CN113173844A - Preparation method of 2-methyl-4-chlorophenoxyacetic acid - Google Patents
Preparation method of 2-methyl-4-chlorophenoxyacetic acid Download PDFInfo
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Abstract
The invention provides a preparation method of 2-methyl-4-chlorophenoxyacetic acid, which comprises the following steps: A) adding o-methylphenol and chloroacetic acid into a composite organic solvent, cooling the system to 10-20 ℃, adding solid alkali, and carrying out a salt forming reaction; B) after the salt forming reaction is finished, adding a trimethylamine hydrochloride catalyst, heating to 100-130 ℃, and carrying out condensation reaction; C) after the condensation reaction is finished, cooling to 25-35 ℃, adding sodium hypochlorite for hypochlorination reaction to generate 2-methyl-4-chlorophenoxy sodium acetate; D) and after the hypochlorination reaction is finished, controlling the temperature to be 50-80 ℃, and adding hydrochloric acid for acidification to obtain the 2-methyl-4-chlorophenoxyacetic acid. The invention adopts the composite organic solvent, slows down the hydrolysis of chloroacetic acid, promotes the reaction forward reaction, reduces the byproducts, and ensures that the yield reaches 94 percent and the content reaches 97 percent. Meanwhile, the product has good crystal form and high content.
Description
Technical Field
The invention belongs to the technical field of organic synthesis, and particularly relates to a preparation method of 2-methyl-4-chlorophenoxyacetic acid.
Background
2-methyl-4-chlorophenoxyacetic acid is a systemic conductive herbicide with wide application prospect. The method is mainly applied to two aspects: firstly, when the concentration of the plant growth regulator is low, the plant growth regulator can promote the plant growth; secondly, the herbicide destroys the metabolism of plants at high concentration so as to achieve the purpose of killing the plants. At present, the fertilizer is widely applied to crops such as corn, wheat field, fruit trees, vegetables and the like.
At present, the research on 2-methyl-4-chlorophenoxyacetic acid mainly focuses on the post-chlorination route, namely, o-cresol is firstly prepared into o-cresol sodium, the o-cresol sodium is condensed with sodium chloroacetate to produce 2-methyl phenoxyacetic acid, and then the o-cresol sodium is acidified and chlorine is introduced to produce the 2-methyl-4-chlorophenoxyacetic acid, wherein the reaction equation is as follows:
patent CN 110407685A discloses a preparation method of o-methylphenoxyacetic acid, which utilizes chloroacetic acid to dissolve in organic solvent, the organic solvent is aromatic hydrocarbon, preferably chlorobenzene. Dropwise adding o-cresol, heating to melt, wherein the molar ratio of chloroacetic acid to o-cresol is 1.2:1, then adding solid sodium hydroxide to salify and perform high-temperature condensation, wherein the condensation reaction temperature is 110-140 ℃, adding a proper amount of water while the solution is hot, and promoting the reaction to perform to prepare the o-tolyloxy acetic acid. The excessive chloroacetic acid is added with water in the heating condensation, and is hydrolyzed under the high temperature condition, so that the consumption of raw materials is high, the treatment pressure of three wastes is increased, the reaction is severe, the safety is poor, and the final product is o-methylphenoxyacetic acid which is an intermediate and can not be directly put into a preparation as a raw material.
Disclosure of Invention
The invention aims to provide a preparation method of 2-methyl-4-chlorophenoxyacetic acid, which has few byproducts and high yield and reduces the pressure of environmental protection on the treatment of phenolic wastewater.
The invention provides a preparation method of 2-methyl-4-chlorophenoxyacetic acid, which comprises the following steps:
A) adding o-methylphenol and chloroacetic acid into a composite organic solvent, cooling the system to 10-20 ℃, adding solid alkali, and carrying out a salt forming reaction;
the composite organic solvent comprises one or more of dichloroethane, cyclohexane, n-hexane, xylene, toluene, petroleum ether and acetone;
B) after the salt forming reaction is finished, adding a trimethylamine hydrochloride catalyst, heating to 100-130 ℃, and carrying out condensation reaction;
C) after the condensation reaction is finished, cooling to 25-35 ℃, adding sodium hypochlorite for hypochlorination reaction to generate 2-methyl-4-chlorophenoxy sodium acetate;
D) and after the hypochlorination reaction is finished, controlling the temperature to be 50-80 ℃, and adding hydrochloric acid for acidification to obtain the 2-methyl-4-chlorophenoxyacetic acid.
