RU2521583C2 - Method of purification of raw sodium dicyanamide - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention can be used in chemistry of nitrogen-containing compounds and for synthesis of medications and colorants. A method of purification of raw sodium dicyanamide includes processing of a product, which contains sodium cyanate as a main admixture, with water solution of ammonium chloride in equimolar quantity.

EFFECT: invention makes it possible to obtain the target product - high quality purified sodium dicyanamide with 96,0% output.

2 tbl

Description

The invention relates to the field of chemistry of nitrogen-containing compounds, and in particular to the development of a method for the purification of crude sodium cyanamide, which is widely used in the synthesis of bigunidine series drugs, dyes, to combat moths and reduce paper fragility / 1,2,3 /.

A known method of purification of sodium dicyanamide by recrystallization from alcohol / 4 /. It is based on the different solubility in ethanol of the target product and sodium bromide. In addition, it is possible to purify sodium dicyanamide by fractional recrystallization from water. It should be noted that these methods have a number of disadvantages. These include:

- low quality of the target product (50%);

- lack of data on the yield, composition of the finished product and process indicators.

The authors selected a recrystallization solvent and the conditions of the process, which allows to intensify the purification. In the experiment, the following solvents were used: ethanol, N, N-dimethylformamide (DMF) and water.

The search was carried out using simple and combined methods. Simple methods consisted of recrystallizing the product in one of the solvents. Combined - in the sequential recrystallization of sodium dicyanamide from water and one of the solvents. The recrystallization conditions were selected by varying the dissolution and crystallization temperatures, as well as the amount of solvent.

The experiment was carried out in a round bottom flask equipped with a thermometer and a reflux condenser. A sample of the product at a given temperature was dissolved in one of the studied solvents, then the system was cooled. The precipitate was filtered off on a Buchner funnel using a vacuum created by a water-jet pump, washed with acetone cooled to 0 ° C and dried in a cuvette. The filtrate was evaporated to dryness, the resulting precipitate was dried. The results are presented in table 1.

In the first five experiments, ethyl alcohol was used as a solvent. The precipitate was dissolved both at room temperature and at the boiling point of alcohol, i.e. experiments 1-4 are duplicated. In experiment 5, recrystallization of the product was carried out. The composition control of raw dicyanamide and the purified product was carried out on the basis of elemental analysis (experiments 1-4). As a result of the analysis of the data obtained, it was found:

- recrystallization from ethyl alcohol allows you to clean the product only from sodium cyanate (experiment 5);

- the solubility of sodium dicyanamide in ethyl alcohol at 23-24 ° C is 2.26%, resulting in large losses of the target product.

In the following 7 experiments, the purification of sodium dicyanamide by recrystallization from N, N-dimethylformamide (DMF) was studied. The composition of the sediments was monitored by elemental and titrometric analyzes. In the course of the study, crude and recrystallized products from water were used. Dissolution of the product was carried out at the boiling point of the solvent. It was found that during crystallization from DMF, the product is almost completely freed from sodium chloride, but cannot be completely purified from sodium cyanate. However, even with a fairly good quality of purification, especially when using the combined method (experiments 10-12), DMF due to the high solubility in it of the target product (14%) cannot be used as a recrystallization solvent. In addition, it is quite expensive and scarce, and its losses for the operation are about 15%.

Recrystallization of sodium dicyanamide from water (experiment 13) allows you to clean the product from the main amount of sodium chloride, at the same time, sodium cyanate is only concentrated. Thus, all the physical methods discussed above have disadvantages.

The objective of the invention is to develop a new method for purification of sodium dicyanamide raw, which allows to increase the yield and quality of the target product. The problem is solved by using the chemical method of purification of sodium dicyanamide from sodium cyanate, the essence of which can be expressed by the following equation:

$$NaOCN+N{H}_{\mathrm{four}}Cl\to NaCl+{(NH)}_{2}CO\text{(one)}$$

The experiment was carried out at an equimolar ratio of reagents (NaOCN and NH ₄ Cl). The crude sodium dicyanamide and ammonium chloride were dissolved in water. The amount of water was determined from the calculation of the formation of a 25% aqueous solution of sodium chloride during the reaction. The study was carried out in a laboratory setup consisting of a 0.5 L round-bottom flask equipped with a stirrer, thermometer and dropping funnel. An aqueous suspension of the crude product was charged into the flask, and an aqueous solution of ammonium chloride was added over 30-40 minutes with stirring from a dropping funnel at a temperature of 50-70 ° C. Then, the resulting reaction mass was cooled to 0 ° C, the precipitate formed was filtered off, washed with acetone cooled to 0 ° C, and dried. The experimental results are presented in table 2.

table 2 Material balance of sodium dicyanamide purification Coming Consumption Stream composition g % Stream composition g % 1. DCAN, including: 30,0 40.7 1. DCAN purified, including: 14.8 20,0 1.1 DCAN 14.8 49.2 1.1 DCAN 14.2 96.0 1.2 Sodium cyanate 4.6 15.3 1.2 Sodium Chloride 0.6 4.0 1.3 Sodium Chloride 10.6 35.5 2. The mother liquor, including: 59.0 80.0 2. Ammonium chloride, aqueous solution, including: 23.8 32,2 2.1 DCAN 0.6 1,0 2.1 Ammonium Chloride 3.8 16,0 2.2 Sodium Chloride 14.1 23.9 2.2 Water 20,0 84.0 2.3 Water 40,0 67.8 3. Water 20,0 27.1 2.4 Urea 4.3 7.3 TOTAL: 73.8 100.0 TOTAL: 73.8 100.0

Analysis of the results presented in table 2, clearly shows that the proposed method is quite good, simple and reliable. The resulting sodium dicyanamide is of high quality. The crude product is practically freed from sodium cyanate. Analysis of the acetone filtrate shows that it contains 20% dissolved salts of the composition: NaN (CN ₂ ) - 4%, NaCl - 85.15%, NH ₄ Cl - 0.07%.

Thus, a new method for purifying contaminated sodium dicyanamide based on the interaction of sodium cyanate with ammonium chloride in an aqueous medium, which allows to obtain the target product of high quality (96.0%), is proposed.

Literature

1. Use of dicyanamides in and with pfotosensitix systems. [Review]: US Pat. No. 3563740, MKI G03C 5/54, 0G ZC / Haist G.M., King J.R., Rassage G.H .; // Applicant and patentee Eastman Kodak Co. - No. JP 11070A, declared - 02.20.67, publ. 02.16.71 - 1971; RZHH, 1971, 23N737P.

2. Rose, F.Z. Bisdiguanides having antibacterial activity [Review] / F.Z. Rose, G. Swain // J Chem. Soc. - 1956. - Vol. 56. - P. 4422; RZH, 1957, 54305.

3. Burns I. Synthesis and purification of carbon-14 labelled 1, 1-hexamethylene-bis [5- (4-chlorophenyl) biguanide] (chlorhexidine), 'Hibitane' (pages 1239-1250) [Review] / I. Burns , I. Labbelled // Compannds and Radio-pharm. - 1982. - Vol. 19. - P. 1239; RZH, 1983, 5ZH172.

4. Madelung, W. Uber Dicyanamides [Review] / W. Madelung, E. Kern, // Libigs. Ann. Chem. - 1922. - Vol. 427, No. 1).

Claims (1)

The method of purification of raw sodium dicyanamide, characterized in that the process consists in treating the product with an aqueous solution of ammonium chloride at an equimolar ratio of ammonium chloride: sodium cyanate (main impurity).