Benzene propylation catalyzed by sulfonic acid resin

Abstract

Rideal kinetics have been observed for benzene propylation catalyzed by beads of sulfonic acid ion-exchange resin at 55 °C and 1 atm. High catalytic activity (1.5 × 10 −8 moles/equiv of acid groups sec) was found for macroporous but not for gel-form resins, demonstrating the practical advantage of high internal surface areas when reactants are almost incapable of swelling the polymer network. Reaction was inhibited by n-heptane, which weakly swelled the network, and this result implies that reaction took place not on the surface, but just within the underlying matrix. From the kinetics, the rate determining step has been identified as the combination of a s-propyl carbonium ion with a benzene molecule. The observed seventh-order dependence of rate on catalyst -SO 3H group concentration suggests that the carbonium ion was stabilized by a surrounding solvent-like network of hydrogen-bonded acid groups sharing the proton deficiency.