During mutarotation of `beta`-D-glucose in aqueous solution angle of optical rotation

Options

A. Remains constant value of + `111^(@)`
B. remains constant value of + `19.2^(@)`
C. changes from an angle of `112^(@)` to a constant value of `+52.5^(@)`
D. changes from an angle of `19.2^(@)` to a constant value of `+52.5^(@)`

Answer

To solve the question regarding the angle of optical rotation during the mutarotation of β-D-glucose in aqueous solution, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Mutarotation**:
- Mutarotation is the change in optical rotation that occurs when an α-anomer and a β-anomer of a sugar interconvert in solution. This process involves the equilibrium between the two forms.

2. **Identify the Initial Optical Rotation**:
- When 100% pure β-D-glucose is dissolved in water, it has an initial specific rotation. According to the information provided, the specific rotation of β-D-glucose is approximately +18.7°.

3. **Observe the Change Over Time**:
- As time progresses, the specific rotation of β-D-glucose changes due to the mutarotation process. It will eventually reach a stable value.

4. **Determine the Final Optical Rotation**:
- The stable value of specific rotation for D-glucose (after mutarotation) is +52.5°. This is the equilibrium point where the mixture of α and β forms stabilizes.

5. **Conclusion**:
- Therefore, during the mutarotation of β-D-glucose in aqueous solution, the angle of optical rotation changes from +18.7° to +52.5° as it reaches equilibrium.

### Final Answer:
The angle of optical rotation during the mutarotation of β-D-glucose in aqueous solution changes from +18.7° to +52.5°.