Preferably, the molar ratio of the o-methylphenol to the chloroacetic acid is (1.0-1.05): (0.85-0.95).
Preferably, the composite organic solvent is one of dichloroethane, cyclohexane, n-hexane, toluene, petroleum ether and acetone, and xylene in a mass ratio of 1: (1-1.5) in the presence of a solvent mixture.
Preferably, the molar ratio of the o-methyl phenol to the solid base is 1: (2.01-2.1).
Preferably, the time of the salt forming reaction is 1-3 hours.
Preferably, the molar ratio of the chloroacetic acid to the trimethylamine hydrochloride is 1 (0.01-0.1).
Preferably, the time of the condensation reaction is 2 to 4 hours.
Preferably, in the step D), 30% hydrochloric acid is dripped for acidification, and after the dripping of the hydrochloric acid is finished, the reaction is continued for 0.5-2 hours to obtain the 2-methyl-4-chlorophenoxyacetic acid.
Preferably, after the acidification reaction is finished, cooling crystallization is carried out, and when the temperature is reduced to 0-15 ℃, the 2-methyl-4-chlorophenoxyacetic acid product is obtained through suction filtration.
The invention provides a preparation method of 2-methyl-4-chlorophenoxyacetic acid, which comprises the following steps: A) adding o-methylphenol and chloroacetic acid into a composite organic solvent, cooling the system to 10-20 ℃, adding solid alkali, and carrying out a salt forming reaction; the composite organic solvent comprises one or more of dichloroethane, cyclohexane, n-hexane, xylene, toluene, petroleum ether and acetone; B) after the salt forming reaction is finished, adding a trimethylamine hydrochloride catalyst, heating to 100-130 ℃, and carrying out condensation reaction; C) after the condensation reaction is finished, cooling to 25-35 ℃, adding sodium hypochlorite for hypochlorination reaction to generate 2-methyl-4-chlorophenoxy sodium acetate; D) and after the hypochlorination reaction is finished, controlling the temperature to be 50-80 ℃, and adding hydrochloric acid for acidification to obtain the 2-methyl-4-chlorophenoxyacetic acid. The invention adopts the composite organic solvent, slows down the hydrolysis of chloroacetic acid, promotes the reaction forward reaction, reduces the byproducts, and ensures that the yield reaches 94 percent and the content reaches 97 percent. Meanwhile, the product has good crystal form and high content. Therefore, the technology is more suitable for industrial production. Low-temperature salification is carried out, the chloroacetic acid hydrolysis is reduced while the conversion rate is improved, and the generation of byproducts is reduced. The method is an anhydrous reaction, and reduces the pressure of environmental protection on the treatment of the phenolic wastewater.
Detailed Description
The invention provides a preparation method of 2-methyl-4-chlorophenoxyacetic acid, which comprises the following steps:
A) adding o-methylphenol and chloroacetic acid into a composite organic solvent, cooling the system to 10-20 ℃, adding solid alkali, and carrying out a salt forming reaction;
the composite organic solvent comprises one or more of dichloroethane, cyclohexane, n-hexane, xylene, toluene, petroleum ether and acetone;
B) after the salt forming reaction is finished, adding a trimethylamine hydrochloride catalyst, heating to 100-130 ℃, and carrying out condensation reaction;
C) after the condensation reaction is finished, cooling to 25-35 ℃, adding sodium hypochlorite for hypochlorination reaction to generate 2-methyl-4-chlorophenoxy sodium acetate;
D) and after the hypochlorination reaction is finished, controlling the temperature to be 50-80 ℃, and adding hydrochloric acid for acidification to obtain the 2-methyl-4-chlorophenoxyacetic acid.
In the invention, the reaction is carried out in a composite organic solvent, the composite organic solvent preferably comprises one or more of dichloroethane, cyclohexane, n-hexane, xylene, toluene, petroleum ether and acetone, and more preferably is a mixed solvent consisting of one of dichloroethane, cyclohexane, n-hexane, toluene, petroleum ether and acetone and xylene, such as xylene and cyclohexane, xylene and acetone, xylene and high-boiling petroleum ether; the mass ratio of one of dichloroethane, cyclohexane, n-hexane, toluene, petroleum ether and acetone to xylene is preferably 1: (1-1.5).
