Peroxy Radicals and Singlet Oxygen (1O2) from the Addition of Superoxide Ion (O2-·) to CCl4, CF3CCl3, PhCCl3, N-BuBr and N-BuCl in Acetonitrile
The initial product from the reaction of RX(R=Cl3C, F3CCCl2, PhCCl2, PhC(O), nBu, X=Cl; R=nBu, X=Br) with O 2 - -is ROO-, which can be reduced by a second O 2 - · to form ROO- (a reactive nucleophile) or can dimerize to form ROOOOR. The latter dissociates homolytically to ROOR and O2. The longer-lived forms of tetraoxide react with (1) 1,4-cyclohexadiene-(1,4-CHD) via dehydrogenation to give PhH, ROOR, and HOOH, (2) diphenylisobenzofuran via dioxygenation to give dibenzoylben-zene and ROOR, and (3) rubrene via dioxygenation to give its endoperoxide and ROOR. Thus the reactivity of ROOOOR parallels that of singlet oxygen (1O2). Because of its diffusion-controlled dimerization, the primary product from the RX/O 2 - · reaction (CCl3COO· for CCl4/O 2 - ·) does not exhibit any reactivity with the allyl hydrogens of 1,4-CHD. Hence, at millimolar concentrations this peroxy radical (the suspected cytotoxin from the aerobic activation of CCl4) does not exist long enough to react with allylic hydrogens. The biological hazard of CCl4 may be due to the transient formation of Cl3COOOOCCl3.
KeywordsSinglet Oxygen Peroxy Radical Millimolar Concentration Aerobic Activation Reactive Nucleophile
Unable to display preview. Download preview PDF.
- 3.D.T. Sawyer, M.S. McDowell, and K.S. Yamaguchi, Reactivity of Perhydroxyl(H00-) in Aprotic Media, Chem. Res. Toxicology 1:000 (1988).Google Scholar
- 4.G.W. Burton, D.O. Foster, B. Perly, T.F. Slater, I.C.P. Smith, and K.U. Ingold, Biological antioxidants, Phil. Trans. R. Soc. Lond. B311:565 (1985).Google Scholar
- 5.C.S. Foote, Light, oxygen, and toxicity, in: Pathology of Oxygen, Academic Press, New York (1982).Google Scholar
- 6.T.F. Slater, Activation of carbon tetrachloride: Chemical principles and biological significance, in: “Free Radicals Lipid Peroxidation and Cancer,” D.C.H. McBrien and T.F. Slater, eds., Academic Press, New York (1982).Google Scholar
- 7.T.F. Slater, K.H. Cheeseman, and K.O. Ingold, Carbon tetrachloride toxicity as a model for studying free-radical mediated liver injury, Phil. Trans. R. Soc. Lond. B311:633 (1985).Google Scholar