Polarography and coulometry of Rh(III) in a pyridine – pyridinium chloride electrolyte

1969 ◽  
Vol 47 (12) ◽  
pp. 2123-2135 ◽  
Author(s):  
Leslie E. Johnston ◽  
John A. Page
Keyword(s):  
Mercury Electrode ◽  
Normal Wave ◽  
Bulk Solution ◽  
Pyridinium Chloride ◽  
Chloride Electrolyte ◽  
Catalytic Wave ◽  
Controlled Potential Electrolysis ◽  
Dropping Mercury Electrode ◽  
Controlled Potential ◽  
Electron Reduction

The polarography and coulometry of Rh(III) has been studied in an aqueous pyridine–pyridinium chloride–sodium chloride electrolyte at pH 5.30 and ionic strength 0.30 M at 25.0 °C. Two distinct types of polarographic behavior were noted as the total Py concentration was varied between 0.05 and 0.45 M, a "normal" wave with E1/2 of −0.43 V vs. a standard calomel electrode, and a second catalytic wave which under some conditions masked the normal wave.For both types of behavior, controlled potential electrolysis gave a well-defined two electron reduction but there was a definite H+ consumption in the electrolyses. It is postulated that hydride species are involved in the reduction according to the scheme[Formula: see text]surface reaction at dropping mercury electrode[Formula: see text]slow, bulk solution in controlled potential electrolysis

Polarography of aromatic azo compounds. II. Kinetic study of the disproportionation of 4-Aminohydrazobenzene-4'-sulphonic acid

1965 ◽  
Vol 18 (5) ◽  
pp. 619 ◽  
Author(s):  
TM Florence
Keyword(s):  
Mercury Electrode ◽  
Sulphonic Acid ◽  
Azo Compounds ◽  
Rate Determining Step ◽  
A Value ◽  
Controlled Potential Electrolysis ◽  
Mercury Cathode ◽  
Dropping Mercury Electrode ◽  
Controlled Potential ◽  
Aromatic Azo Compounds

Solutions of 4-aminoazobenzene-4'-sulphonic acid were reduced by controlled potential electrolysis at a mercury cathode, and the disproportionation rate of the hydrazo derivative determined by spectrophotometry and polarography. The kinetics of the reaction were found to be first-order with respect to both hydrazo and hydrogen ion concentrations, although the overall reaction involved two molecules of the hydrazo compound. In the rate law, -d[hydrazo]/dt = k[H+][hydrazo], k was calculated to be (5.0�0.3) x 106 l. mole-1 sec-1 from spectrophotometric measurements, and (4.5�0.5) x 106 l. mole-1 sec-1 by polarography (25�). A reaction mechanism based on a rate determining step involving a quinonediimine intermediate has been proposed. Another value of the disproportionation rate constant was obtained from the effect of drop time on the limiting currents of 4-aminoazobenzene-4'-sulphonic acid at the dropping mercury electrode. A value of k of (22�5) x 106 l. mole-1 sec-1 was determined by this method. Reasons for the discrepancy between this result, and those found by direct measurement, are discussed.

The reduction of cobalt (II) ion in thiocyanate media by pulse polarography

1983 ◽  
Vol 48 (2) ◽  
pp. 544-549 ◽  
Author(s):  
Jorge Alfredo Bolzan ◽  
Robert Tokoro
Keyword(s):  
Mercury Electrode ◽  
Thiocyanate Complex ◽  
Catalytic Wave ◽  
Pulse Polarography ◽  
Dropping Mercury Electrode ◽  
Thiocyanate Concentration

The electroreduction of cobalt(II) in aqueous thiocyanate solutions at the dropping mercury electrode depends on the thiocyanate concentration. At [SCN-] = 0.3 mol/l the intermediate cobalt(I)-thiocyanate complex does exist electrokinetically and may be responsible for the appearance of a peaked catalytic wave. The predecessor species of this intermediate may be CoSCN+ and Co(SCN)2 in similarity to the behaviour of cobalt(II) with cyanide and azide ions.

