Reactions of Superoxide Ion with Organic Electrophiles

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  

RCH200 + RCH2Hal - RCH2-OO-CH2R + HaE. Reactions of KO2 with optically active alkyl halides proceed with the configurational inversion. Moreover, the reactivity changes in the same order as that of the usual Sj. 2 reactions (primary secondary tertiary J Br Cl) (Sawyer and Gibian 1979). 

Alkyl tosylates and mesylates are cleaved on the action of KOj in DMSO and give rise to the corresponding alcohols. This reaction also proceeds with inversion of configuration at carbon atoms (Morkovnik and Okhlobystin 1979). Such process may be of importance in prostaglandin chemistry. 

Reactions of O2 with esters R C(0)0R also pass nucleophilic substitution as an initial step (Sawyer and Gibian 1979). Final products are acyl peroxides or carboxylic acids. The following set of equations explains the product formation  

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). 

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