JPH0349900B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to tetrafluoroisophthalonitrile useful for imparting flame retardancy and weather resistance to plastics.

Exchanging the halogen atoms with fluorine atoms by reacting an alkali fluoride etc. with an aromatic halide,
The so-called halogen exchange reaction has been known for a long time [for example, Ishikawa, Journal of the Society of Organic Synthetic Chemistry 25 , 808,
(1967), M. Hudlicky, Chemistry of Organic
Fluorine Compounds 112 pages (1976) John
Wiley & Sons Publishing, etc.].

However, aromatic halides that can be halogen-exchanged by the above method are, for example, 2,6-dichlorobenzonitrile to 2,6-
As in the example of synthesizing difluorobenzonitrile, this is usually limited to aromatic halides with a small number of halogen substituents, and it is often difficult to perform complete halogen exchange with polyhalides with larger numbers of halogen substituents. Even if it is possible, the yield is poor. Furthermore, when aromatic halides are halogen-exchanged by the above method, electron-withdrawing groups (e.g. -CN group, -
The ortho and para positions of NO ₂ groups, etc.) can often be exchanged with halogen, but the meta position cannot be exchanged with halogen.

In fact, in the conventional literature there is no method for synthesizing tetrafluoroisophthalonitrile from tetrachloroisophthalonitrile by halogen exchange. However, an example of halogen exchange of tetrachloroisophthalonitrile is given by Ishikawa et al., Industrial Chemistry Journal,
It is stated in Volume 73, page 447 (1970),
Even with halogen exchange using potassium fluoride as a fluorinating agent in DMF solvent, 5-chloro-
Only 2,4,6-trifluoroisophthalonitrile is produced, and completely substituted tetrafluoroisophthalonitrile is not stored.

When producing tetrafluoroisophthalonitrile, the inventors thought that it would be difficult to synthesize it using the general method described above, and even if it could be synthesized, it would have many drawbacks and would be impossible to implement industrially, so they conducted intensive studies on possible methods. As a result, using benzonitrile as a solvent and under naturally occurring pressure, tetrachloroisophthalonitrile was dissolved at 190 to 400
The present inventors have discovered that tetrafluoroisophthalonitrile can be easily produced in good yield by reacting with a fluorinating agent, particularly potassium fluoride, to exchange halogens in the temperature range of .degree. C., and have completed the present invention.

The invention will be explained in more detail below.

Since the solvent benzonitrile in the present invention is thermally stable, the temperature is 190 to 400, which is considered to be the temperature necessary for halogen exchange of tetrachloroisophthalonitrile to tetrafluoroisophthalonitrile.
It has the advantage that it can be used even in the temperature range of °C, and there is no side reaction between the solvent and the raw material or product, which occurs with other solvents. In addition, the use of this solvent has the advantage of being able to easily control the temperature and prevent the formation of a large amount of carbide, unlike a manufacturing method without a solvent, making it possible to obtain the desired product in high yield during industrial implementation. have an advantage.

The fluorinating agent used in the halogen exchange reaction is generally an alkali fluoride such as cesium fluoride, potassium fluoride, or sodium fluoride, or an alkaline earth metal fluoride salt such as barium fluoride or calcium fluoride. There are many. In some cases, transition metal fluorides such as antimony fluoride are also used. In the present invention, any commonly used fluorinating agent can be used. Among these, particularly preferred is potassium fluoride, which is easy to handle and commercially available.

The fluorinating agent is required in an amount at least equivalent to the chloro atom to be substituted by the fluorine atom in the raw material tetrachloroisophthalonitrile.
It is sufficient if it is present in an amount of 4 times or more based on the mole. In particular, a range of 4 to 8 moles of potassium fluoride to tetrachloroisophthalonitrile is suitable.

The reaction temperature of the present invention is preferably in the range of 190 to 400°C. A temperature range of 250 to 350°C is particularly preferred.

When the reaction is carried out at a low temperature, a compound in which chlorine is not completely substituted with fluorine is likely to be produced, and at a high temperature, a carbide is produced, and in both cases, the yield of tetrafluoroisophthalonitrile is reduced.

