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Method for synthesizing p-acetamidobenzoic acid as organic synthesis intermediate

A technology of acetaminophen and organic synthesis, applied in the preparation of organic compounds, organic chemistry, chemical instruments and methods, etc., can solve the problems of complex process and low final yield, reduce intermediate links, shorten reaction time, The effect of increasing the reaction yield

Inactive Publication Date: 2017-05-10
CHENGDU ZHONGHENG HUATIE TECH CO LTD
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, most of the existing synthetic methods are complicated in process, and the final yield is not very high. Therefore, it is necessary to propose a new synthetic method, which is useful for further improving the quality and yield of the product and reducing the content of by-products. important economic significance

Method used

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  • Method for synthesizing p-acetamidobenzoic acid as organic synthesis intermediate

Examples

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example 1

[0011] Dissolve 5mol of p-aminobenzoic acid in 1.5L of 80% formic acid solution with a mass fraction of 80%, control the stirring speed at 130rpm, add 6mol of formic acetic anhydride, increase the solution temperature to 50°C, continue stirring for 70min, and distill under reduced pressure at 50kPa for 50min. Add 2L mass fraction of 15% potassium chloride solution to the solution, reduce the temperature of the solution to 10°C, precipitate crystals, filter, wash with a mass fraction of 10% sodium bromide solution, and recrystallize in a mass fraction of 90% ether solution. The solid sodium hydroxide dehydrating agent dehydrates to finally obtain 814.45 g of p-acetaminobenzoic acid, with a yield of 91%.

example 2

[0013] Dissolve 5mol of p-aminobenzoic acid in 1.6L of 82% formic acid solution with a mass fraction of 82%, control the stirring speed at 140rpm, add 6.2mol of formic acetic anhydride, raise the solution temperature to 52°C, continue stirring for 80min, and distill under reduced pressure at 55kPa for 60min. Add 2.5L mass fraction of 17% potassium chloride solution to the remaining solution, reduce the temperature of the solution to 12°C, precipitate crystals, filter, wash with a mass fraction of 12% sodium bromide solution, and reapply in a mass fraction of 92% ether solution. Crystallization, dehydration with anhydrous calcium sulfate dehydrating agent, and finally 832.35 g of the product p-acetaminobenzoic acid was obtained, with a yield of 93%.

example 3

[0015] Dissolve 5 mol of p-aminobenzoic acid in 1.8 L of formic acid solution with a mass fraction of 85%, control the stirring speed at 150 rpm, add 6.5 mol of formic acetic anhydride, increase the temperature of the solution to 55 ° C, continue stirring for 90 min, and distill under reduced pressure at 60 kPa for 70 min. Add 3L of 20% potassium chloride solution to the remaining solution, reduce the temperature of the solution to 15°C, precipitate crystals, filter, wash with 15% sodium bromide solution, and recrystallize in 95% ether solution , solid sodium hydroxide dehydrating agent dehydration, the final product p-acetaminobenzoic acid 859.20g, yield 96%.

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Abstract

The invention provides a method for synthesizing p-acetamidobenzoic acid as an organic synthesis intermediate. The method comprises following steps: 5 mol of para aminobenzoic acid is dissolved in a 1.5-1.8 L of a formic acid solution, the stirring speed is controlled to be 130-150 rpm, 6-6.5 mol of acetic formic anhydride is added, the temperature of the solution is increased to 50-55 DEG C, the solution is stirred continuously for 70-90 min and is subjected to reduced-pressure distillation for 50-70 min, 2-3 L of a potassium chloride solution is added to the residual solution, the temperature of the mixed solution is reduced to 10-15 DEG C, crystals are separated, filtered, washed with a sodium bromide solution, recrystallized in a diethyl ether solution and dehydrated with a dehydrating agent, and a p-acetamidobenzoic acid product is obtained finally, wherein the mass fraction of the formic acid solution is 80%-85%, the pressure of the reduced-pressure distillation is 50-60 kPa, and the mass fraction of the potassium chloride solution is 15%-20%.

Description

technical field [0001] The invention relates to a method for synthesizing an organic synthesis intermediate p-acetaminobenzoic acid. Background technique [0002] Paracetamol benzoic acid is used in organic synthesis. Most of the existing synthesis techniques use p-toluidine as raw material, which is obtained through acetylation and oxidation. Acetylation still uses acetic anhydride as raw material, and potassium permanganate is used for oxidation. The oxidation temperature is 60-70°C. However, most of the existing synthetic methods are complicated in process, and the final yield is not very high. Therefore, it is necessary to propose a new synthetic method, which is useful for further improving the quality and yield of the product and reducing the content of by-products. important economic significance. Contents of the invention [0003] The object of the present invention is to provide a kind of synthetic method of organic synthesis intermediate p-acetaminobenzoic acid...

Claims

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Application Information

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IPC IPC(8): C07C231/02C07C233/54
CPCC07C231/02C07C233/54
Inventor 彭响亮
Owner CHENGDU ZHONGHENG HUATIE TECH CO LTD
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