- i8 7 - 



First of all the palladium chloride is reduced, after which pronounced 

 absorption of hydrogen is observed. Out of the mass which has re- 

 sulted from the process of reduction a limpid oil, m. p. 106 to 108 

 (15 mm.) could be isolated by distillation. This oil gave aldehyde- 

 reactions and yielded a semicarbazone (m. p. ?). Analysis showed that 

 it was probably citronellal. A second fraction boiling from 116 to 

 1 1 8° (15 mm.), gave no aldehyde reactions. It was possible to show 

 by analysis that citronellol had been formed by the absorption of 

 four hydrogen-atoms. 



In the process of reduction of citral it may therefore be taken 

 for granted that the dissolution of the a, /?- double - bond is first 

 accomplished, and after this the reduction of the aldehyde-group, 

 while the 6,7-double-bond remains intact. A third fraction boiled at 

 139 to 140 (15 mm.) and formed a viscous oil, which quickly con- 

 gealed in crystals. Recrystallised from alcohol, this body had a 

 m. p. of 57 . The fuchsine-test revealed the presence of an aldehyde- 

 group. The high b. p. rendered it improbable that a mono- molecular 

 aldehyde was here present. Determination of the molecular weight 

 by the cryoscopic method gave the figure 326,7, whereas the cal- 

 culation for the di-molecular aldehyde C 20 H 34 O 2 was 306. A further 

 proof was afforded by analysis of the semicarbazone. 



Hence Skita assumes this body to be an aldehyde-anal ogon of 

 the bi-molecular ketones which have been obtained by Harries from 

 a, ^-unsaturated ketones, and assigns to it for the first the following 

 formula 



CH 3 



CH 3 



• CH 3 



CH Q 



>C:CH.CH 2 .CH 2 .C(CH 3 ).CH 2 .CH0 1 ) 



>C:CH.CH 2 .CH 2 .C(CH 3 ).CH 2 .CHO 



In the same way, /3-cyclocitral, the cyclical analogon of citral, 

 gave as sole product of reaction the as yet unknown trimethyl-i, 

 1 ,3 -hexahydro-benzaldehyde-2 . 



H„ C C H„ H„ C C H„ 



V V 



H„c/ \;.CHO ILc/ ^CH-CHO 



I II > I I 



H 2 C^ yC-CH 3 H 2 Cv yCH-CH 3 



CH 2 CH 2 



/?-Cyclocitral Trimethyl- 1,1, 3-hexahydrobenzaldehyde-2 



3 ) In the original paper the bimolecular linking has been erroneously joined 

 to the C -atoms (2). 



