Attacking reagent on benzene in the above reaction is

Options

A. An electrophile i.e. `Fe^-Cl_2`
B. An electrophile i.e. `Cl^+`
C. A nucleophile i.e. `Cl^-`
D. A nucleophile i.e. `FeCl_4^(-)`

Answer

To determine the attacking reagent on benzene in the given reaction, we need to analyze the process of electrophilic aromatic substitution, specifically chlorination of benzene.

### Step-by-Step Solution:

1. **Identify the Reaction**: The question implies a chlorination reaction involving benzene. In this type of reaction, benzene reacts with chlorine (Cl2) in the presence of a catalyst.

2. **Catalyst Role**: The catalyst mentioned in the reaction is FeCl3 (iron(III) chloride). This catalyst plays a crucial role in generating the electrophile from the chlorine molecule.

3. **Formation of Electrophile**: In the presence of FeCl3, the Cl2 molecule undergoes a reaction where one of the chlorine atoms is released as a positively charged electrophile (Cl+). The reaction can be summarized as:
\[ \text{Cl}_2 + \text{FeCl}_3 \rightarrow \text{FeCl}_4^- + \text{Cl}^+ \]
Here, Cl+ is the electrophile that will attack the benzene ring.

4. **Electrophilic Attack**: The Cl+ ion then attacks the benzene ring, resulting in the formation of a sigma complex (also known as the arenium ion or V-land complex). This intermediate is a non-aromatic structure that temporarily forms during the reaction.

5. **Restoration of Aromaticity**: After the formation of the sigma complex, a proton (H+) is removed from the carbon that was attacked, restoring the aromaticity of the benzene ring and resulting in the final product, chlorobenzene.

6. **Conclusion**: The attacking reagent on benzene in this chlorination reaction is the electrophile Cl+.

### Final Answer:
The attacking reagent on benzene in the above reaction is Cl+ (chloronium ion).

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