Allyl chloride is more reactive than n-propyl chloride towards nucleophilic substitution reaction. Explain why?

Resonance Stabilization: Allyl chloride has a π bond adjacent to the reactive site (the carbon bonded to chlorine), allowing for resonance stabilization. The π electrons can delocalize onto the adjacent carbon, dispersing the negative charge over the allylic system. This resonance stabilization lowers the energy of the transition state, making it easier for the nucleophile to attack.

Hyperconjugation: The presence of the π bond also enables hyperconjugation, where the σ C-H bonds adjacent to the π system can donate electron density to stabilize the developing negative charge on the carbon undergoing substitution. This additional stabilization further facilitates the reaction.

Stability of the resulting product: The product formed after nucleophilic substitution in allyl chloride involves a double bond, which is generally more stable than the single bond in the starting material. The thermodynamic stability of the product also drives the reaction forward.

In contrast, n-propyl chloride lacks such resonance stabilization or significant hyperconjugation effects. The absence of these stabilizing factors makes the nucleophilic substitution reaction slower and less favorable compared to allyl chloride.