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The compound Ph-C≡C-CH3 is treated with Hg²+ in acidic aqueous solution. Identify the main organic product A.

1. Ph-CO-CH2-CH3
2. Ph-CH2-CO-CH3
3. Ph-C(OH)=CH-CH3
4. Ph-CH(OH)-CH2-CH3

Correct answer: Ph-CO-CH2-CH3

Solution

Mercury(II)-catalyzed hydration of Ph-C≡C-CH3 follows Markovnikov's rule with electronic direction by the phenyl group, placing the hydroxyl on the carbon alpha to Ph. The resulting enol Ph-C(OH)=CHCH3 tautomerizes to the ketone Ph-CO-CH2CH3 (phenyl ethyl ketone).

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