Monosaccharides nitric acid oxidation

Vigorous oxidation of a monosaccharide (e.g., with dUute nitric acid) produces carboxyl groups at both ends of the chain. Thus galactose gives the sparingly soluble mucic acid glucose affords the soluble saccharic acid, which is best isolated as the sparingly soluble acid potassium salt. 

Monosaccharides such as glucose and fmctose are the most suitable as starting materials. When starch is used, it is first hydrolyzed with oxahc acid or sulfuric acid into a monosaccharide, mainly glucose. It is then oxidized with nitric acid in an approximately 50% sulfuric acid solution at 63—85°C in the presence of a mixed catalyst of vanadium pentoxide and iron(III) sulfate. 

There are two possible routes for DLSA preparation 1). They are available by oxidation of the corresponding monosaccharides with nitric acid (16). This reaction generates relatively low yields in the range of 40%. 

Show the products of the common reactions of monosaccharides that were presented in this chapter oxidation with nitric acid, oxidation with bromine, reduction with... 

Oxidation of secondary hydroxyl groups at C-2 and C-3 leads to acyclic dialde-hydes and dicarboxylic derivatives. Selective oxidation of primary hydroxyl groups is more difficult, but can be achieved by stoichiometric as well as catalytic methods. Nitric acid oxidizes monosaccharides into aldaric acids. Oxidation of cellulose or starch by nitrogen dioxide (N2O4) yields 6-carboxy starch and 6-carboxycellulose respectively. Subsequent hydrolysis under well-controlled conditions (0.5-2 M HCl at 150 °C) of these materials yields o-glucuronic acid (o-GlcAp) [12]. 

If the anomeric centre is not protected, TEMPO-mediated oxidations of monosaccharides with CI2 or Br2 yield aldaric acids, i.e. co-diacids in which the all secondary hydroxyl groups are preserved the use of the 4-acetamido derivative of TEMPO is to be preferred because of its greater stability and lower volatility. This method of making aldaric (saccharic) acids supersedes the use of nitric acid, used in Emil Fischer s classical work to make both ends of... 

A D-aldopentose is oxidized by nitric acid to an optically active aldaric acid. A Ruff degradation of the aldopentose leads to a monosaccharide that is oxidized by nitric acid to an optically inactive aldaric acid. Identify the D-aldopentose. 

A number of oxidizing agents are used to identify functional groups of carbohydrates, in elucidating their structures, and for syntheses. The most important are (1) Benedicts or Tollens reagents, (2) bromine water, (3) nitric acid, and (4) periodic acid. Each of these reagents produces a different and usually specific effect when it is allowed to react with a monosaccharide. We shall now examine what these effects are. 

Full oxidation of monosaccharides by nitric acid to aldaric acids has been an established technique for more than a century. Analogously, oxidation of polysaccharides such as cellulose or starch by nitrogen dioxide (N2O4) yields 6-carboxy starch and 6-carboxycellulose respectively [84]. Subsequent hydrolysis at rigorous conditions (0.5-2M HCl at 150°C) of these materials yields D-glucuronic acid. A drawback of the oxidation with nitrogen dioxide is that depolymerisation may be an important side reaction. An improvement of the process with respect to this aspect can be achieved by conducting the reaction when the polysaccharide is dissolved In 85% phosphoric acid and with sodium nitrite as the oxidant better yield versus a more Important depolymerisation [85-86]. 

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