Faradaic Impedance Study of Mn(II) Reduction Mechanism in NaClO4 and NaCl Solutions on Mercury Electrode

The electrochemical reaction of the Mn(II)/Mn(Hg) system on mercury electrode was studied in 1 M NaClO4 and 1 M NaCl as supporting electrolytes of different complexing and adsorptive properties. The impedance measurements confirmed the two-stage electroreduction of the Mn(II) in investigated solutions. Both the apparent and the true rate constants of the second electron transfer in both supporting electrolytes are lower by one order of magnitude than the rate constant of the first electron transfer. Similar values of corrected rate constants in both electrolytes suggest the similarity in mechanism of the Mn(II) electroreduction.

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The Effect of p-Toluidine on the Two-Step Electroreduction of Zn(II) in Water-Methanol and Water-Dimethylformamide

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19990585 ◽

1999 ◽

Vol 64 (4) ◽

pp. 585-594 ◽

Cited By ~ 2

Author(s):

Barbara Marczewska

Keyword(s):

Electron Transfer ◽

Binary Mixtures ◽

Rate Constant ◽

Rate Constants ◽

Electrode Surface ◽

Mercury Electrode ◽

Forward Rate ◽

Solvent Molecules ◽

Activated Complex

The acceleration effect of p-toluidine on the electroreduction of Zn(II) on the mercury electrode surface in binary mixtures water-methanol and water-dimethylformamide is discussed. The obtained apparent and true forward rate constants of Zn(II) reduction indicate that the rate constant of the first electron transfer increases in the presence of p-toluidine. The acceleration effect may probably be accounted for by the concept of the formation on the mercury electrode an activated complex, presumably composed of p-toluidine and solvent molecules.

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Electrochemical reduction of the nickel(II) dithiocarbamates at the mercury electrode

Australian Journal of Chemistry ◽

10.1071/ch9761191 ◽

1976 ◽

Vol 29 (6) ◽

pp. 1191 ◽

Cited By ~ 9

Author(s):

TH Randle ◽

TJ Cardwell ◽

RJ Magee

Keyword(s):

Electron Transfer ◽

Chemical Reaction ◽

Mercury Electrode ◽

Electrode Reaction ◽

Reduction Mechanism ◽

Ece Mechanism ◽

Controlled Potential ◽

Nickel Species ◽

Electron Transfers ◽

Potential Conditions

The reduction mechanism of a series of nickel(11) dithiocarbamates has been investigated in dimethyl sulphoxide at the mercury electrode. Under controlled-potential conditions, the reduction proceeds initially by an ECE mechanism (electron transfer-chemical reaction-electron transfer) with n = 1 for both electron transfers. The chemical reaction involves a dissociation to produce a nickel species more easily reduced than the nickel(11) dithiocarbamate. However, for some derivatives, rate constants for the chemical step show a time dependence, at electrolysis times above 5 s, consistent with an ECCE mechanism of the type where the product of the first chemical reaction reacts further to produce a nickel species more difficult to reduce than nickel(11) dithiocarbamate. Exhaustive reduction of nickel(11) diethyldithiocarbamate at the mercury-pool electrode gave non-integral n-values (2 > n > 1) consistent with the ECCE mechanism, and demonstrated that the product of the second chemical reaction is reoxidized to nickel(11) diethyldithiocarbamate by oxygen. The nature of the complete electrode reaction suggests a metal-centred reduction.

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Dynamics of silicate exchange in highly alkaline potassium silicate solutions

Canadian Journal of Chemistry ◽

10.1139/v97-229 ◽

1998 ◽

Vol 76 (2) ◽

pp. 183-193

Author(s):

Eva Vallazza ◽

Alex D Bain ◽

Thomas W Swaddle

Keyword(s):

