Which of the following is the most stable carbocation (carbonium ion) ?

Options

A. `CH_(3)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 the most stable carbocation from the given options, we need to analyze the stability factors that influence carbocation stability: hyperconjugation, inductive effects, and resonance.

### Step-by-Step Solution:

1. **Identify the Carbocations**:
We have four carbocations to analyze:
- (A) CH3-CH2^+
- (B) (CH3)2CH^+
- (C) (CH3)3C^+
- (D) C6H5-CH2^+

2. **Analyze Each Carbocation**:
- **(A) CH3-CH2^+**: This is a primary carbocation. It has one alkyl group (ethyl) which can provide some inductive effect and hyperconjugation from the three hydrogens on the adjacent carbon. However, it is the least stable due to being primary.

- **(B) (CH3)2CH^+**: This is a secondary carbocation. It has two methyl groups that can donate electrons through the inductive effect (+I effect) and has more hyperconjugation (6 alpha hydrogens) compared to (A). This makes it more stable than (A).

- **(C) (CH3)3C^+**: This is a tertiary carbocation. It has three methyl groups contributing to the inductive effect and has the highest hyperconjugation (9 alpha hydrogens). This makes it more stable than both (A) and (B).

- **(D) C6H5-CH2^+**: This is a benzylic carbocation. The positive charge can be stabilized by resonance with the phenyl ring. The resonance effect significantly enhances its stability, making it very stable compared to the other carbocations.

3. **Compare the Stability**:
- (A) is the least stable (primary).
- (B) is more stable than (A) (secondary).
- (C) is more stable than (B) (tertiary).
- (D) is the most stable due to resonance stabilization.

4. **Conclusion**:
The most stable carbocation among the given options is **(D) C6H5-CH2^+** due to resonance stabilization.

### Final Answer:
**(D) C6H5-CH2^+ is the most stable carbocation.**