Asked in ETEA MDCAT 2017 2017Moderate

Which group when attached to benzene will increase its reactivity:

Correct answer: A. -NH4+

  • A. -NH4+
  • B. -NH3
  • C. -C≡N
  • D. -COR

Explanation

Activating groups are Atoms or groups that make the benzene molecule more reactive by increasing the ring's electron density.The resonance structures suggest that the amino group increases the electron density only at ortho- and para-positions of the ring, making them more preferred to the electrophilic attack as they make the benzene more negative thus NH4+ can be used as activating group.

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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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