General Methods of Preparation of Haloalkanes
1 . From Alcohols
In Groove ’ s method , ZnC12 is used to weaken the C-OH bond . In case of 3 ° alcohols , ZnC12 is not required .
The reactivity order of halogen acids is HI > HBr > HCl .
Darzen procedure is the best method for preparing alkyl halides from alcohols since both the by products ( SO2 and HCl ) are gaseous and escape easily .
2 . Free Radical Halogenation of Alkanes
Addition of Hydrogen Halides on Alkenes