Free Radical Halogenation

Initiation

Formation of a reactive intermediate

Propagation

Reactive intermediate reacts with stable molecule to produce another reactive intermediate or a product molecule

Termination

Side reactions that destroy the reactive intermediates, often resulting in nonradical product

Free Radicals

Species with odd numbers of electrons, stability determined by compound structure

Homolytic Cleavage

Bond cleavage resulting in free radicals, with electrons going to different atoms

Heterolytic Cleavage

Bond cleavage resulting in ions, with electrons going to the same atom

Primary

Halide bonded to a carbon atom bonded to only one other carbon atom, weak and least preferred

Secondary

Halide bonded to a carbon atom bonded to two other carbon atoms, slightly more stable

Tertiary

Halide bonded to a carbon atom bonded to three other carbon atoms, highly stable and preferred

Resonance

Increases stability of intermediate, preferred when exhibiting resonance

Exothermic Reaction

Weak bonds broken/strong bonds formed, releases energy

Endothermic Reaction

Strong bonds broken/weak bonds formed, requires input of energy

Chlorination Process

Highly exothermic process

Transition States

Highest position on the graph, where reactants change into products

Activation Energy

Difference between starting reactants energy and transition states energy

Rate-Limiting Step

Hump in the graph with highest energy, determines the overall reaction rate

Electronegativities

Higher values lead to quicker reactions, inversely proportional to size

Bond Dissociation Energy (+BDE)

Energy input required, useful in assessing energetics of a chemical reaction

Bond Formation Energy (-BDE)

Energy released, useful in assessing energetics of a chemical reaction

Hammond's Postulate

Related species similar in energy must be similar in structure, transition state resembles nearest stable molecule

Bromination

Highly selective reaction

Chlorination

Non-selective reaction