Preparation method of 3,4-dimethyl benzaldehyde

Abstract

The invention relates to the technical field of fine organic synthesis, and particularly relates to a preparation method of 3,4-dimethyl benzaldehyde. The preparation method comprises the following steps: 1) carrying out acylation: concretely acidizing 100 parts by weight of o-xylene and 150 parts by weight of 1,3-dioxane under an acidic condition, introducing nitrogen as replacement gas, adding 220 parts by weight of aluminum trichloride and 100 parts by weight of mixed Lewis acid to carry out catalysis, introducing 120 parts by weight of carbon monoxide, carrying out an acylation reaction ata temperature of 5 DEG C or lower for at least 12 hours; 2) carrying out washing: concretely washing the acylated solution by water at a water washing temperature of 0-5 DEG C; 3) carrying out distillation: concretely distilling the oil phase at a distillation temperature of 145-225 DEG C, condensing the effluent o-xylene into a liquid state, and then feeding the liquid o-xylene into a recovery tank; and 4) carrying out re-distillation. According to the invention, gas carbon monoxide can be better dissolved by taking 1,3-dioxane as a solvent, and the reaction can be carried out at normal pressure through the addition of a special catalyst, so that the requirements for reaction equipment are reduced; the reaction speed and selectivity are accelerated, isomers in the product are few, and purity of the prepared 3,4-dimethyl benzaldehyde is high.

Description

technical field [0001] The invention belongs to the technical field of fine organic synthesis, and in particular relates to a method for preparing 3,4 dimethylbenzaldehyde. Background technique [0002] 3,4-Dimethylbenzaldehyde is a fine chemical intermediate widely used in medicine, pesticides, spices, beverages, food and other fields, and can be used as a viscosity regulator, coagulant for organic pollutants, pharmaceuticals and cosmetics curing agent. In addition, 3,4-dimethylbenzaldehyde is a new type of non-toxic plastic additive, which can be used to synthesize a new type of polypropylene nucleating and transparent agent for the production of food packaging materials. [0003] The synthesis reaction of 3,4-dimethylbenzaldehyde first started in 1897 when Gattermann Koch introduced formyl groups to the aromatic ring. In the prior art, the synthesis methods of 3,4-dimethylbenzaldehyde mainly include indirect electro-oxidation synthesis method and organic chemical synthe...

AI Technical Summary

Problems solved by technology

Scheme two, organic chemical synthesis method is to be raw material with ortho-xylene and CO, under high pressure condition, obtain 3,4-dimethylbenzaldehyde through carbonylation reaction, the catalyst that adopts is generally protonic acid or Lewis acid, but because Due to the particularity of the structure of benzaldehyde, dimethylbenzaldehyde isomers will be produced in the product after the reaction, and there are many impurities, resulting in the low purity of the target product 3,4 dimethylbenzaldehyde; and the reaction requires High pressure conditions, strict requirements on equipment