OH] as a homogenous catalyst in perchloric acid medium has been investigated. The kinetic results indicate that the reaction was first order on [NBP] and zero order on [D-Glu]. The reaction followed first-order kinetics with respect to Ru(III) chloride in its lower concentration range and tends to zero-order at its higher concentration. Negative effect of [H + ] and [Cl− ] ions on the rate of oxidation were observed, whereas change of ionic strength (µ) of the medium had no effect on the oxidation velocity. The values of rate constants observed at five different temperatures (298, 303, 308, 313, 318 K) were utilized to calculate the activation parameters. Formic acid and arabinonic acid have been identified as the main oxidation products of the reaction. A plausible mechanism from the results of kinetic studies, reaction stoichiometry, and product analysis has been proposed.

The kinetics of Iridium (III) catalyzed oxidation of D-glucose [D-glu] has been studied by N-bromophthalimide [NBP] in the acidic medium (pH 1.3) at 303 K. The reaction followed first-order kinetics with respect to [NBP] from 0.5 9 10 -4 to 4.0 9 10 -4 mol dm -3 . The results indicate the first-order kinetics in [iridium(III)] chloride at lower concentrations from 0.75 9 10 -6 to 5.8 9 10 -6 mol dm -3 tends towards a zero order at its higher concentrations (up to 13.36 9 10 -6 mol dm -3 ). Zero-order kinetics with respect to [D-glu] from 2.0 9 10 -3 to 20.0 9 10 -3 mol dm -3 was observed throughout its variation. A positive effect on the oxidation rate was observed for [Cl -] from 0.2 9 10 -5 to 2.4 9 10 -5 mol dm -3 and the rate of reaction decreased with increase in dielectric constant (decreasing acetic acid from 35 to 15%) of the medium. A negative effect was observed on the reaction rate for [H ? ] from 1.5 9 10 -2 to 12.0 9 10 -2 mol dm -3 . Addition of reduced product of oxidant, i.e., phthalimide from 1.0 9 10 -4 to 8.0 9 10 -4 mol dm -3 did not show a significant effect on the oxidation velocity. Rate of reaction increased with increase in ionic strength from 0.2 9 10 -1 to 4.0 9 10 -1 mol dm -3 of the medium, i.e., increase in [KNO 3 ]; the rate of reaction was increased. From the linear Arrhenius plot of log k 1 versus 1/T, the activation energy (Ea = 50.91 kJ mol -1 ) was calculated. With the help of the energy of activation, parameters such as enthalpy of activation (DH # = 48.39 kJ mol -1 ), entropy of activation (DS # = -321.63 JK mol -1 ), Gibbs free energy of activation (DG # = 145.84 kJ mol -1 ) and frequency factor (Log A = -3.97) were also calculated. A suitable mechanism in conformity with kinetic observations was proposed to explain reaction stoichiometry and product analysis.

No abstract

No abstract

No abstract