Platinum sucrose oxidation

Edye L.A., Meechan, G.V., and Richards, G.N., Platinum catalysed oxidation of sucrose, Carbohydrate Chem., 10, 11-23, 1991. 

The direct electrooxidation of aqueous E>-g]uconic acid to l>arabinose on graphite has been performed in a very simple apparatus which may be suitable for practical application. The electrocatalytic oxidation of sucrose on smooth, lead-modified platinum electrodes has been examined with a view to finding experimental conditions for the selective electrosynthesis of value-added compounds. A paper in Bulgarian on the electrooxidation of diacetone-L-sorbose at low current densities in a nickel oxide electrolizer has been publi ed. The influence of the rize of palladium particles and their location on the support on their activity in the oxidation of glucose has been examined. An investigation of the effect of tonperature and pH on the platinum-catalysed oxidation of sucrose showed that changes in temperature affect mainly the reaction rate, where changes in pH alter the selectivity. ... 

Catalytic oxidation ia the presence of metals is claimed as both nonspecific and specific for the 6-hydoxyl depending on the metals used and the conditions employed for the oxidation. Nonspecific oxidation is achieved with silver or copper and oxygen (243), and noble metals with bismuth and oxygen (244). Specific oxidation is claimed with platinum at pH 6—10 ia water ia the presence of oxygen (245). Related patents to water-soluble carboxylated derivatives of starch are Hoechst s on the oxidation of ethoxylated starch and another on the oxidation of sucrose to a tricarboxyhc acid. AH the oxidations are specific to primary hydroxyls and are with a platinum catalyst at pH near neutraUty ia the presence of oxygen (246,247). Polysaccharides as raw materials ia the detergent iadustry have been reviewed (248). 

Oxidation of Sucrose. Sucrose can be oxidized by HNO, KMnO, and peroxide. Under selected conditions using oxygen with palladium or platinum, the 6- or 6 -hydroxyls can be oxidized to form sucronic acid derivatives (29). 

Platinum supported on carbon (Pt/C) was tested as solid catalysts in the oxidation of sucrose using molecular oxygen as oxidant (Scheme 10). The reaction was carried out in water and under atmospheric pressure. The support strongly influences the reaction and Pt/C was found more efficient than Pt/Alumina at 353 K. Over Pt/C, at a pH of 9, mono-, di-, and tricarboxylate derivatives were mainly obtained with a tricarboxylate yield of 35% [103]. 

Selective electrocatalytic oxidation of sucrose on smooth and upd-lead modified platinum electrodes in alkaline medium. 

This work aims to investigate the electrocatalytic oxidation of sucrose on smooth and upd-lead modified platinum electrodes in order to find experimental conditions for selective electrosynthesis of high value added products. The preliminary results obtained show that the oxidation of sucrose on Pt-Pb electrodes leads mainly to C12 products, such as the I -monoacid and the 6-monoacid of sucrose. 

The electrocatal3rtic oxidation of sucrose has only been the subject of a few investigations. The chemical oxidation of sucrose was firstly mentioned in the works of Bresler (1) and Usch (2). Karabinos (3) analysed the oxidation products of fructose, glucose, glucono-y-lactone and sucrose in 0.5 M NaHCOa. The author concluded that the main reaction products were CO2 and H2O. Bockris et al. (4), investigated the electrochemical oxidation of different carbohydrates at platinum electrodes for their possible use in fuel cells. They noticed that the electroactivity was better in alkaline medium than in acidic medium, and that the reactivity of the molecule decreased with increasing molecular weights. 

The electrocatalytic oxidation of sucrose on platinum and other metal electrodes is mentioned in a previous paper (12). 

In the case of the electrocatalytic oxidation of sucrose at a platinum electrode... 

Table 1. Oxidation products of sucrose obtained on a platinum electrode.

The conversion 3deld at the end of the electrolysis was very low (5%). However, these first results allowed us to identify the oxidation products of sucrose on a smooth platinum electrode. Particularly, it was important to confirm that it is possible to oxidize sucrose without breaking the acetalic bond. 

Figure 4. Electrocatalytic oxidation of sucrose at an upd-Tead modified platinum electrode. Selectivity (S) in I -MAS and 6-MAS for different concentrations of the precursor salt of lead adatoms...

The catalytic oxidation of the carbohydrates in the presence of Cu(II) for the detection of sucrose, galactose, and fructose was exploited using a Teflon-coated platinum wire plated with copper as the working electrode. Therefore, the addition of copper ions in the run buffer increased the sensitivity to an order of magnitude compared to run buffer without copper. Detection limits were 1 pmol 1 ... 

In an investigation of the transition metal-catalysed oxidation of sucrose by oxygen, high selectivity for OH-6 and OH-6 was observed with platinum on carbon at KXPC and neutral pH, with no evidence of reaction at OH-T. ... 

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