Method for preparing 2,4-dichlorophenoxyacetic acid

Abstract

The invention discloses a method for preparing 2,4-dichlorophenoxyacetic acid. The method comprises the following specific steps of adding chloroacetic acid into a sodium hydroxide solution, stirring, adding phenol and adjusting the pH to 11 with sodium bicarbonate; heating for 40 minutes at 100 DEG C; adding hydrochloric acid to adjust the pH value to 4; finally cooling in an ice-water bath to obtain a solid, washing the obtained solid and drying to obtain phenoxy acetic acid; adding the phenoxy acetic acid into a mixed solution of acetic acid and water, adding iron phthalocyanine and stirring; introducing chlorine to carry out chlorination reaction; reacting for 35-50 minutes until the chlorination reaction is completed to obtain a reaction product; cooling the reaction product and filtering to obtain a solid substance; and finally cooling the solid substance to obtain the finished product 2,4-dichlorophenoxyacetic acid, wherein the molar amount of iron phthalocyanine is 0.1% of phenoxy acetic acid. By the method, the product has the advantages of high quality, high yield and high purity; the preparation process is simple and stable, low in industrial cost and environmental friendly.

Description

technical field [0001] The invention belongs to the field of organic synthesis, and in particular relates to a preparation method of 2,4-dichlorophenoxyacetic acid. Background technique [0002] 2,4-Dichlorophenoxyacetic acid (2,4-D) is a plant growth regulator widely used at present. It is an effective herbicide and preservative. It has the functions of preventing lodging, promoting rice production and early maturity , can also be used as an antifungal agent. After 1945, many countries put it into production and application. [0003] Phenol is first chlorinated by chlorine gas to produce 2,4-dichlorophenol, and then etherified and acidified with sodium chloroacetate under alkaline conditions to prepare 2,4-D; phenol and chloroacetic acid can be quickly Etherification, acidification, phenoxyacetic acid, and then chlorination in the aqueous phase can also synthesize 2,4-D. [0004] However, the chlorination end point of phenol is difficult to control. Dichlorophenol contai...

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Problems solved by technology

[0005] The existing synthetic route has a complex technological process, and the products contain impurities such as 2,6-dichlorophenoxyacetic acid, trichlorophenoxyacetic acid, and intermediate monochlorophenoxyacetic acid; the existence of these impurities directly affects the quality and yield. Rate

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