374 CINNAMIC ACID. 



Cinnamic Acid. 

 C 9 H 8 2 = C 6 H 5 .CH:CH.CO.OH. 



Occurrence and formation. In storax, in Tolu- and 

 Peru-balsams (p. 312), and in a few varieties of gum- 

 benzoin. Is formed from cinnamic aldehyde by oxida 

 tion ; by boiling styracin with potassa ; by the simul 

 taneous action of sodium and carbonic anhydride on 

 a-bromcinnamene ; and by heating oil of bitter almonds 

 with acetyl chloride. 



Preparation. Most advantageously from storax. 

 This is boiled for a long time with a solution of sodium 

 carbonate or with potassa-ley, the clear solution of so 

 dium or potassium cinnamate filtered off from the un- 

 dissolved resin, and the cinnamic acid precipitated by 

 hydrochloric acid. By recrystallizing from hot water 

 or by subliming, it is purified. 



Properties. Crystallized from hot water, it forms 

 fine needly crystals; from alcohol, large, clear, easily 

 cleavable prisms ; inodorous ; of a weak taste ; fuses at 

 133, and is distillable almost completely without 

 decomposition. Monobasic acid. Very similar to 

 benzoic acid ; its salts also resemble the benzoates 

 very strongly, but give a yellow precipitate with iron 

 chloride; fusing potassium hydroxide converts it into 

 benzoic and acetic acids. Subjected to the influence 

 of oxidizing agents (dilute nitric acid, potassium 

 hypermanganate, potassium bichromate, and sulphuric 

 acid), it yields oil of bitter almonds and benzoic acid. 

 Nascent hydrogen converts it into hydrocinnamic acid 

 (p. 342). Heated with water to 180-200, and with 

 lime, it is resolved into carbonic acid and cinnamene. 



Ethyl cinnamate, C 9 H 7 2 .C 2 H 5 , is produced by 

 conducting hydrochloric acid gas into a solution of 

 cinnamic acid in absolute alcohol. 



Benzyl cinnamate, C 9 H 7 2 .C 7 H 7 , is contained in 

 Tolu- and Peru-balsams ; and is produced by heating 

 sodium cinnamate with benzyl chloride. Lustrous 



