Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Reexamination Certificate
2001-02-22
2002-09-17
Shah, Mukund J. (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
C562S484000, C504S144000
Reexamination Certificate
active
06452046
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process for producing 2,3,5,6-tetrachloro-1,4-benzenedicarboxylic acid. More particularly, the present invention relates to a process for producing 2,3,5,6-tetrachloro-1,4-benzenedicarboxylic acid, wherein the formation of reaction by-products is less than in the conventional processes to thereby enable efficiently to produce 2,3,5,6-tetrachloro-1,4-benzenedicarboxylic acid.
BACKGROUND OF THE INVENTION
Dimethyl 2,3,5,6-tetrachloro-1, 4-benzenedicarboxylate is widely and in a large amount used as an agricultural or horticultural herbicide.
A common process for producing dimethyl 2,3,5, 6-tetrachloro-1,4-benzenedicarboxylate comprises chlorinating benzene-1,4-dicarbonyl chloride to thereby obtain 2,3,5,6-tetrachloro-1,4-benzenedicarbonyl chloride and converting the same to a dimethyl ester with the use of methanol. However, this process has a drawback in that by-products such as hexachlorobenzene are formed in a large amount.
Therefore, there is a demand for the development of a process for producing dimethyl 2,3,5,6-tetrachloro-1,4-benzenedicarboxylate in which the content of impurities such as the above hexachlorobenzene is greatly reduced.
As the process for producing dimethyl 2,3,5, 6-tetrachloro-1,4-benzenedicarboxylate without the formation of hexachlorobenzene, there can be thought out a process comprising first performing an addition of water to 2,3,5,6-tetrachloro-1,4-benzenedicarbonitrile industrially readily procurable to thereby effect synthesis of 2,3,5,6-tetrachloro-1,4-benzenedicarboxamide, subsequently preparing 2,3,5,6-tetrachloro-1,4-benzenedicarboxylic acid from the 2,3,5,6-tetrachloro-1,4-benzenedicarboxamide and thereafter esterifying the 2,3,5,6-tetrachloro-1, 4-benzenedicarboxylic acid.
Apart from the above, generally, the method of performing an addition of water to a nitrile in sulfuric acid to thereby obtain a carboxamide and the method of hydrolyzing the carboxamide in sulfuric acid to thereby obtain a carboxylic acid are well known.
However, the hydrolysis of 2,3,5,6-tetrachloro-1,4-benzenedicarboxamide was difficult. Nevertheless, the inventors found that 2,3,5,6-tetrachloro-1, 4-benzenedicarboxamide can be hydrolyzed by heating the same in concentrated sulfuric acid at 220° C. or higher temperatures. The hydrolysis of 2,3,5,6-tetrachloro-1,4-benzenedicarboxamide under such severe conditions was unfavorably accompanied by side reactions such as decarboxylation and sulfonation, thereby disenabling to obtain the desired compound, 2,3,5,6-tetrachloro-1, 4-benzenedicarboxylic acid, with a high yield.
Therefore, if a method of efficiently producing 2,3,5,6-tetrachloro-1,4-benzenedicarboxylic acid from 2,3,5,6-tetrachloro-1,4-benzenedicarboxamide is developed, its industrial value is extremely great.
An object of the present invention is to provide a process for producing 2,3,5,6-tetrachloro-1, 4-benzenedicarboxylic acid which is a precursor of dimethyl 2,3,5,6-tetrachloro-1,4-benzenedicarboxylate useful as an agricultural or horticultural herbicide. More particularly, an object of the present invention is to provide a process for producing 2,3,5, 6-tetrachloro-1,4-benzenedicarboxylic acid from 2,3,5, 6-tetrachloro-1,4-benzenedicarbonitrile or 2,3,5, 6-tetrachloro-1,4-benzenedicarboxamide as a feedstock, wherein the formation of reaction by-products is less than in the conventional processes to thereby enable the efficient production of 2,3,5,6-tetrachloro-l,4-benzenedicarboxylic acid.
SUMMARY OF THE INVENTION
In one aspect of the present invention, there is provided a process for producing 2,3,5,6-tetrachloro-1,4-benzenedicarboxylic acid, comprising heating 2,3,5,16-tetrachloro-1,4-benzenedicarboxamide at 110 to 190° C. in the presence of sulfuric acid or fuming sulfuric acid containing water in an amount smaller than a stoichiometric value of hydrolysis of 2,3,5,6-tetrachloro-1,4-benzenedicarboxamide.
