Which of the following is most reactive towards aqueous NaOH?

Options

A. `C_6H_5Cl`
B. `C_6H_5CH_2Cl`
C. `C_6H_5Br`
D. `BrC_6H_4Br`

Explanation

To determine which compound is most reactive towards aqueous NaOH, we need to analyze the reactivity of each compound based on their structure and the mechanism of nucleophilic substitution reactions.

### Step-by-Step Solution:

1. **Identify the Compounds**:
We have four compounds to consider:
- Option 1: C6H5Cl (Chlorobenzene)
- Option 2: C6H5CH2Cl (Benzyl chloride)
- Option 3: C6H5Br (Bromobenzene)
- Option 4: C6H4Br2 (Dibromobenzene)

2. **Understand the Mechanism**:
The reaction with aqueous NaOH involves a nucleophilic substitution reaction where the hydroxide ion (OH⁻) acts as the nucleophile.

3. **Evaluate Reactivity**:
- **Chlorobenzene (C6H5Cl)**: This compound is a haloarene. The presence of the benzene ring stabilizes the carbon-halogen bond due to resonance, making it less reactive towards nucleophilic substitution.

- **Benzyl Chloride (C6H5CH2Cl)**: This compound is an alkyl halide. The carbon-chlorine bond is a single bond, which is easier to break compared to the double bond character present in haloarenes. Therefore, it is more reactive than chlorobenzene.

- **Bromobenzene (C6H5Br)**: Similar to chlorobenzene, bromobenzene also has resonance stabilization, but it is slightly more reactive than chlorobenzene due to the weaker C-Br bond compared to C-Cl. However, it is still less reactive than benzyl chloride.

- **Dibromobenzene (C6H4Br2)**: This compound also exhibits resonance stabilization and has two bromine atoms, which can further stabilize the structure, making it less reactive than benzyl chloride.

4. **Conclusion**:
Based on the analysis, benzyl chloride (C6H5CH2Cl) is the most reactive towards aqueous NaOH due to the absence of resonance stabilization that would hinder the nucleophilic attack.

### Final Answer:
**Benzyl chloride (C6H5CH2Cl) is the most reactive towards aqueous NaOH.**