Free Radical Addition Reaction
Free-radical addition takes place in the presence of heat or light or radical initiator. Radical additions are known for a variety of unsaturated substrates, both olefinic or aromatic and with or without heteroatoms. The product of free radical addition is just reverse of ionic addition that means follows Anti-Markovnokov's rule.
Free-radical reactions depend on one or more relatively weak bonds in a reagent. Under reaction conditions, some weak bonds breaks homolytically into radicals and then reaction proceeds.
Mechanism of Free Radical Addition Reaction
Free radical mechanism takes place in three steps: Chain initiation, Chain propagation and Chain termination. The termination step produce by-product which is generally useless.
Free Radical Addition Reactions of Conjugated Dienes
Conjugated dienes also undergo addition reactions by radical-chain mechanisms. The addition product almost always is the 1,4 adduct. Thus radical addition of hydrogen bromide to 1,3-butadiene gives l-bromo-2-butene.
