Electrochemical reduction and oxidation of the antibiotic cefepime at a carbon electrode

The O-methyl oxime grouping in the antibiotic cefepime is reduced in aqueous buffer solution at pH<8 at a carbon electrode. The reduction of the protonated form of the oxime occurs in a single two-electron step. By comparison with anodic wave of 2-aminothiazole it was furthermore shown that the oxidation of cefepime involves the 2-amino group located on the thiazole ring in the side chain on C-7. Both reduction and oxidation peaks can be used for analytical purposes.     

Electrochemical reduction and oxidation of fullerenopyrrolidines and the ESR spectra of paramagnetic intermediates

Electroreduction and electrooxidation of monosubstituted N-methyl[60]fullerenopyrrolidines were studied by cyclic voltammetry and potentiostatic microelectrolysis in the cavity of an ESR spectrometer. Stepwise reversible transfer of three electrons to the fullerenopyrrolidine molecule results in the formation of stable radical anions (according to ESR, g = 2.0000, H = 0.8 G), dianions, and radical trianions (according to ESR, g = 2.0015, H = 1.5 G). The reduction potentials vary over narrow limits depending on the nature of the substituents in the pyrrolidine fragment of the compounds. Electrooxidation is irreversible and occurs in either one or two steps. For compounds containing the aniline, indole, or phenol fragment, the first step is associated with oxidation of these fragments and only after that, is the fullerenopyrrolidine core oxidized. Oxidation of the pyrrolidine fragment is substantially more difficult than that of tertiary amines.     

Electrochemical reduction and oxidation signals of angiotensin peptides. Role of individual amino acid residues

Chronopotentiometric stripping (CPS) peak H in proteins is due to the catalytic hydrogen evolution reaction (CHER) involving amino acid residues. This peak is sensitive to changes in protein structures, representing a new tool in protein research. Here we show on the ground of studies of CPS behavior of four angiotensin peptides that at neutral pH arginine plays a critical role in CHER at Hg electrode, while participation of histidine residues in this reaction is very weak. At carbon electrode tyrosine residues produce an oxidation peak close to 0.7 V but the presence of histidine in angiotensins is not manifested by any oxidation peak.     

Electrochemical oxidation and reduction of rhodium and iridium complexes with fullerenes C60 and C70

The electrochemical behavior of rhodium and iridium complexes with fullerences C₆₀ and C₇₀ was studied by cyclic voltammetry in a THF—toluene mixture. The complexes were found to be capable of oxidation and reduction. It was demonstrated that thein situ generation of metallofullerene complexes in the electrochemical cell by the interaction of C₆₀ and C₇₀ with hydridocarbonylphosphine complexes of rhodium and iridium, HM(CO)(PPh₃)₃, is possible. The influence of structural factors and the action of CO₂ on changes in the redox properties of fullerene complexes was considered.     

Electrochemical reduction of cobalt and nickel complexes with ligands stabilizing metal in low oxidation state

Electrochemical reduction of cobalt(ii) complexes containing -acceptor ligands (L = bpy, Ph₂Ppy) proceeds through three consecutive reversible steps: one-electron transfer to form a more stable Co^IL complex, transfer of two electrons at more negative potentials to form an anionic [NiL]^– complex, and reduction of the ligand to the radical anion. The stability of the cobalt complexes with different ligands decreases in the series Ph₂Ppy > Ph₃P > bpy.     

Electrochemical oxidation of nitroylides

Conclusions The mechanisms of the electrochemical oxidation of mono- and dinitroylides of S and Se on a Pt electrode in CH₃CN have been studied for the first time. It was shown that the cation radical formed as intermediate was able to react with the medium with removal of an H atom and with the formation of an onium cation or to undergo decomposition. Competition of these processes determines the special features of the electrooxidation of mononitroylides, while on oxidation of dinitroylides the intermediate cation radical decomposed to oxides of nitrogen.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1332–1338, June, 1981.     

Electrochemical oxidation of aldoximes

Conclusions The electrochemical oxidation of aldoximes was found to proceed with the loss of one electron and formation of the corresponding iminoxyl radical, which undergoes subsequent chemical reactions more rapidly than undergoing oxidation on the electrode.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1687–1691, July, 1989.     

