CH659065A5 - METHOD FOR PRODUCING 4,4'-DINITROSTILBEN-2,2'-DISULPHONIC ACID OR A SALTS THEREOF. - Google Patents

Description

The invention relates to a process for the preparation of l-naphthol-4-sulfonic acid, which contains only extremely small amounts of l-naphthol-2-sulfonic acid, by sulfonating 1-naphthol.

The sulfonation of 1-naphthol with sulfuric acid, oleum, sulfur trioxide or chlorosulfonic acid alone produces l-naphthol-4-sulfonic acid, l-naphthol-2-sulfonic acid and at the same time l-naphthol-2,4-disulfonic acid and l-naphthol-2 , 4,7-trisulfonic acid. In order to obtain the highest possible yields of monosulfonic acids, the sulfonations are therefore carried out in such a way that part of the 1-naphthol used remains unreacted.

The oversulfonation can also be suppressed or completely avoided by working in solvents, so that the 1-naphthol can be largely implemented. Solvents are used which do not react with the sulfonating agent under the reaction conditions, e.g. B. Acetic acid (M. Conrad and W. Fischer, Ann. 273,107), tetrachloroethane, benzene and nitrobenzene (British Patent 186 515) and other nitrated and halogenated organic solvents (Japan. Kokai 7 368 556, Japan. Kokai 7 535147, Japan Kokai 7577353).

For many uses (coupling to azo dyes), the Nevile-Winther acid has to be low in l-naphthol-2-sulfonic acid and 1-naphthol, while 1-naphthol-di- and -trisul-fonic acid does not interfere as they also Do not couple diazonium salts. 5 The proportions of l-naphthol-4-sulfonic acid and 1-naphthol-2-sulfonic acid can also be influenced by appropriate selection of the test conditions. British Patent 186 515 states that when sulfonating 1-naphthol with chlorosulfonic acid in tetrachloroethane at 0 to 10 50 ° C., mainly 1-naphthol-4-sulfonic acid is formed. N. Tat-suaki et al. a. (Yuki Gosei Kagaku Kyokai Shi 1972,30,545-8)

have found that the distribution of isomers depends on the reaction temperature. At low temperature (approx. 0 ° C) more l-naphthol-2-sulfonic acid is produced than l-naphthol-4-sulfonic-15 acid, at higher temperature (> 45 ° C) mainly l-naphthol-4-sulfonic acid is produced. To Japan. Kokai 7 368 556 1-naphthol-2-sulfonic acid can also be converted to l-naphthol-4-sulfonic acid by heating in an organic solvent in the presence of acid.

20 Organic solvents are used in all known processes only to influence the sulfonation reaction. The separation of the

1-Naphthol-2-sulfonic acid by fractional salting out of a finally aqueous solution of 1-naphthol sulfonic acid.

25 One takes advantage of the fact that the alkali and alkaline earth salts of l-naphthol-2-sulfonic acid are somewhat less soluble in water than those of l-naphthol-4-sulfonic acid. In this way, however, in the most favorable cases, only reaction mixtures which still contain 5 to 10% of the 30 reaction yield l-naphthol-2-sulfonic acid could be obtained.

The known cleaning processes are complex and the amounts of salt used place a heavy burden on the waste water. In addition, l-naphthol-2-sulfonic acid is also used to precipitate l-naphthol-4-sulfonic acid, so that the yield is reduced.

It has now been found that in the preparation of 1-naphthol-4-sulfonic acid by sulfonation of 1-naphthol in organic solvents in which l-naphthol-4-sulfonic acid is poorly soluble, the 1- 40 naphthol-2-sulfonic acid and the unreacted 1-naphthol largely remain in solution and can be separated from the l-naphthol-4-sulfonic acid which precipitates as a solid by filtration, whereby the quantitative ratio of l-naphthol-4-sulfonic acid to l- Naphthol-2-sulfonic acid can be increased significantly.

The process according to the invention for the preparation of 1-naphthol-4-sulfonic acid which contains less than 2% by weight of 1-naphthol

Contains 2-sulfonic acid, is carried out by sulfonating 1-naphthol in solvents largely inert to sulfonating agents.

50 parts in which the solubility of l-naphthol-4-sulfonic acid is only 0.01 to 5.0% by weight and is characterized in that

that the 1-naphthol-4-sulfonic acid is filtered off immediately after sulfonation. The stated solubility interval refers to the temperature at which the reaction suspension is filtered.

