Which one is most stable ?

Options

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

Answer

To determine which compound is the most stable among Cyclopropane, Cyclobutane, Cyclopentane, and Cyclohexane, we can analyze their structures and the concept of angle strain. Here’s a step-by-step solution:

### Step 1: Identify the Compounds
We have four cyclic hydrocarbons to consider:
- Cyclopropane
- Cyclobutane
- Cyclopentane
- Cyclohexane

### Step 2: Determine the Bond Angles
Each of these compounds has specific bond angles due to their geometric shapes:
- Cyclopropane: 60°
- Cyclobutane: 90°
- Cyclopentane: 108°
- Cyclohexane: 120°

### Step 3: Understand Hybridization
All carbon atoms in these compounds are sp³ hybridized, which ideally should have bond angles of approximately 109.5°. However, due to the cyclic nature of these compounds, the actual bond angles deviate from this ideal value.

### Step 4: Analyze Angle Strain
Angle strain occurs when the bond angles in a molecule deviate from the ideal angle of 109.5° for sp³ hybridized carbons. The greater the deviation, the more angle strain and, consequently, the less stability the compound has.

- Cyclopropane (60°): Significant angle strain
- Cyclobutane (90°): Moderate angle strain
- Cyclopentane (108°): Slight angle strain
- Cyclohexane (120°): Minimal angle strain

### Step 5: Compare Stability
The stability of these compounds can be compared based on their angle strain:
- Cyclopropane has the highest angle strain and is the least stable.
- Cyclobutane has moderate angle strain and is more stable than cyclopropane.
- Cyclopentane has slight angle strain and is more stable than both cyclopropane and cyclobutane.
- Cyclohexane has minimal angle strain and is the most stable of the four.

### Conclusion
Cyclohexane is the most stable compound among the four due to its minimal angle strain.

### Final Answer
**Cyclohexane is the most stable compound.**

---