A kind of preparation method of 3-methoxy-2-methylbenzoic acid

Abstract

The present invention relates to the technical field of ester hydrolysis, and provides a preparation method of 3-methoxy-2-methylbenzoic acid. The present invention mixes 3-methoxy-2-methylbenzoic acid methyl ester and acid solution for hydrolysis to obtain 3-methoxy-2-methylbenzoic acid. The present invention uses acid solution as a catalyst to hydrolyze 3-methoxy-2-methylbenzoic acid methyl ester into 3-methoxy-2-methylbenzoic acid, and the reaction process is gentle, the equipment requirements are not high, and high-salt wastewater will not be produced, and there is no need to increase environmental protection equipment. At the same time, the yield of 3-methoxy-2-methylbenzoic acid in the method is high and the purity is high. According to the data of the embodiment, 3-methoxy-2-methylbenzoic acid is prepared by the method of the present invention, and the product yield is as high as 87.14%, and the purity is as high as 99.34%.

Description

Technical Field

[0001] The invention relates to the technical field of ester hydrolysis, and in particular to a method for preparing 3-methoxy-2-methylbenzoic acid. Background Art

[0002] 3-methoxy-2-methylbenzoic acid is an important raw material for preparing the pesticide methoxyfenozide. At present, 3-methoxy-2-methylbenzoic acid is mainly obtained by acidifying after hydrolysis of 3-methoxy-2-methylbenzoic acid methyl ester under alkaline conditions. For example, the patent of publication number CN113105323A adopts 3-methoxy-2-methylbenzoic acid methyl ester to prepare 3-methoxy-2-methylbenzoic acid. The patent adopts first 3-methoxy-2-methylbenzoic acid methyl ester and alkali reaction to obtain 3-methoxy-2-methyl benzoate, then 3-methoxy-2-methyl benzoate and acid reaction, finally obtain 3-methoxy-2-methylbenzoic acid, but the process of 3-methoxy-2-methyl benzoate and acid reaction can produce a large amount of heat, high requirements for equipment, and a large amount of high-salinity wastewater is produced simultaneously, and it is necessary to increase environmental protection equipment, which causes the production cost to increase, which is unfavorable for industrial production. Summary of the invention

[0003] In view of the above problems, the object of the present invention is to provide a method for preparing 3-methoxy-2-methylbenzoic acid. The preparation method provided by the present invention uses an acid solution as a catalyst to directly hydrolyze 3-methoxy-2-methylbenzoic acid methyl ester into 3-methoxy-2-methylbenzoic acid. The process is simple, and the yield of the hydrolysis product is high. The obtained 3-methoxy-2-methylbenzoic acid has high purity.

[0004] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0005] The present invention provides a method for preparing 3-methoxy-2-methylbenzoic acid, comprising the following steps:

[0006] Methyl 3-methoxy-2-methylbenzoate and an acid solution are mixed and hydrolyzed to obtain 3-methoxy-2-methylbenzoic acid.

[0007] Preferably, the acid solution is one or more of a sulfuric acid solution, a hydrochloric acid solution and an acetic acid solution.

[0008] Preferably, the mass fraction of sulfuric acid in the sulfuric acid solution is 30-50%; the mass fraction of hydrochloric acid in the hydrochloric acid solution is 30-36%; and the mass fraction of acetic acid in the acetic acid solution is 20-50%.

[0009] Preferably, the mixing temperature is 30-50°C.

[0010] Preferably, the acid solution is a sulfuric acid solution and an acetic acid solution, and the mass ratio of the sulfuric acid solution to the acetic acid solution is 2:0.5-2.

[0011] Preferably, the acid solution is a sulfuric acid solution and a hydrochloric acid solution, and the mass ratio of the sulfuric acid solution to the hydrochloric acid solution is 2 to 0.5:1.

[0012] Preferably, the acid solution is a hydrochloric acid solution and an acetic acid solution, and the mass ratio of the hydrochloric acid solution to the acetic acid solution is 2 to 0.5:1.

[0013] Preferably, the mass ratio of the methyl 3-methoxy-2-methylbenzoate to the acid solution is 100:10-20.

[0014] Preferably, the hydrolysis temperature is 80-85°C.

