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JEE Main · 2021 · 18 Mar 2021 · Shift 1 · Biomolecules

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A non-reducing sugar "A" hydrolyses to give two reducing mono saccharides. Sugar A is:
  1. (A)Galactose
  2. (B)Fructose
  3. (C)Glucose
  4. (D)Sucrose✓ Correct

Answer: (D)

Solution

A sugar reduces Tollens' or Fehling's reagent only if it still has a free anomeric carbon that can open to an aldehyde. In sucrose the glycosidic bond joins C-1 of glucose to C-2 of fructose, locking both anomeric centres, so the disaccharide is non-reducing. Hydrolysis breaks that linkage and sets free glucose and fructose, each with an available anomeric carbon and therefore reducing. The sugar A is sucrose.

JEE Main · 2021 · 18 Mar 2021 · Shift 1 · Single correct option

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