Final answer:
A free radical is a molecule with an unpaired electron that is highly reactive; an example is carbon with three bonds and one unshared electron. Free radical polymerization involves the sequential addition of monomers to a growing polymer chain propagated by radicals. The free radical reaction mechanism consists of initiation, propagation, and termination steps.
Step-by-step explanation:
Free Radical Reactions
In the context of chemistry, a free radical is typically a molecule with an unpaired electron, making it highly reactive. For instance, a radical with a carbon atom that has three bonds and one unshared electron can be denoted as H-C-H, where the carbon is sp2 hybridized. This unshared electron resides in a partially filled p-orbital, making it ready to accept another electron to form a new bond, a behavior detailed in Figure 1.5.1a.
Free radical polymerization is a process where monomers combine with free radicals to form a polymer chain. During this process, the radical is regenerated at the end of each addition step to propagate the chain reaction. The formal charge of an atom in a radical is different from when it is in a non-radical form because it doesn't share the unpaired electron.
The mechanism of a free radical reaction involves three essential steps: initiation, where a free radical is generated; propagation, where the growing chain reacts with more monomers; and termination, where two radicals combine to end the chain growth. In Figure 4.2, the general steps of these reactions are illustrated. It is important to note that these reactions are sensitive to conditions and require precise control to prevent unwanted reactions.