Question

Which of the following is an electron donating group?

• A. NO$_2$
• B. -CH$_3$
• C. -COOH$_4$
• D. -CN
• E. -OC$_6$H$_5$

Hint:

Alkyl groups are activating groups in electrophilic aromatic substitution due to their electron-donating nature.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Electron donating groups (EDGs) increase the electron density in a molecule (like a benzene ring) via inductive ($+I$) or resonance ($+R$) effects.
Step 2: Key Formula or Approach:
Identify groups with positive inductive effects (like alkyls) or lone pairs for resonance donation.
Step 3: Detailed Explanation:
(A) $\text{NO}_2$, (C) $\text{COOH}$, and (D) $\text{CN}$ are all electron-withdrawing groups (EWGs) because they have electronegative atoms or multiple bonds that pull density away.
(B) $\text{-CH}_3$ is an alkyl group. Alkyl groups donate electron density through the $+I$ effect and hyperconjugation.
(E) $\text{-OC}_6\text{H}_5$ is a phenoxy group which is complex but alkyls are the most standard EDGs in such lists.
Step 4: Final Answer:
The electron donating group is -CH$_3$.