Concept:Friedel-Crafts acylation attaches an acyl group (\( \text{R}-\text{C}=\text{O} \)) to a benzene ring using an acyl halide and a Lewis acid catalyst.
Formula:$$ \text{C}_6\text{H}_6 + \text{CH}_3\text{COCl} \xrightarrow{\text{AlCl}_3} \text{C}_6\text{H}_5\text{COCH}_3 + \text{HCl} $$
Solution:- Acetophenone (\( \text{C}_6\text{H}_5\text{COCH}_3 \)) specifically requires an acetyl group (\( \text{CH}_3\text{CO}- \)).
- Reacting benzene with acetyl chloride (\( \text{CH}_3\text{COCl} \)) in the presence of anhydrous \( \text{AlCl}_3 \) generates the highly reactive acylium ion (\( \text{CH}_3\text{C}^+=\text{O} \)), which then attacks the ring to form acetophenone.
Why other options are incorrect:- Acetic acid and ethanoic acid (same compound) are carboxylic acids, which do not undergo Friedel-Crafts acylation directly without being converted to an acyl chloride or anhydride first.
- Ethyl benzene is a hydrocarbon product of Friedel-Crafts alkylation, not an acylating agent.
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