Reverse pulse voltammetry. Application to second-order following reactions

Osteryoung, Janet; Talmor, D.; Hermolin, J.; Kirowa‐Eisner, E.

doi:10.1021/j150603a014

Cited by 32 publications

(10 citation statements)

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“…The electrochemical studies were carried out by conventional electrochemical methods, such as DC and normal-pulse polarography (NPP) and the recently introduced reverse-pulse polarographic (RPP) technique (29,30). RPP is a pulse-polarographic technique that has the quantitative merits of the double-potential-step method and the diagnostic strength of cyclic voltametry.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Electroreduction of 1‐Methyl‐2‐, 3‐, and 4‐Carbomethoxypyridinium Ions

Kashti‐Kaplan

Hermolin

Kirowa‐Eisner

1981

J. Electrochem. Soc.

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The character of both polarographic waves of the three isomers 1‐methyl‐2‐, 3‐, and 4‐carbomethoxypyridinium ions (2+, 3+ , and 4+, respectively) has been studied in acetonitrile and in methanol. The first wave is due to a one‐electron reduction under DC and normal pulse polarographic (NPP) conditions. Whereas a stable free radical 4ċ is reversibly formed in the reduction of 4+ and a dimer is irreversibly formed in the reduction of 3+, the 2+ reversibly forms radical 2ċ at low concentration and short pulse width and a dimer under DC conditions. The equilibrium constant and the rate constants for the dimerization reaction 2ċ⇌1/2 dimer have been determined by the reverse‐pulse polarographic method (RPP). The radicals 2ċ and 4ċ have been identified by RPP, and the formal potentials of the couples 2+/2ċ and 4+/4ċ are reported. The second reduction wave of the three compounds is diffusion controlled in protic media (methanol) and yields dihydropyridine as a product. In acetonitrile, the pyridinium salts (n+) exhibit quite complicated behavior, which is dependent on the nature of the pyridinium ion (position of the carbomethoxy group on the ring) and its concentration, the nature of the cations present in the solution, and the time scale in which the electrochemical method is applied. The 3+ isomer does not undergo a second reduction step in this solvent. The anions 2− and 4− react with the cations to form normalnH (dihydropyridines), normalnLi , normalnNa , or the corresponding dimers n‐n (reaction with the starting material n+). The latter reaction causes a decrease in the amplitude of the second wave and is the most favored reaction in the presence of the indifferent bulky tetrabutylammonium cation, under which conditions the anions (2− and 4−) are most stable and are easily detected. The formal potential of the couples 2ċ/2− and 4ċ/4− are reported.

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Section: Resultsmentioning

confidence: 99%

“…Products and intermediates are accumulated in the diffusion layer and their electroactivity is displayed during the application of a short anodic or cathodic potential pulse (milliseconds) during which the resulting current is measured. Examples of uses of RPP in electrode kinetics have been given elsewhere (29,30).…”

Section: Resultsmentioning

confidence: 99%

Electroreduction of 1‐Methyl‐2‐, 3‐, and 4‐Carbomethoxypyridinium Ions

Kashti‐Kaplan

Hermolin

Kirowa‐Eisner

1981

J. Electrochem. Soc.

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“…However, measurements at a variety of drop times, r, and pulse widths, ip, showed that the height of this wave, írp,h2o2> 18 equal within experimental error to the height of the DC wave for reduction of H202. This indicates that this wave is due to oxidation of H202 diffusing to the electrode during the time of the pulse according to the equation H202 + 20H--02 + 2H20 + 2e" (3) It might be asked why, if this identification of the small wave is correct, this wave does not appear in the DC polarogram. The answer is quite simple.…”

Section: Resultsmentioning

confidence: 99%

“…Pulses are applied to successively more positive values, and the resulting curve of current vs. pulse potential is an RP polarogram of the product of the electrode reaction which takes place at the initial potential. Reverse pulse polarography has been used to study the mechanism of electrode reactions (2)(3)(4)(5)(6)(7)(8)(9), to determine diffusion coefficients (10), and for analytical purposes (11). The RP technique can be especially useful analytically when the voltammetric properties of the reaction product are more favorable than those of the reactant itself or when the reduction of the reactant is not well-separated from reduction waves for other substances in solution.…”

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confidence: 99%

Direct and titrimetric determination of hydrogen peroxide by reverse pulse polarography

Brestovisky¹,

Kirowa‐Eisner²,

Osteryoung³

1983

Anal. Chem.

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Hydroxide produced In the polarographic reduction of hydrogen peroxlde gives rise to an anodlc wave for mercury. I n the reverse pulse polarographic mode this wave Is strictly proportional to concentration of hydrogen peroxide In the range 0.007-1.5 mM with dlffusion current constant 6.5 /*A This wave may be used analytlcally for direct determlnatlon of hydrogen peroxlde or It may be used as the lndlcator current for an lndlrect determinatlon employing amperometrlc tltratlon In the dlffuslon layer with strong acid. s112 ,,,~-l mg-2J3.Reverse pulse (RP) polarography is a technique for examining the products of electrochemical reactions (1). In its most usual application the potential is held at an initial value at which the substance OF interest is reduced under diffusion control. Then once in the life of each mercury drop a pulse is applied in the positive direction and the current is sampled near the end of the pulse width. Pulses are applied to successively more positive values, and the resulting curve of current vs. pulse potential is an RP polarogram of the product of the electrode reaction which takes place at the initial potential. Reverse pulse polarography has been used to study the mechanism of electrode reactions (2-9), to determine diffusion coefficients (lo), and for analytical purposes (11).The RP technique can be especially useful analytically when the voltammetric properties of the reaction product are more favorable than those of the reactant itself or when the reduction of the reactant is not well-separated from reduction waves for other substances in solution. The determination of the product may be carried out directly by measuring the height of the RP wave, or it may be done indirectly by titration in the diffusion layer using the RP limiting current for amperometric detection of the end point.An additional feature of this approach is that a wide variety of substances, all of which have the same product, may be determined by use of the same voltammetric wave. In general these classes of compounds are reduced totally irreversibly, and the product is not reoxidized to the starting material on the RP wave. An example of such a class is HzO, IlzOz, 02, and other peroxides or superoxides which generally produce hydroxide on c?lectrocliemical reduction. These reductions are generally irreversible and the resulting waves are poorly suited for direct voltanimetric determinations. However, the hydroxide produced readily depolarizes mercury, according to the reaction Hg + 20H-= Hg(OH), + 2e-and under well-defined ranges of pulse widths and concentrations the resulting (anodic wave is diffusion controlled in hydroxide concentration (12). Here we report on the direct and titrimetric determination of HzOz in unbuffered aqueous solution by using the IRP wave of hydroxide for direct measurement or as an indicator of the end point of an acid-base titration in the diffusion layer.The direct determination based on the height of the RP wave relies on calibration curves obtained for known concentrations of hydrox...

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“…Among other applications, this technique has been employed for evaluation of the electrochemical reversibility of electrode processes [3,4], in the study of electrogenerated products [3] and reaction mechanisms [5][6][7][8] and for determination of diffusion coefficients [9], being particularly valuable when unstable products are involved.…”

Section: Introductionmentioning

confidence: 99%