Preparation of 3-chloro-cinnamic acid
Preparation of raw materials
To make 3-chloro-cinnamic acid, several raw materials need to be prepared. The first requirement is 3-chlorobenzaldehyde, which is the key substance for the initiation of the reaction. The amount should be accurately weighed to match the reaction ratio. Malonic acid is also required, which is an important component involved in the reaction, and its purity and quality should be ensured. Pyridine is also required, which acts as a catalyst in the reaction process. Although the dosage is not large, it plays a key role and can promote the smooth progress of the reaction.

Reaction step
First place the clean reaction vessel in a stable place and inject an appropriate amount of pyridine. This is the beginning of catalysis. Then, slowly add 3-chlorobenzaldehyde, which is precisely weighed, and the operation needs to be careful to prevent it from splashing out. Then add malonic acid to the reaction vessel in sequence. After mixing the three, stir for a while to make the raw materials initially mixed. Then, move the reaction vessel to the heating device and heat it at a moderate temperature. During the heating process, pay close attention to the temperature change, and do not make the temperature too high or too low to prevent affecting the reaction process. As the temperature increases, the reaction gradually occurs, and the state and color of the substance in the container can be seen gradually change. After the reaction reaches the expected level, stop heating.

After the product is separated and purified
, a mixed system containing 3-chlorocinnamic acid is obtained. First cool it to room temperature, then use a suitable separation method. Filtration can be used to remove insoluble impurities in the system. The filtrate contains the target product and other soluble substances, and then by extraction, select the appropriate extractant to extract 3-chloro cinnamic acid into the organic phase. After that, the organic phase is distilled to remove the extractant, and crude 3-chloro cinnamic acid can be obtained. The crude product still contains a little impurities and needs to be further purified. The method of recrystallization can be used to select a suitable solvent, heat to dissolve the crude product, and filter it while it is hot. After the filtrate cools, 3-chloro cinnamic acid crystals precipitate. Filtrate again, wash the crystals with a small amount of cold solvent, and dry to obtain pure 3-chloro cinnamic acid.