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

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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Mechanism of L-ascorbic acid oxidation on a mercury electrode. II. Basic medium

Canadian Journal of Chemistry ◽

10.1139/v78-248 ◽

1978 ◽

Vol 56 (11) ◽

pp. 1533-1537 ◽

Cited By ~ 42

Author(s):

Juan José Ruiz ◽

Antonio Aldaz ◽

Manuel Dominguez

Keyword(s):

Electron Transfer ◽

Ascorbic Acid ◽

Mercury Electrode ◽

Oxidation Mechanism ◽

Limiting Current ◽

Basic Medium ◽

Acid Oxidation ◽

Acid Media ◽

Rate Determining Step ◽

Reaction Orders

A polarographic study of the oxidation mechanism of L-ascorbic acid is carried out in a basic medium and two oxidation waves are observed.An analysis of these waves shows that the limiting current is governed by diffusion and that in each reaction a two electron transfer takes place. On the rising portion of the waves, the oxidation process consists of two consecutive one electron transfers. In the first wave, the second transfer is the rate determining step, whilst in the second wave, a chemical stage subsequent to the second electron transfer is the rate determining step. The reaction orders, together with the Tafel slopes, are calculated.The oxidation mechanism of this acid in basic media is different from that in acid media.

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Mechanism of L-ascorbic acid oxidation and dehydro-L-ascorbic acid reduction on a mercury electrode. I. Acid medium

Canadian Journal of Chemistry ◽

10.1139/v77-389 ◽

1977 ◽

Vol 55 (15) ◽

pp. 2799-2806 ◽

Cited By ~ 97

Author(s):

Juan José Ruiz ◽

Antonio Aldaz ◽

Manuel Dominguez

Keyword(s):

Electron Transfer ◽

Ascorbic Acid ◽

Oxidation Process ◽

Mercury Electrode ◽

Oxidation Mechanism ◽

Limiting Current ◽

Acid Oxidation ◽

Rate Determining Step ◽

Reaction Orders ◽

Electron Transfers

A polarographic study of the oxidation mechanism of L-ascorbic acid and of the reduction mechanism of dehydro-L-ascorbic acid was carried out in an acid medium.For L-ascorbic acid, the oxidation process involves a two electron transfer and obeys the overall reaction[Formula: see text]The polarographic curve shows that the limiting current is governed by diffusion. On the rising portion of the wave, the two electron oxidation process consists of two consecutive one electron transfers, the second being the rate determining step (rds). The reaction orders, together with the Tafel slopes, were calculated.The reduction of dehydro-L-ascorbic acid at the limiting current is kinetically controlled and involves a two electron transfer. The reaction kinetic pathways were studied and the reaction orders and Tafel slope were calculated. It is deduced that, for low overvoltages, the second one electron transfer is the rate determining step.

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Three dimensional band-filling control of complex oxides triggered by interfacial electron transfer

Nature Communications ◽

10.1038/s41467-021-22790-0 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Meng Meng ◽

Yuanwei Sun ◽

Yuehui Li ◽

Qichang An ◽

Zhenzhen Wang ◽

...

Keyword(s):

Electron Transfer ◽

Field Effect ◽

Essential Role ◽

Field Effect Transistors ◽

Three Dimensional ◽

Complex Oxides ◽

Band Filling ◽

Local Lattice ◽

Oxygen Migration ◽

Oxide Heterostructure

AbstractThe d-band-filling of transition metals in complex oxides plays an essential role in determining their structural, electronic and magnetic properties. Traditionally, at the oxide heterointerface, band-filling control has been achieved via electrostatic modification in the structure of field-effect transistors or electron transfer, which is limited to the quasi-two-dimension at the interface. Here we report a three-dimensional (3D) band-filling control by changing the local lattice coordination in a designed oxide heterostructure. At the LaCoO3/LaTiO3 heterointerface, due to the Fermi level mismatch, electrons transfer from LaTiO3 to LaCoO3. This triggers destabilisation of the CoO6 octahedrons, i.e. the formation of lattice configurations with a reduced Co valence. The associated oxygen migration results in the 3D topotactic phase transition of LaCoO3. Tuned by the thickness of LaTiO3, different crystalline phases and band-fillings of Co occur, leading to the emergence of different magnetic ground states.

