Radical stability nitroso-compounds

Spin traps come in basically two types nitroso compounds and nitrone compounds. Reactive free radicals react with the carbon of the nitrone functional group to form a radical adduct that always has a nitroxide group, which is an unusually stable type of free radical. Nitrones are the most useful spin traps for the in vivo detection of free radical metabolites because of the stability of the resulting radical adduct. However, identification of the parent radicals can be difficult because adducts derived from different radicals often have very similar EPR spectra. A comprehensive review of this area through 1992 has recently been published [48]. 

It seems that the stability of the radical can play an important role. Thus nitroso compounds easily yields N=(, a stable radical. 

The ease of the above reaction is evidently associated with the relative stability of the t-butyl radical which facilitates the fragmentation of (47). Other nitroxides can, however, be obtained by less direct reductive methods in particular, they are formed by the reaction of Grignard reagents with both nitroso compounds (Maruyama, 1964) and nitro compounds (Briere and Rassat, 1965). A possible mechanism for the latter reaction has been suggested (see also Hofmann et al., 1964b). 

The ways of getting around this problem involve increasing the lifetime of the radicals by some physical or chemical means. One such approach involves stabilizing the radicals by immobilization, for example, by freeze-quenching a reaction mixture [80]. The disadvantage of this method is that an immobilized radical is generally much harder to characterize and identify than one in fluid solution. Other approaches make use of the chemical reactivity of radicals, for example, their ability to add to the double bonds in nitrones and nitroso compounds. This has led to the development of the spin-trapping procedure [81,82], in which a transient radical is reacted with the... 

Action of aromatic nitro compounds on polymerization Reduction of aromatic nitro compounds Formation of nitroso compounds Reduction of aromatic ring Diazotization of amino nitro compounds 13-Cycloaddition of nitro compounds Thermal stability of aromatic nitro compounds Free radicals Furoxancs References... 

ESIPTmechanism (see Section 93.2.2) can no longer be repeated. Regarding hindered amine stabilizers, depletion is caused by the reaction of acyl radicals, stemming from Norrish reactions, with nitroxyl radicals. Nitroso and nitro compounds (see Chart 9.16) are formed when nitroxyl radicals are photolyzed (117]. 

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