(b)All the aldonic acids and their lactones obtained on oxidation of the aldohexoses are opticallyactive. The presence of a carboxyl group at one end of the carbon chain and a CH2OH at theother precludes the existence of meso forms.(c)Nitric acid oxidation of aldoses converts them to aldaric acids. The same D-aldoses found toyield optically inactive alditols in part (a) yield optically inactive aldaric acids.(d)Aldoses that differ in confguration only at C-2 enolize to the same enediol.The stereogenic center at C-2 in the D-aldose becomes sp2-hybridized in the enediol.The other pairs of D-aldohexoses that form the same enediols areD-Glucose and D-mannoseD-Gulose and D-idoseD-Galactose and D-talose25.20(a)To unravel a pyranose form, locate the anomeric carbon and mentally convert the hemiacetal
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