Which of the following pair of compounds on heating gives butanenitrile?

Step-by-step solution

Butanenitrile ( CH₃ CH₂ CH₂ CN ) contains four carbon atoms. Its synthesis from an alkyl halide with three carbons via nucleophilic substitution with cyanide is effective, since the cyanide group contributes one additional carbon. Propanol, butanol, and n-butylchloride are unsuitable: alcohols require prior conversion to alkyl halides, and n-butylchloride would yield a five-carbon nitrile. In contrast, n-propylchloride ( CH₃ CH₂ CH₂ Cl ) reacts with alcoholic KCN under heat to form butanenitrile: CH₃ CH₂ CH₂ Cl + K