Superoxide ions reactions

Contents Introduction and Principles. - The Reaction of Dichlorocarbene With Olefins. - Reactions of Dichlorocarbene With Non-Olefinic Substrates. -Dibromocarbene and Other Carbenes. - Synthesis of Ethers. - Synthesis of Esters. - Reactions of Cyanide Ion. - Reactions of Superoxide Ions. - Reactions of Other Nucleophiles. - Alkylation Reactions. - Oxidation Reactions. - Reduction Techniques. - Preparation and Reactions of Sulfur Containing Substrates. -Ylids. - Altered Reactivity. - Addendum Recent Developments in Phase Transfer Catalysis. 

HP here is great interest in the biochemistry and relevant coordination chemistry of copper-containing proteins (1,2, 3, 4, 5). They are widely distributed in both plants and animals and are often involved in oxygen metabolism, transport, and use. One of the most actively studied copper proteins is bovine erythrocyte superoxide dismutase (SOD) (6,7,8). This enzyme catalyzes the dismutation of superoxide ion, Reaction 1. 

Moro-Oka YC, Pyoimg J, Arakawa H, Ikawa T. Chemistry of superoxide ion. Reaction of superoxide ion with substrates having labile hydrogens. Chem Lett 1976 11 1293-1296. 

The principal product of the reaction of the alkali metals with oxygen varies systematically down the group (Fig. 14.15). Ionic compounds formed from cations and anions of similar radius are commonly found to he more stable than those formed from ions with markedly different radii. Such is the case here. Lithium forms mainly the oxide, Li20. Sodium, which has a larger cation, forms predominantly the very pale yellow sodium peroxide, Na202. Potassium, with an even bigger cation, forms mainly the superoxide, K02, which contains the superoxide ion, O,. ... 

Starke, P.E., and Farber, J.L. (1985). Ferric iron and superoxide ions are required for the killing of cultured hepatocytes by hydrogen peroxide. Evidence for the participation of hydroxyl radicals formed by an iron catalyzed Haber-Weiss reaction. J. Biol. Chem. 260, 10099-10104. 

Although this reaction shows the formation of 02 +, it is also possible to add one electron to the 02 molecule to produce (),, the superoxide ion, or two electrons to form O/, the peroxide ion. In each case, the electrons are added to the antibonding 7r orbitals, which reduces the bond order from the value of 2 in the 02 molecule. For ()2 the bond order is 1.5, and it is only 1 for 022-, the peroxide ion. The 0-0 bond energy in the peroxide ion has a strength of only 142k) moT1 and, as expected, most peroxides are very reactive compounds. The superoxide ion is produced by the reaction... 

Other cationic surfactants such as TTAB, DTAB, DODAB, STAC, CEDAB, and DDDAB have been used in CL reactions with less frequency. Thus, tetradecyltrimethylammonium bromide [TTAB] has been used to increase the sensitivity of the method to determine Fe(II) and total Fe based on the catalytic action of Fe(II) in the oxidation of luminol with hydrogen peroxide in an alkaline medium [47], While other surfactants such as HTAB, hexadecylpiridinium bromide (HPB), Brij-35, and SDS do not enhance the CL intensity, TTAB shows a maximum enhancement at a concentration of 2.7 X 10 2 M (Fig. 11). At the same time it was found that the catalytic effect of Fe(II) is extremely efficient in the presence of citric acid. With regard to the mechanism of the reaction, it is thought that Fe(II) forms an anionic complex with citric acid, being later concentrated on the surface of the TTAB cationic micelle. The complex reacts with the hydrogen peroxide to form hydroxy radical or superoxide ion on the... 

Dioxygen oxidizes transition metal ions in the lower valence state generating the hydroxyperoxyl radicals or superoxide ions [155,156]. The thermodynamic characteristics of these reactions are presented in Table 10.6. It is seen that all cited reactions are endothermic, except for the reaction of the cuprous ion with 02. The reaction of the ferrous ion with dioxygen has a sufficiently low enthalpy (28 kJ mol 3). 

The reaction proceeds as a chain process involving the peroxyl radical and superoxide ion [284],... 

Superoxide dismutase enzymes are functional dimers of molecular weight (Mr) of approximately 32 kDa. The enzymes contain one copper ion and one zinc ion per subunit. Superoxide dismutase (SOD) metalloenzymes function to disproportionate the biologically harmful superoxide ion-radical according to the following reaction ... 

The authors conclude that superoxide ion probably binds in a similar fashion to the azide and that conserved water ligands in the enzyme structure both hydrogen-bond with and help guide the substrates toward the copper ion. If this is the case, then superoxide binds directly to Cu(II) (inner-sphere electron transfer) in the following reaction ... 

