Free Radical Chemistry

Persulfates produce free radicals in many diverse reaction situations. When solutions of the persulfates are heated, free radicals are formed:
S2O8-2 + heat ——> 2SO4•-

In the presence of suitable monomers, the radical anions act as polymerization initiators to produce polymer molecules:

SO4•- + nCH2 = CH —> -O3SO(CH2(CH)n-1(CH2CH)
CH3 -                         |                                          |                     |
CH3 -                         R                                        R                    R

 Free radicals suitable as polymerization initiators are also generated in the presence of reducing agents, for example, the bisulfite anion:

S2O8-2 + HSO3- + 1/2O2 ——> HSO4- + 2SO4•-

Free radicals can also be generated in the presence of transition metals:

S2O8-2 + Fe+2 ——> Fe+3 + SO4-2 + SO4•-

and mercaptans:

S2O8-2 + 2RSH ——> 2HSO4- + 2RS