Showing papers by "Ajaya Kumar Singh published in 2010"

Kinetic study of the ruthenium(III)-catalyzed oxidation of glycine by N -bromophthalimide in acidic medium

Abstract: The kinetics of ruthenium(III) chloride-catalyzed oxidation of glycine by N–bromophthalimide (NBP) was studied in aqueous perchloric acid at 35 °C. The results showed first- and zero-order behavior with respect to NBP and Gly, respectively. Ru(III) showed a catalytic effect on the reaction which followed first-order kinetics with respect to [Ru(III)] at a low concentration range and tended to zero order at high concentration range. The rates decreased with increase in the proton concentration, while chloride positively influenced the rate of the reaction. Two moles of NBP were required to oxidize one mole of Gly, and the products were identified as phthalimide (NHP), HCN, CO2, and Br−. Neither added NHP nor Br− influenced the reaction rate. Ionic strength and dielectric constant of the medium had no significant effect on the rate. Activation parameters were determined by studying the reaction at different temperatures. A reaction scheme of the catalytic oxidation is proposed.

Kinetic Study of Oxidation of Valine by N-bromophthalimide in Presence of Iridium (III) Chloride as Homogenous Catalyst

Abstract: The mechanistic study of Ir(III) chloride catalyzed oxidation of Val has been studied by by N-bromophthalimide (NBP) in aqueous perchloric acid medium at 303 K. The reaction followed first order kinetics with respect to [NBP] and zero order kinetics with respect to [Val]. At lower concentration range of Ir(III) chloride, the reaction followed first order kinetics while tending to zero order at its higher concentration. A negative effect was observed for [H+] and [NHP] (phthalimide) whereas variation in [Hg(OAc)2] (mercuric acetate), [Cl−], ionic strength (I) and dielectric constant of the medium did not bring about any significant change on the rate of reaction. The rate constants observed at five different temperatures (298 K–318 K) were used to calculate the activation parameters. A plausible mechanism from the results of kinetic studies, reaction stoichiometry and product analysis has been proposed.

A Novel and Facile Oxidation of D-glucose by N-bromophthalimide in the Presence of Chloro-complex of Ruthenium(III)

Abstract: Kinetics of oxidation of D-glucose (D-Glu) by N-bromopthalimide (NBP, C8H4O2NBr) in presence of [RuCl2(H2O)3OH] 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.

Effect of Micellar Aggregates on the Kinetics of Dextrose Oxidation by N-Bromosuccinimide

Abstract: The kinetics of oxidation of dextrose by N-bromosuccinimide (NBS) has been investigated in the presence of cationic cetyltrimethylammonium bromide (CTAB) surfactant in sulfuric acid (H2SO4) medium. Similarly in absence of CTAB solution, the reaction followed fractional-, first-, and negative fractional-order kinetics with respect to [dextrose], [NBS] and [H2SO4], respectively. Although the reaction mechanism remained unaltered by micelles, a typical kψ-[CTAB] profile was observed, that is, with a progressive increase in [CTAB], the reaction rate increased, reached a maximum value, and then decreased. The results are treated quantitatively in terms of Berezin's model. Activation parameters were also evaluated and a negative value of ΔS# shows the formation of well-structured activated complex. The influence of salts on the reaction rates has also been seen. On the basis of product analysis, a pertinent mechanism is proposed.