JPH0753507A - Production of p-aminothiophenol - Google Patents

Abstract

PURPOSE:To provide a method for industrially and advantageously producing p-aminothiophenol in high purity and yield by using a surfactant. CONSTITUTION:This method for producing p-aminothiophenol is to react p- chloronitrobenzene with sodium sulfide in an aqueous solution containing a surfactant and neutralize the resultant reactional solution with an acid. In this case, the time of dropping an aqueous solution of sodium sulfide into a reactional vessel is >=4hr and an organic carboxylic acid is used for the neutralization. The pH of the reactional solution is regulated to 5.5-6.5.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention provides P-aminothiophenol, which is useful as a raw material intermediate for pharmaceuticals, agricultural chemicals, engineering plastics, etc., industrially with P-chloronitrobenzene and sodium sulfide in a higher yield and a higher purity. It relates to a method of manufacturing advantageously.

[0002]

2. Description of the Related Art Conventionally, as a method for producing thiophenols, a heterogeneous solvent composed of water adjusted to be alkaline and a water-insoluble organic solvent is treated with a water-insoluble organic solvent which may contain water, There is a method for producing thiophenols by hydrocracking di- or polysulfide in the presence of a Raney-Nickel catalyst. (JP-A-60-199871)

Further, in a method of hydrogen-reducing a sulfide compound or a nitro compound using a sulfide catalyst of metals of Groups 6 to 8 of the periodic table, the metal of the above-mentioned metal supported on an alkali-treated carrier is used as the catalyst. There is a method of using sulfide. (JP-A-56-81541)

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention JP-A-60-199871
JP-A-56-56
Both of the methods described in Japanese Patent Publication No. -81514 have the problem that they are industrially disadvantageous because the raw materials must be separately synthesized, isolated and purified, and the number of steps is large and the yield is low. . In view of the above, the present invention has an object to industrially advantageously produce P-aminothiophenol with a high purity and a high yield as compared with the above-mentioned conventional method using a surfactant. is there.

[0005]

The present inventors have succeeded in a method for producing industrially advantageous P-aminothiophenol by solving various problems of the conventional method and simplifying the method.
The present invention is a method for producing P-aminothiophenol, which comprises reacting P-chloronitrobenzene and sodium sulfide in an aqueous solution containing a surfactant and neutralizing with an acid. This is a production method in which the dropping time into the reaction vessel is set to 4 hours or more, and the acid used for neutralization is an organic carboxylic acid, and the reaction solution P
The present invention provides a method for producing P-aminothiophenol, which is characterized by adjusting H to 5.5 to 6.5. The reaction temperature is preferably 50 to 70 ° C. The reaction formula for synthesizing P-aminothiophenenoxy sodium from P-chloronitrobenzene and sodium sulfide is as shown in the following reaction formula (I) and
According to (II).

[0006]

[Reaction formula (I)]

[0007]

[Reaction formula (II)]

As shown in the above reaction formulas (I) and (II), in the present invention, the substitution reaction of the chloro atom first occurs to produce sodium nitrothiof enoxy, and then the nitro group is reduced to give aminothiof. Enoxy sodium is produced. However, part of P-chloronitrobenzene undergoes a reduction reaction of the nitro group, and P-chloroaniline is produced. P-
When chloraniline is formed, it does not undergo a substitution reaction and becomes a by-product, resulting in a decrease in yield. The present inventors have found that the addition of a surfactant in this case can suppress the production of side reactions.

Examples of the surfactant used in the present invention include fatty acid salts, alkyl sulfonates, and alkylnaphthalene sulfonates. Sodium n-dodecyl sulfate is preferably used, and the amount thereof is P-chloro. 0.5-2% by weight, preferably 1-1.5% by weight, based on nitrobenzene
Is. No surfactant is used or the amount used is 0.
If it is less than 5% by weight, a by-product is produced and the yield is remarkably low, and even if it is used in excess of 2% by weight, it does not contribute to the increase of the yield, so the upper limit is 2% by weight.

In the general method of the reaction of the present invention, P-chloronitrobenzene, the above-mentioned surfactant and water are charged in a reaction vessel in advance and replaced with nitrogen gas. The temperature is raised with stirring to a predetermined temperature, and then an aqueous solution of 15 to 20% by weight of sodium sulfide is added dropwise at a constant rate at 50 to 70 ° C, preferably about 60 ° C, over 4 hours. Sodium sulfide is used as an aqueous solution, and its concentration is 15 to 20% by weight, preferably 16 to 18% by weight. If the concentration is lower than 15% by weight, the productivity will be poor, and if the concentration is higher than 20% by weight, the crystals will be precipitated and the operability will be poor. If sodium sulfide is mixed with P-chloronitrobenzene from the beginning and reacted, the production of by-product P-chloroaniline increases and the reaction may run away. If sodium sulfide is added dropwise in a shorter period of time, heat generation will be large, temperature control will be difficult, and by-products will increase and the yield will decrease. As a result of various studies, the present invention has led to the discovery of the above reaction method.

