See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Stability of Carbonium Ions **Key Principle:** Carbonium ion stability depends on: 1. Hyperconjugation (donation of C-H bonds to the empty p-orbital) 2. Inductive effects (alkyl groups stabilize positive charge) 3. Resonance stabilization **Analysis of each option:** **(A) $Ph_3C^+$ (trityl cation)** - Three phenyl groups surround the carbocation - Extensive **resonance stabilization**: the positive charge is delocalized across all three benzene rings - Each phenyl contributes electron density through resonance into the vacant p-orbital - Maximum stabilization through both inductive and resonance effects **(B) $(CH_3)_3C^+$ (tert-butyl cation)** - Three alkyl groups provide hyperconjugation and inductive stabilization - No resonance stabilization available - Secondary to option A **(C) $(CH_3)_2CH^+$ (isopropyl cation)** - Only two alkyl groups - Less hyperconjugation than option B **(D) $CH_2=CH-CH_2^+$ (allyl cation)** - Resonance stabilization present but limited to one $\pi$ bond - Less extensive delocalization than option A **Conclusion:** Option (A) is most stable because the **triphenylmethyl cation** has three aromatic rings that provide extensive resonance stabilization, distributing the positive charge across multiple $\pi$ systems—far superior to any aliphatic carbonium ion. **Answer: (A)**