Question

$\mathrm{KCN}$ on reacting with haloalkanes form:

Answer 1

Nucleophilic Substitution:

1. A nucleophilic substitution reaction is an organic process in which one nucleophile is substituted by another.
2. The nucleophile ${\mathrm{CN}}^{-}$ is an ambient nucleophile, meaning it can form bonds with both Carbon and Nitrogen atoms.
3. Haloalkanes are open-chain hydrocarbons in which one or more than one hydrocarbon is replaced by halogen.
4. Because KCN is an ionic molecule, both Carbon and Nitrogen sides are available for bond formation, but the $\mathrm{C}-\mathrm{C}$bond is stronger than the $\mathrm{C}-\mathrm{N}$ bond, resulting in cyanide production.
5. General representation of reaction is $\mathrm{RX}+\mathrm{KCN}\to \mathrm{RCN}$
6. Example: $\underset{\mathrm{Ethyl}\mathrm{iodide}}{{\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{I}}+\underset{\mathrm{Potassium}\mathrm{thiocyanate}}{\mathrm{KCN}}\to \underset{\mathrm{Ethyl}\mathrm{cyanide}}{{\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{CN}}+\underset{\mathrm{Potassium}\mathrm{Iodide}}{\mathrm{KI}}$

Therefore, Haloalkanes on reacting with $\mathrm{KCN}$ gives Alkyl Cyanide