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

To determine which of the given options is an electron-donating group, we need to understand the characteristics of electron-donating groups. These groups are typically characterized by the presence of lone pairs or the ability to release electrons through resonance or inductive effects. Let's analyze the options:

1. NO₂: The nitro group (-NO₂) is a strong electron-withdrawing group due to its ability to draw electrons towards itself via resonance and inductive effects. It does not donate electrons.
2. -CH₃: The methyl group is considered an electron-donating group because it can donate electrons through hyperconjugation and a weak inductive effect. This makes it an electron-releasing group.
3. -COOH₄: The carboxylic acid group (-COOH) is an electron-withdrawing group. Through resonance and inductive effects, it withdraws electrons rather than donating them.
4. -CN: The cyano group (-CN) is a strong electron-withdrawing group due to its ability to pull electrons towards the nitrogen atom, thus not releasing electrons.
5. -OC₆H₅: The phenoxy group (-OC₆H₅) acts as an electron-donating group when attached to an aromatic system through resonance. However, when considering simple carbon chains or non-aromatic systems, it behaves as an electron-withdrawing due to its electronegativity.

Given the characteristics above, -CH₃ is the correct option as it is an electron-donating group. It donates electrons through hyperconjugation when attached to a carbon chain or an aromatic ring.

Thus, the correct answer is:

-CH₃