Which of the following species is most stable ?

Options

A. `CH_2 = dot CH`
B. `Ph dot C H_2`
C. `Me_3 dot C`
D. `Me_2 dot C H`

Explanation

To determine which of the given free radical species is the most stable, we need to analyze the stability based on resonance and inductive effects. Here’s a step-by-step breakdown of the solution:

### Step 1: Identify the Free Radicals
We have four different free radical species to compare. Let's denote them as A, B, C, and D.

### Step 2: Analyze Resonance
- **Free Radical A**: This species does not have any resonance stabilization because there are no π-bonds or other electron-withdrawing/donating groups that can delocalize the free radical.
- **Free Radical B**: This species has a phenyl group attached to it. The phenyl group can stabilize the free radical through resonance. The free radical can delocalize its unpaired electron into the aromatic system, which significantly increases its stability.
- **Free Radical C**: This species has a tertiary carbon (Me3) attached to it. The three methyl groups can provide +I (inductive) effect, but there is no resonance stabilization.
- **Free Radical D**: This species has a secondary carbon (Me2) attached to it. It has two methyl groups providing +I effect, but again, there is no resonance stabilization.

### Step 3: Compare Inductive Effects
- **Free Radical A**: No inductive effect.
- **Free Radical B**: The phenyl group provides resonance stabilization, which is more significant than inductive effects.
- **Free Radical C**: The three methyl groups provide a strong +I effect, but no resonance.
- **Free Radical D**: The two methyl groups provide a moderate +I effect, but no resonance.

### Step 4: Determine Overall Stability
- **Resonance is more powerful than inductive effects**. Therefore, even though Free Radical C has a strong +I effect, Free Radical B is more stable due to resonance stabilization.
- Free Radical A is the least stable due to the absence of both resonance and inductive effects.

### Conclusion
The most stable free radical among the given options is **Free Radical B** due to the resonance stabilization provided by the phenyl group.

### Final Answer
**Option B** is the most stable species.

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