Distonic Stabilization of Anion-Radicals

Calculations (Hacker and Kasai 1993) in the framework of extended Hueckel theory found the LUMO of o-diazobenzoquinone to be mainly (up to 60%) localized at the N—N sector. The electronegativity of the o-carbonyl oxygen enhances the acceptor properties of the diazo group. Charge-spin separation is an understandable consequence of the situation. 

Theoretical studies on the m-benzyne anion led to the inference that it holds a pair of weakly interacting orbitals. One orbital contains the odd spin density, whereas another contains two electrons that are responsible for the negative charge of this species (Nash and Squires 1996). 

Also to be mentioned are the reactions of oxygen atom radical anions with organic substrates. These reactions were reviewed by Gronert (2001). For the reactivity of the atomic oxygen anion-radical, see Section 1.7.2. The atomic oxygen anion-radical reacts with benzene, tetramethylene ethane, or cyclopentadienylidene trimethylenemethane. The reactions consist in abstraction of H2 with the formation of H2O and the corresponding distonic anion-radicals as products. 

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