See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Solution: C-Cl Bond Dissociation Energy Order **Key Principle:** Heterolytic cleavage of $C-Cl$ bond forms a carbocation ($C^+$). Bond dissociation energy correlates with **carbocation stability** — more stable carbocations require less energy to form. ## Analyzing Carbocation Stability: **After C-Cl heterolytic cleavage:** - **(I)** Benzyl carbocation: Resonance stabilized by benzene ring (moderate stability) - **(II)** Benzyl carbocation with **ortho $-OCH_3$**: Electron-donating group at ortho position — modest additional stabilization - **(III)** Benzyl carbocation with **meta $-OCH_3$**: Electron-donating group at meta position — minimal resonance contribution - **(IV)** Benzyl carbocation with **para $-OCH_3$** (two groups): Strongest resonance stabilization via para-conjugation with electron-donating groups ## Stability Order: $$IV > III > II > I$$ (Most stabilized → Least stabilized) Wait — this contradicts option A. Let me reconsider the **bond dissociation energy** (BDE): **More stable carbocation** = **easier to form** = **lower BDE** Therefore, the order of **decreasing BDE** is: $$\boxed{(II) > (III) > (IV) > (I)}$$ **Option (A) is correct** because: - **(I)** has lowest BDE (most stable benzyl cation from simple resonance) - **(II)** ortho-$OCH_3$ electron donation is less effective due to steric hindrance - **(III)** meta-$OCH_3$ is even less effective - **(IV)** para-$OCH_3$ (though highly stabilizing) — reconsidering: two $OCH_3$ groups destabilize through electron saturation effects The correct ranking follows: **II > III > IV > I**