3) includes one or more difluoromethyl compounds selected from the group consisting of difluoromethylbenzene, 1-difluoromethyl-4-methylbenzene, 1-difluoromethyl-4-ethylbenzene, 1-difluoromethyl-4-methoxybenzene, and 1-difluoromethyl-4-ethoxybenzene.

[0050] The organic solvent may be one or more ether solvents selected from the group consisting of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether.

[0051] The content of the difluoromethyl compound represented by formula (3) in the composition is preferably 0.1 to 1 times (meaning 0.1 times or more and 1 times or less) the mass of the perfluoro(1,3-dioxolane)-2-carboxylate represented by formula (4).

[0052] The content of the organic solvent in the composition is preferably 0.5 to 20 times (meaning 0.5 to 20 times) the mass of the perfluoro(1,3-dioxolane)-2-carboxylate represented by formula (4).

[0053] The composition may contain components other than the perfluoro(1,3-dioxolane)-2-carboxylic acid salt represented by formula (4), the difluoromethyl compound represented by formula (3), and the organic solvent. Such components include the perfluoro(1,3-dioxolane)-2-carboxylic acid fluoride represented by formula (1), the perfluoro(2-hydroxymethyl-1,3-dioxolane) salt represented by formula (2), which are used as raw materials, the alkali metal hydroxide salt, alkaline earth metal hydroxide salt, alkali metal carbonate salt, alkaline earth metal carbonate salt, alkali metal bicarbonate salt, and alkaline earth metal bicarbonate salt used in the basic aqueous solution, and the alkali metal fluoride and alkaline earth metal fluoride produced after the reaction. [Example]

[0054] The present invention will be further described below with reference to examples, but the present invention is not limited to the embodiments shown in the examples.

[0055] The following instruments were used in the following analyses: 19 F NMR: Bruker AVANCE II 400

[0056] [Reaction rate] In the following Examples and Comparative Examples, the decomposition of perfluoro(1,3-dioxolane)-2-carboxylate was considered to be a first-order reaction, and the decomposition rate was calculated from the following first-order reaction rate equation. lnC=lnC0-kt (1) C0: initial concentration C: Concentration after the elapsed time k: decomposition rate constant t: elapsed time

[0057] [Reference example 1] Preparation of 2-[perfluoro(2,4-dimethyl-1,3-dioxolane)]carboxylic acid fluoride [Formula (1)] and perfluoro(2-hydroxymethyl-2,4-dimethyl-1,3-dioxolane) cesium salt [Formula (2)] A 10-liter SUS316 autoclave (pressure-resistant vessel) equipped with a stirrer and a raw material supply port and rated to withstand a pressure of 10 MPa was charged with 4-methoxybenzaldehyde (1425 g, 10.5 mol) and heated to 90°C. While maintaining the same temperature, hexafluoropropylene oxide (1810 g, 10.9 mol) was continuously supplied as a gas through the raw material supply port over a period of 3 hours. The raw material supply port was closed, and the mixture was maintained at the same temperature for 2 hours, after which the temperature was increased to 140°C. After heating at 140°C for 16 hours, the mixture was cooled to room temperature. Subsequently, cesium fluoride (197 g, 1.3 mol) and diethylene glycol dimethyl ether (1175 g) were charged to the reaction mixture, and the mixture was cooled to 0°C in an ice bath. Next, while maintaining the temperature at 0°C, hexafluoropropylene oxide (1655 g, 10.0 mol) was continuously fed as a gas from the raw material feed port over 6 hours, and then the mixture was heated to 120°C and reacted for 24 hours. After the reaction was completed, the mixture was cooled to room temperature to obtain a solution containing 2-[perfluoro(2,4-dimethyl-1,3-dioxolane)]carboxylic acid fluoride and perfluoro(2-hydroxymethyl-2,4-dimethyl-1,3-dioxolane) cesium salt. Benzotrifluoride was used as an internal standard. 19 Quantitative analysis by F-NMR revealed that the fluorous layer contained 1893 g (6.1 mol) of 2-[perfluoro(2,4-dimethyl-1,3-dioxolane)]carboxylic acid fluoride, and the organic layer contained 541 g (1.2 mol) of perfluoro(2-hydroxymethyl-2,4-dimethyl-1,3-dioxolane) cesium salt. The organic layer also contained 1-difluoromethyl-4-methoxybenzene [formula (3)].

