Sugar which does not give reddish brown precipitate with Fehling's reagent, is :
- Glucose
- Sucrose
- Lactose
- Maltose
Answer
(2) Sucrose
Solution
Fehling's test (red-brown Cu2O) is given by reducing sugars (free hemiacetal / –CHO group)
Sucrose: glycosidic link between C1 of α-glucose and C2 of β-fructose
∵ both reducing groups are used in the bond ⇒ no free hemiacetal ⇒ non-reducing
Glucose, lactose, maltose have a free hemiacetal group ⇒ reducing
Answer: (2)