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Why does the reaction of haloalkanes with KCN give predominantly an alkyl cyanide (R-CN), but with AgCN gives predominantly an alkyl isocyanide (R-NC)?
AKCN catalyses the reaction
BAgCN has a different oxidation state
CCN⁻ is an ambidentate nucleophile. KCN is ionic → free CN⁻ attacks through C (forming C-C bond, more stable). AgCN is more covalent → only N donates its lone pair, giving the isocyanide
DThere is no difference; same product
Answer & Solution
Correct answer: C. CN⁻ is an ambidentate nucleophile. KCN is ionic → free CN⁻ attacks through C (forming C-C bond, more stable). AgCN is more covalent → only N donates its lone pair, giving the isocyanide
**CN⁻ is ambidentate** — can bond through C or N. **KCN (ionic) → free CN⁻ ion → attacks through C** (more stable C-C bond) → alkyl cyanide. **AgCN (largely covalent) → only the N lone pair is available** → forms R-NC (isocyanide). Classic NEET-favourite distinction.
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