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JEE Main · 2022 · 27 Jul 2022 · Shift 1 · Biomolecules

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A sugar ' X ' dehydrates very slowly under acidic condition to give furfural which on further reaction with resorcinol gives the coloured product after sometime. Sugar ' X ' is
  1. (A)Aldopentose✓ Correct
  2. (B)Aldotetrose
  3. (C)Oxalic acid
  4. (D)Ketotetrose

Answer: (A)

Solution

The reaction described is Seliwanoff's test, which distinguishes ketoses from aldoses. However, the question states that sugar X dehydrates very slowly to give furfural, which then reacts with resorcinol to give a colored product.

Aldopentoses (5-carbon aldoses like ribose, xylose) dehydrate under acidic conditions to form furfural. Furfural reacts with resorcinol to give a cherry-red colored product.

Ketoses react rapidly in Seliwanoff's test, while aldoses react slowly. Since the question mentions "very slowly," sugar X is an aldopentose.

Therefore, the answer is (A) Aldopentose.

JEE Main · 2022 · 27 Jul 2022 · Shift 1 · Single correct option

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