In order to rationalize the complex reaction mixtures in these slurry reactions the authors suggested that irradiations of the oxygen CT complexes resulted in simultaneous formation of an epoxide and dioxetane36 (Fig. 34). The epoxide products were isolated only when pyridine was co-included in the zeolite during the reaction. Collapse of the 1,1-diarylethylene radical cation superoxide ion pair provides a reasonable explanation for the formation of the dioxetane, however, epoxide formation is more difficult to rationalize. However, we do point out that photochemical formation of oxygen atoms has previously been observed in other systems.141 All the other products were formed either thermally or photochemically from these two primary photoproducts (Fig. 34). The thermal (acid catalyzed) formation of 1,1-diphenylacetaldehyde from the epoxide during photooxygenation of 30 (Fig. 34) was independently verified by addition of an authentic sample of the epoxide to NaY. The formation of diphenylmethane in the reaction of 30 but not 31 is also consistent with the well-established facile (at 254 nm but not 366 or 420 nm) Norrish Type I... 

Trace amounts of Cu(II) were reported to catalyze the oxidation of I-to I2 (156) and the phosphinate ion (H2P02) to peroxodiphosphate ion (PDP), which could be present as P20g, HP20 or H2P20f (757). Individual kinetic traces showed some unusual patterns in these reactions, such as the variation between first- and zeroth-order kinetics with respect to the formation of I2 under very similar conditions, or an autocatalytic feature in the concentration profiles of PDP, but these events were not studied in detail. The catalytic effect was interpreted in terms of a Cu(II) / Cu(I) redox cycle and the superoxide ion radical,... 

Reactions of 02 with Alkanes and Alkenes. When compared with 0, the superoxide ion is a much less reactive species. Since the 02 is thermally stable up to -175°C, stoichiometric reactions must be carried out at 175°C or lower temperatures (12). Methane is essentially unreactive with 02 at 175°C, and the reaction with ethylene and propane is slow. Essentially all of the 02 ions re-... 

Alkanes—Continued reactions—Continued with ozonide ions, 135 with superoxide ions, 134-35 role of oxygen ions in oxidation. 138-41 Alkenes, reactions with oxygen ions, 134 with ozonide ions, 135 with superoxide ions, 134-35 Aluminosilicate gels, alkali cations, 241... 

Really, as illustrated in Scheme 5, the irreversible oxidation of these oxygenated complexes can involve either a one-electron or a two-electron process. This depends upon the fact that the reaction of the oxygenated complex to regenerate the non-oxygenated complex can proceed through the release of a superoxide ion or an oxygen molecule. 

The standard potential of the 02/02 pair is equal to -0.15 V in water and -0.60 V in DMF. Usually, dioxygen easily captures two electrons in the stepwise reaction O2 + e —> O2 , then O2 + e 02 . In DMSO, dioxygen reductions into the superoxide ion and then into the dioxygen dianion are characterized by Ey2 = -0.5 V and Ey = -1.5 V in regard to the saturated calomel electrode (Sawyer and Gibian 1979). The superoxide ion occupies an intermediate position in the following redox triad O2 —> 02 —> In accordance with such a position, the superoxide ion... 

The reaction of 1-hydroxy- or 1-aminonaphthoquinone with O2 shows a significant feature of the superoxide ion formation. The superoxide ion forms a van der Waals complex with another product of this reaction, a semiquinone. Hydrogen bonds are formed between Oj" and the OH and NH2 groups of the corresponding semiquinone. As a result, the reaction equilibrium is shifted to the right (Liwo et al. 1997). 

If HB is a weak acid, this reaction is rather slow, but it nevertheless takes place. Substances that are unable to react with O2 can also be involved when the solvent-reactant mixtures contain water or other proton donor compounds, even in traces. Thus, benzaldehyde is absolutely resistant to the action of the superoxide ion. However, benzaldehyde transforms into benzylic alcohol and benzoic acid on the action of O2 in the presence of moisture. Sawyer and Gibian (1979) described the following superoxide variant of the Cannizzaro reaction 202 + H2O —>62 + HOO + OH and 2PhCHO + OH + H2O PhCOOH + PhCH20H. 

Proton-containing admixtures in a solvent or in benzaldehyde can act like water. The superoxide ion abstracts such labile proton and generates the HOO base. The base in its turn abstracts proton from a solvent, for example, AN. If benzaldehyde is present, it is converted into cinnamyl nitrile according to the following simple reactions ... 

Thus, in the presence of water or other proton sources, the O2 ion forms HOO —the strong base. Therefore, many reactions that are ascribed to the superoxide ion are actually reactions with proton donors. These reactions produce effective oxidants (O2 and HOO ) and strong bases (HOO, OH , or B ). This route of base generation finds its applications in synthetic practice. Thus, ethyl... 

As noted earlier, the superoxide ion reacts with effective electron acceptors. It is a one-electron reductant of moderate strength. However, the superoxide ion can act as a nucleophile if a substrate has a decreased electron affinity. For instance, alkyl halides react with the ion O2 RCH2OO -h HaE. This reaction initiates the next ones RCH2OO ... 

The reaction of superoxide ion with carbon tetrachloride is important for olefin epoxidations. This reaction includes the formation of the trichloromethyl peroxide radical Oj" + CCI4 —> Cl + CI3COO. The trichloromethyl peroxide radicals formed oxidize electron-rich olefins. The latter gives the corresponding epoxides. This peroxide radical is a stronger oxidizing agent than the superoxide ion itself (Yamamoto et al. 1986). 

---