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Single entity electrochemistry and the electron transfer kinetics of hydrazine oxidation

Nano Research ◽

10.1007/s12274-021-3353-8 ◽

2021 ◽

Cited By ~ 1

Author(s):

Ruiyang Miao ◽

Lidong Shao ◽

Richard G. Compton

Keyword(s):

Electron Transfer ◽

Bulk Solution ◽

Relative Contribution ◽

Rate Determining Step ◽

Multistep Process ◽

Ph Range ◽

Electro Catalytic Oxidation ◽

Single Particle Impact ◽

The Impact ◽

Kinetics Of

AbstractThe mechanism and kinetics of the electro-catalytic oxidation of hydrazine by graphene oxide platelets randomly decorated with palladium nanoparticles are deduced using single particle impact electrochemical measurements in buffered aqueous solutions across the pH range 2–11. Both hydrazine, N2H4, and protonated hydrazine N2H5+ are shown to be electroactive following Butler-Volmer kinetics, of which the relative contribution is strongly pH-dependent. The negligible interconversion between N2H4 and N2H5+ due to the sufficiently short timescale of the impact voltammetry, allows the analysis of the two electron transfer rates from impact signals thus reflecting the composition of the bulk solution at the pH in question. In this way the rate determining step in the oxidation of each specie is deduced to be a one electron step in which no protons are released and so likely corresponds to the initial formation of a very short-lived radical cation either in solution or adsorbed on the platelet. Overall the work establishes a generic method for the elucidation of the rate determining electron transfer in a multistep process free from any complexity imposed by preceding or following chemical reactions which occur on the timescale of conventional voltammetry.

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The dehydrogenation of 1,4-dihydronaphthalene by tetrachloro-p-benzoquinone

Canadian Journal of Chemistry ◽

10.1139/v76-321 ◽

1976 ◽

Vol 54 (14) ◽

pp. 2261-2265 ◽

Cited By ~ 9

Author(s):

Z. M. Hashish ◽

I. M. Hoodless

Keyword(s):

Electron Transfer ◽

Charge Transfer ◽

Reaction Rate ◽

Second Order ◽

Charge Transfer Complexes ◽

Ion Transfer ◽

Hydride Ion ◽

Rate Determining Step ◽

Hydride Ion Transfer

The dehydrogenation of 1,4-dihydronaphthalene by tetrachloro-p-benzoquinone in phenetole solution has been investigated. The present work does not fully confirm earlier studies which report that the reaction follows second-order kinetics and that the hydride ion transfer is rate determining. In the investigations described in this paper second-order kinetics are only observed in the later stages of the reaction and a 1:1 stoichiometry of the reactants in the process is not obtained. Substitution of tritium in the 1,4-positions of the hydrocarbon appears to not significantly affect the reaction rate. The present results indicate that charge-transfer complexes are formed in the reaction and it is suggested that electron transfer within these complexes could be the rate-determining step in the dehydrogenation.

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Quantitative Voltammetry in Weakly Supported Media. Two Electron Transfer, Chronoamperometry of Electrodeposition and Stripping for Cadmium at Microhemispherical Mercury Electrodes

The Journal of Physical Chemistry C ◽

10.1021/jp9047314 ◽

2009 ◽

Vol 113 (34) ◽

pp. 15320-15325 ◽

Cited By ~ 11

Author(s):

Juan G. Limon-Petersen ◽

Edmund J. F. Dickinson ◽

Neil V. Rees ◽

Richard G. Compton

Keyword(s):

Electron Transfer ◽

Mercury Electrodes

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The effects of the chemical environment of menaquinones in lipid monolayers on mercury electrodes on the thermodynamics and kinetics of their electrochemistry

European Biophysics Journal ◽

10.1007/s00249-021-01512-w ◽

2021 ◽

Author(s):

Karuppasamy Dharmaraj ◽

Dirk Dattler ◽

Heike Kahlert ◽

Uwe Lendeckel ◽

Felix Nagel ◽

...

