Alkanes are called paraffins. They undergo substitution reactions with chlorine in the presence of sunlight. Prove this with a suitable example.

Alkanes, commonly known as paraffins, can indeed undergo substitution reactions with chlorine when exposed to sunlight. This process is known as free radical halogenation.

What Happens During the Reaction?

In the presence of ultraviolet (UV) light, chlorine molecules (Cl₂) break apart into individual chlorine atoms. These highly reactive atoms can then replace hydrogen atoms in alkanes, leading to the formation of chlorinated alkanes.

Example: Reaction of Methane with Chlorine

Let's consider the reaction between methane (CH₄) and chlorine:

• Step 1: Initiation - UV light causes Cl₂ to dissociate into two Cl atoms:
• Cl₂ → 2 Cl·
• Step 2: Propagation - A chlorine atom reacts with methane, replacing a hydrogen atom:
• CH₄ + Cl· → CH₃Cl + H·
• Step 3: Further reactions can occur, leading to more chlorinated products:
• CH₃Cl + Cl· → CH₂Cl₂ + H·

Final Thoughts

This example illustrates how alkanes like methane can react with chlorine in sunlight, resulting in the substitution of hydrogen atoms with chlorine atoms, thus forming chlorinated compounds. This reaction is significant in organic chemistry and industrial applications.