JPH11189566A - Method for producing fluoroalkylcarboxylic acid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for obtaining a fluoroalkylcarboxylic acid from a corresponding fluoroalkylcarboxylic acid chloride by hydrolysis, wherein the generated fluoroalkylcarboxylic acid can be easily separated and purified. SOLUTION: The formula: H (CF ₂ CF ₂ ) _n COCl (wherein,
n is a number from 1 to ) By hydrolyzing the fluoroalkylcarboxylic acid chloride represented by the formula:
In a method for producing a fluoroalkylcarboxylic acid represented by H (CF ₂ CF ₂ ) _n COOH (wherein n is as defined above), the reaction mixture is treated with an aqueous hydrochloric acid layer under acidic conditions. Separated into an alkyl carboxylic acid layer,
The fluoroalkyl carboxylic acid is recovered.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a fluoroalkylcarboxylic acid. Fluoroalkylcarboxylic acids are industrially useful compounds as raw materials for surfactants, medical and agricultural chemicals, and the like.

[0002]

2. Description of the Related Art A carboxylic acid synthesis method is one of important reaction techniques in synthetic organic chemistry, and many carboxylic acid synthesis methods have been studied. For example, a method of synthesizing a carboxylic acid by oxidizing an alcohol, an aldehyde, or the like includes an oxygen oxidation reaction using a solid catalyst; an oxidation reaction using an oxidizing agent such as chromic acid, potassium permanganate, and nitric acid; and a liquid phase autoxidation reaction. It is known (for example, for oxygen oxidation using a solid catalyst, see US Pat. No. 5,495,034;
Heyns, L. Blazejewicz, Tetrahedoron, 9, 67 (1960); For oxidation with chromic acid, see CDHurd, RN Meinert, "Or.
ganic Syntheses ", Col.Vol.II, p541, John Wiley & Son
s, New York (1948); For oxidation by potassium permanganate, see K. Saotome, T. Yamazaki, Bull. Chem. Soc. Jpn.,
36,1264 (1963); For oxidation by nitric acid, see EJStroj
ny, RTIwamasa, LKFrevel, J.Am.Chem.Soc., 93,1171 (1
971); For the liquid phase autoxidation reaction, see GOSchenck, H.-
D.Becker, K.-H.Schulte-Elte, CHKrauch, Chem.Ber., 9
6,509 (1963)). However, there are problems that the solid catalyst is expensive, that it may be difficult to selectively convert to a carboxylic acid, and that the oxidizing agent is often toxic. When carboxylic acid halides or carboxylic acid anhydrides are inexpensive and readily available, these compounds can be easily hydrolyzed to carboxylic acids using water and can be easily purified (for example, HKHall, Jr.). ., CHLue
ck, J. Org. Chem., 28, 2818 (1963)). However, when the carboxylic acid generated by the hydrolysis reaction is easily dissolved in water, it becomes difficult to separate and purify the carboxylic acid.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a process for producing a fluoroalkylcarboxylic acid which does not have the above-mentioned problems of the prior art.

[0004]

Means for Solving the Problems The present inventors obtained fluoroalkyl carboxylic acid chloride by reacting fluoroalkyl alcohol with chlorine in the presence of an activated carbon catalyst (Japanese Patent Application No. 8-345083). When this acid chloride is hydrolyzed, at the end of the reaction, it is separated into a hydrochloric acid aqueous solution layer formed by absorption of hydrogen chloride by-produced by water and a fluoroalkylcarboxylic acid layer obtained by hydrolysis. It has been found that by separation, the corresponding fluoroalkylcarboxylic acid can be recovered quantitatively.

That is, the present invention hydrolyzes a fluoroalkyl carboxylic acid chloride represented by the formula: H (CF ₂ CF ₂ ) _n COCl (I), wherein n is a number of 2 to 8. Thus, in the method for producing a fluoroalkylcarboxylic acid represented by the formula: H (CF ₂ CF ₂ ) _n COOH (II) (wherein n is as defined above), the reaction mixture is treated under acidic conditions. The present invention provides a method for producing a fluoroalkyl carboxylic acid, which comprises separating an aqueous hydrochloric acid layer and a fluoroalkyl carboxylic acid layer, and recovering the fluoroalkyl carboxylic acid.

