[ 443 ] 



LIIL The Constitution of the Aromatic Nucleus. By S. A. 

 Swokn, B.A., Assoc. R.C.Sc.I., late Brackenbury Scholar 

 of Balliol College, Oxford. 



[Concluded from p. 415.] 



II. Arguments against Meyer's symbol. 



[V) T>AEYEli has brought forward, as an argument 

 -D against Ladenburg's symbol, the fact that dihy- 

 droxyterephthalic ether (a benzene derivative) is converted 

 by nascent hydrogen into succino-succinic ether (a hexa- 

 methylene derivative) (Ber. xix. p. 1797). 



A. K. Miller and Ladenburg have each shown his deduction 

 to be faulty (J. C. S. 1887, p. 209). (Without a single ex- 

 ception the facts quoted by these chemists can be as well 

 explained by the symbol of Claus as by that of Kekule.) 



It would indeed be a serious objection to Ladenburg's 

 symbol could it be shown that on hydrogenation the para- 

 linkages are successively split. We should thus expect to get 

 two trimethylene rings. Facts are in opposition to such a 

 supposition. 



But this is not the only conceivable way in which the 

 reaction may occur. A hexamethylene ring may be formed 

 by the dissolution of one para- and two meta-linkages, the 

 atoms being supposed to open out into a hexagonal ring 

 (vide supra, p. 405). It is perhaps improbable that a stable 

 meta-linkage (corresponding to ortho -linkage in Thomson's 

 symbol) would be severed in favour of a much weaker 

 para-linkage. The fact, however, remains that the additive 

 compounds can be so derived. The hexamethylene ring so 

 obtained will differ from that derived from Thomsen's sym- 

 bol in this respect — that the order of the six atoms will not 

 be the same. This is evident from the following diagrams: — 



Thomsen's \ 

 symbol, j 



will give 



