Which of the following will not reduce Fehling’s solution?

The correct answer is Option (3) → 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 — Reduces Fehling’s solution. The C1 of its second glucose unit is free.

• Option (2) Lactose — Reduces Fehling’s solution. C1 of β-D-galactose is linked to C4 of β-D-glucose, so a free aldehyde group can form at C1 of the glucose unit.

• Option (3) Sucrose — Does not reduce Fehling’s solution. 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).

• Option (4) Fructose — Reduces Fehling’s solution. A monosaccharide with a free ketone group.

NCERT (2026-27 edition):
Disaccharides – …

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