Aquachloroiridium (III)-catalyzed oxidation of some unsaturated acids in acetone by acidic quinolinium fluorochromate

Kinetic investigation in Ir(III)-catalyzed oxidation of fumaric acid (FA) and crotonic acid (CA) in an acidified solution of quinolinium fluorochromate (QFC) has been studied in the temperature range of 30–45 °C. First-order kinetics was observed in the case of catalyst Ir(III) as well as oxidant QFC. The order of reaction with respect to substrate (unsaturated acids) was found to be zero. Increase in [Cl−] showed fractional negative order. The influence of [H+] and ionic strength on the rate was found to be insignificant. The main product of oxidation of fumaric acid (FA) and crotonic acid (CA) were identified as pyruvic acid and acetone, respectively. The reaction has been studied in ten different solvents. The first-order rate constant had no effect with decrease in the dielectric constant of the medium. The values of rate constants observed at four different temperatures (30, 35, 40 and 45 °C) were utilized to calculate the activation parameters. A suitable mechanism in conformity with the kinetic observations has been proposed and the rate law has been derived on the basis of obtained data. A transient complex formed between IrIII and oxidant in a slow and rate-determining step, further reacts with substrate to give the products in a series of fast steps.