Heterogeneous Photoinduced Homolytic Aromatic Substitution of Electron-Rich Arenes with Perfluoroalkyl Groups in Water and Aqueous Media - A Radical-Ion Reaction

The photoinduced electron transfer (PET) substitution reaction of electron-rich aromatic nuclei with perfluoroalkyl R-f groups was carried out in water or aqueous mixtures to render substitution products resulting from replacement of aromatic H atoms with the Rf moiety in good yields (5788%). Some mechanistic aspects are discussed, supporting the notion of a PET reaction leading to a classical radical homolytic aromatic substitution (HAS) followed by an electron transfer (ET) and then a proton transfer (PT) sequence. A radical mechanism superimposed on a redox process is proposed to account for product formation. Evidence for the radical cation species (as an initiation event) generated from electron-rich arenes in the presence of perfluoroalkyl halides is provided by the UV/Vis transient spectra obtained by Nanosecond Laser Flash Photolysis techniques.