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Basics of Organic Chemistry question

2023 · 13 Apr · Shift 2 · Q10
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Basics of Organic Chemistry question

2023 · 13 Apr · Shift 2 · Q10

JEE MainChemistryBasics of Organic ChemistryMCQ+4 / −1
Given below are two statements : Statement I : Tropolone is an aromatic compound and has 8π8 \pi8π electrons. Statement II : π\piπ electrons of >C=O\gt \mathrm{C}=\mathrm{O}>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:
  1. A
    Statement I is false but Statement II is true
  2. B
    Both Statement I and Statement II are false
  3. C
    Statement I is true but Statement II is false
  4. D
    Both Statement I and Statement II are true
View written solutionFree

Correct answer: B

  1. Understand the structure of tropolone

    Tropolone is a seven-membered ring containing:

    • three \ceC=C\ce{C=C}\ceC=C bonds in the ring, and
    • one carbonyl group \ceC=O\ce{C=O}\ceC=O.

    It also exists as a resonance-stabilized system, and its aromaticity is discussed through delocalization over the ring.

  2. Check Statement I: "Tropolone is an aromatic compound and has 8π8\pi8π electrons."

    • Tropolone is indeed considered aromatic because it has a cyclic, planar, conjugated system with effective delocalization.
    • However, the key point is the number of delocalized π\piπ electrons involved in aromaticity.

    Count the relevant electrons:

    • three \ceC=C\ce{C=C}\ceC=C bonds contribute 6π6\pi6π electrons.
    • the carbonyl π\piπ bond is not counted as an extra independent pair making the ring an 8π8\pi8π system in the simple sense stated.

    Aromatic stabilization in tropolone is associated with a 6π6\pi6π aromatic system, not an 8π8\pi8π aromatic system.

    Therefore, Statement I is false.

  3. Check Statement II: " π\piπ electrons of \ce>C=O\ce{>C=O}\ce>C=O group in tropolone is involved in aromaticity."

    In tropolone, the carbonyl group participates through resonance interaction with the ring. The π\piπ system is conjugated, but the π\piπ electrons of the carbonyl bond themselves are not counted as the aromatic sextet in the way the statement suggests.

    Aromaticity is not described by saying that the carbonyl π\piπ electrons directly contribute as part of an 8π8\pi8π aromatic circuit. Thus this statement is also taken as false in standard exam treatment.

    Therefore, Statement II is false.

  4. Evaluate options

    • A: Statement I false, Statement II true →\rightarrow→ incorrect
    • B: Both Statement I and Statement II are false →\rightarrow→ correct
    • C: Statement I true, Statement II false →\rightarrow→ incorrect
    • D: Both Statement I and Statement II are true →\rightarrow→ incorrect
  5. Final answer

    The correct option is: B\boxed{\text{B}}B​

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