Chapter 8.5: Mechanism of Halogenation of Alkanes

a step in a chain reaction characterized by the formation of reactive intermediates from nonradical or noncharged molecules

the number of times the cycle of chain propagation steps repeats in a chain reaction

Hammond’ Postulate

Step 1: Chain Initiation  Chain initiation involves formation of radicals from nonradical species. Dissociated by heat or light. Step 2: Chain Propagation  Chain propagation involves reaction of a radical and a molecule to form a new radical Step 3: Chain Termination Chain termination involves destruction of radicals. The first three possible chain termination steps involve coupling of radical to form a new covalent bond. The fourth chain termination step, called disproportionation, involves transfer of a hydrogen atom from the beta position of one radical to another radical and formation of an alkane and an alkene

chlrofluorocarbons (CFCs)

a step in a chain reaction characterized by the reaction of a reactive intermediate and a molecule to give a new reactive intermediate and a new molecule

compounds with one or two carbons, chlorine, and fluorine, formerly used as refrigerants

the structure of the transition state for an exothermic step looks more like the reactants of that step than the products. Conversely, the structure of the transition state for an endothermic step looks more like the products of that step than the reactants.

a step in a chain reaction that involves destruction of reactive intermediates

chain termination

chain initiation

chain length

chain propagation