Aldoses, catalytic oxidation

Uronic acids can be produced by the catalytic oxidation of the primary alcohol of an aldose, provided that the aldehyde group has first been protected, usually as a glycoside. ... 

Catalytic oxidation of partially substituted aldoses has also proved moderately satisfactory. An overall yield of 30% of D-glucuronolactone (XXXVIII) from D-glucose was obtained by catalytic oxidation of 1,2-O-isopropylidene-a-D-glucofuranose (XXXVII) utilising a platinum-activated carbon... 

In perchloric acid, hexoses and pentoses are oxidized by Ce(IV) via formation of two complex intermediates. The first is partly oxidized following Michaelis-Menten kinetics and partly dissociated to the second, which is oxidized more slowly than the former.180 The first step in the oxidation of aldoses by Tl(III) in the same medium involves the C-l-C-2 cleavage of the aldehydo form of the sugar. Thus, D-glucose gives D-arabinose and formic acid. With an excess of oxidant the final product is carbon dioxide.181 In the presence of a catalytic amount of sulfuric acid in acetic acid, Tl(III) oxidizes maltose and lactose to the corresponding disaccharide aldonic acids. The reaction showed activation enthalpies and enthropies characteristic of second-order reactions.182... 

Starting from a salt of an aldonic acid, the Ruff oxidative degradation reaction1 leads to an aldose with loss of one carbon atom. Known since 1898, the original process used aqueous hydrogen peroxide as oxidant, in the presence of catalytic amounts of ferric salts. 

Much is known about the catalytic mechanism of triose phosphate isomerase. TIM catalyzes the transfer of a hydrogen atom from carbon 1 to carbon 2 in converting dihydroxyacetone phosphate into glyceraldehyde 3-phosphate, an intramolecular oxidation-reduction. This isomerization of a ketose into an aldose proceeds through an enediol intermediate (Figure 16.6). 

Also under oxidizing conditions, like the partial oxidation of methanol to hydrogen, water, and CO2, intermetallic compounds can be formed. As in the case of methanol steam reforming over Pd/ZnO, the intermetallic compound ZnPd is part of the catalytic system Pd-Zn/Al203 under these conditions (125). The observation of intermetallic compounds is not limited to oxidation reactions involving methanol. Also in the oxidation of aldoses such as lactose and glucose over... 

Aldoses and alditols can be rapidly oxidized by hydrogen peroxide under certain conditions leading to the formation of formic acid with evolution of oxygen, and a mechanism was proposed involving catalysis by superoxide radicals generated from traces of transition metal salts in Fenton s reaction ferrous ion is considered to play an analogous catalytic role. ... 

The presence of thallium(0) led to an increase in activity and selectivity of metallic palladium catalysts supported on silica in aldose oxidation reactions. However, silica-supported thallium(0) had no activity by itself (entry 3). ° Similarly, the bimetallic catalyst platinum-thallium/ZSM-5, prepared by impregnation of thallium sulfate and chloroplatinic acid on Zeolite Socony Mobil-5 (ZSM-5), showed greater selectivity in propane aromatisation and almost the same catalytic activity as monometallic thallium/ZSM-5 (entry 4). Similar comparison of vanadium-caesium-copper and vanadium-caesium-copper-thallium catalysts supported on TiOa.SiC demonstrated that addition of thallium improved the catalytic activity in partial oxidation of p-tert-butyltoluene to p-tert-butyl-benzaldehyde (entry The application of solid-supported thallium-based catalysts in different processes includes (a) iron-thallium catalysts in carbon monoxide hydrogenations to form hydrocarbons and alcohols, and catalytic reforming of... 

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