MASS-SPECTROMETRY OF SOME FLUORINATED PYRIDINIUM N-IMINES

Four fluorinated pyridinium-N-imines have been studied under both elec tron ionisation and fast atom bombardment conditions, with the aim of evaluating the role of fluorine in the stabilisation of the possible c anonical forms of the resonance hybrid, The data obtained suggest that the presence of a fluorinated substituent increases the contribution of the form bearing the negative charge on the oxygen atom, Electron i mpact data, in particular the highly favoured formation of [M-H](+) io ns and the presence of specific fragmentation channels, different from the ones described in the literature for non-fluorinated analogues, a re in agreement with this hypothesis, Fast atom bombardment data indic ate that protonation activates severe structural modifications, respon sible for decomposition processes that are not easily explained.