Question

Decreasing order of reactivity towards electrophilic substitution for the following compounds is:

• A. C > B > A > D > E
• B. E > D > A > B > C
• C. A > D > E > B > C
• D. D > A > E > C > B

Hint:

Remember: "Donors activate, Withdrawers deactivate." The more easily a group can push electrons into the ring, the more "tasty" that ring becomes for an electron-seeking electrophile!

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
The reactivity of a benzene ring towards electrophilic substitution depends on the nature of the substituent attached. Electron-donating groups (EDGs) activate the ring, while electron-withdrawing groups (EWGs) deactivate it.

Step 2: Detailed Explanation:
- (E) \( -N(CH_3)_2 \): Strong EDG due to resonance (+R effect of Nitrogen). Highly activating. - (D) \( -OCH_3 \): Strong EDG due to resonance (+R effect of Oxygen), but less so than Nitrogen. - (A) \( -CH_3 \): Weak EDG via inductive (+I) effect and hyperconjugation. - (B) Benzene: The standard reference point. - (C) \( -CF_3 \): Strong EWG due to the high electronegativity of three fluorine atoms (-I effect). Highly deactivating.

Step 3: Final Answer
The decreasing order of reactivity (most to least reactive) is E > D > A > B > C.