The composite organic solvent can control the reflux temperature to be 100-130 ℃, the solvent can not turn red due to other impurities or excessive raw materials when being recycled, the reaction is controlled at the reflux temperature, the operation and the realization are easy, and the reaction temperature is 100-130 ℃, so that the reaction system is stable and the product yield is high; the recovered organic solvent does not turn red, and the influence of soluble impurities in the solvent on the product quality is reduced and the product content is improved during product post-treatment. Meanwhile, the form of mixed organic solvent can reduce the solubility of the product in the solvent, and the prepared product is white fine needle-shaped crystal and simultaneously improves the product yield.
In the invention, molten o-cresol and solid chloroacetic acid are preferably added into a composite organic solvent, the temperature is reduced to 10-20 ℃ after the solid chloroacetic acid solvent is cooled, solid alkali such as solid sodium hydroxide is added in times, and salt forming reaction is carried out at low temperature.
The o-methylphenol, the chloroacetic acid and the solid sodium hydroxide are salified at the same time at low temperature, so that the cost can be saved, high-temperature condensation is carried out after the salification is completed, the reaction is carried out separately, the exothermic reaction is delayed, and the safety is improved.
In the invention, the molar ratio of the o-methylphenol to the chloroacetic acid is preferably (1.0-1.05): (0.85-0.95), preferably 1.03-0.9, and the method promotes the positive reaction in a mode of excessive o-methylphenol, and further slows down the chloroacetic acid hydrolysis. And excessive o-methyl phenol is dissolved in the loaded mixed solvent, and can be reused when being used for the second time, so that the o-methyl phenol: the chloroacetic acid molar ratio is 1.03:0.9, and the reaction can be carried out again.
In the present invention, the molar ratio of the o-methyl phenol to the solid base is 1: (2.01-2.1), preferably adding sodium hydroxide for 2-4 times. The method has short time of salt-forming reaction, and the time of the salt-forming reaction is preferably 1-3 hours, and more preferably 2-3 hours.
After the salt forming reaction is finished, adding a trimethylamine hydrochloride catalyst into the system, heating to 100-130 ℃ for condensation reaction. The reaction time is 2-4 h. Compared with other substances such as trimethylamine, the trimethylamine hydrochloride can improve the conversion rate of the condensation reaction, and the condensation reaction can be completed by more than 95%.
Trimethylamine hydrochloride is used as a PH buffering agent, the PH of the reaction can be adjusted and maintained in a weak alkali environment (PH 8-9), the reaction condensation reaction is favorably carried out, the condensation reaction time is shortened from 1-6h to 2-4h, and the production cost is saved. Meanwhile, after salification is finished, a trimethylamine hydrochloride catalyst is added to avoid direct contact with chloroacetic acid to react.
In the invention, the molar ratio of chloroacetic acid to trimethylamine hydrochloride is 1 (0.01-0.1), and more preferably 1: (0.03-0.08), most preferably 1: (0.05-0.06); the condensation reaction temperature is preferably 100 to 130 ℃, more preferably 110 to 120 ℃, such as 100 ℃, 105 ℃, 110 ℃, 115 ℃, 120 ℃, 125 ℃ and 130 ℃, preferably in a range with any of the above values as the upper limit or the lower limit. The time of the condensation reaction is preferably 2 to 4 hours.
After the condensation reaction is finished, cooling the system to 25-35 ℃, and dropwise adding sodium hypochlorite to perform a hypochlorination reaction to generate the 2-methyl-4-chlorophenoxy sodium acetate. After the dropwise addition of the sodium hypochlorite is finished, the reaction temperature is controlled to be 25-35 ℃, the reaction is continued for 3-7h, and the sodium hypochlorite is used as a hypochloride raw material, so that the production risk is reduced.
In the invention, the amount of the sodium hypochlorite is excessive relative to the amount of the 2-sodium methylphenoxyacetate, and the molar ratio of the sodium hypochlorite to the 2-sodium methylphenoxyacetate is preferably (1.5-2): 1. because no new impurities are introduced, and the sodium hyposulfite is weak base, the excessive sodium hyposulfite is more beneficial to the reaction.
And after the hypochlorination reaction is finished, controlling the reaction temperature to be 50-80 ℃, dropwise adding hydrochloric acid for acidification, and after the hydrochloric acid is dropwise added, continuing the reaction for 0.5-2h to obtain the 2-methyl-4-chlorophenoxyacetic acid. The redundant hydrochloric acid and the residual sodium hydroxide in the solvent are subjected to neutralization reaction, so that three wastes are reduced.
In the invention, the hydrochloric acid is preferably a hydrochloric acid solution with a mass fraction of 30%, and the molar ratio of the hydrochloric acid to the sodium 2-methyl-4-chlorophenoxyacetate is preferably (1.5-1.8): 1, more preferably (1.6 to 1.7): 1, acidifying the reaction by the hydrochloric acid, and neutralizing the acid-base property of the solvent.
