Question

The most reactive towards electrophilic reagent is

• A. a
• B. b
• C. c
• D. d

Hint:

Activating groups in EAS are ortho-para directors and increase the rate of reaction compared to benzene.

Answer 1

The Correct Option is C

To determine which compound is most reactive towards an electrophilic reagent, we need to consider the nature of substituents on the benzene ring and their effect on the rate of electrophilic substitution reactions.

Electrophilic aromatic substitution reactions are facilitated by electron-donating groups (EDGs), which increase the electron density on the benzene ring, making it more reactive towards electrophiles. Conversely, electron-withdrawing groups (EWGs) reduce electron density, making the benzene ring less reactive.

Let's analyze the substituents in each option:

• (a) CH₃NHCOCH₃: The acetamido group (NHCOCH₃) is an electron-withdrawing group due to the carbonyl group (C=O). It withdraws electron density from the benzene ring, making it less reactive.
• (b) CH₃CH₂OH: The ethyl group (CH₃CH₂) and the hydroxyl group (OH) can donate electrons through hyperconjugation and resonance. However, the overall effect is not as strong as other pure EDGs.
• (c) CH₃OH: The hydroxyl group (OH) is a strong electron-donating group due to its ability to donate electrons through resonance. It significantly increases the reactivity of the benzene ring towards electrophiles.
• (d) CH₃OCH₃: The methoxy group (OCH₃) is also an electron-donating group. However, its effect is slightly reduced compared to the hydroxyl group because of steric hindrance and less resonance donation.

Based on the above analysis, option (c) with the hydroxyl group (OH) is the most reactive towards electrophilic reagents due to its strong electron-donating character via resonance.

Therefore, the correct answer is option (c): CH₃OH.