488-30-2Relevant articles and documents
Pd(II)-catalysed and Hg(II)-co-catalysed oxidation of D-glucose and D-fructose by N-bromoacetamide in the presence of perchloric acid: A kinetic and mechanistic study
Singh, Ashok Kumar,Srivastava, Jaya,Rahmani, Shahla,Singh, Vineeta
, p. 397 - 409 (2006)
The kinetics of Pd(II)-catalysed and Hg(II)-co-catalysed oxidation of d-glucose (Glc) and d-fructose (Fru) by N-bromoacetamide (NBA) in the presence of perchloric acid using mercury(II) acetate as a scavenger for Br- ions have been studied. The results show first-order kinetics with respect to NBA at low concentrations, tending to zero order at high concentrations. First-order kinetics with respect to Pd(II) and inverse fractional order in Cl- ions throughout their variation have also been noted. The observed direct proportionality between the first-order rate constant (k 1) and the reducing sugar concentration shows departure from the straight line only at very higher concentration of sugar. Addition of acetamide (NHA) decreases the first-order rate constant while the oxidation rate is not influenced by the change in the ionic strength (μ) of the medium. Variation of [Hg(OAc)2] shows a positive effect on the rate of reaction. The observed negative effect in H+ at lower concentrations tends to an insignificant effect at its higher concentrations. The first-order rate constant decreases with an increase in the dielectric constant of the medium. The various activation parameters have also been evaluated. The products of the reactions were identified as arabinonic acid and formic acid for both the hexoses. A plausible mechanism involving HOBr as the reactive oxidising species, Hg(II) as co-catalyst, and [PdCl3·S]-1 as the reactive Pd(II)-sugar complex in the rate-controlling step is proposed.
Mechanism of Ir(III)-catalysed and Hg(II)-co-catalysed oxidation of reducing sugars by N-bromoacetamide in acidic medium
Singh, Ashok Kumar,Rahmani, Shahla,Singh, Bharat,Singh, Ramesh Kumar,Singh, Manju
, p. 249 - 256 (2004)
The kinetics of Ir(III)-catalysed and Hg(II)-co-catalysed oxidation of D-glucose (Glu) and D-fructose (Fru) by N-bromoacetamide (NBA) were studied in acidic medium. The reactions follow identical kinetics, being zero order in each sugar concentration. The experimental results show a first-order dependence on NBA and Ir(III) at low concentrations, but tending towards zeroth order at higher concentrations. A negative effect of variation of [H+], [Cl-] and [NHA] was observed whereas the ionic strength (I) of the medium has no influence on oxidation rate. The important feature of the reaction is that it follows a second-order dependence on mercury(II) ion concentration at low concentrations, but it tends towards first order at higher concentrations. Various activation parameters were calculated and recorded. The corresponding acids were identified as the main oxidation products of the reaction. On the basis of the experimental findings, a suitable mechanism consistent with the observed kinetics was proposed. A comparative study was also made between the kinetic results of the present investigation and those of Ru(III)- and Pd(II)-catalysed oxidations of reducing sugars. Copyright
A novel and Facile oxidation of d-glucose by n-bromophthalimide in the presence of chloro-complex of ruthenium(III)
Singh, Ajaya Kumar,Sachdev, Neerja,Shrivastava, Alpa,Katre, Yokraj,Singh, Surya P.
, p. 947 - 954 (2010)
Kinetics of oxidation of D-glucose (D-Glu) by N-bromopthalimide (NBP, C8H4O2NBr) in presence of [RuCl 2(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. Copyright Taylor & Francis Group, LLC.
