SYNTHESIS OF 1,3-DIOXOLANES CATALYZED BY ALPO4 AND ALPO4-AL2O3 KINETIC AND MECHANISTIC STUDIES

A number of aldehydes and ketones were easily and quantitatively converted to the corresponding 1,3-dioxolanes by the reaction with ethylene glycol over four synthetic amorphous AlPO4, and AlPO4-Al2O3 catalysts using acetonitrile as the solvent at different temperatures in the range 30-60 degrees C without the formation of any by-product. The influence of the number of acid sites on the catalyst surface as well as the substituent effects of different carbonyl compounds studied can be evaluated through several isokinetic parameters obtained owing to the existence of a linear free-energy relationship (LFER). The results obtained account for an intermediate in the transition state whose relative stability is determined by the resonance between the carbonyl group and their substituents, but its evolution is via a concerted process in two adsorption-desorption steps.