Molecules with an extended π system well described by resonance hybrid

  • #1
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Homework Statement:: [...] Molecules with an extended π system such as linear polyenes and polyaromatic compounds are well described by resonance hybrids as well as by delocalized orbitals in molecular orbital theory.
Relevant Equations:: N/A

This is not a Homework question. I was reading Resonance (chemistry) from Wikipedia. I am not able to understand this sentence, "Molecules with an extended π system such as linear polyenes and polyaromatic compounds are well described by resonance hybrids as well as by delocalized orbitals in molecular orbital theory "

What is an extended π system? Given examples of linear polyenes and polyaromatic compounds of extended π system, when I searched polyaromatic, I found bee honeycomb images.
Hexabenzocoronene.svg.png


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Answers and Replies

  • #2
Borek
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You see a honeycomb, I see a system where each individual ring - thanks to the resonance - has a π system. They do combine meaning the system is extended.

For some rings it is immediately obvious, for some it requires spotting that - while the double bond is drawn as if it was on the other side - it is technically shared by two rings, for some it requires drawing a resonance structure. But it is all there.
 

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