Anodic Oxidation Pathways of Carbazoles

Electrochemical and spectroscopic techniques have been employed in elucidating the anodic oxidation pathways of carbazole and several N‐substituted derivatives. For carbazole and the N‐alkyl or N‐aryl derivatives, ring‐ring coupling is the predominant decay pathway of the carbazole cations; the coupling rates are extremely rapid. N‐N coupling is observed initially for carbazole, but in long‐time electrolysis it is of little consequence. The oxidation products have been synthesized by chemical means and compared with the species formed electrochemically by matching of cyclic polarograms and visible absorption spectra. Molecular orbital calculations give a qualitative picture of active sites with regard to follow‐up coupling reactions in the carbazole series. N‐vinyl, N‐acetyl, N‐benzoyl, and N‐nitroso carbazole were investigated briefly but found to be extremely complicated.