The most stable radical among the following is

Options

A.
B.
C.
D.

Answer

To determine the most stable radical among the given options, we need to analyze the effects of substituents on the stability of the radical. The stability of radicals is influenced by the presence of electron-donating groups (which stabilize the radical) and electron-withdrawing groups (which destabilize the radical).

### Step-by-Step Solution:

1. **Understand Radical Stability**:
- The stability of a radical is directly proportional to the presence of +M (mesomeric) or +I (inductive) groups, which donate electron density to the radical.
- The stability is inversely proportional to the presence of -M or -I groups, which withdraw electron density from the radical.

2. **Analyze Each Option**:
- **Option A**: Contains a nitro group (NO2).
- The nitro group exhibits a -M effect, which withdraws electron density and destabilizes the radical.
- **Conclusion**: This radical is less stable.

- **Option B**: Contains a chlorine atom (Cl).
- Chlorine shows a -I effect, which also withdraws electron density from the radical.
- **Conclusion**: This radical is less stable.

- **Option C**: Contains a cyano group (C≡N).
- The cyano group exhibits a -I effect, which destabilizes the radical.
- **Conclusion**: This radical is less stable.

- **Option D**: Contains a methyl group (CH3).
- The methyl group shows a +I effect, which donates electron density to the radical.
- **Conclusion**: This radical is more stable.

3. **Determine the Most Stable Radical**:
- Based on the analysis, Option D, which contains the methyl group, is the only option that stabilizes the radical due to its +I effect.
- Therefore, the most stable radical among the options is **Option D**.

### Final Answer:
The most stable radical among the following is **Option D**.