38951-80-3Relevant academic research and scientific papers
One-electron oxidation of sterically hindered amines to nitroxyl radicals: Intermediate amine radical cations, aminyl, α-aminoalkyl, and aminylperoxyl radicals
Brede,Beckert,Windolph,Goettinger
, p. 1457 - 1464 (1998)
Sterically hindered amines (2,2,6,6-tetramethyl-substituted piperidines) are easily oxidized (i) by electron transfer to parent cations in n-butyl chloride solution, (ii) by the sulfate radical anion in aqueous solution, and (iii) by sensitized electron transfer to carbonyl triplets. In nonpolar surroundings in the nanosecond time range, the radical cations of the tertiary piperidines have been directly observed by optical spectroscopy to exhibit absorption maxima below λ = 300 nm and around 550 nm. Subsequently, they deprotonate to α-alkylamine radicals, which are also the first observable products of oxidation with sulfate radical anions in water. In the case of secondary piperidines, the amine radical cations deprotonate to aminyl radicals in times 8 M-1 s-1) for several alkyl radicals and for the tert-butyloxyl radical and less than 105 M-1 s-1 for alkylperoxyl radicals. Because of the minor importance of radical reactions with the sterically hindered amines (HALS), the antioxidant effect of these compounds ought to be explained by oxidation, primarily via cationic and subsequently radical intermediates to the persistent nitroxyl radicals, which scavenge other radicals very efficiently.