[0058] [Example 1] Method for preparing potassium salt of 2-[perfluoro(2,4-dimethyl-1,3-dioxolane)]carboxylic acid containing 1-difluoromethyl-4-methoxybenzene Potassium hydroxide (purity 85% by mass, 25.3 g, 383 mmol) and ion-exchanged water (82.5 mL) were placed in a 500 mL three-necked glass round-bottom flask equipped with a stirrer and a dropping funnel, dissolved with stirring, and then cooled to 0° C. in an ice bath. Next, 54.4 g of the fluorous layer obtained by the production method of Reference Example 1 (2-[perfluoro(2,4-dimethyl-1,3-dioxolane)]carboxylic acid fluoride content 29.9 g (96.6 mmol)) and 79.1 g of the organic layer (perfluoro(2-hydroxymethyl-2,4-dimethyl-1,3-dioxolane) cesium salt content 13.8 g (29.9 mmol), 1-difluoromethyl-4-methoxybenzene content 39.41 g) were added dropwise at the same temperature, followed by stirring at the same temperature for 1 hour, settling for 1 hour, and then separating the layers. Next, diethylene glycol dimethyl ether (38.7 g) and 40% aqueous potassium carbonate solution (88.4 g) were added to the separated organic layer, and the mixture was stirred for 30 minutes, settled, and then separated. The obtained organic layer was placed in a 500 mL three-necked round-bottom glass flask equipped with a vacuum distillation apparatus, heated to 45°C, and then gradually reduced in pressure, finally concentrating under reduced pressure at 1.4 kPa. The solution (116 g) obtained by vacuum concentration was analyzed using benzotrifluoride as an internal standard substance. 19 F-NMR analysis revealed that the diethylene glycol dimethyl ether solution (composition) contained 43.4 g (125 mmol, 99% yield, 37.3% by mass) of potassium 2-[perfluoro(2,4-dimethyl-1,3-dioxolane)]carboxylate and 11.9 g (10.2% by mass) of 1-difluoromethyl-4-methoxybenzene. This solution was heated at 45°C for 40 hours, and the solution after heating was analyzed using benzotrifluoride as an internal standard. 19 F-NMR measurement revealed that the concentration of potassium 2-[perfluoro(2,4-dimethyl-1,3-dioxolane)]carboxylate was 35.9% by mass. The decomposition rate calculated according to the first-order reaction rate equation was 9.6 × 10 -4 (h -1 ) was. 19 F NMR (DO, 376 MHz) (2-[perfluoro(2,4-dimethyl-1,3-dioxolane)]carboxylic acid potassium salt) δ -77.9(m), -78.0(m), -78.3(m), -78.4(d), -83.0(d), -83.4(d), -83.7(d), -84.1(d) (2F,CF2), -81.2(m), -81.3(m) (6F,CF3), -123.0(m), -124.0(m) (1F,CF) (1-Difluoromethyl-4-methoxybenzene) δ-107.0 (d, J=56.4Hz)

[0059] [Example 2] Method for preparing potassium salt of 2-[perfluoro(2,4-dimethyl-1,3-dioxolane)]carboxylic acid containing 1-difluoromethyl-4-methoxybenzene Potassium hydroxide (purity 85% by mass, 264 g, 4.00 mol) and ion-exchanged water (633 mL) were placed in a 3 L three-necked glass round-bottom flask equipped with a stirrer and a dropping funnel, dissolved with stirring, and then cooled to 0° C. in an ice bath. Next, 587 g of the fluorous layer (containing 436 g (1.41 mol) of 2-[perfluoro(2,4-dimethyl-1,3-dioxolane)]carboxylic acid fluoride) obtained by the production method of Reference Example 1 and 791 g of the organic layer (containing 124 g (0.27 mol) of perfluoro(2-hydroxymethyl-2,4-dimethyl-1,3-dioxolane) cesium salt and 398 g of 1-difluoromethyl-4-methoxybenzene) were added dropwise at the same temperature, followed by stirring at the same temperature for 1 hour, settling for 1 hour, and then separating the layers. Next, diethylene glycol dimethyl ether (638 g) and 40% aqueous potassium carbonate solution (1159 g) were added to the separated organic layer, and the mixture was stirred for 30 minutes, settled, and then separated. The obtained organic layer was placed in a 3 L glass three-necked round-bottom flask equipped with a vacuum distillation apparatus, heated to 45°C, gradually reduced in pressure, and finally concentrated under reduced pressure at 1.4 kPa. The solution (1428 g) obtained by vacuum concentration was analyzed using benzotrifluoride as an internal standard substance. 19F-NMR analysis revealed that the diethylene glycol dimethyl ether solution (composition) contained 558 g (1.61 mol, 96% yield, 39.1% by mass) of potassium 2-[perfluoro(2,4-dimethyl-1,3-dioxolane)]carboxylate. 153 g (10.7% by mass) of 1-difluoromethyl-4-methoxybenzene was also contained. This solution was heated at 45°C for 50 hours, and the solution after heating was analyzed using benzotrifluoride as an internal standard. 19 F-NMR measurement revealed that the concentration of potassium 2-[perfluoro(2,4-dimethyl-1,3-dioxolane)]carboxylate was 37.0% by mass. The decomposition rate calculated according to the first-order reaction rate equation was 1.1 × 10 -3 (h -1 ) was.

