Photochemical Reaction of 9,10-Phenanthrenequinone with Hydrogen Donors. Behavior of Radicals in Solution as Studied by CIDNP

Behavior of radicals produced in the photochemical reaction of 9,10-phenanthrenequinone was investigated by use of CIDNP and ESR technique. By comparison of the sign of CIDNP signals in formation of and in decomposition (photochemical or thermal) of adducts, the rearrangement of adducts, e.g., from the 1,2-adduct to 1,4-adduct and vice versa, was proposed. Although the adducts are stable enough to isolate in general, they decomposed photochemically or thermally to give the mixture of 9,10-phenanthrenediol (or its quinhydrone), the dehydrogenated dimer of hydrogen donor, and others as minor product.