-R effect in benzene causes anti-aromaticity?

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The discussion centers on the -R effect of substituents like NO2 in benzene, specifically in nitrobenzene. The introduction of the -R effect leads to the formation of a double bond between nitrogen and carbon, resulting in a charge distribution that affects the π electron count. The key issue raised is the presence of four π electrons in the canonical forms, which suggests anti-aromaticity, contradicting the stability typically associated with resonance. The participants seek clarification on the apparent contradiction between resonance stability and anti-aromatic characteristics.

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Consider any -R effect showing group like NO2 in place of anyone of the hydrogen of the benzene ring, here we get nitrobenzene.

We know that after showing -R effect a double bond will be formed between N and C and one of the π bond will no longer be present in the ring and it's place will be taken by + charge on ortho and para position which will be in conjugation with the remaining two π bonds in the ring as can be seen from the diagram below.

245595


However the problem is that, in the canonical forms after resonance there will be 4 π electrons in a planar conjugated ring, which by definition is anti aromatic. But this should not be true because we know that resonance increases stability but anti aromatic hydrocarbons are unstable.

Can anyone give an explanation for the same.
 
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None of the canonical forms has a ring of 4 pi electrons. They have six pi electrons in a non-cyclic conjugated system (including the C=N bond).
 

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