AB-INITIO STUDY OF THE ADSORPTION OF ACETONE AND KETO-ENOL EQUILIBRIUM ON THE MGO(100) SURFACE

An ab-initio quantum mechanical study of the adsorption of acetone and 2-propenol on a clean MgO(100) surface is reported. Ab-initio Hartree -Fock calculations have been carried out using an embedded-cluster app roach in which the environment is described by total ion potentials an d point charges. Optimized geometries for both acetone and 2-propenol adsorbed on the surface have been obtained using two basis sets and se veral model clusters. The adsorbate-surface interaction is found to be weak and electrostatic in nature, although there is a relative stabil ization of the enol tautomer. The effect of the surface on the keto-en ol equilibrium is analyzed and explained on the basis of this differen tial adsorption. Surface reconstruction induced by the adsorbate is al so considered. While the surface relaxation effects are found to be ne gligible for acetone, they appear to be larger for 2-propenol. and all owing the surface to relax changes the qualitative description of the enolization process since in this case an enolate species is found to be adsorbed on the surface. (C) 1998 Elsevier Science B.V.