Electrochemical oxidation of squaric and croconic acids on Pt and Pt surfaces modified by underpotential heavy metal monolayers in acid solutions

1987 ◽  
Vol 65 (2) ◽  
pp. 397-403 ◽  
Author(s):  
D. Sazou ◽  
G. Kokkinidis
Keyword(s):  
Electrochemical Oxidation ◽  
Perchloric Acid ◽  
Electrochemical Behaviour ◽  
Sweep Rate ◽  
Hydration Reaction ◽  
Acid Solutions ◽  
Rotating Disc ◽  
Rate Determining Step ◽  
Controlled Potential ◽  
Reaction Orders

The electrochemical oxidation of squaric and croconic acids on platinum in aqueous perchloric acid solutions has been investigated by means of cyclic voltammetry, rotating disc electrode, potentiostatic transients and controlled-potential electrolysis. The kinetic parameters (Tafel slopes, reaction orders) have been determined on the foot of the wave by varying the sweep rate, the angular velocity, depolarizer concentration, and perchloric acid concentration. A probable mechanism has been proposed for the overall oxidation processes. It involves two charge-transfer steps followed by the desorption of product, which is the rate-determining step. The oxidation product is immediately deactivated by a rapid hydration reaction. Also, the effect of underpotential Tl, Pb, and Bi monolayers on the electrochemical behaviour of squaric and croconic acids has been examined.

scholarly journals Electrochemical oxidation of methanol on Pt3Co bulk alloy

2003 ◽  
Vol 68 (11) ◽  
pp. 859-870 ◽  
Author(s):  
Snezana Gojkovic
Keyword(s):  
Kinetic Parameters ◽  
Electrochemical Oxidation ◽  
Methanol Oxidation ◽  
Reaction Pathway ◽  
Acid Solutions ◽  
Bulk Alloy ◽  
Promoting Effect ◽  
Rate Determining Step ◽  
Oxidation Of Methanol ◽  
Reaction Orders

The electrochemical oxidation of methanol was investigated on a Pt3Co bulk alloy in acid solutions. Kinetic parameters such as transfer coefficient reaction orders with respect to methanol and H+ ions and energy of activation were determined. It was found that the rate of methanol oxidation is significantly diminished by rotation of the electrode. This effect was attributed to the diffusion of formaldehyde and formic acid from the electrode surface. Stirring of the electrolyte also influenced the kinetic parameters of the reaction. It was speculated that the predominant reaction pathway and rate determining step are different in the quiescent and in the stirred electrolyte. Cobalt did not show a promoting effect on the rate of methanol oxidation on the Pt3Co bulk alloy with respect to a pure Pt surface.

Electrochemical behaviour of galena (PbS) in aqueous nitric acid and perchloric acid solutions

2004 ◽  
Vol 34 (1) ◽  
pp. 37-46 ◽  
Author(s):  
Yu. Mikhlin ◽  
A. Kuklinskiy ◽  
E. Mikhlina ◽  
V. Kargin ◽  
I. Asanov
Keyword(s):  
Nitric Acid ◽  
Perchloric Acid ◽  
Electrochemical Behaviour ◽  
Acid Solutions ◽  
Aqueous Nitric Acid

The Oxidation of Tetrahydrofuran by Ruthenium Tetroxide

1972 ◽  
Vol 50 (19) ◽  
pp. 3129-3134 ◽  
Author(s):  
Donald G. Lee ◽  
Matthijs Van Den Engh
Keyword(s):  
Perchloric Acid ◽  
Activation Parameters ◽  
Isotopic Labeling ◽  
Acid Solutions ◽  
Ruthenium Tetroxide ◽  
Rate Determining Step ◽  
Rate Of Reaction ◽  
Hydride Abstraction ◽  
Aqueous Perchloric Acid ◽  
Kinetics Of

The kinetics of the oxidation of tetrahydrofuran by ruthenium tetroxide in aqueous perchloric acid solutions have been investigated. The rate of reaction is found to be directly dependent on the concentrations of oxidant and reductant, but inversely dependent on the acidity of the medium. A mechanism involving hydride abstraction in the rate determining step was found to be consistent with the evidence obtained from isotopic labeling and an analysis of the activation parameters (ΔH≠ = 14.0 kcal/mol, ΔS≠ = −18.4 e.u.) of the reaction. This conclusion is further substantiated by noting the similarity between the reactions of ruthenium tetroxide with alcohols and ethers.

The Oxidation of 2-Propanol by Ruthenium Tetroxide

1972 ◽  
Vol 50 (13) ◽  
pp. 2000-2009 ◽  
Author(s):  
Donald G. Lee ◽  
Matthijs van den Engh
Keyword(s):  
Perchloric Acid ◽  
Acid Solutions ◽  
Ruthenium Tetroxide ◽  
High Acid ◽  
Rate Determining Step ◽  
Carbonium Ion ◽  
Hydride Abstraction ◽  
Aqueous Perchloric Acid ◽  
Kinetics Of ◽  
Very High

The kinetics of the oxidation of 2-propanol by ruthenium tetroxide in aqueous perchloric acid solutions have been investigated. The results indicate that the two mechanisms pertain; at moderate acidities (1–6.5 M HClO4) the rate determining step involves hydride abstraction while at very high acid concentrations the rate determining step becomes carbonium ion formation.

