196 SCIENCE PROGRESS 



Although on diazotisation and treatment with potassium 

 iodide they yield isomeric dinitro-diiodo-diphenyls where it is 

 necessary to use a cuprous salt or copper powder, while the 3:3'- 

 derivative gives the usual chloro-bromo-etc. compounds the 

 3:5' dinitrobenzidine gives derivatives of benzerythrene [IV] 



NO2 NOa 



(Br.CN)Cl (3~~vl} (Z}~~{Z) ^^(^^•^N') 



NO2 NO, 



[IV] 



An important confirmation of the existence of a new type 

 of isomerism in the diphenyl series is supplied by the work of 

 Kenner and Stubbings {Trans. Chem. Soc, 192 1, 119, 593). 

 The authors prefer not to decide at the moment between the 

 merits of the various possible formulae, but, for the sake of 

 comparison, Cain's notation will be adopted here. 



By the oxidation of a dinitrophenanthraquinone [V] Schulze 

 (Ann., 1880, 203, 95) obtained a dinitrodiphenic acid, of which 

 the orientation was established by Schmidt (Ber., 1903, 36. 3745) 

 as [VI] by conversion into 2 : 2'-dinitrodiphenyl and through 

 the diamino-compound [VII] into carbazole [VIII] 



^CO— COs^ COjH CO2H 



\. 



o 



NO2 NO2 NO2 NOj 



[V] [VI] 



NH2 NH2 NH 



[VII] [VIII] 



An attempt to synthesise the same acid by removal of 

 iodine by means of copper from two molecules of 2-iodo-3- 

 nitrobenzoic ester [IX] resulted in a new dinitro-diphenic 

 acid [X] which differs markedly from the acid obtained by 

 Schulze. On reduction Schulze's acid [VI] yields a diamino- 

 dicarboxylic acid in the usual way, but the new acid gives a 

 dilactam [XI], it being impossible to isolate the diamino-acid 



COgMe NO2 CO2H ^CO.NH^ 



o^ - o~o - o — 



NO2 CO2H NO, \ ^-" 



* NH.CO 



[IX] [X] [XI] 