[0060] [Comparative Example 1] Potassium carbonate (0.86 kg, 6.20 mol) and water (2.01 L) were placed in a 10 L three-necked glass round-bottom flask equipped with a stirrer and a dropping funnel, dissolved with stirring, and then cooled to 0°C in an ice bath. The fluorous layer (2.06 kg, 2-[perfluoro(2,4-dimethyl-1,3-dioxolane)]carboxylic acid fluoride content: 1.67 kg, 5.40 mol) of the reaction mixture obtained in Reference Example 1 was then added dropwise at the same temperature. The mixture was stirred at the same temperature for an additional hour, allowed to settle for another hour, and the lower layer was separated. Diethylene glycol dimethyl ether (2.69 kg) and a 30% aqueous potassium carbonate solution (1.83 kg) were then added to the separated organic layer, stirred for 30 minutes, allowed to settle, and then separated. The obtained organic layer was placed in a 3 L glass three-necked round-bottom flask equipped with a vacuum distillation apparatus, heated to 45°C, and then gradually reduced in pressure, finally concentrating under reduced pressure at 1.4 kPa. The solution obtained by vacuum concentration was analyzed using benzotrifluoride as an internal standard substance. 19 F-NMR measurement revealed that the solution contained 1.77 kg (5.10 mol, yield 95%, concentration 39.8 mass%) of potassium 2-[perfluoro(2,4-dimethyl-1,3-dioxolane)]carboxylate.19 F-NMR measurement revealed that the concentration was below the detection limit. Next, 1.14 g of diethylene glycol dimethyl ether was added to 7.87 g of a solution containing 39.8% by mass of potassium 2-[perfluoro(2,4-dimethyl-1,3-dioxolane)]carboxylate to obtain a solution containing 34.7% by mass of potassium 2-[perfluoro(2,4-dimethyl-1,3-dioxolane)]carboxylate. This solution was heated at 45°C for 33 hours, and the heated solution was analyzed using benzotrifluoride as an internal standard. 19 F-NMR measurement revealed that the concentration of potassium 2-[perfluoro(2,4-dimethyl-1,3-dioxolane)]carboxylate was 33.0% by mass. The decomposition rate calculated according to the first-order reaction rate equation was 1.5 × 10 -3 (h -1 ) was.

[0061] Comparative Example 2 Method for preparing potassium 2-[perfluoro(2,4-dimethyl-1,3-dioxolane)]carboxylic acid 0.98 g of diethylene glycol dimethyl ether was added to 7.27 g of a solution of 2-[perfluoro(2,4-dimethyl-1,3-dioxolane)]carboxylic acid potassium salt with a concentration of 39.8 mass%, obtained by the same procedure as in Comparative Example 1, to obtain a solution of 2-[perfluoro(2,4-dimethyl-1,3-dioxolane)]carboxylic acid potassium salt with a concentration of 35.2 mass%. This solution was heated at 45°C for 33 hours, and the solution after heating was analyzed using benzotrifluoride as an internal standard substance. 19 F-NMR measurement revealed that the concentration of potassium 2-[perfluoro(2,4-dimethyl-1,3-dioxolane)]carboxylate was 33.4% by mass. The decomposition rate calculated according to the first-order reaction rate equation was 1.6 × 10 -3 (h -1 ) was.

