of the Aromatic Nucleus. 415 



aceto-acetic ether on methyl-aniline, a reaction which can be 

 represented only as follows : — 



•NCH, 



NCH, 



,NIH ICH; 



/"r ; u£i 3 C6H 4 



CfiHs ! o4-c.cH 3 .=H 2 0-H J-'v 



\ 



C.CR 3 



I H-f-CH 



1 ' 

 • l I 



COOH 



Methyl- Aceto-acetic 

 aniline. ether. 



=2H 2 0+ c 6 h 4 



\ T 



OH-'-CO 



C.CH, 



CH 



CO 



Hypothetical 

 intermediate body. 



Methyl-y-oxyquinaldine 

 (lactam form). 



The formation of this body from y-oxyquinaldine necessi- 

 tates the change of the " lactim " into the " lactam form." 

 This change can be satisfactorily explained only on the 

 assumption that in 7-oxyquinaldine the nitrogen atom is 

 directly combined with the para- or 7-carbon atom. 



These researches, together with those of Ruhemann on 

 citrazinic acid (J. C. S. 1887, p. 403), and of Graebe and Caro 

 on acridine {Ber. xiii. p. 99), afford evidence of para-linkage 

 in the pyridine nucleus. 



Finally, I would point out that arguments in favour of one 

 para-linkage in benzene are equally strong in favour of three, 

 for in no other way can the necessary symmetry of the mole- 

 cule be maintained. Such a deduction would not be strictly 

 logical in the case of the pyridine compounds, but the only 

 alternative ormula — viz. one with olefmoid linkages, 



CH 



CH 



CH 



or 



N CH 



CH 



is scarcely a representation of the stability of pyridine. 

 [To be continued.] 



