Benzophenone triplet properties in acetonitrile and water. Reduction by lactams

Abstract

The technique of time resolved laser flash spectroscopy has been used to study the photophysical and photochemical properties of the lowest triplet of benzophenone in water and acetonitrile. New estimates have been obtained for the triplet extinction coefficient, unimolecular and bimolecular rate constant of decay in both solvents, as well as a determination of the quantum yield of ketyl formation in pure water and the rate constants of hydrogen abstraction from various lactams in both solvents. Evidence for hydrogen abstraction from water by a triplet of benzophenone is found. Correlation between rate constants of hydrogen abstraction from lactams by the lowest benzophenone triplet and their ionization potential is discussed. Reversibility of these hydrogen abstractions is considered.