Chemistry - Biomolecules Question with Solution | TestHub
Carbohydrates are polyhydroxy aldehydes or ketones, or substances that yield such compounds upon hydrolysis. In their cyclic forms, they exist as hemiacetals or hemiketals. The structural elucidation of these molecules involves understanding their stereochemistry, ring size, and the nature of their functional groups. A critical aspect of carbohydrate chemistry is the anomeric effect and mutarotation, where the alpha and beta anomers interconvert in solution through an open-chain intermediate. Furthermore, chemical transformations like Kiliani-Fischer synthesis (chain lengthening) and Ruff degradation (chain shortening) are essential tools for determining the configuration of sugars. The "reducing" ability of a sugar depends on the availability of a free hemiacetal group that can open into an aldehyde. If the anomeric carbon is involved in a glycosidic linkage (as in sucrose), the sugar becomes non-reducing.
A certain D -aldopentose ' X ' on reaction with yields an optically active aldaric acid. When ' X ' undergoes Killiani-Fischer synthesis, it yields two aldohexoses ' Y ' and ' Z '. ' Y ' on oxidation with gives an optically inactive aldaric acid, while ' ' gives an optically active one. Identify ' '.
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D-Arabinose: D-Arabinose gives an active aldaric acid. Its extension gives Glucose (inactive/meso aldaric acid) and Mannose (active aldaric acid).