And after the acidification reaction is finished, cooling and crystallizing, controlling the temperature to be reduced by 1-3 ℃ per minute, and performing suction filtration to obtain the product when the temperature is reduced to 0-15 ℃. Standing and layering the filtrate, separating the organic phase from the water phase, recycling the organic phase, and simply distilling the water phase for recycling.
The invention provides a preparation method of 2-methyl-4-chlorophenoxyacetic acid, which comprises the following steps: A) adding o-methylphenol and chloroacetic acid into a composite organic solvent, cooling the system to 10-20 ℃, adding solid alkali, and carrying out a salt forming reaction; the composite organic solvent comprises one or more of dichloroethane, cyclohexane, n-hexane, xylene, toluene, petroleum ether and acetone; B) after the salt forming reaction is finished, adding a trimethylamine hydrochloride catalyst, heating to 100-130 ℃, and carrying out condensation reaction; C) after the condensation reaction is finished, cooling to 25-35 ℃, adding sodium hypochlorite for hypochlorination reaction to generate 2-methyl-4-chlorophenoxy sodium acetate; D) and after the hypochlorination reaction is finished, controlling the temperature to be 50-80 ℃, and adding hydrochloric acid for acidification to obtain the 2-methyl-4-chlorophenoxyacetic acid. The invention adopts the composite organic solvent, slows down the hydrolysis of chloroacetic acid, promotes the reaction forward reaction, reduces the byproducts, and ensures that the yield reaches 94 percent and the content reaches 97 percent. Meanwhile, the product has good crystal form and high content. Therefore, the technology is more suitable for industrial production. Low-temperature salification is carried out, the chloroacetic acid hydrolysis is reduced while the conversion rate is improved, and the generation of byproducts is reduced. The method is an anhydrous reaction, and reduces the pressure of environmental protection on the treatment of the phenolic wastewater.
In order to further illustrate the present invention, the following examples are provided to describe the preparation method of 2-methyl-4-chlorophenoxyacetic acid of the present invention in detail, but should not be construed as limiting the scope of the present invention.
Example 1
Adding xylene: the preparation method comprises the following steps of adding 400g of a composite organic solvent with the ratio of cyclohexane to 1.5:1 into 1.03 mol of molten o-cresol and 0.9 mol of solid chloroacetic acid respectively, adding 2.05 mol of solid sodium hydroxide in portions when the solid chloroacetic acid is cooled to 10-20 ℃ after being dissolved, and carrying out salt-forming reaction at low temperature. After salification is finished, 6g of trimethylamine hydrochloride catalyst is added, and the temperature is raised to 115 ℃ for condensation reaction. After the condensation reaction is finished, when the temperature is reduced to 25-35 ℃, sodium hypochlorite (1.5-2.0 mol) is dripped to carry out hypochlorination reaction to generate the 2-methyl-4-chlorophenoxy sodium acetate. After the dropwise addition of the sodium hypochlorite is finished, controlling the reaction temperature to be 25-35 ℃, and continuing to react for 3-7 h. After the hypochlorination reaction is finished, 200g of 30% hydrochloric acid is dripped into the mixture for acidification when the reaction temperature is controlled to be between 50 and 80 ℃, and the reaction is continued for 0.5 to 2 hours after the dripping of the hydrochloric acid is finished to obtain the 2-methyl-4-chlorophenoxyacetic acid. And after the acidification reaction is finished, cooling and crystallizing, controlling the temperature to be reduced by 1-3 ℃ per minute, and performing suction filtration to obtain the product when the temperature is reduced to 0-15 ℃. The yield of the product is 95.5 percent, and the content is 97.4 percent.
