Question

Account for the following:
(i) Allyl chloride is hydrolysed more readily than n-propyl chloride.(ii) Isocyanides are formed when alkyl halides are treated with silver cyanide.
(iii) Methyl chloride reacts faster with OH– ion in SN2 reaction than ethyl chloride.

Hint:

SN2 favors primary halides with minimal steric hindrance; resonance also stabilizes intermediates in SN1.

Answer 1

(i) Allyl chloride is hydrolyzed more readily than n-propyl chloride.

Solution:

Allyl chloride undergoes a faster SN1 reaction because the carbocation formed is resonance stabilized. In contrast, n-propyl chloride does not form such a stable carbocation, making its hydrolysis slower.

(ii) Isocyanides are formed when alkyl halides are treated with silver cyanide.

Solution:

AgCN is covalent and favors the formation of isocyanides (\( \text{R-NC} \)) due to bond formation through nitrogen rather than carbon. Unlike KCN, which is ionic and gives nitriles (\( \text{R-CN} \)), AgCN facilitates the formation of isocyanides.

(iii) Methyl chloride reacts faster with OH^– ion in SN2 reaction than ethyl chloride.

Solution:

In SN2 reactions, less steric hindrance facilitates the reaction. Methyl chloride has no bulky groups attached to the carbon, making it more reactive than ethyl chloride, which has one additional methyl group.