Do compounds like tropolone, furan, and thiophene (which are aromatic) show resonance?
If yes then what are the resonance structures that can be drawn? Also, do all aromatic compounds show resonance?
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1$\begingroup$ I think aromaticity by definition implies resonance $\endgroup$– Binary GeekMar 15, 2015 at 13:39
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1$\begingroup$ Binary is right. A prerequisite for aromaticity is cyclic conjugation. Conjugation in itself allows resonance. Although do not confuse resonance with aromaticity. Resonance is a necessary, but not sufficient condition for aromaticity. $\endgroup$– LexiconMar 15, 2015 at 14:27
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1 Answer
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Resonance structures can be drawn for all aromatic compounds. Tropolone, furan and thiophene are considered to be aromatic compounds because
- we can draw resonance structures
- and they are cyclic compounds with 4n+2 (n=1) pi electrons
Here are the resonance structures we can draw for tropolone, the positive charge can be delocalized to every carbon in the ring.
Just like in benzene, where instead of drawing 2 resonance structures (top of following figure) we usually just draw the one resonance structure shown at the bottom of the figure;
instead of drawing all 8 resonance structures for tropolone, we usually represent them by just drawing the one resonance structure shown at the bottom of the tropolone figure.
and here are the resonance structures for furan
and for thiophene, they are the same as furan, just replace the oxygen with a sulfur atom in the resonance structures.
