A method for synthesizing 4,4'-dichlorodiphenyl sulfoxide

Abstract

The invention discloses a method for synthesizing 4,4'-dichlorodiphenyl sulfoxide, and belongs to the technical field of organic synthesis. The method comprises the following steps: using chlorobenzene and thionyl chloride as raw materials and aluminum trichloride as a catalyst to carry out a Friedel-Crafts acylation reaction to prepare the 4,4'-dichlorodiphenyl sulfoxide; adding chlorobenzene in steps, controlling the reaction temperature between 25 and 10 DEG C, lowering the reaction temperature to reduce the selective activity of the ortho- and meta-positions of the benzene ring in the second step, thereby controlling the generation of by-products, and thus improving the reaction purity of the 4,4'-dichlorodiphenyl sulfoxide; and adding a sulfur dioxide solution to reduce the activity of the aluminum trichloride catalyst, further controlling the generation of by-products, and improving the reaction purity of the 4,4'-dichlorodiphenyl sulfoxide.

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthesis, and in particular relates to a method for synthesizing 4,4'-dichlorodiphenyl sulfoxide. Background Art

[0002] 4,4'-Dichlorodiphenyl sulfone is commonly used as a monomer for the preparation of polymers such as polyethersulfone or polysulfone, or as an intermediate for pharmaceuticals, dyes, and pesticides. 4,4'-Dichlorodiphenyl sulfone is prepared by oxidizing 4,4'-dichlorodiphenyl sulfoxide, which can be obtained by a Friedel-Crafts reaction of thionyl chloride and chlorobenzene as starting materials in the presence of a catalyst (e.g., aluminum chloride).

[0003] The main impurities in 4,4'-dichlorodiphenyl sulfoxide are 2,4'-dichlorodiphenyl sulfoxide and 3,4'-dichlorodiphenyl sulfoxide, with contents of about 1-10% and 0.5-15% respectively. These impurities are mainly caused by the excessive activity of aluminum chloride, resulting in poor selectivity, and excessive local heat during the reaction, resulting in poor selectivity. Currently, the purification of 4,4'-dichlorodiphenyl sulfoxide mainly involves recrystallization to remove the by-products 2,4'-dichlorodiphenyl sulfoxide and 3,4'-dichlorodiphenyl sulfoxide.

[0004] DE-A 3704931 describes a method for separating DCDPS (4,4'-dichlorodiphenyl sulfone) from a mixture comprising 0.5 to 20% by weight of 2,4'-dichlorodiphenyl sulfone and 0.5 to 30% by weight of 3,4'-dichlorodiphenyl sulfone by mixing the mixture with an alkanol, cooling it, and separating out the DCDPS for purification.

[0005] Due to their high boiling points, 2,4'-dichlorodiphenyl sulfoxide and 3,4'-dichlorodiphenyl sulfoxide are not suitable for distillation purification. The recrystallization purification process is cumbersome, with low yields, high production costs, and significant waste, waste, and product quality assurance. Summary of the Invention

[0006] To address the above-mentioned issues, the present invention provides a method for synthesizing 4,4'-dichlorodiphenyl sulfoxide. By adding a sulfur dioxide solution, the activity of the aluminum chloride catalyst is reduced, thereby lowering the activity of the Friedel-Crafts acylation reaction and controlling the formation of by-products. Furthermore, by lowering the reaction temperature, the selective activity at the ortho- and meta-positions in the second step is reduced, thereby increasing para-selectivity and improving product purity.

[0007] To achieve the above-mentioned purpose, the present invention is implemented through the following technical solutions:

[0008] A method for synthesizing 4,4'-dichlorodiphenyl sulfoxide comprises the following steps:

[0009] (a) adding thionyl chloride and aluminum chloride to a sulfur dioxide solution at -15 to -10°C, stirring and dissolving to obtain a mixed solution;

[0010] (b) The mixed solution obtained in step (a) is pumped into a static mixer for circulation, and chlorobenzene 1 is pumped into the static mixer at the same time. After the reaction is carried out at -15 to -10°C for 2 to 4 hours, chlorobenzene 2 is pumped into the mixed solution. After the addition is completed, the temperature is lowered to -25 to -20°C and the reaction is continued for 2 to 4 hours. After the reaction is completed, the temperature is raised to 25 to 30°C and stirred to release sulfur dioxide. After the sulfur dioxide is completely volatilized, deionized water is added to the obtained reaction solution, and the solution is heated to 80 to 100°C with stirring to quench the aluminum chloride. After the quenching reaction is completed, the temperature is lowered to 30 to 40°C, and the solution is filtered to obtain 4,4'-dichlorodiphenyl sulfoxide.

