Which of the following is the least stable form of cyclohexane?

Options

A. Boat-form
B. Chair form
C. Skew- boat form
D. Crown form

Answer

To determine which form of cyclohexane is the least stable, we need to analyze the stability of the different conformations of cyclohexane: chair, crown, skew boat, and boat forms.

### Step-by-Step Solution:

1. **Identify the Different Forms of Cyclohexane**:
- The four forms of cyclohexane we are considering are:
- Chair form
- Crown form
- Skew boat form
- Boat form

2. **Establish Stability Order**:
- The stability of these forms can be ranked based on torsional strain and steric repulsion:
- **Chair form**: Most stable due to minimal torsional strain and no steric repulsion.
- **Crown form**: More stable than skew boat but less stable than chair due to some torsional strain.
- **Skew boat form**: Less stable than crown due to increased torsional strain.
- **Boat form**: Least stable due to significant steric repulsion between flagpole hydrogens.

3. **Explain the Stability Factors**:
- **Chair Form**: No torsional strain and no steric repulsion make it the most stable.
- **Crown Form**: Has some torsional strain but is more stable than skew boat.
- **Skew Boat Form**: Increased torsional strain compared to crown form makes it less stable.
- **Boat Form**: The close proximity of flagpole hydrogens leads to significant steric repulsion, making it the least stable form.

4. **Conclusion**:
- Based on the analysis, the least stable form of cyclohexane is the **Boat form**.

### Final Answer:
The least stable form of cyclohexane is the **Boat form**.

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