Photochemical Reduction of p-Quinones with Hydrogen Donors Studied by CIDNP Technique

Photo-reduction of p-benzoquinone, 1,4-naphthoquinone, and their methyl- or chloro-derivatives has been investigated by means of CIDNP technique. Strongly polarized PMR signals due to unstable reaction intermediates, p-quinones, and hydroquinones were observed during the course of reaction. Structures of the unstable reaction intermediates, none of which accumulated as reaction products, were determined, their polarized PMR signals being compared with those of the unstable reaction intermediates resulting from the deuterated substrates. From these results, a reaction scheme for these photo-reduction was proposed.