Primary photochemical processes in aromatic molecules. Part 10. - Photochemistry of substituted benzophenones

Abstract

The reasons for the low photochemical reactivity of certain derivatives of benzophenone have been investigated. Quantum yields, absorption spectra, luminescence characteristics, flash photolysis and spectroscopic studies of primary products and molecular weight determinations of the state of aggregation are reported. The photochemical stability of ortho alkyl benzophenones is attributed exclusively to tautomerization and the stability of para hydroxyl benzophenone to inversion of π-π* and n-π* triplet states. In the 2,4-dihydroxyl derivative the triplet state is no longer observed, probably because π-π* and n-π* levels are inverted in both singlet and triplet manifolds.