Superoxide reaction

Aminophenol was being oxidised in THF solution at 65°C using a larger than normal proportion of potassium dioxide. When stirring was stopped after 6 h, a violent explosion occurred. This was attributed to formation of tetrahydrofuranyl hydroperoxide by the excess dioxide. THF was described as an unsafe solvent for superoxide reactions [1], A later attempt at the same reaction in toluene also led to explosion, now blamed on the substrate [2],... 

It has been shown that the activity of NO synthases is regulated by cofactors calcium binding protein calmodulin and tetrahydrobiopterin (H4B). Abu-Soud et al. [149] have studied the effect of H4B on the activity of neuronal nNOS I, using the isolated heme-containing oxygenase domain nNOSoxy. It was found that nNOSoxy rapidly formed an oxygenated complex in the reaction with dioxygen, which dissociated to produce superoxide (Reaction (6)) ... 

Since glutathione is synthesized in cells in relatively huge amounts, it is seldom applied as pharmacological antioxidant. Furthermore, the mechanism of its antioxidant activity is not so simple as that of vitamins E and C. The major reason is that the GS radical formed during scavenging of free radicals by GSH does not disappear by dimerization but participates in the chain reaction, producing superoxide (Reactions (20)-(23)). Furthermore, it has recently been shown that contrary to previous findings the rate constant for the reaction of GSH with superoxide is relatively small (200-1000 lmol-1 s-1) [211,223],... 

Unfortunately, due to the above shortcomings of hydroxylamine derivatives as spin traps, the uncertainties of the mechanism of their reactions with superoxide are added. Although it is supposed that nitroxide radicals are formed by oxidation with superoxide (Reaction (6)), this reaction cannot be an elemental stage because superoxide cannot abstract a hydrogen atom. 

In the literature there are no quantitative studies on the kinetics and thermodynamics of stoichiometric superoxide reactions with metal centers in general, and metalloporphyrins in particular. More precisely, superoxide concentration and temperature dependent kinetic and thermodynamic measurements were never reported and consequently the rate constants, activation parameters or binding constants for this t5rpe of reactions (Scheme 15) are not known. (The catalytic rate constants for the superoxide disproportionation, i.e., dismutation, by metal complexes are known (see earlier), however in those measurements the concentration of a catalytic amount... 

Nitrobenzene chloride, sulfonylperoxy radical reactions, 1035, 1036 2-Nitrobenzenesulfinylperoxy intermediate, superoxide reactions, 1034 Nitrogen-containing compound oxidation bis(trimethylsilyl) peroxide reactions, 802-3, 804 dioxiranes, 1151-5 primary aromatic amines, 1151 A-oxidation, 531-8, 539 Nitrohpids, hpid hydroperoxides, 952-4 Nitronate ions, dioxirane oxidation, 1152-3 Nitrosation, malondialdehyde, 667 Nitroso compounds, spin trapping, 664 Nitrotyrosine, peroxynitiite determination, 740-1... 

Peroxysulfates, analytical aspects, 744 Peroxysulfenate, superoxide reactions, 1033 Peroxysulfinate, superoxide reactions, 1033-5 Perpendicular effect, methyl substituted-benzyl carbinyl hypochlorite photolysis, 907,... 

C-H bond unreactive to insertion, 1160 dioxirane oxidation, 1156 Sulfonic acids, C-H bond unreactive to insertion, 1160 Sulfonyl endoperoxides parasiticidal activity, 1309 synthesis, 1306-9, 1332 Sulfonyl peroxides, 1001-2, 1004-7 Sulfonylperoxy radical, superoxide reactions, 1035-9 Sulfoxidation... 

TOCO see Thiol-olefin co-oxygenation Tocopherols, TEARS assay, 668 Torsion angles, hydroperoxides, 690 Tosylhydrazones, superoxide reactions, 1036 Total hydroperoxides see Peroxide value Total oxidative capacity, titration methods, 674 Total polar phenols, colorimetry, 664 Toxicity... 

Table 8. Electrogenerated superoxide reaction with malonate esters ...

For the reduction reaction, Eq. (36), the reaction orders correspond to the superoxide reaction mechanism [9]. 

Copper in trace amounts can distort the kinetics of superoxide reactions with other compounds, because it effectively catalyses the dismutation reaction [143], Complexation by edta prevents this, as well as the reduction of hydrogen peroxide. Thus, edta protects the bases of DNA against copper-mediated damage [144]. However, edta will not protect if iron is involved, since rates of reaction between this metal complex and oxygen, superoxide or hydrogen peroxide are appreciable. 

Two families of metalloproteins are excellent catalysts for the disproportionation of superoxide (Reaction 5.95). 

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