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°C and 2-3 atmosphere pressure, produces glucose.
In the light of the above statements, choose the correct answer from the options given below:
Statement I: D-glucose pentaacetate reacts with 2,4-dinitrophenylhydrazine.
Statement II: Starch, on heating with concentrated sulfuric acid at 100°C and 2-3 atmosphere pressure, produces glucose.
In the light of the above statements, choose the correct answer from the options given below:
Show Hint
- Both Statement I and Statement II are true
- Statement I is true but Statement II is false
- Statement I is false but Statement II is true
- Both Statement I and Statement II are false
The Correct Option is C
Solution and Explanation
Statement I:
D-glucose pentaacetate reacts with 2,4-dinitrophenylhydrazine.
D-glucose pentaacetate is a derivative of glucose in which all the hydroxyl (–OH) groups are esterified. As a result, there is no free carbonyl group (aldehyde or ketone) available for reaction.
2,4-Dinitrophenylhydrazine (DNPH) specifically reacts with aldehydes and ketones through a nucleophilic addition to the carbonyl group, forming 2,4-dinitrophenylhydrazones.
Since D-glucose pentaacetate lacks a free carbonyl group, it **does not** react with 2,4-dinitrophenylhydrazine.
Therefore, Statement I is false.
Statement II:
Starch, on heating with concentrated sulfuric acid at 100°C and under 2–3 atmosphere pressure, produces glucose.
Starch is a polysaccharide composed of multiple glucose units linked by glycosidic bonds.
Under acidic conditions and upon heating under pressure, starch undergoes **acid-catalyzed hydrolysis**, breaking the glycosidic linkages and ultimately yielding glucose molecules.
Therefore, Statement II is true.
Conclusion:
Statement I is false, and Statement II is true.
Final Answer:
The final answer is $ \text{Statement I is false but Statement II is true} $.
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