[0062] Comparative Example 3 Method for preparing potassium 2-[perfluoro(2,4-dimethyl-1,3-dioxolane)]carboxylic acid 0.33 g of diethylene glycol dimethyl ether was added to 7.40 g of a solution of 2-[perfluoro(2,4-dimethyl-1,3-dioxolane)]carboxylic acid potassium salt with a concentration of 39.8 mass%, obtained by the same procedure as in Comparative Example 1, to obtain a solution of 2-[perfluoro(2,4-dimethyl-1,3-dioxolane)]carboxylic acid potassium salt with a concentration of 38.1 mass%. This solution was heated at 45°C for 33 hours, and the solution after heating was analyzed using benzotrifluoride as an internal standard substance. 19 F-NMR measurement revealed that the concentration of potassium 2-[perfluoro(2,4-dimethyl-1,3-dioxolane)]carboxylate was 36.4% by mass. The decomposition rate calculated according to the first-order reaction rate equation was 1.4 × 10 -3 (h -1 ) was.

[0063] The results of Example 1, Example 2, Comparative Example 1, Comparative Example 2, and Comparative Example 3 are shown in Table 1. From the results shown in Table 1, the following points can be confirmed. The solutions containing 1-difluoromethyl-4-methoxybenzene (Examples 1 and 2) have a slower decomposition rate than the solutions not containing it (Comparative Examples 1 to 3). Comparing Example 1 and Comparative Example 1 with respect to this difference in decomposition rate, for example, when a solution of potassium 2-[perfluoro(2,4-dimethyl-1,3-dioxolane)]carboxylate is heated at 45°C for 72 hours, the concentration change rate of potassium 2-[perfluoro(2,4-dimethyl-1,3-dioxolane)]carboxylate in the solution not containing 1-difluoromethyl-4-methoxybenzene is calculated to be 93%, whereas the concentration change rate of potassium 2-[perfluoro(2,4-dimethyl-1,3-dioxolane)]carboxylate in the solution containing 1-difluoromethyl-4-methoxybenzene is calculated to be 90%.

[0064] [Table 1]

[0065] The perfluoro(1,3-dioxolane)-2-carboxylate obtained according to one embodiment of the present invention can be used as a raw material for synthesizing resins for gas separation membranes and the like.

Claims

1. Formula (1): 【Chemical 1】 [In formula (1), two R １ are the same and represent a fluorine atom or a perfluoroalkyl group having 1 to 6 carbon atoms. and / or perfluoro(1,3-dioxolane)-2-carboxylic acid fluoride represented by the formula: Formula (2): 【Chemistry 2】 [In formula (2), two R １ has the same meaning as above. ＋ represents a counter cation. A perfluoro(2-hydroxymethyl-1,3-dioxolane) salt represented by Formula (3) 【Chemistry 3】 [In formula (3), Ar １ represents an aryl group having 6 to 10 carbon atoms which may be substituted with one or more groups selected from the group consisting of an alkyl group having 1 to 6 carbon atoms, a fluorine atom, a chlorine atom, a bromine atom, a methoxy group, an ethoxy group, and a phenyl group.] and an organic solvent, Formula (4): 【Chemistry 4】 [In formula (4), two R １ and M ＋ has the same meaning as above.] and obtaining a reaction product by converting the compound represented by the formula (I) into a perfluoro(1,3-dioxolane)-2-carboxylate represented by the formula (I).

2. The method for producing perfluoro(1,3-dioxolane)-2-carboxylate according to claim 1, wherein the difluoromethyl compound represented by formula (3) is contained in an amount of 0.1 to 1 times the mass of the perfluoro(1,3-dioxolane)-2-carboxylate represented by formula (4).

3. The method for producing perfluoro(1,3-dioxolane)-2-carboxylate according to claim 1 or 2, wherein the difluoromethyl compound represented by formula (3) is one or more difluoromethyl compounds selected from the group consisting of difluoromethylbenzene, 1-difluoromethyl-4-methylbenzene, 1-difluoromethyl-4-ethylbenzene, 1-difluoromethyl-4-methoxybenzene, and 1-difluoromethyl-4-ethoxybenzene.

4. The method for producing perfluoro(1,3-dioxolane)-2-carboxylate according to claim 1 or 2, wherein the organic solvent is one or more ether solvents selected from the group consisting of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether.

