Method for preparing 3-methyl-4-nitrobenzoic acid by oxidizing with nitric acid

Abstract

The invention relates to a method for preparing 3-methyl-4-nitrobenzoic acid by oxidizing with nitric acid. The method comprises the steps of carrying out oxidation reaction, neutralizing, extracting, decolorizing and acidifying, wherein diluted nitric acid serves as an oxidant, and 2,4-dimethyl-nitrobenzene serves as a basic raw material. The feed ratio, the reaction temperature, the reaction pressure and the reaction time are controlled reasonably, thus the problems of low reaction conversion rate and generation of many by-products are solved. Because the diluted nitric acid serves as the oxidizing agent and replaces potassium permanganate, potassium dichromate, chromium trioxide and other strong oxidizing agents which are high in cost and are difficult to recover, and the generated waste acid can be recycled, the cleanness of industrial synthesis reaction can be improved, and the pollution to environment can be reduced. The method provided by the invention has the advantages that the reaction yield is improved to over 50% from the initial 27%, the reaction condition is mild, the production and operation safety is high, the reaction equipment is simple, and the raw materials including nitric acid and 2,4-dimethyl-nitrobenzene are wide in supply and low in cost and are suitable for large-scale industrial production.

Description

technical field [0001] The application relates to the field of synthesis of fine chemical products, in particular to a method for selectively oxidizing raw material 2,4-dimethylnitrobenzene into 3-methyl-4-nitrobenzoic acid by using dilute nitric acid as an oxidant. Background technique [0002] The concentrations of all materials described herein are mass concentrations. [0003] 3-Methyl-4-nitrobenzoic acid is a fine chemical product with high added value. Many important organic products can be further synthesized from it, such as ethyl 4-chloroquinazoline-6-carboxylate, 2- n-Propyl-4-methyl-6-carboxybenzimidazole, 4-methyl-2-ethyl-1H-benzimidazole-6-methyl carboxylate, 3,4-dihydro-4-quinazoline Homo-6-carboxylic acid, 4-aminophenyl-1,3-dicarboxylic acid, 4-amino-3-methylbenzoic acid methyl ester, 4-nitrophenyl-1,3-dicarboxylic acid, etc.; another 3 -Methyl-4-nitrobenzoic acid is also used in medicine and is an important intermediate in the synthesis of antihypertensive ...

AI Technical Summary

Problems solved by technology

The above method has a high yield, but its catalyst and oxidant are expensive, and post-treatment such as catalyst recovery is difficult, and the production cost is high; although the nitric acid oxidation method will produce a large amount of oxidant, it can be recycled and recycled

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