In the method of the present invention, a fluoroalkyl carboxylic acid chloride (I) is hydrolyzed to obtain a fluoroalkyl carboxylic acid (II). Hydrogen chloride generated as a by-product in the hydrolysis reaction in an amount of 1 mol per 1 mol of acid chloride is absorbed by water to form an aqueous hydrochloric acid solution. As a result, the reaction system becomes acidic, and the fluoroalkylcarboxylic acid is separated exclusively as a lower layer. By separating the reaction mixture separated into two layers, fluoroalkylcarboxylic acid (II) can be easily and quantitatively recovered. If necessary, the recovered fluoroalkylcarboxylic acid can be separated and purified by distillation or the like to obtain a highly pure fluoroalkylcarboxylic acid (II).

The amount of water used in the hydrolysis reaction is 1 to 1 mol of the fluoroalkylcarboxylic acid chloride (I).
Mol or more, preferably 2 to 10 mol. The hydrolysis reaction may be carried out in any reaction mode, for example, a method in which water is dropped into fluoroalkyl carboxylic acid chloride (I), a method in which fluoroalkyl carboxylic acid chloride (I) and water are simultaneously charged, A method of dropping the alkyl carboxylic acid chloride (I) and the like can be mentioned. The last method is preferred. The reaction temperature is 0 to 150 ° C, preferably 10 to 120 ° C. The reaction time is usually 4 to 80
The time is about time, but can be adjusted by selecting other conditions such as a charging rate of carboxylic acid chloride and the like, a reaction temperature and the like.

[0008] Hydrogen chloride by-produced is absorbed by water to form an aqueous hydrochloric acid solution, and the unabsorbed portion can be treated by a known removal method. After completion of the reaction, the fluoroalkylcarboxylic acid (I) obtained by the above-mentioned separation operation can be purified by a known method. For example, methods such as extraction, distillation, recrystallization, and column chromatography can be used.

[0009]

EXAMPLES The present invention will be specifically described below with reference to examples. Example 1 Water (50.0 g, 2777.8 mmol) was previously charged into a 300 ml four-necked flask equipped with a stirrer, a thermometer, and a dropping funnel. While stirring, the fluoroalkyl carboxylic acid chloride: H is adjusted so that the internal temperature is maintained at 70 ° C. or lower.
(CF ₂ CF ₂ ) ₃ COCl (150.0 g, 411.5 mm
ol) was added dropwise. The reaction was terminated when the disappearance of the starting carboxylic acid chloride was confirmed by gas chromatography. When the reaction mixture is left standing for about 1 hour, it separates into a hydrochloric acid aqueous solution layer and a fluoroalkyl carboxylic acid layer.
And an upper aqueous hydrochloric acid layer (39.2 g), respectively. By distilling the carboxylic acid layer, 99% -purity fluoroalkylcarboxylic acid: H (CF ₂ CF ₂ ) ₃ COO
H (106.8 g, 308.7 mmol) was obtained in an isolated yield of 7
Obtained at 5.0%.

Claims (1)

[Claims] 1. A hydroalkyl carboxylic acid chloride represented by the formula: H (CF ₂ CF ₂ ) _n COCl (where n is a number of 2 to 8) is hydrolyzed to obtain a compound represented by the formula: H ( In a method for producing a fluoroalkylcarboxylic acid represented by the formula: CF ₂ CF ₂ ) _n COOH (wherein n is as defined above), the reaction mixture is mixed under acidic conditions with a hydrochloric acid aqueous solution layer and a fluoroalkyl carboxylic acid. A method for producing a fluoroalkylcarboxylic acid, comprising separating the fluoroalkylcarboxylic acid from an acid layer and collecting the fluoroalkylcarboxylic acid.