408 



Mr. S. A. Sworn on the Constitution 



linkage can be broken and again set up in such a manner. 

 The formation of anthracene from benzene and acetylene 

 tetrabromide does not prove that the paraffinoid residue 

 (C 2 H 2 ) IV exists as such in the anthracene molecule, any more 

 than Berthelot's synthesis of benzene from acetylene shows 

 that there are three such residues in benzene. The aggrega- 

 tion of other atoms to this residue causes it to assume the 

 most stable configuration, viz. that of two para-carbon 

 atoms in the aromatic nucleus. 



A direct proof of the aromatic nature of the central ring in 

 anthracene is wanting. The sulphonic radical, when intro- 

 duced by the direct action of sulphuric acid, invariably 

 attaches itself to one of the external nuclei. The naphthalene 

 derivatives, which we might expect to be the immediate pro- 

 ducts of the oxidation of anthracene, are at once further 

 oxidized (Beilstein, Handb. der org. Chemie, ii. p. 188). It 

 should be noticed that a proof of the contrary view would be 

 no argument against para-linkage because di-phenylene ethane 

 can be as well represented by Claus' as by Kekule's symbol. 

 It has, however, been shown (Graebe and Caro, Ber. xiii. 

 p. 99) that acridine (the analogue of anthracene) is oxidized 

 to a quinoline derivative, thus : — 





CH 





CH 



* 



CH 



CH 



CH 



















CH 



CH 



CH 



gives 



CH CH 



CH 



N CH. 



Acridine. 



C.COOH 



C.COOH 



Pyr. a-/3-quinoline dicarboxylic acid. 



This reaction shows that the central ring (B) of the acridine 

 molecule is a pyridine nucleus. By analogy it may be con- 

 cluded that the central ring in anthracene is of a benzenoid 

 nature. If this be admitted it follows, from the proved 

 existence of a single linkage in this ring, that the benzene 

 molecule must have one and therefore three such linkages. 



(2) Bamberger and Philip have shown pyrene to consist of 

 four benzene nuclei A, B, C, D, conjugated as in the diagram 

 (Ber. xx. p. 365). These chemists give the following formulas 

 for pyrene and its quinone : — 



