Jean Meybeck

Photochimie des oligomeres dimeres et trimeres de la polyacrylophenone I. Rendements quantiques de coupures dues aux reactions de norrish II

Abstract Quantum yields of scission of oligomers, dimers and trimers of poly- acrylophenone have been determined by irradiating in benzene solution under nitrogen at 365 nm. The scissions occur preferentially towards the non-substituted carbonyl in the α position, in agreement with the substitution rules of Lewis. The carbonyls situated in the middle of the trimers lead to the same quantum yields of scission, which are equivalent to the quantum yields of the carbonyls substituted by CH 3 in the α position. The photochemical epimerization of the diastereoisomers of the dibenzoyl 2,4-pentane compound supports the existence of a biradical intermediate in the Norrish type II reaction. The quantum yields for the formation of the various photoproducts are independent of the configuration of the oligomers.