Hydrogen-Atom Abstraction from the Solvent by the Lowest Excited Triplet State of Chromone Yielding the [beta]-Keto-Type Solvent Adduct(s)

The lowest excited triplet state of chromone with mixed nπ*-ππ* character abstracts a hydrogen atom from the solvent. Although the ketyl-type radical thus generated is indistinguishable from the β-enol-type radical, this radical (or its keto form, i.e., the β-keto-type radical) gives rise to formation of the β-keto-type solvent adduct(s).