Question

Why thionyl chloride is preferred for preparing haloalkane?

Answer 1

Thionyl chloride is preferred for preparing alkyl chlorides from alcohols because the by-products formed in the reaction are SO2 and HCl which are in gaseous form and escape into the atmosphere leaving behind pure alkyl chlorides.

CH3CH2−OH+SOCl2⟶CH3CH2−Cl+SO2↑+HCl↑