Kinetics of oxidation of organic compounds by silver(II) in aqueous perchloric acid solution. Part 2. Aliphatic carboxylic acids

Abstract

The reactions between Ag^II and acetic, propionic, n-butyric, isobutyric, and pivalic acids have been investigated kinetically, at 14.0, 22.0, and 30.0 °C, in aqueous perchloric acid media (1.00 ⩽[HClO₄]⩽ 4.00M; µ= 4.0M) by a stopped-flow technique. The overall reaction is: 2Ag^II+ RCO₂H → 2Ag^I+ 2H⁺+ CO₂+ products. The reactions are second order and the rate constants increase with decreasing acidity. Alternative mechanisms for acid-dependent pathways are considered. The rate-determining step involves electron exchange with R–CO₂H bond rupture. Two pathways were found to operate and their reactivities correlate with the σ* values of the Taft equation. The results are discussed with reference to previous findings concerning Ag^II oxidation of formic acid.