Metal peroxides, structure

Urea-hydrogen peroxide (UHP) crystal structure, 98, 99 disilazane reactions, 814-15 transition metal peroxides, 1083, 1089-90, 1099, 1103, 1113 Uric acid... 

The present volume comprises 17 chapters, written by 27 authors from 11 countries, and deals with theoretical aspects and structural chemistry of peroxy compounds, with their thermochemistry, O NMR spectra and analysis, extensively with synthesis of cyclic peroxides and with the uses of peroxides in synthesis, and with peroxides in biological systems. Heterocyclic peroxides, containing silicon, germanium, sulfur and phosphorus, as well as transition metal peroxides are treated in several chapters. Special chapters deal with allylic peroxides, advances in the chemistry of dioxiranes and dioxetanes, and chemiluminescence of peroxide and with polar effects of their decomposition. A chapter on anti-malarial and anti-tumor peroxides, a hot topic in recent research of peroxides, closes the book. 

O EIEs of 1. 026-1.030 were computed from three experimentally determined frequencies that represent the most isotopically sensitive vibrational modes for side-on peroxide structures. This approach may be superior to the full frequency analysis specifically for the third row metals where the DFT method is less reliable. 

For oxidation, different stressing schemes can be used, and this depends generally on the structure of the drug substance (active component) autooxidation, metals, peroxide-mediated, peroxy-mediated, bubbled oxygen, and pressurized oxygen. Auto-oxidation involves a free radical initiator such as AIBN (2,2 -azobisisobutyronitrile) or AMVN (2,2 -azobis(2,4-dimethylvaleronitrile) to initiate oxidation [37] and has been used to mimic long-term room temperature degradation related to oxidation. The concentration... 

Another approach to minimizing the problem of metal peroxide dissolution was to incorporate a redox metal into a zeolite by replacing some or all of the aluminum in the framework. Of these redox zeolites, the most common catalysts for peroxide oxidations are the titanium silicalites, TS-1 and TS-2 (Chapter 10). 14,15,19-23 TS-1, the more generally used material, has a crystal structure analogous to ZSM-5 with two dimensional channels of 0.55-0.60 nm in... 

As mentioned above, much less is known about the structural characteristics and mechanisms of the nonheme metal-containing monooxygenase enzymes. From the similarities of the overall stoichiometries of the reactions and the resemblance of some of the enzymes to dioxygen-binding proteins, it is likely that the initial steps are the same as those for cytochrome P-450, i.e., dioxygen binding followed by reduction to form metal-peroxide or hydroperoxide complexes. It is not obvious that the next step is the same, however (i.e., O—O bond cleavage... 

The only mention by Vail (1) of peroxide structures in relation to silicates is the stabilizing effect of sodium silicate in combination with magnesium silicate in stabilizing peroxide bleaching baths, probably by adsorbing and inactivating traces of catalytically active metals such as copper. 

Gilbert et al. [133] employed EPR spectroscopy to monitor the initial stages in the free-radical copolymerization of carbohydrates and methacrylic acid, initiated by a metal-peroxide redox couple. The authors aimed to understand the behavior of mixed carbohydrate-monomer systems in the presence of radical initiators by gaining knowledge of the rate constants and their dependence on radical structure and different substitution patterns. 

The chromates of the alkali metals and of magnesium and calcium are soluble in water the other chromates are insoluble. The chromate ion is yellow, but some insoluble chromates are red (for example silver chromate, Ag2Cr04). Chromates are often isomorph-ous with sulphates, which suggests that the chromate ion, CrO has a tetrahedral structure similar to that of the sulphate ion, SO4 Chromates may be prepared by oxidising chromium(III) salts the oxidation can be carried out by fusion with sodium peroxide, or by adding sodium peroxide to a solution of the chromium(IIl) salt. The use of sodium peroxide ensures an alkaline solution otherwise, under acid conditions, the chromate ion is converted into the orange-coloured dichromate ion ... 

Figure S.l The enzyme superoxide dismutase (SOD). SOD is a P structure comprising eight antiparallel P strands (a). In addition, SOD has two metal atoms, Cu and Zn (yellow circles), that participate in the catalytic action conversion of a superoxide radical to hydrogen peroxide and oxygen. The eight p strands are arranged around the surface of a barrel, which is viewed along the barrel axis in (b) and perpendicular to this axis in (c). [(a) Adapted from J.S. Richardson. The stmcture of SOD was determined in the laboratory of J.S. and D.R. Richardson, Duke University.)...

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