An ESR Study of the Aziridine and Azetidine Radical Cations: Evidence for the C...C Ring-Opened Aziridine Radical Cation

Article abstract of DOI:10.1021/j100402a005

The radical cations from aziridine and azetidine have been characterized by ESR spectriscopy following their generation in the solid state by γ irradiation of dilute solutions of the parent compounds in the CFCl3 maarix at 77 K.The ESR parameters of the azetidine radical cation are typical of those for nitrogen-centered amine radical cations such as Me2NH^.+.On the other hand, the radical cation formed from aziridine has very different ESR parameters that compare closely to those for the isoelectronic C^...C ring-opened form of the oxirane radical cation and the allyl radical.The radical cation formed from azetidine is therefore assigned a ring-closed structure with the unpaired electron in a 2p_z orbital on nitrogen perpendicular to the ring plane, whereas the cation from aziridine is an allylic C^...C ring-opened planar isomer with the unpaired electron in a nonbonding ? orbital centered mainly on the two end carbon atoms.The neutral 1-aziridinyl and 1-azetidinyl radicals have been detected as radical products following the γ-irradiation of the parent compounds in the CFCl2CF2Cl and CF3CCl3 matrices.In particular, the 1-azetidinyl radical is produced cleanly from the azetidine radical cation in the CFCl2CF2Cl matrix at ca. 100 K.