Question

What is substitution reaction of alkanes?

Answer 1

When a H atom in the alkane is replaced by another different atom.

Explanation:

Alkanes undergo free radical substitution with halogens in the presence of uv light or even in the dark when heated to about 300 Celsius.

Initially chloromethane + HCl(g) forms, but further substitutions are possible and di- tri- and tetrachlromethane can form.

The reaction also forms methyl radicals, which can react to form ethane and all the H atoms in ethane can be replaced as well. The products can get very complicated. It is not therefore, a great way to make halogenoalkanes. This is better done by using an alkene an HX.