JPS60243039A - Production of oxalyl fluoride - Google Patents

Abstract

PURPOSE:To produce oxalyl fluoride useful as a raw material for the production of various organofluorine compounds, easily, in high yield, by fluorinating oxalyl chloride with hydrogen fluoride in the presence of pyridine. CONSTITUTION:Oxalyl fluoride is produced by fluorinating oxalyl chloride with hydrogen fluoride in the presence of a pyridine compound such as pyridine, methylpyridine, dimethylpyridine, ethylpyridine, trimethylpyridine, ethylmethylpyridine, tetramethylpyridine, etc. The concentration of the pyridine compound in hydrogen fluoride is 1-50mol%, preferably 3-25mol%. The hydrogen fluoride solution containing pyridine compound has extremely low vapor pressure compared with hydrogen fluoride and is stable at a relatively high temperature, and accordingly, the evaporation loss of hydrogen fluoride can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for easily producing oxalyl fluoride from oxalyl chloride with high yield.

Oxalyl fluoride is a substance useful as a raw material for producing various organic fluorine compounds such as barfluorodivinyl ether. Furthermore, as a method for producing oxalyl fluoride, a method of fluorinating oxalyl chloride is known.

As the fluorinating agent for fluorinating the above-mentioned oxalyl chloride, an alkali metal fluoride such as NaFKF is usually used. In this case, the alkali metal fluoride is sulfolane,
The reaction is carried out in a state in which the reaction mixture is uniformly suspended in an appropriate neutral solvent such as tetraglyme, 7-cetonitrile, etc., and the temperature of the reaction system is generally relatively high, up to 130°C. However, this method has the disadvantage that since the reaction proceeds at the solid-liquid interface, the reaction is very slow even if an alkali metal fluoride with a sufficiently small particle size is used.

Furthermore, although alkali metal fluorides are expensive reagents, only a portion of their usage is effectively consumed, which poses a major industrial problem. Furthermore, not only is the yield of the reaction low, but also the reaction temperature is high, so fluorinated phosgene is likely to be produced as a by-product. On the other hand, as a fluorinating agent, hydrogen fluoride is extremely cheap, but since it separates into two phases that are uniformly mixed with oxalyl chloride, it shows no reactivity towards oxalyl chloride, and does not substantially remove oxalyl fluoride. cannot be manufactured.

Therefore, the present inventors have discovered that by a method of reacting oxalyl chloride and hydrogen fluoride under stirring conditions that are more vigorous than the reaction activity limit stirring, the desired oxalyl fluoride can be produced efficiently without the by-product of phosgene fluoride. We found that this method can be obtained well and have already proposed it (Japanese Unexamined Patent Publication No. 57-67533).

Similarly, we have already discovered that the desired oxalyl fluoride can be obtained in good yield by simply reacting oxalyl chloride and hydrogen fluoride in the gas phase, and have already proposed it (Japanese Patent Application No. 58-244411). . However, in each of these proposed methods, the former requires special stirring conditions, which not only complicates the equipment, but also makes it cumbersome to determine specific stirring conditions in advance, and the latter requires a theoretical Since hydrogen fluoride is required in excess of the amount, it is troublesome to separate the hydrogen fluoride accompanying the generated gas, and additional equipment such as a vaporizer is required.

On the other hand, JP-A-54-158396 proposes a method for producing oyasalyl fluoride by fluorinating oxalyl chloride using hydrogen fluoride in the presence of acetonitrile.
The yield is over 70%, which is still not satisfactory.

In view of the above, the present inventors have conducted further research on the fluorination of oxalyl chloride in the presence of various additives such as primary to tertiary asnes and aprotic polar compounds to hydrogen fluoride. I did it systematically. As a result, it was discovered that oxalyl fluoride can be obtained at a rapid reaction rate and in an extremely high yield by reacting oxalyl chloride with hydrogen fluoride, especially in the presence of pyridines, and has completed the present invention. This is what we have come to. That is, the present invention provides a method for producing oxalyl fluoride by fluorinating oxalyl chloride with hydrogen fluoride, which is characterized in that the fluorination is carried out using hydrogen fluoride in the presence of pyridine. This is the manufacturing method. According to the invention, 80
It was confirmed that oxalyl fluoride could be obtained with a yield of 90% or more, and that the hydrogen chloride to be produced as a by-product did not combine with the pyridine, thereby causing no inconvenience to the reaction.

In order to obtain oxalyl fluoride, which is the object of the present invention, an approximately theoretical amount of 2 moles of hydrogen fluoride is required per 1 mole of oxalyl chloride. Therefore, in general, hydrogen fluoride consumed as the reaction continues can be replenished according to the theoretical amount, and hydrogen fluoride used in excess can be recovered or used for the next reaction. can. Note that when hydrogen fluoride contains water, oxalic acid is produced as a by-product during the reaction with oxalyl chloride, resulting in a decrease in the yield of the desired oxalyl fluoride. Therefore, the water content of hydrogen fluoride is generally 0.
．． It is desirable to suppress the content to 5% by weight or less, preferably 0.1% by weight or less.

In the present invention, the presence of pyridine is extremely important in order to obtain the desired oxalyl fluoride in good yield through the reaction of oxalyl chloride and oxalyl fluoride.

The pyridines of the present invention collectively refer to pyridine and its homologs, such as pyridine, methylpyridine, dimethylpyridine, and ethylpyridine.

Trimethylpyridine, ethylmethylpyridine×tetramethylpyridine, etc. are used.

