AIIMS2018Chemistry-Carbohydrates

AIIMS 2018 Chemistry Anomeric Effect MCQ Question

Type: MCQ-conceptual-Medium-Class 12

Assertion : Boiling point of α-D-glucose\alpha\text{-D-glucose} is less than β-D-glucose\beta\text{-D-glucose}.

Reason : β-D-glucose\beta\text{-D-glucose} is more stable than α-D-glucose\alpha\text{-D-glucose}.

A

If both assertion and reason are true and reason is the correct explanation of assertion.

B

If both assertion and reason are true but reason is not the correct explanation of assertion.

C

If assertion is true but reason is false.

D

If both assertion and reason are false.

Correct Answer

Option A

Detailed Explanation

β-D-glucose is more stable than α-D-glucose because the hydroxyl group (–OH) on the anomeric carbon in β-D-glucose occupies an equatorial position, minimizing steric strain and torsional strain, while in α-D-glucose, the –OH group is in an axial position, leading to increased steric hindrance. This increased stability of β-D-glucose contributes to its higher boiling and melting points compared to α-D-glucose. Options B and C are incorrect because the stability and physical properties of these anomers can be clearly determined based on their conformations, and option D is irrelevant as it does not pertain to the question.

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