Oxygen anion radical

The reaction with nitrite proceeds smoothly and with relatively high yields of the corresponding nitroarene (see Sec. 10.6). Obviously a major part of the driving force of this reaction is the formation of a stable, i. e., an energetically favorable, radical, nitrogen dioxide. With the hydroxide ion — a much stronger nucleophile than the nitrite ion — the reaction is expected to produce very unstable radicals, the hydroxy radical OH and the oxygen radical anion O, from the diazohydroxide (Ar - N2 — OH) and the diazoate (Ar-N20 ) respectively. Consequently, dediazoniation in alkaline aqueous solution does not follow the simple Scheme 8-41 with Yn = OH, but instead involves diazoanhydrides (Ar — N2 —O —N2 —Ar) as intermediates (see Sec. 8.8). 

Oxygen radical anion 02( > is formed in an equilibrium reaction of the copper-cysteine-oxygen complex and a copper-cysteine complex ... 

Oxygen radical anion forms excited-singlet oxygen in different pathways, e.g. by a reaction with copper-cysteine-oxygen complex to yield the excimer (02)2- The computerized kinetic equations derived from this scheme allowed predictions in respect of the chemiluminescence intensity as a function of the oxygen and cysteine concentrations and as a function of time these were satisfactorily confirmed by the ex-... 

The lucigenin radical 78 is not involved, according to Janzen and coworkers 136), in the direct formation of this cyclic peroxide one would, however, expect a reaction of 78 with oxygen radical anion to be a possible way of forming the cyclic peroxide, although lucigenin radicals were not detected in the presence of hydrogen peroxide. 

The electrochemical reduction of oxygen in dimethylformamide generates oxygen radical-anion. This will abstract a hydrogen atom from the methyl group in a methylpyridine, the process finally leading to the pyridinecarboxyUc acid [219],... 

Van der Zee J, Dubbelman TMAR, Van SteveninckJ (1987) The role of hydroxyl radicals in the degradation of DNA by ozone. Free Rad Res Commun 2 279-284 Vieira AJSC,Telo JP (1997) EPR detection of oxygen radical anion in aqueous solution at room temperature. Redox Rep 3 349-350... 

Oxygen radical anions ( 3.8). The O center can be formed by various means on the surface, not only by doping the material with alkali metals ions. O exhibits an high chemical reactivity and can be located at low-coordinated sites as well as at regular terrace sites. 

Some aspects of the photopolymerisation kinetics of different monomers have been investigated. The photopolymerisation rate of methyl methacrylate is accelerated in the presence of oxygen when triethylamine is present . This enhanced rate is associated with the usual oxygen-amine complex which can form a variety of species such as oxygen radical anions or hydrogen peroxide to give reactive hydroxyl radicals. The rate of photopolymerisation of methyl... 

To suppress the electron and electron-hole recombination and continuously supply valence-band electron holes for an oxidative process, a sacrificial electron acceptor must be used to scavenge the electron in the conduction band [15,20], Oxygen is usually used in photocatalytic oxidation because of its ability to capture conduction-band electrons from most semiconductors [8]. The oxygen radical anion formed after the quenching of an electron is an additional oxidant, which is useful for oxidative waste degradation, but may be a source of side reactions in organic synthesis. To reduce such side reactions, the use of other electron acceptors such as methyl viologen and N2O has been reported [74]. 

High yield and selective formation of carbonyl compounds from aromatic olefins have been obtained in air-saturated acetonitrile solution [Eq.(16)] [123-125]. The combination of a radical cation of the alkene and an oxygen radical anion gives a dioxane intermediate which then undergoes cleavage. For substituted naphthalenes, the oxidative cleavage can be stopped at the side chain of one benzene ring [Eq. (17)] [126]. 

This direct conversion of benzene to phenol is of great practical importance [58c]. The surface oxygen radical anion, 0 , formed through a reaction of N7O with electrons trapped on the surface of MgO, reacts with methane at 298 K [59], The partial oxidation of ethane to ethanol and acetaldehyde over iron phosphate catalyst (573-773 K) by using nitrous oxide as an oxidant has been reported [60],... 

If oxygen is present the loose electrons are consumed for its reduction which may result in formation of oxygen radical anions and in the oxidative degradation of the polymer backbone. An irreversible degradation of conductivity of freshly prepared PPy exposed to oxygen has been reported [7]. On the other hand the relaxation of the EPs can be turned to advantage. If a metal salt is allowed to diffuse into a freshly prepared EP layer the subsequent spontaneous relaxation and reduction yields metal clusters that are finely dispersed throughout the polymer s bulk [8]. These... 

Polymer oxidation is related to the formation of an oxygen radical anion O Jand possibly other species by electron transfer from photoexcited Ti02 to molecular oxygen. A recent modifi-... 

The last dimerisation reaction is probably assumed to resemble the Russell termination step (p. 23) but it must be said that is an unlikely candidate for the typically high quantum yields of the luminol reaction. Direct reaction [76] with oxygen is observed and, instead of diazaquinone, its addition product with oxygen radical anion is assumed. An endoperoxide such as (47) is not proposed as an intermediate. 

Since there is no effect of H2O2 concentration on the integrated chemiluminescence intensity, the conclusion was drawn that oxygen radical anion activates the luminol radical anions to chemiluminescence, forming the non-radical diazaquinone perhydrate (59) ... 

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