Which of the following carbocations is most stable ?

Options

A.
B.
C.
D.

Explanation

To determine which of the given carbocations is the most stable, we need to analyze the stability based on the following factors: inductive effect, hyperconjugation, and resonance. However, in this case, resonance does not apply, so we will focus on inductive effects and hyperconjugation.

### Step-by-Step Solution:

1. **Identify the Carbocations**:
- Carbocation A: CH3CH2CH2C^+CH3 (2° carbocation)
- Carbocation B: CH3CH2C^+CH2CH3 (2° carbocation)
- Carbocation C: Neopentyl carbocation (1° carbocation)
- Carbocation D: CH3C^+CH3 (2° carbocation)

2. **Determine the Degree of Carbocation**:
- Carbocation A: Secondary (2°)
- Carbocation B: Secondary (2°)
- Carbocation C: Primary (1°)
- Carbocation D: Secondary (2°)

3. **Assess Hyperconjugation**:
- Hyperconjugation involves the interaction of the σ-bonds (C-H or C-C) with the empty p-orbital of the carbocation.
- Count the number of alpha hydrogens for each carbocation:
- Carbocation A: 5 alpha hydrogens → 6 hyperconjugating structures
- Carbocation B: 4 alpha hydrogens → 5 hyperconjugating structures
- Carbocation C: 0 alpha hydrogens → 1 hyperconjugating structure (least stable)
- Carbocation D: 4 alpha hydrogens → 5 hyperconjugating structures

4. **Stability Order Based on Hyperconjugation**:
- Carbocation A has the highest number of hyperconjugating structures (6).
- Carbocation B and D have 5 hyperconjugating structures each.
- Carbocation C has the least stability due to only 1 hyperconjugating structure.

5. **Conclusion**:
- Based on the analysis, Carbocation A (CH3CH2CH2C^+CH3) is the most stable carbocation due to having the maximum number of hyperconjugating structures.

### Final Answer:
**Carbocation A (CH3CH2CH2C^+CH3) is the most stable.**

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