The photochemistry of a series of 10 a-(ary1oxy) acetophenones has been examined by quantum yield, product studies, and laser flash photolysis techniques. Triplet decay involves a competition of@-cleavage with intramolecular quenching by the@-aryl group, the latter being favored in all systems. Typical triplet lifetimes at room temperature range from 60 to 260 ps and are rather insensitive to the substitution pattern.@-Cleavage rate constants ...