ELECTRON-SPIN RESONANCE-SPECTRA OF DIASTEREOMERIC NITROXYLS PRODUCED BY SPIN TRAPPING HYDROXYALKYL RADICALS

Nitroxyl radicals having two chiral centers can be produced by the spin trapping method. In alcoholic solvents asymmetric spectra are obtained from the superposition of two spectra due to diastereomeric nitroxyls. In an aprotic solvent such as toluene the difference in the spectra of the diastereomers is large enough to permit separation of the doublets due to the β-hydrogen hyperfine splitting. Although this parameter shows a large solvent effect the apparent solvent effect on the g value and the nitrogen hyperfine splitting is small. Various experimental facts point to intramolecular hydrogen bonding as the cause for the difference in the spectra obtained in protic and aprotic solvents. An assignment of structure (cis-trans) is made on the basis of some correlations of ESR parameters. © 1979 American Chemical Society.