Of D-gluconic acid

Electrochemical Decarboxylations Investigated in Micro Reactors Organic synthesis 86 [OS 86] Electrochemical cecarboxylation of D-gluconic acid... 

Figure 4.95 Faradaic current efficiency as electrical charge equivalent for conversion of D-gluconic acid given for two values of average current density. The symbols represent measured conversion and the solid and dashed lines calculated results [65. ...

OS 86] ]R 29] ]P 66] A model is able to describe experimental results obtained for the electrochemical decarboxylation of D-gluconic acid (1 A mT ) [65]. At an average electrical current of 5 A m the model predicts better performance than is actually achieved. 

The second procedure, and probably the more effective [if, as here, the desired product is L-xy/o-2-hexulosonic acid (28)], is based on simultaneous, fermentative oxidation of L-idonic acid (42) to 28, and fermentative decomposition of D-gluconic acid (86). Efforts directed toward the simultaneous oxidation of 42 and decomposition of D-gluconic acid will be summarized, as well as efforts made to convert 42 efficiently into 28 by fermentative oxidation. 

The rates of hydrolysis of the lactones depend on the parent structure for instance, the 1,4-lactone of D-mannonic acid is more stable than that of D-gluconic acid, and the 1,4-lactones of 2-deoxyaldonic acids are more stable than the corresponding aldonolactones. The final attainment of equilibrium between free aldonic acids and their lactones is reached only after many days at room temperature it is, however, accelerated by the presence of strong acids and by heating. A detailed discussion of the formation and hydrolysis of aldonolactones is available in a review by Shafizadeh,59 and the conformations and stabilities of aldonolactones have been discussed by Lemieux.60 Detailed analyses of D-glucono-1,5-lactone and other lactones have been reported.61 13C NMR spectroscopy proved to be a convenient method for monitoring the equilibria.62... 

Fully acetylated aldonyl chlorides have been prepared by treatment of acetylated aldonic acids with phosphorus pentachloride87 or thionyl chloride.88 Dichloromethyl methyl ether was later shown to afford the derivative of D-gluconic acid in almost quantitative yield.89... 

The electrocatalytic oxidation of D-gluconic acid at an ubiquinine-mixed carbon paste electrode with an immobilized layer of D-gluconate dehydrogenase has been described.259... 

The oxidation of secondary hydroxyl functions to the carbonyl group is often an undesired side reaction. However, the oxidation of D-gluconic acid to 2-oxogluconic acid is a highly selective process (97% yield) when a Pt-Bi catalyst is employed.89 Such a procedure is of industrial interest. 

Tiemann studied the further oxidation of D-gluconic acid with bromine at 100 a reducing sirup was formed which was isolated as an amorphous barium salt or a crystalline osazone. Ruff repeated the work and could find no oxygluconic acid in the oxidation mixture most of the D-gluconic acid was unaltered and the reducing power was very low, especially in comparison with that obtained when keto aldonic acids were prepared by the action of hydrogen peroxide and ferrous salts. By ether extraction and distillation the formation of formic, oxalic and glycolic acids was shown. 

Herzfeld reported a certain amount of oxidation on carbon atom six, as indicated by the formation of saccharic acid from D-glucose. The dicarboxylic acid was isolated from the normal oxidation mixture obtained in the preparation of D-gluconic acid from D-glucose or maltose. However, the reaction products were processed differently than usual following the procedure of Grieshammer, the acidic reaction mixture was neutralized with zinc carbonate instead of calcium or lead carbonate. Thus, the saccharic acid, which normally would be precipitated as an... 

It was pointed out that N-methyl-L-glucosaminic acid nitrile was only the second nitrile in the sugar series to be isolated in the cyanohydrin reaction and that extension of the general procedure by which it was prepared should result in the isolation of other members. The nitrile of N-methyl-L-glucosaminic acid showed the same unusual mutarotation as does that of the lower-melting form of D-gluconic acid nitrile. Wolfrom and Thompson have noted that N-methyl-L-glucosaminic acid nitrile hydrochloride was a much more stable compound than the free base. 

These data indicate that the rate of hydrolysis of the lactones is also, to a considerable extent, affected by the stereoisomerism of the molecule. For instance, the lactones of n-mannonic acid are more stable than those of D-gluconic acid, from which they only differ in the steric position of the hydroxyl group at C2. A mixture of n-glucono-1,4-lactone and n-mannono-1,4-lactone can be fractionated by the absorption, on an anion-exchange... 

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