Question

The substituent X increases electron density in benzene ring by hyperconjugation effect and substituent Y decreases electron density in benzene by resonance effect. X and Y respectively are

• A. $-CH_3,\ -NO_2$
• B. $-OCH_3,\ -COCH_3$
• C. $-OH,\ -NO_2$
• D. $-CH_3,\ -NHCH_3$

Hint:

\[ -CH_3 \] is activating due to hyperconjugation. \[ -NO_2 \] is strongly deactivating due to the $-R$ effect.

Answer 1

The Correct Option is A

Concept: Hyperconjugation increases electron density in aromatic rings through sigma-electron delocalization. Electron withdrawing groups decrease electron density through negative resonance effect ($-R$ effect).

Step 1: Identify the group showing hyperconjugation.
Alkyl groups such as \[ -CH_3 \] donate electron density to the benzene ring through hyperconjugation. Therefore X must be \[ -CH_3 \]

Step 2: Identify the group showing negative resonance effect.
The nitro group \[ -NO_2 \] withdraws electrons strongly through resonance. Hence it decreases electron density in the benzene ring. Therefore Y must be \[ -NO_2 \]

Step 3: Choose the answer.
\[ \boxed{-CH_3,\ -NO_2} \]