— 212 — 



acid. Perkin's reaction, applied under various experimental conditions, 

 such as different durations of the reaction, different proportions of 

 benzaldehyde (origin not stated), sodium acetate and acetic anhydride, 

 as well as increased temperature, always yielded the same synthetic 

 cinnamic acid. In order to settle the point whether perhaps the cause 

 of the differences in the cinnamic acids was to be sought in the benz- 

 aldehyde, a benzaldehyde free from chlorine was carefully distilled. In 

 the course of frequently repeated fra< tionations the author succeeded 

 in recovering a "volatile constituent" as well as one boiling between 

 182 and 184 . By Perkin's reaction, storacic cinnamic acid was 

 obtained from the most volatile fraction (b. p. not stated), and hetero- 

 /3- cinnamic acid from the fraction with the highe>t b. p. 



In order to prove the connection between the special properties 

 of hetero-/?-cinnamic acid and the aromatic nucleus, the former was 

 oxidised with permanganate into benzaldehyde, and cinnamic acid re- 

 generated from this product. The acid, again, was hetero-/?-cinnamic 

 acid. Natural banzaldehyde containing hydrocyanic acid yielded chiefly 

 storacic-cinnamic acid. But when the aldehyde was split up into 

 fractions boiling respectively at 150 to 17 8° (I), 178 to 180 (II), and 

 180 to 180,5° (III) and each fraction treated by itself, fraction I 

 yielded storacic acid, fraction II synthetic acid, and fraction III 

 hetero-/?-cinnamic acid. This result indicates the probability that 

 when hydrocyanic acid is eliminated from the natural benzaldehyde 

 containing that acid, the benzaldehyde is converted into "synthetic" 

 benzaldehyde. As a matter of fact, the aldehyde referred to above, 

 when freed from hydrocyanic acid by our process, yielded synthetic 

 cinnamic acid. 



Erlenmeyer also mentions experiments for the reciprocal conversion 

 of the different cinnamic acids. He found, inter alia, that storacic 

 acid remains unaltered when boiled for 36 hours with caustic soda 

 liquor, whereas on prolonged exposure in the cold in concentrated 

 sulphuric acid it gradually becomes converted into hetero-/J-cinnamic 

 acid. In order to convert storacic cinnamic acid into the synthetic 

 product, the former is oxidised into benzaldehyde with permanganate 

 of potash, and from the latter, when condensed, synthetic acid almost 

 always results. The discovery that with Perkin's reaction, but in the 

 presence of copper, ordinary benzaldehyde yields storacic cinnamic 

 acid, is a remarkable one. 



A table containing data as to the manner in which storacic-cinnamic 

 acid, synthetic cinnamic acid and hetero-/?-cinnamic acid are obtained 

 and generated, is added to the paper. The results of an examination 

 of the crystallographic elements of the cinnamic acid dibromides and 

 the conductivity of the isomeric cinnamic acids (this latter by K. Bube), 

 are also given. The investigation is to be continued. 





