Showing papers on "Polarography published in 1970"
TL;DR: In this article, the reduction potential of dipyrido[3,2-a:2',3'-c]-phenaiine was shown to be -0.40 V against a standard calomel electrode.
Abstract: 1,l0-Phenanthroline-5,6-quinone is prepared from 1,l0-phenanthroline via 5-nitro-1,l0-phenanthroline and 5-amino-1,l0-phenanthroline. It is converted by standard methods into 4,5-diazafluoren-9-one, 4,5-diazafluoren-9-ol,4,5-diazafluorene, and the new heterocyclic system dipyrido[3,2-a:2',3'-clphenazine. These four compounds each form a complex with cupric chloride. They thus represent a new series of chelating agents. By reaction with ethylene dibromide, dipyrido[3,2-a:2',3'-c]-phenaiine forms a diquaternary salt which is reduced in aqueous solution by a one-electron transfer to a highly coloured radical cation. Polarography experiments show that the reduction potential of the salt is -0.40 V against a standard calomel electrode.
326 citations
TL;DR: It was possible by using these methods to work with lower DNA concentrations and to measure at lower pH, and the dependences of limiting dc polarographic currents of denatured DNA onpH had S-shaped courses.
Abstract: The behaviour of denatured DNA was studied with the aid of classical (dc) polarography, alternating current polarography, oscillopolarography and pulse-polarography. The dependences of limiting dc polarographic currents of denatured DNA onpH had S-shaped courses. The curves of S-shaped dependences shifted to variouspH according to the concentration and to the type of salts of background electrolyte. In the regions ofpH, where the height of dc polarographic step almost did not change withpH, the limiting current had the character of diffusion controlled currents. At higherpH, when the drop of current occurred, the dc polarographic curves had a maximum form. The decrease of current and the appearance of the maximum-like curve is probably connected with adsorption/desorption processes which take place on the electrode at negative potentials. S-shaped course had even the dependence of the height of pulse-polarographic curves and the depths of an indentation on the oscillopolarograms dE/dt againstE on pH. In difference to the dc polarography, it was possible by using these methods to work with lower DNA concentrations and to measure at lower pH.
102 citations
72 citations
TL;DR: In this paper, the electrochemical oxidation of four 1,2-ene-diamines is studied on mercury and platinum electrodes in acetonitrile and benzonitrile.
68 citations
52 citations
TL;DR: In this article, the adsorption of the depolarizer leads to an increase in the sensitivity of the analytical determination with different methods to different extents ; the highest increase, almost 100-fold, was found with the controlled current methods.
51 citations
46 citations
TL;DR: In this article, the effect of tetraethylammonium ions on the catalytic wave has been investigated and a mechanism which involves a rapid adsorption equilibrium between the bulk and adsorbed nickel(II)-thiocyanate complexes was proposed.
35 citations
TL;DR: In this paper, the relative location of the highest occupied and lowest vacant orbitals for a series of structurally similar π-complexes is discussed, and the relation between the reduction potential of the LnM-σ-R bond and the pKa RH has been found; pKa values for a number of metallocenes as a C-H-type acid have been determined.
Abstract: Polarography on both the dropping mercury and solid electrodes in aprotic solvents, electrolysis at a controlled potential, oscillopolarography, potentiometry, etc., along with non-electrochemical methods (such as e.s.r., nuclear-γ-resonance, i.r., n.m.r. spectroscopies) of a great number of organometallic transition metal π-complexes has been covered in detail. Methods and procedures are considered which may be helpful in the solution of such problems as a localization of electronic changes in a complex which may occur (a) on metal orbitals; (b) on the π-ligand orbitals, and (c) on the antibonding orbital of the metal–σ-ligand bond. The application of electrochemical methods in the solution of such problems as the relative location of the highest occupied and lowest vacant orbitals for a series of structurally similar π-complexes is discussed. The relation between the reduction potential of the LnM—σ—R bond and the pKa RH has been found; pKa values for a number of metallocenes as a C—H-type acid have been determined.
33 citations
TL;DR: In this article, it was shown that reduction waves corresponding to formation of mercury compounds are formed by the unprotonated species Reduction waves of compound 1, and uv absorption bands and anodic waves of compounds I-IV are suitable for analytical purposes.
TL;DR: In this article, the polarographic behavior of 38 herbicides was studied in 5 supporting electrolytes using single sweep derivative polarography and the 16 compounds showing the greatest polarographic activity were investigated further in order to estimate their detection limits.
Abstract: The polarographic behaviour of 38 herbicides was studied in 5 supporting electrolytes using single sweep derivative polarography. The 16 compounds showing the greatest polarographic activity were investigated further in order to estimate their detection limits. It is suggested that polarography might provide a useful technique for the analysis of 12 of these materials.
TL;DR: In this article, the electrolysis of N-heterocyclic compounds is discussed and the polarographic results are provided to supplement the discussion and to suggest further use of preparative electrolysis.
