RU2385860C1 - Method of purifying 1,2-phenylenediamine - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a novel improved method of purifying 1,2-phenylenediamine, involving distillation at normal pressure. During distillation, one of aliphatic alcohols - ethyl, propyl or isopropyl or their mixture in arbitrary ratio is put into the distillate receiving vessel and the obtained alcohol solution is cooled to 5-10°C and 1,2-phenylenediamine is filtered.

EFFECT: method enables production of high-purity 1,2-phenylenediamine and its storage for a long period of time without change in colour.

1 cl, 6 ex

Description

The invention relates to organic chemistry, namely to diamine derivatives of benzene and directly to 1,2-phenylenediamine, which is widely used in the synthesis of various drugs and in enzyme-linked immunosorbent assay (ELISA) in biochemistry.

A known method of purification of 1,2-phenylenediamine. It consists in the recrystallization of 1,2-phenylenediamine from water in the presence of sodium hydrosulfite, filtration and drying [1].

The disadvantage of this method is the darkening of the purified 1,2-phenylenediamine within two months after purification.

A known method of purification of 1,2-phenylenediamine, which also uses the system: hot water and sodium hydrosulfite dissolved in it [2]. A 1,2-phenylenediamine sample purified by this method also acquired a dark color within two months after purification.

A known method of purification of 1,2-phenylenediamine using water and sodium sulfite [3]. The 1,2-phenylenediamine obtained by this method, as well as the first two, darkens within 2-3 months of storage.

All three methods are very similar to the 1,2-phenylenediamine purification system, which uses almost the same methods with insignificant variations, so the quality of the product has small variations.

The disadvantages of these methods is that they do not provide a completely white substance, well stored in time and suitable for chemical synthesis and for ELISA. Over time, the product acquires a dark color and cannot be used in fine organic synthesis, especially in ELISA, for which the color of the reagent is of particular importance.

The prototype of the invention is a method for purification of 1,2-phenylenediamine [4], which consists in heating 1,2-phenylenediamine in the presence of zinc sulfate or chloride, followed by distillation under reduced pressure, resulting in a colorless product, which becomes light brown during storage for 3 months.

The disadvantages of the method remain the same, because it does not provide a quality product that would not change its color during prolonged storage.

The technical result of the invention is to obtain a pure product that does not contain impurities. It can be stored for a long time (more than three years) without changing color.

The expected result can be achieved on available chemical equipment through the use of the effect of rapid cooling of distilled 1,2-phenylenediamine. This physical effect is obtained by combining the processes of distillation and recrystallization of 1,2-phenylenediamine, which gives a high-quality product.

The essence of the invention lies in the fact that 1,2-phenylenediamine is distilled at normal pressure in a nitrogen atmosphere (the boiling point of 1,2-phenylenediamine is 254-256 ° C), and one of the aliphatic alcohols (ethyl, propyl, is preliminarily placed in the receiving vessel) or isopropyl) or a mixture thereof in an arbitrary ratio. The resulting alcoholic solution was cooled to 10 ° C and 1,2-phenylenediamine was filtered off. Moreover, the ratio of 1,2-phenylenediamine to alcohol is 1: (2 ÷ 3).

Method implementation examples

Example 1. 100 g of the source of 1,2-phenylenediamine (the content of the basic substance is 80%) is distilled from a Wurz flask at atmospheric pressure in a nitrogen atmosphere. In the receiving flask is 300 ml of ethyl alcohol. The distillation process is carried out until traces of dark liquid appear in the distillate. At this point, the distillation is stopped and the distillate (1,2-phenylenediamine) in the form of a solution in ethanol is cooled to 10 ° C. The precipitated white 1,2-phenylenediamine precipitate was filtered off on a Buchner funnel, washed with 25 ml of ethanol cooled to 10 ° C, and dried on filter paper. Yield of 1,2-phenylenediamine 70 g (87.5%). Mp 102-103 ° C, bp 254 ÷ 256 ° C, white crystalline precipitate.

The proposed method allows you to get rid of impurities due to the rapid cooling of 1,2-phenylenediamine. After distillation, the temperature of 1,2-phenylenediamine decreases from 254 ° C to 20-40 ° C, and the alcohol vapor layer protects 1,2-phenylenediamine from oxidation. This technique leads to a sharp cooling of the product by more than 200 ° C.

Example 2. The purification of 1,2-phenylenediamine is carried out analogously to example 1, only 200 ml of isopropyl alcohol are placed in the receiver. The yield of pure 1,2-phenylenediamine is 72 g (90%). White crystalline powder.

Example 3. Purification of 1,2-phenylenediamine is carried out analogously to example 1, only 250 ml of propyl alcohol are placed in the receiver. The yield of 1,2-phenylenediamine is 69 g (86.3%). White crystalline powder.

Example 4. The purification of 1,2-phenylenediamine is carried out analogously to example 1, only in the receiver is a mixture of two alcohols (ethyl and propyl) in any ratio. The yield of 1,2-phenylenediamine is 69 g (86.3%).

Example 5. The purification of 1,2-phenylenediamine is carried out analogously to example 1, only in the receiver is a mixture of three alcohols (ethyl and propyl or isopropyl) in any ratio. The yield of 1,2-phenylenediamine is 73 g (91.3%).

Example 6. Purification of 1,2-phenylenediamine is carried out analogously to example 1, only a solution of the distillate in alcohol is cooled to 5 ° C. The yield of 1,2-phenylenediamine is 70 g (87.5%). (Further cooling of the distillate solution in alcohols from 10 ° C to 5 ° C does not increase the yield of 1,2-phenylenediamine).

Positive effect

The proposed method allows you to get rid of impurities due to the rapid cooling of 1,2-phenylenediamine after distillation (from 254 ° C the temperature drops to 20-40 ° C), as well as the protective effect of alcohol vapor (1,2-phenylenediamine does not have time to oxidize). When storing the samples of 1,2-phenylenediamine obtained in Examples 1-6, they remained completely white for 3 years. Compared with samples of 1,2-phenylenediamine purified by recrystallization from water or distillation in vacuo, the samples obtained by the proposed method were more stable, because samples recrystallized from water or distilled in vacuo darkened already in the second or third month after purification.

LITERATURE

1. Fizer L., Fizer M. Reagents for organic synthesis, vol. 4, p. 38, 1971.

2. Syntheses of organic preparations, Sat 2, p. 509-511, 1949.

3. Agronomov A.E., Shabarov Yu.S. Laboratory work in an organic workshop. M., "Chemistry", pp. 195-196, 1974.

4. Yap. US Pat. No. 53-77024, declared 12/17/76, No. 51-150742, publ. 07/08/78. (RZhKhim, 1979, 12N148P). The method of purification of aromatic amines. Nagata Teruyuki, Hirai Hiroshi, Yamanoto Takaichi [Mitsui Toatsu Kagaku KK].

Claims (1)

The method of purification of 1,2-phenylenediamine, including distillation, characterized in that the distillation is carried out at normal pressure in a nitrogen atmosphere, while one of the aliphatic alcohols - ethyl, propyl or isopropyl alcohols, or a mixture of them in an arbitrary ratio is placed in the distillate receiver, then obtained the alcohol solution is cooled to 5-10 ° C and 1,2-phenylenediamine is filtered off, and the ratio of alcohol (alcohols) to 1,2-phenylenediamine is (2 ÷ 3): 1.