RU2381215C1 - 2-imino-4-thiobiuret synthesis method - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a method for synthesis of 2-imino-4-thiobiuret by reacting dicyandiamide with a sulphur-containing compound in an acidic medium, where dicyandiamide is reacted with sodium thiosulphate in a 20-25% sulphuric acid medium at 90-98°C for 40-60 minutes. The reaction mass is kept at that temperature for 4-4.5 hours. The 2-imino-4-thioburet bisulphate formed is dissolved in water, after which 10-15% ammonia water is added first for 2-3 minutes, and then a 25-30% sodium hydroxide solution for 3-4 minutes and the end product is extracted using a known method.

EFFECT: increased output of end product, cutting synthesis time to 7-8 hours and increased environmental safety of the method.

1 cl, 5 ex, 1 tbl

Description

The invention relates to the chemical industry, namely to the production of 2-imino-4-thiobiuret. This product is used as a precursor in the synthesis of five-membered heteroaromatic diamines, drugs, and it itself has radioprotective properties.

State of the art

A known method of obtaining 2-imino-4-thiobiuret by the interaction of thiourea with phosphorus pentachloride (Rathke B. Ver. 1879. V.11. S.962-967).

However, the use of phosphorus (V) chloride leads to environmental hazards.

Closest to the invention in terms of essential features is a method (Kurzer F. J. Chem. Soc. 1955. P.2-5.), Which includes the following stages:

- the interaction of dicyandiamide with a sulfur-containing compound, namely gaseous hydrogen sulfide, in an acidic environment at 65-70 ° C for 24-30 hours;

- subsequent cooling of the reaction mass to 45 ° C;

- the addition of sodium hydroxide to neutralize the acidic environment and the binding of impurities of elemental sulfur;

- filtration to remove the formed sodium sulfide;

- cooling the filtrate to 0 ° C for 24 hours;

- filtering the target product;

- purification of the target product by recrystallization from boiling methanol.

This method has several significant disadvantages:

- low yield of the target product - 34-42%;

- long duration of the method - 61-64 hours;

- high environmental hazard of the method due to the use of gaseous hydrogen sulfide.

SUMMARY OF THE INVENTION

The objective of the invention was to find a method for producing 2-imino-4-thiobiuret by reacting dicyandiamide with a sulfur-containing compound in an acidic environment, which would increase the yield of the target product, shorten the duration of the process and increase its environmental safety.

The problem is solved by the method of obtaining 2-imino-4-thiobiuret by the interaction of dicyandiamide with a sulfur-containing compound in an acidic medium, in which dicyandiamide is reacted with sodium thiosulfate in a medium of 20-25% sulfuric acid at 90-98 ° C for 40-60 minutes, maintain the reaction mass at this temperature for 4-4.5 hours, the resulting 2-imino-4-thiobiuret bisulfate is dissolved in water and 10-15% ammonia water is added first for 2-3 minutes, then 25- 30% sodium hydroxide solution for 3-4 minutes and secrete left product in a known manner.

The invention makes it possible to obtain the following advantages:

- increase the yield of the target product to 53-68%;

- reduce the total time of the method to 7-8 hours;

- increase environmental safety, since the use of gaseous hydrogen sulfide was ruled out.

Information confirming the possibility of carrying out the invention

To implement the method using the following substances:

Dicyandiamide TU 6-09-3967 - 75 hours

Narya thiosulfate GOST 429 - 76 hours

Sulfuric acid GOST 4204 - 77 hh.

Water ammonia GOST 3760 - 79 rpm.

Sodium hydroxide GOST 4328 - 77 hours

State standard specification 6995 methyl alcohol - 77 hch.

The method is carried out by sequentially carrying out the following operations:

- dissolve dicyandiamide and sodium thiosulfate in water when heated;

- 20-25% sulfuric acid is added dropwise within 40-60 minutes;

- heated to 90-98 ° C;

- make exposure at a temperature of 90-98 ° C for 4-4.5 hours;

- cooled to room temperature;

- the precipitated precipitate of 2-imino-4-thiobiuret bisulfate is filtered off, washed with water and dried;

- dissolve 2-imino-4-thiobiuret bisulfate in water when heated;

- add an equimolecular amount of 10-15% ammonia water and mix for 2-3 minutes;

- add an equimolecular amount of 25-30% sodium hydroxide solution and mix for 3-4 minutes;

- cool the reaction mass to 0 ° C;

- filter the precipitate of 2-imino-4-thiobiuret;

- clean 2-imino-4-thiobiuret.

Example 1

A mixture consisting of 8.4 g (0.1 mol) of dicyandiamide, 27.3 g (0.11 mol) of sodium thiosulfate and 50 ml of distilled water is heated with stirring until it is completely dissolved. 36.6 ml (0.11 mol) of 25% sulfuric acid are added over 1 hour. Heated to 98 ° C and maintained at this temperature for 4.5 hours. The filtrate is cooled. The resulting precipitate of 2-imino-4-thiobiuret bisulfate is filtered off, washed with cold water and dried.

10 g (46 mmol) of 2-imino-4-thiobiuret bisulfate is dissolved in 125 ml of distilled water with heating. When completely dissolved, add 10 ml (46 mmol) of 15% ammonia water and mix the reaction mass for 2 minutes. Then, 4.2 ml (46 mmol) of a 30% sodium hydroxide solution was added to the resulting solution and stirred for 4 minutes. The target product is isolated by cooling to 0 ° C and filtering the precipitate.

Yield 4.9 g (90%). After recrystallization from methanol, shiny prisms are obtained in an amount of 3.7 g (75%).

Mp = 162-164 ° C. Mp ^lit = 160-164 ° C. ESP (H ₂ O), λ _max (logε) nm: 212 (4.15); 236 (4.21); 263 (4.13).

The yield of the target product and the duration of the method for different values of the parameters are given in the table.

Claims (1)

A method of producing 2-imino-4-thiobiuret by reacting dicyandiamide with a sulfur-containing compound in an acidic medium, characterized in that dicyandiamide is reacted with sodium thiosulfate in a medium of 20-25% sulfuric acid at 90-98 ° C for 40-60 min, maintain the reaction mass at this temperature for 4-4.5 hours, the resulting 2-imino-4-thiobiuret bisulfate is dissolved in water, after which 10-15% ammonia water is added first over 2-3 minutes, then 25-30% sodium hydroxide solution for 3-4 minutes and the desired product is isolated by the way.