Question

For the reaction shown, the product formed is:

• A. Acetophenone type structure
• B. Vinyl ketone on benzene
• C. Ethyl substituted ketone
• D. Cyclohexanone fused to benzene

Hint:

HgSO$_4$/H$_2$SO$_4$ on terminal alkyne always gives \textbf{methyl ketone} with Markovnikov rule.

Answer 1

The Correct Option is D

Step 1: The reagent set is \(HgSO$_4$ / dil.\;H$_2$SO$_4$\) in presence of water and heat. This combination is used for oxymercuration–demercuration of terminal alkynes.
Step 2: Terminal alkyne attached to aromatic ring undergoes \[ R–C\equiv CH \;\longrightarrow\; R–CO–CH$_3$ \] via Markovnikov hydration.
Step 3: In the given molecule, the side chain \( \text{C}\equiv\text{CH} \) is attached to benzene adjacent to a carbonyl group. After hydration the triple bond converts into a methyl ketone ring closure.
Step 4: The resulting system behaves as if the alkyne portion forms a six-membered saturated ring with \(C=O\) → cyclohexanone fused to benzene.
Step 5: Match with options → only (D) represents this transformation.