Anion radical reactions with organic

Radical, Anion, Anion-Radical Reactions with Organic Halides... 

In reactions with organic substrates, the 0 anion-radical is usually bad at electron transfer, but good at hydrogen atom abstraction. Because of the O spherical symmetry, its reactions are vulnerable by steric factors. Because of the O charged nature, its reactions with organic ions are of course susceptible to the effects of coulombic interaction also. Armstrong et al. (2004) showed that the predominant reactions with the anions of alanine and methylalanine proceed as follows ... 

The transition metal nature is not essential for this redox reaction. However, one of the reaction products, namely, the anion-radical 8O4 , can be complexed by a transition metal in a higher oxidation state. This leads to some stabilization of 8O4 and increases its reactive concentration. In other words, further reactions with organic substrates are facilitated (Fristad and Peterson 1984). 

Cuprous and ferrous salts are preferable. Sometimes, a transition metal salt is deliberately added to a mixtnre of a snbstrate and a persnlfate salt (Dobson et al. 1986). The free or metal-coordinated sulfate anion-radical reacts with an organic snbstrate, giving rise to a snbstrate cation-radical (Minisci et al. 1983, Itahara et al. 1988, Telo and Vieira 1997). The substrate cation-radical is often able to expel a proton and transform into the corresponding radical. The latter regenerates the initial metallic ion. The whole reaction becomes a catalytic one with respect to the metal. 

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. 

These radicals may initiate oxidation reactions with organic species. The reaction of S-containing radicals with organic moieties leading to CO2 formation is faster than the corresponding reaction with P-containing radicals. However, as previously indicated, these anionic species may be... 

Catalysts of the Ziegler-Natta type are applied widely to the anionic polymerization of olefins and dienes. Polar monomers deactivate the system and cannot be copolymerized with olefins. J. L. Jezl and coworkers discovered that the living chains from an anionic polymerization can be converted to free radicals by the reaction with organic peroxides and thus permit the formation of block copolymers with polar vinyl monomers. In this novel technique of combined anionic-free radical polymerization, they are able to produce block copolymers of most olefins, such as alkylene, propylene, styrene, or butadiene with polar vinyl monomers, such as acrylonitrile or vinyl pyridine. 

Figure 4, Correlations of anion, radical, and radical anion reactions with organic halides and the halide effect...

The reaction of bis(benzene)vanadium [12129-72-5] with TCNE affords an insoluble amorphous black soHd that exhibits field-dependent magnetization and hysteresis at room temperature, an organic-based magnet (12). The anion radical is quite stable in the soHd state. It is paramagnetic, and its intense electron paramagnetic resonance (epr) spectmm has nine principal lines with the intensity ratios expected for four equivalent N nuclei (13) and may be used as an internal reference in epr work (see Magnetic spin resonance). 

The attachment of an electron to an organic acceptor generates an umpolung anion radical that undergoes a variety of rapid unimolecular decompositions such as fragmentation, cyclization, rearrangement, etc., as well as bimolecular reactions with acids, electrophiles, electron acceptors, radicals, etc., as demonstrated by the following examples.135"137... 

A variety of organic anion radicals have been prepared in solution and characterized by spectroscopic (ESR and UV-vis) methods. Most often, the anion radicals are formed by reaction of electron-poor molecules with highly reducing alkali metal mirrors (such as sodium, potassium, and lithium) in anhydrous (oxygen-free) ethereal solvents (such as dimethoxyethane, tetrahy-... 

The kinetic advantage method, again using aromatic anion radicals as reference ET reagents, combined with the investigation of steric constraints at the electrophilic carbon centre, has also been used for examining the reaction of alkyl halides with several purely organic nucleophiles. The... 

Addition of 0- to double bonds and to aromatic systems was found to be quite slow. Simic et al. (1973) found that O- reacts with unsaturated aliphatic alcohols, especially by H-atom abstraction. As compared to O, HO reacts more rapidly (by two to three times) with the same compounds. In the case of 1,4-benzoquinone, the reaction with O consists of the hydrogen double abstraction and leads to the 2,3-dehydrobenzoquinone anion-radical (Davico et al. 1999, references therein). Christensen et al. (1973) found that 0- reacts with toluene in aqueous solution to form benzyl radical through an H-atom transfer process from the methyl group. Generally, the O anion-radical is a very strong H-atom abstractor, which can withdraw a proton even from organic dianions (Vieira et al. 1997). 

Carbon dioxide, CO2, is a typical component of the gaseous environment for reactions in air or in the presence of air traces. Therefore, both interactions between CO2 and organic ion-radicals as well as reactions of 62 with uncharged molecules of organic compounds should be considered. Interaction of CO2 with organic anion-radicals leads, as a rule, to carboxylic acids COj" anion-radicals are not formed. Even such a one-electron reductant as the superoxide ion (in aprotic medium) simply adds to carbon dioxide CO2 + O2 -> 00-C02. The additional product accepts an electron ... 

The reactions of 8O3 anion-radicals with organic and inorganic compounds have commanded considerable interest because of the role of these anion-radicals in grievous health and technological... 

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