Peroxyl Radicals - Free-Radical-Induced DNA Damage and Its Repair - page 161

8.7
O-Transfer Reactions

O-transfer reactions of peroxyl radicals are sometimes referred to as two-elec-
tron reductions (Bonifacic et al. 1991; Schöneich et al. 1991; Merényi et al. 1994),
in analogy to the one-electron reduction discussed above, although the reac-
tion type is quite different. It requires the addition of the peroxyl radical to an
electron-rich center and is thus reminiscent of the O-transfer in ozone reactions
(Muñoz and von Sonntag 2000; Muñoz et al. 2001; Flyunt et al. 2003). In some
cases, this complex may simply decay into an oxyl radical and an oxide as ob-
served with diaryltellurides (Engman et al. 1995), phosphines (Engman et al.
1995) and disulfides [Schöneich et al. 1991; Bonifacic and Stefanic 2000; e.g.,
reaction (38)].

R-O-O • + (CH 3 ) 2 S → R-O • + (CH 3 ) 2 S=O (38)

In the case of tellurides, strongly oxidizing peroxyl radicals may also undergo
ET in competition, and the adduct to phosphines may be sufficiently long-lived
to react further with O 2 (Engman et al. 1995).
The trichloromethylperoxyl radical adds to the iodide ion [reaction (39)]
with subsequent decomposition into the trichloromethoxyl radical [reaction
(40)] which is further reduced by iodide into trichloromethanol [reaction (41);
Bonifacic et al. 1991]. Its decay is much faster [reaction (42), k

10 4 s − 1 ] than
the subsequent hydrolysis of phosgene [reaction (43), k = 9 s − 1 at 25 °C, E a = 53 kJ
mol − 1 ; Mertens et al. 1994].

≥ 8 ×