In the present invention, in order to react under naturally occurring pressure,
Approximately 2Kg/ ^cm2 to 12Kg/in the temperature range of 210℃ to 350℃
Although the pressure in ^cm2 gauge is shown, it may be further pressurized with an inert gas such as nitrogen.

The reaction time varies depending on the reaction temperature, but is approximately 2
A range of 48 hours is appropriate.

The starting material, tetrachloroisophthalonitrile, is preferably added to the reaction system in an amount of about 5 to 50 parts per 100 parts by weight of the solvent.

It is generally said that it is preferable to carry out the halogen exchange reaction under anhydrous conditions as much as possible in order to increase the reaction rate and avoid side reactions.

Commonly used DMSO, TMSO ₂ , DMF,
Aprotic polar solvents such as NMP and DMSO ₂ are highly hygroscopic and contain a considerable amount of water.
Therefore, prior to the reaction, it is necessary to add benzene, toluene, etc. to remove water by distillation as an azeotrope. In the present invention, benzonitrile does not have hygroscopic properties, so its operation is not required in principle. However, since potassium fluoride used as a fluorinating agent has high hygroscopicity, in some cases it is preferable to add benzene, toluene, etc. to remove water by distillation in advance as an azeotrope.

In the present invention, a phase transfer catalyst may be present in the reaction system. That is, the presence of a phase transfer catalyst has the advantage of increasing the reaction rate and shortening the reaction time.

As a phase transfer catalyst, crown compounds such as dibenzo-18-crown-6-ether, molecular weight
300 to 600 polyethylene glycol, etc. can be used.

The appropriate amount to be added is 0.01 mol to 0.25 mol based on tetrachloroisophthalonitrile.

Benzonitrile, the solvent of the present invention, can be easily separated from the product by distillation and can be reused as a solvent in the next reaction.

EXAMPLES The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited thereto.

Example 1 200 g of benzonitrile, 80.0 g (0.301 mol) of tetrachloroisophthalonitrile, and 83.9 g (1.445 mol) of ultrafine dried potassium fluoride were charged into a 500 c.c. stainless steel autoclave, and the air inside the reaction vessel was charged. After replacing with nitrogen gas, at 320℃
The mixture was heated and stirred for 18 hours. After the reaction was completed, the mixture was cooled to room temperature and suspended potassium chloride and unreacted potassium fluoride were removed by filtration. When the benzonitrile solution of the mother liquor was analyzed using a gas chromatograph using an internal standard method with a packing material of SE521m and a column bath temperature of 60°C, it was found that tetrafluoroisophthalonitrile was compared to the charged tetrachloroisophthalonitrile.
90.5 mol% was obtained. In this analysis chart, almost no peaks of other components such as the peak of the main substituted isophthalonitrile were observed.
The product peak was confirmed to be tetrafluoroisophthalonitrile by mass spectrometry spectrum (70ev; m/e=200, 131, 100, 31). By distilling off the solvent benzonitrile from the above mother liquor by vacuum distillation, 52.5 g of crystals of tetrafluoroisophthalonitrile (MP; 73-76
℃) was recovered. The elemental analysis value of this crystal is carbon
48.0%, fluorine 38.3%, nitrogen 13.7% (theoretical value carbon
48%, fluorine 38%, and nitrogen 14%).

● ^19F NMR
(Solvent: Acetone- _d6 , External standard: Trifluoroacetic acid) δ=27.5ppm (doublet, J=11Hz, 1F) δ=40.6ppm (doublet, J=21Hz, 2F) δ=83.6ppm
(triplet − doublet, J _AB = 21Hz, J _AX = 11Hz,
1F) ● Mass spectrum EI m/e=200 (M ^- ) ● Infrared absorption spectrum (KBr) 2270cm ^-1 (ν _C ≡ _N ) 1500, 1640cm ^-1
(ν _nax .F=benzene ring C=C)

Claims (1)

[Claims] 1 Tetrafluoroisophthalonitrile.