( 567 ) 



Spec. gr.i„ 0,7565 

 Hn,, 1.49856. 



If we calculate the molecular refraction from these data, with the 

 aid of the formula of Lorentz — Loijenz, we find ^fK =^'S1,0S, 

 whilst for CsHg is found J/'/t = 28.53 assuming that the hydrocarbon 

 possesses tliree double bonds, and making use of the atomic retrac- 

 tions of CoNRADY ') and the increment for the double bond. 



The difference of 2,5 between the calculated and found molecular 

 refraction is a striking one. According to Brühi, ') excesses always 

 occur with substances with a conjugated system of double bonds. 

 In the aliphatic terpene ociniene, an excess (to the extent of 1.76) 

 is also found, and this assumes an extraordinarily large proportion 

 in the case of allo-ocimene. 'j 



As regards the structural foi-inula of the hydrocarbon obtained, 

 its formation from 



CH,==CH— CH— CH— CH=CH, 



! 1 



OH OH 



by the elimination of the two OH-groups by means of formic acid 

 points to the formula: 



CH,=CH— CH=CH— CH=CH, 

 which indeed represents 1.3.5-hexatriene. 



A glance at this formula shows that it may appear in two geo- 

 metrical isomeric forms, namely in the cis and tnnis form^): 



CH,=CH— CH CH„=CH— CH 



tl '^>Hl ■ '11 



C,H=CH— CH HC— CH=CH,. 



If, with Thiele *), we accept partial valencies the formula of 

 1.3.5-hexatrieiie should be written: 



CH,=CH^CH=ClQ'H:=('ll, 

 Unsaturated liydrocarixms with a conjugated system readily take 



1) Zeitschr. physik. Clieiu. 3, -i'^O. 



-, B.B. 38, 708. 



■'l G. J. Enklaar, Dissertation 190-5. Compare literature on the subject p. 87. 



■') Probably, the hydrocarbon is a mixture of both. Id the fractionation, besides 

 the main fraction, a distillate could be obtained bolting between 77.5^ and 78^.5 

 (sp. gr.j.j 0.7558, nnio 1.494 MR 30.8), also a final fraction boiling between 

 80°— 82' (sp. gr.m 0.7584, nnio 1.508, MR 31.2). We hope to repeat the expe- 

 riment on a larger scale. 



') Ann. 306. 94. 



