Process for the preparation of cinnamic acid and coumarin

摘要

Cinnamic acid and coumarin are produced on an industrial scale in a Perkin synthesis by heating the mixture of the reactants benzaldehyde, or salicylaldehyde, with acetic anhydride and sodium acetate. This results in a yellow or brown colouration which must be removed during working-up by filtration with active carbon. The invention utilises the scientific finding technically in such a way that the first step to be carried out is an enolisation with the aid of the condensing agents such as sodium acetate together with another condensing agent such as sodium formate or their alkali metal salts of carbonates and acetates, respectively, followed by an addition of aldehyde in a constant stream with vigorous stirring, and immediately removing by distillation at the same rate the amounts of water and acetic acid formed by the effluent of the reaction.