Question

Which of the following undergo nitration at the fastest rate?

• A. \( \mathrm{C_6H_5NO_2} \)
• B. \( \mathrm{C_6H_5CH_3} \)
• C. \( \mathrm{C_6H_5COOH} \)
• D. \( \mathrm{C_6H_5Br} \)

Hint:

Alkyl groups activate the benzene ring toward electrophilic substitution, while groups like \(NO_2\) and \(COOH\) strongly deactivate it.

Answer 1

The Correct Option is B

Concept:

Nitration of benzene derivatives is an electrophilic aromatic substitution reaction.
The rate of nitration depends on the activating or deactivating nature of the substituent already present on the benzene ring.
Electron-donating groups activate the ring and increase the reaction rate.
Electron-withdrawing groups deactivate the ring and decrease the reaction rate.
Step 1: Analyze the nature of substituents.

Step 2: Identify the most activated ring. The methyl group (\(CH_3\)) donates electron density to the benzene ring through the \(+I\) effect and hyperconjugation, increasing the electron density on the ring. \[ \therefore\ \mathrm{C_6H_5CH_3} \text{ undergoes nitration fastest.} \]