Aldonic acids solubilities

Acetylated nitriles of the aldonic acids are crystalline solids that are very soluble in most nonpolar organic solvents (chloroform, ether, benzene), less soluble in the alcohols usually employed for recrystallization, and almost insoluble in cold water some compounds have a remarkably high solubility in water at elevated temperatures. 

Its preponderance in the synthesis, high dextrorotation ([a]n +50°, equilibrium) and the low solubility of the phenylhydrazide of its aldonic acid are good signs that it resembles D-galactose rather than D-talose. 

Of the methods available for shortening the carbon chain of sugars, the Ruff degradation is generally one of the most facile. A soluble salt of a chosen aldonic acid is treated with hydrogen peroxide in the presence of... 

This method involves the oxidation of aldoses to aldonic acids by potassium hypoiodite in methanol and the condensation of the isolated potassium salt of the aldonic acid in hot acid with o-phenylenediamine (M3). The specific aldobenzimidazole can be identified by the solubility in water, optical rotation in acid, and melting point. This method is not as simple as chromatography. It requires dehydration of the sample and a relatively high concentration of the sugars to be identified. 

One of the most useful methods for shortening the carbon chain of a sugar involves oxidation of a soluble salt of the aldonic acid with hydrogen peroxide in the presence of ferric acetate 184), Prior to the development of this method by Ruff, H. J. H. Fenton had shown that tartaric acid is oxidized by hydrogen peroxide in the presence of ferrous salts, but apparently no oxidative cleavage of carbon-carbon bonds was noted. The ferrous ion-catalyzed oxidation was extended to many carbohydrates by associates of Fenton (Chapter VI) and by other workers 185), The ferric ions used as the catalyst in the Ruff method permit the oxidation of aldonic acids but are inactive with respect to sugars. Ferrous ions are much less selective. 

The aldonic acids, especially gluconic acid in the form of soluble salts, are important as cation sequestering agents for the purpose of introducing appropriate metallic ions such as iron, bismuth, and particularly calcium into the body in a neutral and easily assimilable form. Calcium lactobio-nate CaBr2 may have value as a sedative. 

Aldonic acids (e.g. melibionic and gentiobionic acids) derived from reducing disaccharides have been coupled to the amino-groups of proteins with the aid of a water-soluble carbodi-imide/ The immunochemical properties of some of the synthetic glycoproteins were assessed using plant agglutinins and antibodies raised towards the conjugates. 

The salts and lactones of the aldonic and saccharic acids react readily with phenylhydrazine to form the hydrazides 48) The low solubility and ease of crystallization of the hydrazides have led to their use for the characterization and isolation of the acids. Aniline reacts in a manner similar to phenylhydrazine. 

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