Question:medium

Glucose does not react with which of the following?

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Which classic reagent fails because glucose has no free aldehyde group (cyclic hemiacetal)?
Updated On: Jul 10, 2026
  • Bromine water
  • \( NaHSO_3 \)
  • \( C_6H_5NHNH_2 \)
  • \( (CH_3CO)_2O \)
Show Solution

The Correct Option is B

Solution and Explanation

Step 1: Recall the anomalies of glucose used to deduce its cyclic structure: it does not give the Schiff test, does not react with \(NaHSO_3\), and its pentaacetate does not react with \(NH_2OH\).
Step 2: These facts prove the aldehyde group is not truly free but tied up as a hemiacetal (ring form).
Step 3: Reagents that still work (bromine water, phenylhydrazine, acetic anhydride) do so via the small open-chain fraction or the hydroxyl groups.
Step 4: The sodium bisulphite addition reaction, however, fails, so glucose does not react with \(NaHSO_3\).
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