SCIENCE PROGRESS 



C CMS 



20. 



ffubber 



HC=0 = 



I 

 ? 



CHj.C=0 = O 



laeuu/inic Atdetyc/e 



Superox/de 



r 



HC-O 



£ GP.UuhniC 

 Aia'ehydc 



This indicates that the rubber nucleus is an eight-membered 

 ring. And its formation from isoprene is represented thus : 



CH 3 



I 

 ,'~C 



1/ \ 



CH CH 2 



II 

 CH2 CH 2 



II 

 CH 2 CH 



% /\ 



CH 3 



I 



— c 



s \ 



-CH CH 2 



I I 



CH 2 CH 2 



I I 



CH 2 CH— - 



\ ^ 

 C — 



H 3 C 



Rubber. 



H 3 C 



2 molecules Isoprene. 



The dotted lines denote partial valencies according to Thiele's 

 theory. And Harries supposed that an indefinite number of 

 rings might be linked together at the double bonds. This view 

 was criticised by Pickles in 1910, who preferred to think that 

 the C 5 H 8 nuclei unite to form long chains as : 



CH 3 CH 3 CH 3 



I I I 



— CH 2 . C : CH . (CH 2 ) 2 . C : CH . (CH 2 ) 2 . C : CH . CH 2 — 



In 19 14 Harries proposed a new formula for rubber con- 

 sisting of five QH 8 groups united to form a C 20 ring. Rubber 



