PhMgBr (Grignard reagent ) cannot be used to prepare the compound ?

Options

A.
B.
C.
D.

Answer

To determine which compound cannot be prepared using the Grignard reagent phenyl magnesium bromide (PhMgBr), we will analyze the four options given in the question.

### Step-by-step Solution:

1. **Identify the Grignard Reagent**:
- The Grignard reagent in question is phenyl magnesium bromide (PhMgBr).

2. **Evaluate Option 1: Benzoic Acid (C6H5COOH)**:
- When PhMgBr reacts with carbon dioxide (CO2), it forms a carboxylate intermediate, which upon hydrolysis yields benzoic acid.
- **Conclusion**: Benzoic acid can be prepared using PhMgBr.

3. **Evaluate Option 2: 2-Phenyl Ethanol (C6H5CH(OH)CH3)**:
- PhMgBr can react with an aldehyde or ketone to form an alcohol. For example, reacting with acetaldehyde (CH3CHO) will yield 2-phenyl ethanol after hydrolysis.
- **Conclusion**: 2-Phenyl ethanol can be prepared using PhMgBr.

4. **Evaluate Option 3: Acetophenone (C6H5COCH3)**:
- PhMgBr can react with acetyl chloride (CH3COCl) to form acetophenone after hydrolysis.
- **Conclusion**: Acetophenone can be prepared using PhMgBr.

5. **Evaluate Option 4: Tertiary Butyl Benzene (C6H5C(CH3)3)**:
- When PhMgBr is reacted with a tertiary alkyl halide, it does not lead to the formation of tertiary butyl benzene. Instead, it would lead to the formation of benzene and other by-products.
- **Conclusion**: Tertiary butyl benzene cannot be prepared using PhMgBr.

### Final Answer:
The compound that cannot be prepared using the Grignard reagent phenyl magnesium bromide (PhMgBr) is **Tertiary Butyl Benzene**.

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