A kinetic and mechanistic investigation of oxidation of D-Mannitol by Diperiodatocuprate (III) in an aqueous alkaline medium

The study investigates the kinetics associated with the oxidation of D-Mannitol (D-Mann) by diperiodatocuprate(III) (DPC) in an aqueous alkaline medium using spectrophotometric method. Reaction medium’s ionic strength was maintained constant at 0.60 mol dm^-3. First-order kinetics in [DPC] and less than unit order for [D-Mann] and [alkali] were observed in the reaction. It was of the negative fractional order in [periodate]. It was determined that the reaction of substrate D-Mann with DPC in an alkaline medium shows 1(D-Mann):4(DPC) stoichiometry. Ionic strength of the medium had no effect on the rate of reaction and same was the observation with dielectric constant. The products of reaction were identified by FTIR and confirmed by LC-ESI-MS spectral data. The reaction constants for each step of the mechanism were determined. For the slow step of reaction mechanism, activation parameters were calculated and discussed. Further, thermodynamic quantities for the reactions were also estimated.

Based on the literature survey, DPC was chosen for the current study. DPC was prepared by the reported methods as cited in the manuscript. Stable reaction mixtures were prepared in two different reagent bottles and maintained at a desired temperature using a water bath. The reaction between the oxidant DPC and substrate D-Mannitol was spectrophotometrically analyzed by a UV-Vis spectrophotometer. With the help of data obtained, graphs were plotted to obtain k_obs for different variations, and the mechanism was synthesized. A rate law for the reaction under investigation was proposed based on the results and mechanism.