In the present invention, the desired oxalyl fluoride can be obtained in good yield by generally maintaining the concentration of pyridine in hydrogen fluoride at a concentration of 1 to 50 mol%, preferably 3 to 25 mol%. I can do it. In addition, the fluoride aqueous solution containing such pyridines has a very low vapor pressure compared to hydrogen fluoride and is stable even at relatively high temperatures, so the amount of hydrogen fluoride volatilized can be reduced. Handling is advantageous because the amount of accompanying hydrogen fluoride is small. However, if the concentration of pyridines in hydrogen fluoride is lower than 1 mol%, the phase separation between the hydrogen fluoride and oxalyl chloride becomes severe, slowing down the reaction, or even preventing the reaction from occurring at all. Not only does it disappear, but due to the increase in the vapor pressure of hydrogen fluoride, hydrogen fluoride is entrained in the reaction product gas. ,
Furthermore, if the concentration of pyridine in hydrogen fluoride is higher than 50 mol%, the reaction rate will be slow, which is industrially disadvantageous.

Regarding the hydrogen fluoride solution containing the above-mentioned pyridines,
There are no particular restrictions on the preparation method, such as the order of mixing pyridines and hydrogen fluoride. Since pyridine and hydrogen fluoride generate heat when mixed, it is generally preferable to add hydrogen fluoride to pyridine and mix with cooling to adjust the concentration to a predetermined concentration.

Next, the method of reacting oxalyl chloride and pyridine in the present invention is not particularly limited as long as it is in the presence of pyridine, and the two may be mixed batchwise or continuously. Generally, it is recommended to add and mix oxalyl chloride in a liquid or gaseous state to a hydrogen fluoride solution containing the above-mentioned pyridines. A particularly industrially advantageous method is to continuously or intermittently add oxalyl chloride in a liquid or gaseous state to a pyridine-containing hydrogen fluoride solution, which is simple and has a good yield of oxalyl fluoride. .

Note that if oxalyl chloride is continuously or intermittently supplied to a hydrogen fluoride solution containing pyridines, and the reaction rate slows down as the concentration of hydrogen fluoride decreases, new hydrogen fluoride is added. The reaction rate can be restored by replenishing. The method of replenishing hydrogen fluoride is not particularly limited, and it may be added continuously in small amounts depending on the reaction rate of fluorination of oxalyl chloride during the reaction, or the reaction system may be cooled once as necessary and a predetermined amount may be added. After adding hydrogen fluoride, a method is adopted in which the reaction is restarted at a predetermined reaction temperature.

In the present invention, if the reaction temperature is too high, by-products such as phosgene fluoride are unavoidable, and if it is too low, the reaction rate becomes slow, resulting in a decrease in yield. Therefore, in general θ~10'O
Reaction temperatures of "C1, preferably 10 to 60"C are contemplated.

Furthermore, although the reaction according to the present invention can be carried out at normal pressure, elevated pressure, or reduced pressure, it is generally convenient to carry out the reaction near normal pressure. According to the reaction conditions of the present invention, the reaction rate of fluorination is extremely fast, and the reaction time is about 0.2 to 10 hours, although it varies depending on the reaction method, amount of reaction, size of reactor, etc. .

Since the oxalyl fluoride produced in the present invention has a considerably low fluoride point, it can be easily taken out from the reaction system together with hydrogen chloride as a by-product.

When the reaction temperature is made considerably low, oxalyl fluoride remaining in the reaction solution after the reaction can be taken out by appropriate heating. The resulting oxalyl fluoride and hydrogen chloride can be easily separated using the difference in boiling points. In addition, in the present invention, since the amount of hydrogen fluoride accompanying oxalyl fluoride is extremely small, it is easy to purify the oxalyl fluoride, and it can be concentrated in a cold trap by a simple separation operation such as low-temperature distillation. .

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

Example 1 Approximately 1.5 t polychlorotrifluoroethylene reactor (inner diameter 11 cm , height 1sC:m) was used.

200 g of pyridine was placed in a reactor, and 400 g of anhydrous hydrogen fluoride was slowly added under cooling to prepare a pyridine-hydrogen fluoride solution.

Next, add the pyridine-hydrogen fluoride solution to a temperature of about 2 ml under stirring.
Controlled at 5° C., 480 g of oxalyl chloride was fed at a flow rate of 3.2 min. After supply ends, 10
Stirring was continued for a minute, and then nitrogen gas was blown at a low flow rate for 15 minutes to complete the reaction in order to drive out the product remaining in the reaction solution.

Analysis of the material obtained from the dry ice-methanol trap revealed that it consisted mostly of oxalyl fluoride, with small amounts of hydrogen chloride and hydrogen fluoride. By rectifying this, 330.9 (yield 92.9%) of oxalyl fluoride was obtained. The analysis is based on IR spectrum, 1
This was carried out by measuring 8C-NMR spectrum and 19F-NMR spectrum.

Example 2 The reaction was carried out in the same manner as in Example 1 except that the amount of oxalyl chloride supplied was changed to 960 g. After completion, the reactor was cooled again and anhydrous hydrogen fluoride aooI! was replenished. This pyridine-hydrogen fluoride solution was reacted with 480 g of oxalyl chloride under the same conditions as in Example 1, followed by a separation operation. As a result, 4 g of aa (yield 94.0%) of oxalyl fluoride I got it.

Example 3 A pyridine-hydrogen fluoride solution 6009 prepared using the same reaction vessel and method as in Example 1 was cooled to -20°C, and oxalyl chloride 480Ii was added thereto. Thereafter, the temperature was raised to 25°C and stirred at 25°C for 4 hours. Then, nitrogen gas was blown at a low speed for 15 minutes to complete the reaction.

Example 1 shows the separation operation of the product obtained in the cold trap.
305 g (yield: 85.8%) of oxalyl fluoride was obtained.

patent applicant Tokuyama Soda Co., Ltd.

Claims (1)

[Claims] A method for producing oxalyl fluoride, which comprises fluorinating oxalyl chloride with hydrogen fluoride in the presence of pyridines.