See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

## Solution: Identifying the Most Electron-Rich Ring **Step 1: Analyze the electron-donating groups attached to benzene** The electron density of the benzene ring depends on the electron-donating ability of substituents: - $\text{PhCH}_3$: methyl group ($-CH_3$) - $\text{PhEt}$: ethyl group ($-C_2H_5$) - $\text{Cumene}$: isopropyl group ($-CH(CH_3)_2$) - $\text{PhCMe}_3$: tert-butyl group ($-C(CH_3)_3$) **Step 2: Compare inductive effects** All substituents are alkyl groups, which are electron-donating through the **inductive effect** (σ-donation). The electron-donating ability follows the trend of alkyl group stability and size considerations at the α-carbon. **Step 3: Assess hyperconjugation** Hyperconjugation (σ-orbital overlap with benzene π-system) increases with the number of α-hydrogens: - $-CH_3$: **3 α-hydrogens** → strongest hyperconjugation - $-C_2H_5$: 2 α-hydrogens - $-CH(CH_3)_2$: 1 α-hydrogen - $-C(CH_3)_3$: 0 α-hydrogens (no α-H) **Step 4: Conclusion** The methyl group ($-CH_3$) in **$\text{PhCH}_3$ (toluene)** provides the strongest electron donation to the benzene ring through maximum hyperconjugation. This makes the ring most electron-rich and most reactive toward electrophilic aromatic substitution. **Answer: (A) PhCH₃**