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Organic Chemistry: Aromaticity

  1. Feb 22, 2015 #1
    1. The problem statement, all variables and given/known data
    upload_2015-2-22_17-2-24.png

    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

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    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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