RU2547264C1 - Method of producing chlorine-substituted phenylenediamines - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method is carried out by reducing corresponding chlorine-substituted nitroanilines or dinitrobenzenes in a solvent medium. A solution of the reduction products is treated with mineral acid (hydrochloric, sulphuric or phosphoric acid or with hydrogen chloride gas) and the obtained salt of the mineral acid is converted into a base by treating with an alkaline agent in the presence of an antioxidant (sodium sulphite, potassium sulphite or sodium pyrosulphite). The desired compound is separated by extraction and crystallisation. The solvent used in the reduction process is water, dimethylacetamide or a mixture of dimethyl formamide with water, methyl alcohol, ethyl alcohol, isopropyl alcohol, ethyl acetate, benzene or toluene. The reduction process is carried out using hydrogen in the presence of a catalyst: platinum or palladium or another platinum group metal on a support, or palladium which is modified with nickel or iron on a support, or a skeleton nickel or nickel-chromium catalyst. Alternatively, reduction is carried out using iron in an aqueous solvent in the presence of an electrolyte.

EFFECT: improved method of producing chlorine-substituted phenylenediamines, which enables to obtain end products of high quality by preventing oxidation and formation of packing products during separation.

8 cl, 1 tbl, 13 ex

Description

Chlorinated phenylenediamines are of interest as monomers for heat-resistant flame-retardant high-strength fibers, films and varnishes.

A known method of producing 2-chloro-1,4-phenylenediamine (2,5-diaminochlorobenzene (CPPDA)) by the electrochemical reduction of 2-chloro-4-nitroaniline (XNA) (A.S. SU 1511257, IPC C07C 87/60, publ. 09/30/1989). The disadvantage of this method is the use of an expensive platinum anode, very high corrosiveness of the working environment [9.4-12% HCl or H ₂ SO ₄ , 0.4-0.8% TiCl ₄ , TiCl ₃ , Ti (SO ₄ ) ₂ , Ti ₂ (SO ₄ ) ₃ in water], the formation of impurities during the recovery process, as evidenced by the violet color of the electrolyte.

A known method for producing 2-chloro-1,4-phenylenediamine by catalytic hydrogenation of HNA with hydrogen under pressure up to 10 MPa on a stationary platinum catalyst in ethyl acetate (Patent RU 2083540, IPC C07B 31/00, publ. 07/10/1997). The conditions for the selection of the product, indicators of its quality and yield are not shown. The disadvantage of this method is the process under high pressure, necessitating the use of expensive equipment.

A known method for producing 2,5-dichloro-1,4-phenylenediamine by reducing 2,5-dichloro-4-nitroacetanilide with iron filings in a medium of water in the presence of formic acid and a dispersant, followed by hydrolysis of 2,5-dichloro-4-amino-1- acetanilide (A.S. Czechoslovakia CS195789, IPC C07C 87/60, publ. 05.15.1982). After completion of the recovery, the reaction mass is neutralized with magnesium oxide. The yield of 2,5-dichloro-4-aminoacetanilide in the reduction step is 68% of theory. Deacetylation is carried out by hydrolysis of 2,5-dichloro-4-aminoacetanilide in the presence of a twofold molar excess of sulfuric acid, followed by purification with activated carbon and kieselguhr. The free base is isolated by neutralization with soda ash, followed by washing with water and drying. The yield of 2,5-dichloro-1,4-phenylenediamine at the deacetylation step is 89.8%. Thus, the total yield of the target phenylenediamine at the stages of reduction and deacetylation is only 61% of the theoretical. Any characteristics of the obtained product are not given in the description. It is noted that it can be used as a raw material in the production of azo pigments for dyeing plastics and fibers. The process is cumbersome, low output. Obviously, the proposed method does not provide the receipt of 2,5-dichloro-1,4-phenylenediamine monomer degree of purity.

