Preparation method for p-hydroxybenzoic acid

Abstract

The invention relates to a preparation method for p-hydroxybenzoic acid. The preparation method comprises successively adding pyrazole, 4-aminobenzotrifluoride and potassium hydroxide into dimethyl sulphoxide, dissolving, heating and refluxing for 1 h, cooling, adding water into the refluxing liquid for dissolving, adding dichloromethane, separating the liquid, extracting for three times, drying the organic phase with anhydrous magnesium sulfate, and performing column chromatography separation for obtaining 4-(tri(pyrazol-1-yl)methyl)aniline; and dropwise adding concentrated sulfuric acid into a mixed solution of 4-(tri(pyrazol-1-yl)methyl)aniline and water, dropwise adding a sodium nitrite aqueous solution under an ice bath condition with stirring, dropwise adding a sulfuric acid solution with the concentration of 15.5%, heating to 30-100 DEG C, reacting for 15 min to 2 h, naturally cooling, adding ethyl acetate and performing liquid-separation extraction for three times, performing reduced-pressure rotary evaporation, drying the organic phase with anhydrous sodium sulfate, and performing vacuum drying, so as to obtain p-hydroxybenzoic acid. The reaction synthetic route is short, reaction time is short, yield is high, and postprocessing is simple. The yield of 4-(tri(pyrazol-1-yl)methyl)aniline is about 80%, and the yield of p-hydroxybenzoic acid is about 99%.

Description

technical field [0001] The invention belongs to the field of chemical synthesis, and in particular relates to a preparation method of p-hydroxybenzoic acid. Background technique [0002] p-Hydroxybenzoic acid is a very versatile raw material for organic synthesis. It is used as an intermediate for the preparation of dyes and pesticides. . Ester derivatives of p-hydroxybenzoic acid such as methyl, ethyl, propyl, butyl, isopropyl, and isobutyl p-hydroxybenzoate are widely used as food additives in soy sauce, vinegar, and refreshing drinks (except soft drinks) ), fruit flavorings, fruits and vegetables, pickled products, etc. It can also be used as preservatives, fungicides, and insecticides. [0003] There are many ways to produce p-hydroxybenzoic acid, chemical methods such as potassium phenate carboxylation, or potassium salicylate heating, or diazotization and Sandmeyer reaction from p-aminophenol. The process must be carried out under high temperature and high pressure,...

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Problems solved by technology

[0003] There are many ways to produce p-hydroxybenzoic acid, chemical methods such as potassium phenate carboxylation, or potassium salicylate heating, or diazotization and Sandmeyer reaction from p-aminophenol. The process must be carried out under high temperature and high pressure, which requires a large amount of energy consumption, resulting in high production efficiency and low cost, especially the generation of environmental pollutant phenol in the synthesis route, which brings great difficulties to the treatment of industrial wastewater

The biosynthesis method uses plants or bacteria to synthesize, the reaction time is long, and the yield is low

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