[0011] The mass ratio of the sulfur dioxide solution in step (a) to the chlorobenzene 1 in step (b) is 5-10:1.

[0012] The molar ratio of the aluminum chloride in step (a) to the chlorobenzene 1 in step (b) is 1-1.1:1.

[0013] The molar ratio of the chlorobenzene 1 in step (b) to the thionyl chloride in step (a) is 1:1-1.1.

[0014] The molar ratio of the chlorobenzene 2 in step (b) to the thionyl chloride in step (a) is 1-1.1:1.

[0015] The mass ratio of the deionized water added in step (b) to the aluminum chloride in step (a) is 5-10:1.

[0016] The aluminum chloride quenching reaction time in step (b) is 0.5 to 1 hour.

[0017] Preferably, in step (b), the mixture is heated to 80-90° C. under stirring to quench the aluminum chloride.

[0018] The synthetic route of 4,4'-dichlorodiphenyl sulfoxide of the present invention is:

[0019] .

[0020] The method for synthesizing 4,4'-dichlorodiphenyl sulfoxide of the present invention comprises the following steps: sulfur dioxide exists in a liquid form at -10°C at low temperature; experiments show that aluminum chloride is used as a catalyst, and a sulfur dioxide solution is added to reduce the catalyst activity and weaken the reaction activity; chlorobenzene and thionyl chloride are added at low temperature to first obtain p-chlorobenzenethionyl chloride; another portion of chlorobenzene is added at low temperature to further undergo Friedel-Crafts acylation reaction to obtain high-purity 4,4'-dichlorodiphenyl sulfoxide; and the method can discharge sulfur dioxide from the reaction system by heating and stirring in the later stage, add deionized water and stir to quench the aluminum chloride, and cool and filter to obtain high-purity 4,4'-dichlorodiphenyl sulfoxide.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1) The method for synthesizing 4,4'-dichlorodiphenyl sulfoxide of the present invention uses a sulfur dioxide solution as a low-boiling-point solvent, which can reduce the activity of the aluminum chloride catalyst, reduce the reaction activity, and thus reduce the generation of by-products. Furthermore, p-chlorophenylthionyl chloride is first obtained by stepwise addition of chlorobenzene at low temperature, and then further undergoes a Friedel-Crafts acylation reaction with chlorobenzene at low temperature to obtain high-purity 4,4'-dichlorodiphenyl sulfoxide. The low-temperature step-by-step reaction further reduces the selectivity for the ortho- and meta-positions of the benzene ring, and the para-position has higher selectivity than the ortho- and meta-positions, thereby reducing the generation of by-products and improving the purity of the product.

[0023] 2) The present invention utilizes the low boiling point of sulfur dioxide. The local heat in the reaction process can be carried away by the vaporization of sulfur dioxide, thereby solving the problem of the influence of poor heat transfer on the reaction selectivity.

[0024] 3) The present invention realizes small feed and large circulation by using a static mixer, which greatly improves the reaction rate.

