32 THE ROYAL SOCIETY OF CANADA 



If now, Harries continued, methyl butadiene (isoprene) poly- 

 merizes to form a synthetic rubber, after the same plan, it should 

 produce dimethyl cyclo octadiene of the constitution already given, 

 whose ozonide upon decomposition should yield laevulinic acid and 

 aldehyde. However, acetonyl acetone and succinic acid were ob- 

 tained instead. This, however, is easily understood if the poly- 

 merization of isoprene yielded unsymmetrical dimethyl cyclo octadiene 

 instead of the symmetrical compound. So that the synthetic rubber 

 from isoprene has the unsymmetrical constitution, and the fact that 

 acetonyl acetone and succinic acid are formed from the diozonide 

 instead of laevulinic aldehyde constitutes no objection to the main 

 contention of Harries. 



Pickles raised the objection that, according to the Harries con- 

 stitution, "the vague and unnecessary conception of polymerization" 

 is employed, and suggested that the rubber molecule consists of 

 isoprene groups linked up successively in one large ring, thus: 



-CH2.C-CH-CH2-CH2-C-CH-CH2-CH2-C-CH-CH2- 



CH3 CH3 CH3 



the ends of the chain- being connected so as to constitute a large ring 

 not further polymerized. He further suggested that the various 

 rubbers differ in the number of such nuclei in the ring. That is. 

 Pickles places all the isoprenes in the whole rubber molecule in one 

 huge ring, this molecule not being subsequently polymerized. 



It was about this time that Harries became suspicious of the 

 polymerized dimethyl cyclo octadiene constitution, having, among 

 other observations, found that the chlorine content of the hydro- 

 chloric acid addition product of rubber, CioHio 2 HCl, could be made 

 to fall below CioHie HCl, on heating with pyridine under pressure. 

 It would appear that Harries was scarcely justified in abandoning his 

 constitution on these grounds, for the actions seem altogether too 

 drastic to warrant drawing any definite conclusions at all regarding 

 the constitution of the original rubber molecule. However, he set up 

 a constitution very similar to Pickles, in that five molecules of isoprene 

 are linked together in a single ring. But he adhered to the notion 

 that this large ring must itself be polymerized to a compound of 

 much higher molecular weight (C25H.io)x- His objection to having 

 all the isoprenes in one ring without further polymerization was that 

 such a compound would not likely depolymerize easily, while it was 

 known that rubber undergoes a change (which Harries called de- 

 polymerization) when worked mechanically on hot rolls. 



