| The photochemistry of aromatic compounds containing the ketone chromophore has been studied in the presence of phenols. The research may be divided into two main branches. The first involves a study of bimolecular reactions between photoexcited aromatic ketones and phenols conducted by nanosecond laser flash photolysis techniques. From these experiments, a new mechanism of hydrogen atom abstraction has been proposed. The second branch involves efforts to examine the reaction in compounds where both aromatic ketone and phenol moieties are present in the same chemical structure.;The main result is the emergence of a new mechanism of hydrogen atom abstraction involving initial hydrogen-bonding between the reaction partners, followed by hydrogen transfer as a coupled electron-/proton-transfer. This mechanism rationalised many aspects of phenolic quenching. In the case of bimolecular reactivity, very fast overall quenching rates are observed for both lowest n, pi* and pi,pi* triplets, and a large variety of aromatic ketones of varying structure have been examined. The intramolecular reactivity was based upon the triplet lifetimes of various linked phenolic ketones. The triplet lifetimes are found to vary depending on isomerism and, to a lesser extent, chromophore. Studies of the acetophenone, indanone and benzophenone chromophores have been undertaken. |
