An Investigation into the Electrochemical Oxidation of Some Aromatic Amines in the Room-Temperature Molten Salt System Aluminium Chloride-n-Butylpyridinium Chloride

Article abstract of DOI:10.1021/ja00533a021

The electrochemical oxidation of a number of aromatic amines in the low-temperature molten salt system aluminium chloride-N-butylpyridinium chloride has been investigated.In acidic melts TPA is oxidized reversibly to its radical cation which at more positive potentials undergoes a further, chemically irreversibly oxidation to the dication of the amine.In basic melts the stability of the radical cation is reduced and it couples to form tetraphenylbenzidine which is itself further oxidized.The oxidation of the other amines was more complex as a result of their being involved in complexation equilibria with acid species in the melt.In basic melts where they were uncomplexed, their behavior was similar to that of TPA, but, in acidic melts, the amine complexes underwent irreversible two-electron oxidations to their respective dications at potentials ca. 1 V positive of the first oxidation potential of the free amine.TMB, which, depending on the melt acidity, could be present as the free amine mono or di complex, was also oxidized to its dication.The actual mechanism of this oxidation was dependent upon the melt acidity.The oxidation of TMB was also shown to be dependent upon the temperature, the TMB cation radical being stable at low temperature but becoming unstable with respect to disproportionation as the temperature was increased.