138 



Report of Schimmel $ Co. April 1913. 



saturated, two rings must exist both in it and also in selinene. But in the process 

 of oxidising with alkaline bromine solution an acid is formed which contains only one 

 carbon atom less, from which fact Semmler and Risse conclude that the two keto- 

 groups can only exist in one single form, that is to say, once as a methyl keto-group 

 and the second time as a keto-group in ring-formation. From this they again conclude 

 that the structure of natural selinene can only be of such a character that at one time 

 a methylene-group occurs in a side-chain, while the second time a methylene-group 

 is directly bound to the ring. Hence, natural selinene would belong to the class of 

 pseudo-sesquiterpenes (semicyclic sesquiterpenes). When natural selinene (ortho-selinene) 

 is ozonised, there is formed a small proportion of an acid product which has been 

 shown to be identical with the acid from regenerated selinene described below. 



The latter body yielded, as a neutral ozonisation-product, the diketone described 

 above (semicarbazone, m. p. 228°) and, as an acid oxidation-product, an acid: selinene- 

 diketo monocarboxylic acid, C14H22O4, of which the methylester boils between 185 

 and 190° (11mm.): d 20 o 1,0635, « D + 4°24', n D 1,47889. As only an exceedingly minute 

 proportion of diketone had been formed, the authors assume that in the process of 

 regeneration the semicyclic selinene is generated only in a minor degree. The formation 

 of a diketomonocarboxylic acid appears to indicate that during the elimination of 

 hydrogen chloride the double bond has been transposed into the ring. The following 

 formulae are given in order to make the separate reactions more intelligible: — 



H :; C X ^CH> 



HsCx^ /CH £ 



CC1 

 I 

 CH, CH 



H 2 C 7 ch CH 2 



HC! 



HC X ?V JCH 2 



H2W £ H |CH 2 KOH + CH3OH H 2 C 



— — > 



H 3 C 



CH., C 



CH 2 



Sem. /».sr«rfo-(yc/)-selinene (natural). 

 Ozone I 



H 8 C 



H :! C 



CH 2 



' CH ;! 



Selinene dihydrochloride. 



Diketone. 



■" ^CH 



H 3 C CH 2 C 



I 

 CH 3 



Ortho-(a)-se\'mene. 

 I Ozone 



H 3 C 



CH 3 



Diketomonocarboxylic acid. 



The natural selinene is therefore a mixture, which consists principally of semicyclic 

 pseudo-(/?)-selinene, and contains but little ortho-(«)-selinene. 



