CS200441B1 - Method of preparing aminophenylurea - Google Patents

Description

The invention relates to a process for the preparation of an aminophenyl urea of the formula I

wherein X and Y are each independently hydrogen, methyl or chlorine.

These substances, which are valuable nolotovary products in the manufacture of dyes, are produced predominantly by the action of »cyanates in a slightly acidic» environment on the corresponding monoacyilphenylenediamines, with the following reactions taking place:

^h 2N - Ar - NHg - ŽS23 ___> HgK - Ar - NH - Ae --- S232—9 »

H.N-CO-NH-Ar-NHAe-5 ------ H-N-CO-HH-Ar-NHpH <1

One of the aminoecycles of phenylenediamine must be protected by acylation prior to reaction with cyanoic acid in a mildly acidic environment in order to avoid the undesirable formation of phenylenediurea

200 441

200 441

Η K-CO-NH-Ar-NH-CO-NH _O.

²

This hitherto used method of preparation has some disadvantages, which consist mainly in the three-step synthesis with the use of acetic anhydride or another acylating agent, where both the first stage, ie acylation and especially the third stage, ie acid hydrolysis of the acyl group, do not usually occur unequivocally; products that reduce the yield and quality of the product.

The lower yields of the synthesis are also related to the greater pollution of the waste water, in particular with the starting phenylenedlamine.

These disadvantages are largely eliminated by the process for preparing the aminophenyl urea of formula (I)

wherein X and Y are each independently hydrogen, methyl or chlorine according to the invention and which comprises the formation of the corresponding phenyl / endiamine of formula II, xh ₂ n = W \ ^NH 2 CD r

wherein X and Y have the same meaning as in formula I, at 10 to 50 ° C, react with cyanic acid released directly in the reaction mixture of successively added sodium or potassium cyanate in an aqueous medium whose acidity is maintained during the reaction; provide complete protonation of one and a partial protonation of the other amino group of the phenylenediamine of formula II and complete protonation of the resulting aminophenyl urea of formula I, for example by adding an acid, especially hydrochloric acid, and / or adding buffers or potassium corresponds to the reaction rate of the liberated acids _in cyanate with the phenylenediamine of formula II.

The acidity of the reaction mixture, wherein the protonate of one and a partial protonate of the other amino group of the phenylenediamine of Formula II, and the protonate of the aminophenyl urea of the formula I, is generally in the pH range of 0.5 to 4, as specifically exemplified below. For example, in the preparation of m-aminophenyl urea ee, m-phenylenediamine is treated with cyanic acid in an environment maintained at a pH of about 0.8-2.2% after the reaction. Ee dissolves the m-aminophenyl urea present in the reaction mixture, if not diluted with water; by heating and / or adding an alkaline agent such as aqueous

200 441 sodium or potassium hydroxide or carbonate solution, the reaction mixture is subjected to filtration with possible addition of activated carbon, the filtrate is acidified with hydrochloric acid to a pH of at least 1, the precipitated m-aminophenylurea crystals in the form of hydrochloride are cooled and separated from the liquid phase and optionally washed with dilute acid % hydrochloric acid to remove unreacted m-phenylenediamine.

Finding suitable conditions for the direct reaction of the phenylenediamine of formula II with just one cyanic acid molecule is contemplated. With the essential phase of the reaction, the interaction of the carbonate ion of cyanic acid H - 0 - 0 S 'N | <H - TT -? With a free electron pair of the amino group;

H

AND

AND"

AND

H

- Ar - NH, so that for the unambiguous reaction of just one mole of cyanic acid with one mole of phenylenediamine, it is necessary to flush out that one amino group of the phenylenediamine is protonated completely, or? then it does not contain a free electron pair capable of reacting with cyanic acid, and a second amino group of phenylenediamine to be protonated only partially to be able to react with cyanic acid. A further condition is that the resulting aainophenylureas * should therefore be upgraded so that the aminophenylurea can no longer be reacted with cyanic acid.

Further, the cyanic acid present must be capable of reacting. Since cyanic acid is poorly stable - decomposes to carbon dioxide and ammonium ions, or polymerizes to cyamelide - it is advisable to add sodium or potassium cyanate to the acidic reaction medium at a rate such that the cyanated acid just reacts with the phenylenediamine II.

Suitable protonation conditions, ie acidity of the reaction medium, can be determined from the course of the titration curves of the corresponding diamine of formula II with a strong mineral acid.

For example, the titration of an aqueous solution of 1,3-phenylenediamine having an initial pH of about 8.5 with hydrochloric acid shows that protonation of one amino group begins at about pH 7J at pH 5.2 is about half protonated, at about pH 3.5 it is protonated one amino group and the protonation of the other amino group begins. That is about half protonated at pH fully protonated is below pH 0.8.

