590 SCIENCE PROGRESS 



Gattermann, Elbs, Haber, Haussermann, Lob, and others. All 

 these investigators paid special attention to the electro-reduction 

 of the nitro- (NO2) group in aromatic compounds — in particular 

 nitrobenzene — both as a preparative method and also from a 

 purely physical standpoint. 



The first experiments on electro-reduction (as well as electro- 

 oxidation) of organic substances were made between 1875 and 

 1886 b}' Goppelsroeder,^ who worked on the production and 

 bleaching of dyestuffs by means of electrolytically produced 

 h3'drogen and oxygen. From aniline sulphate by electro- 

 oxidation Goppelsroeder obtained aniline-black, while potas- 

 sium thioc3'anate on electrol3'tic reduction 3'ielded the dye 

 canarin. 



More important, both practically and theoretically, was the 

 work of Gattermann on the electro-reduction of nitrobenzene 

 and its derivatives. The chemical reduction of this substance 

 yields, according to the reducing agent employed, azoxybenzene, 

 azobenzene, hydrazobenzene, aniline, and benzidine. All of 

 these products ma}^ also be obtained with the help of the 

 electric current, variations in the conditions of electrolysis 

 corresponding, as noted above, to the use of different chemical 

 reducing agents.^ 



Gattermann,^ however, and independently Clement and 

 Noyes,* succeeded in obtaining an electro-reduction product 

 of nitrobenzene, which all chemical agents had failed to yield, 

 viz. para-amido-phenol. As an intermediate product phenyl- 

 hydroxylamine is formed, subsequently undergoing transfor- 

 mation to amido-phenol, thus : 



NOo NHOH NH, 



H H OH 



Nitrobenzene. Phenyl-hydroxylamine. Amidophenol. 



Corresponding amidophenols were obtained under similar 

 conditions from other aromatic nitro-compounds, such as nitro- 

 toluene, dinitrobenzenes, etc. When nitrobenzene is reduced 



1 Oesterreich's Wollen ufid Leinen Industrie^ Reichenberg, 1885. 



* See scheme on p. 592. 



' Ber. der. deui. chem. Gesell. 26 (1893), 1849. 



* Ibid. 990. 



