Kharasch addition

[1] The reaction is used to append trichloromethyl or dichloromethyl groups to terminal alkenes.

The method has attracted considerable interest,[2] but it is of limited value because of narrow substrate scope and demanding conditions.

[3] The reaction mechanism involves free radicals of the general formula CXCl2 (X = Cl, H).

For the precursors carbon tetrachloride and chloroform, the requisite radicals can arise by abstraction of a halogen atom by a electropositive metal.

[4] This addition is a step in a protocol known as atom transfer radical polymerization.