Oxidation of d-glucose by N-bromophthalimide in the presence of chlorocomplex of iridium(III): a kinetic and mechanistic study

Abstract

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.

Kinetics and mechanisms of oxidation of d-fructose and d-lactose by permanganate ion in acidic medium

“…In catalyzed oxidation of lactose in an acidic medium, since the solution of catalyst was prepared in the water therefore it was reasonable to assume that the reactive specie of catalyst is [Hg(H 2 O) 6 ] +2 [19,20].…”

A Review of some catalysts and promoters used in organic transformations

“…[88] Das et al reported chlorocomplex of Ir(III) as efficient catalyst for oxidation of D-glucose by N-bromophthalimide. [89]…”

Oxidative behavior of N-bromophthalimide for organic compounds: a review

“…By literature, we found several articles on the oxidation of several organic compounds NBP in transition metal catalyzed system in acidic and alkaline medium, i.e., d-glucose [76,77], d-fructose [78], glycine [79,80], valine [81][82][83], β-alanine [84], leucine [85], d-arabinose [86].…”