Competition between cyclization, cleavage, and reverse hydrogen transfer in 1,4-hydroxybiradicals: crystal structure--solid state reactivity correlations

[reaction: see text] To provide experimental evidence on the relationship between stucture and reactivity in 1,4-hydroxybiradical intermediates, the Norrish type II photochemistry of a homologous series of spirobenzoyladamantane derivatives was investigated in the crystalline state and the outcome correlated with the structures of the compounds as determined by X-ray crystallography. The results provide an unusually detailed and compelling picture of the geometric factors responsible for the partitioning of these reactive intermediates among cleavage, cyclization, and reverse hydrogen transfer.