A known method of producing 2,5-dichloro-1,4-phenylenediamine by reducing 4-nitro-2,5-dichloroaniline with excess hydrazine hydrate in the presence of iron chloride and activated carbon in ethyl alcohol (Chinese Pat. 1974540, C07C 209/36, publ. 06/06/2007). The yield of 2,5-dichloro-1,4-phenylenediamine 93%, the content of the basic substance 99.5% (high performance liquid chromatography, HPLC), melting point 164-165 ° C. The disadvantage of this method is the use of expensive highly toxic hydrazine hydrate.

A known method for producing 4-chloro-1,3-phenylenediamine by catalytic hydrogenation of 2,4-dinitrochlorobenzene (DNCB) in a mixture of ester and alcohol under a hydrogen pressure of up to 7 MPa in the presence of a platinum catalyst on coal (GB Patent GB 1417662, IPC B07J 23 / 00, C07C 209/96, publ. 10.12.1975). Hydrogenation proceeds at a temperature of 60-140 ° C. After completion of the hydrogenation, the solvent is removed by vacuum distillation. The bottom residue is recrystallized from water to give 4-chloro-1,3-phenylenediamine with a melting point of 88-91 ° C and a purity of 97%. The yield of the target product 89% of theoretical. The disadvantage of this method is the low degree of purity of the product if it is used as a monomer in the preparation of a high molecular weight polymer.

It is also known that the main problem in the isolation of high-purity ortho-, meta-, and para-phenylenediamines is their tendency to oxidize with oxygen, which is always present in dissolved form in water and organic solvents. So 1,4-phenylenediamine and its derivatives substituted in the nucleus are easily oxidized to quinondiimine,

which further reacts with 1,4-phenylenediamine to form an indamine dye, which undergoes further transformations as a result of oxidation and condensation reactions [J.F. Corbett. J. Chem. Soc. Perkin Trans, II, 1972, No. 8, p.999-1005; A.A. Kiryushkin, I.N. Kovalchuk, X.M. Avanesova, A.Yu. Shibaev. Zhurn. org Chem., vol. XX, issue 5, 1052-1055 (1984)]

Therefore, when the chloro-substituted phenylenediamine is isolated by distillation of the solvent during heating, the oxidation and resinification of the target products proceed, accompanied by a decrease in the yield and deposition of resinous substances on the internal surfaces of the apparatus.

Closest to the proposed method is the method described in patent GB 1417662.

The objective of the invention is to improve the process for producing chloro-substituted phenylenediamines, which consists in improving their quality by preventing oxidation and the formation of condensation products during the isolation process.

The problem is solved by the proposed method for producing chlorine substituted phenylenediamines, for example, such as 4-chloro-1,3-phenylenediamine, 2-chloro-1,4-phenylenediamine, 2,6-dichloro-1,4-phenylenediamine, 2,5-dichloro -1,4-phenylenediamine by reduction of the corresponding chloro-substituted dinitrobenzenes or chloro-substituted nitroanilines in a solvent medium, followed by isolation of the target product.

The proposed method is characterized in that the solution of the reduction products after separation from the catalytic system or the reducing medium is treated with mineral acid, chlorine-substituted phenylenediamine is isolated in the form of a salt of a mineral acid, and then chlorine-substituted phenylenediamine is isolated as a free base by treatment of its salt with an alkaline agent in the presence of an antioxidant, followed by extraction with an organic solvent, and then from a solution in an organic solvent by crystallization.

As a solvent for the recovery process, one of the series is used: water, dimethylacetamide (DMAA), dimethylformamide (DMF), N-methylpyrrolidone (NMP), methyl alcohol, ethyl alcohol, isopropyl alcohol, mixtures of these solvents with water, ethyl acetate, benzene or toluene.

The reduction is carried out with hydrogen in the presence of a catalyst or iron. As a hydrogen reduction catalyst, platinum, palladium or other platinum group metals on a support are used, or palladium modified with nickel and iron on a support, or skeletal nickel or nickel-chromium. The recovery process can be carried out both periodically and continuously. The reduction with iron is carried out in an aqueous solvent in the presence of an electrolyte, for example NH ₄ Cl or FeCl ₂ .