Abstract: Publisher Summary This chapter discusses the electrolysis of N-heterocyclic compounds and emphasizes on preparative electrolysis. The polarographic results are provided to supplement the discussion and to suggest further use of preparative electrolysis. The chapter focusses on electrolysis at a controlled potential. The electrolysis of an organic compound involves one or more steps in which electrons are transferred to or from the electrode and some chemical steps before and/or after the electrochemical steps. Electrode reactions may be divided into two main types depending on whether the electron transfer occurs directly between the electrode and the substrate or whether the electron is transferred to (or from) another species, which then reacts with the substrate. The apparatus for electrolysis requires electrodes, cells and circuits. The electrolytic formation of heterocyclic systems involves ring closure reactions, ring contractions, and ring expansions. The electrode reactions of heterocyclic compounds where a reduction or oxidation of the nucleus takes place are discussed. The electrolysis of substituted heterocyclic compounds, where the electrode reaction involves the substituent directly or when it plays an essential role in determining the course of the reaction and the reductions leading to ring contractions has been described.
TL;DR: In this article, the polarographic and chronopotentiometric behavior of nickel(II)-acetyl-acetonate complexes is examined in the pH-range 3.6-9.8.
TL;DR: A wide range of olefin-mercury(II) acetate addition compounds were polarographically examined and found to exhibit two 1-electron waves over most of the pH scale as mentioned in this paper.
TL;DR: In this paper, the reversible polarographic reduction of acetophenone, free and coordinated with the (CO)3Cr-group in aprotic media was investigated and the analogy between the polarographic data for coordinated and non-coordinated acyclic compounds was made.
TL;DR: In this paper, the polarographic behavior of the iodide ion, the triiodomercurate ion, and mercuric iodide at the dropping mercury electrode was investigated in dimethylformamide, using d.c. polarography, controlled potential electrolysis, and oscillographic polarography with a multi-triangular voltage sweep.
Abstract: The polarographic behavior of the iodide ion, the triiodomercurate ion, and mercuric iodide at the dropping mercury electrode was investigated in dimethylformamide, using d.c. polarography, controlled potential electrolysis, and oscillographic polarography with a multi-triangular voltage sweep. The iodide ion gives two well-defined anodic waves: the first wave corresponds to the reversible oxidation of mercury to the triiodomercurate ion, and the second, to the reversible oxidation of mercury to mercuric iodide. A maximum arises on the reduction wave of the triiodomercurate ion, but it is suppressed by the addition of a small amount of polyvinyl chloride. The oscillographic polarograms and electrocapillary curves suggested that the iodide ion, like the triiodomercurate ion and mercuric iodide, is strongly adsorbed on the dropping mercury electrode. The maximum on the wave due to the reduction of the triiodomercurate ion to mercury and the iodide ion was ascribed to the convection of the mercury drop, whic...
TL;DR: In this article, a microcoulometric method of determination of 2-methyl-1,4-naphthoquinone (vitamin K 3 ) with electrogenerated cerium(IV) ion is described.
TL;DR: The double anodic wave observed at low ionic strength in perchlorate is consistent with previous studies of the system and appears to have its origin in double layer effects rather than in an intermediate in the reduction.
TL;DR: In this paper, the possibility of using the simple calculation method of plotting ΔE1/2 vs. the logarithm of the concentration of the ligand, for the class of the electrode reaction in which the non-reversibility is due to the charge transfer step and is independent of complex formation, has been investigated.
TL;DR: In this paper, the authors used ac polarographic methods to evaluate the half-wave potentials and diffusion currents of the chloride complexes of Bi(III) and Sb(III), as both these electrode reactions exhibit pronounced maxima in chloride media.
TL;DR: In this paper, the electrochemical behavior of bis(2-phenyl-3-indolinone)azine (I) in dimethylformamide solution was studied by polarography, cyclic voltammetry, controlled-potential coulometry and ultraviolet spectroscopy.
TL;DR: Direct current polarography and several related techniques have been evaluated for the determination of metal derivatives of ethylenebisdithiocarbamic acid, and cathodic stripping analysis has been shown to be the most suitable.
Abstract: Direct current polarography and several related techniques have been evaluated for the determination of metal derivatives of ethylenebisdithiocarbamic acid, and cathodic stripping analysis has been shown to be the most suitable. Ethylenethiuram monosulphide has been identified as a major breakdown product of the ethylenebisdithiocarbamate anion.
TL;DR: In this paper, it was shown that 2-thiopurine is reduced at DME by way of three polarographic waves, the first stage is a one-electron reduction to a free radical species which below pH 5 can be further reduced in a second oneelectron process to 1,6-dihydro-2-thypurine.
TL;DR: In this article, a study of the U(VI)/U(V) couple in lithium hydroxide solutions has been carried out by polarography, at concentrations of uranium(VI) and lithium hydride at which the former is soluble and stable.
TL;DR: In this article, a polarographic study of the effect of the double layer on the kinetics of electroreduction of peroxydisulphate anion at a mercury electrode in formamide is presented.
TL;DR: In this article, linear calibration graphs were obtained over the concentration range 10 −4 to 10 −3M by d.c. and a.c., and 10 −6 to 10−4M by a. c. polarography.
Abstract: Methods have been evaluated for the determination of tetramethylthiuram disulphide by d.c. and a.c. polarography. Linear calibration graphs were obtained over the concentration range 10–4 to 10–3M by d.c. polarography, and 10–6 to 10–4M by a.c. polarography. The electrode reaction was studied by cyclic voltammetry and evidence obtained to support the postulated mechanism of reduction of the S—S bond to give two dimethyldithiocarbamate molecules.