The magnitude of the hydrogen-deuterium isotope effect (IE) in the photosensitized cyanation of biphenyl is found to depend on the concentration of biphenyl and on that of cyanide, as well as on the ionic strength of the medium. These concentration dependences are shown to originate from intermolecular electron exchange between biphenyl and its radical cation, in competition with addition of cyanide. Similar observations are made for ...
