Cyclic Voltammetry of Two Analogue K-Group Vitamin Compounds in Dimethylsulfoxide

Abstract

The electrochemical reduction of two analogue K-group vitamin compounds, menadione and phthiocol, was studied by cyclic voltammetry in DMSO on glassy carbon electrodes. The reduction process of the more biologically active of these compounds (menadione), is associated with the formation of the semiquinone anion radical and the dianion. Two separated reversible one-electron peaks were observed. In contrast, the less biologically active phthiocol exhibits a single irreversible 2/3-electron peak which is explained by an ECE-DISP1 self-protonation mechanism. In the presence of a donor proton such as benzoic acid, menadione and phthiocol are reduced both through a sequence of consecutive electron transfer and protonation reactions occurring via an irreversible two-electron ECE-DISP1 mechanism.

Electrochemical and ESR study on the transformation processes of α-hydroxy-quinones

“…It is noticeable that upon the addition of base, a considerable amount of water is now present during the experiments (the TBAOH used is a 1 M aqueous solution). The stability of the ESR signals confirms that the added water behaves as a very weak proton donor in acetonitrile, as was previously described for DMSO [17].…”

“…Some authors propose that the reduction proceeds by a monoelectronic reduction of Q-O À , (Eq. (6)) [17][18][19].…”

Intra and intermolecular hydrogen bonding effects in the electrochemical reduction of α-phenolic-naphthoquinones

“…NQ is the reference quinone for this study [27,28]. In the particular case of the a-phenolic-naphthoquinones HNQ and H 2 NQ, it is observed that the chemical reversibility of the voltammetric waves is not lost by the effect of the presence of the a-phenolic groups, which allows us to discard the intervention of any self-protonation reaction [29,30]. Contrasting with this, the weak acidity of the a-phenolic protons accounts for the intervention of non-covalent interactions which provokes important differences in the redox potentials and current intensities.…”

Correlation of voltammetric behavior of α-hydroxy and α-methoxy quinones with the change of acidity level in acetonitrile

“…There is a controversy about the identification of the electrochemical process associated with the reduction of the conjugated base of the a-hydroxy quinones [22,32,44,49]. The in situ electronic spin resonance (ESR) results of the electrolysis of these quinones at the applied potential corresponding to the anion reduction process support a monoelectronic transfer in the reduction [50].…”