[0025] 4) The method for synthesizing 4,4'-dichlorodiphenyl sulfoxide of the present invention comprises adding deionized water to quench the catalyst, cooling and filtering to obtain a high-purity 4,4'-dichlorodiphenyl sulfoxide product. After heating, sulfur dioxide is volatilized and discharged from the reaction system, and then condensed and recovered through a condensation device in an exhaust system for recycling, thereby achieving excellent environmental and economic benefits. The 4,4'-dichlorodiphenyl sulfoxide obtained by the present invention has a reaction purity greater than 99.8%, a 2,4'-dichlorodiphenyl sulfoxide content of less than 0.1%, and a 3,4'-dichlorodiphenyl sulfoxide content of less than 0.05%. The production process is safe and environmentally friendly, the product quality is excellent, and the product has extremely high industrial promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a liquid chromatogram of 4,4'-dichlorodiphenyl sulfoxide prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0027] In order to better understand the technical solutions of the present invention, the following is a further detailed description of the above content of the present invention through specific implementation methods in the form of examples. However, this should not be construed as limiting the scope of the above subject matter of the present invention to the following examples. All technologies implemented based on the above content of the present invention fall within the scope of the present invention.

[0028] Example 1 At -10°C, 0.125 kg of thionyl chloride and 0.133 kg of aluminum chloride were added to 0.56 kg of sulfur dioxide solution, and the mixture was stirred and dissolved to obtain a mixed solution;

[0029] The obtained mixed liquid was pumped into a static mixer for circulation. At the same time, 0.112 kg of chlorobenzene 1 was pumped into the static mixer. After the reaction was carried out at -10°C for 2 hours, 0.118 kg of chlorobenzene 2 was pumped into the static mixer. After the addition was completed, the temperature was lowered to -20°C and the reaction was continued for 2 hours. After the reaction was completed, the temperature was raised to 25°C and stirred to release sulfur dioxide. After the sulfur dioxide was released, 1 kg of deionized water was added to the obtained reaction liquid. The mixture was heated to 80°C with stirring to quench the aluminum chloride. After quenching the reaction for 0.5 hours, the reaction liquid was cooled to 30°C and filtered to obtain 0.266 kg of 4,4'-dichlorodiphenyl sulfoxide with a yield of 98.4% and a liquid phase purity of 99.9%.

[0030] Example 2 At -15°C, 0.262 kg of thionyl chloride and 0.294 kg of aluminum chloride were added to 2.25 kg of sulfur dioxide solution, and the mixture was stirred and dissolved to obtain a mixed solution;

[0031] The obtained mixed liquid was pumped into a static mixer for circulation. At the same time, 0.225 kg of chlorobenzene 1 was pumped into the static mixer. After the reaction was kept at -15 ° C for 4 hours, 0.248 kg of chlorobenzene 2 was pumped into it. After the addition was completed, the temperature was lowered to -25 ° C and the reaction was continued for 4 hours. After the reaction was completed, the temperature was raised to 30 ° C and stirred to release sulfur dioxide. After the sulfur dioxide was volatilized, 1.47 kg of deionized water was added to the obtained reaction liquid. It was heated to 100 ° C while stirring to quench the aluminum chloride. After quenching the reaction for 1 hour, the reaction liquid was cooled to 40 ° C and filtered to obtain 0.533 kg of 4,4'-dichlorodiphenyl sulfoxide with a yield of 98.4% and a liquid phase purity of 99.9%. Its liquid phase spectrum is as follows Figure 1 shown.

[0032] Example 3 At -13°C, 0.369 kg of thionyl chloride and 0.42 kg of aluminum chloride were added to 1.69 kg of sulfur dioxide solution, and the mixture was stirred and dissolved to obtain a mixed solution;

[0033] The obtained mixed liquid was pumped into a static mixer for circulation. At the same time, 0.338 kg of chlorobenzene 1 was pumped into the static mixer. After the reaction was kept at -12°C for 4 hours, 0.36 kg of chlorobenzene 2 was pumped into it. After the addition was completed, the temperature was lowered to -25°C and the reaction was continued for 4 hours. After the reaction was completed, the temperature was raised to 30°C and stirred to release sulfur dioxide. After the sulfur dioxide was completely volatilized, 2.5 kg of deionized water was added to the obtained reaction liquid. The mixture was heated to 90°C with stirring to quench the aluminum chloride. After the quenching reaction for 1 hour, the reaction liquid was cooled to 40°C and filtered to obtain 0.802 kg of 4,4'-dichlorodiphenyl sulfoxide with a yield of 98.5% and a liquid phase purity of 99.9%.