Electrochemical oxidation of N-p-toluenesulfinamides

[reaction: see text] Contrasting and interesting electrochemical behavior is observed in anodic oxidation of N-substituted p-toluenesulfinamides under controlled current conditions. For sulfinamides derived from secondary alkylamines and primary arylamines, the N-sulfinyl group is removed and the corresponding amines are formed; for sulfinamides derived from primary alkylamines, sulfur oxidation yields the corresponding sulfonamides in good yields.     

Electrochemical oxidation of ketoximes

Conclusions The oxidation of ketoximes on a platinum anode in acetonitrile proceeds through the intermediate formation of the corresponding radical-cation, iminoxyl radical, and oxoimmonium cation.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1683–1686, July, 1989.     

Electrochemical oxidation of phenols

Electrochemical oxidation of chlorinated phenols was studied.     

Electrochemical oxidation of methylenedioxyamphetamines

Four amphetamine derivatives bearing a methylenedioxy group at positions 3 and 4 of the benzene ring and differing in their substitution at C(6) were studied by differential pulse voltammetry in aqueous media. These experiments showed a single oxidation peak for the C(6)-H, -Br and -Cl compounds, while the C(6)-NO(2) analogue was not oxidized. The oxidation peak is interpreted as due to the removal of one electron from the aromatic electrophore with formation of a radical cation stabilized by the dioxole ring. The linear relationship between the peak current and the concentration of the derivatives is appropriate for development of a quantitative method for their determination. pK' values were determined using both electrochemical and spectrophotometric methods.     

Electrochemical oxidation of xanthosine

The electrochemical oxidation of xanthosine in aqueous solution at pH 2.0 at the pyrolytic graphite electrode has been studied. The primary electrochemical oxidation reaction is an irreversible 1 e⁻, 1 H⁺ reaction giving the C(8) free radical. In order to account for the ultimate products formed, the latter primary radical reacts with xanthosine to give at least one N free radical and with water to give an 8-hydroxylated free radical. The C(8) and N radicals couple to give a xanthosylxanthosine dimer which rapidly loses one ribosyl residue to give a xanthosylxanthine dimer. The 8-hydroxylated radical reacts with the C(8) and N radicals to give two isomeric hydroxylated xanthosylxanthosines. The 8-hydroxylated radical can also undergo further electrochemical oxidation (1 e⁻, 1 H⁺) to 9-β-D-ribofuranosyluric acid which is immediately oxidized (2 e⁻, 2 H⁺) to a very reactive quinonoid. Attack by water on the quinonoid gives two isomeric tertiary alcohol intermediates which have been isolated and characterized by their UV and mass spectra and by their reaction with water to give a diol. The latter diol decomposes to 5-hydroxyhydantoin-5-carboxamide-3-riboside.     

Electrochemical oxidation of selenocystine and selenomethionine

Electrochemical oxidation of selenocystine (SeCys) and selenomethionine (SeMet), on a gold electrode was studied by cyclic voltammetry (CV), rotating disk electrode technique (RDE) and chronocoulometry (CC). In 0.2 mol/L HAc-NaAc (pH = 3.90) supporting electrolyte, anodic peak I potential of SeCys and SeMet was 810 mV and 638 mV, respectively, and this electrode process was diffused controlled. The electrochemical oxidation process of SeCys, in which six electron-transfers were involved, yielded selenocystine selenoxide. The electrochemical oxidation process of SeMet, in which two electron-transfers were involved, yielded selemethionine selenoxide.     

Electrochemical reduction of nitrotetralones

The electrochemical reduction of three nitrotetralone derivatives by tast and differential pulse polarography and cyclic voltammetry in a wide pH range was studied. In aqueous media, the reduction of mono- and dinitrotetralone follows the general pattern of reduction of aromatic nitro compounds: the nitro group is reduced in a four-electron step to a hydroxylamine group. However, in mixed media this reduction differs from that of other nitrobenzenes, due to the fact that the formation of the nitroradical anion was not observed. The reduction of the acetoxy derivative was studied only at alkaline pH, because it suffered acid hydrolysis. The ionization pK of the protonatable groups were polarographically obtained.