As a mineral acid, one of a series of hydrochloric, sulfuric, phosphoric or gaseous hydrogen chloride is used.

Sodium hydroxide, potassium hydroxide, calcium hydroxide, calcium oxide, sodium carbonate, potassium carbonate, calcium carbonate, sodium sulfite, potassium sulfite are used as an alkaline agent for the isolation of chlorine-substituted phenylenediamine from salt.

Sodium sulfite (Na ₂ SO ₃ ) or potassium sulfite (K ₂ SO ₃ ) or sodium pyrosulfite (Na ₂ S ₂ O ₅ ) or hydrazine hydrate are used as an antioxidant in the process of isolating chloro-substituted phenylenediamine from salt.

One of the series methylene chloride, chloroform, ethyl acetate, benzene, toluene, hexane, heptane, petroleum ether, gasoline-solvent (nefras) or a mixture of solvents from the series are used as an organic solvent for extraction during the extraction of chlorine-substituted phenylenediamine from salt.

In order to more fully isolate the chloro-substituted phenylenediamine mineral salt after reduction from solvents such as amide, water or mixtures thereof, the solubility of the chloro-substituted phenylenediamine mineral salt can be reduced by adding solvents in which these salts are poorly soluble. Such solvents include lower aliphatic alcohols, acetone, aliphatic and aromatic hydrocarbons (table).

If necessary, the salts of chloro-substituted phenylenediamines can be purified by recrystallization from aqueous solutions of the corresponding acids in the presence of activated carbon. In this case, the acid mother liquors formed after separation of the salt can be used again to recrystallize a new portion of salt. Thus, low-waste salt recrystallization stage is achieved.

The proposed method allows to significantly improve the process of obtaining chlorine-substituted phenylenediamine, prevents gumming in the process of isolation, provides improved product quality. The salts of mineral acids of chlorine-substituted phenylenediamines are stable when stored in air, they can be accumulated and used as necessary, while when storing free chlorine-substituted phenylenediamines, special precautions must be taken, which still do not provide sufficient stability of the target products

The invention is illustrated by the following examples, which are not intended to give an exhaustive description of the method.

Example 1. Synthesis of 4-chloro-1,3-phenylenediamine (HMFDA)

40.5 g of 4-chloro-1,3 are loaded into a stainless steel reactor with a capacity of 0.5 dm ³ , equipped with a stirrer, a jacket for heating and cooling, gas inlet and outlet fittings, a bottom valve, a heated filter and a solution receiver of hydrogenation products -dinitrobenzene, 150 cm ³ ethyl acetate, 100 cm ³ ethyl alcohol and 2.0 g of catalyst 2% Pt / C. Recovery is carried out at a temperature of 50-110 ° C under a hydrogen pressure of 5.0 MPa. After the absorption of hydrogen is complete, the hydrogenation product solution is filtered off from the catalyst and 23 cm ^{3 of} 60% sulfuric acid is introduced, which corresponds to a 5% molar excess with respect to the theoretical amount of 4-chloro-1,3-phenylenediamine (HMFDA). A precipitate of 4-chloro-1,3-phenylenediamine monosulphate salt (HMFDA · H ₂ SO ₄ ) immediately precipitated with a lilac hue. The suspension is filtered off with suction, the salt precipitate is washed with alcohol and dried. The salt yield was 46.2 g (96% of theory), the sulfuric acid content (titrimetry) was 41% (100.6% of theory).

42.0 g of HMFDA · H ₂ SO ₄ salt is placed in 200 cm ^{3 of a} 2% aqueous solution of sodium sulfite (Na ₂ SO ₃ , reducing agent), and neutralized with an aqueous solution of sodium hydroxide to pH 7.5. The base of HMFDA is extracted with methylene chloride. The solvent is distilled off in a rotary evaporator. 22.9 g of 4-chloro-1,3-phenylenediamine (92% of theory) are obtained. White powder with a lilac shade. The melting point is 90-91 ° C, the content of the basic substance is 99.2% (determined by gas-liquid chromatography - GC).

