Synthesis and spin trapping applications of 2,2-dimethyl-d6-4-methyl-2H-imidazole-1-oxide-1-15N

A new spin trap, 2,2-dimethyl-d6-4-methyl-2H-imidazole-1-oxide-1-15N (lTMIO), was synthesized and characterized. Hyperfine splitting (HFS) constants of spin adduct ESR spectra of this compound with oxygen-centered, carbon-centered, thiyl and sulfite-derived radicals were determined and compared with the data of the unsubstituted compound. The increase in ESR spectral intensity and the accompanying decrease of the spectral linewidth result in resolution of the HFS due to interaction with alpha-protons of alkyl radicals trapped by lTMIO. Trapping of the formate radical in deoxygenated aqueous solution revealed a very low spectral linewidth (delta Bpp = 0.028 mT) of the corresponding adduct. A strong dependence of the ESR spectra on pH was observed when the autoxidation product of sulfite, SO3-, was trapped. The pKa was found to be 5.8 +/- 0.3. In comparison to other nitrones, application of this spin trap provides more detailed information on the structure of the species trapped, especially for carbon-centered radicals.