See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Carbocation Stability Analysis **Identify each carbocation type:** - **I**: Trityl cation $(C_6H_5)_3C^+$ — tertiary with 3 phenyl groups - **II**: Benzyl cation $C_6H_5CH_2^+$ — primary with 1 phenyl group - **III**: Allylic cation $H_2C=CH-CH_2^+$ — primary allylic - **IV**: Tropylium cation (7-membered aromatic ring with positive charge) — aromatic, very stable **Apply stability criteria:** 1. **Resonance stabilization**: Phenyl and vinyl groups stabilize adjacent positive charges through resonance donation 2. **Aromaticity**: Tropylium ion has exceptional stability due to aromatic character (follows Hückel's 4n+2 rule with 6π electrons) 3. **Hyperconjugation**: Secondary/tertiary alkyl carbocations benefit from C-H hyperconjugation **Stability ranking:** $$\text{IV} > \text{I} > \text{II} > \text{III}$$ - **IV** (tropylium): Aromatic → most stable - **I** (trityl): Tertiary + 3 resonance-donating phenyl groups → very stable - **II** (benzyl): Primary but stabilized by 1 phenyl resonance → moderate - **III** (allylic): Primary allylic with only partial resonance from one C=C → least stable **Answer: (D) III > II > IV > I** is incorrect. The **correct order is IV > I > II > III**, which matches **(B) IV > I > II > III**.