Reactions of stabilizer compounds. III. Oxidative reactions of some 2′‐hydroxy‐2‐phenylbenzotriazole light stabilizers in the AIBN‐initiated autoxidation of cumene

Oxidative decay of number of commercially important 2′‐hydroxy‐2‐phenylbenzotriazole light stabilizers during the AIBN‐initiated autoxidation of cumene at 65°C is described. The reactivity of the hydroxyphenylbenzotriazoles studied increased in the order 2‐(2′‐hydroxy‐5′‐methyl)phenylbenzotriazole (Ia) < 2‐(2′‐hydroxy‐3′,5′ ‐di‐tert‐pentyl)phenylbenzotriazole (Ie) < 5‐chloro‐2‐(3′,5′‐di‐tert‐butyl‐2′‐hydroxy)phenylbenzotriazole (Ic) < 5‐chloro‐2‐(3′‐tert‐butyl‐2′‐hydroxy‐5′‐methyl)phenylbenzotriazole (Ib). The major product from the reaction of Ib was identified as the cumylperoxycyclohexa‐2,5‐dienone (III). The possible occurrence of these reactions during the degradation of stabilized polymers is discussed.