3.2.4 - Chlorination Of Alkanes

When do alkanes react with halogens

In the presence of UV light producing Halogenoalkanes

• UV light breaks down the halogens binds producing reactive intermediate (appears in the mechanism of the reaction but not in the overall balanced equation) called free radicals

• Free radicals attack the alkanes resulting in a series of reactions initiation, propagation and termination

Initiation

The halogen is broken down

Propagation

A hydrogen is replaced and the Cl• radical reformed as a catalyst

• this step can continue many times to result in multiple substitutions → this is a chain reaction

• Conditions of the reaction can be altered to favour the termination step and limit the no. Of substitutions

Termination

2 radicals join to end the chain reaction forming a stable product