Question

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

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

Answer 1

Answer: (C)

$RX+AgCN\to \underset{\left(P\right)}{\mathrm{RNC}}+AgX$
$RX+KCN\to \underset{\left(Q\right)}{\mathrm{RCN}}+KX$
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.