Cyclic voltammetry and differential pulse voltammetry of rescinnamine

Two redox processes can be4 observed for rescinnamine by cyclic voltammetry. The electroactive group is identified as the 3,4,5-trimethoxycinnamic. A mechanism including a homogenous dimerization reacyion following the electron transfer is proposed for the redoz process which occurs at less negative potentials, and the rate constant for the homogenous reactions is calculated. Differential pulse voltammetry is proved to be a suitable method for quantitative determination of the alkaloid.     

Cyclic staircase voltammetry

The use of cyclic staircase voltammetry was investigated in order to study kinetic mechanisms at low concentration levels. The reversible case for c.s.c.v. was studied along with two common kinetic cases: e.c. and catalytic mechanism. For both the e.c. and catalytic case, it was possible to correlate the peak current ratio with the rate constant with one working curve regardless of the step size, the step time or the time in the step in which the current was measured. For the catalytic mechanism, the increase in the peak current of the forward peak can also be correlated with the rate constant, once again regardless of the experimental parameters. Using this technique, high sensitivity can be obtained at low concentrations and fast scan rates as was shown by comparing c.s.c.v. with cyclic voltammetry for micromolar cadmium solutions. The use of staircase voltammetry for the study of the catalytic reaction between iron (III)-triethanolamine and hydroxylamine was demonstrated and a rate constant of 180 M^?1 s^?1 was obtained, which is consistent with previous work.     

Cyclic voltammetry of phenol

The possibility of phenol determination by cyclic voltammetry (CVA) on electrochemically modified glassy-carbon electrodes (GCE) was studied. The effect of the rate of linear potential sweep on the sensitivity of phenol determination was investigated. The adsorption nature of the analytical signal of phenol was revealed. The formation of the hydroquinone-quinone couple by the electrochemical oxidation of phenol was proved by CVA.     

Cyclic voltammetry at microstructured electrodes

We present the theoretical treatment of cyclic voltammograms at microstructured electrodes. Calculations of voltammograms permit the determination of electrochemical parameters of redox systems in a single cell in parallel with the determinations of the spectroscopic parameters. The structural parameters of the electrode can be determined using the theoretical treatment presented if the electrochemical parameters of the redox system are known. Furthermore, lithographic-galvanic (LIGA) structures can be used as a model for microporous electrodes. Regression analysis was used to compare experimental and calculated cyclic voltammograms as well as to determine the electrochemical and spectroscopic parameters. A modified Randles-Sevčik equation has been derived to described the peak current dependence of cyclic voltammograms at micro-structured electrodes for both reversible and quasi-reversible charge transfer.     

Electrochemistry of organometallic compounds: I. Cyclic voltammetry of organocobaloximes in aqueous acid solutions

This paper presents a systematic investigation on effects of the nature of the organic axial ligand on the primary electrochemical oxidation steps of organoaquobis(dimethylglyoximato)cobalt(III). Evidence is presented to support a one electron reversible process, yielding a cobalt(III) compound attached to the organic radical. Studies of p-substituted benzyl and phenyl derivatives support further the proposed process. The following step is a pseudo-first order irreversible dissociation of the oxidized species, yielding the trans-Co(DH)₂(H₂O)⁺ and the organic radical that can be further oxidized at the electrode. Linear free energy correlations obtained between E_1/2 and Taft or Hammett parameters, depending on the nature of the organic substituent in axial position, strongly favor that Co-alkyl(aryl) bonding electrons are involved in the electron transfer.     

Reaction of perfluorodimethylm ercury and its analogs with silyl- and stannylmercury compounds

Conclusions Bis(triethylsilyl)mercury reacts with HgR₂(R=CF₃, CF₂CF₃) to give the corresponding perfluoro-alkyl(triethylsilyl)mercury compounds. The analogous reaction with bis [tris(trimethylsilylmethyl) stannyl]-mercury is catalyzed by fluoride anions and is complicated by the decomposition of the unsymmetrical stannylmercury compounds.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 189–191, January, 1973.     

Cyclic voltammetry studies on pure lead

A potentiometric study of complex formation between gallium and L-serine, L-tyrosine, L-methionine shows the existence of the complexes Ga(L₀)³⁺ and Ga(L_?)²⁺. In the case of L-cysteine, the complex Ga(L_2?)⁺ exists also. L₀, L_?, L_2? designate respectively the zwitterion and the mono- and divalent anions of amino acid. The stability constants of the complexes have been determined.     