Example 2
Adding xylene: 400g of composite organic solvent with the acetone ratio of 1:1, respectively adding 1.03 mol of molten o-cresol and 0.9 mol of solid chloroacetic acid, cooling to 10-20 ℃ after the solid chloroacetic acid is dissolved, adding 2.05 mol of solid sodium hydroxide in portions, and carrying out salt forming reaction at low temperature. After salification is finished, 6g of trimethylamine hydrochloride catalyst is added, and the temperature is raised to 100 ℃ for condensation reaction. After the condensation reaction is finished, when the temperature is reduced to 25-35 ℃, sodium hypochlorite (1.5-2.0 mol) is dripped to carry out hypochlorination reaction to generate the 2-methyl-4-chlorophenoxy sodium acetate. After the dropwise addition of the sodium hypochlorite is finished, controlling the reaction temperature to be 25-35 ℃, and continuing to react for 3-7 h. After the hypochlorination reaction is finished, 200g of 30% hydrochloric acid is dripped into the mixture for acidification when the reaction temperature is controlled to be between 50 and 80 ℃, and the reaction is continued for 0.5 to 2 hours after the dripping of the hydrochloric acid is finished to obtain the 2-methyl-4-chlorophenoxyacetic acid. And after the acidification reaction is finished, cooling and crystallizing, controlling the temperature to be reduced by 1-3 ℃ per minute, and performing suction filtration to obtain the product when the temperature is reduced to 0-15 ℃. The yield of the product is 90.5 percent, and the content is 89.6 percent.
Example 3
Adding xylene: 400g of a composite organic solvent with the high boiling point of 1:1, respectively adding 1.03 mol of fused o-cresol and 0.9 mol of solid chloroacetic acid, adding 2.05 mol of solid sodium hydroxide in portions when the solid chloroacetic acid is cooled to 10-20 ℃ after being dissolved, and carrying out salt forming reaction at low temperature. After salification is finished, 6g of trimethylamine hydrochloride catalyst is added, and the temperature is raised to 125 ℃ for condensation reaction. After the condensation reaction is finished, when the temperature is reduced to 25-35 ℃, sodium hypochlorite (1.5-2.0 mol) is dripped to carry out hypochlorination reaction to generate the 2-methyl-4-chlorophenoxy sodium acetate. After the dropwise addition of the sodium hypochlorite is finished, controlling the reaction temperature to be 25-35 ℃, and continuing to react for 3-7 h. After the hypochlorination reaction is finished, 200g of 30% hydrochloric acid is dripped into the mixture for acidification when the reaction temperature is controlled to be between 50 and 80 ℃, and the reaction is continued for 0.5 to 2 hours after the dripping of the hydrochloric acid is finished to obtain the 2-methyl-4-chlorophenoxyacetic acid. And after the acidification reaction is finished, cooling and crystallizing, controlling the temperature to be reduced by 1-3 ℃ per minute, and performing suction filtration to obtain the product when the temperature is reduced to 0-15 ℃. The yield of the product is 93.5 percent, and the content is 97.8 percent.
Example 4
Adding xylene: the preparation method comprises the following steps of adding 400g of a composite organic solvent with the ratio of cyclohexane to 1, adding 1.03 mol of molten o-cresol and 0.9 mol of solid chloroacetic acid, cooling to 10-20 ℃ after the solid chloroacetic acid is dissolved, adding 2.05 mol of solid sodium hydroxide in portions, and carrying out salt forming reaction at low temperature. After salification is finished, 6g of trimethylamine hydrochloride catalyst is added, and the temperature is raised to 100-130 ℃ for condensation reaction. After the condensation reaction is finished, cooling to 25-35 ℃, and then dropwise adding 1.7 mol of sodium hypochlorite to carry out hypochlorination reaction to generate the 2-methyl-4-chlorophenoxy sodium acetate. After the dropwise addition of the sodium hypochlorite is finished, controlling the reaction temperature to be 25-35 ℃, and continuing to react for 3-7 h. After the hypochlorination reaction is finished, 200g of 30% hydrochloric acid is dripped into the mixture for acidification when the reaction temperature is controlled to be between 50 and 80 ℃, and the reaction is continued for 0.5 to 2 hours after the dripping of the hydrochloric acid is finished to obtain the 2-methyl-4-chlorophenoxyacetic acid. And after the acidification reaction is finished, cooling and crystallizing, controlling the temperature to be reduced by 1-3 ℃ per minute, and performing suction filtration to obtain the product when the temperature is reduced to 0-15 ℃. The yield of the product is 94.4%, and the content is 97.6%.