After the dropping of the sodium sulfide aqueous solution, aging is carried out at a similar temperature for a predetermined time to complete the substitution reaction of chloro atoms of P-chloronitrobenzene, and then the temperature is raised to 90 ° C. or more and the temperature is maintained for 4 hours or more. Then, the nitro group is reduced. If the temperature during the reduction reaction is lower than 90 ° C, the reaction rate is slow, and preferably 100 to 105 ° C. The reduction reaction time is 4 hours or longer, preferably 6 hours or longer.
If it is shorter than 4 hours, the yield will decrease. After completion of the reduction reaction, the mixture is cooled and toluene is added to remove P-chloroaniline as a by-product. Salt is added to the aqueous layer to make it saturated, and the mixture is dropped into a container containing a predetermined amount of toluene and glacial acetic acid. Further, glacial acetic acid is added for neutralization, the pH is adjusted to a predetermined pH, and the toluene layer is separated. After extraction with toluene again, the toluene layers are combined and the toluene is distilled off, and then rectified to obtain P-aminothiophenol. By this method, the production of by-products could be suppressed.

The temperature for the reduction reaction of the above nitro group is 90 ° C. or higher. If the temperature is lower than this, the reaction rate is low and it is not industrially feasible. The reaction temperature is preferably 100 to 105 ° C. Further, the time of the reduction reaction is set to 4 hours or more, and if it is shorter than this, the yield is lowered. Although glacial acetic acid was used in the neutralization step, formic acid,
Organic acids such as acetic acid and propionic acid can be used, but glacial acetic acid is particularly preferable. It was found that by dropping water into glacial acetic acid, the -SH group became stable and P-aminothiophenol was obtained in high yield. The adjustment of PH is 5.5 to 6.5, and about 6.3 is particularly preferable. P
If H is higher or lower than the above, the yield will decrease.

[0013]

EXAMPLES The present invention will be described with reference to examples. With stirring 50
To a 0 ml four-necked flask, 60 g of water, 31.52 g (0.200 mol) of P-chloronitrobenzene and 0.3 g of sodium n-dodecyl sulfate as a surfactant were charged, and N ₂ substitution was carried out. This Na ₂ S · 9H ₂ O, those 124.8g of (0.520 mol) was dissolved in water 120 g, was added dropwise over 6 hours at 60 ° C.. After completion of the dropping, the mixture was further stirred at 60 ° C. for 1 hour, then the temperature was slowly raised to the reflux temperature (104 ° C.), and the reaction was carried out for 6 hours. The reaction mixture is cooled and 100 ml of toluene and NaCl are added.
Add 60 g, stir after stirring, and separate. The aqueous layer was added dropwise to a beaker containing 100 ml of toluene and 30 g of glacial acetic acid in advance. Adjust the pH to 6.3 with glacial acetic acid and separate. Extract again with 100 ml of toluene. The production rate of P-aminothiophenol in the obtained toluene layer was 90% by gas chromatography analysis. After toluene was distilled off from the toluene layer, rectification was performed to obtain 18.8 g of P-aminothiophenol. P
After the distillation of -aminothiophenol, the yield was 75% and the purity measured by gas chromatography was 98.1%.

[0014]

[Comparative Example 1] The same procedure as in Example was carried out except that the dropping condition of the aqueous sodium sulfide solution was 60 ° C for 2 hours. As a result, the production rate in the toluene layer was 60%, and the yield after distillation of P-aminothiophenol was 50%.

[0015]

[Comparative Example 2] The same procedure as in Example was carried out except that PH was adjusted to PH = 4.2. As a result, the production rate in the toluene layer was 83%, and the yield after distillation of P-aminothiophenol was 65%.

[0016]

The P-aminothiophenol produced by the method of the present invention has high purity in terms of quality. Since a surfactant is used and the amount of water used is small, the yield per reactor volume is large. That is, according to the present invention, highly pure P-aminothiophenol can be obtained in a higher yield than ever before, and the industrial value of the present invention is extremely large.

Claims (3)

[Claims] 1. A method for producing P-aminothiophenol, which comprises reacting P-chloronitrobenzene with sodium sulfide in an aqueous solution containing a surfactant and neutralizing with an acid. 2. The method for producing P-aminothiophenol according to claim 1, wherein the dropping time of the aqueous sodium sulfide solution into the reaction vessel is 4 hours or longer. 3. The method for producing P-aminothiophenol according to claim 1, wherein the acid used for neutralization is an organic carboxylic acid, and the pH of the reaction solution is adjusted to 5.5 to 6.5.