A comparison of electron spin resonance α- and β-hyperfine coupling constants in para-substituted α-phenethyl radicals

The linear relationship between the electron spin resonance hyperfine coupling constants (hfc) of the α- and β-hydrogens of para-substituted α-phenethyl radicals provides experimental evidence that the magnitude of both the α- and β -hfc is determined largely by the extent of spin delocalization in these benzylic systems. The scale, developed using substituted benzyl radicals, is shown to apply to phenethyl radicals as well.