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Stabilizer 260 provided about 700/0 of the photostability achieved with 56 (R == H) (110).

Data on chemical reactions of phenolic HAS are rare. Additive 259 photolyses and yields the respective phenoxyl. The corresponding aminyl radical was not detected (15). This indicates a preferential reactivity of the phenolic moiety in comparison with the tertiary amine moiety in the alkylperoxyl-rich environment. The regenerative quinone methide-+phenol mechanism analogous to the rearrangement of 112-+113 has been considered for oxidized 260 containing a propionate-type phenolic moiety in its molecule.