Oxidation by metal ions and

Oxidation of carbon monoxide by metal ions and homogeneous catalysis of the water gas shift reaction and related processes. J. Halpern, Comments Inorg. Chem., 1981,1, 3-15 (42). 

I.3.4.2. Intermolecular Cycloaddition at C=X or X=Y Bonds Cycloaddition reactions of nitrile oxides to double bonds containing heteroatoms are well documented. In particular, there are several reviews concerning problems both of general (289) and individual aspects. They cover reactions of nitrile oxides with cumulene structures (290), stereo- and regiocontrol of 1,3-dipolar cycloadditions of imines and nitrile oxides by metal ions (291), cycloaddition reactions of o-benzoquinones (292, 293) and aromatic seleno aldehydes as dipolarophiles in reactions with nitrile oxides (294). 

Our results clearly show that modification of the electronic state of titanium oxide by metal ion implantation is closely associated with the strong and longdistance interaction which arises between the titanium oxide and the metal ions implanted, as shown in Fig. 13, and not by the formation of impurity energy levels within the band gap of the titanium oxides resulting from the formation of impurity oxide clusters which are often observed in the chemical doping of metal ions, as shown in Figs. 6 and 13. 

Furthermore, as shown in Fig. 10.2, such red shifts in the absorption band of the metal ion-implanted titanium oxide photocatalysts can be observed for any kind of titanium oxide except amorphous types, the extent of the shift changing from sample to sample. It was also found that such shifts in the absorption band can be observed only after calcination of the metal ion-implanted titanium oxide samples in 02 at around 723-823 K. Therefore, calcination in 02 in combination with metal ion-implantation was found to be instrumental in the shift of the absoiption spectrum toward visible light regions. These results clearly show that shifts in the absorption band of the titanium oxides by metal ion-implantation is a general phenomenon and not a special feature of a certain kind of titanium oxide catalyst. 

Our results clearly show that modification of the electronic state of titanium oxide by metal ion-implantation is closely associated with the strong and long distance interaction which arises between the titanium oxide and the metal ions... 

In many cases it is not known unambiguously which of these two mechanisms is operative. The pathway involving ligand deprotonation is most favoured by high oxidation state metal ions, and is relatively well-established for complexes of metal ions such as pla-tinum(iv), where appropriate intermediates may be isolated, and for cobalt(m), where there is very convincing kinetic evidence for the involvement of such deprotonated intermediates. The careful design of experiments and the selection of the correct complexes is crucial in this area of study. 

These concepts are important for an understanding of the roles played by metal ions and their complexes in the catalysis of oxidation reactions via homo-lytic mechanisms. Thus, metal complexes may function as catalysts by interfering with any of the various initiation, propagation, and termination steps outlined earlier. 

Greatorex D., Kemp T. J. Electron spin resonance studies of photo-oxidation by metal ions in rigid mediaat low temperatures. Part 3. Ce(IV) photo-oxidations of aldehydes, ketones, esters and amides. J. Chem. Soc., Faraday Trans. 1972 68 (1) 121-29. 

Ascorbic acid is a strong two-electron reducing agent that is readily oxidized in one-electron steps by metal ions and metal complexes in their higher valence states. An inner sphere mechanism for the stoichiometric oxidation of ascorbic acid by ferric ion in acid solution is illustrated by Scheme 1(8). The first step in the reaction is the formation of a monoprotonated Fe(III) complex similar to the monoprotonated ascorbate complexes listed in Table I. The intermediate monoprotonated Fe(III) complex is short-lived and rapidly undergoes an intramolecular one-electron transfer to give a deprotonated Fe(II) complex of the ascorbate radical anion, indicated by 7. This complex dissociates to the free radical anion, which may then combine with a second ferric ion to form the complex 9. Complex 9 in turn undergoes a second intramolecular electron... 

Unhke the hydrophobic mechanism that forms Afi fibrils, metal-induced A precipitation proceeds through two pathways- 1. reversible, ionically-mediated oligomerization, 2. Cu-mediated A oxidation and cross-finking. High affinity chelators both inhibit and reverse Afi precipitation induced by metal ions, and dissolve deposits from post-mortem human brain tissue [ 143,183] (Table 2). A also recruits the contaminating metal ions in ordinary laboratory buffers to form the micronuclei that seed the precipitation of peptide solutions into fibrils. Therefore, even the formation of fibrils in the... 

A specific free radical can be produced from a precursor molecule either in an initiation step or a propagation step in which a reagent radical reacts with the precursor. Initiation requires either removal or addition of an electron or homolysis. Chemically this can be done in a number of ways, by using one-electron oxidants or reductants or by inducing homolysis in some way examples of these types of reactions include autoxidation [84-86], photochemical oxidation and reduction [87-90], and oxidation and reduction by metal ions and their complexes [91-93], In propagation reactions, the reagent radical might be the hydroxyl radical, the hydrated electron, or any other suitably reactive species that will interact with the precursor molecule in the desired manner. We will consider initiation reactions first. 

The hydroperoxide decomposes both to molecular products (acetic acid and acetaldehyde) and to free radicals (formation of HO is suggested) which attack ketone molecules. Thus the overall rate of oxidation is much higher them that of enol oxidation by metal ions. 

A wide variety of interrelated homogenous gas-phase, solution-phase, and heterogenous chemistry may ultimately result in oxidation of SO2 to sulfuric acid in DUV exposure tools. The three main possible reaction pathways for the oxidation of sulfur dioxide to sulfuric acid in the exposure chamber may include (i) direct oxidation of sulfur dioxide by stable atmospheric oxygen, (ii) catalyzed oxidation of sulfur dioxide by metal ions, and (iii) photochemical oxidation of sulfur dioxide by ozone and hydroxyl radical. 

SilyIated- 1,3-dithianes are intennediate in the preparation of the lal e HCX)2SiMe3, and can be readily oxidised to acylsilanes, while the stannyl analogues give cation radical on oxidation by metal ions. ... 

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