JEE Main 2025 — Biomolecules Question with Solution
From: JEE Main 2025 (Online) 28th January Morning Shift
Question
Given below are two statements:
Statement I : D-glucose pentaacetate reacts with 2,4 -dinitrophenylhydrazine
Statement II : Starch, on heating with concentrated sulfuric acid at and pressure produces glucose.
In the light of the above statements, choose the correct answer from the options given below
Choose an option
Show full solutionCorrect option: C
Step-by-step explanation
Statement I: D-glucose pentaacetate does not react with 2,4-dinitrophenylhydrazine (DNPH). This is because D-glucose pentaacetate is a derivative where all the hydroxyl groups of D-glucose have been acetylated, eliminating the presence of a free aldehyde group. Since DNPH reacts specifically with free aldehyde or ketone groups to form hydrazones, D-glucose pentaacetate does not participate in this reaction.
Statement II: Starch, when heated with concentrated sulfuric acid at 100°C and under a pressure of 2-3 atmospheres, undergoes hydrolysis. This process breaks the glycosidic linkages in starch, resulting in the production of glucose. This statement is accurate as starch is a polysaccharide composed of glucose units and can be broken down into glucose under these conditions.
The correct information based on the statements is:
Statement I is false, as D-glucose pentaacetate does not react with 2,4-dinitrophenylhydrazine due to the absence of a free aldehyde group.
Statement II is true, as the described method effectively converts starch into glucose.
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