Given below are two statements: Statement I: Tropolone is an aromatic compound and has 8π electrons. Statement II: π electrons of >C=O group in tropolone is involved in aromaticity. In the light of the above statements, choose the correct answer from the options given below:
(A)Both Statement I and Statement II are true
(B)Statement I is true but Statement II is false✓ Correct
(C)Statement I is false but Statement II is true
(D)Both Statement I and Statement II are false
Answer: (B)
Solution
Tropolone owes its stability to the dipolar resonance form in which the carbonyl oxygen bears the negative charge and the seven-membered ring becomes a tropylium cation. That ring then carries a closed loop of six π electrons and obeys the Hückel rule, so tropolone is aromatic. Counting every π bond in the molecule, the three ring \ce{C=C} bonds and the \ce{C=O} bond together supply eight π electrons, so the compound is aromatic and possesses 8π electrons; this makes Statement I correct. The aromatic sextet, however, comes from the ring carbons, while the π electrons of the \ce{C=O} group shift onto oxygen as a lone pair and take no part in the ring, so Statement II is incorrect. Hence Statement I is true but Statement II is false.Structure of tropoloneResonance structures showing aromatic system
JEE Main · 2023 · 13 Apr 2023 · Shift 2 · Single correct option
