Addition reaction with organic molecules

In reactions with organic molecules e q reacts as nucleophilic reagent it attacks molecules with low-lying molecular orbital, like aromatic hydrocarbons, conjugated olefinic molecules, carboxyl compounds, and halogenated hydrocarbons (Swallow 1982 Buxton 1982, 1987 Buxton et al. 1988). In the latter case, addition is usually followed by halide ion elimination, so the reaction can be considered as a dissociative electron capture. For instance, the reaction with chlorobenzene yields phenyl radical and chloride ion... 

The 02 ion appears to play an important role in a number of photooxidation reactions (see Section VI,C) for example, the photo-oxidation of alkenes over TiOz. However, it seems likely that OJ is not, in many cases, active in the oxidation step but further conversion occurs to give a mononuclear species, not detected directly, which then oxidizes the adsorbed hydrocarbons. Photo-oxidation of lattice oxygen in the M=0 systems (e.g., V2Os supported on PVG) gives rise to an excited charge transfer state such as V4 + -0 . This excited state can react as O- either by addition to a reactant molecule or by an abstraction reaction (see Section V of Ref. /). In the presence of oxygen, 03 is formed which then reacts further with organic molecules. 

The Michael addition mechanism, whereby sulfur nucleophiles react with organic molecules containing activated unsaturated bonds, is probably a major pathway for organosulfur formation in marine sediments. In reducing sediments, where environmental factors can result in incomplete oxidation of sulfide (e.g. intertidal sediments), bisulfide (HS ) as well as polysulfide ions (S 2 ) are probably the major sulnir nucleophiles. Kinetic studies of reactions of these nucleophiles with simple molecules containing activated unsaturated bonds (acrylic acid, acrylonitrile) indicate that polysulfide ions are more reactive than bisulfide. These results are in agreement with some previous studies (30) as well as frontier molecular orbital considerations. Studies on pH variation indicate that the speciation of reactants influences reaction rates. In seawater medium, which resembles pore water constitution, acrylic acid reacts with HS at a lower rate relative to acrylonitrile because of the reduced electrophilicity of the acrylate ion at seawater pH. 

In addition, the hydrated electron acts as a nucleophile, especially with organic molecules that contain halogen atoms (Eq. 6-16). This reaction results in rapid elimination of a halide ion from the initially formed negatively charged organic species. The reaction of Eq. 6-16 is of special interest for the degradation of per-halogenated saturated hydrocarbons that are usually not affected by hydroxyl radicals (Sun et al, 2000). 

In Chapter 11 we continue our focus on organic molecules with electron-rich functional groups by examining alkynes, compounds that contain a carbon-carbon triple bond. Like alkenes, alkynes are nucleophiles with easily broken n bonds, and as such, they undergo addition reactions with electrophilic reagents. 

Simple alkyl azides are quite labile even at room temperature and have a tendency to detonate on rapid heating for these reasons, the majority of kinetic studies have been confined to the solution phase. As with azocompounds, the common nitrogen elimination reaction is the consequence of the relative stability of the resulting, divalent RN radical, called a nitrene, and the high heat of formation of the N2 molecule. In some cases, particularly in the thermolysis of aryl azides, Nj elimination follows a concerted path nevertheless, nitrene formation is of more common occurrence in both the photolytic and thermal decompositions. Decomposition and addition reactions of organic azides have been recently reviewed . 

As an odd-electron molecule, many of the reactions of nitrogen dioxide are typical of free radicals. This applies particularly to its association with atoms such as, H, F, and Cl or other radicals such as, the OH, NO, alkyl, and alkoxy radicals its addition reactions with unsaturated systems such as, olefins, acetylenes, and aromatic compounds, and its hydrogen abstraction reactions. The ability of the NO2 free radical to abstract hydrogen from an organic molecule ... 

Since it is unanimously agreed that MTBE is eUminated via OH radicals, many studies have been performed in order to elucidate the mechanistic pathway of the conversion. OH radicals react with organic molecules by the abstraction of hydrogen from C - H or O - H bonds, via hydroxyl group addition to unsaturated carbon bonds or the interaction with N-, P-, and S-containing bonds [32]. Since in the MTBE molecule no unsaturated carbon bonds and no N-, P-, or S-atoms are present the initial reaction has to concentrate on the abstraction of H atoms or the cleavage of the C - 0 bond. 

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