CHEMISORPTION AND CLEAVAGE OF ALKYL BENZOATES ON ALUMINA SURFACE STUDIED BY INELASTIC ELECTRON-TUNNELING SPECTROSCOPY

The technique of inelastic electron tunneling spectra (IETS) has been used to study the surface reaction of ethyl, isobutyl, and tert-butyl benzoates on alumina. The ethyl and isobutyl benzoates decompose to the corresponding alcohols where the net reaction accounts for the hydrolysis of the benzoate, and the ultimate products of chemisorption on alumina surface are detected to be the corresponding alkoxide anions. In the case of tert-butyl benzoate, the chemisorbed species on the alumina surface is benzoic acid rather than tert-butyl alcohol. In both cases, the surface reactions are identified as the dissociative chemisorption of the hydrolysis products of the original benzoate molecule. These phenomena are explained by the cleavage of the acyl-oxygen bond and of the alkyl-oxygen bond, respectively, both proceeding via acid-catalyzed hydrolysis.