Kinetics of a Phase-Transfer Catalysis Reaction in Supercritical Fluid Carbon Dioxide

The first example of a phase-transfer-catalyzed reaction carried out in a supercritical fluid (SCF) is reported. The kinetics of the nucleophilic displacement of benzyl chloride with a bromide ion in SCF solvent CO 2 in the presence of acetone cosolvent is presented. In addition, the solubility of tetraheptylammonium bromide (THAB) in SCF CO 2 in the presence of acetone cosolvent is reported. The reaction rate was measured at 50 and 75 °C at pressures to 200 bar; the reaction was found to follow first-order, reversible kinetics for the reactions catalyzed by THAB and zero-order kinetics for reactions catalyzed by 18-crown-6.