[0034] Example 4: At -11°C, 2.62 kg of thionyl chloride and 2.79 kg of aluminum chloride were added to 15 kg of sulfur dioxide solution, and the mixture was stirred and dissolved to obtain a mixed solution.

[0035] The obtained mixed liquid was pumped into a static mixer for circulation. At the same time, 2.25 kg of chlorobenzene 1 was pumped into the static mixer. After the reaction was carried out at -12°C for 3.5 hours, 2.48 kg of chlorobenzene 2 was pumped into the static mixer. After the addition was completed, the reaction liquid was cooled to -20°C and the reaction was continued for 2.5 hours. After the reaction was completed, the temperature was raised to 28°C and stirred to release sulfur dioxide. After the sulfur dioxide was volatilized, 22 kg of deionized water was added to the obtained reaction liquid. The mixture was heated to 85°C with stirring to quench the aluminum chloride. After the quenching reaction for 0.7 hour, the reaction liquid was cooled to 36°C and filtered to obtain 5.35 kg of 4,4'-dichlorodiphenyl sulfoxide with a yield of 98.7% and a liquid phase purity of 99.9%.

[0036] Example 5: At -14°C, 24.98 kg of thionyl chloride and 29.26 kg of aluminum chloride were added to 150 kg of sulfur dioxide solution, and the mixture was stirred and dissolved to obtain a mixed solution.

[0037] The obtained mixed liquid was pumped into a static mixer for circulation. At the same time, 22.5 kg of chlorobenzene 1 was pumped into the static mixer. After the reaction was kept at -13°C for 3 hours, 24.75 kg of chlorobenzene 2 was pumped into it. After the addition was completed, the temperature was lowered to -21°C and the reaction was continued for 3 hours. After the reaction was completed, the temperature was raised to 25°C and stirred to release sulfur dioxide. After the sulfur dioxide was completely volatilized, 150 kg of deionized water was added to the obtained reaction liquid. The mixture was heated to 90°C with stirring to quench the aluminum chloride. After the quenching reaction for 1 hour, the reaction liquid was cooled to 30°C and filtered to obtain 52.65 kg of 4,4'-dichlorodiphenyl sulfoxide with a yield of 98.5% and a liquid phase purity of 99.9%.

[0038] Comparative Example 1: At -15°C, 0.131 kg of thionyl chloride and 0.146 kg of aluminum chloride were added to 1 kg of dichloromethane, and the mixture was stirred and dissolved to obtain a mixed solution;

[0039] The obtained mixed liquid was pumped into a static mixer for circulation. At the same time, 0.112 kg of chlorobenzene 1 was pumped into the static mixer. After the reaction was kept at -10°C for 2 hours, 0.135 kg of chlorobenzene 2 was pumped into it. After the addition was completed, the temperature was lowered to -23°C and the reaction was continued for 2 hours. After the reaction was completed, the temperature was raised to 25°C, and 1 kg of deionized water was added to the obtained reaction liquid. The mixture was heated to 80°C with stirring to quench the aluminum chloride. After quenching the reaction for 0.5 hours, the reaction liquid was cooled to 30°C and filtered to obtain 0.246 kg of 4,4'-dichlorodiphenyl sulfoxide with a yield of 90.7% and a liquid phase purity of 89.5%.

[0040] Comparative Example 2 At -15°C, 0.131 kg of chlorobenzene and 0.146 kg of aluminum chloride were added to 1 kg of sulfur dioxide solution, and the mixture was stirred and dissolved to obtain a mixed solution;

[0041] The obtained mixed liquid was pumped into a static mixer for circulation. At the same time, 0.225 kg of chlorobenzene was pumped into the static mixer. After the reaction was kept at -10°C for 2 hours, the temperature was lowered to -23°C and the reaction was continued for 2 hours. After the reaction was completed, the temperature was raised to 25°C and stirred to release sulfur dioxide. After the sulfur dioxide was completely volatilized, 1 kg of deionized water was added to the obtained reaction liquid. The mixture was heated to 80°C with stirring to quench the aluminum chloride. After the quenching reaction for 0.5 hours, the reaction liquid was cooled to 30°C and filtered to obtain 0.248 kg of 4,4'-dichlorodiphenyl sulfoxide with a yield of 91.4% and a liquid phase purity of 88.6%.

