" P " is an optically active compound with molecular formula C6H12O. When " P " is treated with 2,4-dinitrophenylhydrazine, it gives a positive test. However, in presence of Tollens reagent, "P" gives a negative test. Predict the structure of "P".
(A)(see structure)
(B)(see structure)✓ Correct
(C)(see structure)
(D)(see structure)
Answer: (B)
Solution
The compound reacts with 2,4-dinitrophenylhydrazine, so it contains a carbonyl group, yet it fails Tollens' test, so that carbonyl belongs to a ketone, not an aldehyde. Being optically active, it must also hold a carbon bearing four different groups. Of the ketones of formula C6H12O, the one in which the carbon next to the carbonyl carries a methyl, an ethyl, a hydrogen and the acetyl group is a stereocentre and meets every requirement. The structure consistent with all the tests is CH3COCH(CH3)CH2CH3, 3-methylpentan-2-one.
JEE Main · 2025 · 07 Apr 2025 · Shift 2 · Single correct option