Example 2. Synthesis of 4-chloro-1,3-phenylenediamine (HMFDA)

75 g of atomized iron powder, 50 cm ^{3 of} water, 10 cm ^{3 of} dimethylacetamide and 8 cm ^{3 of} concentrated hydrochloric acid are placed in a three-necked flask with a capacity of 250 cm ³ . The mixture is heated with stirring to 90 ° C and a solution of 30 g of 4-chloro-1,3-dinitrobenzene in 30 cm ^{3 of} dimethylacetamide is gradually introduced. The mixture is then stirred under heating for 0.5 hour, filtered from a precipitate of iron oxide, washed with a precipitate of iron hydroxide 20 cm ^{3 of} dimethylacetamide, attaching a wash filtrate to the main filtrate. The combined filtrates - a solution of HMFDA in aqueous dimethylacetamide are cooled to 10 ° C and 17.2 cm ^{3 of} 60% sulfuric acid are introduced. Then 100 cm ^{3 of} isopropyl alcohol are introduced and left in the refrigerator for 2 hours to mature the precipitate. The suspension of the salt is filtered, the precipitate of the salt is washed with isopropyl alcohol. The yield of HMFDA · H ₂ SO ₄ salt was 31.9 g (89.5%), the content of H ₂ SO _{4 was} 40.6% (99.6% of theory).

30.0 g of HMFDA · H ₂ SO ₄ salt is placed in 150 cm ^{3 of a} 2% aqueous solution of potassium sulfite (K ₂ SO ₃ , reducing agent) and neutralized with an aqueous solution of potassium hydroxide to pH 7.5. Base - HMFDA extracted with chloroform. The solvent is distilled off in a rotary evaporator. 16.7 g (94%) of HMFDA are obtained. White powder with a lilac shade. Melting point 90-91 ° C, basic substance content 99.0% (GC).

Example 3. Synthesis of 4-chloro-1,3-phenylenediamine (HMFDA)

The synthesis is carried out in the reactor described in example 1. 30 g of 2,4-dinitrochlorobenzene (DNCB), 300 cm ^{3 of} benzene and 2 g of 0.5% Pt / C catalyst are loaded into the reactor. Recovery is carried out at a temperature of 30-60 ° C and a hydrogen pressure of 5.0 MPa. After the absorption of hydrogen is complete, the hydrogenation product solution is filtered off from the catalyst. By distilling off 1/4 of the solvent, the reaction water is removed as an azeotrope with benzene and a stream of hydrogen chloride is passed into the dehydrated solution. 4-Chloro-1,3-phenylenediamine dihydrochloride is isolated from the solution as a white crystalline precipitate, which is filtered off and dried. Get 4-chloro-1,3-phenylenediamine dihydrochloride with a hydrogen chloride content of 33.86% of the mass. (Theoretical content of hydrogen chloride 33.84% by mass.). The yield of dihydrochloride is 31.45 g (98.5% of theory). By neutralizing the dihydrochloride in an aqueous suspension, using sodium carbonate as a neutralizing agent, sodium sulfite as an antioxidant, and benzene as an extractant, 17.31 g of 4-chloro-1,3-phenylenediamine are obtained (82% of theory on DNCB). Light gray powder with a lilac shade. Melting point 90-91 ° C. The basic substance content of 99.4% (GC).

