Laser flash photolysis of 1 in solution leads to the formation of a short-lived triplet (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 I1 ...