Gas phase tautomerism of tautomeric azo naphthols and related Schiff bases studied by mass spectrometry

Mass spectra of several azonaphthols and related Schiff bases containing intramolecular hydrogen bonding (IHB) are interpreted in respect of their keto-enol tautomerism. It is shown that in gas phase the enol-like tautomer strongly predominates. In the azodyes the existing IHB is very weak, while in the corresponding Schiff bases it is strong enough and determines the fragmentation pathway.