Process for producing 3-chloro-4-fluoronitrobenzene

Details Process for producing 3-chloro-4-fluoronitrobenzene Process for producing 3-chloro-4-fluoronitrobenzene

1988-06-23

1990-02-06

Locker, Howard J.

Organic compounds -- part of the class 532-570 series

Organic compounds

Oxygen containing

568937, 568939, C07C 7912, C07C 1712

Patent

active

048989967

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to a process for producing 3-chloro-4-fluoronitrobenzene. More specifically, the present invention relates to a process for producing 3-chloro-4-fluoronitrobenzene having a high purity with a high yield.


BACKGROUND ART

3-Chloro-4-fluoronitrobenzene is a useful compound as an intermediate for medicine and agricultural chemicals.
As industrial process for producing 3-chloro-4-fluoronitrobenzene, there has hitherto been known a process which comprises reacting 3,4-dichloronitrobenzene with excessive amount of potassium fluoride in a polar organic solvent at a high temperature. By this process, however, 3-chloro-4-fluoronitrobenzene cannot be obtained at a low cost due to the low yield and low purity, a large amount of expensive potassium fluoride used, requirement of a lot of cost for recovery of the polar organic solvent, etc.
The following reports disclose that 4-fluoronitrobenzene is subjected to chlorination to obtain 3-chloro-4-fluoronitrobenzene: to 101.
According to the processes described in the reports .circle.1 and .circle.2 , 4-fluoronitrobenzene is chlorinated in the presence of ferric chloride or iron powder. These processes, however, have a defect that a large amount of dichloro-4-fluoronitrobenzene are produced as by-products in addition of aimed 3-chloro-4-fluoronitrobenzene. And there is no description in which aimed compound was obtained in a high yield in the reports.
Thus, there is demanded a development of a process comprising chlorination of 4-fluoronitrobenzene, in which 3-chloro-4-fluoronitrobenzene is obtained with a high yield with lowering the production of dichloro-4-fluoronitrobenzene as by-products.


DISCLOSURE OF INVENTION

As the result of extensive researches for solving the problems as mentioned above, the present inventors have found that dichloro-4-fluoronitrobenzenes as the by-products are rarely formed by chlorinating 4-fluoronitrobenzene in the presence of specific substances and achieved the present invention thereon.
According to the present invention, there is provided a process for producing 3-chloro-4-fluoronitrobenzene which is characterized by chlorinating 4-fluoronitrobenzene in the presence of:
(1) iodine or an iodide in combination with iron or an iron compound, or
(2) iodine or an iodide in combination with antimony or an antimony compound.


BEST MODE FOR CARRYING OUT THE INVENTION

First, 4-fluoronitrobenzene used as a starting material in the process of the present invention is explained. 4-Fluoronitrobenzene is produced, for example, by directly nitrating fluorobenzene. Nitratoin of fluorobenzene is more advantageously carried out in sulfuric acid kept in a specific concentration at a temperature in a specific range.
The concentration (weight ratio) of sulfuric acid to be kept during the nitration reaction is selected in the range of 65 to 80%, preferably in the range of 70 to 78%.
The reaction temperature is 0.degree. to 90.degree. C., preferably 30.degree. to 80.degree. C., more preferably 40.degree. to 70.degree. C. As a nitrating agent, nitric acid is preferably used. The amount of nitric acid is preferably 1.0 to 1.1 times of the theoretical amount. As a method of addition of nitric acid, though nitric acid can be added alone, nitric acid is more preferably added in a state of mixed acids composed of nitric acid and sulfuric acid. The reaction time is usually 0.5 to 5 hours, though it varies depending on the reaction conditions. After completion of the reaction, the sulfuric acid layer is separated from oil layer and used by recycling. The oil layer is washed with warm water, then with an aqueous alkali solution followed by distillation to separate fluoromononitrobenzenes, respectively.
Thus obtained 4-fluoronitrobenzene is chlorinated in the presence of:
(1) iodine or an iodide in combination with iron or an iron compound, or
(2) iodine or an iodide in combination with antimony or an antimony compound.
The iodine and the iodides used in the process of the present invention include iodine, hydrogen io

REFERENCES:
patent: 4446075 (1984-05-01), Erglmeier et al.
patent: 4456777 (1984-06-01), Petruck et al.
Chemisches Zentralflatt 194 II p. 1432.
Receuil des Travaux Chimiques des Payo--Bas 51, (1932), pp. 98-113.
Japanese Abstract, vol. 8, No. 67, Mar. 29, 1984, Abstract No. C216, Abstract No. 58-222040, Inque, Fumio et al., "Preparation of M--Chlorobezotrifluoride".
Patent Abstracts of Japan, vol. 4, No. 54, Apr. 23, 1980, Abstract No. 55-24120, Kobayashi, "Preparation of 2,5--Dichlorobenzoic Acids".

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