JPH0699358B2 - Method for producing oxalyl fluoride - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing oxalyl fluoride from oxalyl chloride in a high yield and in a simple manner.

[Prior art and its problems]

Oxalyl fluoride is a compound useful as a starting material for producing a fluorine-containing organic compound, particularly a perfluoroalkyl vinyl ether compound. As a method for producing such oxalyl fluoride, a journal
Of Organic Chemistry (J.org.chem.) 2016,
(1960) using oxalyl chloride and sodium fluoride (NaF) in the solvent of sulfolane, reaction temperature 60 ℃ ~ 130 ℃
Is known to obtain oxalyl fluoride at a yield of 60%. Further, in JP-A-54-158396, a method of reacting oxalyl chloride with hydrogen fluoride in an acetonitrile solvent to obtain oxalyl fluoride in a yield of 69 to 74%, JP-A-57-67533. In the method of reacting oxalyl chloride with hydrogen fluoride, the reaction solution is stirred more vigorously than the reaction activity limit stirring, and in JP-A-60-139642, oxalyl chloride and hydrogen fluoride are disclosed. Method for producing oxalyl fluoride by contacting oxalyl in the gas phase, JP-A-60-2605
In Japanese Patent Publication No. 34-34, there has been proposed a method of reacting oxalyl chloride with hydrogen fluoride in the presence of melamine to obtain oxalyl fluoride at a yield of 90%.

Among these methods, the method of dispersing NaF in a sulfolane solvent and reacting it with oxalyl chloride is NaF.
Despite being used in an excessive amount, the yield of oxalyl fluoride was as low as 60%, and 60-120 ℃
That is, it has a drawback that it must be reacted at a high temperature. On the other hand, the method using hydrogen fluoride has a problem that it is difficult to handle because the boiling point of the hydrogen fluoride is 19.5 ° C., which is a toxic substance that becomes a gas at room temperature, and the boiling point of oxalyl fluoride is 0 ° C. Since hydrogen fluoride is used in an amount more than the stoichiometric amount, it is unavoidable that hydrogen fluoride is mixed into the product during separation and purification. Furthermore, it is considered that hydrogen chloride, which is a by-product, naturally enters the product. Therefore, in order to obtain highly pure oxalyl fluoride, means such as precision distillation is necessary. Although hydrogen fluoride can be recovered and reused, hydrogen chloride by-produced in this reaction must be neutralized with an alkali. That is, a method of synthesizing oxalyl fluoride from oxalyl chloride using hydrogen fluoride is also an industrially difficult method and is not yet satisfactory.

[Means for solving problems]

In view of the above, the present inventors have earnestly studied a method for producing oxalyl fluoride with good yield by using an alkali metal fluoride that is easier to handle than hydrogen fluoride and is inexpensive. As a result, by dispersing fine particles of an alkali metal fluoride of 10 μ or less in an aprotic solvent and reacting oxalyl chloride at a temperature of −10 ° C. to 50 ° C., the reaction rate is large and the yield is extremely high. The present invention has been completed by discovering that oxalyl fluoride can be obtained. That is, the present invention uses oxalyl chloride in an aprotic solvent in the form of finely divided sodium fluoride of 10 μm or less at a temperature of −10 ° C. to 50 ° C. to react the oxalyl fluoride. It is a manufacturing method. According to the present invention, oxalyl fluoride can be obtained in a yield of 90% or more.

The alkali metal fluoride used in the present invention is generally sodium fluoride or potassium fluoride,
Sodium fluoride that is industrially inexpensive and has low hygroscopicity is particularly preferably used. In the present invention, the form of the alkali metal fluoride and the reaction temperature are very important. That is, the smaller the particle shape of the alkali metal fluoride, that is,
The larger the surface area, the faster the reaction with oxalyl chloride and the higher the conversion rate of the reaction. Therefore, particles having a particle size of 10 μm or less are generally used. Therefore, in the present invention, the alkali metal fluoride having a particle size larger than 10 μm is sieved or crushed by a ball mill, and the alkali metal fluoride is put in an aprotic solvent and crushed by a ceramic or a stainless steel sphere to obtain fine particles. Recommended to use.

The amount of these alkali metal fluorides used with respect to oxalyl chloride can be brought closer to the theoretical amount as the particle size of the alkali metal fluorides becomes smaller. Generally, when the particle size is 10 μm or less, the amount of the alkali metal fluoride is 1.1 to 3 times the equivalent amount of oxalyl chloride.
On the other hand, when the particle size of the alkali metal fluoride is larger than this, the amount of the alkali metal fluoride used becomes four times or more, and the portion not used for the reaction increases, which is not an industrially advantageous method.

In addition, in the reaction of the present invention, oxalyl chloride becomes carbon dioxide, carbon oxide, and hydrochloric acid due to the presence of water, which is not preferable. Therefore, the alkali metal fluoride
It is necessary to bake and dehydrate at a high temperature of 200 to 500 ° C. Further, an aprotic solvent such as sulfolane, acetonitrile, adiponitrile, triglyme, and tetraglyme is used as the solvent, and it is desired to dehydrate the solvent by a known method to adjust the water content to 500 ppm, preferably 100 ppm. The amount of the solvent used is such that the alkali metal fluoride is sufficiently stirred. The reaction between the alkali metal fluoride of the present invention and oxalyl chloride is -10 ° C.
A temperature of ~ 50 ° C is preferred, the reaction is exothermic, 0 ° C
Although the reaction rate was high even in the vicinity, it was revealed that the conversion of oxalyl chloride to oxalyl fluoride was poor at 60 ° C or higher, and as a result, the yield of oxalyl fluoride was poor. That is, it is considered that at a high temperature, a side reaction such as the formation of carbonyl fluoride occurs. Therefore, the reaction temperature of the present invention is -10 ° C to 50 ° C, preferably 0 ° C.
To around room temperature is optimal. If the reaction is extremely exothermic, it is preferable to control the reaction temperature by a means such as cooling. The reaction pressure may be any of normal pressure, increased pressure and reduced pressure, but it is preferable to carry out the reaction under normal pressure because it is simple and easy.