[0015] Preferably, after the hydrolysis is completed, the method further comprises mixing the obtained reaction solution and an organic solvent and then standing to separate the layers, collecting an organic phase, washing the organic phase with water, and mixing the washed organic phase with an acid solution for secondary hydrolysis.

[0016] The invention provides a method for preparing 3-methoxy-2-methylbenzoic acid, comprising the following steps: mixing 3-methoxy-2-methylbenzoic acid methyl ester and an acid solution for hydrolysis to obtain 3-methoxy-2-methylbenzoic acid. The invention adopts an acid solution as a catalyst to directly hydrolyze 3-methoxy-2-methylbenzoic acid methyl ester into 3-methoxy-2-methylbenzoic acid, the reaction process is gentle, the equipment requirements are not high, and high-salt wastewater will not be generated, and there is no need to increase environmental protection equipment. At the same time, the yield of 3-methoxy-2-methylbenzoic acid in the method is high, and the obtained 3-methoxy-2-methylbenzoic acid has high purity. According to the data of the embodiment, 3-methoxy-2-methylbenzoic acid is prepared by the method provided by the invention, and the product yield is as high as 87.14%, and the purity is as high as 99.34%. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The present invention provides a synthetic route diagram of 3-methoxy-2-methylbenzoic acid. DETAILED DESCRIPTION

[0018] The present invention provides a method for preparing 3-methoxy-2-methylbenzoic acid, comprising the following steps:

[0019] Methyl 3-methoxy-2-methylbenzoate and an acid solution (referred to as the first acid solution) are mixed and hydrolyzed to obtain 3-methoxy-2-methylbenzoic acid.

[0020] In the present invention, unless otherwise specified, all substances are commercially available products well known to those skilled in the art.

[0021] In the present invention, the first acid solution is preferably one or more of a sulfuric acid solution, a hydrochloric acid solution and an acetic acid solution; the mass fraction of sulfuric acid in the sulfuric acid solution is preferably 30-50%, more preferably 30-40%; the mass fraction of hydrochloric acid in the hydrochloric acid solution is preferably 30-36%, more preferably 30%; the mass fraction of acetic acid in the acetic acid solution is preferably 20-50%, more preferably 20-30%; when the first acid solution is a sulfuric acid solution and an acetic acid solution, the mass ratio of the sulfuric acid solution to the acetic acid solution is preferably 2:0.5-2, more preferably 2:0.5-1; when the first acid solution is a sulfuric acid solution and a hydrochloric acid solution, the mass ratio of the sulfuric acid solution to the hydrochloric acid solution is preferably 2-0.5:1, more preferably 2:1; when the first acid solution is a hydrochloric acid solution and an acetic acid solution, the hydrochloric acid solution is preferably 2:0.5:1, more preferably 2:1; The mass ratio of the solution to the acetic acid solution is preferably 2-0.5:1, more preferably 2:1; in a specific embodiment of the present invention, when the first acid solution is a sulfuric acid solution and an acetic acid solution, the mass fraction of the sulfuric acid solution is preferably 30%, the mass fraction of the acetic acid solution is preferably 20%, and the mass ratio of the sulfuric acid solution to the hydrochloric acid solution is preferably 2:1; when the first acid solution is a hydrochloric acid solution and an acetic acid solution, the mass fraction of the hydrochloric acid solution is preferably 30%, the mass fraction of the acetic acid solution is preferably 30%, and the mass ratio of the hydrochloric acid solution to the acetic acid solution is preferably 2:1; when the first acid solution is a sulfuric acid solution and a hydrochloric acid solution, the mass fraction of the sulfuric acid solution is preferably 40%, the mass fraction of the hydrochloric acid solution is preferably 30%, and the mass ratio of the sulfuric acid solution to the hydrochloric acid solution is preferably 2:1.

[0022] In the present invention, the mixing temperature is preferably 30-50°C, more preferably 50°C; the mixing method is preferably heating methyl 3-methoxy-2-methylbenzoate to the mixing temperature, and then dropping the first acid solution into methyl 3-methoxy-2-methylbenzoate; the dropping rate is preferably 0.1-0.5 g / min; the mass ratio of methyl 3-methoxy-2-methylbenzoate to the first acid solution is preferably 100:10-20.

