Oxidation-reduction comparisons

Lanthanide-actinide bonding and oxidation-reduction comparisons 274... 

Lanthanide-actinide oxidation-reduction comparisons in aqueous (uncomplexed,... 

In this section only coordination and complexing (sharing of electron pairs, i.e., acid-base effects) are considered. Oxidation-reduction comparisons (transfer of electrons) are made in sections 4.4 and 4.5. 

Oxidation-reduction comparisons in ionic systems 4.4.1. Binary oxides and halides... 

Co(Y)CP and Co(HY)Cl react with Fe " " at comparable rates. Comparisons are instructive between this redox reaction and other cation-catalysed chloride-abstraction reactions which occur without simultaneous oxidation-reduction. The intimate mechanisms are likely to be... 

Marcus RA (1963) On the theory of oxidation-reduction reactions involving electron transfer. V. Comparison and properties of electrochemical and chemical rate constants. J Phys Chem 67 853-857... 

As for chemical reactions, the oxidation-reduction (redox) reactions in homogenous medium (i.e., in the bulk of the solution) have been experimentally studied with proper intensity only in the last two decades. There has been some development of the bulk reactions. However, as before, a comparison of one and the same compound in chemical and electrochemical electron-charge-transfer reactions is still of current interest. Such a comparison is made in this section. The examples offered are intended to invoke novel interpretations or to discover new colors in pictures that have already been drawn. 

Ortmans I, Moucheron C, Kirsch-De Mesmaeker A (1998) Ru(ll) polypyridine complexes with a high oxidation power. Comparison between their photoelectrochemisty with transparent SnC>2 and their photochemistry with desoxyribonucleic acids. Coord Chem Rev 168 233-271 Ozawa T, Ueda J, Flanaki A (1993) Copper(ll)-albumin complex can activate hydrogen peroxide in the presence of biological reductants first ESR evidence for the formation of hydroxyl radical. Biochem Mol Biol Int 29 247-253... 

Holm, T.R. and Curtiss, C.D. (1989) A comparison of oxidation-reduction potentials calculated from the As(V)/As(III) and Fe(III)/Fe(II) couples with measured platinum-electrode potentials in groundwater. Journal of Contaminant Hydrology, 5(1), 67-81. 

K) -1690 10 kJ mol 1. The preparation and properties of this and other actinide (IV) complex oxides are described and are compared with other perovskites BaM03. The relative stabilities of tetravalent and hexavalent uranium in various environments are compared in terms of the oxidation-reduction behavior of uranium in geological nuclear waste storage media in perovskite, uranium(IV) is very unstable in comparison with uranium(VI). ... 

In true fermentation, the free energy drop between substrate (say glucose) and anaerobic end products is always modest by comparison with respiration, because fermentation is never based on electron transfer chains coupled to phosphorylation. Rather, true fermentations depend upon a variety of oxidation-reduction reactions involving organic compounds, C02, molecular hydrogen, or sulfur compounds. All these reactions are inefficient in terms of energy yield (moles ATP per mole substrate fermented), and, therefore, the mass of cells obtainable per mole of substrate is much smaller than with respiratory-dependent species. 

Charton (J52) has also applied the extended Hammett equation to the oxidation-reduction potentials of 5-substituted phenanthroline complexes of iron in various acidic media (95, 97, 651) and of bis-5- and 4,7-substituted phenanthroline complexes of copper in 50% dioxane (404). Thus, one should expect an overall similarity between the variations in pAa, stability constant, and oxidation-reduction potential data for the various ligands. The variations in a and )3 values found for various substitution positions and the tautomerism in the LH+ ions show that the correlation need not be good. A similar point may also be made about the comparison of data for the transoid bipyridylium ions and their cis complexes. Plots of A versus pA for various systems (95, 404) show a linear dependence to differing extents. As would be expected, the data for analogous complexes of iron (28), ruthenium (214, 217, 531), and osmium (111, 218, 220) show very good correlation. The assumption (152) that the effects of substituents are additive is borne out by these potential data, where the changes in potential on methyl substitution are additive (97). 

Nonhomogeneous behavior was also predicted by Levine and Zou (343), who began with the oxidation/reduction model of Sales et al. (272) for CO/O2 on polycrystalline Pt and introduced CO surface diffusion. This model predicted one-dimensional, stable traveling waves on the Pt surface. Because no experimental measurements have been performed for traveling waves on polycrystalline catalysts at atmospheric pressures, no comparison to experimental data was possible. 

Table 1 lists outer-sphere rate constants of these kinds. Finally, there are outer-sphere reactions in which neither reagent is substitutionally inert on the time scale of oxidation-reduction, but the outer-sphere path is chosen in the absence of a ligand capable of bridging the two reagents. Only indirect comparisons establish examples of this class. Self-exchange between Fe and Fe is such an example. The appearance of the rate law term k[Fe l(Fe ] is remarkable in other reactions of aquated metal ions, the term k [M M ][H ] is so large that the former is buried in experimen-... 

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