Radical halogenation is the replacement of a hydrogen atom on an alkane by a halogen atom, proceeding through a free-radical chain mechanism. It matters as the principal way to introduce a functional group into otherwise unreactive alkanes. The reaction is started by ultraviolet (UV) light or heat, which splits the halogen into radicals; these then propagate through a cycle of hydrogen abstraction and halogen transfer until the chain terminates.

自由基卤代是把烷烃上的一个氢原子替换为一个卤素原子的反应,通过自由基链式机理进行。它之所以重要,是因为它是向原本不活泼的烷烃中引入官能团的主要途径。该反应由紫外(UV)光或加热引发,使卤素分裂为自由基;这些自由基随后通过夺氢和转移卤素的循环进行链传递,直到链终止。