JEE Main · 2023 · 11 Apr 2023 · Shift 2 · Biomolecules

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Number of compounds from the following which will not produce orange red precipitate with Benedict solution is ______

Glucose, maltose, sucrose, ribose, 2-deoxyribose, amylose, lactose.

Answer: 2

Solution

Benedict's test detects reducing sugars (free or potentially free aldehyde/ketone groups).

Reducing sugars: Glucose, maltose, ribose, 2-deoxyribose, lactose (all have free anomeric carbons).

Non-reducing sugars: Sucrose (glycosidic linkage between anomeric carbons of both glucose and fructose) and Amylose (polysaccharide with only one reducing end, negligible for the test).

Therefore, 2 compounds (sucrose and amylose) will not produce the orange-red precipitate.

Structure Amylose structure — Amylose structure

Structure Sucrose structure — Sucrose structure

JEE Main · 2023 · 11 Apr 2023 · Shift 2 · Integer answer

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