Reaction of halo alkane with KCN and AgCN | Class XII CBSE & ISC Board | By Dr. Vikas Yadav

1. Reaction with Potassium Cyanide (KCN):
- Nucleophile: In KCN, the cyanide ion (CN⁻) exists primarily as a free ion with the carbon atom as the nucleophile.
- Reaction: The carbon of the cyanide ion attacks the carbon in the haloalkane via an SN2 mechanism.
- Product: Alkyl cyanides (nitriles) are formed.
General Reaction:
R-X + KCN → R-CN + KX
CH₃Br + KCN →CH₃CN + KBr
- Nature of Product: The product will have a carbon-nitrogen triple bond (nitrile).

2. Reaction with Silver Cyanide (AgCN):
- Nucleophile: In AgCN, the cyanide is covalently bonded to the silver ion, and the nitrogen atom acts as the nucleophile rather than the carbon.
- Reaction: The nitrogen attacks the carbon in the haloalkane, leading to the formation of an alkyl isocyanide (isonitrile).
- Product: Alkyl isocyanides are formed.
R-X + AgCN → R-NC + AgX
CH₃Br + AgCN → CH₃NC + AgBr
- Nature of Product: The product will have a nitrogen-carbon triple bond (isonitrile).
Key Differences:
- With KCN: Forms an alkyl cyanide (R-CN).
- With AgCN: Forms an alkyl isocyanide (R-NC).

The difference in products is due to whether the carbon or nitrogen of the cyanide group acts as the nucleophile.

Тэги:

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