Fundamentholfundamenthol
JEE Main2026Jan 28, Shift 2Chemistry
Q.

Structures of four disaccharides are given below. Among the given disaccharides, the non-reducing sugar is :

  1. A

    1

  2. B

    2

  3. C

    3

  4. D

    4

Solution

A disaccharide is non-reducing when both monosaccharide units are joined through their anomeric (acetal) carbons, leaving no free hemiacetal -OH to mutarotate and reduce Tollens'/Fehling's reagents.

Structure (1) is sucrose — -D-glucopyranose linked to -D-fructofuranose. Both anomeric carbons are tied up in the glycosidic bond (acetal-acetal linkage), so there is no free hemiacetal and the sugar is non-reducing.

The other three disaccharides each retain a free anomeric -OH (hemiacetal) and are reducing.

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