JEE MAIN - Chemistry (2025 - 28th January Morning Shift - No. 3)
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 $100^{\circ} \mathrm{C}$ and $2-3 \mathrm{atmosphere}$ pressure produces glucose.
In the light of the above statements, choose the correct answer from the options given below
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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