Mass spectral study of the occurrence of tautomeric forms of selected enaminones

Abstract

The mass spectra of enaminones can provide valuable information with regards to tautomeric equilibria in the gas phase. Mass spectra of selected enaminones have been analyzed and specific fragmentation assignments have been done to characterized and weigh co-existing all possible tautomers of enaminones. Thioenaminones are of particular interest due to their tendency to shift the tautomeric equilibrium towards the thioenolimine or thioenolenamine form. Mass spectra of differently substituted enaminones are examined looking for common mass spectral behaviors. Ion fragmentations from specific tautomers allow predicting the most stable structure for the selected compounds. Acceptable correlation between the experimental data and theoretical results are found only with the neutral species, indicating that mass spectrometry could be resourced as a tool for the investigation of tautomerism of neutral species in the gas phase.