Aromatic nucleophilic fluorination with KF catalyzed by polymer-supported phosphonium salts under solid–solid–liquid phase transfer conditions

Abstract

Fluorination of 2,4-dinitrochlorobenzene (DNCB) with solid KF was conducted in the presence of polymer-supported tetraphenylphosphonium chloride catalyst under solid–solid–liquid (S–S–L) phase transfer conditions. The triphase fluorination obeyed zero-order kinetics with respect to DNCB concentration and first-order kinetics with respect to the catalyst concentration. The apparent activation energy for the fluorination was estimated as about 40 kJ/mol. On the basis of these results, the ion exchange reaction between the Cl − ion of the supported catalyst and the F − ion of KF was concluded to be rate-determining in this S–S–L triphase fluorination. The addition effect of water on the triphase fluorination was discussed by means of both the prompted dissolution of solid KF and the decreased reactivity of the F − ion, induced by increased hydration.