In general, 2 to 50 times, especially 5 to 10 times the amount by weight of solvent (s), based on the 1-naphthol used. Suitable solvents are, for example, mononuclear aromatic hydrocarbons containing up to three chlorine atoms, preferably toluene, xylene, nitrobenzene, nitrotoluene, mono-, di- or trichlorobenzene, but also halogenated aliphatic hydrocarbons, preferably trichlorethylene, 1,1. 1- or 1,1,2-trichloroethane, tetrachlorethylene or 1,1,2,2-tetrachloroethane. 65 The solvent (mother liquor) that is still present in the solid after filtration can be displaced in a conventional manner by washing out with further solvent.

A further increase in purity by treating the solid with organic solvents can be done either by washing further or stirring the filter cake and filtering again. The amounts of solvent used for this depend on the solvency of the solvent and on the desired cleaning effect; their amount is generally 2 to 50 times the volume of the filter cake.

For such a further treatment of the solid, in addition to the solvents mentioned above, solvents can also be used which are not inert to the sulfonating agent, but have similar solution properties. Examples include alkyl aryl ethers, in particular anisole and phenetol.

In principle, sulfuric acid, oleum, sulfur trioxide and chlorosulfonic acid can be used as sulfonating agents. However, preference is given to using chlorosulfonic acid which, even when a slight excess is used, is completely consumed either by the formation of l-naphthol-2,4-disulfonic acid or by side reactions; most of the hydrogen chloride produced escapes as a gas. When using sulfuric acid, oleum or sulfur trioxide, both yields and purity are lower.

In general, the chlorosulfonic acid is used in a stoichiometric excess of up to 20% by weight. When using halogenated hydrocarbons or nitrated aromatics as solvents, the stoichiometric amount or a very small excess can be used; if toluene or xylene is used, an approximately 5 to 20 percent excess must be used because the latter solvents are also sulfonated to a small extent. The chlorosulfonic acid is preferably added dropwise to the mixture of 1-naphthol and solvent at temperatures from -20 to 120 ° C. When using inert or inert solvents, sulfonation can be carried out at high temperature. To establish a favorable isomer ratio in the reaction mixture, stirring is carried out in a manner known per se for several hours at temperatures above 50 ° C., preferably at 70 to 100 ° C., if appropriate when using solvents with a low boiling point under pressure.

After the sulfonation, the filtration is preferably also carried out at the temperatures mentioned (between 50 and 100 ° C.). According to the process of the invention, if the preferred experimental conditions are observed, a product is obtained which contains less than 0.5% l-naphthol-2-sulfonic acid and 1-naphthol and still 1 to 3% l-naphthol-2,4-disulfonic acid. based on l-naphthol-4-sulfonic acid.

The free 1-naphthol-4-sulfonic acid is generally obtained from the solvent-moist filter cake, if appropriate after displacing a high-boiling solvent by a solvent with a low boiling point, by simple drying at temperatures below 120 ° C., if appropriate in vacuo.

The process according to the invention overcomes a decades-old prejudice: l-naphthol-4-sulfonic acid is not obtained from the reaction mixture as a salt by dissolving it in water and fractionally salting it out, but directly after sulfonation, in a simple and substantially purer manner, by filtration and preferably washing out the filter residue with (a low-boiling) solvent.

The fact that the free l-naphthol-4-sulfonic acid is obtained by the process according to the invention and not a salt, as in the processes in which the reaction mixture is discharged onto ice / water and then l-naphthol-4-sulfonic acid is salted out this sulfonic acid is also a not insignificant advantage of the new process. The l-naphthol-4-sulfonic acid can also be aqueous in a manner known per se

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Solution of the free acid or an alkali salt or as a solid, saline sodium salt can be isolated by:

-Insert the filter cake in water or dilute alkali and separate the solvent by phase separation or distillation. The remaining aqueous solution of 4-naphthol sulfonic acid or the salt can be used for most purposes without further treatment;

- Enter the filter cake in water or dilute alkali, separate the solvent by phase separation or distillation and salt out the sodium salt of 1-naphthol-4-sulfonic acid from the aqueous solution by adding sodium chloride. After filtering off and washing with brine, a product is obtained which is practically free from organic contaminants; the l-naphthol-2,4-disulfonic acid remains dissolved in the filtrate.

example 1

73 g of 1-naphthol are sulfonated in 500 ml of chlorobenzene at 30 ° C. by slowly adding 60 g of chlorosulfonic acid, then the mixture is left to react at 80 ° C. for 4 h. In addition to l-naphthol-4-sulfonic acid, the reaction mixture contains 5% of theory of l-naphthol-2-sulfonic acid.

