Inelastic electron tunnelling spectroscopy (IETS) of carboxylic acids and related systems chemisorbed on plasma-grown aluminium oxide. Part 1.—Formic acid (HCOOH and DCOOD), acetic acid (CH3COOH, CH3COOD and CD3COOD), trifluoroacetic acid, acetic anhydride, acetaldehyde and acetylchloride

Abstract

A study of the inelastic electron tunnelling spectra (IETS) of formic acid, [²H₂]formic acid, acetic acid, [²H₄]acetic acid and trifluoroacetic acid shows that these chemisorb from the vapour phase on to plasma-grown aluminium oxide as surface-bound formates and acetates. Detailed vibrational mode band assignments are made and the carboxylates are deduced to be adsorbed symmetrically on, though not necessarily perpendicular to, the oxide surface. The plasma-grown oxide shows enhanced reactivity to acetaldehyde over bulk γ-alumina behaviour. Evidence is obtained for the involvement of two surface-site types in reaction with trifluoroacetic acid.