How to obtain purified 3,4-dihydroxybenzoic acid?

3,4-dihydroxybenzoic acid is a phenolic acid and a metabolite of polyphenols. It is widely used in medicine, cosmetics, dyes, chemical industry and other industries, mainly used as pharmaceutical intermediates, dyes, analytical reagents and so on.

There are many ways to prepare 3,4-dihydroxybenzoic acid, such as extraction from the leaves of syringa, which is divided into raw material pretreatment and extraction. Syringa are dried, seeds and other impurities are removed after selection, and the remaining parts are crushed to obtain fine powder.

The fine powder was crushed to 70 mesh sieve, and 2 grams were taken as raw material. Under certain technological conditions, anhydrous ethanol was used as the extraction agent to get the extraction solution. After filtration, the extraction solution was removed and ethanol was recovered to get 3,4-dihydroxybenzoic acid.

Several other operations are needed to obtain the fine 3,4-dihydroxybenzoic acid. Add 50ml ethanol and 3ml 0.1mol/L hydrochloric acid to crude protocatechuic acid, gently shake to dissolve, and then put it into a clean separating funnel, extract with 0.1mol/L sodium hydroxide solution, repeat the operation for 3 times, extract 50mL each time, at the same time, wash the extracted sodium hydroxide solution with 10ml ether, combine with ether solution, Refined 3,4-dihydroxybenzoic acid with white powdery crystal appearance is obtained by adjusting the pH value to neutral and then evaporating and drying.

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