[0023] In the present invention, the temperature of the hydrolysis is preferably 80-85°C; the reaction time of the hydrolysis is preferably 7-13h. In a specific embodiment of the present invention, the reaction progress is preferably monitored by gas chromatography, and the reaction is considered to be complete when the raw material conversion rate no longer increases. In a specific embodiment of the present invention, the first gas chromatography analysis is preferably performed after the reaction is carried out for 5-7h to obtain the raw material conversion rate, and then the reaction is continued for 1-3h, and the gas chromatography analysis is performed again. If the raw material conversion rate increases, the reaction is continued for 1-3, until the result of the next gas chromatography analysis shows that the raw material conversion rate no longer increases compared with the previous one, and the reaction is considered to be complete. The reaction formula of the hydrolysis is as follows: Figure 1 shown.

[0024] In the present invention, after the hydrolysis (referred to as primary hydrolysis) is completed, the present invention preferably purifies the obtained hydrolyzate liquid; the purification is preferably: mixing the obtained hydrolyzate liquid and an organic solvent for static stratification, collecting the organic phase, washing the organic phase with water, and then rotary evaporating the washed organic phase to obtain 3-methoxy-2-methylbenzoic acid; the organic solvent is preferably one or more of toluene, dichloroethane and xylene, more preferably one or two of toluene and dichloromethane, and further preferably toluene; the stratification is preferably performed using a separatory funnel.

[0025] In the present invention, after the hydrolysis (referred to as the first hydrolysis) is completed, it is preferably further included that the obtained reaction solution and the organic solvent are mixed and then allowed to stand for stratification, the organic phase is collected, the organic phase is washed with water, and the washed organic phase is mixed with an acid solution (referred to as the second acid solution) for secondary hydrolysis; in the present invention, the organic solvent is preferably one or more of toluene, dichloroethane and xylene, more preferably one or two of toluene and dichloromethane, and further preferably toluene; the stratification is preferably carried out using a separatory funnel; the second acid solution is preferably one or more of sulfuric acid solution, acetic acid solution and hydrochloric acid solution; the mass ratio of the methyl 3-methoxy-2-methylbenzoate and the second acid solution is preferably 100:8-10; the temperature of the second hydrolysis is preferably 80-85°C, and the time is preferably 6-8h; in a specific embodiment of the present invention, preferably when the raw material conversion rate of the first hydrolysis is lower than 50%, the obtained reaction solution is subjected to secondary hydrolysis, and the raw material conversion rate after the second hydrolysis is completed can reach more than 80%; if the yield of the first hydrolysis is higher, there is no need to carry out secondary hydrolysis.

[0026] In the present invention, the method for judging whether the secondary hydrolysis is completed is consistent with the above-mentioned scheme and will not be described in detail here. After the secondary hydrolysis is completed, the obtained secondary hydrolysis product liquid is preferably subjected to static stratification, the organic phase is collected, the obtained organic phase is washed with water, and the organic phase after washing is subjected to rotary evaporation to remove the organic solvent to obtain 3-methoxy-2-methylbenzoic acid; the stratification is preferably performed using a separatory funnel.

[0027] In order to further illustrate the present invention, a method for preparing 3-methoxy-2-methylbenzoic acid provided by the present invention is described in detail below in conjunction with examples, but they should not be construed as limiting the scope of protection of the present invention.

[0028] Example 1

[0029] Weigh 100g of methyl 3-methoxy-2-methylbenzoate into a reaction bottle, heat it to 50°C with an oil bath, add 10g of a 30% sulfuric acid solution by mass, and after the addition is complete, continue to heat up to 85°C for hydrolysis reaction. After 5h of reaction, GC analysis shows that the raw material conversion rate is 50%. After continuing the reaction for 2h, GC analysis shows that the raw material conversion rate increases from 50% to 51.2%. After another 3h of reaction, GC analysis shows that the raw material conversion rate no longer increases, so the reaction is stopped. After the obtained reaction solution is naturally cooled to room temperature, an organic solvent, ethylene dichloride, is added to the obtained reaction solution, and the organic phase is collected. The obtained organic phase is washed with water, and the organic phase after washing is subjected to rotary evaporation to remove the organic solvent, and finally 43.6g of 3-methoxy-2-methylbenzoic acid is obtained with a purity of 98.6% and a yield of 48.35%.