Kinetic and mechanistic investigation of Pd(II)-catalysed and Hg(II)-co-catalysed oxidation of d(+)melibiose by N-bromoacetamide in acidic medium
Singh, Ashok Kumar,Yadav, Sarita,Srivastava, Rashmi,Srivastava, Jaya,Rahmani, Shahla
, p. 2213 - 2219 (2010)
The kinetic and mechanistic study of homogeneously Pd(II)-catalysed and Hg(II)-co-catalysed oxidation of d(+)melibiose (mel) by N-bromoacetamide (NBA) in perchloric acid medium have been made at temperature 40 °C ± 0.1 °C. Kinetic results show first-order kinetics with respect to NBA at its low concentrations, tending to zero-order at its high concentrations. The oxidation rate is directly proportional to [Pd(II)] and [sugar], indicating first-order kinetics with respect to Pd(II) and sugar. Zero effect of Cl- and H+ ions throughout their variation have been noted. First-order kinetics with respect to Hg(II) at its low concentration tends to zero-order at its higher concentration. Addition of acetamide (NHA) decreases the first-order rate constant (k1) while the rate of reaction is not influenced by the change in ionic strength (μ) of the medium. The first-order rate constant decreases with an increase in dielectric constant of the medium. Arabinonic acid, lyxonic acid and formic acid were identified as oxidation products of the reaction. Various activation parameters including the entropy of activation were also calculated. A plausible mechanism conforming to kinetic data, spectrophotometric observations, reaction stoichiometry and product analysis has been proposed.
Alkaline KMnO4 oxidation of reducing sugars in microemulsions: Inhibition effect of surfactants
Tripathi,Upadhyay
, p. 261 - 266 (2015)
The kinetics of oxidation of reducing sugars viz. D-glucose and D-fructose by alkaline KMnO4 in microemulsion media was investigated. The aqueous, cationic microemulsion was prepared from cetyl trimethyl ammonium bromide, n-butanol, n-hexane and water, whereas n-decane, aerosol-OT and water were used to prepare the anionic microemulsion. The order of reaction in oxidant was always found to be unity, while that in substrate and alkali was decreased from unity to zero at higher concentrations substrate and alkalirespectively. On decreasing [H2O]/[Surfactant] ratio (increasing surfactant content) in microemulsion, the observed rates constants of oxidation (k obs) were decreased. The inhibition effect on the rate of oxidation was greater in cationic microemulsion. A mechanism consistent with kinetic data is proposed.
Antagonism in (conventional anionic-gemini anionic) mixed micelle catalyzed oxidation of D-fructose by alkaline chloramine-T: A kinetic study
Kambo, Neelu,Upadhyay, Santosh K.
, p. 123 - 132 (2009)
The catalytic effect of individual conventional anionic surfactant, namely, sodium lauryl sulfate (NaLS), anionic gemini surfactant, namely, sodium salt of bis(1-dodecenyl succinamic acid) (NaBDS), and mixed surfactant (NaLS + NaBDS) on the rate of oxidat
Selective Conversion of Various Monosaccharaides into Sugar Acids by Additive-Free Dehydrogenation in Water
Mollar-Cuni, Andres,Byrne, Joseph P.,Borja, Pilar,Vicent, Cristian,Albrecht, Martin,Mata, Jose A.
, p. 3746 - 3752 (2020/06/01)
Abundant sugars of five and six carbon atoms are promising candidates for the production of valuable platform chemicals. Here, we describe the catalytic dehydrogenation of several pentoses and hexoses into their corresponding sugar acids with the concomitant formation of molecular hydrogen. This biomass transformation is promoted by highly active and selective catalysts based on iridium(III) complexes containing a triazolylidene (trz) as ligand. Monosaccharides are converted into sugar acids in an easy and sustainable manner using only catalyst and water, and in contrast to previously reported procedures, in the absence of any additive. The reaction is therefore very clean, and highly selective, which avoids the tedious purification and product separation. Mechanistic investigations using 1H NMR and UV-vis spectroscopies and ESI mass spectrometry (ESI-MS) indicate the formation of an unprecedented diiridium-hydride as dormant species that correspond to the catalyst resting state.
Upgrading of Biomass Monosaccharides by Immobilized Glucose Dehydrogenase and Xylose Dehydrogenase
Zdarta, Jakub,Pinelo, Manuel,Jesionowski, Teofil,Meyer, Anne S.