According to the reaction conditions of the present invention, the conversion rate from oxalyl chloride to oxalyl fluoride is extremely fast, and the reaction time may be completed at the end of addition of oxalyl chloride, but the reaction may be completed within 1 day. It's finished.

Next, the oxalyl fluoride produced in the present invention is separated from the solvent. As a method of separation, distillation is performed under reduced pressure, normal pressure, or increased pressure. Since heating is not preferable from the stability of oxalyl fluoride, it is preferable to distill oxalyl fluoride under reduced pressure.

〔The invention's effect〕

According to the present invention, hydrogen chloride, hydrochloric acid, carbonyl fluoride and the like are not mixed in oxalyl fluoride at all or are negligible, so that high-purity oxalyl fluoride can be easily prepared by low temperature distillation. It can be obtained by operation and with an isolation yield of 90% or more.

〔Example〕

Examples will be shown below, but the invention is not limited thereto.

Example 1 130 parts by weight of sulfolane having a water content of 100 ppm dried by a molecular sieve, and an average particle size of 1-2 μ after baking at 400 ° C. for 8 hours
100 parts by weight of sodium fluoride having a specific surface area of 1 m ² / g and a magnetic stirrer are placed in a flask equipped with a magnetic stirrer, and 75 parts by weight of oxalyl chloride (sodium fluoride is used in twice the equivalent amount of oxalyl chloride) while stirring. The mixture was added dropwise over 2 hours while maintaining the reaction temperature around 30 to 40 ° C. After dripping,
When the reaction solution was analyzed using a gas chromatograph,
There were only peaks for oxalyl fluoride and sulfolane, and no peaks for oxalyl chloride. Since oxalyl chloride was completely converted to oxalyl fluoride, oxalyl fluoride was evaporated from the solvent under reduced pressure and collected in a trap immersed in dry ice / methanol. The scavenged gas was analyzed by infrared spectroscopy, there is a sharp absorption peak at 1861cm ^-1 and 1872cm ^-1, it was confirmed that the oxalyl fluoride.
The isolated yield of oxalyl fluoride was 91%.

Examples 2 to 3 100 parts by weight of sodium fluoride having a particle size of 1 to 2 μm was baked at 400 ° C., then 150 parts by weight of acetonitrile dried by molecular sieve was put into a flask, and 60 parts by weight of oxalyl chloride was stirred. Was added dropwise over 2 hours (sodium fluoride was used at 2.5 times the equivalent of oxalyl chloride). The reaction temperature was around 30 ° C. The conversion rate from oxalyl chloride to oxalyl fluoride was measured by analyzing the reaction liquid after 8 hours by gas chromatography. The results are shown in Table 1 as Example 2. Also, the results of using sodium fluoride having a particle size of 5 to 7 μm in the same manner as in Example 2 are also shown in Table 1 as Example 3.

Comparative Examples 1-2 In the same manner as in Example 2, oxalyl fluoride was produced using sodium fluoride having a particle size of 15 to 20 μm and 90 to 100 μm. The results are also shown in Table 1 as Comparative Example 1 and Comparative Example 2, respectively. From these experiments, it is clear that the reaction activity is significantly reduced when the particle size of sodium fluoride becomes large.

Examples 4-5 Dry Sodium Fluoride 10 having a particle size of 1-2 μm
To 100 parts by weight of 0 parts by weight of dried acetonitrile, 75 parts by weight of oxalyl chloride (sodium fluoride is used in an amount of 2 times equivalent to oxalyl chloride) was added dropwise over 1 hour, and 23 hours later, oxalyl fluoride was added from the reaction solvent. Ride was isolated. The results obtained by setting the reaction temperatures of 0 ° C. and 30 ° C. are shown in Table 2 as Examples 4 and 5, respectively.

Comparative Example 3 As in Example 4, what was carried out at a reaction temperature of 70 ° C. is shown in Table 2 as Comparative Example 3. It is clear that when the reaction temperature rises, the side reaction occurs and the yield is poor.

Example 6 100 parts by weight of sodium fluoride having a particle size of 5 to 7 μm baked at 400 ° C., 200 parts by weight of dried sulfolane, and 50 parts by weight of stainless steel balls having a diameter of 5 mm were placed in a stainless steel autoclave and vigorously stirred. While crushing the sodium fluoride with, 100 parts by weight of oxalyl chloride (sodium fluoride is used in 1.5 times equivalent amount of oxalyl chloride) was added dropwise over 2 hours. When the reaction liquid was analyzed by gas chromatography three hours after the dropping, it was found that oxalyl chloride had been completely converted to oxalyl fluoride. Collected inside. The isolated yield of oxalyl fluoride at that time was 91%.
Met.

Claims (1)

[Claims] 1. Oxalyl fluoride characterized by reacting oxalyl chloride in an aprotic solvent in the form of fine particles of an alkali metal fluoride of 10 μm or less at a temperature of −10 ° C. to 50 ° C. Manufacturing method.