Photochemistry of macrocyclicketones within zeolites: competition between Norrish typeI and typeII reactivity

Photolysis of macrocyclic mono- and diketones (1 and 2) included in X and Y zeolites gives Norrish type I products in addition to the products obtained via the Norrish type II process, the only observed process in isotropic media. Enhancement of the type I over the type II process is cation-dependent and especially large enhancements are obtained with Li and Na as cations. The zeolite effect is attributed to a reduction in the rate of the Norrish type II a-hydrogen abstraction process