SU878764A1 - Method of preparing aniline or o- or r-nitroanilines - Google Patents

Description

(54) METHOD OF OBTAINING ANILINES TYPE ABOUT OR P-NITROANGEOUNDS

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The invention relates to basic organic synthesis, in particular to a method for producing aromatic amines of the benzene series, which are important intermediates for the production of a number of dyes, fibers, chemicals for rubber, plastics; pharmaceuticals.

A known method for producing aromatic amines is by reducing the aromatic nitro compounds with calcium sulfohydrate 1}.

There is also known a method for producing aromatic amines of the benzene series by reducing, for example, with hydrogen, the corresponding nitro or chloro-nitro compounds of benzene, for which the feedstock is benzene. The yield of, for example, aniline from nitrobenzene is 97-98% 2.

Recently, there has been increasing evidence in the literature of the expediency of the industrial production of amines by the action of hypochlorite.

sodium on the corresponding amides in an alkaline medium (Hoffmann rearrangement) ..

The starting product for the benzene group amines in this process is the corresponding benzamides, which are obtained from toluene. Toluene is a cheaper and more promising raw material than benzene. This method is particularly promising for the production of p-nitroaniline.

A known method for producing benzene amine amines, which is the closest to the proposed method and consists in the interaction of the corresponding benzamides with sodium hypochlorite in the presence of a catalyst — bromine-iodine compounds or compounds of the general formula

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I X-N-R

The process is carried out in an aqueous medium in the presence of an excess of alkali at 80-90 ° C. All the necessary equimolar amount of the hyperchlorite is added at one time, while the temperature of the reaction mass rises by several degrees. When receiving by this method aniline from benzamide in the presence of a catalyst - sulfamide, the yield does not exceed 86.7%. p-Nitroaniline is obtained from P-nitrobenzamide in the presence of a catalyst, potassium iodide, with a yield of 84%. The melting point of the technical product of the chemically pure product is 147.5 ° C. However, this method does not allow to obtain the target product with a high yield and good quality. The aim of the invention is to yield and improve the quality of the target product. The goal is achieved by the fact that sodium hypochlorite is introduced into the reaction mixture gradually over 15150 minutes at and the temperature of the reaction mass during its addition is kept constant in the specified interval. According to the proposed method, the process is carried out as follows. The initial benzamide is mixed with water, an alkali solution, and then an equimolar amount of sodium hypochlorite is added at 5-22 ° C over 15-150 minutes. It is only after adding the total amount of hypochlorite in these temperature conditions that the temperature is raised to 8090 ° C, stirred, the reaction mixture is cooled to room temperature and the formed amine is separated by filtration or, for example, in the case of aniline being obtained by distillation with water vapor. In the case of 0-nitroanlene, the rate of hypochlorite injection, ensuring the maintenance of a constant temperature, is rarely controlled metrically. According to the proposed method, aniline is obtained (without using a catalyst with a yield of 96-97%, chromaticity of 15-30 units on a platinum-cobalt scale, P-nitroaniline with a yield of 91%, and mp. 146-147 C, (-nitroaniline by the Hoffman rearrangement in the literature has not yet been described) with a yield of 95.6% and a melting point of 68–69.5 ° C (the melting point of chemically pure O-nitroaniline is 71.5 ° C. 44 Example 1. 12.1 kg of benzamide mixed with 150 ml of water and 11 ml of 50% sodium hydroxide solution, then cooled to and at this temperature for 1 h, 44 ml of sodium hypochlorite solution are introduced and containing 7.5 g of active chlorine, then kept at 5 s for 30 minutes, the temperature is raised for 15 minutes and stirred for 10 minutes, the reaction product is distilled off with water vapor. The amount of distilled aniline is 8.97 g. 96.5% of theory. The color of the obtained aniline is on a platinum-cobalt scale of 15-30 units Example 2. 16.6 g of P-nitrobenzamide are mixed with 150 ml of water, 5.5 ml of 50% -Hdro sodium hydroxide solution and 0.1 g potassium iodide. At 22 ° C, 44 ml of sodium hypochlorite solution containing 7.5 g of active chlorine are added over 15 minutes. Then the temperature is raised for 10 minutes to 89-92 ° C and stirred for 10 minutes. Then cooled to room temperature, filter the product, washed with water until neutral. The weight of the technical product is 12.6 g, the yield of P-nitroaniline is 91.3% (calculated on the loaded P-nitrobenzamide}. The content of the basic substance is 99.3%, mp 146-147 ° C. Example 3. 8.3 g (-nitrobenzamide is mixed with 75 ml of water, 3.1 ml of a 46% sodium hydroxide solution and 0.1 g of potassium iodide. For 2 hours and 30 minutes, add 22 ml of sodium hypochlorite solution to a constant value of the redox potential; 3.77 g of active chlorine.After the addition of sodium hypochlorite is carried out, they are removed for 15 minutes, then the temperature is raised within 10 minutes to 83-85 ° C and maintained at this temperature for 10 minutes, then cooled to room temperature, the reaction product is filtered, washed with water until neutral.The technical product weight is 6.6 g, the content of the main substance is 98.5%. 95.6%, mp 68.5-69. Thus, the proposed method allows to increase the yield of the target products from 84-86 to 91-97%, to improve their quality; for example, the melting point of P-nitroaniline, this method, 146-147 ° C (prototype i44C).

Claims (2)

1. USSR author's certificate No. 72449, cl. C 07 C 87/60, 06.02.48. About 2. Berkman B.E. Industrial synthesis of aromatic nitro compounds and amines. M., 1964. 2. For Germany of FRG 2328757, cl. C 07 C 85/00, published 09.01.75 15 (prototype).