( 720 ) 



terpenederivatives as yet known, it is a derivative of dimethyl- 

 2-6 octane : 



CH, 



On account of the proved identity of tlic bromides, ociniene should 

 also possess this carbon skeleton. Now when we accept the correct- 

 ness of the hydrogenation principle of conjugate systems'): 



\ / \ / 



C = C — C==C +2H^H — C — C = C — C — H 



/ I I \ / I I \ 



it is, in the carbon branch formation of dimethyl 2— 6-octane, only 



then possible for difTerent triënes to give identical diënes, when these 



triënes possess the following conjugate systems : 



c c— c c c — c 



C = C c — C and C=C ...■■•• C = G/ 



c ,c = c / c /c = c / 



I II 



and Avhen the third double link occupies the same position in both 

 formulae, and is not conjugate with the other double links. For 

 this third double link 1 or 2 is the only possible position ; on 

 account of my experiences as to the oxidation of ocimene, I should 

 be inclined to accept the position 2, although the position 1 has still 

 quite as much right of existence'). Perhaps, as Semmi.er believes, 

 myrcene may contain both forms (ortho and pseudo form). 



Dihydro-ocimene and dihydromyrcene then assume the formula of 

 dimethyl 2^6 octadiene 2 — 6 : 



1) For exact details and the literature of this liydrogenation principle, I must 

 refer to my dissertation p. 26. 1 wish only to point out particularly, that my rule is not 

 based on the theory of Thiele, but has been deduced in a purely empirical manner. 

 I, therefore, make a distinction between the addition of hydrogen and that of other 

 substances which may prove more complicated. 



-) Admitting for this third double link the position I, yet another couple of 

 formulae seems possible; on account of other facts the latter must however be 

 rejected. 



