CS265800B1 - Process for preparing 4,5-dichlor-1-phenyl-6-oxo-1h-pyridazine - Google Patents

Abstract

The solution relates to the method of production 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine by reaction of the reaction mixture obtained by diazotization aniline, redundancy of benzenediazonium chloride, subsequent hydrolysis of the phenylhydrazinedisulfonate with hydrochloric acid and diluting with water containing the same 3.6 to 8.0 wt. phenylhydrazine hydrochloride, at a temperature of 50 to 95 ° C with 4 to 10% mucoohloric acid solution in water and / or mother liquor after isolation of the resulting 4,5-dichloro- of 1-phenyl-6-oxo-1H-pyridazine of temperature 40 to 80 ° C in a continuous flow flow reactor at a temperature of 70 ° C 100 ° C. The reaction mixture of phenylhydrazine hydrochloride before entering the flow The reactor is stirred at 50 ° C 95 ° C with bleaching clay used in quantity 0.01 to 1.0 wt. weighted phenylhydrazine hydrochloride reaction mixture and filtered. The solution can be used in production chloridazone herbicide.

Description

The present invention relates to a process for the preparation of 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine by reacting a phenylhydrazine hydrochloride reaction mixture obtained by diazotizing aniline, reducing sodium benzenediazonium disulfide, followed by hydrolyzing sodium phenylhydrazine disulfonate with hydrochloric acid and diluting with water.

4,5-Dichloro-1-phenyl-6-oxo-1H-pyridazine is an intermediate for the production of the selective herbidide chloridazone. Several methods of its preparation are known. The process for the preparation of 4,5-dichloro-1-phenyl-6-oxo-pyrid-pyridazine according to DE 1 086 283 is based on the reaction of phenylhydrazine with mucochloric acid in an organic solvent medium, while according to U.S. Pat. 205 592, said reaction is carried out in a mixture of an organic solvent and water. Other methods of preparing 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine are based on the reaction of mucochloric acid and phenylhydrazine in an aqueous medium. According to U.S. Pat. No. 2,628,181, the reaction of phenylhydrazine hydrochloride with mucochloric acid is carried out in water in the presence of sodium carbonate, whereby the resulting phenylhydrazone of mucochloric acid is isolated and converted to 4,5-dichloro-1-phenyl-6-oxo-boiling in glacial acetic acid. H-pyridazine. Other known processes for the preparation of 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine (GB 881 616, DE 1 545 595, CS 220 299) use a dilute mineral acid medium for the reaction of mucochloric acid with phenylhydrazine. The methods of preparing 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine are based on the isolated phenylhydrazine, respectively. phenyl hydrazine hydrochloride.

phenyl hydrazine hydrochloride.

The object of the invention protected by CS 195 128 is a batch process for the preparation of 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine by reacting the undivided resulting reaction mixture from the production of phenylhydrazine with mucochloric acid. The disadvantages of this method, consisting mainly of technological complexity and energy intensity, are solved by the process for the production of 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine according to CS 236 650, which is based on the fact that the resulting undivided reaction mixture from the preparation of phenylhydrazine with a content of 3.6 to 8.0 wt. phenylhydrazine hydrochloride at a temperature of 50 to 95 ° C is continuously metered into the flow reactor simultaneously with a 4 to 10% solution of mucochloric acid in the mother liquor after isolation by reaction of the resulting 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine, the reactor contents are maintained at a temperature of 70 to 100 ° C. A common significant disadvantage of the methods of CS 195 128 and CS 236 650 is that the quality of the 4,5-dihalo-1-phenyl-6-oxo-1H-pyridazine obtained is too dependent on consistent adherence to the process for producing phenylhydrazine hydrochloride, e.g. j. the quality of its resulting reaction mixture. Practical experience confirms that even slight deviations from the stated technological mode of production of phenylhydrazine hydrochloride, which is virtually impossible to exclude under industrial production conditions, lead to increased formation of concomitant pitch impurities in the form of the resulting reaction mixture of phenylhydrazine hydrochloride. The use of the thus obtained reaction mixture of phenylhydrazine hydrochloride for the preparation of 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine leads to a product with markedly deteriorated qualitative parameters in terms of its saler use for the production of the chlorideidazone herbicide. No less serious are the technological problems associated with the handling of the contaminated reaction mixture of phenylhydrazine hydrochloride, which consists in clogging the metering pumps with pitch sludge and their subsequent mechanical damage.

