Organic compounds -- part of the class 532-570 series – Organic compounds – Nitriles
Reexamination Certificate
2001-08-29
2002-08-20
Siegel, Alan (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Nitriles
C570S147000, C570S177000, C570S180000
Reexamination Certificate
active
06437168
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method for the production of an aromatic fluorine compound, and more particularly to a method for extracting a reaction product containing a target aromatic fluorine compound formed by the halogen exchange reaction of an aromatic chlorine compound with a fluorinating agent efficiently from the reaction vessel.
2. Description of Related Art
The method for producing an aromatic fluorine compound by the halogen exchange reaction of an aromatic chlorine compound with a fluorinating agent is well known method. The official gazette of JP-B-62-7,185, for example, described a method for obtaining pentafluorobenzonitrile by subjecting pentachlorobenzonitrile and a fluorinating agent to the halogen exchange reaction in benzonitrile. A working example, recommending a reaction temperature in the range of 270-400° C. and a reaction time in the range of 2-48 hours, obtained a target product by charging an autoclave with benzonitrile, pentachlorobenzonitrile, and dry potassium fluoride and then heating and stirring the components at 320° C. for 16 hours therein. After completion of the reaction, the reaction solution was treated by the use of a rotary evaporator at an ambient temperature of 200° C. to separate potassium chloride and unaltered potassium fluorine from the solution and obtain on the bottom of the kettle a benzonitrile solution containing pentafluorobenzonitrile.
The official gazette of JP-B-01-49,346 discloses a method for obtaining tetrafluorophthalonitrile by subjecting tetrachlorophthalonitrile and a fluorinating agent to a halogen exchange reaction in benzonitrile. A working example, recommending a reaction temperature in the range of 190-320° C. and a reaction time in the range of 2-48 hours, obtained a target product by charging an autoclave with benzonitrile, tetrachlorophthalonitrile, and dry potassium fluoride and then heating and stirring these components at 255° C. for 16 hours therein. After completion of the reaction,the reaction solution was treated by the use of a rotary evaporator at an ambient temperature of 230° C. to separate potassium chloride and unaltered potassium fluoride from the solution and then the separated solution was distilled to obtain benzonitrile and tetrafluorophthalonitrile by evaporation.
Then, the official gazette of JP-B-02-16,746 discloses a method for effecting the halogen exchange reaction in a non-protone polar solvent or in the absence of a solvent. A working example, recommending a reaction temperature in the range of 200-450° C. and a reaction time in the range of 0.5-30 hours, obtained the target product by charging an autoclave with 2,6-dichlorobenzonitrile and potassium fluoride and heating these components at 350° C. for three hours for the purpose of inducing the components to react. After completion of the reaction, the reaction product was cooled and, from the neighborhood of 200° C. downward, treated by the use of a distilling device to obtain the target product.
The official gazette of JP-B-04-4,309, discloses a method for inducing 3,4,5,6-tetrachlorophthalonitrile to undergo a reaction in the presence of a benzonitrile solvent by heating the reaction mixture under a spontaneously generated pressure or under normal pressure while keeping the mixture in a refluxed state. A working example, recommending a reaction temperature in the range of 190-400° C. and a reaction time in the range of 4-48 hours with a view to preventing the solubility of potassium fluoride from abruptly rising in consequence of the use of benzonitrile at a temperature exceeding the boiling point thereof, obtained a target product by charging an autoclave with 3,4,5,6-tetrachlorophthalonitrile and dry potassium fluoride and heating the components at 230° C. for 10 hours for the purpose of inducing these components to react. After completion of the reaction, the reaction product was cooled to room temperature and the consequently suspended potassium chloride and the unaltered potassium fluoride were removed by filtration, with the result that the target product, i.e. 3,4,5,6-tetrafluorophthanlonitrile, was obtained in the filtrate. The methods disclosed in the official gazettes mentioned above invariably adopted a procedure of charging a reaction vessel with relevant raw material compounds, synthesizing a target product therein, extracting the product from the reaction vessel, and refining the target product in a separate vessel furnished with a filtering device or an evaporator.
The fluorinating agent which fulfills the role of inducing an aromatic chlorine compound and a fluorinating agent to undergo a halogen exchange reaction, however, is suffered to remain as a precipitate in the reaction solution occurring after completion of the halogen exchange reaction because it is the fluoride salt of an alkali metal such as cesium fluoride, potassium fluoride, or sodium fluoride or the fluoride salt of an alkaline earth metal such as barium fluoride or calcium fluoride. Since the reaction product formed by the halogen exchange reaction generally is a slurry of high viscosity, it is at a disadvantage in requiring an unduly long time for the work of extraction thereof from the reaction vessel and suffering part of the reaction product to remain as a residue in the reaction vessel. Since the raw material compounds and the target product generally emit a strong odor, it is practically difficult for the worker to collect the reaction product directly from the interior of the reaction vessel by reason of labor hygiene. Particularly, the process of the reaction mentioned above possibly by-produces hydrogen fluoride which is a corrosive compound. In the halogen exchange reaction which is carried out more often than not in a batchwise mode, therefore, it is an immensely important task to accomplish the extraction of the reaction product efficiently from the reaction vessel fresh from the completion of the target product without entailing leakage of the odor in the ambience and without exposing the worker to the atmosphere of the reaction product mentioned above.
In the fields of production, therefore, the desirability of developing a method for quickly extracting the reaction product from the reaction vessel, and that without suffering part thereof to remain as a residue inside the reaction vessel, has been finding enthusiastic recognition.
SUMMARY OF THE INVENTION
The object implied above is accomplished by the following invention.
(1) A method for the production of an aromatic fluorine compound by the halogen exchange reaction of an aromatic chlorine compound with a fluorinating agent, characterized by extracting the aromatic fluorine compound obtained by the halogen exchange reaction from a reaction vessel at a temperature in the range of 20-250° C.
This invention enables the reaction product fresh from the completion of the halogen exchange reaction to be efficiently extracted quickly from the reaction vessel without suffering part thereof to remain as a residue therein.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
This invention is directed, a method for the production of an aromatic fluorine compound by the halogen exchange reaction of an aromatic chlorine compound with a fluorinating agent, characterized by extracting the aromatic fluorine compound obtained by the halogen exchange reaction from a reaction vessel at a temperature in the range of 20-250° C.
The term “aromatic chlorine compound” as used in this invention refers to a compound containing at least one chlorine atom in an aromatic ring thereof. It means a compound which may be possessed of a substituent other than chlorine atom such as, for example, an electron attractive substituent such as cyano group, nitro group, or fluorocarbonyl group besides the chlorine atom. As concrete examples of the aromatic chlorine compound, the compounds represented by the following general formula (1) and (2) may be cited.
(wherein Cl denotes a chlorine atom, —X denotes any member selected from the element consisting of —CN, —NO
2
,
Fish & Richardson P.C.
Nippon Shokubai Co. , Ltd.
Siegel Alan
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