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Synthetic method of 8-hydroxyquinoline

TIME:22-10-28    NUM:0

1. It is obtained by cyclization reaction of o-aminophenol. Add glycerin into the acid-resistant reaction pot, slowly add concentrated sulfuric acid under stirring, and simultaneously add o-aminophenol and o-nitrophenol in sequence, and add 65% of the total oleum first. Heat up to 125°C, stop heating, naturally heat up to 140°C, and wait until the temperature returns to 136°C. The rest of the oleum was continued to be added, maintaining the temperature at 137°C. After adding acid, keep warm for 4h, cool to below 100, pump into an acid-resistant pot containing 10 times the amount of water (calculated by o-aminophenol), stir, heat to 75-80, use 30% sodium hydroxide The solution was neutralized to pH 7-7.2. The precipitate is released while hot, cooled into a block, and sublimed under reduced pressure to obtain the finished product of 8-hydroxyquinoline.


2. Mix o-aminophenol, o-nitrophenol, glycerin and glacial acetic acid, add concentrated sulfuric acid in stages, and heat the mixture until it starts to boil. Then, it was refluxed on an oil bath, and the unreacted o-nitrophenol was removed by steam distillation. Cool, neutralize with sodium hydroxide solution, and recover by steam distillation to obtain 8-hydroxyquinoline.


3. 8-sulfoquinoline is obtained by sulfonation of quinoline, then 8-hydroxyquinoline base is obtained by alkali melting, and finally 8-hydroxyquinoline is obtained by acidification. The preparation process is as follows:

Sulfonation process Using quinoline as raw material, slowly add the raw material into sulfuric acid under stirring conditions, heat in a sand bath, and sulfonate at 100-180 °C for 2-3 hours. Then naturally cooled to room temperature, further cooled with ice water, filtered and dried to obtain the product 8-sulfoquinoline.

Alkali melting process Under stirring conditions, slowly add the sulfonated product to the molten alkali, melt at about 200 to 240 ° C for 30 to 40 minutes, add hot water after cooling, and heat to dissolve all of it, and cool to room temperature Then, neutralize with dilute acid to pH=7, after the crystallization is precipitated, suction filtration, and the filter cake is air-dried.

Distillation process: Distill the alkali melting product with steam, cool it, and crystallize the product 8-hydroxyquinoline.