Example 4. Synthesis of 2-chloro-1,4-phenylenediamine (HFPDA)

In the reactor described in example 1, load 19 g of 2-chloro-4-nitroaniline (XNA), 170 cm ³ ethyl acetate and 1.0 g of catalyst 2% Pt / C. Recovery is carried out at a temperature of 30-50 ° C and a hydrogen pressure of 2.0 MPa. After completion of hydrogen uptake, the solution of hydrogenation products is filtered off from the catalyst and treated with 20 cm ^{3 of} 36.0% hydrochloric acid. The suspension of 2-chloro-1,4-phenylenediamine dihydrochloride (DPC ChPPDA) is filtered, the precipitate is washed with 20% hydrochloric acid. DHPCHPDA - white powder. The content of hydrogen chloride 33.9% (theoretical content of hydrogen chloride 33.84% of the mass.). Yield 23.26 g (98% of theory).

20 g of DHC CPFDA salt is placed in 80 cm ^{3 of} benzene and neutralized with stirring with a 10% aqueous sodium hydroxide solution containing 1.5% sodium sulfite. The layers are separated, the aqueous layer is washed with 50 cm ^{3 of} benzene. Benzene extracts combine and distill benzene in a rotary evaporator. 12.7 g of CPPDA (96.0% of theory) are obtained. Crystal melt of white color with a light beige tint. Melting point 65.5 ° C. Chromaticity 1.0 units. The basic substance content of 99.8% (GC).

Example 5. Synthesis of 2-chloro-1,4-phenylenediamine (HFPDA)

In the reactor described in example 1, load 19 g of 2-chloro-4-nitroaniline, 170 cm ^{3 of} isopropyl alcohol and 1.0 g of the catalyst 0.5% Pt / C. Recovery is carried out at a temperature of 30-50 ° C and a hydrogen pressure of 2.0 MPa. After the completion of hydrogen absorption, the solution of hydrogenation products is filtered off from the catalyst and treated with 12.6 cm of 60% sulfuric acid. The monosulfuric salt of HFPDA (HPFDA · H ₂ SO ₄ ) immediately precipitates. The suspension is filtered, the precipitate is washed with isopropyl alcohol. White powder with a light lilac shade. Yield 25.97 g (98% of theory). The sulfuric acid content of 40.8% (100.1% of theoretical).

25.0 g of the salt of HFPDA · H ₂ SO _{4 is} placed in 80 cm ^{3 of a} 2% aqueous solution of sodium sulfite (Na ₂ SO ₃ , an antioxidant) and neutralized with an aqueous solution of sodium hydroxide to pH 7.5. Base - HPPDA is extracted at 50 ° C with a benzene: hexane mixture. The extract is cooled to 5 ° C. At the same time, CPFDA crystallizes. The suspension is filtered, the precipitate is washed with hexane and dried. Yield 13.8 g (93%). White crystalline powder with a slight lilac shade. Melting point 65.5 ° C, color 1.8. The basic substance content of 99.6% (GC).

Example 6. Synthesis of 2-chloro-1,4-phenylenediamine (HFPDA)

38 g of 2-chloro-4-nitroaniline, 170 cm ^{3 of} dimethylacetamide and 4.0 g of catalyst 0.5% Pt / Al ₁ O ₃ are charged into the reactor described in example 1. Recovery is carried out at a temperature of 40-50 ° C and a hydrogen pressure of 2.0 MPa. After completion of hydrogen uptake and separation of the catalyst, 200 cm ^{3 of} isopropyl alcohol and 25.2 cm ^{3 of} 60% sulfuric acid are introduced into the hydrogenate. The precipitated monosulphate salt of HFPDA · H ₂ SO _{4 is} filtered off and washed with acetone. White powder. The yield of salt HFDA · H ₂ SO ₄ 51,4 g (97% of theory). The content of H ₂ SO ₄ in the salt is 40.8% (100.1% of theory).

40.0 g of the salt of HFPDA · H ₂ SO _{4 is} placed in 130 cm ^{3 of a} 2% aqueous solution of sodium sulfite, 100 cm ^{3 of} benzene is introduced and neutralized with an aqueous solution of sodium hydroxide to pH 7.5. The benzene layer is separated. The aqueous layer is washed with another 100 cm ^{3 of} benzene. The benzene extracts are combined, evaporated in a rotary evaporator to half the initial volume. The concentrate is cooled, precipitated crystals of HFPDA are filtered off and dried. Yield 19.4 g (82% of theory). White crystalline powder with a purple tint. Melting point 65 ° C. Chromaticity of 1.8 units. The basic substance content of 99.8% (GC).

