Kinetics and Spectroscopic Study of a Ketyl-Phenoxy Biradical Produced by Remote Hydrogen Abstraction

Article abstract of DOI:10.1021/jo00229a021

Laser flash photolysis of 1 in solution leads to the formation of a short-lived triplet (τ_T = 13.3 ns in acetonitrile) which decays via hydrogen abstraction from the remote hydroxy group.The resulting 1,13-biradical has a lifetime of 118 ns in acetonitrile and decays almost exclusively by back-hydrogen-transfer in a process that appears to be controlled by intersystem crossing.The valeryl analogue 2 is nonreactive with respect to Norrish II fragmentation in fluid solution (Φ_II < 0.001), presumably as a result of a shortened triplet lifetime due to efficient intramolecular phenolic quenching.