Effect of Substituents

Effect of Substituents MDCAT MCQs with answers

8 past paper MCQs on Effect of Substituents, from the Chemistry of Hydrocarbons unit of MDCAT Chemistry. The year each question appeared is shown where known; tap “Show answer” for the correct option and a short solution.

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1.Which of the following is an example of a substituent group which releases electrons to the benzene ring? (MDCAT 2024)

  1. $-\mathrm{CN}$
  2. $-\mathrm{NR_3^+}$
  3. $-\mathrm{NH_2}$
  4. $-\mathrm{NO_2}$
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Correct answer: (c) $-\mathrm{NH_2}$

The lone pair on nitrogen is donated into the ring, which is why $-\mathrm{NH_2}$ activates it.

2.Which of the following is an example of substituent group which release electrons to benzene ring : (UHS MDCAT 2024)

  1. -CN
  2. -NR3+
  3. -NH2
  4. -NO2
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Correct answer: (c) -NH2

The lone pair of the amino group is fed into the ring; nitro and cyano groups pull electrons out.

3.The most readily sulphonated compound is: (NUMS MDCAT 2024)

  1. Benzene
  2. Chlorobenzene
  3. Nitrobenzene
  4. Toluene
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Correct answer: (d) Toluene

The methyl group feeds electrons into the ring and so activates it towards the electrophile.

4.Which of the following undergoes sulfonation the fastest? (PMC MDCAT 2022)

  1. Benzene
  2. Chlorobenzene
  3. Nitrobenzene
  4. Toluene
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Correct answer: (d) Toluene

The methyl group feeds electrons into the ring and so speeds up attack by the electrophile.

5.How do meta directing groups affect the electrophilic substitution of benzene ring? (PMC Practice 2021)

  1. Increase electron density at the ortho and para positions
  2. Decrease electron density at the ortho and para positions
  3. Make benzene less reactive
  4. Both Options B and C are correct
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Correct answer: (d) Both Options B and C are correct

A meta director pulls electrons out of the ring, chiefly from the ortho and para positions, so the ring is deactivated.

6.When CH3 is attached to the benzene ring, it makes the ring a: (PMC MDCAT 2020)

  1. Good electrophile
  2. Good nucleophile
  3. Resonance hybrid
  4. Extraordinary stable
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Correct answer: (b) Good nucleophile

The methyl group feeds electrons into the ring, so the ring becomes richer in electrons and attacks electrophiles.

7.Which derivative of benzene shows maximum reactivity in electrophilic substitution reactions? (UHS MDCAT 2019)

  1. Benzoic acid
  2. Methyl benzene
  3. Benzaldehyde
  4. Nitrobenzene
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Correct answer: (b) Methyl benzene

The methyl group feeds electrons into the ring; the other three groups pull them out.

8.Among the following, which one has an electron withdrawing effect: (UHS MDCAT 2017)

  1. -NH2
  2. -N(CH3)2
  3. -CHO
  4. -I
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Correct answer: (c) -CHO

The carbonyl group pulls electrons out of the ring; the amino and alkyl groups push them in.

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