Lead oxide modification

The use of sofid supports in conjunction with permanganate reactions leads to modification of the reactivity and selectivity of the oxidant. The use of an inert support, such as bentonite (see Clays), copper sulfate pentahydrate, molecular sieves (qv) (151), or sifica, results in an oxidant that does not react with alkenes, but can be used, for example, to convert alcohols to ketones (152). A sofid supported permanganate reagent, composed of copper sulfate pentahydrate and potassium permanganate (153), has been shown to readily convert secondary alcohols into ketones under mild conditions, and in contrast to traditional permanganate reactivity, the reagent does not react with double bonds (154). 

A recent development is the introduction of ZGS (Zirconia Grain Stabilised) platinum. This is produced by the addition of a small amount of zirconia (zirconium(IV) oxide) to molten platinum, which leads to modification of the microstructure of the solid material with increased hot strength and greater resistance to chemical attack. Whereas the recommended operating temperature for pure platinum is 1400 °C, the ZGS material can be used up to 1650 °C. 

Synonyms lead(ll) oxide yellow lead oxide litharge (red alpha modification of the oxide) massicot (yellow beta form)... 

The red lead oxide (the tetragonal alpha modification) is obtained by slow cooling of the lead monoxide melt. The sohdified mass may contain the red alpha form of the oxide resulting from slow cooling of the melt, under an outer layer of yellow beta form that may result from the rapid cooling of the outer portion. 

It is estimated that the average daily intake is about 14 mg, but the increasing use of highly refined foods may lead to dangerously low consumption. Recent interestd f has been aroused by studies that show that much larger amounts of vitamin E (e.g., 100-400 mg/day) substantially reduce the risk of coronary disease and stroke in both womens and menh and also decrease oxidative modification of brain proteins.1 The decrease in heart attacks and stroke may be in part an indirect effect of the anticlotting... 

Azoxybenzene has been prepared by reduction of nitrobenzene with alcoholic potassium hydroxide,1 with sodium amalgam,2 with hydrogen in the presence of lead oxide,3 with methyl alcohol and sodium hydroxide,4 with sodium methylate and methyl alcohol,5 and by electrolytic reduction 6 by oxidation of azobenzene with chromic anhydride 7 by treatment of /9-phenylhydroxylamine with alkaline potassium permanganate,8 with nitrobenzene,9 with mineral adds,10 and with mercury acetamide,11 and by oxidation of aniline with hydrogen peroxide,12 and with acid permanganate solution in the presence of formaldehyde.13 The procedure described above is a slight modification of one described in the literature.14... 

In vitro studies have shown that homocysteine can undergo autoxidation, leading to the formation of oxygen free radicals (30-32). Homocysteine is involved in oxidative modification of low-density lipoprotein in vitro (33). Increased lipid peroxidation in humans with hyperhomocysteinemia has been reported (34,35). However, vitamin supplementation that resulted in substantial reduction of tHcy concentrations did not normalize either the homocysteine redox status or the increased lipid peroxidation in CAD patients (35,36). 

Oxidative modification of proteins renders them more susceptible to proteolytic attack and enzymic hydrolysis (Wolff et al., 1986 Davies, 1987). Hence, if generation of active oxygen species occurs significantly in vivo, one consequence may be accelerated hydrolysis of damaged proteins. Therefore, radical generation at inappropriate sites may lead to destruction of the protein and pathological tissue degradation. 

Comparison of the cyclovoltammetric curves recorded for carbon fibers (CF) in both aqueous and nonaqueous solutions provided evidence of a considerable decrease in double electric layer capacity with increase in CF carbonization temperature (particularly between 1100 and 1400°C) [21,204]. This observation applies to both unmodified and oxidized carbon fibers. Oxidative modification leads to the appearance of a broad anodic peak with a potential between 0.1 and 0.3 V in neutral aqueous solutions (see Fig. 16a). The ab.sence of any peak on CV curves recorded in acetonitrile solutions (Fig. 16b) suggests that functional... 

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