See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

## Analysis of Electronic Effects For all three effects (inductive, mesomeric, and hyperconjugation) to operate simultaneously, we need: - A substituent that is **electron-withdrawing by induction** (−I effect) - A substituent that can participate in **resonance** (±M effect) - A substituent with **α-hydrogens** for hyperconjugation ### Examining Option (B): $-COCH_3$ (acetyl group) **Inductive Effect (−I):** The carbonyl carbon is highly electronegative. The $C=O$ bond polarizes electron density away from the benzene ring, creating a −I effect. ✓ **Mesomeric Effect (±M):** The carbonyl group has a lone pair on oxygen that can donate electron density to the aromatic ring through resonance: $$\text{Benzene ring} \leftarrow \text{O lone pair (M⁺ effect)}$$ This creates resonance structures where oxygen stabilizes positive charge on the ring. ✓ **Hyperconjugation:** The methyl group ($-CH_3$) attached to the carbonyl has three α-hydrogens that can undergo hyperconjugation with the π-system through $\sigma \rightarrow \pi^*$ orbital overlap. ✓ ### Why others fail: **(A) $-Cl$:** No hyperconjugation (no α-hydrogens); only −I and mild −M effects. **(C) $-CH_3$:** Shows +I (alkyl groups are electron-donating) and +M effects, but requires the ring to be aromatic with extended conjugation for hyperconjugation with the ring itself—doesn't satisfy the inductive requirement. **(D) Benzene:** No substituent; no effects operate. **Answer: (B)** is the only molecule where all three effects operate.