Mechanism Of Redox Process Research Articles

Spectro-Electrochemical Properties of Pelargonidin-3-O-Glucoside

This paper presents the spectral and electrochemical properties correlated to antioxidant character attributed to anthocyans: Pelargonidin-3-O-Glucoside, Cyanidin-3-O-Glucoside, Delphinidin-3-O-Glucoside, Peonidin-3-O-Glucoside, Malvidin-3-O-Glucoside. The Anthocyans were obtained and purified from natural selective hydroalcoholic extracts using HPLC chromatography. A series of determinations through the chemical voltammetry method were performed in view of identifying the anthocyanins’ oxidation and reduction potentials. These determinations were performed in electrochemical environments with different polarities and pH, in N, N-Dimethylformamide–Ethanol-Hydrochloric acid–Water systems. The results obtained offered data regarding the stability of anthocyans in the respective media. For Pelargonidin-3-O-Glucoside we performed detailed UV-VIS spectro-electrochemical measurements, using an optically transparent thin layer electrochemical cell. The results of these determinations offered information regarding the mechanism of redox processes.

Manganese forms and their content and transformations in freshwater sediments (analytical review)

The concentrations of different manganese forms in the solid phase and pore water of freshwater sediments are discussed. Mechanisms of redox processes with participation of manganese are examined. Data on the concentration of manganese in freshwater nodules are summarized.

Mechanism of electrochemical reactions of polyaniline films formed under the conditions of cathodic oxygen reduction

Polyaniline films (further, CPANI) were obtained under the conditions of oxygen cathodic reduction in the aniline-containing solution on the electrodes of mixed indium tin oxide (ITO), graphite, and gold. CPANI films are characterized by redox processes in the potential ranges of 0.1–0.2 V and ∼0.4 V (SCE). These processes are caused by the polymer chain fragments of different structure and the ratio between the peaks corresponding to these processes varies significantly as dependent on the synthesis conditions (electrode material, stirring, etc). The mechanism of electrode processes on CPANI is studied using the methods of cyclic voltammetry and quartz microgravimetry. It is found that only hydrogen cations and supporting electrolyte anions participate in the electrode process at the potentials of 0.1–0.2 V. The mechanism of redox processes on the obtained polymer films is discussed.

Reactivity and Biological Activity of the Marine Sesquiterpene Hydroquinone Avarol and Related Compounds from Sponges of the Order Dictyoceratida

A review of results of bioactivity and reactivity examinations of marine sesquiterpene (hydro)quinones is presented. The article is focused mostly on friedo- rearranged drimane structural types, isolated from sponges of the order Dictyoceratida. Examples of structural correlations are outlined. Available results on the mechanism of redox processes and examinations of chemo- and regioselectivity in addition reactions are presented and, where possible, analyzed in relation to established bioactivities. Most of the bioactivity examinations are concerned with antitumor activities and the mechanism thereof, such as DNA damage, arylation of nucleophiles, tubulin assembly inhibition, protein kinase inhibition, inhibition of the arachidonic cascade, etc. Perspectives on marine drug development are discussed with respect to biotechnological methods and synthesis. Examples of the recognition of validated core structures and synthesis of structurally simplified compounds retaining modes of activity are analyzed.

Novel kinetics in a biomimetic redox reaction involving NADH and tetrazolium salts in aqueous micellar solutions

Aqueous micelles of Triton X-100 are shown to catalyze the redox reaction between NADH and 2- p-iodophenyl-3- p-nitrophenyl-5-phenyltetrazolum chloride (INT) at neutral pH. The reaction exhibits a first-order dependence on NADH when INT is saturating; conversely, when NADH is saturating, the dependence is strictly second-order with respect to INT. The second-order dependence of the reaction on INT is also evident in situations where micelles of a cationic detergent are used in place of Triton X-100. The available kinetic evidence indicates the transient formation of a central complex involving the addition of two molecules of INT and one molecule of NADH to a “site” on the micelle where they are held together until completion of the redox process. However, the reaction does not seem to proceed by successive 1- e − steps, suggesting that the second-order dependence on INT has no bearing on the mechanism of redox process. The transfer of reducing equivalents between NADH and INT is shown to be direct and quantitative, with the redox steps confined to a microenvironment, as in the case of enzymatic NAD(P)H-dependent reactions. A mechanism consistent with the hydridic nature of the migrating hydrogen from the C(4) position of the dihydropyridine nucleus of NADH is proposed, assuming that only one molecule of INT in the central complex participates in the actual redox process and that the other molecule of INT acts as a cocatalyst by way of providing the necessary “basicity” at the reaction site.

CO Oxidation and NO Reduction on Perovskite Oxides

Abstract The search for substitutes of noble metal supported exhaust control catalysts has led to the study of a number of perovskite oxides (1). The mechanisms of redox processes on these surfaces are topotactic in nature, thus accounting forthe reversible loss and uptake of bulk oxygen or for the concomitant creation and annihilation of vacancies rendering these systems as attractive oxidation catalysts. The variable oxygen stoichiometry of perovskite structure is responsible for the exotic behavior of these materials as a new class of high Tc superconducting oxides (2). The extreme ease of removing oxygen from the framework but still retaining the basic ingredients of the perovskite structure and the possibility of deriving different structural frameworks from ideal perovskite structure (e.g. insertion of rock salt layer between perovskite layers results in a K2NiF4 structure, while insertion of double [Bi2O2] layers between perovskite layers results in an Aurivillius phase) and the possibility of substitution of either or both A and B site cations by foreign metal ions make them function as chemical chameleons (3) with a wide variety of solid state and catalytic properties. Among the various redox catalytic processes promoted by them the oxidation of CO and the reduction of NO seem to be interesting in view of their relevance for auto-exhaust emission control. The present chapter attempts to consider the generalities that have been evolved in these studies, which will be useful for the formulation of auto-exhaust control catalysts based on perovskites in the future.