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.

Previous work had elucidated the anodic oxidation pathways of carbazole and several N‐substituted derivatives. These studies have now been extended to seventy‐six ring‐substituted carbazoles using electrochemical and spectroscopic techniques to study the reactivity of the various substituted carbazole cation radicals. Generally, it was found that 3, 6, and 9 (N) positions are extremely reactive; if these sites are not blocked by inert substituents the cation radicals generated by electrolytic oxidation react rapidly via coupling‐deprotonation. In some cases, substituents are eliminated from the 3 and 6 positions in the cation radicals followed by coupling to form substituted bicarbazyls. In other cases, relatively stable cation radicals were obtained and their EPR and visible absorption spectra were recorded. It was found that the reactivities of substituted carbazole cation radicals are considerably greater than those of analogous di‐ and triphenylaminium ions due to the planarity of the carbazole aromatic rings.

Enthalpy, entropy, and molar volume changes during the fusion process of a wide range of quaternary

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