Solved previous year question from the OPSC OAS/OCS 2024 Preliminary Examination (General Studies), with the official answer key and a detailed explanation.
Question
Which of the following is a non-reducing sugar:
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Answer & Explanation
Correct answer: (C) Sucrose
Correct Answer: (C) — Sucrose
Sucrose — The Non-Reducing Sugar
A sugar is called reducing if it has a free aldehyde or ketone group (hemiacetal/hemiketal) that can donate electrons to reduce other compounds. Sucrose is a disaccharide formed by the union of glucose and fructose through a 1,2-glycosidic bond that links both their anomeric (reducing) carbon atoms. This means sucrose has no free anomeric carbon, leaving it with no reducing end — making it a classic non-reducing sugar. It therefore fails to react with Fehling’s solution, Benedict’s reagent, or Tollens’ reagent.
