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Preparation of pyrogallic acid with pyridine as decarboxylation catalyst of 3,4,5-trihydroxybenzoic acid

A technology of pyrogallic acid and gallic acid, applied in chemical instruments and methods, preparation of organic compounds, organic chemistry, etc., can solve the problems of low yield, unreported, poor product quality, etc., achieve high yield, improve Purity, product quality good effect

Inactive Publication Date: 2006-08-23
INST OF CHEM IND OF FOREST PROD CHINESE ACAD OF FORESTRY
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

This preparation process yield is lower, and product quality is also poorer
In recent years, China has also used the atmospheric pressure catalytic decarboxylation method to prepare pyrogallic acid, which has obtained higher product yield and better product quality, but no catalyst has been reported.

Method used

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  • Preparation of pyrogallic acid with pyridine as decarboxylation catalyst of 3,4,5-trihydroxybenzoic acid
  • Preparation of pyrogallic acid with pyridine as decarboxylation catalyst of 3,4,5-trihydroxybenzoic acid

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Experimental program
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Effect test

Embodiment 1

[0029] A method for preparing pyrogallic acid with pyridine as a gallic acid decarboxylation catalyst, comprising the following steps:

[0030] In the first step, anhydrous gallic acid and pyridine are stirred and mixed at a molar ratio of 1: (0.1-0.4), and reflux reaction is performed at 130-160°C. The material becomes a melt and a large amount of CO 2 Bubbles escape, keep warm until no bubbles are generated in the reaction product,

[0031] Wherein, the ratio of the amount of substances of anhydrous gallic acid and pyridine can be 1: 0.15, 1: 0.18, 1: 0.22, 1: 0.27, 1: 0.33, 1: 0.36, 1: 0.38, and the temperature of the reflux reaction can be 135°C, 146°C, 153°C, 158°C; the holding temperature is the same as the reflux reaction temperature, which is 130-160°C;

[0032] In the second step, keeping the temperature of the reaction product at 130 to 160° C., and gradually reducing the pressure of the atmosphere of the above reaction product to below 2 kPa from 1 standard atmosph...

Embodiment 2

[0039] Weigh 30g of anhydrous gallic acid and place it in a flask with a stirring and condenser tube, add 5ml of pyridine, and heat to 155°C under reflux for reaction under stirring. The material becomes a melt, and there is a large amount of CO at the same time 2 Bubbles escape. Incubate the reaction until no bubbles are formed. At normal pressure first, then depressurized to 2kPa, pyridine was distilled at 155°C. Continue vacuuming until the pressure is below 2kPa, and slowly raise the temperature to 175°C, and the product begins to sublimate. Keep the temperature and vacuum constant until no sublimation products escape. Take out the product and grind it, put it into a washing container, add 70ml of chloroform, stir and wash thoroughly. After filtering, rinse with a small amount of chloroform. After filtering and drying, the residual chloroform was removed in a vacuum oven at 55°C to obtain 18 g of the product. The yield is 81%. The product yield refers to the ratio of...

Embodiment 3

[0041] Weigh 100 g of anhydrous gallic acid and place it in a flask with a stirring and condenser tube, add 10 ml of pyridine, and heat to 135° C. for reflux reaction under stirring. The material becomes a melt, and there is a large amount of CO at the same time 2Bubbles escape. Incubate the reaction until no bubbles are formed. At normal pressure first, then depressurized to 2kPa, pyridine was distilled off at 150°C. Continue vacuuming until the pressure is below 2kPa, and slowly raise the temperature to 160°C, and the product starts to sublimate. Keep the temperature and vacuum constant until no sublimation products escape. Take out the product and grind it, put it into a washing container, add 180ml of chloroform, stir and wash thoroughly. After filtering, rinse with a small amount of chloroform. After filtering and drying, the residual chloroform was removed in a vacuum drying oven at 60°C to obtain 59 g of the product. The yield was 81%.

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Abstract

Production of pyrogallic acid with pyridine as gallic acid decarboxylation catalyst is carried out by agitating and mixing anhydrous gallic acid with pyridine, refluxing reacting, material forming melt, CO2 bubbles escaping, keeping temperature until bubble not escaping from reacting product, keeping temperature of reacting product, releasing pressure of the atmosphere, distilling out pyridine of reacting product, raising temperature for the reacting product, collecting escaped sublimed product until sublimed product non escaping, grinding the sublimed product, adding chloroform, agitating and washing, dissolving the residual pyridine into chloroform, filtering, drip washing by chloroform, filtering, drying, removing residual chloroform, and obtaining pyrogallic acid. It achieves low boiling point, suitable alkalinity and easy separation.

Description

technical field [0001] The invention relates to a method for preparing pyrogallic acid, in particular to a method for preparing pyrogallic acid by using pyridine as a gallic acid decarboxylation catalyst. Background technique [0002] At the end of the 18th century, Scheele was the first to obtain pyrogallic acid from gallic acid by dry distillation. Since then, the preparation methods have been continuously developed, which can be generally divided into two categories: semi-synthetic methods and total synthetic methods. [0003] The semi-synthetic method uses gallic acid as raw material for decarboxylation. At first, it was direct heating and dry distillation, which had many by-products and low product yield; later, it developed into vacuum decarboxylation, solvent decarboxylation and high-pressure decarboxylation in aqueous medium. In 1976, Polish patents (Pol.87,354, Pol.83,789) proposed to use N,N-dimethylformamide as a catalyst for decarbox...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C07C39/10C07C37/00
Inventor 陈笳鸿汪咏梅吴冬梅吴在嵩
Owner INST OF CHEM IND OF FOREST PROD CHINESE ACAD OF FORESTRY
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