Radical addition to aromatic aldoximes

Abstract

The e.s.r. spectra of the hydronitroxide radicals ArCHX-NHȮ, obtained by reaction of a number of aromatic aldoximes ArCHNOH (Ar = phenyl, 3- and 4-pyridyl, 2- and 3-thienyl, 2-furyl) with radicals X˙(X = MeS, BuⁿS, Et₃Si, Ph₃Ge), have been detected. Assignment of the α- and β-proton splittings has been achieved by means of deuterium labelling. The analysis of the hyperfine splittings supports the hypothesis that the radicals ArCH(SR)-NHȮ adopt a single preferred conformation whereas the radicals ArCH(SiEt₃)-NHȮ and ArCH(GePh₃)-NHȮ undergo a rotational pathway through a variety of torsional conformers.