| Abstract
| - Three new photoproducts, ethyl O-benzoyl mandelate(5a), ethyl O-acetylmandelate (6a),andbiphenyl triketone (7a) are isolated and identified in thereactions of ethyl phenylglyoxylate (1a)in benzene. Quantum yields and initial rate constants of productformation are shown to beconcentration dependent. For the formation of carbonyl product3 at lower starting materialconcentrations (<0.01 M), quantum yields greater than 1 are observed.Variations in the quantumyields as a function of reaction time are due to the accumulation ofα-hydroxyphenyl ketene (D).The relative reactivities of triplet excited states ofphenylglyoxylates 1 and phenyl ketones arecompared. A mechanism involving both intramolecular γ-Habstraction and intermolecular Habstraction, which leads to radical chain reaction, is proposed.Rate constants for intramolecularγ-H abstraction (kN) and intermolecular Habstraction (kI) of methyl phenylglyoxylate(1d) aremeasured.
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