Kinetics of oxidation of d(+)melibiose and cellobiose by N-bromoacetamide using a rhodium(III) chloride catalyst

Abstract

The kinetics of oxidation of the sugars D(?)Melibiose (mel) and Cellobiose (cel) by N-bromoacetamide (NBA) in the presence of Rh(III) chloride as homogeneous catalyst in acidic medium at 45°C have been investigated. The reactions are first-order with respect to [NBA], [Rh(III)] and [substrate]. The rate is proportional to [H ? ]. No effects of [Hg(II)], [NHA] or [Cl -] on the rates were observed. Ionic strength and dielectric constant also have little effect. The observed kinetic data, available literature and spectroscopic evidence lead us to conclude that NBAH ? and [RhCl 5 (H 2 O)] 2-are the reactive species of NBA and Rh(III) chloride, respectively. The rate-determining step of the proposed reaction path common for both sugars gives an activated complex by the interaction of a charged complex species and neutral sugar molecule, which in the subsequent steps disproportionates into the reaction products with the regeneration of catalyst. The reactions have been studied at four different temperatures and with the help of first-order rate constant values, various activation parameters have been calculated. The main oxidation products of the reactions were identified as arabinonic acid, formic acid and lyxonic acid in the case of mel and arabinonic acid and formic acid in the case of cel.

Kinetic and mechanistic investigation of Pd(II)-catalysed and Hg(II)-co-catalysed oxidation of d(+)melibiose by N-bromoacetamide in acidic medium

“…N-bromoacetamide has been used as an oxidant in Ru(III) [5]-, Ir (III) [2]-and Pd(II) [15]-catalysed oxidation of reducing sugars in acidic medium. In each case, it has been observed that HOBr is the main reactive species of NBA.…”

“…(3) The role of reducing sugar molecule in the presence of Pd(II) chloride as catalyst and NBA as an oxidant in acidic medium is similar to the reported role of reducing sugar in the presence of Ir(III)/Ru(III) chloride and NBA in acidic medium. (4) Pd(II) chloride in acidic medium participates in the reaction under investigation in the same way as it is reported in Ru(III) [5]-and Ir(III) [2]-catalyzed oxidation of reducing sugars by NBA in acidic medium. …”

“…In this study our main aim was to ascertain whether-(1) NBA as an oxidant in acidic medium behaves in the same way as it behaved in the reported Ru(III) [5]-and Ir(III) [2]-catalyzed oxidation of reducing sugars. (2) HOBr is the reactive species of NBA in acidic medium in the present investigation as is reported in Ru(III) [5]-and Ir(III) [2]catalyzed oxidation of reducing sugars by NBA in acidic medium or not? (3) The role of reducing sugar molecule in the presence of Pd(II) chloride as catalyst and NBA as an oxidant in acidic medium is similar to the reported role of reducing sugar in the presence of Ir(III)/Ru(III) chloride and NBA in acidic medium.…”

Role of Ru(III) as Inhibitor in Oxidation of Arabinose and Ribose by [Cu(bipy)2]2+ in Alkaline Medium: Spectrophotometric and Kinetic Studies

“…2+ in Alkaline Medium: Spectrophotometric and Kinetic Studies of some simple reducing sugars have been studied using various transition metals like Cr(VI), Cu(II), Fe(III), Ir(III), Rh(III), Pd(II), Ru(III) [21][22][23][24][25][26]. The kinetics of oxidation of sugars has been the most popular and interesting research in recent years [27][28][29][30].…”

Removal of Orange G from aqueous solution by hematite: Isotherm and mass transfer studies

“…The dye is also important to pathologists [1]. Colored dye waste frequently contains a spectrum of metals and other toxic organic pollutants [2] including dyes and the presence of dye colors may indicate the existence of toxicants [3]. It is the disodium salt of benzene-azo-6:8-disulphuric acid and its molecular structure is shown in Fig.…”