Which one is most reactive towards `S_(N^(1))` reaction?

Options

A. `C_(6)H_(5)CH (C_(6)H_(5))Br `
B. ` C_(6)H_(5)CH (CH_(3))Br `
C. `C_(6)H_(5)C(CH_(3)) (C_(6)H_(5)) Br `
D. `C_(6)H_(5)CH_(2)Br `

Answer

To determine which compound is most reactive towards an SN1 reaction, we need to analyze the stability of the carbocations formed during the reaction. The stability of a carbocation is influenced by factors such as inductive effects and resonance.

### Step-by-Step Solution:

1. **Understanding SN1 Reaction**:
- SN1 (Substitution Nucleophilic Unimolecular) reactions involve the formation of a carbocation intermediate. The rate of the reaction depends on the stability of this carbocation.

2. **Identify the Compounds**:
- We need to evaluate the given compounds (not specified in the question) to determine which one forms the most stable carbocation.

3. **Carbocation Stability**:
- Carbocation stability increases in the following order:
- Methyl < Primary < Secondary < Tertiary
- Additionally, resonance and inductive effects can further stabilize carbocations.

4. **Analyzing the Given Options**:
- **Option 1**: If it forms a primary carbocation, it will be less stable.
- **Option 2**: If it forms a secondary carbocation, it will be more stable than a primary one.
- **Option 3**: If it has two benzene rings and an alkyl group (like CH3), it will benefit from resonance stabilization and inductive effects, making it highly stable.
- **Option 4**: If it forms a tertiary carbocation, it will be stable, but not as much as the one with resonance from benzene rings.

5. **Conclusion**:
- Based on the analysis, the compound in **Option 3**, which has two benzene rings and an alkyl group, will be the most stable due to resonance and inductive effects. Therefore, it will be the most reactive towards an SN1 reaction.

### Final Answer:
The most reactive compound towards an SN1 reaction is **Option 3**.