211 



in a paper in which the author endorses Biilmann's theory on the 

 trimorphy of the isomeric cinnamic acids. Referring to Biilmann's 

 assertion that the cinnamic acids melting respectively at 38, 46, 57, 

 and 68° are chemically identical, Liebermann points out, however, 

 that the fact that separate modifications can exist within so wide a 

 range of temperatures indicates that the differences between these bodies 

 are not only crystallographical but also to some extent chemical. Lieber- 

 mann moreover shows that mere mechanical manipulations, such as 

 rubbing, may cause the acid melting at 42 to 43 ° to become 

 converted into the variety melting at 65 to 66,5°. He also noticed 

 that the wa-acid, m. p. 5 8°, especially after being comminuted, was con- te 

 verted into the <2//<9-acid, m. p. 68°, after prolonged exposure to light. 



Meanwhile Biilmann 1 ) has continued his earlier investigations and 

 has been able to confirm the observations he has already made with 

 regard to the ready conversion of the three cinnamic acids as well 

 as his theory of a trimorphy of the three acids, although the behaviour 

 of the acids melting respectively at 58 and 68° points to the existence 

 between them of differences which up to the present have not yet 

 been explained. 



Without entering into details of the experiments, we desire to give a 

 synopsis of the results of Erlenmeyer's 2 ) most recent investigations, 

 which form a continuation of this author's work to which we referred 

 in our last Report 3 ). 



The author's investigations show that hetero-cinnamic acid can 

 be formed in plants, although only in comparatively small proportions. 

 As regards the cinnamic acids which are made by various synthetic 

 processes, the heating of benzalacetone with sodium hypochlorite (accor- 

 ding to the process of the Farbwerke Meister, Lucius and Briming) pro- 

 duced mixtures of storacic and hetero-cinnamic acid. Heating 

 of benzal-malonic acid with glacial acetic acid (Claisen's and Crismer's 

 process) 4 ) resulted in alio- cinnamic acid accompanied by similar acids, 

 which separated out in the crystalline form of storacic and hetero- 

 cinnamic acids. Cinnamic acid ester prepared according to Claisen 5 ) 

 and Erlenmeyer 6 ) from acetic ester and benzaldehyde by condensation 

 with sodium, yielded, when saponified, synthetic cinnamicacid. 

 Phenylpropionic acid, when reduced with zinc-dust and glacial acetic 

 acid (Aronstein's and Holleman's process) 7 ), yielded storacic cinnamic 



*) ibidem 42 (1909), 1443. 



2 ) ibidem 42 (1909), 2649 and 2655. 



3 ) ibidem 42 (1909), 502; Report April 1909, 138. 



4 ) Liebig's Annalen 218 (1883), 135. 



5 ) Berl. Berichte 23 (1890), 977. 



6 ) Liebig's Annalen 275 (1893), 12. 



7 ) Berl. Berichte 22 (1889), 1181. 



14" 



