The combination of Fe-II(DPAH)(2) (DPAH(2) = 2,6-dicarboxypyridine) and O-2 in a 2:1 pyridine/acetic acid solution results in a rapid autoxidation to produce HOOH and Fe-III(DPA)(DPAH) (k(1), 1.8 +/- 0.5 M(-1) s(-1)). The resultant HOOH reacts with excess Fe-II(DPAH)(2) via a nucleophilic addition to give a Fenton reagent [(DPAH)(2)(FeOOH)-Fe---O-II + pyH(+)] (1) that reacts with (a) excess Fe-II(DPAH)(2) to give Fe-III(DPA)(DPAH) [k(2), (2 +/- 1) X 10(3) M(-1) s(-1)], (b) excess c-C6H12 and PhSeSePh (a carbon radical trap) to give c-C(6)H(11)SePh [kinetic isotope effect (KIE) (k(c-C6H12)/k(c-C6D12)), 2 2], and (c) excess O-2 to form an adduct [1(O-2)], which reacts with excess c-C6H12 via an intermediate [(DPAH)(2)Fe-IV(OH)(OOC6H11)l (6) and Fe-II(DPAH)(2) to give c-C6H10(O) (KIE, 2.0) and Fe-III(DPA)(DPAH) [32 mM Fe-II(DPAH)2, O-2(1 atm, 3.4 mM), and 1 M c-C6H12 yield 6 mM c-C6H10(O)]