Abstract: The photochemistry of a-allylbutyrophenone (a-AB) and that of y- cyclopropylbutyrophenone (y-CB) both reveal that the 1, 4-biradicals generated by triplet- state y-hydrogen abstraction undergo typical radical rearrangements in competition with their more normal type I1 reactions. From a-AB, 2-phenyl-2-norbornanol is formed in 1/24th the combined yield of 1-phenyl-4-penten-1-one and 1-phenyl-2-allylcyclobutanol. Its ...