Asked in PMC Practice Test 2Moderate

How do meta directing groups affect the electrophilic substitution of benzene ring?

Correct answer: D. Both Options B and C are correct

  • A. Increase electron density at the ortho and para positions
  • B. Decrease electron density at the ortho and para positions
  • C. Make benzene less reactive
  • D. Both Options B and C are correct

Explanation

The meta groups deactivate the ring, by the inductive effect, in the presence of an electronegative atom, that withdraws the electrons away from the ring. As the electron is withdrawn from the ring, by the meta group, it leaves the carbons, at the ortho and para positions, with a positive charge, which is unfavorable for the electrophile, so the electrophile attacks the carbon at the meta positions. Since the conditions are unfavourable for an electrophile to bind, we can assume benzene to have undergone a loss of reactivity.

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About Benzene and Aromatic Compounds

Benzene has a planar ring of delocalised π electrons, giving aromatic stability and equal carbon-carbon bond lengths. The topic covers resonance, electrophilic substitution reactions such as nitration, halogenation, sulphonation and Friedel-Crafts reactions, along with substituent effects and the distinction between substitution in benzene and addition in ordinary alkenes.

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