Rate Constants ◽

Relaxation Times ◽

Complete Analysis ◽

True Rate ◽

Line Shape Analysis ◽

Cyclic Trimer ◽

Selective Inversion ◽

Order Of Magnitude ◽

Kinetics Of ◽

Link Formation

The problem of measuring the kinetics of Si exchange between aqueous silicate species by 29Si NMR has been revisited, using highly alkaline KOH solutions (2.8 mol SiIV per kg solvent, [SiIV]/K2O = 0.43) at 60-90°C to minimize the number of silicate species present. Longitudinal 29Si relaxation times T1 and apparent rate constants estimated from line-shape analysis (LSA) varied markedly with the degree of purity of the KOH used, but rate constants k obtained by selective inversion-recovery (SIR) using the CIFIT data-fitting program were independent of the source of KOH and were smaller than those obtained from LSA by at least an order of magnitude. Although only four kinetically significant silicate anions (monomer M, dimer D, linear trimer L, and cyclic trimer C) were present, overlap of the D and L resonances prevented complete analysis of the SIR data. True rate constants could therefore be obtained only for the M-D exchange (for formation of D, k1 (90°C) = 0.13 ± 0.01 kg mol -1 s-1, Δ H1dagger = 67.4 kJ mol-1, Δ S1dagger = -78 J K-1 mol-1; for dissociation of D, k-1 (90°C) = 1.4 ± 0.1 s-1, Δ H-1dagger = 64.7 kJ mol-1, and Δ S1dagger = -66 J K-1 mol-1). Models that included L as the precursor of C (MDLC mechanism) showed, within the limitations imposed by D-L band overlap, that the reactivities of M, D, L, and C in Si-O-Si link formation or dissociation were all roughly comparable. Good fits of the experimental data, however, and equally reliable rate constants for the M-D exchange, could be obtained with models that ignored the presence of L entirely (MDC mechanism). The simple MDC model also provides consistent apparent rate constants kC and k-C for the overall formation of C from M + D and the reverse process, respectively, by SIR of either M or C ( Δ HCdagger = 76.5 kJ mol-1, Δ SCdagger = -57 J K-1 mol-1; Δ H-Cdagger = 88.6 kJ mol-1, and Δ S-Cdagger = -7 J K-1 mol-1).Key words: kinetics, silicates, 29Si NMR.

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Electron Transfer at Boron-Doped Diamond Electrodes. Comparison with Pt, Au and RuO2

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc20031621 ◽

2003 ◽

Vol 68 (9) ◽

pp. 1621-1635 ◽

Cited By ~ 3

Author(s):

Francesco Friso ◽

Sergio Trasatti

Keyword(s):

Electron Transfer ◽

Cyclic Voltammetry ◽

Exchange Reaction ◽

Rate Constants ◽

Electrolyte Solutions ◽

Reaction Rates ◽

Diamond Electrodes ◽

Boron Doped Diamond ◽

Boron Doped ◽

Order Of Magnitude

Electron exchange reaction rates were compared for boron-doped diamond (BDD), Pt, Au and RuO2 using [Ru(NH3)6]3+/2+ as a redox couple. The study was carried out by cyclic voltammetry; calculations were performed by Nicholson's procedure. The results show that the rate constants on BDD, Pt and Au are qualitatively similar, one order of magnitude higher than on RuO2. The outcome is explained in terms of the specific structure of the interface between oxides and electrolyte solutions.

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Faradaic impedance measurements of the ferrous/ferric citrate system

Australian Journal of Chemistry ◽

10.1071/ch9672567 ◽

1967 ◽

Vol 20 (12) ◽

pp. 2567

Author(s):

D Elliott

Keyword(s):

Electron Transfer ◽

Reaction Mechanism ◽

Ferric Citrate ◽

Negative Dependence ◽

Faradaic Impedance ◽

Impedance Measurements ◽

Impedance Technique ◽

Transfer Stage

An examination of the ferrous/ferric citrate system has been made by the faradaic impedance technique. Determination of the reaction mechanism by the dependence of the rate on concentration has been attempted. The results have proved ambiguous in deciding whether the rate is controlled chemically or by the electron transfer stage. In addition, the negative dependence of the rate on iron(II) concentration has proved difficult to account for and a mechanism involving iron(IV) has been tentatively proposed.

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Kinetics and Mechanism of Zn(II) Ion Electroreduction in the Presence of Vetranal

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc20080616 ◽

2008 ◽

Vol 73 (5) ◽

pp. 616-626 ◽

Cited By ~ 9

Author(s):

Jolanta Nieszporek ◽

Dorota Gugała-Fekner ◽

Dorota Sieńko ◽

Jadwiga Saba ◽

Krzysztof Nieszporek

Keyword(s):

Electron Transfer ◽

Mercury Electrode ◽

Surface Excess ◽

Forward Reaction ◽

True Rate ◽

Half Wave ◽

Reversible Potential ◽

Dropping Mercury Electrode ◽

Dc Polarography ◽

Bridging Model

The two-step reduction of Zn(II) ions at a dropping mercury electrode in 1 M NaClO4 with addition of vetranal was examined using dc polarography, cyclic voltammetry and impedance measurements. Small changes of reversible potential of half-wave, Er1/2, values indicate that the Zn(II)-vetranal complexes formed in the solution are very unstable. A stepwise character of electron transfer in the Zn(II) ion reduction was established. The catalytic activity of vetranal is stronger in the first step of electron transfer than in the second one. The linear dependence of the true rate constant for the forward reaction, ktf, of Zn(II) electroreduction versus relative surface excess, Γ′, of vetranal at a given potential in the reaction plane, Φr, was interpreted in terms of a "bridging model".

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