Radical reactivity of 2,2,6,6,-tetramethylpiperidine derivatives: A kinetic ESR study

Significant aspects of the free radical chemistry of 2,2,6,6,-tetramethylpiperidine derivatives (HALS) which are of interest in respect to the mechanism of inhibition of polyolefin photo-oxidation have been elucidated by performing an ESR study of the reactions initiated by t-butoxyl radicals. With unsubstituted 2,2,6,6,-TMP the preferred site of the H-abstraction is the NH bond; this selectivity is preserved also when activated CH bonds adjacent to ester groups are present. The reactions of the aminyl radical products with the parent molecules and other reactive compounds have been followed by kinetic ESR and their rate constants and activation energies measured.