AN ENDOR STUDY OF RADICAL SPIN ADDUCTS DERIVED FROM NOVEL 2-SUBSTITUTED-5,5-DIMETHYL-PYRROLINE-N-OXIDE SPIN TRAPS

ENDOR spectra of a series of carbon- and oxygen-centered radical adduc ts of 2-substituted DMPO-type nitrones are reported. They include the novel cyclic nitrones, 2-phenyl-5,5-dimethyl-pyrroline-N-oxide (2-Ph-5 ,5-M2PO), 2,5,5-trimethyl-1-pyrroline-N-oxide (2,5,5-M3PO), and 2-phen yl-3,3,5,5-tetramethyl-1-pyrroline-N-oxide (2-Ph-3,3,5,5-M4PO). Electr on paramagnetic resonance (EPR) was used to ascertain the nitrogen hyp erfine splittings (hfs's) while H-1 ENDOR was employed to determine th e long-range (gamma) hydrogen hfs's. The magnitude of the nitrogen hfs combined with the numbers and sizes of the long-range gamma-H hfs's o f spin adducts of these new spin traps are shown to help disclose the identities of various added radicals (or radical addends). It should b e noted that the three new spin traps presented here are keto-nitrones not aldo-nitrones. Thus, there is alkyl (e.g. CH3) or aryl (e.g. C6H5 ) substitution at the 2-position of the pyrroline-N-oxide ring. This f eature is part of our search for modified spin traps that yield spin a dducts with greater stability.