Theory of Molecular Volumes. 451 



The Di-terpenes, C 2 oH 32 . 



Several di-terpenes have had some of their physical 

 properties determined. 



Di-terpene C 20 H 32 , d 15 . 5 0*9525, B.P. 320-325° 

 Colophene „ 0*940 318-320° 



Owing to compact ring structure we take K = *45, as for 

 the sesquiterpenes. 



This gives for di-terpene d BP 0*7671 a volume of 351*8. 



2A.V. 112x3*70 = 414*4. 



The difference for ring structure is 



414-4- 351*8 = 62-6 (4x15-6). 



Di-terpene is thus a Tetracyclic compound, 



I. e. a polymerization of four mols. of C 5 H 8 and the 

 formation of four rings. 



There is thus a bridging of the first ring. We find 



CH 3 

 I 



— CH ~ CH 2 -CH - CH 2 ~ C 



Bridged 

 Bing. 



— C — CH 2 ~ C — CH 2 — CH 



CH S 



The Polymethylenes. 



An interesting class of compounds, of which one member, 

 hexamethylene C 6 Hi 2 , has already received attention, is that 

 of the Polymethylenes, w(CH 2 ). 



C 6 H 12 ... B.P. 79°-0, V 105*2, V BP 116*3, K=*047. 



Adopting this value for all the polymethylenes, we find : — 



The Polymethylenes. 

 Compound. W. M.V. SA.V. A for B. 



Cyclobutane, C 4 H 8 ...24 [80*2] ^'?> - S'6 Q 4 



CH 2 — CH 2 



I I 



CH 2 CHj 



2 G2 



