Search results for "Polarography"
showing 6 items of 46 documents
Apparent activation energies and apparent frequency factor in polarographic waves of paludrine-Zn(II)
1993
Abstract Arrhenius and Vlcek plots of ac 1 and dp polarograms of paludrine-Zn complexes are tested in order to understand the apparent activation energies and pre-exponential factor, and their dependence on the potential. These empirical treatments are useful for obtaining information about the energetic contributions of the elemental processes associated with the Zn(II) and paludrine ligands in the overall mechanism of reduction of the complex 2:1 on the mercury interface.
Antidiabetic Behavior of Biguanides
1983
The existence of active electron pairs on some nitrogen atoms in phenformin hydrochloride is inferred from the presence of a hydrogen catalytic polarographic wave. This finding emphasizes the ability of biguanides to form hydrogen bridges with other molecular species such as amino acids and proteins, as well as to form coordination complexes with zinc and other metallic cations by means of these electron pairs. The antidiabetic action of phenformin and other related biguanides can be explained in terms of competition between these molecules and insulin to coordinate cationic oligoelements together with their ability to form hydrogen bonds between the biguanide moiety and insulin itself.
Voltammetric behaviour of monomeric fac-trioxomolybdenum(VI) complexes with aminocarboxylic ligands in aqueous media
1992
Abstract Cyclic voltammetry, polarography and controlled-potential coulometry experiments have been used to characterize the electrochemical reduction of fac-MoO3L2− complexes (L = aspartic acid or iminodiacetic acid) in aqueous media. These complexes are reduced in two irreversible proton-assisted steps to give an oxo-bridged molybdenum(V) species and then to a molybdenum(III) dimer species. At pH 4.5, the former reduction step for the iminodiacetic acid ligand occurs at Ep = −0.75 V, while the second one appears at −1.12 V vs SCE. The overall electrochemical process can be described in terms of a homogeneous chemical reaction, coupled between two electron transfers (ECE mechanism), that i…
Studien zum Vorgang der Wasserstoffübertragung, 47.Elektroreduktion von 1,4-Benzoldicarbonitril, 1,4-Diacetylbenzol und Terephthalaldehyd
1978
Die Elektroreduktion von 1,4-Benzoldicarbonitril in Gegenwart von Essigsaure fuhrt bei einem Stromdurchgang von 4.5 Faraday-aquivalenten/mol in 80proz. Ausbeute zu 4-Amino-methylbenzonitril (1). Bei Anwendung von 6 Faraday-aquivalenten/mol konnen geringe Mengen an 4-Methylbenzonitril (2) nachgewiesen werden. Bei der praparativen Elektroreduktion von 1,4-Diacetylbenzol in Gegenwart unterschiedlicher Mengen an Essigsaure entstehen 4-(1-Hydroxyethyl)acetophenon (3), 1,1′-(1,4-Phenylen)diethanol (4) sowie polymere Pinakole 5 in den in Tabelle 1 angegebenen Mengen. Terephthalaldehyd wird in Gegenwart von Essigsaure zu 4-Hydroxymethylbenzaldehyd (6), Terephthalalkohol (7) und einem polymeren Pina…
Electrochemical reduction of the nitrite to ammonium ions in presence of [MoO2(O2CC(S)C6H5)2]2−
1995
Abstract Ammonia is formed during potentiostatic reduction of sodium nitrite solutions on the nafion-complex-coated electrode. When (NH4)2[MoO2(O2CC(S)(C6H5)2)2] is present in NaNO2 solutions a polarographic wave is associated to electrocatalytic reduction of nitrite ion. The wave height varies linearly on the concentration of nitrite ion, allowing a procedure for analysing this ion. This electrochemical behaviour distinguishes the nitrite from the nitrate ions. The Mo(VI), Mo(V), and Mo(IV) are involved in catalytic redox processes determining formation of NH4+ from nitrite ions.
Second harmonic ac polarography of strongly adsorbed electroactive species
1981
Abstract The second harmonic ac current is calculated for the case of a quasi-reversible surface redox system: both species are strongly adsorbed according to a Langmuir isotherm and the kinetics of the process are controlled by the electron transfer. The current is measured with a phase-sensitive detector and the variation of the in-phase and quadrature components vs. the frequency leads to the surface rate constant ks. The experimental results obtained for benzo-(c)cinnoline are in good agreement with the theoretical predictions and with the results of impedance measurements. The advantages of the two methods are compared.