[0030] Example 2

[0031] Weigh 100g of methyl 3-methoxy-2-methylbenzoate into a reaction bottle, heat it to 50°C with an oil bath, and drop 15g of 50% acetic acid solution. After the dropwise addition, continue to heat to 85°C for hydrolysis reaction. After 7h of reaction, GC analysis shows that the raw material conversion rate is 18%. After continuing the reaction for 3h, GC analysis shows that the raw material conversion rate increases from 18% to 26%. After another 3h of reaction, GC analysis shows that the raw material conversion rate no longer increases, and the reaction is stopped. After the obtained reaction solution is naturally cooled to room temperature, an organic solvent, ethylene dichloride, is added to the obtained reaction solution and allowed to stand for stratification. Collect the organic phase, wash the obtained organic phase with water, add 8g of mixed acid consisting of 33% sulfuric acid solution and 20% acetic acid solution by mass to the washed organic phase for secondary hydrolysis, the temperature is 80°C, the reaction is carried out for 6.5h, GC analysis shows that the raw material conversion rate is 94.3%, stop the reaction, let the obtained reaction solution stand and stratify, collect the organic phase, wash the obtained organic phase with water, and remove the organic solvent by rotary evaporation of the washed organic phase, and finally obtain 74.2g of 3-methoxy-2-methylbenzoic acid with a purity of 98.7% and a yield of 81.54%.

[0032] Example 3

[0033] Weigh 100g of methyl 3-methoxy-2-methylbenzoate into a reaction bottle, heat it to 50°C with an oil bath, and drop 15g of a mixed acid consisting of a 30% sulfuric acid solution and a 20% acetic acid solution, wherein the mass ratio of the 30% sulfuric acid solution to the 20% acetic acid solution is 2:1. After the dropwise addition, continue to heat to 80°C for hydrolysis reaction. After 6h of reaction, GC analysis shows that the raw material conversion rate is 93%. After continuing the reaction for 1h, GC analysis shows that the raw material conversion rate increases from 93% to 95%. After another 3h of reaction, GC analysis shows that the raw material conversion rate no longer increases, and the reaction is stopped. After the obtained reaction solution is naturally cooled to room temperature, toluene is added to the obtained reaction solution, and the mixture is allowed to stand for stratification. The organic phase is collected, and the obtained organic phase is washed with water. The organic phase after washing is subjected to rotary evaporation to remove the organic solvent, and finally 81.6g of 3-methoxy-2-methylbenzoic acid is obtained with a purity of 99.2% and a yield of 88.7%.

[0034] Example 4

[0035] Weigh 100g of methyl 3-methoxy-2-methylbenzoate into a reaction bottle, heat it to 50°C with an oil bath, and drop 15g of a mixed acid consisting of a 30% sulfuric acid solution and a 20% acetic acid solution, wherein the mass ratio of the 30% sulfuric acid solution to the 20% acetic acid solution is 2:0.5. After the dropwise addition, continue to heat to 80°C for hydrolysis reaction. After 6h of reaction, GC analysis shows that the raw material conversion rate is 94%. After continuing the reaction for 1h, GC analysis shows that the raw material conversion rate no longer increases, and the reaction is stopped. After the obtained reaction solution is naturally cooled to room temperature, toluene is added to the obtained reaction solution, and the mixture is allowed to stand for stratification. The organic phase is collected, and the obtained organic phase is washed with water. The organic phase after washing is subjected to rotary evaporation to remove the organic solvent, and finally 79.3g of 3-methoxy-2-methylbenzoic acid is obtained with a purity of 99.15% and a yield of 87.14%.

