LIQUID-SOLID-LIQUID TRIPHASE CATALYSIS - CONSIDERATION OF THE RATE-LIMITING STEP, ROLE OF STIRRING, AND CATALYST EFFICIENCY FOR SIMPLE NUCLEOPHILIC DISPLACEMENT

The kinetics of the triphase catalyzed displacement of chloride ion on n-decyl methanesulfonate employing a series of 1% cross-linked polystyrene resins having pendant tri-M-butylphosphonium groups has been investigated. The rate of displacement (1) exhibited a pseudo-first-order dependency on the mesylate concentration, (2) was directly proportional to the amount of catalyst used, (3) was independent of stirring, (4) was characterized by a free energy of activation of ~30 kcal mol-1, and (5) depended on the catalyst-ion concentration in the resin. In addition, reaction was favored at the external portion of the bead. Taken together, these observations provide strong support that a diffusion-limited chemical reaction is the rate-controlling step. When large quantities of polymer were employed, stirring was needed to increase resin contact with the liquid-liquid interface. Consideration of apparent activation energies, and absorption of n-decyl methanesulfonate in the catalysts, supports the conclusion that inefficient use of ionic sites dispersed throughout the resins is responsible for the low activity observed. © 1979, American Chemical Society. All rights reserved.