Question

Why are oxidizing agents like $HN{O_3}$ and $HI{O_3}$ are used in the iodination of alkanes?

Answer 1

Alkanes are acyclic saturated hydrocarbons. They consist of hydrogen and carbon atoms arranged in a tree structure in which all the carbon-carbon bonds are single. Iodination is a process in which iodine is introduced in the molecule.

Complete step by step answer:
Iodination of alkanes is carried out in the presence of oxidizing agents because one of the products is hydrogen iodide, which is a strong reducing agent and it converts alkyl iodide back to an alkane. Alkanes undergo very few reactions. The two most important reactions are combustion and halogenation.
Further, iodination is a reversible reaction because $HI$ is a very strong reducing agent.
Now, let us consider a reaction
$C{H_3}C{H_3}\underset{{h\nu }}{\overset{I}{\longleftrightarrow}}C{H_3}C{H_3}I + HI$
Since the reaction is reversible in nature, we use oxidizing agents like $HN{O_3}$ or $HI{O_3}$ to destroy HI. These oxidizing agents further oxidize HI to ${I_2}$and make the reaction irreversible.
Moreover, alkyl groups are non-polar due to almost similar electronegativity of carbon and hydrogen. The haloalkanes are less soluble in water. Some amount of energy is required to overcome the attractions between the haloalkane molecules and to break the hydrogen bond between the water molecules to make them dissolve in water.
Hence, HI is a strong reducing agent and it reduces alkyl iodide back to alkanes.

Note:
Iodo Arenes are also difficult to synthesize because the reaction is reversible and the HI produced is a strong reducing agent to reduce iodobenzene back to benzene. Moreover, alkanes are saturated hydrocarbon which means that their carbon atoms are joined together by single bonds and this makes them relatively unreactive.