16533-48-5Relevant articles and documents
Direct Oxidation of L-Sorbose to 2-Keto-L-gulonic Acid with Molecular Oxygen on Platinum- and Palladium-Based Catalysts
Broennimann, C.,Bodnar, Z.,Hug, P.,Mallat, T.,Baiker, A.
, p. 199 - 211 (1994)
The selective oxidation of the C1 hydroxyl group of L-sorbose to a carboxylic group without protection of the four other hydroxyl functions was investigated.The reactions were performed in slightly alkaline aqueous solutions with molecular oxygen over various alumina- and carbon-supported Pt and Pd catalysts.Optimum reaction conditions were 50 deg C, pH 7.3, and a catalyst:reactant ratio of 1:4 (wt/wt).The lower the pH and the temperature, the higher the selectivity toward 2-keto-L-gulonic acid.Catalyst deactivation was also found to increase with lower pH and temperature.A 5 wtpercent Pt/alumina catalyst showed the best catalytic performance (67percent selectivity at 58percent conversion).Promotion with Bi or Pb had a detrimental effect on selectivity for 2-keto-L-gulonic acid.Electrochemical measurements indicated that the reaction occurs in a rather narrow potential range, which corresponds to a moderate oxygen coverage of Pt or Pd.Four types of catalyst deactivation processes were identified, based on XPS and ICP-AES analysis and on the in situ determination of the oxidation state by monitoring the catalyst potential during reaction.A significant chemical poisoning of the active noble metal sites occurred during the initial, destructive adsorption of L-sorbose and during the oxidation reaction.The successive contamination of active sites resulted in overoxidation (too high oxygen coverage of Pt or Pd).The partially oxidized promoters and noble metals were corroded and dissolved in the presence of 2-keto-L-gulonic acid, resulting in an irreversible deactivation.
Platinum-containing hyper-cross-linked polystyrene as a modifier-free selective catalyst for L-sorbose oxidation
Sidorov,Volkov,Davankov,Tsyurupa,Valetsky,Bronstein,Karlinsey,Zwanziger,Matveeva,Sulman,Lakina,Wilder,Spontak
, p. 10502 - 10510 (2001)
Impregnation of hyper-cross-linked polystyrene (HPS) with tetrahydrofuran (THF) or methanol (ML) solutions containing platinic acid results in the formation of Pt(II) complexes within the nanocavities of HPS. Subsequent reduction of the complexes by Hsub
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Reichstein,Gruessner
, p. 311,319 (1934)
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Localized Basification of Catalytic Surfaces enhances the Selective Oxidation of L-Sorbose over Supported Pt Catalysts modified with Tertiary Amines
Broennimann, C.,Mallat, T.,Baiker, A.
, p. 1377 - 1378 (1995)
Modification of supported Pt catalysts with strongly adsorbing tertiary amines is shown to be an efficient method to increase the reaction rate in the direct oxidation of L-sorbose to 2-keto-L-gulonic acid with molecular oxygen, and to increase the selectivity of the base-sensitive reaction.
A new synthesis of L-ascorbic acid (vitamin C) from protected derivatives of D-glucitol
Garcia,Velasco,Barba
, p. 1153 - 1161 (1991)
Indirect, anodic oxidation of 1,3,2,4-diacetals of D-glucitol, leads to the 3,5,4,6-diacetals of 2-keto-L-gulonic acid. Hydrolysis of which provides L-xylo-2-hexulosonic acid and hence L-ascorbic acid by lactonization.
Selective oxidation of L-sorbose in the synthesis of L-ascorbic acid
Lakina,Sul'man,Matveeva,Mikhailov
, p. 138 - 140 (2000)
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Oxidation of carbohydrates of biological importance by the aquachromium(IV) ion
González, Juan Carlos,Mangiameli, María Florencia,Asis, Agostina Crotta,Bellú, Sebastián,Sala, Luis F.
, p. 84 - 92 (2013/03/28)
The oxidation reactions kinetics of a series of related saccharides by aqua-oxo chromium(IV) ion, (H2O)5CrIVO 2+, were carried out in perchloric acid aqueous solutions. These reactions yield superoxochromium(III) ion, CrO22+, providing evidence that the two-electron reduction of CrO2+ to Cr2+ occurred in a single step. In all of these reactions, Cr 2+ is the immediate product and could be trapped as CrO 22+ when an excess of oxygen was present. The bimolecular rate constants for different aldoses and d-glucitol are independent of [H +] in the range 0.1-1.0 M. Relative reactivities of these saccharides toward CrO2+ reduction are 1-methyl-α-d-glucopyranose 2+ showed the same mechanism but the redox process is strongly inhibited when [H+] increases. Activation parameters were also determined for selected reactions. On the basis of the kinetic result, activation parameters data and oxidized organic products, the mechanism of saccharides oxidation by CrO2+ is proposed to be a direct hydride-ion transfer.
