Electron paramagnetic resonance and spin trapping study of radicals formed during reaction of aromatic amines with isoamyl nitrite under aprotic conditions.

Diazotization of primary aromatic amines with isoamyl nitrite in benzene at room temperature was studied employing EPR and spin trapping techniques. Nitrosodurene (ND), 2-methyl-2-nitrosopropane (MNP), and 5,5-dimethyl-pyrroline N-oxide (DMPO) were used as spin trapping agents. Aryl radicals were detected employing ND and MNP. Using DMPO as a spin trap most of the amines produced EPR spectra ascribed to adducts with aniline-type radicals (N-centred radicals). The assignments were verified using 15N-labeled anilines. Similar spectra of DMPO adducts were recorded from amines treated with benzoyl peroxide or benzophenone plus UV. Possible mechanisms of formation of these adducts (radical trapping versus nucleophilic addition to DMPO followed by oxidation) during treatment of the amines with isoamyl nitrite are discussed.