The reaction of nitroxyl radicals with hydroperoxides

In presence of traces of strong acids 2,2,6,6‐tetramethylpiperidine‐N‐oxyl (2) induces the decomposition of hydroperoxides such as tert‐butyl hydroperoxide (1) and cumene hydroperoxide (CHP). 2 disproportionates in presence of hydrogen chloride into 1‐hydroxy‐2,2,6,6‐tetramethylpiperidine (5) and 2,2,6,6‐tetramethyl‐1‐oxopiperidinium chloride (4). This oxammonium salt is the active component which catalyses the decomposition of the hydroperoxide 1 by forming alkylperoxy radicals and the hydroxylamine derivative 5. The peroxy radicals are converted into alkyloxy radicals and molecular oxygen, and the oxyradicals regenerate 2 and an alcohol. The concentration of 2 remains constant through the whole period of the reaction. If 1 is present in an excess over 2 and the oxammonium salt 4, additional protons are needed to decompose the hydroperoxides.