(i) From hydrocarbons by electrophilic substitution
Aryl chlorides and bromides can be easily prepared by electrophilic
substitution of arenes with chlorine and bromine respectively in the
presence of Lewis acid catalysts like iron or iron(III) chloride The ortho and para isomers can be easily separated due to large
difference in their melting points Reactions with iodine are reversible
in nature and require the presence of an oxidising agent (HNO3,
HIO4) to oxidise the HI formed during iodination Fluoro compounds
are not prepared by this method due to high reactivity of fluorine