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(CH2C•H)
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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•