The reaction suspension is filtered and the mother liquor remaining in the filter cake is displaced with 400 ml of hot chlorobenzene. Drying in vacuo gives 1-naphthol-4-sulfonic acid in a yield of 92% of theory with a content of l-naphthol-2-sulfonic acid of <0.5% and with 3% 1-naphthol-2,4- disulfonic acid.

By stirring the solvent-moist filter cake in 200 ml of water and separating off the solvent, an aqueous solution of the product is obtained which, possibly after clarification, can be used as such.

In a further work-up variant, the aqueous solution thus obtained is mixed with 60 g of sodium chloride, the precipitated sodium salt of l-naphthol-4-sulfonic acid is filtered off and washed with 200 ml of brine. The sodium salt of 1-naphthol-4-sulfonic acid is thus obtained in a yield of 88% of theory and practically free from organic impurities.

Example 2

The procedure is as described in Example 1, but 1,2-dichlorobenzene is used instead of chlorobenzene. The reaction mixture contains 4% of theory 1-naphthol-2-sulfonic acid.

After working up as indicated in Example 1, 93% of theory of dry, free l-naphthol-4-sulfonic acid with <0.5% l-naphthol-2-sulfonic acid and 2% l-naphthol-2,4-disulfone are obtained. fonic.

Example 3

73 g of 1-naphthol and 60 g of chlorosulfonic acid are reacted in 500 ml of a trichlorobenzene isomer mixture, as described in Example 1. The reaction mixture contains 2% of theory 1-naphthol-2-sulfonic acid. After filtration and displacement of the mother liquor with 400 ml of hot trichlorobenzene, it is taken up in 300 ml of water and the solvent is separated off. The remaining aqueous solution contains 93% of theory 1-naphthol-4-sulfonic acid, 0.5% of theory 1-naphthol-2-sulfonic acid and 3% l-naphthol-2,4-disulfonic acid.

Example 4

The procedure is as described in Example 3, the mother liquor remaining in the filter cake after filtering the reaction suspension is displaced with 400 ml of chloroform instead of trichlorobenzene. Drying the solvent-moist filter cake gives 92% of theory dry, free 1-naphthol-4-sulfonic acid with a content of l-naphthol-2-sulfonic acid of <5% and with 1% l-naphthol-2,4- disulfonic acid.

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Example 5

73 g of 1-naphthol are sulfonated in 700 ml of toluene at 0 ° C. by slowly adding 61 g of chlorosulfonic acid, then the mixture is left to react at 80 ° C. for 4 h. The reaction mixture contains 5% of theory of 1-naphthol-2-sulfonic acid. The reaction suspension is filtered and the mother liquor remaining in the filter cake is displaced with 500 ml of toluene.

After working up as indicated in Example 1, 88% of theory 1-naphthol-4-sulfonic acid with 1-naphthol and l-naphthol-2-sulfonic acid content of 0.5% and with 2% l-naphthol-2,4- disulfonic acid, or 88% of theory 1-naphthol-4-sulfonic acid sodium salt, which is practically free of organic impurities.

Example 6

73 g of 1-naphthol and 60 g of chlorosulfonic acid are reacted in 700 ml of benzene, as indicated in Example 5. The reaction mixture contains 7% l-naphthol-2-sulfonic acid. After working up 87% of theory dry, free 1-naphthol-4-sulfonic acid with 1% l-naphthol-2-sulfonic acid and 3% l-naphthol-2,4-disulfonic acid are obtained.

Example 7

73 g of 1-naphthol and 65 g of chlorosulfonic acid are reacted in 700 ml of a xylene isomer mixture, as indicated in Example 5. The reaction mixture contains 2% l-naphthol-2-sulfonic acid. After working up, 80% of theory of dry, free l-naphthol-4-sulfonic acid with <0.5% 1-naphthol-2-sulfonic acid and 0.5% l-naphthol-2,4-disulfonic acid are obtained.

Example 8

73 g of 1-naphthol are sulfonated in 300 ml of 1,1,2-trichloroethane at 50 ° C. by slowly adding 60 g of chlorosulfonic acid, then the mixture is left to react at 80 ° C. for 4 h. The reaction mixture contains 7% l-naphthol-2-sulfonic acid. The reaction mixture is filtered and the mother liquor remaining in the filter cake is displaced with 300 ml of 1,1,2-trichloroethane.

