Abstract
Four fluorinated pyridinium-N-imines have been studied under both electron ionisation and fast atom bombardment conditions, with the aim of evaluating the role of fluorine in the stabilisation of the possible canonical forms of the resonan ce 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 impact data, in particular the highly favoured formation of [M – H]+ ions and the presence of specific fragmentation channels, different from the ones described in the literature for non-fluorinated analogues, are in agreement with this hypothesis. Fast atom bombardment data indicate that protonation activates severe structural modifications, responsible for decomposition processes that are not easily explained.
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