Radiation mechanisms. Part VII. Electron-loss and -capture processes in phenylphosphinic acid and related compounds

Abstract

Exposure of phenylphosphinic acid and related compounds to ⁶⁰Co γ-rays at 77 K resulted in electron addition to the aromatic ring, since, the characteristic e.s.r. spectra of the alternative phosphoranyl radicals were absent except for that assigned to PhṖH(O)OH radicals. The anions were protonated on annealing, or directly at 77 K in methanolic glasses, to give cyclohexadienyl radicals which exhibited a hyperfine coupling of 22 G to ³¹P nuclei. However, the aromatic anion of PhPH(O)OH probably undergoes a 1,2-hydrogen atom shift from phosphorus to the ring carbon, the resulting adduct having A(¹H) 40 and A(³¹P) 200 G. This species is unstable and either breaks down to give benzene and ·PO(OH)^– radicals, or undergoes a further hydrogen shift to give a normal cyclohexadienyl species.