Ludovit Treindl

Oscillatory oxidation of Mn(II) ions by hexacyanoferrates(III) and bistability in the reductions of MnO2 by hexacyanoferrates(II) in a CSTR

Abstract A new transition metal oscillator based on the oxidation of Mn2+ ions by Fe(CN)3−6 ions in a CSTR has been found. As well as the oscillations of the absorbance of the Mn(IV) species, pH-oscillations have been observed. In the reduction of manganese dioxide by Fe(CN)4−6 ions a kinetic bistability has been described. A skeleton mechanism described recently for Mn(II)H2O2 and Mn(II)Br2 oscillators has been applied here and further developed by the idea of the catalytic activity of colloidal particles and of the assistance of the pH-value change of both main processes, i.e. of the Mn(II) oxidation by Fe(CN)3−6 ions and of the Mn(IV) reduction by Fe(CN)4−6 ions. This appears to be the first case where both sides of a reversible reaction are autocatalytic.

Oscillatory System I―, H2O2, HClO4: The Modified Form of the Bray-Liebhafsky Reaction

The kinetics of iodide ions oxidation with hydrogen peroxide in solutions of perchloric acid at temperature of 60 degrees C has been studied in detail. We have found conditions under which this reaction proceeds oscillatory. The Bray-Liebhafsky (BL) oscillatory reaction started by the oxidation of iodide ions with hydrogen peroxide is described for the first time. The described results support our assumption (Olexová, A.; Mrákavová, M.; Melichercík, M.; Treindl, L. Collect. Czech. Chem. Commun. 2006, 71, 91-106) that singlet oxygen ((1)O(2)) is an important intermediate of the BL oscillatory reaction in the sense of the Noyes-Treindl (N-T) skeleton mechanism (Treindl, L.; Noyes, R.M. J. Phys. Chem. 1993, 97, 11354-11362).

BELOUSOV-ZHABOTINSKY OSCILLATIONS DURING THE CHEMICAL OR ELECTROCHEMICAL GENERATION OF AG+ IONS

Abstract The oscillatory Belousov-Zhabotinsky reaction has been studied in the presence of Ag + ions using potentiometric and amperometric methods. Amperometrically the oscillations were followed by monitoring the anodic current at a potential of 1.0 V, which corresponds to the electrooxidation of Br − ions. In the Ag + -perturbed BZ reaction we still observe anodic current oscillations due to the electrooxidation of Br − ions more or less loosely bound in AgBr mono- or oligomers. Solid AgBr, however, has been found to be chemically and electrochemically inert in the BZ reaction. The timescale of producing electrochemically inactive AgBr precipitate is a second-order process with a rate constant of 256 M −1 s −1 .

Kinetics and Mechanism of the Autocatalytic Oxidation of Mn(II) by Bromine

The oxidation of Mn(II) by bromine is an autocatalytic reaction, which seems to be important for a detailed elucidation of chemical oscillators, based on manganese chemistry. With regard to the mechanism proposed previously, an alternative reaction mechanism is proposed, based on a micro-heterogeneous oxidation of Mn(II) ion, adsorbed on a surface of the MnO2 colloid.

Kinetics of the autooxidation of iodine with regard to the bray-liebhafsky oscillatory reaction

The kinetics of autooxidation of iodine in acidic solutions has been studied and its autocatalytic character has been observed. The proposed reaction scheme, based on the experimental results, is in accordance with the Treindl-Noyes skeleton mechanism for the Bray-Liebhafsky oscillatory reaction.

Chemical oscillators based on the oxidation of Mn(II) by some halogens

Chemical oscillators based on the oxidation of Mn(II) ions by bromine or chlorine in NaH2PO4−NaOH buffer solutions in a CSTR (continuous-flow stirred tank reactor) are described. The oscillations correspond to the two alternating processes. The first process is the oxidation of Mn(II) by HOBr or HOCl to Mn(IV) and the second one is of a micro-heterogeneous nature, consisting of the reduction of Mnc4+ and Mnc3+ centers on the surface of colloids (MnO2)col by halides.