mutarotation

Question

Mutarotation in glucose arises due to:

RankGuru · Accepted Answer

1. **Definition**: Mutarotation is the change in the specific optical rotation of a solution of an optically active compound over time until it reaches equilibrium.
2. **Glucose Anomers**: Glucose exists in two cyclic hemiacetal forms: $\alpha$-D-Glucose ($+112^\circ$) and $\beta$-D-Glucose ($+19^\circ$).
3. **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 $\alpha$ or $\beta$ anomer.
4. **Equilibrium**: Eventually, an equilibrium mixture is formed (approx. $36\% \alpha$, $64\% \beta$, and $<1\%$ open-chain) with a stable rotation of $+52.7^\circ$.
5. **Conclusion**: This **interconversion** between anomers is the cause of mutarotation.

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mutarotation

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