Tautomeric equilibrium of amides and related compounds: theoretical and spectral evidences

The tautomeric equilibrium of several amides and related compounds is studied experimentally via mass spectrometry techniques. Experimental findings are complemented with theoretical calculations in order to rationalise mass spectra results of some amides, thioamides, ureas and thioureas. Some further possible studies are pointed out in order to complement present findings. Both mass spectra and theoretical results indicate that tautomerism involves neutral species rather than the ionic analogues. Besides, thio-derivatives have a relatively higher tendency to occur as imidols. (C) 2000 Elsevier Science B.V. All rights reserved.