[0036] Example 5

[0037] Weigh 100g of methyl 3-methoxy-2-methylbenzoate into a reaction bottle, heat it to 50°C with an oil bath, and drop 15g of a 30% hydrochloric acid solution. After the addition is complete, continue to heat to 80°C for hydrolysis reaction. After 6h of reaction, GC analysis shows that the raw material conversion rate is 35%. After continuing the reaction for 1h, GC analysis shows that the raw material conversion rate increases from 35% to 39.5%. After continuing the reaction for 1h, GC analysis shows that the raw material conversion rate no longer increases, and the reaction is stopped. After the resulting reaction solution is naturally cooled to room temperature, the resulting reaction solution is added to the resulting solution. Toluene was added, the mixture was allowed to stand and the stratification was carried out. The organic phase was collected and washed with water. 10 g of 30% hydrochloric acid solution was added to the washed organic phase for secondary hydrolysis at 80°C for 6.5 h. According to GC analysis, the raw material conversion was 82.3%. The reaction solution was allowed to stand and the stratification was carried out. The organic phase was collected and washed with water. The organic phase was evaporated to remove the organic solvent, and finally 72.5 g of 3-methoxy-2-methylbenzoic acid was obtained with a purity of 98.6% and a yield of 80.3%.

[0038] Example 6

[0039] Weigh 100g of methyl 3-methoxy-2-methylbenzoate into a reaction bottle, heat it to 30°C with an oil bath, and drop 20g of a mixed acid consisting of a 30% hydrochloric acid solution and a 30% acetic acid solution, wherein the mass ratio of the 30% hydrochloric acid solution to the 30% acetic acid solution is 2:1. After the dropwise addition, continue to heat to 80°C for hydrolysis reaction. After 6h of reaction, GC analysis shows that the raw material conversion rate is 35%. After continuing the reaction for 3h, GC analysis shows that the raw material conversion rate no longer increases, stop the reaction, add toluene to the reaction solution, let stand and stratify, collect the organic phase, wash the obtained organic phase with water, and rotary evaporate the organic phase after washing to remove the organic solvent, and finally obtain 38.2g of 3-methoxy-2-methylbenzoic acid with a purity of 98.54% and a yield of 41.98%.

[0040] Example 7

[0041] Weigh 100g of methyl 3-methoxy-2-methylbenzoate into a reaction bottle, heat it to 30°C with an oil bath, and drop 15g of a mixed acid consisting of a 40% sulfuric acid solution and a 30% hydrochloric acid solution, wherein the mass ratio of the 40% sulfuric acid solution to the 30% hydrochloric acid solution is 2:1. After the dropwise addition, continue to heat to 80°C for hydrolysis reaction. After 6h of reaction, GC analysis shows that the raw material conversion rate is 23%. After continuing the reaction for 3h, GC analysis shows that the raw material conversion rate no longer increases, stop the reaction, and add methyl Benzene, stand and separate, collect the organic phase, wash the obtained organic phase with water, add 10g of mixed acid consisting of 33% sulfuric acid solution and 20% acetic acid solution by mass to the washed organic phase for secondary hydrolysis, temperature 85°C, reaction 6h, GC analysis, raw material conversion is 93.7%, the obtained reaction solution is stood and separated, collect the organic phase, wash the obtained organic phase with water, and remove the organic solvent by rotary evaporation of the washed organic phase, finally obtain 75g 3-methoxy-2-methylbenzoic acid, purity is 99.34%, yield is 82.42%.

[0042] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing 3-methoxy-2-methylbenzoic acid, characterized in that: The specific steps are: Weigh 100g of methyl 3-methoxy-2-methylbenzoate into a reaction bottle, heat it to 50°C with an oil bath, and drop 15g of a mixed acid consisting of a 30% sulfuric acid solution and a 20% acetic acid solution, wherein the mass ratio of the 30% sulfuric acid solution to the 20% acetic acid solution is 2:

1. After the dropwise addition, continue to heat to 80°C for hydrolysis reaction. After 6h of reaction, GC analysis shows that the raw material conversion rate is 93%. After continuing the reaction for 1h, GC analysis shows that the raw material conversion rate increases from 93% to 95%. After another 3h of reaction, GC analysis shows that the raw material conversion rate no longer increases, and the reaction is stopped. After the obtained reaction solution is naturally cooled to room temperature, toluene is added to the obtained reaction solution, and the mixture is allowed to stand for stratification. The organic phase is collected, and the obtained organic phase is washed with water. The organic phase after washing is subjected to rotary evaporation to remove the organic solvent, and finally 81.6g of 3-methoxy-2-methylbenzoic acid is obtained with a purity of 99.2% and a yield of 88.7%.

Images