Peroxides, also

Because many organic peroxides undergo thermolysis to form useful free radicals, they are used commercially as initiators for free-radical reactions. Many organic peroxides also undergo reactions in which free radicals are not involved, eg, heterolyses, hydrolyses, reductions, and rearrangements. Numerous reviews of the chemistry and appHcations of organic peroxides have been pubHshed (11,13—41). 

DiaLkyl peroxides also undergo nucleophilic displacements by organometaUic compounds ... 

These peroxides also form 1 1 adducts with styrene and form hydroben2oin diarenesulfonates with stilbenes. Di(ben2enesulfonyl) peroxide decomposes in water to phenol and sulfuric acid (33). 

Other unsymmetrical peroxides can be prepared by this reaction by employing other acylating agents, eg, alkyl chloroformates, organosulfonyl chlorides, and carbamoyl chlorides (210). Unsymmetrical and symmetrical di(diacyl peroxides) also are obtained by the reaction of dibasic acid chlorides directiy with peroxycarboxyhc acids or monoacid chlorides directiy with diperoxycarboxyhc acids in the presence of a base (44,187,203). 

Chlorine DiLV i-.le 10049-04-4 1000 Ethyl Methyl Keior.e Peroxide (also Methyl Ethyl KetonePeroxide concentration greater than 60%) 1. 4 51M10... 

Oxygen bleaches such as sodium carbonate peroxide (also called sodium percarbonate), sodium peroxide, or sodium perborate are made by reacting molecules with hydrogen peroxide. When the result is added to water, the hydrogen peroxide is released. 

The sulfur analog of hydrogen peroxide also exists and is an example of a polysulfane, a catenated molecular compound of composition HS—S —SH, where n can take on values from 0 through 6. The polysulfide ions obtained from the polysulfanes include two ions found in lapis lazuli (Fig. 15.15). 

Take special notice of what we can accomplish when we use this technique it gives us the power to move the position of a double bond. When using this technique, we must carefully consider the regiochemistry of each step. In the first step (addition), we must decide whether we want a Markovnikov addition (HBr), or an anti-Markovnikov addition (HBr with peroxides). Also, in the second step (elimination), we must decide whether we want to form the Zaitsev product or the Hofmann product (which we can control by carefully choosing our base, ethoxide or fcrf-butoxide). Get some practice with this technique in the following problems. 

Strong oxidants, fuming nitric acid or sodium peroxide, also cause the immediate ignition of hydrogen sulphide. 

Organic peroxides also are suitable for gel breaking [462]. The peroxides need not be completely soluble in water. The time needed to break is controlled in the range of 4 to 24 hours by adjusting the amount of breaker added to the fluid. 

Ascorbate is known to act as a water-soluble antioxidant, reacting rapidly with superoxide, hydroxyl and peroxyl radicals. However, reduced ascorbate can react non-enzymatically with molecular oxygen to produce dehydroascorbate and hydrogen peroxide. Also, ascorbate in the presence of light, hydrogen peroxide and riboflavin, or transition metals (e.g. Fe, Cu " ), can give rise to hydroxyl radicals (Delaye and Tardieu, 1983 Ueno et al., 1987). These phenomena may also be important in oxidative damage to the lens and subsequent cataract formation. 

Indeed, when present in concentrations sufficient to overwhelm normal antioxidant defences, ROS may be the principal mediators of lung injury (Said and Foda, 1989). These species, arising from the sequential one-electron reductions of oxygen, include the superoxide anion radical, hydrogen peroxide, hypochlorous ions and the hydroxyl radical. The latter species is thought to be formed either from superoxide in the ptesence of iron ions (Haber-Weiss reaction Junod, 1986) or from hydrogen peroxide, also catalysed by ferric ions (Fenton catalysis Kennedy et al., 1989). 

Dyeing cotton yarn with selected direct dyes and simultaneous bleaching with peroxide. It is claimed that the peroxide also increases the colour yield [324]... 

Interaction gives the extremely explosive poly(ethylidene) peroxide, also formed on warming peroxidised diethyl ether. 

Mercuric carboxylates, which decarboxylate by a chain mechanism when initiated by peroxides, also decarboxylate under UV irradiation (123,128,129,131-140,142,144-146,153-155). In addition, decarboxylation was observed for mercuric benzoate and mercuric a-naphthoate (123). Side reactions [Eqs. (24), (25), (109)] observed in peroxide initiated reactions also occurred on UV irradiation, and mercurous salt formation [Eq.(24)] was more extensive under the latter conditions. Decarboxylation giving methylmercuric acetate occurred on irradiation of mercuric acetate in aqueous solution and is considered to be of environmental significance (156,157). Stepwise decarboxylation giving (CF3)2Hg occurred on irradiation of solid mercuric trifluoroacetate at -196° C (158), but, at 20° C, trifluoromethyl radicals diffused from the solid and dimerized (158). No other diorganomercurial has been formed by radical decarboxylation, and the reaction is not preparatively competitive with the thermal decarboxylation synthesis of (CF3)2Hg (26,27) (Section III,A). 

Monomers, such as styrene or methyl methacrylate, are oxidized to oligomeric peroxides also [107] ... 

In addition to the aforementioned dusts and fibers, coal mine dusts may also stimulate oxygen radical production [199], In this case hydroxyl radical production and lipid peroxidation also correlated well with the content of available surface iron. It has been proposed that free radical-mediated processes can be a casual cause of coal workers pneumoconiosis due to exposure to coal dusts. 

Carbamate nerve agents are readily destroyed by high pH (i.e., basic solutions). Use an aqueous caustic solution (minimum of 10% by weight sodium hydroxide or sodium carbonate) or use undiluted household bleach. Basic peroxides also rapidly detoxify carbamate nerve agents. 

The guide to safe handling and storage of peroxides also contains a comprehensive bibliography of detailed information [1], The earlier publication contains tabulated data on fire and explosion hazards of inorganic peroxides [2],... 

Like other peroxides, also dioxetanes are sensitive to the presence of metal ions and their complexes, which catalyze the decomposition of the dioxetane molecule. In most cases, this decomposition is dark, i.e. no chemiluminesce is generated in such a catalytic cleavage42. An informative exception, for instance, constitutes the chemiluminescent decomposition of the dioxetane 19 in Scheme 13, initiated by the ruthenium complex Ru(bipy)3Cl243. It has been shown that this chemiexcitation derives from the valence change of the ruthenium ion in the process Ru3+ I e — Ru2+, for which the efficiency of the excited-state generation may be as much as 40%44. Hence, when the radical anion of the carbonyl cleavage fragment from the dioxetane and the Ru3+ ion are formed in... 

---