The dibromo compound [P] (molecular formula: C9H10Br2) when heated with excess sodamide followed by treatment with dilute HCl gives [Q]. On warming [Q] with mercuric sulphate and dilute sulphuric acid yield [R] which gives positive Iodoform test but negative Tollen's test. The compound [P] is:
(A)(see structure)
(B)(see structure)
(C)(see structure)✓ Correct
(D)(see structure)
Answer: (C)
Solution
The product [R] gives a positive iodoform test but a negative Tollens test, so it is a methyl ketone of the type Ar−CO−CH3 rather than an aldehyde. Such a ketone comes from Markovnikov hydration of a terminal arylalkyne [Q] with mercuric sulphate and dilute sulphuric acid, and that alkyne forms when a geminal dibromide loses two molecules of hydrogen bromide to excess sodamide. The formula C9H10Br2 fits 1,1-dibromo-1-(4-methylphenyl)ethane, which gives 4-methylphenylacetylene and then 4-methylacetophenone, so [P] is the geminal dibromide 4-CH3C6H4−CBr2−CH3.
JEE Main · 2026 · 22 Jan 2026 · Shift 2 · Single correct option