[0042] Comparative Example 3: At -15°C, 0.131 kg of thionyl chloride and 0.133 kg of aluminum chloride were added to 1 kg of dichloromethane, and the mixture was stirred and dissolved to obtain a mixed solution;

[0043] The obtained mixed solution was pumped into a static mixer for circulation. At the same time, 0.236 kg of chlorobenzene was pumped into the static mixer. The mixture was kept at -10°C for reaction for 2 hours. After the addition was completed, the temperature was lowered to -23°C and the reaction was continued for 2 hours. After the reaction was completed, the temperature was raised to 25°C. 1 kg of deionized water was added to the obtained reaction solution. The mixture was heated to 80°C with stirring to quench the aluminum chloride. After quenching the reaction for 0.5 hours, the reaction solution was cooled to 30°C and filtered to obtain 0.204 kg of 4,4'-dichlorodiphenyl sulfoxide with a yield of 75.2% and a liquid phase purity of 75.3%.

[0044] Although the above describes the specific implementation methods of the present invention, it does not limit the scope of protection of the present invention. Based on the technical solution of the present invention, various modifications or variations that can be made by those skilled in the art without creative work are still within the scope of protection of the present invention.

Claims

1. A method for synthesizing 4,4'-dichlorodiphenyl sulfoxide, characterized in that: The following steps are involved: (a) adding thionyl chloride and aluminum chloride to a sulfur dioxide solution at -15 to -10°C, stirring and dissolving to obtain a mixed solution; (b) The mixed solution obtained in step (a) is pumped into a static mixer for circulation, and chlorobenzene 1 is pumped into the static mixer at the same time. After the reaction is carried out at -15 to -10°C for 2 to 4 hours, chlorobenzene 2 is pumped into the mixed solution. After the addition is completed, the temperature is lowered to -25 to -20°C and the reaction is continued for 2 to 4 hours. After the reaction is completed, the temperature is raised to 25 to 30°C and stirred to release sulfur dioxide. After the sulfur dioxide is completely volatilized, deionized water is added to the obtained reaction solution, and the solution is heated to 80 to 100°C with stirring to quench the aluminum chloride. After the quenching reaction is completed, the temperature is lowered to 30 to 40°C, and the solution is filtered to obtain 4,4'-dichlorodiphenyl sulfoxide.

2. The method for synthesizing 4,4'-dichlorodiphenyl sulfoxide according to claim 1, wherein: The mass ratio of the sulfur dioxide solution in step (a) to the chlorobenzene 1 in step (b) is 5-10:

1.

3. The method for synthesizing 4,4'-dichlorodiphenyl sulfoxide according to claim 1, wherein: The molar ratio of the aluminum chloride in step (a) to the chlorobenzene 1 in step (b) is 1-1.1:

1.

4. The method for synthesizing 4,4'-dichlorodiphenyl sulfoxide according to claim 1, wherein: The molar ratio of the chlorobenzene 1 in step (b) to the thionyl chloride in step (a) is 1:1-1.

1.

5. The method for synthesizing 4,4'-dichlorodiphenyl sulfoxide according to claim 1, wherein: The molar ratio of the chlorobenzene 2 in step (b) to the thionyl chloride in step (a) is 1-1.1:

1.

6. The method for synthesizing 4,4'-dichlorodiphenyl sulfoxide according to claim 1, wherein: The mass ratio of the deionized water added in step (b) to the aluminum chloride in step (a) is 5-10:

1.

7. The method for synthesizing 4,4'-dichlorodiphenyl sulfoxide according to claim 1, wherein: The aluminum chloride quenching reaction time in step (b) is 0.5 to 1 hour.

8. The method for synthesizing 4,4'-dichlorodiphenyl sulfoxide according to claim 1, wherein: The stirring in step (b) is heated to 80-90° C. to quench the aluminum chloride.

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