|Class 12 Chemistry Haloalkanes and Haloarenes||Methods of Preparation of aryl halides|
Methods of Preparation of aryl halides
This method can be used to prepare aryl chlorides and bromides. This is done by treatment of arene with chlorine or bromine in the absence of sunlight and in the presence of halogen carrier like AlCl3, FeCl3 etc. at low temperatures. It is an electrophilic substitution.
However the yield of Chlorobenzene is very poor as the main product is Triphenyl phosphate.
Diazonium salts are highly reactive compounds used to prepare arene derivatives. Treating diazonium salt with copper (I) chloride (Cu2Cl2) or copper (I) bromide (Cu2Br2) leads to the formation of corresponding haloarene. This reaction is known as Sandmeyer reaction.
Haloarenes can also be prepared by reaction of benzene diazonium chloride with copper powder in the presence of corresponding halogen acid. This reaction is termed as Gattermann reaction.