Cyclic voltammetry and theoretical calculations of silyl-substituted 1,4-benzoquinones

Cyclic voltammograms of 2,3,5,6-tetrakis(trimethylsilyl)-1,4-benzoquinone (1a), 2,3,5,6-tetrakis(dimethylvinylsilyl)-1,4-benzoquinone (1b), 2,3,5,6-tetrakis(dimethylsilyl)-1,4-benzoquinone (1c), 4,4,6,6,10,10,12,12-octamethyl-4,6,10,12-tetrasilatricyclo[7.3.0.0^3,7]dodeca-1(9),3(7)-diene-2,8-dione (1d), and 5-t-butyl-2-(pentamethyldisilanyl)-1,4-benzoquinone (5h) showed that the first reduction step was reversible and that the second step was irreversible. The first half-wave reduction potentials of 1a, 1b, 1c, and 1d shifted negatively relative to 1,4-benzoquinone by −0.31, −0.24, −0.03, and −0.18 V, respectively. These results demonstrated that the electron-accepting ability of the chair-form quinones 1a and 1b was lower than that of the planar quinones 1c and 1d. The of 5h (−0.93 V vs. Ag/Ag⁺) was quite similar to that of 5-t-butyl-2-trimethylsilyl-1,4-benzoquinone (5a, −0.94 V). A cyclic voltammogram of dimethylsilylene-bridged 1,4-benzoquinone dimer 7 showed two kinds of (−0.76 and −0.94 V). The electrochemical behavior of 7 would be interpreted in terms of near-neighbor interactions between reduced and non-reduced quinone units. Theoretical calculations of the silyl-1,4-benzoquinones reproduced well the solid state structures of the compounds. Also, the computed vibrational frequencies of the silyl-1,4-benzoquinones were in good agreement with the IR absorption frequencies of the CO units in the compounds. The LUMO energy levels of the silyl-1,4-benzoquinones were quantitatively proportional to the .     

Cyclic voltammetry of copper in sodium hydroxide solutions

The cyclic voltammograms of the Cu electrode were, obtained in NaOH solution as a function of the voltage scanning rate, electrolyte concentration and voltage range. A correlation was made between three well-defined anodic peaks and their corresponding cathodic ones. The anodic peaks were found to correspond successively to the formation of a monolayer of Cu₂O, formation of a thick multilayer film of CuO and finally Cu₂O₃ upon which O₂ is evolved. It is suggested that CuO is formed from the oxidation of Cu₂O and/or direct oxidation of metallic copper.Below 0.1 M NaOH the ratio of anodic to cathodic charges was found to be about unity, indicating the quantitative reduction of solid oxidation products, while at higher alkali concentrations higher charge ratios were obtained due to increasing proportions of soluble reaction products.The behaviour of the copper electrode in NaOH was found to be quite complicated. Thus, no simple relations were found between the voltage scanning rate and both the peak current and peak potential or between the peak current and the alkali, concentration. Further work is needed to obtain a definitive explanation of this behaviour.     

Cyclic voltammetry of iron dimine complexes in acetonitrile

The electrochemical behavior of iron diimine complexes, (H₃C?N=C(R)?C(R′)=N?CH₃)₃Fe(II) (R, R′=H,H;H, CH₃; CH₃, CH₃), and (C₅H₄N?C(R₁)=N(R₂))₃Fe(II) (R₁, R₂=H, CH₃; CH₃, CH₃) on a platinum working electrode in acetonitrile is described, and compared to that of the parent aromatic complex, tris-(2,2′-bipyridine)Fe(II). One-electron reversible oxidations were found for all the compounds studied. The electrochemical reductions show 2–3 reduction waves in the potential range studied. Only for the complexes of mixed diimine ligands or 2,2′-bipyridine, a pre-adsorption wave is also observed. It is possible to stabilize low valence states with all ligands studied. A formal iron(I) state is described for the first time for all aliphatic diimine complexes, thus showing that the acceptor properties of the diimine complexes do not depend on the presence of the aromatic rings, but on the iron-diimine chromophore.     

Cyclic unsaturated compounds

Conclusions Reversible structural isomerization of 1,3- and 1,2-dimethylsubstituted cyclopentadienes, proceeding according to a mechanism of 1,2-shift of the methyl group from the 5-position of the cyclopentadiene ring, accompanied by the migration of the system of intracyclic double bonds, is carried out at the temperatures 400–500°. In conjunction with the 1,2-shift of hydrogen, the indicated conversion leads to the formation of an equilibrium mixture of structural isomers, containing 38% 1,3-dimethylcyclopentadienes and 62% 1,2-and 2,3-dimethylcyclopentadienes (total).For communication 36 of this series, see [1].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 1978–1983, September, 1971.