1. Friedel-Crafts alkylation of benzene

Friedel-Crafts alkylation is a reaction that involves the synthesis of alkylbenzenes from benzene and alkyl halides or alkyl groups. The reaction is catalyzed by a Lewis acid, typically aluminum chloride (AlCl3) or ferric chloride (FeCl3).

The general mechanism for Friedel-Crafts alkylation involves the formation of a carbocation intermediate, which reacts with benzene to form the desired alkylbenzene. The reaction proceeds through electrophilic aromatic substitution.

2. Major product in Friedel-Crafts alkylation of benzene

The major product in a Friedel-Crafts alkylation reaction is determined by the stability of the carbocation intermediate formed during the reaction. In general, more stable carbocations are formed from more substituted alkyl halides or alkyl groups.

3. Options for Friedel-Crafts alkylation of benzene

a) 1-butene with HF:
- 1-butene is an alkene and cannot undergo Friedel-Crafts alkylation directly.
- This reaction will not give 2-phenylbutane as the major product.

b) 2-butanol with H2SO4:
- 2-butanol can be dehydrated to form 2-butene, which can then undergo Friedel-Crafts alkylation.
- This reaction can give 2-phenylbutane as the major product.

c) Butanoyl chloride with AlCl3 then Zn, HCl:
- Butanoyl chloride is an acyl chloride and cannot undergo Friedel-Crafts alkylation directly.
- The reaction conditions with AlCl3 then Zn, HCl suggest a reduction reaction rather than an alkylation.
- This reaction will not give 2-phenylbutane as the major product.

d) Butyl chloride with AlCl3:
- Butyl chloride is an alkyl halide and can undergo Friedel-Crafts alkylation.
- This reaction can give 2-phenylbutane as the major product.

4. Conclusion

The option that would not give 2-phenylbutane as the major product in a Friedel-Crafts alkylation of benzene is option C, which involves the reaction of butanoyl chloride with AlCl3 then Zn, HCl. This reaction conditions suggest a reduction reaction rather than an alkylation.