Oxidation of reducing sugars

Oxidations of reducing sugars with lead tetraacetate have been re-examined more recently.131 133 At 0°, or at 25°, in acetic acid and in the presence of excess lead tetraacetate, one mole of D-glucose took up only two moles of oxidant132- 133 (see Fig. 4), as had been observed by Hockett and Zief. The product of this reaction was not a triose derivative (LI) but a diformate ester of D-erythrose.132 (Oxidation of D-glucose with a limited pro-... 

The rate of oxidation of reducing sugars by cupric ion is found to be proportional to sugar and [OH ] and to be independent of [Cu ]. What does the kinetics suggest about the mechanism of oxidation ... 

Figure 7.28 Formation of semidiones from oxidation of reducing sugars.

In the oxidation of reducing sugars, periodate and lead tetraacetate frequently act quite differently. These differences can usually be traced to differences in the rates of oxidation of (a) the various forms that the sugars assume in solution and... 

A. S. Perlin, Ring contraction during the lead tetraacetate oxidation of reducing sugars. Can. J. Chem., 42 (1964) 2365-2374. 

A review on metal-ion oxidations of reducing sugars and kinetic approaches to mechanisms has appeared. 

The complexation of free sugars with metal ions (e.g. Ca + and La + ions) in aqueous solution is referred to in Chapter 18, and the mechanism of oxidation of reducing sugars by molecular oxygen is discussed in Chapter 22. 

Oxidation of the aldehyde group of an aldose to form a carboxyUc acid or carboxyUc acid anion is often used analytically to determine the amount of reducing sugar. The Benedict and Fehling methods measure the amount of reducing sugar present in a fluid. In these reactions, the oxidant, Cu ", is reduced to Cu". Cu" precipitates as CU2O, which can be measured in a variety of ways. In the ToUens test, Ag" is reduced to Ag. ... 

Rates of Enolization Reactions. For a better understanding of the transformation and oxidation reactions of reducing sugars, methods have been developed to measure the primary rates of enolization (18). One of these methods depends on the rate at which tritium ions are released from aldoses-2- to the solvent. This is measured by separation of the water-, sublimation, and radiochemical assay of the water as the reaction proceeds. The rate constant is calculated from the first-order equation ... 

In the Somogyi-Nelson assay, all substances with reducing or oxidative properties might cause interference. The most important factor to consider is the back-oxidation by air. To control air oxidation, sodium sulfate is added during the process. In addition, citric acid has been reported to cause interference in the estimation of reducing sugars (Paleg, 1959). 

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