Polarography as an Analytical Tool

1964 ◽  
Vol 47 (1) ◽  
pp. 21-27
Author(s):  
John K Taylor
Keyword(s):  
Mercury Electrode ◽  
Selective Extraction ◽  
Analytical Tool ◽  
Diffusion Control ◽  
Oscillographic Polarography ◽  
Dropping Mercury Electrode ◽  
Anodic Stripping ◽  
Controlled Potential ◽  
Solid Electrodes ◽  
Practice Methods

Abstract Polarography is a useful analytical tool for determining many substances in solutions at small concentrations, and is frequently applied to analysis of minor constituents. Conventional polarography employs a dropping mercury electrode, can measure solutions in concentrations ranging from 10-2 to 10-5M, and requires only a few tenths of ml for analysis. Because of the difficulty of obtaining diffusion control in practice, methods are comparative and involve empirical calibrations with standard solutions. Practical tolerances have been worked out to insure that results are reliable to 2 relative per cent. Interferences have been lessened by several means, e.g., complexing, separation by electrolysis at controlled potential, selective extraction, and improvements in circuitry to permit use of relatively dilute supporting electrolytes. Modified polarographic methods include solid electrodes, derivative polarography, differential polarography, cathode ray polarography, anodic stripping polarography, and oscillographic polarography.

The polarography of some substituted azobenzenes in acetonitrile. II. Identification of reduction products

1973 ◽  
Vol 26 (6) ◽  
pp. 1251 ◽  
Author(s):  
KG Boto ◽  
FG Thomas
Keyword(s):  
Visible Spectrophotometry ◽  
Controlled Potential Electrolysis ◽  
Controlled Potential ◽  
Electron Reduction

The reduction products of azobenzene and 4-nitroazobenzene in acetonitrile were investigated by polarography and ultraviolet-visible spectrophotometry after generation by controlled potential electrolysis. The results obtained indicate that azobenzene is reduced in two steps to give firstly the monoanion and secondly the monoprotonated form of the dianion, whereas 4-nitroazobenzene gives the monoanion and the dianion, respectively, as the products of the two one-electron reduction steps. The azobenzene monoanion undergoes a very slow disproportionation (k = 8.2 dm3 mol-1 min-1) to produce azobenzene and the monoprotonated dianion in equimolar amounts. The second reduction products of both compounds are stable in the absence of oxygen.

Electrochemical investigation of reduction of mercury complexes of 2-aminocyclopentene-1-dithiocarboxylic acid and some of its derivatives at mercury electrodes

1996 ◽  
Vol 74 (1) ◽  
pp. 95-102 ◽  
Author(s):  
A. Safavi ◽  
M. B. Gholivand
Keyword(s):  
Electrochemical Techniques ◽  
Mercury Electrode ◽  
Elemental Mercury ◽  
Redox Processes ◽  
Electrochemical Investigation ◽  
Controlled Potential Electrolysis ◽  
Mercury Complexes ◽  
Controlled Potential ◽  
Mercury Electrodes ◽  
Complementary Study

Electrochemical techniques of polarography, cyclic voltammetry, and controlled potential electrolysis at mercury electrodes have permitted a detailed investigation of the reduction reactions associated with mercury 2-aminocyclopentene dithiocarboxylate complexes, Hg(ACD)2, in dimethyl sulphoxide (DMSO). As a complementary study, the electrochemistry of the ligands themselves was investigated in DMSO solutions and at mercury electrodes. The lability of mercury(II) complexes and their rapid interaction with elemental mercury strongly influence the nature of the redox processes observed at mercury electrodes. Reduction of Hg(ACD)2 at a mercury electrode occurs in an overall two-electron step as:[Formula: see text]although mercury(I) is implicated as an intermediate. Key words: reduction, electrochemical techniques, mercury complexes.

The electrochemical oxidation of 2,5-dihydroxybenzoic acid on a mercury electrode in aqueous solutions

1986 ◽  
Vol 64 (1) ◽  
pp. 11-14 ◽  
Author(s):  
D. Sazou ◽  
N. Papadopoulos
Keyword(s):  
Oxidation Process ◽  
Electrochemical Behaviour ◽  
Mercury Electrode ◽  
The Other ◽  
Hanging Mercury Drop Electrode ◽  
Dihydroxybenzoic Acid ◽  
Current Function ◽  
Controlled Potential Electrolysis ◽  
Controlled Potential ◽  
Ph Range

The electrochemical behaviour of 2,5-dihydroxybenzoic acid (2,5-DHBA) has been studied in the pH range 5.5–12.7 at a hanging mercury drop electrode (HMDE). Voltammograms show the existence of one reversible wave of 2,5-DHBA governed by diffusion conditions. In the oxidation process a two-electron transfer takes place, as shown by the controlled potential electrolysis. From the calculation of the voltammetric parameters (peak width Ep − Ep/2, peak current function [Formula: see text]and from the other experimental data, a mechanism for the overall reaction in two different pH ranges, 5.5–9.5 and 9.5–12, is proposed.

