Which of the following sugar is non-reducing?

The correct answer is Option (4) → Sucrose

A reducing sugar reduces Fehling’s solution and Tollens’ reagent. It can do so only if it has a free aldehyde or ketone group (a free hemiacetal carbon that can open to the carbonyl form). All monosaccharides are reducing sugars. A disaccharide is reducing only if one of its units still has this group free after the glycosidic linkage is formed.

• Option (1) Maltose — A reducing sugar. Two α-D-glucose units are joined C1 to C4; the C1 of the second glucose unit is free.

• Option (2) Lactose — A reducing sugar. β-D-galactose and β-D-glucose are joined C1 to C4; the C1 of the glucose unit is free.

• Option (3) Glucose — A reducing sugar. A monosaccharide with a free aldehyde group.

• Option (4) Sucrose — Not a reducing sugar. C1 of α-D-glucose is joined to C2 of β-D-fructose, so both reducing groups are used in the linkage. On hydrolysis it gives the two reducing monosaccharides: \( \ce{C12H22O11 + H2O -> C6H12O6 + C6H12O6} \) (D-(+)-glucose and D-(−)-fructose).

NCERT (2026-27 edition):
Disaccharides – …

Note: The same/similar question has been asked in different years by NTA as per the details given below: