OH radical trapping with benzoxazine nitrones: a combined computational and spectroscopic study

The hydroxyl radical addition onto 3-aryl-2H-benzo[1,4]oxazin-4-oxides spin traps yielded very persistent nitroxides. Their EPR spectra showed unusually large splitting due to the trapped OH proton, whose assignment has been possible by means of the isotope exchange technique. A proper DFT study revealed isomeric molecular geometries with possible intramolecular hydrogen bonds (IHB) forming five- and/or six-membered rings, allowing to be envisioned relationships between EPR hyperfine coupling constants (h.f.c.c.) and IHB strengths.