Question

Sol. [Key Concept: Nitrile formation and Hofmann degradation]

CN⁻ displaces I⁻ from 1-iodopropane by SN2 to give A,

CH₃CH₂CH₂CN, butanenitrile. Partial hydrolysis gives B,

CH₃CH₂CH₂CONH₂, butanamide. Br₂/NaOH causes Hofmann bromamide degradation, removing the carbonyl carbon and giving C,

CH₃CH₂CH₂NH₂, propan-1-amine.

Hence, option (3). The cyanide step adds one carbon, while the Hofmann step removes one.