Which is most stable radical ?

Options

A. `CH_(3)`
B. `CH_(2) = CH - CH_(2)`
C. `CH_(3) - CH_(2)`
D.

Answer

To determine which is the most stable radical among the given options, we will analyze the stability of free radicals based on resonance and other factors.

### Step-by-Step Solution:

1. **Understanding Free Radicals**: Free radicals are species that contain an unpaired electron. Their stability can be influenced by the presence of resonance, hyperconjugation, and the nature of the substituents attached to the radical center.

2. **Analyzing CH3 Free Radical**:
- The methyl radical (CH3•) has no resonance stabilization because there are no π bonds or adjacent atoms that can delocalize the unpaired electron.
- Therefore, the CH3 radical is relatively unstable.

3. **Considering Other Radicals**:
- Let's consider a radical such as the allyl radical (C3H5•), which can be represented as CH2=CH-CH2•.
- In this case, the radical can be stabilized by resonance. The unpaired electron can be delocalized over the π system, allowing for resonance structures where the radical is shared between different atoms.

4. **Resonance Stabilization**:
- The presence of resonance means that the radical is not localized on a single atom, which generally increases stability.
- For example, in the allyl radical, we can draw two resonance structures, which indicates that the radical character is spread out over the molecule.

5. **Conclusion**:
- Based on the analysis, the radical with resonance stabilization (such as the allyl radical) is more stable than the methyl radical.
- Therefore, the most stable radical among the options provided is the one that can participate in resonance.

### Final Answer:
The most stable radical is the one that can undergo resonance stabilization, such as the allyl radical (C3H5•).

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