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Homework Help: Organic Chemistry: Aromaticity

  1. Feb 22, 2015 #1
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    Huckel's Rule: 4n +2 pi electrons

    3. The attempt at a solution

    I'm having problems with the last molecule. I said that the first molecule was indeed aromatic because it has 6 pi electrons and obeys the 4n + 2 rule. The second one is not aromatic because it has 16 pi electrons. But for the last molecule, my reasoning for why it's not aromatic is that although it has 6 pi electrons, the electrons in the p orbitals of the carbons from the carbonyls don't occupy the p-orbitals of the oxygen, the two p-orbitals just overlap. So I don't think the p-orbitals of those carbons count towards aromaticity in the ring because those orbitals overlap with the p-orbitals on the oxygens and not the p-orbitals of the adjacent carbons. I was thinking that those p orbitals don't contribute to resonance stabilization in the ring. There are indeed 6 pi electrons, but i don't think the conjugated pi-orbital system criteria is satisfied. Is my reasoning on the right track? Any help would be appreciated. Thanks!
  2. jcsd
  3. Feb 23, 2015 #2
    The last one is not a planar compound...my text book says it must be a planar compound to be aromatic.
    Last edited by a moderator: Feb 23, 2015
  4. Mar 4, 2015 #3

    Suraj M

    User Avatar
    Gold Member

    Could you please state why the last molecule is not planar? it is true that the compound must be planar to be aromatic!
  5. Mar 4, 2015 #4
    Maybe becoz of the steric interference between NH group and oxon group it might have been diS placed. .(not so sure abt this)
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