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 conve rted 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 ra nge 30-60 degrees C without the formation of any by-product. The influ ence of the number of acid sites on the catalyst surface as well as th e substituent effects of different carbonyl compounds studied can be e valuated through several isokinetic parameters obtained owing to the e xistence of a linear free-energy relationship (LFER). The results obta ined account for an intermediate in the transition state whose relativ e stability is determined by the resonance between the carbonyl group and their substituents, but its evolution is via a concerted process i n two adsorption-desorption steps.