13.2.1—Organic reaction terminology

A homologous series shares a functional group and general formula, with successive members differing by CH₂. Saturated compounds contain no carbon–carbon multiple bond; unsaturated compounds do.

Homolytic fission splits a bond evenly to form radicals, while heterolytic fission gives both electrons to one atom and forms ions. In radical chemistry, initiation creates radicals, propagation consumes and regenerates them, and termination removes radicals.

UV light can split Cl₂ homolytically: Cl₂ → 2Cl·. A chlorine radical then abstracts H from methane, beginning a propagation chain.

A radical is not simply an ion, and “unsaturated” does not mean every bond is weak. Match the term to the electron movement shown.