Normal coordinate analysis of molecules adsorbed on zeolite surfaces: Part II. Propene adsorbed in zeolites A

Abstract

Vibrational analysis has been performed for propene in the gas phase and in zeolites A adsorbed near Li +, Na +, Mg 2+, Ca 2+ amd Zn 2+ ions, using a valence force model. Withdrawal of electron density from the π bond to the unoccupied s orbitals of the cations represents the main contribution to the interaction, giving rise to a monotonous decrease of the CC force constant in the sequence of growing polarizing power of the cations. From this, an approach of the cations by the double bond must be assumed in accord with the weakening of the adjacent CH bonds. From further analysis there are indications for the hindrance of the deformation motion due to adsorption, while the methyl group remains rather unperturbed. Normal coordinate analysis of adsorbed species supports well the predictions of the geometrical arrangement and electronic structure from quantum chemical calculations