Anodic Oxidation Pathways of Carbazoles

Abstract

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.

One-electron photooxidation of carbazole in the presence of carbon tetrachloride. Part II. Carbon tetrachloride as a reaction medium. Use of ammonia after irradiation and during irradiation

“…The same principle of transformation for the radical cation of carbazole has been observed in the studies of electrochemical oxidation of carbazole (27). Similarly, the photolysis products of N-acetyl carbazole, being formed as a result of the reactions of carbazyl and acetyl radicals in the solvent cage (28), as well as the thermal rearrangement products of N,N1-dicarbazyl (29), strongly support the mechanism discussed for the reactions between the pair of radicals P and CCl,.…”

“…In this case N,Nf-dicarbazyl (23) For personal use only. the following compounds: 3,9-di-(N-carbazy1)car-carbazole-CC1, system according to the following: bazole (24), N-cyano-3-(N-carbazy1)carbazole (26), and 3-(N-carbazy1)carbazole (27) in addition ['I C + hv + 'C* to products 1, 3, 22,28, and 29 (second column in [2] 'c* + cCI, -1(C~+.CCI,6-)*s,l, Table 1). [3] l(c6+ ~~.cC1,6-)*,,,, -[ c + ' c1-CCI,],,~, All the isolated and identified products, using ammonia after and during irradiation, support the carbazole radical cation transformation mechanism that we proposed in part I (15).…”

One-electron photooxidation of N-ethylcarbazole in the presence of carbon tetrachloride. Products and mechanism of the photochemical reaction

“…[16]). Similar reaction in the tion of the cation a, in the reaction media studied here seems trialkylamine-polyhalomethane system (14) has been thorhighly probable. Nevertheless this will obviously require furoughly studied.…”

“…It is in good agreement with the charge density redistribution in the aromatic system. Indeed, theoretical calculations of the n electronic charge density in the carbazole molecule (8,13,14) show that the 1, 3, 6, 8, and 9 (N) positions are most favored.…”

“…Most of these investigations were correlated with the reactions (6)(7)(8) have been the object of extensive studies in theoretical calculations which have been carried out in order to describe the ground and excited electronic states of carbazole '~u t h o r to whom correspondence may be addressed. (9,(13)(14)(15) and N-alkyl derivatives of carbazole (1 1,16 Carbazole and its derivatives, like other aromatic amines in panied by the heterolytic dissociation of a C-Cl bond in CCl,. the presence of strong organic electron acceptors such as tetracyanoethylene, tetracyanoquinodimethane, 2,3-dichloro-5,6-dicyano-p-benzoquinone, trinitro and tetranitrofluorenones, p-chloranil, etc., form charge transfer (CT) complexes (17)(18)(19)(20)(21)(22) with new asymmetric absorption bands in the visible region of the spectrum.…”