Kinetics and mechanism of the silver(I)-catalyzed oxidations of arsenic(III) and antimony(III) with peroxodiphosphate in acetate buffers

Abstract

A kinetic study of the silver(I)-catalyzed oxidations of AsIII and SbIII with peroxodiphosphate (pdp) was performed by estimating AsIII and SbIII with permanganate. The oxidation of AsIII was found to conform to the rate law (i) in the range pH 2.10—4.52, where K2 and K3 are the acid-dissociation –d[AsIII]/dt=[pdp][AsIII][AgI](k1K2–1[H+]2+k2[H+])/([H+]+K3)(i), constants of H3P2O8– and H2P2O82–; k1/K2 and K2 were found to be (5.0 ± 0.2)× 104 dm9 mol–3 s–1 and 38 ± 3 dm6 mol–2 s–1 at 50 °C. The oxidation of SbIII was first order in [SbIII], [pdp], and [AgI], and independent of pH, [acetate], and [tartrate]; the third-order rate was found to be 18 ± 1 dm6 mol–2 s–1 at 50 °C in the range pH 3.00—4.61. The silver(I) catalysis operates through complex formation of pdp and AgI rather than AgI/AgIII redox cycling.