Depto. Química Orgánica

META DIRECTORS
SEAr

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15/07/2017
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The meta-directors are all strong deactivators and make the second SEAr very difficult. They hamper it because they drastically reduce the electron density of the ring they are attached to.
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The resonance forms of nitrobenzene and benzoic acid indicate that the ring must be very electron defficient, mainly at the ortho and para positions:
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IMPORTANT: A meta director deactivates ALL ring positions but specially the ortho and para ones which are those with the lowest electron density. That's why they direct to meta the by-all-means difficult second SEAr.
  
Therefore, a strong deactivator directs but NOT favors the SEAr:

 Strong deactivators heavily hamper the SEAr but once it is carried out, they direct it to the least disfavored meta position.

Please, avoid plainly saying that a deactivator favors meta SEAr.
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