Ambidentate Behavior of Cyanide [duplicate]








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[Adding cyanide vs nitrite for nucleophilic substitution and why does it change when we use silver salts for it](/questions/117754/adding-cyanide-vs-nitrite-for-nucleophilic-substitution-and-why-does-it-change-w)

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Why do haloalkanes give alkyl cyanides when treated with KCN but give alkyl isocyanide with AgCN?




The $\ce{KCN}$ substance is made of two ions : $\ce{K^+}$ and $\ce{CN^-}$ The active ion is cyanide, and the active atom in cyanide ion is the carbon atom, which is charged $-1$. This negative C atom attacks haloalkanes to produce alkylcyanide.
On the contrary, $\ce{AgCN}$ is not made of two ions. It is not soluble in water. The bond $\ce{Ag-C}$ is mainly covalent. So the active atom in $\ce{AgCN}$ is the outer $\ce{N}$ atom. When interacting with a haloalkane, the $\ce{N}$ atom has a free doublet which can attack it via a $\ce{S\_N2}$ mechanism to produce an isocyanide.


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