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Identify the final product [D] obtained in the following sequence of reactions. CH₃CHO → (i) LiAlH₄ (ii) H₃O⁺ → [A] → (H₂SO₄, Δ) [B] → (HBr) [C] → (bromobenzene, Na/dry ether) [D]
Acetaldehyde reduces to ethanol [A]. Acidic dehydration of ethanol gives ethene [B]. Addition of HBr gives ethyl bromide [C]. Wurtz-Fittig reaction of ethyl bromide with bromobenzene and sodium in dry ether couples the ethyl group to the benzene ring, yielding ethylbenzene [D]! Option (2) in 15 seconds!
Lithium aluminium hydride reduces acetaldehyde to primary alcohol ethanol:
Heating ethanol with concentrated sulphuric acid at 443 K undergoes intramolecular dehydration to form ethene:
Addition of hydrogen bromide across the symmetrical alkene double bond produces bromoethane:
Reaction of bromoethane and bromobenzene with sodium metal in dry ether produces alkylarene (ethylbenzene) via the Wurtz-Fittig reaction:
Diagnose every choice: Know exactly why the right option works and why distractors fail.
Terminal sodium acetylide is not formed in this reaction pathway.
Accurate: Cross-coupling of bromobenzene and bromoethane yields ethylbenzene.
Biphenyl is the Fittig self-coupling byproduct of bromobenzene, not the primary cross-coupled product.
Butane is the Wurtz self-coupling byproduct of bromoethane.
In the Wurtz-Fittig reaction of bromobenzene and bromoethane, biphenyl and butane form as side products. The intended cross-coupled product of aryl halide + alkyl halide is ethylbenzene.
"A mixture of an alkyl halide and aryl halide gives an alkylarene when treated with sodium in dry ether."
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