Chemically induced oxidative reactions

Chemical Antioxidant Systems. The antioxidant activity of tea extracts and tea polyphenols have been determined using in vitro model systems which are based on hydroxyl-, peroxyl-, superoxide-, hydrogen peroxide-, and oxygen-induced oxidation reactions (109—113). The effectiveness of purified tea polyphenols and cmde tea extracts as antioxidants against the autoxidation of fats has been studied using the standard Rancimat system, an assay based on air oxidation of fats or oils. A direct correlation between the antioxidant index of a tea extract and the concentration of epigallocatechin gallate in the extract was found (107). 

Chemically Induced Oxidative Electron-Transfer Reactions... 

ChemicallY Induced Oxidative Electron-Tranter Reactions 11169... 

Chemically induced ET reactions rely on complex sequences in which the solvent, and in particular water, plays a key role [3b], Solvent molecules may (and usually do) modify the structure of the ET reagent, and thus the oxidizing/reducing potentials. The many influences of water can be illustrated by the modulation of the efficiency of the oxidation of an enamine by CAN. Indeed, a small amount of water (ca. 0.3 equiv.) is necessary to ensure catalytic turnovers, while an excess of water shifts the equilibrium towards aldehyde and free catalyst. In the heterogeneous system water also determines the stationary concentration of CAN, which remains mainly insoluble in the reaction mixture, finally, water can also participate in the reaction as cation scavenger, as was seen, for example, in the capture of the putative sUyl-cation intermediate in the aUylation reaction (see below). 

Chemically Induced Oxidative Bectron-Tran er Reactions 11179... 

Oxidation of a metal or alloys to its (lower energy state) oxides or cations. In effect, the wastage or other damage to a metal caused by one or more of several types of chemical or electrochemical reactions. Takes many forms such as galvanic, crevice, pitting, underdeposit, and biologically induced corrosion. 

Depending on the fabrication techniques and deposition parameters, the pH sensitive slope of IrOx electrodes varies from near-Nemstian (about 59 mV/pH) to super-Nemstian (about 70mV/pH or higher). Since the compounds in the oxide layers are possibly mixed in stoichiometry and oxidation states, most reported iridium oxide reactions use x, y in the chemical formulas, such as lr203 xH20 and IrOx(OH)y. Such mixed oxidation states in IrOx compounds may induce more H+ ion transfer per electron, which has been attributed to causing super-Nerstian pH responses [41],... 

Despite the many failures encountered over the last decades in up-scaling photochemical reactions, industrial preparative photochemistry has not lost its image as an attractive tool for the synthesis of fine chemicals. Reaction conditions (solvent, temperature, work-up procedures) are, in general, quite flexible and facilitate implementation of such processes on an industrial scale in terms of environmental protection. In addition, light-induced oxidation processes exhibit a very promising potential for the chemical treatment of contaminated surface and ground waters, as well as for liquid and gaseous industrial waste. 

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