Dolbier HW Solutions 619

Dolbier HW Solutions 619 - 713 CARBOHYDRATES(b All the...

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( b ) All the aldonic acids and their lactones obtained on oxidation of the aldohexoses are optically active. The presence of a carboxyl group at one end of the carbon chain and a CH 2 OH at the other precludes the existence of meso forms. ( c ) Nitric acid oxidation of aldoses converts them to aldaric acids. The same D -aldoses found to yield optically inactive alditols in part ( a ) yield optically inactive aldaric acids. ( d ) Aldoses that differ in con f guration only at C-2 enolize to the same enediol. The stereogenic center at C-2 in the D -aldose becomes sp 2 -hybridized in the enediol. The other pairs of D -aldohexoses that form the same enediols are D -Glucose and D -mannose D -Gulose and D -idose D -Galactose and D -talose 25.20 ( a ) To unravel a pyranose form, locate the anomeric carbon and mentally convert the hemiacetal
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