Haloakanes react with KCN to form alkyl cyanides as main product while AgCN forms isocyanides as the chief product . Explain .

Explanation

KCN is mainly ionic compound and provides cyanide ions in solution. Though each carbon and nitrogen carry a lone pair of electrons, the lone pair on carbon is more reactive. The carbonium ion, `R^(+)`, preferentially combines with the carbon atom of the cyanide group and forms alkyl cyanide.
On the other hand, AgCN is mainly a covalent compound and only nitrogen has the lone pair of electrons. Thus, carbonium ion attacks through nitrogen and thereby forms an alkyl isocyanide.