Which of the following is the most stable carbocation?

Options

A. `CH_(3)overset(+)CH_(2)`
B. `(CH_(3))_(2)overset(+)CH`
C. `(CH_(3))_(3)overset(+)C`
D. `C_(6)H_(5)overset(+)CH_(2)`

Explanation

To determine which of the provided carbocations is the most stable, we need to analyze the stability of each carbocation based on their structure and the principles of carbocation stability.

### Step-by-Step Solution:

1. **Understanding Carbocation Stability**:
- Carbocations are positively charged carbon species. Their stability is influenced by the number of alkyl groups attached to the positively charged carbon and the ability to stabilize the positive charge through resonance or hyperconjugation.
- The general order of carbocation stability is:
- Tertiary (3°) > Secondary (2°) > Primary (1°) > Methyl (C^+) > Vinyl (C^+).

2. **Identify the Carbocations**:
- Let's denote the carbocations as follows:
- Option A: CH₃CH₂⁺ (1° carbocation)
- Option B: CH₃CH⁺CH₃ (2° carbocation)
- Option C: C(CH₃)₃⁺ (3° carbocation)
- Option D: C₆H₅CH₂⁺ (phenyl carbocation, which is a resonance-stabilized carbocation).

3. **Analyzing Each Option**:
- **Option A**: CH₃CH₂⁺ is a primary carbocation and is the least stable due to having only one alkyl group to help stabilize the positive charge.
- **Option B**: CH₃CH⁺CH₃ is a secondary carbocation, which is more stable than a primary carbocation due to having two alkyl groups.
- **Option C**: C(CH₃)₃⁺ is a tertiary carbocation, which is the most stable among the three types of carbocations due to having three alkyl groups that can donate electron density to stabilize the positive charge.
- **Option D**: C₆H₅CH₂⁺ (phenyl carbocation) is also stabilized by resonance. The positive charge can be delocalized over the aromatic ring, making it very stable.

4. **Comparing Stability**:
- Between the tertiary carbocation (Option C) and the phenyl carbocation (Option D), the phenyl carbocation benefits from resonance stabilization, which can often make it more stable than a tertiary carbocation.
- Therefore, the most stable carbocation among the options given is **Option D** (C₆H₅CH₂⁺).

### Conclusion:
The most stable carbocation is **Option D** (C₆H₅CH₂⁺).

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