ELECTRON-IMPACT MASS-SPECTRA OF SOME SUBSTITUTED C-PHENYL N-TERT-BUTYL NITRONES (PBNS)

The electron impact mass spectra of fifteen 4-substituted PBN's and PB N itself have been obtained using the probe method. Strong molecular i on peaks were observed in most cases. Fragmentation follows two major pathways depending on the polarity of the substitutent: the tert-butyl bond breaks to produce either the tert-butyl cation or isobutylene. T he latter route is analogous to the well known McLafferty rearrangemen t. Fragmentation to produce the tert-butyl radical is a minor route. E lectron-donating polar substituents appear to enhance fragmentation to isobutylene.