Reduction with stoichiometry

Fabrication techniques, especially the preparation of thin films of functional materials, have made major progress in recent years. Thin-film solid electrolytes in the range of several nanometers up to several micrometers have been prepared successfully. The most important reason for the development of thin-film electrolytes is the reduction in the ionic resistance, but there is also the advantage of the formation of amorphous materials with stoichiometries which cannot be achieved by conventional techniques of forming crystalline compounds. It has often been observed that thin-film electrolytes produced by vacuum evaporation or sputtering provide a struc-... 

The P-cluster, located at the interface of MoFe-protein s a- and (3-subunits, is believed to function as the electron transfer mediator between Fe-protein and the N2 reduction site at the M center. The P-cluster is contained within a hydrophobic environment and located approximately 10 A below the MoFe-protein surface. Three cysteine side chains from each subunit bind to iron ions in the P-cluster. The cluster is now known to exist in Pox and PN forms in active enzyme, both with stoichiometry FegS7. The PN form, with its octahedrally coordinated central sulfur, has the structure shown in Figure 6.6. As can be seen in Table 6.3, the PN form contains all ferrous irons, corresponding to the P (5 = 0) state, whereas the Pox form corresponds to the P2+ (5=3 or 4) form. 

Mechanism, Stoichiometry and Stereochemistry of Reductions with Hydrides... 

The stoichiometry of lithium aluminum hydride reductions with other compounds such as nitriles, epoxides, sulfur- and nitrogen-containing com-... 

Hydroperoxides undergo reduction with aqueous Fe(II), which turns to aqueous Fe(III). The reaction can be followed at 305 nm (e = 2095 M cm ) ° . Although the stoichiometry of this process is straightforward, with two Fe(II) ions being consumed per molecule of hydroperoxide, the mechanism involves an alkoxide free radical, RO", that may undergo -elimination, H abstraction from R—H, or a 1,2-H-shift and reaction with other components in the system. A case in point is the determination of f-butyl hydroperoxide which consumes under 1 mol of Fe(II) per mol of analyte under inert gas cover, while in the presence of O2 four mols are consumed, pointing to extensive side reactions of the RO" free radical, both without and with O2 in the system. ... 

Reduction of elemental selenium with Sml2 leads to the selective formation of Se and Se depending on the reaction stoichiometry, similar to the reduction with NaBH4 and hydrazine (Sects. 2.2.2 and 2.2.3). These inorganic dianions react with alkyl bromides to produce dialkyl selenides and diselenides, respectively, in excellent yields (Scheme 15) [17a]. 

The Chilean niter deposits contain up to 0.3% iodine in the form of calcium iodate. After dissolution and recrystallization of the niter, the supernatant liquor contains up to 9 g/L of sodium iodate. Iodine is liberated by reduction with sulfur dioxide (in the form of sodium bisulfite), further reduction to iodide being avoided by maintaining stoichiometry ... 

Reductants with the next stable oxidation state two units higher are formally two-electron reductants e.g., Sn(ll), T1(I) and Pt(II). Reactions of Pt(II) usually are with Pt(lV) complexes and as a result have the stoichiometry of substitution processes (the reduction of Au(lII) by Pt(Il) occurs]. The major problem in assessing reactivity patterns in these reactions is the variety of rate laws and paucity of data. Because noncomplementary reactions produce unstable oxidation states that react by a variety of mechanisms, rate laws are often not comparable reactivity patterns are highly dependent on the oxidant in ways that are not yet analyzable. 

The spectral and potentiometric characteristics of type b cytochromes in a succinate-cytochrome c reductase, prepared from pigeon breast muscle mitochondria using a mixture of ionic and nonionic detergents, have shown a close resemblance to those in intact mitochondria 8,34,37). The succinate-cytochrome c reductase may be fractionated into two complexes, succinate-ubiquinone reductase and ubiquinone-cytochrome c reductase, so-called complexes II and III, respectively. Complex III contains type b cytochromes, cytochrome c, and nonheme iron protein in a stoichiometry of 2 1 1 (38). One of the type b cytochromes shows an a peak at 562 nm (559.5 nm at 77°K) by the reduction with succinate and is identified as cytochrome b. The other, with the a peak at 566 nm (562.5 and 554 nm at 77°K), is reduced by succinate only in the presence of antimycin or by dithionite and is identified as cytochrome bi- These two cytochromes do not combine with CO. 

A general feature of these reactions, in which platinum reacts with monoelectronic reagents, is to undergo oxidation-reduction with formation of labile platinum(III) intermediates. These reactions can involve reduction of platinum(IV) complexes or oxidation of platinum(II) complexes, and the stoichiometry of these two sets of reactions is shown in equation (559). ... 

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