Trichloromethylperoxyl radical

Mico BA, Pohl LR. 1983. Reductive oxygenation of carbon tetrachloride trichloromethylperoxyl radical as a possible intermediate in the conversion of carbon tetrachloride to electrophilic chlorine. Arch Biochem Biophys 225 596-609. 

In the series of hydroxycyclohexadienylperoxyl radicals, one encounters the competition between the H02-/02- elimination leading to phenol [reactions (9) and (14)/(15)] and fragmentation of the ring (Pan et al. 1993). That latter has been attributed to an intramolecular addition of the peroxyl radical function to a diene double bond [reaction (24)]. This reaction is reversible [reaction (-24)], but when 02 adds to the newly created carbon-centered radical the endoperoxidic function is locked in [reaction (25)]. In analogy to reaction (24), the first step of the trichloromethylperoxyl-radical-induced oxidation of indole is its addition to the indole C(2)-C(3) double bond (Shen et al. 1989). 

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 > 8 x 104 s 1] than the subsequent hydrolysis of phosgene [reaction (43), k = 9 s 1 at 25 °C, / a = 53 kj mol1 Mertens et al. 1994]. 

This trichloromethylperoxyl radical can efficiently abstract hydrogen atoms from lipids and initiate lipid peroxidation... 

Some oxy-radicals lead to both electron transfer reactions and addition to the carotenoid. The most well studied is the trichloromethylperoxyl radical CCI3OO-, a peroxyl radical which is known to cause hepatotoxity and other types of tissue injury (Packer et al, 1981 Hill et al, 1995). Packer et al. (1981) showed that, in the presence of/3-carotene, there was a fast bleaching of the carotene ground state absorption with a rate constant of 1.5 x lO M s". The loss of absorption at 450 nm was accompanied by an increase in absorption in the near infrared region (950-1000 nm), indicating that the reaction produces the /3-carotene radical cation. 

Trichloromethylperoxyl radicals (CCl302 ) are frequently used to study the ability of compounds to scavenge ROO [120]. CCl302 were generated by radiolysis of an aqueous mixture of propan-2-ol and CCI4. Flavonoids showed variable rate constants 108 M-1 sec-1 for fisetin and morin, 107 M-1 sec-1 for myricetin and quercetin, and 106 M-1 sec-1 for catechin and epicatechin [121]. 

The trichloromethylperoxyl radical (CCI3OO ), involved in carbon tetrachloride hepatotoxicity (Slater 1987), has a reduction potential of > 1.1 V, but < 1.3 V from its lack of reactivity with deoxya-denosine 5 -monophosphate (Jovanovic and Simic 1988). The rate constant for the reaction of CCI3OO + ergothioneine was determined to be 1.2x10 M" s" (Asmus et al. 1996), surprisingly double the estimate obtained by Jovanovic and Simic (1991). 

---