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

1997 ◽  
Vol 75 (7) ◽  
pp. 1023-1029 ◽  
Author(s):  
A. Safavi ◽  
L. Fotouhi
Keyword(s):  
Electron Transfer ◽  
Electrochemical Techniques ◽  
Mercury Electrode ◽  
Electrode Reaction ◽  
Ece Mechanism ◽  
Reduction Mechanisms ◽  
Ec Mechanism ◽  
Controlled Potential ◽  
Electron Reduction ◽  
Derivatives Of

The reduction mechanisms of a series of nickel(II) dithiocarboxylate complexes have been investigated in dimethyl sulphoxide at the mercury electrode. Various electrochemical techniques, including polarography, cyclic voltammetry, chronoamperometry, and controlled potential coulometry, were employed. The reduction of the complexes of the acid derivatives of 2-aminocyclopentene-1-dithiocarboxylate (ACD) proceeds initially by an ECE mechanism (electron transfer – chemical reaction – electron transfer) followed by a one-electron irreversible process. The nature of the complete electrode reaction suggests a metal-centered reduction. The nickel complexes of the ester derivatives of ACD underwent a one-electron reduction that was subject to a follow-up catalytic reaction (EC′ mechanism) and the original complex is regenerated through this regeneration reaction. Keywords: reduction, nickel(II) dithiocarboxylate, mercury electrode.

The Reactions of Electrogenerated [Ni(sacsac)2]-: Biomimetic Chemistry Related to Nickel Enzymes

1995 ◽  
Vol 48 (4) ◽  
pp. 835 ◽  
Author(s):  
PA Lay ◽  
AF Masters ◽  
CD Wasiowych
Keyword(s):  
Cyclic Voltammetry ◽  
Lewis Base ◽  
Spectroscopic Methods ◽  
Initial Product ◽  
Light Water ◽  
Nickel Enzymes ◽  
Controlled Potential Electrolysis ◽  
Scan Rate ◽  
Controlled Potential ◽  
Electron Reduction

The electrochemical reduction of [Ni( sacsac )2] ( sacsac = C5H7S2- = pentane-2,4-dithionate) has been investigated by cyclic voltammetry and controlled-potential electrolysis in acetone/tetra- butylammonium tetrafluoroborate (0.1 M). The reactions of the reduction product(s) with CO, CO2, CH3I, C12H25SH, light and water have been surveyed. At a scan rate of 100 mV s-1, [Ni( sacsac )2] (0.5 mM ) undergoes a quasi-reversible one-electron reduction (∆ Ep = 88 mV) at -1.543 V (v. Fc+/0) and an irreversible four-electron oxidation at +0.635 V. The oxidation generates the 3,5-dimethyl-1,2-dithiolium cation, as evidenced by the observation of the (known) reduction of this cation at -0.840 V. The initial product of the reduction of [Ni( sacsac )2] is a Lewis base, and reacts with light, water, CO, CO2, CH3I and C12H25SH. These reactions have been followed by electrochemical and spectroscopic methods. They appear to be biomimetic for a number of reactions observed for nickel enzymes.

Electrochemical Studies of Organotitanium Nitrogen Fixation Systems

1973 ◽  
Vol 51 (6) ◽  
pp. 815-820 ◽  
Author(s):  
T. Chivers ◽  
E. D. Ibrahim
Keyword(s):  
Cyclic Voltammetry ◽  
Nitrogen Fixation ◽  
Electrochemical Reduction ◽  
Argon Atmosphere ◽  
Electrochemical Studies ◽  
Controlled Potential Electrolysis ◽  
Controlled Potential ◽  
Electron Reduction ◽  
The One ◽  
Ether Solvents

The electrochemical reduction of compounds of the type (π-Cp)2Ti(R)Cl (R = Cl, CH3, C6H5, C5F5, OTiCl(π-Cp)2) in ether solvents has been studied using the techniques of polarography, controlled potential electrolysis, and cyclic voltammetry. The one-electron reduction products, presumably (π-Cp)2TiR (R = CH3, C6F5), are initially green in tetrahydrofuran but, in a dinitrogen or argon atmosphere, they form intensely blue solutions which result from the reaction of (π-Cp)2TiR with tetrahydrofuran solvent.

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