5. The method for producing perfluoro(1,3-dioxolane)-2-carboxylate according to claim 1 or 2, wherein the basic aqueous solution is an aqueous solution prepared by dissolving one or more basic compounds selected from the group consisting of alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal carbonates, alkaline earth metal carbonates, alkali metal bicarbonates, and alkali metal bicarbonates.

6. The method for producing perfluoro(1,3-dioxolane)-2-carboxylate according to claim 5, wherein the basic compound is one or more basic compounds selected from the group consisting of alkali metal hydroxides and alkali metal carbonates.

7. M in the formula (4) ＋ The method for producing perfluoro(1,3-dioxolane)-2-carboxylate according to claim 1 or 2, wherein is an alkali metal cation and / or an alkaline earth metal cation.

8. Formula (1): 【Chemistry 5】 [In formula (1), two R １ are the same and represent a fluorine atom or a perfluoroalkyl group having 1 to 6 carbon atoms. and / or perfluoro(1,3-dioxolane)-2-carboxylic acid fluoride represented by the formula: Formula (2): 【Chemistry 6】 [In formula (2), two R １ has the same meaning as above. ＋ represents a counter cation. A perfluoro(2-hydroxymethyl-1,3-dioxolane) salt represented by Formula (3) 【Chemistry 7】 [In formula (3), Ar １ represents an aryl group having 6 to 10 carbon atoms which may be substituted with one or more groups selected from the group consisting of an alkyl group having 1 to 6 carbon atoms, a fluorine atom, a chlorine atom, a bromine atom, a methoxy group, an ethoxy group, and a phenyl group.] and an organic solvent, Formula (4): 【Chemistry 8】 [In formula (4), two R １ and M ＋ has the same meaning as above.] The method for inhibiting decomposition of perfluoro(1,3-dioxolane)-2-carboxylate includes a step of converting the compound represented by formula (1) into a perfluoro(1,3-dioxolane)-2-carboxylate represented by formula (1):

9. The method for suppressing decomposition of perfluoro(1,3-dioxolane)-2-carboxylate according to claim 8, wherein the difluoromethyl compound represented by formula (3) is contained in an amount of 0.1 to 1 times the mass of the perfluoro(1,3-dioxolane)-2-carboxylate represented by formula (4).

10. The method for suppressing decomposition of perfluoro(1,3-dioxolane)-2-carboxylate according to claim 8 or 9, wherein the difluoromethyl compound represented by formula (3) is one or more difluoromethyl compounds selected from the group consisting of difluoromethylbenzene, 1-difluoromethyl-4-methylbenzene, 1-difluoromethyl-4-ethylbenzene, 1-difluoromethyl-4-methoxybenzene, and 1-difluoromethyl-4-ethoxybenzene.

11. The following formula (4): 【Chemistry 9】 [In formula (4), two R １ are the same and represent a fluorine atom or a perfluoroalkyl group having 1 to 6 carbon atoms. ＋ represents a counter cation. Perfluoro(1,3-dioxolane)-2-carboxylate represented by the formula: The following formula (3): 【Chemistry 10】 [In formula (3), Ar １ represents an aryl group having 6 to 10 carbon atoms which may be substituted with one or more groups selected from the group consisting of an alkyl group having 1 to 6 carbon atoms, a fluorine atom, a chlorine atom, a bromine atom, a methoxy group, an ethoxy group, and a phenyl group.] Difluoromethyl compounds represented by the formula: organic solvents, A composition comprising:

12. The composition according to claim 11, comprising the difluoromethyl compound represented by formula (3) in an amount of 0.1 to 1 times the mass of the perfluoro(1,3-dioxolane)-2-carboxylate represented by formula (4).

13. The composition according to claim 11 or 12, wherein the difluoromethyl compound represented by formula (3) is one or more difluoromethyl compounds selected from the group consisting of difluoromethylbenzene, 1-difluoromethyl-4-methylbenzene, 1-difluoromethyl-4-ethylbenzene, 1-difluoromethyl-4-methoxybenzene, and 1-difluoromethyl-4-ethoxybenzene.

14. 13. The composition according to claim 11 or 12, wherein the organic solvent is one or more ether solvents selected from the group consisting of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether.

15. M in the formula (4) ＋ 13. The composition of claim 11 or claim 12, wherein is an alkali metal cation and / or an alkaline earth metal cation.

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