Cinnamic acid, chemical name 3-phenyl-2-propenoic acid, is an important fine chemical intermediate, widely used in the production of pharmaceuticals, spices, plastics and photographic materials and other products, but also an intermediate in the pre-chiral compounds of the new sweetener aspartame.
Cinnamic acid has two isomers, cis and trans, and is commonly trans. Cinnamic acid is colorless needle-like monoclinic crystals, insoluble in cold water, soluble in hot water, ethanol, ether, acetone and glacial acetic acid. Cinnamic acid is decarboxylated into styrene when heated, and benzoic acid is generated when oxidized. Cinnamic acid is found in Tolu balsam, suhagi balsam, etc. It is mainly used in the production of esters. Cinnamic acid is mainly used in the production of esters for the preparation of lilac-type floral flavors and medicines.
Report I.
In a 1000mL four-necked flask, insert a stirrer, a thermometer, a dropping funnel, and a rubber tube connected to an oxygen cylinder. Add 20g of caustic soda, 600mL of water, and 6g of silver/copper catalyst, stir to raise the temperature, pass oxygen at a flow rate of 4L/min, and control the temperature at 45-50°C. After 10 minutes, start to add 60g of cinnamaldehyde dropwise at a flow rate of 0.5g/min, and continue to pass the oxygen for 15 minutes after completion of the dropwise addition. The filtrate was filtered off to obtain a light yellow solution, and the filtrate was washed with water. The washings were combined with the filtrate, warmed to 70-80 ° C, added hydrochloric acid, adjusted the pH to 2, cooled to room temperature, filtration, drying to obtain 64.5 g of white crystals of cinnamic acid, whose melting point is 132-133 ° C, the yield is 95.8%.
Cinnamic acid exists in cis and trans isomers. The trans isomer can be used as food flavorings, in addition to extracted from natural raw materials (thujone), can also be prepared according to the following method; 1. from benzaldehyde, anhydrous sodium acetate and acetic anhydride in the presence of pyridine to start the Bergen reaction. 2. from benzaldehyde and ethyl acetate to start the Kerbenzene biocondensation reaction. 3. from benzaldehyde and acetyl chloride reaction. 4. from benzylidene forked acetone oxidized by sodium hypochlorite. Production method (1) of the following: 32.5 kg of anhydrous potassium carbonate, 25 kg of acetic acid into the reaction pot, slowly heated to 120 ° C, to be carbon dioxide gas is reduced, dropwise addition of 100 kg of benzaldehyde and 100 kg of acetic anhydride. Under stirring, heated to 150-160 ℃, control the temperature at the top of the fractionation column tower at about 120 ℃, to be about 45 kg of acetic acid evaporated, and then drop-added acetic anhydride 75 kg, when there is no longer acetic acid evaporated, the reaction temperature will be raised to 180 ℃. The excess acetic anhydride was evaporated and ended about 3h. Add 10% sodium hydroxide to neutralize to pH=9. Pass through steam to remove a small amount of benzaldehyde placed overnight. Acidification with 10% hydrochloric acid, at this time that there is a white precipitate precipitation, to pH = 5, with a centrifuge shake filter, washing, and then cinnamic acid in 100 ~ 110 ℃ drying room blast drying, get cinnamic acid finished product.