Question

But-1-yne on reaction with dilute H2​SO4​ in the presence of Hg2+ ions at 333K gives:

• A.

  

• B.

  

• C.

  

• D.

  

Hint:

But-1-yne reacts with HSO and Hg2+ to form butan-2-one via hydration and tautomerism.

Answer 1

The Correct Option is A

The reaction given in the question involves the hydration of but-1-yne using dilute \text{H}_2\text{SO}_4 in the presence of \text{Hg}^{2+} ions at 333K. This is a classic example of the keto-enol tautomerism involved in alkyne hydration, which eventually leads to the formation of a ketone.

1. But-1-yne is an alkyne with the formula \text{CH}_3\text{C}\equiv\text{CH}.
2. The hydration of but-1-yne occurs in an acidic medium provided by dilute \text{H}_2\text{SO}_4 with \text{Hg}^{2+} as a catalyst. This usually leads to the addition of water across the triple bond.
3. Initially, enol is formed as an intermediate. Enol is unstable and usually isomerizes into its corresponding ketone, which is the more stable form.
4. The enol formed from but-1-yne is butan-1-ol. This immediately tautomerizes to butan-2-one (methyl ethyl ketone).

Therefore, the main product formed by the reaction of but-1-yne with dilute \text{H}_2\text{SO}_4 in the presence of \text{Hg}^{2+} ions is butan-2-one.

The correct answer corresponds to the structural formula of butan-2-one as depicted in the given option: