Scavenging by oxygen

Both phenyl radicals and arsenic-containing radicals seem to be involved. Both can be scavenged by oxygen present either in the atmosphere or in the compound itself. 

Some 6% of this is susceptible to further thermal reaction with phenyl groups unless scavenged by oxygen to form PhAsO(OH)j. 

The hypothesis that electron scavenging by oxygen or other oxidants is faster than electron-hole recombination is perhaps too restrictive, as it is now recognized that this reaction, in particular with oxygen, can be rather slow (see Ref. 19 and the values of estimated rate constants in Ref. 41). When 0x2 acts as a mere electron scavenger, reaction (Ig) could be neglected. The rate... 

Electron scavenging by oxygen species in competition with eqn. (53a) was identified as the origin of the sensitivity of this photoassisted redox-type mechanism towards added oxygen. 

The radicals Caq and H are scavenged by oxygen and do not interfere. Unfortunately, hexacyanateferrate(n) solutions can only be used to measure g(OH) up to 105 C because of their thermal instabiUty. In order to extend the temperature range to 300 C, Elhot et al. [3] measured G(C03 ) from aerated solutions of hydrogencarbonate where reaction (4) replaces (3) ... 

The use of neutralising amines in conjunction with an oxygen scavenger—metal passivator improves corrosion control in two ways. First, because any acidic species present is neutralized and pH is increased, the condensate becomes less corrosive. Second, most oxygen scavenger—passivators react more rapidly at the mildly alkaline conditions maintained by the amine than at lower pH levels. For these reasons, this combination treatment is gaining wide acceptance, particularly for the treatment of condensate systems that are contaminated by oxygen. 

Superoxide is a free radical form of oxygen (02 ) that is damaging to cells. Superoxide is scavenged by the enzyme superoxide dismutase used by neutrophils to destroy microbes in the body. 

The FW oxygen scavengers mentioned earlier are volatile and can therefore provide additional protection against post-boiler section corrosion induced or enhanced by oxygen in-leakage. These particular scavengers also break down under pressure to produce some level of volatile ammonia, which can neutralize any carbon dioxide found in the steam-condensate system. 

It is interesting to note that scavenging of radicals can be done by oxygen atoms from the target compound itselT. ... 

These reactions demonstrate the Brflnsted base role of adsorbed oxygen perviously found on Ag(llO) and show further that more active transition metals which themselves activate C-H bonds catalytically oxidize via a two-step mechanism in which the surface intermediates are scavenged by adsorbed oxygen. 

Nunes, F.A., Kupperman, D., Kumar, C., Chance, B. and Brass, C.A. (1992). Increased chemiluminescence upon rcper-fusion of ischaemic rat liver is attenuated by oxygen radical scavengers and allopurinol. Hepatology 16, 160A. 

A dinitrosyl (NO)2 species forms, whose dissociation leads to N2 the remaining adsorbed oxygen species have to be scavenged by the activated reductant, C, HvOz to recover the free active site, permitting the catalytic cycle to turn over (Figure 5.1, function 3) [10]. 

Similar results have been obtained over alumina alone, in the presence of propene [27], The initial HC of the feed (propene) has to first transform to oxygenates (alcohol, aldehyde, etc.) - simultaneously to the NO decomposition (function 3) - to scavenge adsorbed oxygen species left by NO decomposition and regenerate the active sites of function 3. The mild oxidation of HC to oxygenates is the role of function 2 of the present model. 

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