524 



TRANSACTIONS OF SECTION B. 



decomposiliou of the diozonide, which can be represented as taking place iu two 

 phases. 



1st phase: — 



CioU,A = CH3 . C-CHj-CHj-CH + CHj , CO . CII^ . CH„ . CHO 



II II 



0=0 =0=0 



3nd phase : — 



C,oH,A + 2H20 = 2CH3 . CO . CH, . CH, . CnO + 2H„0,- 



The hydrocarbon 0,^11,,, must thus contain a cyclic nucleus, the above com- 

 ponents having resulted from the ozonide. 



CH, 



CH,./' 



I " 

 CH, 



CO 



OCH 



\ 



CHj 



I 

 CH, 



CH3 



I 

 CO 



/ 



\ 



CHO 



OC^^ 



I 

 CH, 



CHi, 



I 

 CH, 



Ozonides 



CU, 



I/' 



O 



t 



or II. 







\ 



CHO 



CH, 



CH3 



I 

 OC 



CH^ 



I 

 CH 



/ 



OCH 



.0, 



CH, 



CH, 



CH, 



I 

 CH- 



\CH 



CH2 



I 

 CH, 



I ■ 

 CCCHJ 



hy^^i 



H.,C 



I 

 H..C 



The hydrocarbon itself must then have the formula — 

 CH, 



or II. 



HC- 



\o, 



,0 



/ 



CHj 



I 

 CH3 



I 

 -CH 



\o/' 



CH, CH, 



I I 



c = c 



I I 



CHj CH, 



I r 



CHj CH, 



I r 



CH = CH 



In consideration of the facts that isoprene and dipentene are formed on the 

 distillation of rubber, constitution II. is discarded, as constitution II. alone allows 

 of a simple explanation of these transformations. 



The conclusion from this investigation is that the fundamental hydrocarbon 

 in rubber is 1 : 5 dimethyl-cyclo-octadiene (1 : 5). At first sight this is surprising, 

 as the synthetical formation of 8-c.arbon rings is a matter of great difficulty, only 

 one such compound having been made, viz., azelone. R. Willstatter has, how- 

 ever, recently obtained a cyclo-octadiene from granatoine and demonstrated its 

 tendency to ready polymerisation. Guttapercha, on treatment with ozone, yielded 

 the Sime products of decomposition as were obtained iu the case of indiarubber, 



