Question

Identify the product $(P)$ and $(Q)$ in the reactions.
$RX+AgCN \rightarrow \left(P\right)+AgX;$
$RX+KCN \rightarrow \left(Q\right)+KX$

• A. (P) $ \rightarrow $ RCN, (Q) $ \rightarrow $ RCN
• B. (P) $ \rightarrow $ RCN, (Q) $ \rightarrow $ RNC
• C. (P) $ \rightarrow $ RNC, (Q) $ \rightarrow $ RCN
• D. (P) $ \rightarrow $ RNC, (Q) $ \rightarrow $ RNC

Answer 1

Answer: (C)

$RX+AgCN \rightarrow \underset{\left(P\right)}{R N C}+AgX$
$RX+KCN \rightarrow \underset{\left(Q\right)}{R C N}+KX$
Both C and N can donate electron pairs. Since KCN is predominantly ionic and $C-C$ bond is more stable than $C-N$ bond in case of KCN, attack takes place through carbon atom.
AgCN is predominantly covalent hence only nitrogen pair is available for bonding resulting in formation of isocyanide.