Reactions of Superoxide Ion with Organic H Acids

The O2 ion in a solution promotes proton abstraction from a substrate or a solvent. This results in the formation of organic bases, which are conjugated with the appropriate H acids. All H acids with a pX value lower than 23 can take part in such proton transfers (Sawyer and Gibian 1979). For this reason, even organic acids (HB), which are weaker than water, enter the exothermic reaction, namely, HB -I- 2O2 — 02 + HOO + B.  

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  

The treatment of benzaldehyde with potassium hydroxide in AN results in the formation of the same product, that is, cynnamyl nitrile (Sawyer and Gibian 1979). 

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 

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