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

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.