Cholorobenzene is formed by reaction of chlorine with benzene in the presence of `AlCl_(3)`. Which of the following species attacks the benzene ring in this reaction?

Options

A. `Cl^(-)`
B. `Cl^(+)`
C. `AlCl_3`
D. `[AlCl_4]^(-)`

Explanation

To determine which species attacks the benzene ring in the formation of chlorobenzene from chlorine and benzene in the presence of AlCl₃, we can follow these steps:

### Step 1: Identify the Reactants
The reactants in this reaction are benzene (C₆H₆) and chlorine (Cl₂), with aluminum chloride (AlCl₃) acting as a catalyst.

### Step 2: Role of AlCl₃
AlCl₃ is a Lewis acid, which means it can accept electron pairs. In this reaction, it interacts with chlorine (Cl₂) to activate it.

### Step 3: Formation of the Electrophile
When AlCl₃ reacts with Cl₂, it forms a complex. The reaction can be represented as:
\[ \text{Cl}_2 + \text{AlCl}_3 \rightarrow \text{AlCl}_4^- + \text{Cl}^+ \]
Here, the chlorine molecule (Cl₂) is polarized, leading to the formation of a chloronium ion (Cl⁺), which is positively charged and acts as an electrophile.

### Step 4: Electrophilic Attack on Benzene
The benzene ring is electron-rich due to its delocalized π electrons. The positively charged chloronium ion (Cl⁺) is attracted to the electron-rich benzene ring. This results in the electrophilic substitution reaction where Cl⁺ attacks the benzene ring.

### Step 5: Formation of Chlorobenzene
The attack of Cl⁺ on the benzene ring leads to the formation of chlorobenzene (C₆H₅Cl) and the regeneration of AlCl₃:
\[ \text{C}_6\text{H}_6 + \text{Cl}^+ \rightarrow \text{C}_6\text{H}_5\text{Cl} + \text{H}^+ \]

### Conclusion
The species that attacks the benzene ring in this reaction is the chloronium ion (Cl⁺).

### Final Answer
The correct answer is Cl⁺ (the chloronium ion).

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