Learning Objective: To learn the two different ways a free radical reacts and the mechanism it undergoes.
Skill Level - Intermediate
Prerequisites:
Resonance (Chapter – Electronic Displacements of a Covalent Bond)
Chapter: Reactive Intermediates
Sub-topic: Free Radicals
Author's Note: Free radical reactions are imagined proceeding without a harness. However, there are two ways by which it reacts – propagation followed by termination. I have covered four ways by which a free radical undergoes the propagation reaction and two ways by which the reaction terminates. Also, I have included the role of reaction inhibitors and their mechanism in quenching a free radical species.
Fate of Free Radicals
Free radicals act by propagating or terminating a reaction.
Propagation
The propagation reactions are those where the free radicals lead to reactions that form other new radicals. These new radicals must again react further, therefore, growing the reaction.
There are four main propagation reactions (atom abstraction, addition to multiple bonds, fragmentation or decomposition, and rearrangement), of which the first two are the most common....

Termination (Dimerization or disproportionation reaction)
The reaction commonly terminates by a simple combination...
Another termination process is the...
Role of Radical Inhibitors in reaction termination
Radical inhibitors such as hydroquinone, BHT....
