Which of the following would not given 2 - phenylbutane as the major product in a Friedel - Crafts alkylation 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 determine which of the following would not give 2-phenylbutane as the major product in a Friedel-Crafts alkylation reaction with benzene, we need to analyze the potential reactants and their behavior in the reaction.

### Step-by-Step Solution:

1. **Understanding Friedel-Crafts Alkylation**:
Friedel-Crafts alkylation involves the reaction of an alkyl halide with benzene in the presence of a Lewis acid catalyst (like AlCl3). The alkyl halide generates a carbocation, which then reacts with the benzene ring.

2. **Identifying the Major Product**:
The major product is determined by the stability of the carbocation formed during the reaction. For 2-phenylbutane to be the major product, the carbocation must be a secondary or more stable carbocation that can rearrange to form the desired product.

3. **Analyzing Each Option**:
- **Option 1: 1-Butene with HF**:
- 1-butene can form a secondary carbocation upon reaction with HF. This secondary carbocation can then react with benzene to form 2-phenylbutane.
- **Conclusion**: This option can give 2-phenylbutane.

- **Option 2: 2-Butanol with H2SO4**:
- 2-butanol, when treated with H2SO4, will form a carbocation that can also lead to the formation of 2-phenylbutane.
- **Conclusion**: This option can also give 2-phenylbutane.

- **Option 3: Butanoyl Chloride with AlCl3**:
- Butanoyl chloride will undergo Friedel-Crafts acylation rather than alkylation. It forms an acylium ion, which is a different type of electrophile. The reaction will not yield 2-phenylbutane but rather a phenylbutanoyl compound.
- **Conclusion**: This option will not give 2-phenylbutane.

- **Option 4: 2-Butyl Chloride with AlCl3**:
- 2-butyl chloride can form a stable secondary carbocation that can react with benzene to yield 2-phenylbutane.
- **Conclusion**: This option can give 2-phenylbutane.

4. **Final Answer**:
Based on the analysis, the correct answer is **Option 3: Butanoyl Chloride with AlCl3**, as it does not yield 2-phenylbutane.