Which one of the following Carbocation is most stable :

Options

A.
B.
C.
D. `overset(o+)(CH_(2))-NO_(2)`

Answer

To determine which carbocation is the most stable among the given options, we need to analyze the stability of each carbocation based on its degree and the presence of electron-withdrawing groups. Here’s the step-by-step solution:

### Step 1: Identify the Degree of Each Carbocation
- **Option 1**: 2° carbocation (secondary) with an electron-withdrawing group (EWG).
- **Option 2**: 1° carbocation (primary) with an electron-withdrawing group (EWG).
- **Option 3**: 2° carbocation (secondary) without any electron-withdrawing group.
- **Option 4**: 1° carbocation (primary) with a strong electron-withdrawing group (NO2).

### Step 2: Analyze the Effects of Electron-Withdrawing Groups
- Electron-withdrawing groups destabilize carbocations because they pull electron density away from the positively charged carbon, making it less stable.
- In options 1, 2, and 4, the presence of electron-withdrawing groups will decrease the stability of the carbocations.

### Step 3: Compare the Stability of Each Carbocation
- **Option 1**: The 2° carbocation is destabilized by the EWG, making it less stable than a 2° carbocation without an EWG.
- **Option 2**: The 1° carbocation is less stable than a 2° carbocation, and the presence of an EWG further decreases its stability.
- **Option 3**: The 2° carbocation without any electron-withdrawing groups is more stable than both the 1° and 2° carbocations with EWGs.
- **Option 4**: The 1° carbocation is significantly destabilized by the strong EWG (NO2), making it the least stable.

### Step 4: Conclusion
Based on the analysis, **Option 3** is the most stable carbocation because it is a 2° carbocation without any destabilizing electron-withdrawing groups.

### Final Answer
The most stable carbocation is **Option 3**.

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