Process of preparing malonic ester

Abstract

This invention relates to a method to synthesize malonate from chloroacetic acid, which includes neutralization, cyanidation, acidification, dehydration and esterification. It has the characteristics that dilute sulphuric acid is added after dehydration so that cyanoacetic acid is hydrolyzed into malonic acid which is then esterified to obtain malonate. This invention has the advantages of low cost, easily-controlled technique and high yield.

Description

technical field [0001] The present invention relates to the preparation method of malonate, specifically is the method for the synthesis of malonate with chloroacetic acid as raw material. Background technique [0002] Malonate products such as dimethyl malonate are widely used as industrial raw materials for medicine, pesticides and cosmetics. The traditional production process uses chloroacetic acid as raw material, through neutralization, cyanation, acidification, dehydration, esterification Such steps are realized, but the yield is relatively low. This is mainly because it is required to completely remove the water during dehydration, and as the amount of water decreases, the dehydration temperature will gradually rise above 110°C, which will intensify the decomposition of the intermediate product cyanoacetic acid, resulting in the yield of the final product malonate The rate is lower. Therefore, many improved malonate synthesis methods have adopted the hydrolysis proc...

AI Technical Summary

Problems solved by technology

For example, the Chinese patent CN1200368A discloses a method for preparing malonate in which hydrolysis, esterification, and extraction are carried out simultaneously. This method requires controlling the water content in the system after cyanoacetic acid dehydration is 6%, otherwise the water content in the system is too small. It will affect the hydrolysis of cyanoacetic acid, make the hydrolysis of cyanoacetic acid incomplete, and cause the product quality to be unqualified; and the moisture content in the system is too much, the balance of its esterification reaction will be affected, and the yield of malonate will be significantly increased. decline

But obviously, in this method, it is difficult to control the moisture content of the system after dehydration in the production process, because the dehydration residue cannot be sampled and analyzed, so this method is difficult to realize in the actual production process