JEE Main · 2022 · Shift-ImediumBIO-031

Which one of the following is a reducing sugar?

Biomolecules · Class 12 · JEE Main Previous Year Question

Question

Which one of the following is a reducing sugar? image

Options
  1. a

    Option a

  2. b

    Option b

  3. c

    Option c

  4. d

    Option d

Correct Answera

Option a

Detailed Solution

Step 1: Identifying Reducing Sugars — A reducing sugar must have a free hemiacetal or hemiketal group (an \ceOH-\ce{OH} group on the anomeric carbon).

Step 2: Checking the Options — We analyze each structure in the image to locate a free anomeric position that can open into an aldehyde or ketone.

Step 3: Conclusion — In structure (a), the free hemiacetal group allows it to reduce Tollen’s\text{Tollen's} or Fehling’s\text{Fehling's} reagent. Thus, (a) is a reducing sugar.

Key Point: Non-reducing sugars have their anomeric carbons locked in glycosidic linkages.

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