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7757762 
Journal Article 
The electrochemical oxidation of 4-bromoaniline, 2,4-dibromoaniline, 2.4,6-tribromoaniline and 4-iodoaniline in acetonitrile solution 
Kadar, M; Nagy, Z; Karancsi, T; Farsang, G 
2001 
Yes 
Electrochimica Acta
ISSN: 0013-4686 
46 
22 
3405-3414 
English 
WOS:000170850900009 
The electrochemical oxidation of 4-bromo-, 2, 4-dibromo-, 2, 4, 6-tribromo- and 4-iodoanilines was investigated in acetonitrile solution. Based on the experimental results, it can be stated that the Bacon-Adams mechanism (J. Am. Chem. Soc. 90 (1968) 6596) is the main electrochemical oxidation route in acetonitrile solution similar to the 4-chloroanilines. In the cases of 4-bromo- and 2, 4-dibromoanilines, the substituent in the para position eliminated in the dimerisation step, following its oxidation to bromine, which quantitatively substitutes the free ortho position of the starting bromoaniline. As a consequence of this, oxidised form of brominated 4-amino-diphenylamines is formed besides brominated anilines. Halogenisation did not take place at the oxidation of 2, 4, 6-tribromo- and 4-iodoaniline because the rejected halide ion can only be oxidised to elemental halogen (bromine and iodine). In the case of all bromo monomer compounds, the role of 'head-to-head' coupling was found negligible (azobenzene type compounds). 4, 4′-Diiodo-azobenzene has been observed as by-product in traces at 4-iodoaniline oxidation. The electrochemical oxidation of 4-bromoaniline resulted in the 'ortho-coupling' product in a considerable less degree in contrast with 4-chloroaniline. The oxidation products prepared by controlled potential electrolysis (CPC) were isolated and identified by different techniques: GC-ECD (gas chromatography), GC-MS (gas chromatograph-mass spectrometry), and ES-MS (electrospray mass spectrometry). Cyclic voltammograms of the 4-halogenoaniline type substrates and n-tetrabutylammonium halides, have been recorded before and after the CPC electrolysis, and were also used for product identification. © 2001 Elsevier Science Ltd. All rights reserved. 
anilines; electrochemical oxidation; halogenisation