Drying gives 80% of theory free 1-naphthol-4-sulfonic acid with 1% 1-naphthol-2-sulfonic acid with 1% 1-naphthol-2,4-disulfonic acid.

Example 9

73 g of 1-naphthol and 60 g of chlorosulfonic acid are reacted in 800 ml of 1,1,2,2-tetrachloroethane at 50 ° C., then the mixture is stirred at 80 ° C. for 4 h. There are 4% of theory 1-5 naphthol-2-sulfonic acid. The reaction mixture is filtered and the mother liquor remaining in the filter cake is displaced with 500 ml of 1,1,2,2-tetrachloroethane. Drying gives 90% of theory free l-naphthol-4-sulfonic acid with <0.5% 1-naphthol-2-sulfonic acid and 2% l-naphthol-2,4-disulfonic acid.

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Example 10

73 g of 1-naphthol and 65 g of chlorosulfonic acid are reacted in 600 ml of chloroform at the boiling point (60 ° C.) and stirred for 10 h at the boiling point. There are 10% 1-15 naphthol-2-sulfonic acid. The reaction mixture is filtered and the mother liquor remaining in the filter cake is displaced with 500 ml of chloroform.

Drying gives 80% of theory free 1-naphthol-4-sulfonic acid with <0.5% l-naphthol-2-sulfonic acid and 20 <0.5% l-naphthol-2,4-disulfonic acid.

Example 11

73 g of naphthol and 60 g of chlorosulfonic acid are reacted in 500 ml of 25 trichloroethane at the boiling point (90 ° C.) and the mixture is subsequently stirred at the boiling point for 2 h. There are 3% l-naphthol-2-sulfonic acid. The reaction mixture is filtered and the mother liquor remaining in the filter cake is displaced with 300 ml of trichlorethylene. The filter cake still contains 30 l-naphthol-2-sulfonic acid corresponding to a yield of 2% of theory.

For further cleaning, the filter cake is boiled out with 500 ml of trichlorethylene and filtered.

Drying gives 90% of theory free 1-naphth-35 thol-4-sulfonic acid with% 1-naphthol-2-sulfonic acid and 3% 1-naphthol-2,4-disulfonic acid.

Example 12

The procedure is as described in Example 11, but the further 40 cleaning of the filter cake is carried out by stirring with 500 ml of anisole and filtration. Drying gives 89% of theory free 1-naphthol-4-sulfonic acid with <0.5% 1-naphthol-2-sulfonic acid with 3% l-naphthol-2,4-disulfonic acid.

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Claims (10)

659 064 PATENT CLAIMS 1. Process for the preparation of l-naphthol-4-sulfonic acid, which contains less than 2% by weight of l-naphthol-2-sulfonic acid, by sulfonating 1-naphthol in solvents largely inert to sulfonating agents, in which the solubility of l -Naphthol-4-sulfonic acid is only 0.01 to 5.0 wt .-%, this interval of solubility relates to the temperature at which the filtration of the reaction suspension is carried out, characterized in that the immediately after sulfonation Filtered l-naphthol-4-sulfonic acid at these temperatures. 2. The method according to claim 1, characterized in that 2 to 20 times the amount by weight of solvent), based on 1-naphthol, is used. 3. The method according to claim 1 or 2, characterized in that optionally one to three chlorine atoms containing mononuclear aromatic hydrocarbons are used as the solvent. 4. The method according to claim 3, characterized in that toluene, xylene, nitrobenzene, nitrotoluene, mono-, di- or trichlorobenzene is used as the solvent. 5. The method according to claim 1 or 2, characterized in that halogenated aliphatic hydrocarbons are used as the solvent. 6. The method according to claim 5, characterized in that trichlorethylene, 1,1,1- or 1,1,2-trichloroethane, tetrachlorethylene or 1,1,2,2-tetrachloroethane is used. 7. The method according to any one of claims 1 to 6, characterized in that the sulfonating agent is chlorosulfonic acid in a stoichiometric excess of up to 20% by weight. 8. The method according to any one of claims 1 to 7, characterized in that one carries out the filtration of the reaction suspension at temperatures between 50 and 100 ° C. 9. The method according to any one of claims 1 to 8, characterized in that the filtered off l-naphthol-4-sulfonic acid is treated for cleaning with a solvent in which the solubility of l-naphthol-4-sulfonic acid 0, 01 to 5 wt .-%, but this need not be inert to sulfonating agents. 10. The method according to claim 9, characterized in that an alkyl aryl ether, in particular anisole or phenetol, is used as the solvent.