Deprotonation nitroxyl

At pH < 7 the nitroxyl radicals do not undergo an observable heterolysis (khs 10 s ), but decay by bimolecular reactions. However, in basic solution an OH -catalyzed heterolysis takes place to yield the radical anion of the nitrobenzene and an oxidized pyrimidine. In the case of the nitroxyls substituted at N(l) by H (i.e. those derived from the free bases), the OH catalysis involves deprotonation at N(l) which is adjacent to the reaction site [= C(6)] (cf. Eq. 15) [26] ... 

There have been several papers dealing with the oxidation reactions of nitrogen and sulfur-based compounds. Hindered amines, such as substituted 2,2,6,6-tetramethylpiperidines, are easily oxidized by electron-transfer reactions to the corresponding cation, by the sulfate radical anion, and by sensitized electron transfer to carbonyl triplets. Radicals derived from tertiary piperidines were observed directly by optical spectroscopy and deprotonated to a-alkylamine radicals. The amine radical cation derived from secondary piperidines deprotonated to give aminyl radicals. In the presence of oxygen, both classes were oxidized to give nitroxyl radicals, but by different proposed mechanisms. Both oxidation and fragmentation pathways have been observed in the photochemical reaction of alkyl phenyl sulfides with tetranitromethane. The oxidation of various A-(arylthio)-4-substituted-2,6-diarylanilines (18) with PbOa yielded, in most cases, persistent radicals that could... 

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