Isopropylbenzene can be prepared by :

Options

A. Benzene `+CH_(3)CH = CH_(2) overset(H_(2)SO_(4))(rarr)`
B. Benzene `+CH_(3)-underset(Cl)underset(|)(C)H-CH_(3) overset(AlCl_(3))(rarr)`
C.
D.

Answer

To prepare isopropylbenzene (also known as cumene), we can follow a series of steps that involve the reaction of benzene with an appropriate alkyl halide or alcohol in the presence of a catalyst. Here’s a step-by-step breakdown of the process:

### Step 1: Identify the Components
We need to start with benzene (C6H6) and an isopropyl group (C3H7). The isopropyl group can be introduced via isopropyl chloride (C3H7Cl) or isopropanol (C3H8O).

### Step 2: Choose the Reaction Method
There are several methods to prepare isopropylbenzene:
1. **Friedel-Crafts Alkylation**: This involves the reaction of benzene with isopropyl chloride (or isopropanol) in the presence of a Lewis acid catalyst like AlCl3.
2. **Hydride Shift**: If starting from a secondary alcohol, we can use acid to protonate the alcohol, leading to the formation of a carbocation, which can then rearrange to form a more stable carbocation before reacting with benzene.

### Step 3: Friedel-Crafts Alkylation
1. **React Benzene with Isopropyl Chloride**:
- Combine benzene (C6H6) with isopropyl chloride (C3H7Cl) in the presence of AlCl3.
- The AlCl3 acts as a catalyst and helps generate the isopropyl carbocation (C3H7+).

**Reaction**:
\[ \text{C}_6\text{H}_6 + \text{C}_3\text{H}_7\text{Cl} \xrightarrow{\text{AlCl}_3} \text{C}_6\text{H}_5\text{C}_3\text{H}_7 + \text{HCl} \]

### Step 4: Carbocation Stability
- The isopropyl carbocation is a secondary carbocation, which is more stable than a primary carbocation. Thus, it can effectively react with the benzene ring.

### Step 5: Nucleophilic Attack
- The benzene ring acts as a nucleophile and attacks the isopropyl carbocation, leading to the formation of isopropylbenzene.
- The aromaticity of the benzene is restored by the loss of a proton (H+).

### Step 6: Final Product
- The final product is isopropylbenzene (C6H5C3H7), which is also known as cumene.

### Conclusion
Isopropylbenzene can be prepared through Friedel-Crafts alkylation using benzene and isopropyl chloride in the presence of a Lewis acid catalyst like AlCl3.