The above-mentioned deficiencies are eliminated virtually completely by the process for producing 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine by reaction of the reaction mixture obtained by diazotizing aniline, reducing benzene diazonium chloride, followed by hydrolysis of sodium phenylhydrazinedisulfonate with hydrochloric acid and dilution with water containing 3.6 to 8 %, 0 wt. phenylhydrazine hydrochloride, at a temperature of 50 to 96 ° C with a 4 to 10% solution of mucochloric acid in water and / or in the mother liquor after isolation of the resulting 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine, 40 to 80 ° C in a continuous flow reactor at 70 to 100 ° C according to the invention. SUMMARY OF THE INVENTION The present invention is characterized in that the reaction mixture of phenylhydrazine hydrochloride is stirred at 50 to 95 ° C with the bleaching clay used in an amount of 0.01 to 1.0% by weight before entering the flow reactor. calculated on the weight of the reaction mixture of phenylhydrazine hydrochloride and filtered.

A decisive advantage of the process according to the invention is that the simple and inexpensive intervention in the technological process guarantees the continuous high quality of the 4,5-dir-chloro-1-phenyl-6-oxo-1H-pyridazine produced, which is essential for herbicide production. chloridazon. The extensive testing of the process of the present invention under operating conditions has shown that treating the resulting reaction mixture from the production of phenylhydrazine hydrochloride with bleaching clay makes it easy to produce 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine of about 99% purity while its use only about 94%. Another important advantage of the method according to the invention is the trouble-free operation of the metering pumps, which results in a reduction of downtime and maintenance costs, respectively. investment costs.

The following examples illustrate but do not limit the invention.

Example 1

The boiler was dosed with 872 kg of water. While stirring and cooling, 1156.8 kg of 32% hydrochloric acid were added. After cooling the contents of the boiler to 10 ° C, 404.6 kg of aniline was added at a temperature of 10 to 150 ° C. After addition of the aniline, the mixture was cooled to +2 ° C and 741.8 kg of a 40% aqueous sodium nitrite solution were metered below the surface. At the end of diazotization, the reaction mixture was discharged into a reduction vessel in which 2530.2 40% sodium bisulfite and 609.7 kg of 40% sodium hydroxide were introduced at a rate such that the temperature of the mixture was maintained between 30-35. C. After heating to 85 ° C, 5.5 kg of zinc dust and 1.7 kg of bleaching clay were added. The mixture was held at 90 ° C for 2 h. After filtering, the reaction mixture was charged to boilers containing 1090.6 kg of 32% hydrochloric acid. Hydrolysis was performed for 4 h at 90 ° C. The phenylhydrazine hydrochloride suspension was diluted with 3000 kg of water at 70 ° C, 10 kg of bleaching clay was added and the mixture was filtered while stirring. A 4.3% phenylhydrazine hydrochloride solution was obtained.

A flow reactor consisting of three boilers connected together in a cascade and equipped with a stirrer was charged with 1 610 kg of 4.3% phenylhydrazine hydrochloride at 70 ° C prepared as described above and 1330 kg of a 6% aqueous mucochloric acid solution with hourly stirring. containing 0.03 kg of free hydrogen chloride at 60 ° C. The reaction mixture was held in the reactor at 95 ° C and held for 1 h. The technical product 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine was isolated by filtration. 11.35 kg of product with a purity of 99% were obtained in 1 hour. The yield was 97.4% of theory.

Example 2

The procedure described in Example 1, except that 20 kg of bleaching clay was added after diluting the reaction mixture of phenylhydrazine hydrochloride at 90 ° C, gave the technical product 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine of purity 99.4%.

Claims (1)

A process for the preparation of 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine by reaction of the reaction mixture obtained by aniline diazotation, reduction of benzenediazonium chloride, followed by hydrolysis of sodium phenylhydrazinedisulfonate with hydrochloric acid and dilution with water containing 3.6 to 8.0 wt. phenylhydrazine hydrochloride, at a temperature of 50 to 95 ° C with a 4 to 10% solution of mucochloric acid in water and / or a mother liquor after isolation by reaction of the resulting 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine at 40 to 80 ° C in a continuous flow reactor at 70 to 100 ° C, characterized in that the phenylhydrazine hydrochloride reaction mixture is stirred at 50 to 95 ° C with the bleaching clay used in an amount of 0.01 to 1 prior to entering the flow reactor. %, 0 wt. calculated on the weight of the reaction mixture of phenylhydrazine hydrochloride and filtered.