Question

Among PCl₅ and SOCl₅, which reagent is preferred for the preparation of chloroalkanes from alcohols?

Answer 1

1. Thionyl chloride (SOCl₂) is preferred over phosphorus pentachloride (PCl₅) for preparing chloroalkanes from alcohols.
2. SOCl₂ reacts with alcohols to form alkyl chlorides while releasing gaseous byproducts (SO₂ and HCl), which escape and drive the reaction to completion, resulting in cleaner products and easier purification.
3. In contrast, PCl₅ produces several byproducts like POCl₃ and HCl, making the reaction harsher and purification more difficult.
4. Additionally, SOCl₂ operates under milder conditions and is more selective, reducing side reactions.

Thus, SOCl₂ is generally the reagent of choice for converting alcohols to chloroalkanes.