The course of the titration curve of p-aminophenylurea then indicates that its complete protonation occurs below pH 2.2. Thus, a suitable pH for the preparation of m-aminophenylurea in the form of hydrochloride is in the range of 0.8 to 2.2. This pH range can be ensured either by the use of pH control, preferably automatic, in which an amount of mineral acid, preferably hydrochloric acid, is automatically added to the reaction mixture along with the alkali cyanate to maintain the desired pH, or by buffers controlling the desired pH range of protolytic equilibrium. .

200,441 such as urea or excess phenylenediamine and the like, or by simultaneous use of buffers and addition of acid.

A small amount of phenylenedeaurea, which may be formed locally by not realizing the reaction mixture, can be removed from the reaction mixture by filtration as a sparingly soluble component.

As can be seen, the process for the preparation of the aminophenyl urea of formula (I) according to the invention is advantageous in comparison with the hitherto used three-step synthesis (); it consists of only one operation without protecting one amino group of the used phenylenediamine it is not necessary to carry out acid hydrolysis after the reaction itself. This has a significant impact on the economy of the production process, reducing the time required for technology, saving the aoylating agent, avoiding loss of side reactions, especially in the case of acid hydrolysis, and reducing the amount and pollution of wastewater. Simplification also brings savings in energy, manpower and reduced equipment requirements.

In order to further elucidate the invention, the following examples are given in which the percentages are by weight.

Example 1

A solution of 1.0 mole of m-phenylenediamine and 1.0 mole of urea in 145 ml of water, acidified with hydrochloric acid to pH 1 ', 2, is condensed with cyanic acid by successively dropping 1.3 moles of potassium cyanate as a 40% solution and hydrochloric acid such that the pH of the reaction mixture during the condensation is in the range of 1.2 to 1.5 and the temperature in the range of 19 to 21 ° C. The reaction mixture is allowed to react for 30 minutes, heated to 60 ° C while adjusting pH to 3.5 to 4.5 by addition of sodium hydroxide. The insolubles were removed from the solution by filtration, the filtrate was acidified by the addition of 50 ml of concentrated hydrochloric acid, cooled to 10 ° C, the precipitated m-aminophenylurea hydrochloride crystals were filtered off and washed with 50 ml of dilute hydrochloric acid.

The yield was 220 g of wet crystals containing 130.2 g of m-aminophenyl urea, corresponding to 86.2% of theory, calculated on the m-phenylenediamine used.

Example 2

A solution of 1.0 mol of m-phenylenediamine in 145 ml of water, acidified to pH 0.8 with hydrochloric acid, is condensed by dropwise addition of 1.5 mol of potassium cyanate as a 40% aqueous solution and hydrochloric acid such that the pH of the reaction mixture is 0, 8 and a temperature of 10 ° C. The reaction mixture was allowed to react and continued as in Example 1.

The yield is 208 g of wet crystals of m-aminophenylurea hydrochloride containing 101.6 g of 100% m-aminophenylurea, corresponding to 74% of theory, calculated on the m-phenylenedlamine employed.

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Example 3

A solution of 1 mol of m-phenylenediamine in 145 ral of water, acidified with hydrochloric acid to pH 2.2, is condensed with cyanic acid by simultaneous dropwise addition of 1.2 mol of potassium cyanate as a 40% solution and hydrochloric acid so as to condense The pH of the reaction mixture was in the range of 2.0 to 2.2 and the temperature in the range of 45 to 50 ° C.

Yield: 346 g of paste containing 116.9 g of 100% aminophenyl urea, i.e., 77.4% of theory, calculated on the m-phenylenediamine employed.

Example 4

A solution of 1.0 mol of m-phenylenediamine in 400 ml of 18% hydrochloric acid is condensed with cyanic acid by successively introducing 0.5 mol of potassium cyanate crystalline pH while maintaining spontaneously between 0.8 and 1.5 and at ae temperature condensation at 18-20 ° C. After the reaction, the precipitated crystals are filtered off, the filtrate containing m-phenylenediamine being used for further synthesis of m-aminophenyl urea. The crystals were washed with dilute hydrochloric acid.

The yield was 177 g of wet crystals with a content of 65.5 g of m-aminophenylurea of 100% (43.2% of theory) calculated on the m-phenylenediamine used. The yield can be increased by repositioning the filtrate for further oneration.

Example 5

A solution of 1.0 mol of p-phenylenediamine in 350 ml of water acidified with hydrochloric acid to pH 3 and condensed with cyanic acid by the concurrent addition of 1.3 moles of potassium cyanate in a solution of 40 .mu.l hydrochloric acid so that The reaction mixture was in the range of 2.5 to 3 and the temperature in the range of 20 to 22 ° C. The procedure is as in Example 4.

