Synthesis of Cinnamic Acid

To a reflux apparatus (capped with a calcium chloride drying tube) add 20 mL of freshly distilled benzaldehyde, 30 mL of acetic anhydride and 12 g of anhydrous potassium acetate with stirring, reflux in 160°C for 1 h. Then reflux at 170-180°C for 3 h, while still hot (80°C) pour the contents into 100 mL of water and add as much of sodium carbonate until the mixture becomes strongly alkaline. Then set up a distillation apparatus and distill the mixture until the cloudiness disappears. The distillate can be discarded, the residue is then filtered and cooled down. As much of conc. HCl is added until no more bubbling occurs, cool the mixture in a freezer, filter and wash with some cold water. Recrystallize in hot ethanol.



The mixture after addition of water and refluxing

index (1)

Addition of sodium carbonate

index (2)

Steam distillation of the mixture

index (3)

The residue and the distillate

index (4)

The recrystallized product

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