ORGANIC CHEMISTRY 



19 



if one quinaldine residue is the source. Further oxidation 

 with alkahne ferricyanide of the residue after removal of this 

 compound gave i-ethyl-2 — quinolone [XV] in quantities which 

 indicated that it must be derived from the remaining part of 

 the molecule. 



O 



CO2H 

 NEt . NO2 

 [XIV] 



NEt 

 [XV] 



CH :C 

 NEtX 

 [XVI] 



The smoothness and ease of the oxidation with nitric acid 

 suggests that the quinaldine residue which gives the quinal- 

 dinic acid ethyl nitrate is attached to the rest of the molecule by 

 a double bond, and it is inferred that the carbocyanine contains 

 the grouping [XVI]. 



It is suggested that the mechanism of the reaction is as 

 follows : 



+ CH2O + 



CH. 



CH3 

 NEtl 



CH, • CH, • CH, 



NEtl 

 + HaO-s. 



NEtl 



NEtl 



: CH • CH2 • CH2 



NEt NEtl 



[XVII] 



+ HI-> 



: CH • CH : CH 

 NEt NEtl 



It is not considered possible for a compound of the struc- 

 ture [XVII] to be as strongly coloured as pinacyanol, and the 

 oxidation with nitric acid suggests the presence of the ethylene 

 linking. The formation of pinacyanol therefore involves 

 oxidation or dehydrogenation, and it is suggested that the 

 greater yields obtained by bringing about the condensation in 

 the presence of quinoline ethiodide may be due to this substance 

 giving rise to compounds which serve to take up hydrogen. 

 It may be suggested that the quinoline ethiodide condenses 



