Alkyne Hydration
Mediumchemistry
Hydration of 2-butyne (Hg2+, H2SO4) gives major product:
Select the correct option:
Solution
Incorrect! Answer:
Butan-2-one
- Reaction Setup: Alkynes add water in the presence of acid and Hg2+ catalyst (Kucherov Reaction).
- Enol Intermediate: Water adds across the triple bond to form a vinyl alcohol (enol): CH3−C(OH)=CH−CH3.
- Tautomerism: Enols are highly unstable and undergo Keto-Enol tautomerization rapidly. The hydrogen from Oxygen moves to the α-carbon, and the C−O single bond becomes a C=O double bond.
- Final Product: Tautomerization of the but-2-en-2-ol enol yields Butan-2-one (Ethyl methyl ketone).
- Note: Hydration of Ethyne gives Ethanal, but hydration of all higher alkynes gives ketones.
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About This Question
- Subject
- chemistry
- Chapter
- hydrocarbons
- Topic
- alkyne hydration
- Difficulty
- Medium
- Year
- 2025
Solution
Correct Answer:
Butan-2-one
- Reaction Setup: Alkynes add water in the presence of acid and Hg2+ catalyst (Kucherov Reaction).
- Enol Intermediate: Water adds across the triple bond to form a vinyl alcohol (enol): CH3−C(OH)=CH−CH3.
- Tautomerism: Enols are highly unstable and undergo Keto-Enol tautomerization rapidly. The hydrogen from Oxygen moves to the α-carbon, and the C−O single bond becomes a C=O double bond.
- Final Product: Tautomerization of the but-2-en-2-ol enol yields Butan-2-one (Ethyl methyl ketone).
- Note: Hydration of Ethyne gives Ethanal, but hydration of all higher alkynes gives ketones.
This medium difficulty chemistry question is from the chapter hydrocarbons, covering the topic of alkyne hydration. It appeared in the 2025 exam.
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