See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Ether Cleavage by Halogen Acids ## Mechanism of Ether Cleavage Ethers undergo cleavage via an $S_N1$ mechanism with protonation followed by nucleophilic attack: $$R-O-R' + HX \rightarrow R-O^+H-R' + X^- \rightarrow \text{Products}$$ ## Determining Reactivity Order The reactivity depends on **two factors**: 1. **Acidity of HX** — stronger acids protonate the ether more readily 2. **Nucleophilicity of $X^-$** — stronger nucleophiles attack the carbocation faster | Acid | Acidity | Nucleophilicity of $X^-$ | Overall Effect | |------|---------|--------------------------|-----------------| | $HI$ | Moderate | **Very high** ($I^-$ is excellent nucleophile) | **Highest reactivity** | | $HBr$ | Moderate | High ($Br^-$) | **Intermediate** | | $HCl$ | Moderate | Lower ($Cl^-$ is weak nucleophile) | **Lowest reactivity** | ## Key Point Although **HCl is most acidic**, ether cleavage is controlled primarily by **nucleophilicity of the halide ion**, not acid strength. The $I^-$ ion (largest, most polarizable) is the strongest nucleophile despite HI being a weaker acid than HCl. **Reactivity order: $HI > HBr > HCl$** **Answer: (A)**