Question

Identify that disaccharide which will not give brick
red ppt with Fehling's reagent but after acidic
hydrolysis the two sugars will give the same osazone
Sucrose
Maltose
Lactose
Ribose​

Answer 1

Sucrose is that disaccharide which will not give brick red precipitate with Fehlings reagent because it is a non reducing sugar.

In sucrose molecule the two monosaccharide units are held together by a glycosidic linkage between C1 of α-glucose and C2 of β-fructose. Since the reducing groups of glucose and fructose are involved in glycosidic bond formation, sucrose is a non-reducing sugar.

When acidic hydrolysis is done then both glucose and fructose acts as a reducing sugar and give red ppt with Fehlings reagent.

Regards