From the benzene mother liquor, an additional amount of the product is isolated, which is subjected to purification.

Example 7. Synthesis of 2-chloro-1,4-phenylenediamine (HFPDA)

The synthesis is carried out as described in example 6, using 0.8% Pd / C as a catalyst. Obtain 50.3 g (94.9% of theory) of a salt of HFPDA · H ₂ SO ₄ . White powder. The content of H ₂ SO ₄ in the salt is 40.84% (100.2% of theory). 40 g of the salt of HFPDA · H ₂ SO _{4 is} neutralized as described in Example 6. 19.0 g of HFPDA (80.3% of theory) are obtained. White crystalline powder with a purple tint. Melting point 65 ° C. Chromaticity of 2.3 units. The basic substance content of 99.2% (GC).

Example 8. Synthesis of 2-chloro-1,4-phenylenediamine (HFPDA)

The synthesis is carried out similarly to that described in example 6, using a mixed catalyst NPF-1 0.2% Pd as a catalyst; 0.2% Ni; 0.2% Fe / C. Obtain 50.1 g of salt HFPDA · H ₂ SO ₄ (94.5% of theory). White powder. The content of H ₂ SO ₄ in the salt is 40.80% (100.1% of theory). 40 g of the salt of HFPDA · H ₂ SO _{4 is} neutralized as described in Example 6. 19.2 g of HFPDA (81.1% of theory) are obtained. White crystalline powder with a purple tint. Melting point 65 ° C. Chromaticity 3.4 units. The basic substance content of 99.3% (GC).

Example 9. Synthesis of 2-chloro-1,4-phenylenediamine (HFPDA)

The synthesis is carried out similarly to that described in example 6, using skeletal nickel (Raney nickel) as a catalyst. Obtain 49.7 g (93.2% of theory) of a salt of HFPDA · H ₂ SO ₄ . The content of H ₂ SO ₄ in the salt is 40.84% (100.2% of theory). White powder. 40 g of the salt of HFPDA · H ₂ SO _{4 is} neutralized as described in Example 6. 18.9 g of HFPDA are obtained (79.8% of theory). White crystalline powder with a purple tint. Melting point 65 ° C. Chromaticity of 2.8 units. The basic substance content of 99.1% (GC).

Example 10. Synthesis of 2-chloro-1,4-phenylenediamine (HFPDA)

Catalytic hydrogenation is carried out in the reactor described in example 1.

38 g of 2-chloro-4-nitroaniline 170 cm ^{3 of} ethyl acetate and 4 g of catalyst 0.5% Pt / Al ₂ O ₃ are charged into the reactor. Recovery is carried out at a temperature of 40-50 ° C and a hydrogen pressure of 2.0 MPa. After completion of hydrogen uptake and separation of the catalyst, 15.7 g of 88.5% phosphoric acid is added dropwise to the hydrogenate. The temperature of the solution rises from 30 to 34 ° C. A few minutes after the end of the addition of phosphoric acid, a white precipitate begins to precipitate. After cooling in the refrigerator for 2 hours at 10 ° C, the suspension is filtered, the filter cake washed with ethyl acetate and dried. The yield of monophosphate salt of HFPDA · H ₃ PO ₄ 51.94 g (98% of theory). The powder is white. The content of H ₃ PO _{4 is} 40.732% (100.0% of theory).

