Kinetics in phase-transfer catalysis: a theoretical study. Part 1. Poisoning effect by catalyst foreign ion

Abstract

The kinetics of phase-transfer-catalysed reversible or irreversible S_N2 substitution of an organic substrate RY by an aqueous electrolyte X^– has been studied theoretically, in order to analyse the poisoning effect due to a foreign counter ion Z^– of the phase-transfer catalyst. The foreign ion, although introduced in catalytic amount, deactivates a portion of the phase-transfer catalyst. This results in a slower reaction, although it may go to completion or to equilibrium conversion. However, the poisoning effect is negligibly small when the selectivity extraction constant K_z/x^sel⩽ 1 at equal initial reactant concentrations and when K_z/x^sel⩽ 10 at a ten-fold electrolyte concentration. Under these conditions, the reaction rates depend linearly on the overall' onium salt concentration in the organic phase.