TRANSFORMATION OF 1,2-DIOLS OVER PERFLUORINATED RESINSULFONIC ACIDS (NAFION-H)

The transformations of 1,2-diols over perfluorinated resinsulfonic acids (Nafion-H) were studied, and correlations were examined between the structures of the investigated diols, the possible dehydration routes and the catalytic properties of Nafion-H. Comparisons were also made between the catalytic properties of Nafion-H and NaHX zeolite. Because of its stronger acidity, Nafion-H functions at temperatures considerably lower than those for the usual dehydrating catalysts, e.g. the zeolites. As is well established for other solid electrophilic catalysts, the dehydration of 1,2-diols mainly proceeds via the pinacol rearrangement. The lower temperatures and the stronger acidity of Nafion-H strongly favour the pinacol rearrangement versus 1,2-elimination The reaction conditions are also advantageous for the formation of substituted 1,3-dioxolanes in a secondary condensation step between the unreacted diol and the primarily formed carbonyl compounds. Nafion-H gradually deactivates during long use, but it can be partially reactivated by washing with acetone.