In situ FTIR study of the adsorption and reaction of 2′-hydroxyacetophenone and benzaldehyde on MgO

The adsorption and reaction of 2′-hydroxyacetophenone and benzaldehyde on MgO were investigated via in situ FTIR spectroscopy in an attempt to gain a better understanding of the Claisen–Schmidt condensation reaction between these two molecules catalyzed by MgO. The results indicate that 2′-hydroxyacetophenone adsorbs on MgO through abstraction of the phenolic hydrogen, forming a surface phenolate ion. Benzaldehyde adsorbs through its carbonyl bond and can be subsequently oxidized to form two different types of benzoate species. These benzoate species are inactive toward further reaction with 2′-hydroxyacetophenone and/or its surface derivatives and accumulate on the MgO surface with time on stream. In contrast, the 2′-hydroxyacetophenone-derived phenolate ion reacts with benzaldehyde, yielding an adsorbed chalcone-type product.