Reduction of 4,4'-stilbenequinone and 4,4'-diphenoquinone upon reaction with photogenerated radicals.
The properties of 3,3',5,5'-tetra-tert-butyl-4,4'-stilbenequinone (StQ) were studied by photochemical means. Acetone, acetophenone or benzophenone was photolyzed in the presence of both StQ and a donor, such as alcohols or triethylamine. This initiated reaction of a ketyl radical with StQ to form a semiquinone radical and eventually induce a permanent bleaching due to conversion of StQ to 4,4'-dihydroxystilbene (StQH(2)). The quantum yield of conversion of StQ to StQH(2) increases with the donor concentration. Similar effects were found for the ketone-sensitized radical-induced conversions of the analogous diphenoquinone to the reduction product, diphenol.
Görner
Helmut
H
Max-Planck-Institut für Bioanorganische Chemie, Mülheim an der Ruhr, Germany. goerner@mpi-muelheim.mpg.de