Asked in ETEA MDCAT 2009 2009Moderate

Which of the following species deactivate the benzene ring when attached to benzene ring?

Correct answer: B. SO3H

  • A. C2H5
  • B. SO3H
  • C. NH2
  • D. CH3

Explanation

order of activating group (NH2, NHR, NHCOCH3, OCH3,CH3,C2H5(and deactivating group (NO2, CN, CHO, COR, COOH, COOR, SO3H)to increase and decrease reactivity of electrophilic substitution. Out of the given options, the following species deactivate the benzene ring when attached to the benzene ring: SO3H (sulfonic acid group) This is called deactivating groups because they decrease the electron density of the benzene ring through resonance and/or inductive effects. This makes the benzene ring less reactive towards electrophilic substitution reactions.

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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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