Isotopic exchange reactions in liquid sulfur dioxide—VII Catalysis by antimony pentafluoride of sulfur exchange between thionyl fluoride and sulfur dioxide

Radiosulfur exchange has been studied in liquid mixtures of thionyl fluoride and sulfur dioxide. While no exchange occurs between the two species alone, the addition of antimony pentafluoride leads to exchange, both observations being parallel to those observed with the analogous chlorine compounds. The kinetics of the exchange has been interpreted in terms of equilibria involving 1:1 adducts between catalyst and each solvent species as well as a polymeric antimony pentafluoride species. The rate-determining step consists of bimolecular interaction between either 1:1 adduct and the other solvent species. For the reaction between SO2. SbF5 and SOF2 the rate constant is k = 1·85 × 107 exp(−17,300/RT)1. mole−1 sec−1, ΔS≠ = −27·3 ± 3·9 e.u.