The yield was 428 g of wet crystals containing 97.3 g of p-aminophenylurea 100% ee, ie 64.2% of theory, calculated on the p-phenylenediamine used.

Example 6

A solution of 1.0 mole of 2-methyl-5-fenylendiarainu in 150 ml of water, acidified with hydrochloric acid to pH 1.7, is condensed with cyanic acid by dropwise addition of 1.3 M potassium aaatanu to _the solution at a concentration of 40% and hydrochloric acid such that the pH of the reaction mixture during the condensation would be 1.5 to 1.7 and the temperature in the range of 20 to 22 ° C. The procedure is as in Example 4.

The yield is 214 g of wet crystals containing a mixture of 61 g of 4-methyl-3-aminopheaylurea, i.e. 37% of theory, calculated on the 2-methyl-1,5-phenylenediamine seeded, and 61.5 g of 2-methyl-5-aminophenylurea , ie 37.5% of the theory per fsnylsindiamine deployed.

Example 7

A solution of 1.0 mol of 5-chloro-2-methyl-1,4-phenylenediamine in 1500 ml of water, acidified with hydrochloric acid to pH 1.3, is condensed with cyanic acid by simultaneous dropwise addition of 1.3 moles of potassium cyanate in water. in the form of a 40% solution and hydrochloric acid such that the pH of the reaction mixture is between 1.3 and 1.5 and the temperature is between 20 and 22 ° C. After reaction, the pH of the reaction mixture is adjusted to 7 and after cooling, the precipitated crystals are filtered off and washed with dilute hydrochloric acid.

The yield was 393 g of wet crystals with a content of 128 g of a mixture of 2-methyl-5-chloro-4-aminophenyl urea and 2-chloro-5-methyl-4-arnophenyl ureas, i.e. 64.4% of theory per seeded 5-chloro-2- methyl-1,4-phenylenediamine. Chromatographers are equimolar and both compounds contaminated with traces of the starting diamine.

Example 8

A solution of 1.0 mol of 2,5-dlchloro-1,4-phenylenediamine in 1000 ml of water, acidified with hydrochloric acid to pH 0.9 ee, is condensed with cyanic acid by simultaneous dropwise addition of 1.3 mol of potassium cyanate in 40 ml of solution and hydrochloric acid such that the pH of the reaction mixture is between 0.8 and 1.0 and the temperature is between 20 and 22 ° C. After reaction, the pH of the reaction mixture was adjusted to 7 and after cooling, the precipitated crystals were filtered off and washed with dilute hydrochloric acid.

The yield was 305 g of wet crystals and contained 112.5 g of 2,5-dichloro-4-aminophenylarea, i.e. 51.2 theory, calculated on the 2,5-chloro-1,4-phenylenediamine employed. Chromatography contains the product diamine starting material and 2,5-dlchloro-1,4-phenylene urea.

Claims (2)

SUBJECT OF THE INVENTION A process for the preparation of an amnophenyl urea of the formula I wherein X and Y are each independently hydrogen, methyl or chlorine, characterized in that the corresponding phenylenedlamine of the general formula II ^H 2 N | Y Y nh ₂ • / X 200 441 where X and Y have the same meaning as in formula I, at 10 to 50 ° C, react with cyanate acid released directly in the reaction mixture from successively added sodium or potassium cyanate in an aqueous medium whose acidity is maintained at a value during reaction complete protonation of one and a partial protonation of the other amino group of the phenylenediamine of formula II; and complete protonation of the resulting aminophenylurea of formula I, for example by dropwise addition of an acid, in particular hydrochloric acid, and / or addition of buffers. As urea or phenylenedlamine, the rate of addition of sodium or potassium cyanate corresponding to the reaction rate of the liberated cyanate with the phenylenediamine of formula II, 2. A process for the preparation of m-aminophenylurea according to claim 1, characterized in that m-phenylenediaoft is treated with cyanic acid in an environment maintained at a pH of 0.8 to 2.2, after which the reaction mixture is present in the reaction mixture. -amino-phenyl urea dissolves, after dilution with water, by heating and / or addition of an alkaline reagent such as aqueous sodium or potassium hydroxide or carbonate solution, the reaction mixture is filtered with optional charcoal, acidified with at least 1 hydrochloric acid, cooled crystals precipitated The m-aminophenylurea in the form of the hydrochloride is separated from the liquid phase and optionally washed with dilute hydrochloric acid at a concentration of 3 to 15% by weight to remove any non-sintered m-phenylenediamine present.