Conversion of ethanol to but- 1- yne

Conversion of Ethanol (CH₃CH₂OH) to But-1-yne (CH≡C–CH₂CH₃)

The transformation of ethanol into but-1-yne is a multistep organic synthesis process. It involves substitution, elimination, and coupling reactions. Let’s understand this conversion step by step.

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Step 1: Ethanol → Bromoethane

Ethanol reacts with PBr₃ (or HBr + ZnCl₂) to form bromoethane.

CH₃CH₂OH → (PBr₃) → CH₃CH₂Br

Step 2: Bromoethane → Ethyne

Bromoethane undergoes elimination with alc. KOH to form ethene, which further reacts with Br₂/HBr and then alc. KOH to give ethyne.

CH₃CH₂Br → (alc. KOH) → CH₂=CH₂ → (Br₂/HBr, alc. KOH) → HC≡CH

Step 3: Ethyne → Sodium Acetylide

Ethyne reacts with a strong base like NaNH₂ in liquid ammonia to form sodium acetylide.

HC≡CH → (NaNH₂/liquid NH₃) → HC≡C⁻Na⁺

Step 4: Sodium Acetylide → But-1-yne

Sodium acetylide undergoes alkylation with ethyl bromide to give but-1-yne.

HC≡C⁻Na⁺ + CH₃CH₂Br → CH≡C–CH₂CH₃

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✨ Overall Reaction Pathway

Ethanol → Bromoethane → Ethene → Ethyne → Sodium Acetylide → But-1-yne

Figure: Stepwise Conversion of Ethanol to But-1-yne

🔍 Key Points to Remember:

• Conversion involves both elimination (E2) and substitution reactions.
• Sodamide (NaNH₂) is essential for forming acetylide ion.
• The final step uses ethyl bromide for chain extension.
• This transformation highlights how alcohol can be converted into an alkyne.