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 (ii) From amines by Sandmeyer’s reaction
When a primary aromatic amine, dissolved or suspended in cold
aqueous mineral acid, is treated with sodium nitrite, a diazonium
salt is formed Mixing the solution of freshly prepared diazonium
salt with cuprous chloride or cuprous bromide results in the
replacement of the diazonium group by –Cl or –Br