Homolytic bond breaking occurs when a molecule breaks up to form two or more new products. In the reaction given, molecular chlorine forms two radicals in which one electron stays with each fragment formed.

The radical reaction would create the anti-Markovnikov product shown and both , hv and , AIBN (azobisisobutyronitrile) effectively cause radical reactions. The bromine would then be substituted with the group.

The double bond in 1-hexene is across carbons one and two. Just adding HBr would put the bromine on carbon 2 because the bromine is more stable on the more highly subtituted carbon. If you want to put the bromine on the less substituted carbon (generating 1-bromohexane), you must carry out the reaction in the presence of peroxides. The mechanism involves a free radical on the secondary carbon and a bromine addition on the primary carbon.

The most substituted atom is most likely to be attacked, as a radical intermediate would be created. The radical intermediate would be most stable on the most substituted carbon.

Termination is the only step that does not generate a radical product. The termination step ends the reaction by bringing together two radical molecules to produce a stable non-radical product.