3-hydroxy-4-methyl-4-pentenonitrile and 4-methyl-3-oxo-4-pentenonitrile: Study of the Tautomerics Equilibria in Gas Phase and in Solution.

JUAN M. GIUSSI; AGUSTÍN PONZINIBBIO; M. SUSANA CORTIZO; PATRICIA E. ALLEGRETTI

SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY.

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2010 vol. 77 p. 367 - 373

1386-1425

In the present work the tautomerics equilibria in 3-hydroxy-4-metil-4-pentenonitrile and 4-methyl-3-oxo-4-pentenonitrile have been studied. The first compound presents two possible theoretical tautomers, nitrile and ketenimine. The second compound presents four possible theoretical tautomers keto-nitrile, nitrile-enol (E and Z) and keto-ketenimine. The study of the equilibrium in gas phase was performed by gas cromatography-mass spectrometry (GC-MS), and in solution by proton nuclear magnetic resonance spectrometry (1H-NMR). In gas phase, the keto-nitrile tautomer was favoured, a result which was supported by theoretical calculations by use of AM1 semiempiric calculation. The experimental tautomerization heat values were in good agreement with the theoretical ones. The 1H-NMR spectra gave the additional evidence for the coexistence of the tautomers ketonitrile and enolnitrile for 4-methyl-3-oxo-4-pentenonitrile. The nitrile-ketenimine equilibrium for both compounds could not be observed by 1H-NMR spectra because of the low sensibility of this method. The ketonitrile-enolnitrile tautomerization heat of 4-methyl-3-oxo-4-pentenonitrile have been calculated and compared with the corresponding one in gas phase for evaluate the solvent effect.