Chemical and electrochemical oxidation of phenothiazine

Abstract

ALEXEI N. PANKRATOV, INNA M. UCHAEVA, and ALEXANDER N. STEPANOV. Can. J. Chem. 71, 674 (1993) The oxidation of phenothiazine in dilute solutions of sulphuric acid leads to the corresponding cation radical. Using a potentiometric technique, a pK, value of 5.72 ? 0.05 was determined for phenothiazine. The kinetics has been studied and participation of both protonated and unprotonated oxidant in the oxidation reaction has been confirmed. Using a voltammetric technique with a rotating disk electrode, the anodic oxidation of phenothiazine was shown to be a oneelectron diffusion-controlled process. A quantum chemical explanation was found for the direction of phenothiazine protonation and the absence of a dimerization stage of oxidation.ALEXEI N. PANKRATOV, INNA M. UCHAEVA et ALEXANDER N. STEPANOV. Can. J . Chem. 71, 674 (1993) L'oxydation de la phknothiazine, en solutions dilukes d'acide sulfurique, conduit au cation radical. Faisant appel a une technique potentiomktrique, on a dttermink un pK, de 5,72 * 0,05 pour la phenothiazine. On a ktudi6 la cinttique de la reaction et on a dCmontr6 que l'oxydant proton6 aussi bien que le non proton6 participent a la r6action d'oxydation. Faisant appel a la technique de voltamp6romttrie avec une tlectrode a disque tournant, on a dCmontr6 que l'oxydation anodique est une rkaction impliquant un klectron dans un processus contr616 par la diffusion. On a expliquk la direction de la protonation de la phenothiazine et I'absence d'ktape de dimkrisation durant I'oxydation.[Traduit par la rkdaction]

Electrochemical preparation of a molecularly imprinted polypyrrole modified pencil graphite electrode for the determination of phenothiazine in model and real biological samples

“…Electrochemical oxidation of PTZ occurs with removal of one electron and formation of cation radical. PTZ cation radical is stable in acidic medium and unstable in neutral and weakly acidic solutions [48]. This behavior was subscribed by our results.…”

“…The first step is a reversible electron abstraction from the PTZ to the colored semi-quinone radical cation. The radical-cation is stable in a strongly acidic medium [48]. In the second step, the radical cation is irreversibly oxidized by loss of another electron and PTZ ion is created (not shown in Scheme 2).…”

Investigation of some biologically relevant redox reactions using electrochemical mass spectrometry interfaced by desorption electrospray ionization

“…It was proposed [33, 45, 46] that chlorpromazine can easily undergo oxidation in acid medium, in which a one e − oxidation process leads to the formation of a radical cation intermediate. It is known that, while the radical cation of phenothiazine is comparably stable, the radical cations of the substituted phenothiazines are believed to be unstable and could further react with solvent to give rise to sulfoxide [47]. Previously, Van Berkel et al reported the observation of radical cations of analytes including phenothiazine generated from the electrospray needle [48].…”

Overcharge performance of 3,7-disubstituted N-ethylphenothiazine derivatives in lithium-ion batteries

“…Aromatic amines such as triphenylamines and phenothiazines are subject to dimerization and oligomerization reactions in the radical cation state, which has been shown to occur most readily at the positions para to the nitrogen atoms. [21][22][23][24][25][26] Conveniently, these positions are the most reactive in electrophilic aromatic substitution reactions, making them easy to modify with a variety of substituents. Therefore, for this study, we synthesized 3,7-disubstituted derivatives of EPT in which substituents are incorporated at the positions para to the nitrogen atoms (Fig.…”