Thionyl chloride is preferred in the preparation of chlorine compounds from alcohols because:
The reaction goes to completion
The by product being gases, escapes, hence there is no problem of separation of the product.
The reagent is cheap
None of the above
The thionyl chloride method is preferred over hydrogen chloride or phosphorous chloride method for the preparation of haloalkanes because both the by-products (SO2 and HCl) in this case are gases and escape leaving behind pure chloroalkane. This reaction takes place in the presence of