According to Baeyer's strain theory, which of the following is/are most stable cyclic compounds?

Options

A. Cyclopropane
B. Cyclobutane
C. Cyclopentane
D. Cyclohexane

Answer

To determine which cyclic compound is the most stable according to Baeyer's strain theory, we will analyze the angle strain in each of the given compounds: cyclopropane, cyclobutane, cyclopentane, and cyclohexane.

### Step-by-Step Solution:

1. **Understanding Baeyer's Strain Theory**:
- Baeyer's strain theory states that the stability of cyclic compounds is influenced by angle strain, which is the difference between the desired bond angle (109.5° for sp³ hybridized carbon) and the actual bond angle in the cyclic structure.

2. **Identifying the Desired Bond Angle**:
- For all cycloalkanes (cyclopropane, cyclobutane, cyclopentane, and cyclohexane), the desired bond angle is approximately 109.5°.

3. **Determining Actual Bond Angles**:
- **Cyclopropane**: The structure is triangular, so each bond angle is 60°.
- **Cyclobutane**: The structure is square-like, so the bond angles are approximately 90°.
- **Cyclopentane**: The structure is pentagonal, so the bond angles are approximately 108°.
- **Cyclohexane**: The structure is hexagonal, so the bond angles are approximately 120°.

4. **Calculating Angle Strain**:
- **Cyclopropane**:
- Angle strain = Desired angle - Actual angle = 109.5° - 60° = 49.5°
- **Cyclobutane**:
- Angle strain = 109.5° - 90° = 19.5°
- **Cyclopentane**:
- Angle strain = 109.5° - 108° = 1.5°
- **Cyclohexane**:
- Angle strain = 109.5° - 120° = -10.5° (indicating a favorable strain due to its chair conformation)

5. **Comparing Stability**:
- The greater the angle strain, the less stable the compound. Therefore, we can rank the stability based on the calculated angle strains:
- Cyclopropane: 49.5° (least stable)
- Cyclobutane: 19.5°
- Cyclopentane: 1.5° (most stable among the given options)
- Cyclohexane: -10.5° (very stable due to its chair conformation)

6. **Conclusion**:
- Among the given cyclic compounds, **cyclopentane** is the most stable cyclic compound according to Baeyer's strain theory.

### Final Answer:
**Cyclopentane is the most stable cyclic compound according to Baeyer's strain theory.**

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