Which of the following would not given 2 - phenylbutane as the major product in a Friedel - Crafts reaction with benzene?

Options

A. 1 - butene + HF
B. `"2 - butanol "+H_(2)SO_(4)`
C. `"Butanoylchloride "+AlCl_(3)` then `Zn-Hg//HCl`
D. `"Butyl chloride "+ AlCl_(3)`

Answer

To solve the question of which of the following reagents would not give 2-phenylbutane as the major product in a Friedel-Crafts reaction with benzene, we will analyze each of the given reagents step-by-step.

### Step 1: Understand the structure of 2-phenylbutane
2-phenylbutane has the following structure:
- It consists of a butane chain (four carbon atoms) with a phenyl group (C6H5) attached to the second carbon.
- The molecular formula is C10H14.

### Step 2: Analyze the reagents one by one

1. **Reagent 1: 1-Butane + HF**
- 1-butane can undergo protonation in the presence of HF, leading to the formation of a carbocation.
- This carbocation can then react with benzene to form 2-phenylbutane.
- **Conclusion**: This reagent will give 2-phenylbutane.

2. **Reagent 2: 2-Butanol + H2SO4**
- 2-butanol can be protonated by sulfuric acid, leading to the formation of a stable carbocation.
- This carbocation can then react with benzene to yield 2-phenylbutane.
- **Conclusion**: This reagent will also give 2-phenylbutane.

3. **Reagent 3: Butanoyl chloride + AlCl3**
- Butanoyl chloride (an acyl chloride) undergoes Friedel-Crafts acylation in the presence of AlCl3.
- The acyl group (C=O) will attach to the benzene ring, forming an acylated product.
- Upon reduction (Clemensen reduction) with zinc amalgam and HCl, the carbonyl group will be converted to a methylene group (–CH2–).
- The product formed will be 1-phenylbutane, not 2-phenylbutane.
- **Conclusion**: This reagent will NOT give 2-phenylbutane.

4. **Reagent 4: Butyl chloride + AlCl3**
- Butyl chloride can form a carbocation in the presence of AlCl3.
- This carbocation can rearrange to a more stable secondary carbocation and react with benzene to form 2-phenylbutane.
- **Conclusion**: This reagent will give 2-phenylbutane.

### Final Answer
The reagent that would NOT give 2-phenylbutane as the major product in a Friedel-Crafts reaction with benzene is **Butanoyl chloride + AlCl3**.

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