Infrared study of the reactivity of acetone and hexachloroacetone adsorbed on haematite

Abstract

Infrared spectra of acetone adsorbed at beam temperature on α-Fe₂O₃ show that acetone can chemisorb on Lewis-acid sites and gives, at least partially, enolate anions; these, by aldolic condensation with molecules from the gas phase, produce a chemisorbed form of mesityl oxide. At 523 K acetate ions are formed.

Two different forms of trichloroacetate ions are formed on the surface at beam temperature by the adsorption of hexachloroacetone and trichloroacetic acid.

This behaviour indicates the presence of pairs of acid–base sites on the surface of haematite, and also shows that its surface hydroxy groups have a lower degree of nucleophilic character with respect to those of other oxides such as aluminas, SnO₂ and alkaline-earth oxides.