Mutarotation
Mediumchemistry
Mutarotation in glucose arises due to:
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Solution
Incorrect! Answer:
Interconversion of α and β anomers in solution
- Definition: Mutarotation is the change in the specific optical rotation of a solution of an optically active compound over time until it reaches equilibrium.
- Glucose Anomers: Glucose exists in two cyclic hemiacetal forms: α-D-Glucose (+112∘) and β-D-Glucose (+19∘).
- Mechanism: In aqueous solution, the ring opens to form a tiny amount of the open-chain aldehyde form, which then re-closes to form either the α or β anomer.
- Equilibrium: Eventually, an equilibrium mixture is formed (approx. 36%α, 64%β, and <1% open-chain) with a stable rotation of +52.7∘.
- Conclusion: This interconversion between anomers is the cause of mutarotation.
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About This Question
- Subject
- chemistry
- Chapter
- biomolecules
- Topic
- mutarotation
- Difficulty
- Medium
- Year
- 2025
Solution
Correct Answer:
Interconversion of α and β anomers in solution
- Definition: Mutarotation is the change in the specific optical rotation of a solution of an optically active compound over time until it reaches equilibrium.
- Glucose Anomers: Glucose exists in two cyclic hemiacetal forms: α-D-Glucose (+112∘) and β-D-Glucose (+19∘).
- Mechanism: In aqueous solution, the ring opens to form a tiny amount of the open-chain aldehyde form, which then re-closes to form either the α or β anomer.
- Equilibrium: Eventually, an equilibrium mixture is formed (approx. 36%α, 64%β, and <1% open-chain) with a stable rotation of +52.7∘.
- Conclusion: This interconversion between anomers is the cause of mutarotation.
This medium difficulty chemistry question is from the chapter biomolecules, covering the topic of mutarotation. It appeared in the 2025 exam.
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