Example 5
Adding xylene: the preparation method comprises the following steps of adding 400g of a composite organic solvent with the ratio of cyclohexane to 1, adding 1.03 mol of molten o-cresol and 0.9 mol of solid chloroacetic acid, cooling to 10-20 ℃ after the solid chloroacetic acid is dissolved, adding 2.05 mol of solid sodium hydroxide in portions, and carrying out salt forming reaction at low temperature. After salification is finished, 6g of trimethylamine hydrochloride catalyst is added, and the temperature is raised to 100-130 ℃ for condensation reaction. After the condensation reaction is finished, cooling to 25-35 ℃, and then dropwise adding 2.0 mol of sodium hypochlorite to carry out hypochlorination reaction to generate 2-methyl-4-chlorophenoxy sodium acetate. After the dropwise addition of the sodium hypochlorite is finished, controlling the reaction temperature to be 25-35 ℃, and continuing to react for 3-7 h. After the hypochlorination reaction is finished, 200g of 30% hydrochloric acid is dripped into the mixture for acidification when the reaction temperature is controlled to be between 50 and 80 ℃, and the reaction is continued for 0.5 to 2 hours after the dripping of the hydrochloric acid is finished to obtain the 2-methyl-4-chlorophenoxyacetic acid. And after the acidification reaction is finished, cooling and crystallizing, controlling the temperature to be reduced by 1-3 ℃ per minute, and performing suction filtration to obtain the product when the temperature is reduced to 0-15 ℃. The yield of the product is 95.6 percent, and the content is 98.1 percent.
Comparative example 1
2-methyl-4-chlorophenoxyacetic acid was prepared according to the procedure in example 1. Except that the charge of the solid caustic soda sodium hydroxide in comparative example 1 was at moles.
The yield of the product is 89.5 percent, and the content is 90.4 percent.
The comparative example 1 changes the feeding amount of the solid caustic soda under the condition of no change of other conditions, obviously reduces the yield and the content, and the experimental result shows that the salt forming process is carried out under the condition that the alkali is 2.01-2.1 mol and is properly excessive.
Comparative example 2
2-methyl-4-chlorophenoxyacetic acid was prepared according to the procedure in example 1. Except that the catalyst in comparative example 2 was an aqueous trimethylamine solution.
The yield of the product is 87.6 percent, and the content is 93.4 percent.
In the comparative example 2, the type of the catalyst is changed under the condition that other conditions are not changed, the yield and the content are obviously reduced, and the experimental result shows that compared with the trimethylamine aqueous solution catalyst, the trimethylamine hydrochloride has better catalytic effect.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (9)
1. A preparation method of 2-methyl-4-chlorophenoxyacetic acid comprises the following steps:
A) adding o-methylphenol and chloroacetic acid into a composite organic solvent, cooling the system to 10-20 ℃, adding solid alkali, and carrying out a salt forming reaction;
the composite organic solvent comprises one or more of dichloroethane, cyclohexane, n-hexane, xylene, toluene, petroleum ether and acetone;
B) after the salt forming reaction is finished, adding a trimethylamine hydrochloride catalyst, heating to 100-130 ℃, and carrying out condensation reaction;
C) after the condensation reaction is finished, cooling to 25-35 ℃, adding sodium hypochlorite for hypochlorination reaction to generate 2-methyl-4-chlorophenoxy sodium acetate;
D) and after the hypochlorination reaction is finished, controlling the temperature to be 50-80 ℃, and adding hydrochloric acid for acidification to obtain the 2-methyl-4-chlorophenoxyacetic acid.
2. The preparation method according to claim 1, wherein the molar ratio of o-methylphenol to chloroacetic acid is (1.0-1.05): (0.85-0.95).
3. The preparation method according to claim 1, wherein the composite organic solvent is one of dichloroethane, cyclohexane, n-hexane, toluene, petroleum ether and acetone, and xylene in a mass ratio of 1: (1-1.5) in the presence of a solvent mixture.
4. The method according to claim 1, wherein the molar ratio of the o-methylphenol to the solid base is 1: (2.01-2.1).
5. The preparation method according to claim 1, wherein the time of the salt forming reaction is 1 to 3 hours.
6. The preparation method according to claim 1, wherein the molar ratio of chloroacetic acid to trimethylamine hydrochloride is 1 (0.01-0.1).
7. The method according to claim 1, wherein the condensation reaction is carried out for 2 to 4 hours.
8. The preparation method of claim 1, wherein in the step D), 30% hydrochloric acid is added dropwise for acidification, and after the hydrochloric acid is added dropwise, the reaction is continued for 0.5-2 hours to obtain 2-methyl-4-chlorophenoxyacetic acid.
9. The preparation method of claim 1, wherein after the acidification reaction is finished, cooling crystallization is carried out, and when the temperature is reduced to 0-15 ℃, a 2-methyl-4-chlorophenoxyacetic acid product is obtained by suction filtration.
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| CN114685264A (en) * | 2022-05-06 | 2022-07-01 | 山东潍坊润丰化工股份有限公司 | Preparation method of high-quality 2-methyl-4-chlorophenoxyacetic acid |
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