40 g of the salt of HFPDA · H ₃ PO _{4 is} placed in 130 cm ^{3 of a} 2% aqueous solution of potassium sulfite, 100 cm ^{3 of} ethyl acetate is introduced and neutralized with an aqueous solution of potassium hydroxide to a pH of 7.5. The ethyl acetate layer was separated. The aqueous layer was washed with 100 cm ³ ethyl acetate. The ethyl acetate extracts are combined and the ethyl acetate is distilled off in a rotary evaporator. The yield of HPPDA 21.1 g (97.5% of theoretical). White crystalline melt with a beige tint. Melting point 65 ° C, chroma 1.2 units. The basic substance content of 99.7% (GC).

Example 11. Synthesis of 2-chloro-1,4-phenylenediamine (HFPDA)

In a three-necked flask with a capacity of 1 dm ³ , equipped with a stirrer, reflux condenser and thermometer, 600 cm ^{3 of} water, 117 g of iron powder and 10 cm ^{3 of} concentrated hydrochloric acid are charged. The mixture is heated with stirring and 78 g of 2-chloro-4-nitroaniline are gradually introduced. After complete addition, the mass is heated for another 0.5 hours with stirring. The solution of reduction products is separated from the iron sludge and 52 cm ^{3 of} 60% sulfuric acid are gradually introduced into it. Immediately a white precipitate of the salt of HFPDA · H ₂ SO _{4 is released} . The salt suspension is filtered, the precipitate is washed with water. The yield of monosulphate salt of HFDA · H ₂ SO _{4 is} 94.7 g (87% of theory). The content of H ₂ SO ₄ in salt is 41.1% of the mass. (100.9% of theoretical).

80 g of salt HFDDA · H ₂ SO ₄ are placed in 260 cm ^{3 of a} 2% aqueous solution of sodium sulfite, injected with 200 cm of benzene and neutralized with an aqueous solution of sodium hydroxide to pH 8.0. The benzene layer is separated. The aqueous layer is washed with another 100 cm ^{3 of} benzene. The benzene extracts are combined, evaporated in a rotary evaporator. The concentrate is cooled, precipitated crystals of HFPDA are filtered off and dried. The yield of HFAFD is 40.7 g (85.9% of theory). White crystalline powder with a slight lilac shade. Melting point 65.0 ° C. Chroma 1.6 units The basic substance content of 99.8% (GC).

Treatment of the benzene mother liquor with 60% sulfuric acid gives an additional amount of CPPDA · H ₂ SO ₄ .

Example 12. Synthesis of 2,6-dichloro-1,4-phenylenediamine (2,6-DCPFDA)

In a three-necked flask with a capacity of 500 cm ³ , equipped with a stirrer, reflux condenser and thermometer, 150 cm ^{3 of} water, 150 cm ^{3 of} dimethylacetamide, 30 g of iron powder and 2 cm ^{3 of} concentrated hydrochloric acid, which, interacting with iron, give an electrolyte - iron chloride FeCl ₂ . The mixture is heated to boiling with stirring, cooled to 90 ° C, and 36.0 g of 2,6-dichloro-4-nitroaniline (2,6-DHNA) are gradually introduced. The reaction mass is filtered while hot from iron sludge in a nitrogen atmosphere and 156 cm ^{3 of} 36.3% hydrochloric acid are added to the filtrate. The suspension of 2,6-dichloro-1,4-phenylenediamine dihydrochloride (DHC 2,6-DCPFDA) is filtered, the precipitate is washed with 20% hydrochloric acid. The salt of DHC 2,6-DHPFDA is a white powder, the content of hydrogen chloride is 29.25% of the mass. (theoretical content of hydrogen chloride 29.2% of the mass.). Yield 40.0 g (92% of theory).

30 g of 2,6-DHPFDA DHA salt is placed in 100 cm ^{3 of a} 2% aqueous solution of sodium sulfite, 100 cm ^{3 of} chloroform is introduced and neutralized with an aqueous solution of sodium hydroxide to pH 7.5. The chloroform layer is separated. The aqueous layer is washed with 50 cm ^{3 of} chloroform. From the combined chloroform extracts, the solvent is distilled off in a rotary evaporator. The yield of 2,6-DCPDDA was 18.9 g (89.0% of theory). White crystalline powder. Melting point 124 ° C. The basic substance content of 99.1% (GC).

