Study of intramolecular hydrogen abstraction on photoexcited 1,3-dimethylanthrone in the condensed phase

The time-resolved thermal lensing (TRTL) technique was applied to determine the reaction heat of intramolecular hydrogen abstraction for excited 1,3-dimethylanthrone (DMAT). The excited carbonyl group abstracts the hydrogen atom of the neighboring methyl group to produce an intermediate. The intermediate decayed with 1.2±0.1 μs. The heat conversion efficiency was determined to be 1.02±0.02, revealing that excited DMAT emits all the energy as heat. The time profile of a TRTL signal led to the value of the reaction heat for the intermediate, 131±6 kJ/mol. We briefly discuss candidates for the intermediate.