Preparation of 4-chloro-cinnamic acid

Raw material preparation
requires an appropriate amount of p-chlorobenzaldehyde, malonic acid and an appropriate amount of pyridine and other raw materials. P-chlorobenzaldehyde needs to ensure purity, the appearance should be colorless to light yellow liquid with a special odor; malonic acid should be white crystalline without obvious impurities; pyridine also needs to ensure quality, colorless or slightly yellow liquid.

Reaction process
In a clean reaction vessel, add p-chlorobenzaldehyde and malonic acid in a certain proportion, and slowly drop pyridine as a catalyst. During the reaction process, the reaction temperature must be strictly controlled and maintained at a suitable range, usually in a specific temperature range, the reaction system gradually changes. After close observation of the reaction phenomenon, it can be seen that the color of the solution is gradually changed, accompanied by slight bubbles. The condensation reaction between this aldehyde group and malonic acid under the catalysis of pyridine occurs, and the precursor material of 4-chloro-cinnamic acid is gradually formed.

Product separation and purification
After the reaction is completed, when the reaction liquid is cooled, suitable separation methods such as filtration and extraction are used. First, the insoluble substances that may be generated in the reaction are filtered off, and then the organic phase containing 4-chloro-cinnamic acid is extracted with a suitable extractant. Subsequently, the organic phase is distilled and other operations are performed to remove the extractant and other volatile impurities. Finally, the recrystallization operation is carried out, and a suitable solvent is selected to precipitate 4-chloro cinnamic acid in pure crystal form. After drying treatment, a relatively pure 4-chloro cinnamic acid product is obtained. The product is tested, and its color should be white to light yellow crystalline powder. The melting point and other indicators should meet relevant standards to ensure the purity and quality of the product.