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In high school books, Huckel's rule is used for determining aromaticity. We were taught this example

enter image description here

Huckel's rule is limited to monocyclic systems. We were taught to find aromaticity by -

  1. looking for a closed loop. The two loops that were pointed out have been drawn (in pink) in the diagram above.
  2. Applying Huckel's rule to it i.e counting the number of $\pi$ electrons and then applying the 4n+2 formula for aromatic compounds and 4n for anti.

No explanation was provided as to why this concept works on the grounds of 'this is out of syllabus'.

I have multiple questions regarding this 'closed loop' concept

  1. What is it really called?
  2. How does this loop methodology work?
  3. What would happen if the inner loop was aromatic and outer anti aromatic?
    (the example has both loops anti)
Gaurang Tandon
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Avyansh Katiyar
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    Well, you put charges backwards... – Mithoron Feb 23 '18 at 16:17
  • https://chemistry.stackexchange.com/questions/78732/is-7%d1%81irculene-aromatic-or-anti-aromatic - pretty much same thing. – Mithoron Feb 23 '18 at 16:18
  • related https://chemistry.stackexchange.com/questions/37641/is-buckminsterfullerene-aromatic https://chemistry.stackexchange.com/questions/51484/does-aromaticity-require-a-co-planar-pi-system – Mithoron Feb 23 '18 at 16:22
  • @avatar if you want to separate charges to make the inner and outer rings look aromatic, the negative charge should be on the inner ring. – Oscar Lanzi Feb 24 '18 at 14:31
  • @Oscar the rings are anti aromatic – Avyansh Katiyar Feb 24 '18 at 14:33
  • I see , the title is aromaticity that's Mithoron said that the charges are backwards – Avyansh Katiyar Feb 24 '18 at 14:34
  • @AvyanshKatiyar The rule you stated is not very clear. Does all "loops" being aromatic or antiaromatic make the entire molecule the same? It would be great if you could provide some reference! – DatBoi Mar 04 '22 at 14:46

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