Question

How are aralalkyl halides prepared?

Answer 1

Methods of preparation of aralkyl halides:

1. From Aralkyl Alcohols (Halogenation of Benzylic Alcohols):
   Aralkyl halides can be prepared by the reaction of benzylic (aralkyl) alcohols with halogenating agents such as phosphorus halides (PCl₃, PCl₅), thionyl chloride (SOCl₂), or hydrogen halides (HCl, HBr). The hydroxyl group is replaced by a halogen atom under these conditions.
   Example:
   Benzyl alcohol \[\ce{(C6H5CH2OH) + PCl3 ->\underset{Benzyl chloride}{(C6H5CH2Cl)}}\]
2. From Toluene (Free Radical Halogenation):
   The benzylic position of toluene or other alkyl-substituted arenes undergoes free radical halogenation when treated with halogens (Cl₂ or Br₂) in the presence of light or heat. This selectively substitutes one or more benzylic hydrogens with halogen atoms to give benzyl halides.
   Example:
   \[\ce{C6H5CH3 + Br2 ->[(hv or heat)][]C6H5CH2Br + HBr}\]