Infrared spectroscopic study of the adsorption of nitriles on aluminium oxide. Fermi resonance in coordinated acetonitrile

Abstract

The adsorption of acetonitrile CH₃CN and CD₃CN on to a δ-Al₂O₃ sample has been studied by i.r. spectroscopy. The nitrile is coordinately bonded to exposed Al³⁺ ions or H-bonded to surface hydroxyl groups. Fermi resonance between the ₂ fundamental and the (₃+₄) combination in the two adsorbed species is discussed and the positions of the unperturbed vibrations are estimated. An assignment of the Fermi resonance doublet in the coordinated species is given. The CN stretching vibration seems not to be very sensitive to energetic heterogeneities among the exposed cations. I.r. and Raman spectra of adsorbed t-butyl cyanide are also discussed.