, p. 5164 - 5173 (2018/10/25)
Direct upgrading and separation of the monosaccharides from biomass liquors is an overlooked area. In this work we demonstrate enzymatic production of gluconic acid and xylonic acid from glucose and xylose present in pretreated birchwood liquor by glucose dehydrogenase (GDH, EC 1.1.1.47) and xylose dehydrogenase (XDH, EC 1.1.1.175), respectively. The biocatalytic conversions were compared using two different kinds of silica support materials (silica nanoparticles (nanoSiO2) and porous silica particles with hexagonal pores (SBA 15 silica) for enzyme immobilization. Upon immobilization, both enzymes showed significant improvement in their thermal stability and robustness at alkaline pH and exhibited over 50 % activity even at pH 10 and 60 °C on both immobilization matrices. When compared to free enzymes at 45 °C, GDH immobilized on nanoSiO2 and SBA silica displayed a 4.5 and 7.25 fold increase in half-life, respectively, whilst XDH immobilized on nanoSiO2 and SBA showed a 4.7 and 9.5 fold improvement in half-life, respectively. Additionally, after five reaction cycles both nanoSiO2GDH and nanoSiO2XDH retained more than 40 % activity and GDH and XDH immobilized on SBA silica maintained around 50 % of their initial activity resulting in about 1.5–1.6 fold increase in biocatalytic productivity compared to the free enzymes.
Aerobic oxidation of xylose to xylaric acid in water over pt catalysts
Sadula, Sunitha,Saha, Basudeb
, p. 2124 - 2129 (2018/10/20)
Energy-efficient catalytic conversion of biomass intermediates to functional chemicals can make bio-products viable. Herein, we report an efficient and low temperature aerobic oxidation of xylose to xylaric acid, a promising bio-based chemical for the production of glutaric acid, over commercial catalysts in water. Among several heterogeneous catalysts investigated, Pt/ C exhibits the best activity. Systematic variation of reaction parameters in the pH range of 2.5 to 10 suggests that the reaction is fast at higher temperatures but high C C scission of intermediate C5-oxidized products to low carbon carboxylic acids undermines xylaric acid selectivity. The C C cleavage is also high in basic solution. The oxidation at neutral pH and 60 8C achieves the highest xylaric acid yield (64 %). O2 pressure and Pt amount have significant influence on the reactivity. Decar-boxylation of short chain carboxylic acids results in formation of CO2, causing some carbon loss; however, such decarboxyla-tion is slow in the presence of xylose. The catalyst retained comparable activity, in terms of product selectivity, after five cycles with no sign of Pt leaching.
Highly selective photocatalytic oxidation of biomass-derived chemicals to carboxyl compounds over Au/TiO2
Zhou, Baowen,Song, Jinliang,Zhang, Zhanrong,Jiang, Zhiwei,Zhang, Pei,Han, Buxing
, p. 1075 - 1081 (2017/03/17)
Highly selective transformation of biomass-derived chemicals into value-added chemicals is of great importance. In this work, selective photooxidation of various biomass-derived chemicals, including ethanol, glucose, xylose, 2-furaldehyde, 5-hydroxymethyl-2-furfural, and furfuralcohol to the corresponding carboxyl compounds was studied using atmospheric air as the oxidant at ambient temperature. It was found that the reactions could be carried out efficiently over Au nanoparticles (AuNPs) supported on TiO2 (AuNPs/TiO2) under both ultraviolet (UV) and visible light in Na2CO3 aqueous solution. Under the optimized conditions, the selectivities for desired products were higher than 95% for all the reactions. Detailed studies indicated that the surface plasmon resonance of AuNPs and the band-gap photoexcitation of TiO2 were responsible for visible-light-responding and UV-light-responding activities, respectively. Na2CO3 acted as the promoter for the visible-light-induced oxidation and the inhibitor of reactive oxygen species with strong oxidation power under UV light.
