Coulometry in resonator cavity of EPR spectrometer: Electrochemical oxidation of carbazole methyl derivatives

1981 ◽  
Vol 46 (1) ◽  
pp. 40-47 ◽  
Author(s):  
Pavel Kubáček
Keyword(s):  
Electrochemical Reduction ◽  
Electrochemical Oxidation ◽  
Electrode Surface ◽  
Cation Radical ◽  
Radical Product ◽  
Spin Concentration ◽  
Resonator Cavity ◽  
Methyl Derivatives ◽  
Simultaneous Measuring ◽  
Radical Character

Electrochemical reduction of carbazole, 3-methyl- and 3,9-dimethylcarbazole in acetonitrile leads to the formation of a layer of conductive, insoluble products on the electrode surface of a partially radical character. This phenomenon was studied by coulometry in the resonator cavity of an EPR spectrometer with simultaneous measuring of the spin concentration. With carbazole and 3-methylcarbazole, the radical particles are formed with a yield of about 2% with respect to the current passed, whereas with 3,9-dimethylcarbazole this yield is by an order or magnitude lower. The radical product adsorbed on the electrode is probably a sparingly soluble perchlorate of the cation radical of 3,3'- or 6,6'-bicarbazole. 3,6,9-Trimethylcarbazole gives on oxidation a relatively stable primary cation radical. Electrochemical oxidation of 9-methyl- and 3,6-dimethylcarbazole does not lead to radical products.

Features of electrochemical reduction of silk fibroin in the presence of phosphate tricalcium in the form of nanocating

2021 ◽  
pp. 2150476
Author(s):  
Khakkulov Jakhongir Mardonovich ◽  
Kholmuminov Abdufatto Akhatovich ◽  
Temirov Zokir Shukurulloevich
Keyword(s):  
Shear Flow ◽  
Electrochemical Reduction ◽  
Silk Fibroin ◽  
Tricalcium Phosphate ◽  
Electrode Surface ◽  
Newtonian Flow ◽  
Phosphate Ions

The possibilities of movement and electrochemical reduction of fibroin macroions in the presence of tricalcium phosphate ions in the form of a nanocoating during electrolysis have been studied. The manifestation of a non-Newtonian flow of a mixture of macroions and ions in a shear flow, the conditions for their electrochemical reduction in the form of a nanocoating with uniform morphology, and thickness on the electrode surface are revealed. It was found that the excess ions in the mixture and the uneven relief of the electrode surface contribute to the formation of a nanocoating with an inhomogeneous and uneven thickness.

Chemical and electrochemical oxidation of phenothiazine

1993 ◽  
Vol 71 (5) ◽  
pp. 674-677 ◽  
Author(s):  
Alexei N. Pankratov ◽  
Inna M. Uchaeva ◽  
Alexander N. Stepanov
Keyword(s):  
Electrochemical Oxidation ◽  
Sulphuric Acid ◽  
Quantum Chemical ◽  
Oxidation Reaction ◽  
Cation Radical ◽  
Rotating Disk ◽  
Rotating Disk Electrode ◽  
Disk Electrode ◽  
Diffusion Controlled ◽  
Voltammetric Technique

The oxidation of phenothiazine in dilute solutions of sulphuric acid leads to the corresponding cation radical. Using a potentiometric technique, a pKa 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 one-electron diffusion-controlled process. A quantum chemical explanation was found for the direction of phenothiazine protonation and the absence of a dimerization stage of oxidation.

scholarly journals Surface Electrochemistry of Uranium Dioxide in Acidic Hydrogen Peroxide Solutions

2012 ◽  
Vol 1475 ◽  
Author(s):  
Mayuri Razdan ◽  
David Hall ◽  
David W. Shoesmith
Keyword(s):  
Hydrogen Peroxide ◽  
Surface Layer ◽  
Electrochemical Reduction ◽  
Surface Diffusion ◽  
Uranium Dioxide ◽  
Electrode Surface ◽  
Surface Electrochemistry ◽  
Ph Range ◽  
Acidic Hydrogen

ABSTRACTThe electrochemical reduction of H2O2 on SIMFUEL was investigated over the pH range 1 to 4. The mechanism at pH 4 is known to occur on UV species incorporated into a surface layer of UIV1-2xUV2xO2+x. However, below pH 3, reduction occurs on an adsorbed UVO2(OH) state which is unstable and oxidizes to insulating UVI before dissolving as UO22+. Both schemes are observed at intermediate pH’s. The presence of both low and high acidic regions at the electrode surface is determined by the combination of peroxide concentration, bulk pH and the surface diffusion conditions.

