Benzene can be converted to isopropyl benzene (Cumene) by the following reagent.

Options

A. `CH_(3) CH_(2) CH_(2)` Cl + Anhy. `AlCl_(3)`
B. `CH_(3)–CH = CH_(2)` + Anhy.` AlCl_(3)`
C. Both of the above
D. none of these

Answer

To convert benzene to isopropyl benzene (cumene), we can follow these steps:

### Step 1: Identify the Reaction
We need to perform an electrophilic aromatic substitution reaction. The reagent we will use is an alkyl halide in the presence of a Lewis acid catalyst, such as AlCl3.

### Step 2: Structure of Cumene
The structure of cumene is as follows:
- It has a benzene ring (C6H5) attached to a propyl group (C3H7), specifically isopropyl (C3H7) which is (CH(CH3)2).

### Step 3: Choose the Alkyl Halide
For this reaction, we can use 1-bromopropane (CH3CH2CH2Br) as the alkyl halide.

### Step 4: Formation of Carbocation
When 1-bromopropane reacts with AlCl3, the Lewis acid (AlCl3) interacts with the bromine atom, leading to the formation of a carbocation. The reaction can be summarized as:
- CH3CH2CH2Br + AlCl3 → CH3CH2CH2+ + AlCl4−
This produces a primary carbocation (CH3CH2CH2+).

### Step 5: Carbocation Rearrangement
Since primary carbocations are less stable, a hydride shift occurs to form a more stable secondary carbocation:
- CH3CH2CH2+ → CH3CH(CH3)+ (isopropyl carbocation)

### Step 6: Electrophilic Attack on Benzene
The isopropyl carbocation (now a more stable secondary carbocation) acts as an electrophile and attacks the benzene ring:
- C6H5 + CH3CH(CH3)+ → C6H5CH(CH3)2 (cumene)

### Step 7: Regeneration of Aromaticity
After the electrophilic attack, a proton is lost from the benzene ring to restore aromaticity:
- C6H5CH(CH3)2 → Cumene + H+

### Conclusion
Thus, benzene can be converted to isopropyl benzene (cumene) using 1-bromopropane and AlCl3 as the reagents.

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