Example 13. Synthesis of 2,5-dichloro-1,4-phenylenediamine (2,5-DCPFDA)

Recovery is carried out as described in example 12, using 36.0 g of 2,5-dichloro-4-nitroaniline. The separation of 2,5-dichloro-1,4-phenylenediamine dihydrochloride (DHC 2,5-DCPFDA) from the solution of reduction products is carried out after separation of the iron sludge, while under stirring, 30 g of hydrogen chloride gas are bubbled through a bubbler layer under stirring. The precipitated crystals of DHC 2,5-DCPFDA are filtered off. DHC 2,5-DHPFDA - white powder. The content of hydrogen chloride is 29.3% by weight (100.34% of theoretical), the yield is 41.3 g (95% of theoretical). By neutralizing 30.0 g of the salt of DHC 2,5-DCPDDA, similarly to that described in Example 12, 19.8 g of 2,5-DCPDDA are obtained (93.2% of theory). Crystalline powder. Melting point 165 ° C. The basic substance content of 99.3% (GC).

Table Solubility of 2-chloro-1,4-phenylenediamine (CPPDA) and its salts at 25 ° C №№ pp Solvent Solubility,% mass Hpfda HPPDA2HCl HFPDAH ₂ SO ₄ HFPDAH ₃ PO ₄ one Acetone > 50.0 0,03 0,07 0.04 2 Methanol > 56.0 3.05 3 Isopropanol 16.7 0.14 0.01 0.04 four Benzene 8.3 not soluble not soluble 5 Toluene 5.5 not soluble not soluble 6 Bezin solvent 0.015 not soluble not soluble 7 Ethyl acetate 18.2 0.11 0.01 8 Dimethylformamide > 50.0 6.3 9 Dimethylacetamide > 50.0 12.30 1,04 6.19 10 Water 5.3 30.00 0.63 2.89 eleven 20% hydrochloric acid - 0.63 - - 12 30% hydrochloric acid - 0.15 - - 13 18% acid - - 0.67 (17 ° C) -

Claims (8)

1. The method of producing chlorine-substituted phenylenediamines by reduction of the corresponding chloro-substituted nitroanilines or dinitrobenzenes in a solvent medium, followed by isolation of the target product, characterized in that the solution of the reduction products is treated with mineral acid, the formed salt is separated from the solvent and then transferred to the base by treatment with an alkaline agent in the presence of an antioxidant followed by extraction and crystallization. 2. The method according to claim 1, characterized in that one of the series is used as a recovery solvent: water, dimethylacetamide or a mixture of dimethylacetamide with water, dimethylformamide or a mixture of dimethylformamide with water, methyl alcohol, ethyl alcohol, isopropyl alcohol, ethyl acetate, benzene or toluene. 3. The method according to claim 1, characterized in that the reduction is carried out with hydrogen in the presence as a catalyst of platinum, or palladium, or other platinum group metals on a support or palladium modified with nickel or iron, on a support, or skeletal nickel, or nickel- chrome. 4. The method according to claim 1, characterized in that the reduction is carried out by iron in an aqueous solvent in the presence of an electrolyte. 5. The method according to claim 1, characterized in that the separation of the chlorine-substituted phenylenediamine salt from the solution of the reduction products is carried out in the presence of acetone or lower aliphatic alcohol. 6. The method according to claim 1, characterized in that as a mineral acid use hydrochloric acid, or sulfuric acid, or phosphoric acid, or gaseous hydrogen chloride. 7. The method according to claim 1, characterized in that sodium sulfite or potassium sulfite or sodium pyrosulfite is used as an antioxidant. 8. The method according to claim 1, characterized in that the extraction of the chlorine-substituted phenylenediamine is carried out with an organic solvent, one of the series: methylene chloride, chloroform, ethyl acetate, benzene, toluene, aliphatic hydrocarbon or a mixture of solvents from the series.