A carbonyl compound P, which gives positive iodoform test, undergoes reaction with MeMgBr followed by dehydration to give an olefin Q. Ozonolysis of Q leads to a dicarbonyl compound R, which undergoes intramolecular aldol reaction to give predominantly S.
The structure of the carbonyl compound P is
(A)(see structure)
(B)(see structure)✓ Correct
(C)(see structure)
(D)(see structure)
Answer: (B)
Solution
The carbonyl compound P gives a positive iodoform test, which indicates the presence of a CH3CO− group (methyl ketone).
Looking at the structures:
Option (A) has a CH3CO− group conjugated with a benzene ring
Option (B) has a CH3CO− group with an additional methyl on the double bond
Options (C) and (D) have different structures
Based on the subsequent reactions (Grignard addition, dehydration, ozonolysis, and intramolecular aldol), the correct structure is (B).
JEE Advanced · 2009 · 12 Apr 2009 · Paper 1 · Single correct option