Electrochemical and biological oxidation of 1,4-dihydropyridine derivatives

1981 ◽  
Vol 46 (5) ◽  
pp. 1141-1147 ◽  
Author(s):  
Antonín Kurfürst ◽  
Jiří Ludvík ◽  
Pavel Rauch ◽  
Miroslav Marek
Keyword(s):  
Electrochemical Reduction ◽  
Nitro Group ◽  
Electrochemical Oxidation ◽  
Respiratory Chain ◽  
Enzyme System ◽  
Biological Oxidation ◽  
Common Trends ◽  
Cyclic Voltametry ◽  
Dihydropyridine Derivatives

Electrochemical oxidation of 1,4-dihydropyridines I-XII and electrochemical reduction of the nitro group of 4-(2-nitrophenyl)-1,4-dihydropyridines III, VI, IX and XII was studied using cyclic voltametry. When comparing the electrochemical and the biological oxidation of 3,5-dimethoxycarbonyl-2,6-dimethyl-4-(2-nitrophenyl)-1,4-dihydropyridine (IX, Nifedipine) and related 1,4-dihydropyridines it was found that in spite of certain common trends the oxidation of these compounds (I-XII) in the organism cannot be predicted unambiguously. Of the substances tested compounds IX and XI (3,5-diethoxycarbonyl-4-phenyl-2,6-dimethyl-1,4-dihydropyridine) were the least oxidizable by the respiratory chain, and at the same time they did not inhibit this enzyme system. In addition to this, compound IX was the least oxidizable by the microsomal system.

Interfacial interactions between aqueous solutions of 4,4'-bipyridyl and mercury

1987 ◽  
Vol 52 (1) ◽  
pp. 54-65 ◽  
Author(s):  
Michael Heyrovský ◽  
Ladislav Novotný
Keyword(s):  
Charge Transfer ◽  
Acid Solution ◽  
Electrode Surface ◽  
Negative Charge ◽  
Cation Radical ◽  
Simultaneous Increase ◽  
Neutral Solution ◽  
Adsorbed State ◽  
Langmuir Coefficient ◽  
Drop Time

From analysis of electrocapillary curves obtained by drop-time measurements with spindle-type capillary and the method of controlled convection the data on reversible equilibrium adsorption of 4,4'-bipyridyl on mercury from aqueous 0·1M solutions of Na2SO4 and H2SO4 were obtained. In neutral solution 4,4'-bipyridyl is strongly adsorbed: at potential of maximum adsorption the Langmuir coefficient β = 1.4 . 102 m3 mol-1 and Γm = 1.8 . 10-6 mol m-2; in acid solution the adsorption of the doubly protonated 4,4'-bipyridylium cation is weaker and its potential dependence goes through a minimum. The increase of adsorption of the bipyridylium cation and a simultaneous increase of negative charge with increasing negative potential are explained by charge transfer in adsorbed state. The electroreduction of 4,4'-bipyridyl is preceded by formation at the electrode surface of a layer of sparingly soluble salt of the bipyridyl cation radical.

THE INVESTIGATION OF THE ELECTROOXIDATION OF SODIUM BOROHYDRIDE ON VARIOUS METAL ELECTRODES IN AQUEOUS BASIC SOLUTIONS

2018 ◽  
pp. 80-86
Author(s):  
H. Celikkan ◽  
M. Sahin ◽  
M. L. Aksu ◽  
T. N. Veziroğlu
Keyword(s):  
Catalytic Activity ◽  
Electrochemical Oxidation ◽  
Sodium Borohydride ◽  
Electrode Surface ◽  
Square Wave Voltammetry ◽  
Metal Electrodes ◽  
Square Wave ◽  
Wave Voltammetry ◽  
Basic Solutions ◽  
Electron Transfers

This study is related to the electrochemical oxidation of NaBH4 on Au, Pt, Pd and Ni electrodes by the use of cyclic and square wave voltammetry. The most effective metal for the oxidation of sodium borohydride was found to be Au. Pt and Pd electrodes also showed certain activity while Ni was not effective. The compound was observed to give two consecutive oxidation steps with 6 and 2 electron transfers. The experiments conducted while keeping the potential at −0.8V showed that the resulting compound is adsorbed upon the electrode surface and gradually decrease its catalytic activity.

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