Oxygen species, redox thermodynamic

Fig. 2. Thermodynamics of the reduction of oxygen species Potential diagram at pH 7. Figures are apparent standard redox potentials versus NHE, at pH 7. Figures used for the alkyl peroxide species at the top of the diagram are approximations derived from computations by Koppenol [19]. An upper value for the ROO /ROOH redox couple would be 1.1 V, i.e. the value derived from the trichloromethyl peroxyl radical, the strongest oxidant known among peroxyl radicals. See the discussion in the text. Note (see a) A aq -0.16 V (relative to 1 M 02) is a better reference than —0.33 V for the reversible...

The reaction thermodynamics for oxygen species are influenced by the solution matrix and its acidity. Thus, the redox thermodynamics of O2 are directly dependent upon hydronium ion activity,... 

Redox Thermodynamics for Oxygen Species Electrode material effects... 

The formation of an iron(II) phase in an excess of oxygen is quite remaiitable. Thermodynamic calculations indicate that under reaction conditions anhydrous iron(IlI)sulfate Fe2(S04)3 i the only stable compound Kinetic experiments reveal that in the catalytic redox cycle the reoxidation of the active sites is the rate-determining step The order with respect to oxygen is almost unity, whereas the order with respect to H2S is close to zero [9]. Under steady slate conditions therefore the concentration of the iron(m) species and, hence, the concentration of reactive oxygen species will be low. The high steady state surface concentration of Fe(U) species brings about the formation of the... 

Thus, it can basically be predicted imder what conditions (pH, concentration of redox species) the metal dissolution reaction (Fe —> Fe ) proceeds thermodynamically. From a practical point of view, the rate of the reaction and therefore the fate of the oxidized species (Fe ) is extremely important they can either be solvated, i.e., to form Fe (H20) complexes, and therefore be efficiently dissolved in the solution, or they can react with oxygen species of... 

Owing to the allotropic forms of oxygen, to its various redox states, and related chemical species that are thermodynamically stable or exist for kinetic reasons, a lot of redox reactions are usually described. However, many of them are not really important for the common works, particularly for those in solutions consequently, only some of them have been described here. The publications cited earlier can be searched for data useful for the calculation of Gibbs energy or potentials of particular reactions. 

Catalysts and their effects on chemical reactions aid in efficiency, effectiveness and selectivity. A recent example of current research is redox and ligand exchange reactions of the oxygenation catalyst (N,N -bis(salicylidene)ethylenediaminato)co-balt(II), Co(SALEN)2 (below), and its one-electron oxidation product, Co(salen) 2-These were investigated in DMF, pyridine, and mixtures of these solvents. Solvent effects on the potentials, the thermodynamics of cross reactions, and the distribution of Co(II) and Co(III) species as a function of the solvent composition are important considerations (Eichhorn, 1997). The results in these solvents should be compared with other work with catalysts using more environmentally benign media (Collins et al., 1998). 

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