Mécanisme des réactions du chlorite et du dioxyde de chlore. 1. Stoechiométrie des réactions du chlorite et cinétique en présence d'ortho-tolidine

1981 ◽  
Vol 59 (8) ◽  
pp. 1177-1187 ◽  
Author(s):  
Guy Schmitz ◽  
Henri Rooze
Keyword(s):  
Chlorine Dioxide ◽  
Perchloric Acid ◽  
Hypochlorous Acid ◽  
Chloride Ions ◽  
Sodium Chlorite ◽  
Kinetic Investigation ◽  
Acid Solutions ◽  
Fast Reaction ◽  
Rate Determining Step ◽  
Chlorous Acid

The relative amount of chlorine dioxide produced by the disproportionation of sodium chlorite increases as the concentrations of chlorite and chloride ions increase. It passes through a minimum when the concentration of perchloric acid varies from 2 M to 0.01 M. The fast reaction between chlorite and hypochlorous acid is a part of the mechanism of this disproportionation and its stoichiometry was also investigated. The relative amount of chlorine dioxide produced depends on the method of mixing the reactants and on the acidity. It increases if the concentration of chlorite increases and can exceed the amount predicted by:[Formula: see text]Ortho-tolidine reacts very rapidly with chlorine and with chlorine dioxide but not with chlorous acid. In perchloric acid solutions (pH < 2.5) the product of its oxidation has a considerable absorption with a maximum at 440 nm (ε = 59700 M−1 cm−1). Chlorine reacts more rapidly with ortho-tolidine than with chlorous acid. The kinetic investigation of the disproportionation of chlorous acid is thus simplified by the use of ortho-tolidine. With added chloride ions the rate determining step is HClO2 + Cl− + H+ → 2HClO with a rate constant[Formula: see text]The most reliable values for the free enthalpy of formation of oxychlorine compounds are selected from the literature.

The electrochemical oxidation of gold telluride (AuTe2) in perchloric acid solutions

1996 ◽  
Vol 41 (6) ◽  
pp. 879-885 ◽  
Author(s):  
S. Jayasekera ◽  
J. Avraamides ◽  
I.M. Ritchie
Keyword(s):  
Electrochemical Oxidation ◽  
Perchloric Acid ◽  
Acid Solutions ◽  
Gold Telluride

Properties of electrochemically generated primary cationradicals of phenyl- and 2-(4-tolyl)-1,3,4,7-tetramethylisoindoles

1980 ◽  
Vol 45 (6) ◽  
pp. 1669-1676 ◽  
Author(s):  
Pavel Kubáček
Keyword(s):  
Electrochemical Oxidation ◽  
Spin Polarization ◽  
High Spin ◽  
Epr Spectroscopy ◽  
Half Life ◽  
Electrochemical Behaviour ◽  
Epr Spectra ◽  
Electrochemical Generation ◽  
Splitting Constant ◽  
Reduced Temperature

The first step of electrochemical oxidation of 2-phenyl- and 2-(4-tolyl)-1,3,4,7-tetramethylisoindoles in anhydrous acetonitrile produces relatively stable cationradicals which have been studied by means of EPR spectroscopy using the method of internal electrochemical generation of radicals under reduced temperature. The same electrochemical behaviour of the both studied derivatives and identical EPR spectra of their cationradicals can be explained within the Huckel MO method. The largest contribution to the magnitude of splitting constant of nitrogen nucleus is due to π-σ-spin polarization of C-N bonds caused by high spin abundance of pz-AO of carbon atoms. Half-life of decomposition of the studied cationradicals is 4 min at -30°C.

Some Aspects of the Electroreduction of Niazid to Nicotinamide on Mercury Electrodes in Acidic Media

1992 ◽  
Vol 57 (9) ◽  
pp. 1836-1842 ◽  
Author(s):  
Rafael Marín Galvín ◽  
José Miguel Rodríguez Mellado
Keyword(s):  
Electron Transfer ◽  
Essential Role ◽  
Uv Spectroscopy ◽  
Acidic Media ◽  
Polarographic Wave ◽  
Rate Determining Step ◽  
Tafel Slopes ◽  
Reaction Orders ◽  
Mercury Electrodes ◽  
The Waves

The electroreduction of niazid on mercury electrodes has been studied in acidic media (pH < 6). Tafel slopes and reaction orders were obtained at potentials corresponding to the foot of the first polarographic wave. On the basis of both polarographic and voltammetric results it has been shown that the waves appearing at more negative potentials correspond to the reduction of nicotinamide. Protonation of niazid plays an essential role in its reduction and pK values of 1.4, 3.2 and 11.5 were obtained by UV spectroscopy. The process corresponding to the first wave is irreversible, being the second one-electron transfer the rate determining step. Above pH 4 the process is complex due to the overlapping of the waves caused by the occurrence of protonation reactions.

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