In another aspect of the present invention, there is provided a process for producing 2,3,5, 6-tetrachloro-1,4-benzenedicarboxylic acid, comprising heating 2,3,5,6-tetrachloro-1,4-benzenedicarbonitrile at 110 to 190° C. in the presence of sulfuric acid or fuming sulfuric acid containing water in an amount smaller than a stoichiometric value required for forming 2,3,5,6-tetrachloro-1,4-benzenedicarboxylic acid from 2,3,5,6-tetrachloro-1,4-benzenedicarbonitrile.
The acidity function (—Ho) of the sulfuric acid or the sulfuric acid containing fuming sulfuric acid is preferably in the range of 10.27 to 14.44.
In the present invention, 2,3,5,6-tetrachloro-1, 4-benzenedicarboxylic acid can be obtained directly from industrially readily procurable 2,3,5,6-tetrachloro-1,4-benzenedicarbonitrile or from 2,3,5,6-tetrachloro-1,4-benzenedicarboxamide which can be easily produced therefrom, as a precursor, by heating the same at 110 to 190° C. in the presence of sulfuric acid or fuming sulfuric acid containing water in an amount smaller than a stoichiometric value of hydrolysis. In the present invention, the hydrolysis of 2,3,5,6-tetrachloro-1,4-benzenedicarboxamide is advanced under mild conditions, so that the probability of side reactions is low. Therefore, the present invention enables to produce 2,3,5,6-tetrachloro-1, 4-benzenedicarboxylic acid more easily with a higher yield than in the prior art.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The process for producing 2,3,5,6-tetrachloro-1, 4-benzenedicarboxylic acid from 2,3,5,6-tetrachloro-1, 4-benzenedicarboxamide and the process for producing 2,3,5,6-tetrachloro-1,4-benzenedicarboxylic acid from 2,3,5,6-tetrachloro-1,4-benzenedicarbonitrile according to the present invention will be described separately from each other in detail below.
Production of 2.3,5.6-Tetrachloro-1, 4-benzenedicarboxylic Acid from 2,3,5,6-Tetrachloro-1, 4-benzenedicarboxamide
<2,3,5,6-Tetrachloro-1,4-benzenedicarboxamide as a Feedstock>
2,3,5,6-Tetrachloro-1,4-benzenedicarboxamide may be produced from 2,3,5,6-tetrachloro-1, 4-benzenedicarbonitrile. 2,3,5,6-Tetrachloro-1, 4-benzenedicarbonitrile is being produced on an industrial scale as a feedstock for drugs, agricultural or horticultural herbicides (common name: Tefluthrin, trade name: Force) and industrial chemicals, so that it is available at a low price. The reaction from 2,3,5,6-tetrachloro-1,4-benzenedicarbonitrile to 2,3,5,6-tetrachloro-1,4-benzenedicarboxamide proceeds in acid conditions readily and in a quantitative manner.
<Hydrolysis of 2,3,5,6-Tetrachloro-1, 4-benzenedicarboxamide>
The hydrolysis of 2,3,5,6-tetrachloro-1, 4-benzenedicarboxamide to obtain 2,3,5,6-tetrachloro-1, 4-benzenedicarboxylic acid, effected in the present invention, is carried out in a system consisting of 2,3,5,6-tetrachloro-1,4-benzenedicarboxamide as a feedstock, concentrated sulfuric acid or fuming sulfuric acid and water. Factors influencing the reaction efficiency include the concentration of reactants, temperature, pressure, reaction time, etc. These can be appropriately set individually or in combination.
Concentrated Sulfuric Acid or Fuming Sulfuric Acid
The concentration of concentrated sulfuric acid in use exerts direct influence upon the reaction efficiency by virtue of temperature and time and the yield of desired product. In the hydrolysis of 2,3,5,6-tetrachloro-1,4-benzenedicarboxamide according to the present invention, concentrated sulfuric acid is considered as not only functioning as a catalyst but also supplying water required for the reaction. The first stage of hydrolysis of 2,3,5,6-tetrachloro-1, 4-benzenedicarboxamide is initiated by an addition of proton to the carboxamido group, and a water substitution reaction follows.
Therefore, in the above hydrolysis, a suitable concentration of concentrated sulfuric acid in use is selected taking into account the proton donating capability of concentrated sulfuric acid and the amount of water that is present prior to and during the reaction. In the present invention, use is made of concentrated sulfuric acid containing water in an amount smaller than a stoichiometri
Ishii Teruhiko
Komatsubara Kenichi
Matsushita Utaro
Sano Kimitoshi
SDS Biotech K.K.
Shah Mukund J.
Tucker Zachary C.
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