An evaluation of polyethylene glycol as a catalyst in liquid-gas phase transfer catalysis: the base-catalyzed isomerization of allylbenzene

The gas-phase base-catalyzed isomerization of allylbenzene has been used as a model reaction to evaluate the activity of polyethylene glycol in liquid-gas phase transfer catalysis by-use of pulse reaction kinetics. Polyethylene glycol-potassium carbonate complexes adsorb the allylbenzene and reaction occurs at the catalyst interface. The activity of the catalyst is determined by two factors: the equilibrium of adsorption of the organic substrate and the solvation of the carbonate anion. We have found that polyethylene glycol adsorbs poorly vis-à-vis high surface area γ-alumina, and that solvation of the carbonate anion by the polyethylene glycol also reduces its activity. Carbonate anions impregnated on γ-alumina are not solvated and therefore have high activity.