28 THE ROYAL SOCIETY OF CANADA 



and to describe some new rubber reactions and new rubber compounds 

 which substantiate, in a measure, a new constitutional formula which 

 appears not only to be in harmony with the new facts, but also 

 adequately to express the older ones. The chief virtue of these new 

 rubber derivatives, which we have made, for constitutional purposes, 

 lies in the fact that in the reactions used in producing them, the 

 rubber molecule was only very slightly altered, in some cases the 

 depolymerization of the main nucleus of carbon atoms not having 

 occurred, I believe, at all. Evidently such reactions should throw 

 considerable light upon the extent of the rubber molecule, and, in 

 conjunction with those reactions involving a partial splitting off of 

 groups from this nucleus, should enable the derivation of a satis- 

 factory structural formula to be attempted. 



Review of Literature 



There is no occasion here to review exhaustively the literature. 

 This has already recently been done by others, notably by Harries in 

 Liebigs Annalen der Chemie, and in his Untersuchungen iiber 

 Kautschukarten. I shall accordingly review the reactions only in 

 sufficient detail to make clear their bearing upon the problem of 

 constitution. 



The products formed by the destructive distillation of rubber 

 were investigated by Williams (1), Wallach (2), Bouchardat (3), 

 Fischer (4), Harries (5) and others. Among the products isoprene 

 and dipentene were identified. The importance of isoprene was 

 emphasized by the discovery by Bouchardat (6) and by Tilden (7) 

 that this hydrocarbon could be polymerized by dilute hydrochloric 

 acid and by long standing to form rubber like masses. 



CH3 



Tilden (8) had proposed the formula CH2 = C — CH = CH2 for 

 isoprene, and this constitution was verified by Ipatiew and Wittorf (9). 

 Ipatiew (10) also showed the so-called isoprene fraction, obtained on 

 distilling rubber, to be a mixture chiefly of isoprene and trimethyle- 

 thylene. 



More recently a number of syntheses of isoprene have been 

 developed both in England and Germany, many of them covered by 

 patents. Also much work has been carried out, notably by Harries 

 (11) at Kiel, and by Perkin, Matthew and Strange (12) in London 

 upon the polymerization of isoprene to rubber by means of acetic 

 acid and metallic sodium. 