Keyword(s):

Electron Transfer ◽

Rate Constants ◽

Transfer Rate ◽

Chemical Environment ◽

Lipid Monolayers ◽

Redox Potentials ◽

Electron Transfer Rate ◽

Thermodynamics And Kinetics ◽

Mercury Electrodes ◽

Kinetics Of

AbstractThe effects of the chemical environment of menaquinones (all-trans MK-4 and all-trans MK-7) incorporated in lipid monolayers on mercury electrodes have been studied with respect to the thermodynamics and kinetics of their electrochemistry. The chemical environment relates to the composition of lipid films as well as the adjacent aqueous phase. It could be shown that the addition of all-trans MK-4 to TMCL does not change the phase transition temperatures of TMCL. In case of DMPC monolayers, the presence of cholesterol has no effect on the thermodynamics (formal redox potentials) of all-trans MK-7, but the kinetics are affected. Addition of an inert electrolyte (sodium perchlorate; change of ionic strength) to the aqueous phase shifts the redox potentials of all-trans MK-7 only slightly. The formal redox potentials of all-trans MK-4 were determined in TMCL and nCL monolayers and found to be higher in nCL monolayers than in TMCL monolayers. The apparent electron transfer rate constants, transfer coefficients and activation energies of all-trans MK-4 in cardiolipins have been also determined. Most surprisingly, the apparent electron transfer rate constants of all-trans MK-4 exhibit an opposite pH dependence for TMCL and nCL films: the rate constants increase in TMCL films with increasing pH, but in nCL films they increase with decreasing pH. This study is a contribution to understand environmental effects on the redox properties of membrane bond redox systems. Graphical abstract

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Sub- and super-Nernstian Tafel slopes can result from reversible electron transfer coupled to either preceding or following chemical reaction

Journal of Electroanalytical Chemistry ◽

10.1016/j.jelechem.2020.114942 ◽

2021 ◽

Vol 880 ◽

pp. 114942

Author(s):

Haotian Chen ◽

Richard G. Compton

Keyword(s):

Electron Transfer ◽

Chemical Reaction ◽

Reversible Electron Transfer ◽

Tafel Slopes

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Understanding the reaction mechanism of Kolbe electrolysis on Pt anodes

10.33774/chemrxiv-2021-3n07b ◽

2021 ◽

Author(s):

Sihang Liu ◽

Nitish Govindarajan ◽

Hector Prats ◽

Karen Chan

Keyword(s):

Reaction Mechanism ◽

Potential Range ◽

Microkinetic Model ◽

Rate Determining Step ◽

Rate Limiting Step ◽

Limiting Step ◽

Tafel Slopes ◽

Kolbe Electrolysis ◽

Kolbe Reaction ◽

Rate Limiting

Kolbe electrolysis has been proposed an efficient electrooxidation process to synthesize (un)symmetrical dimers from biomass-based carboxylic acids. However, the reaction mechanism of Kolbe electrolysis remains controversial. In this work, we develop a DFT- based microkinetic model to study the reaction mechanism of Kolbe electrolysis of acetic acid (CH3COOH) on both pristine and partially oxidized Pt anodes. We show that the shift in the rate-determining step of oxygen evolution reaction (OER) on Pt(111)@α-PtO2 surface from OH* formation to H2O adsorption gives rise to the large Tafel slopes, i.e., the inflection zones, observed at high anodic potentials in experiments on Pt anodes. The activity passivation as a result of the inflection zone is further exacerbated in the presence of Kolbe species (i.e., CH3COO* and CH3*). Our simulations find the CH3COO* decarboxylation and CH3* dimerization steps determine the activity of Kolbe reaction during inflection zone. In contrast to the Pt(111)@α-PtO2 surface, Pt(111) shows no activity towards Kolbe products as the CH3COO* decarboxylation step is limiting throughout the considered potential range. This work resolves major controversies in the mechanistic analyses of Kolbe electrolysis on Pt anodes: the origin of the inflection zone, and the identity of the rate limiting step.

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