Properties electron acceptor

We postulated a reaction mechanism with participation of an aromatic radical cation which was formed by one electron transfer from an aromatic hydrocarbon to copper(II) chloride. Activated alumina has electron-acceptor properties, and formation of a radical cation of an aromatic hydrocarbon adsorbed on alumina has been observed by ESR (ref. 13). Therefore, it seemed to us that alumina as a support facilitates the generation of the radical cation of the aromatic hydrocarbon. 

Mairanovski, V. G., A. A. Engovatov et al. (1975). Electron-donor and electron-acceptor properties of carotenoids Electrochemical study of carotenes. J. Electroanal. Chem. 66 123-137. 

Since the values of for many organic acceptors are generally unobtainable (in organic solvents), an alternative measure of the electron-acceptor property is often based on the irreversible cathodic peak potential F (in cyclic voltammetry). Thus for a series of related compounds, Fig. 6 shows that the values of Fred are linearly related to gas-phase electron affinities (EA).70... 

Fig. 17 Comparison of the electron acceptor properties of JV-nitropyridinium cations (XPyNO ) as measured by their E% values in relationship to the thermodynamic acidities of the corresponding hydropyridinium cations (XPyH+) as evaluated by their pXa values. Reproduced with permission from Ref. 235a.

The products of the reactions of picryl chloride with isomeric 4- and 5-aminobenzofurazans in dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) were studied by means of nonaqueous potentiometric titration. The effect of the position of the furazan fragment in 4- and 5-picrylaminobenzofurazans on the NH acidity is considered. The electron-acceptor properties of the furazan fragment were evaluated via inclusion of the resulting data into the pK -cr correlation for 2,4,6-trinitrodiphenylamines <2005RJC933>. 

It is interesting to note that the increase in the ratio as a result of increasing the electron-acceptor property of the phosphines also resulted in a decrease in the production of the 1,2-addition product, 3-methyl-1,4-pentadiene (see Table X). No attempt has been undertaken to explain this observation. 

The UV/Vis spectra (Figure 3.2) of the chestnut brown solutions of the monoadducts CjqHR, particularly the intensive bands at = 213, 257 and 326 nm, are close to those of Cjq, demonstrating their electronic similarity [4]. The biggest changes in the spectra compared with Cjq appear in the visible region. The typical features of Cjq between X = 400 and 700 nm are lost, and a new and very characteristic band at X = 435 nm appears, which is independent of the nature of R. Also, the electrochemical properties of CjqHR are comparable with those of Cjq [5, 19]. The first three reversible reduction waves shift about 100 mV to more negative potentials. Therefore, the fullerene core in these monoadducts still exhibits remarkable electron-acceptor properties, which is one reason for almost the identical chemical reactivity compared with CgQ. 

Cycloaddition of sulfenes to a,)8-unsaturated sulfides that contain electron-donor substituents, such as alkyl and arylthio groups, has proved to be a valuable synthetic pathway for the production of thietane 1,1-dioxides. Methylsulfonylsulfene (84) is more reactive than the regular sulfenes because of the activating effect by the strong electron-acceptor properties of the sulfonyl group. If, in addition, a strong electron-donor group, such as the alkylamino function, is provided by the unsaturated sulfide molecule, the cycloaddition proceeds much more readily. 

One very convincing piece of evidence that the Silicon atom has very definite electron acceptor properties is the observation 30) that certain... 

The first two terms represent van der Waals interactions between the adsorbed SOC and the surface, which would apply to all SOC. The second two terms represent Lewis acid-base interactions, which can be important for compounds containing O, N, or aromatic rings, for example, the adsorption of alkyl ethers on the polar surface of quartz. The y coefficients (in mJ m 2) describe the surface properties, where yvdw is associated with its van der Waals interactions with adsorbing gases, y describes its electron-acceptor interactions, and y describes the electron-donor interactions of the surface. On the other hand, the properties of the adsorbing species are described by In pL for the van der Waals interactions and by the dimensionless parameters ft and which relate to the electron-donor and electron-acceptor properties (if any), respectively, of the adsorbing molecule. 

As mentioned before (Sect. 3.1) Newman developed tetranitrofluorenylidene oxamino-propionic acid (TAPA, 79) as a new agent for the resolution of hexahelicene. Its molecular structure, including a large moiety with strong electron acceptor properties, promised good complexing properties towards aromatic compounds like hexahelicene. 

At present, most studies on new photochemically active systems concentrate on poly-chromophoric, dendritic, supramolecular systems and novel materials. For example, theoretical calculations indicate that the development of related nanotubes will result in materials with excellent electron-acceptor properties and highly red-shifted bands in the near-IR region17. 

Finally, inspection of Table 3.2 shows also that there are cases in which Yu can be even smaller than 1. An example is a solution of diethylether in chloroform. Here, the solute is an electron donor (H-acceptor), while the chloroform solvent is an electron acceptor (H-donor). In this case, the solute and solvent both acquire additional inter-molecular interactions that were unavailable to them in their pure liquid forms. The monopolar diethylether (only vdW interactions in its pure liquid) can add polar interactions to its vdW attractions with the molecules of the monopolar chloroform solvent exhibiting a complementary electron acceptor property. 

Before we look at some other surfaces, we should briefly address the H-donor (electron acceptor) properties, HDsurf, of the mineral oxides discussed so far. As can be seen from Fig. 11.5b (data for mineral oxides) and Table 11.1, HDsurf values decrease with increasing RH and become more similar with increasing RH. Furthermore, between 30 and 90% RH the HDsurf values can also be estimated by linear interpolation. However, in contrast to the vdW parameter, at 90% RH this value is smaller than that of the bulk water surface. This may have to do with the orientation of the water molecules caused by the nearby solid surface, but an unambiguous explanation is still missing. Between 90 and 100% RH, when the thickness of the adsorbed water layer rapidly grows, one can anticipate that this difference disappears. 

Figure 1 j4 Diagrammatic rationalization of the better electron-acceptor properties of an excited state... 

Because of this difference in electron-donorand electron-acceptor properties, excited states have very different redox properties from those of related ground states. The effect is so marked that many photochemical processes begin with a complete transfer of an electron from (or to) an excited state (1.2), and the subsequent chemistry is that of radical cations and radical anions, species that are regarded as unusual in ground-state organic reactions. The importance of photochemical electron transfer is underlined by its extensive involvement in photobiological processes such as photosynthesis. 

Tests on Treated Catalysts. Electron Acceptor Properties. Samples (0.1 gram) of materials A and B were activated in turn by heating to 600° C in vacuo for 6 hours, cooled in desiccator, and transferred to... 

From a systematic study of bichromophoric compounds 97-99, the importance of substituents and solvent polarity in intramolecular deactivation processes of photoexcited anthracenes by nonconjugatively tethered, and spatially separated, aromatic ketones in their electronic ground state is apparent. For 97a-d, in which the electron acceptor properties of the aromatic ketone moiety have been varied by appropriate p-substitution of the phenyl ring (R is methoxy, H, phenyl, and acetyl, respectively), the longest-wavelength absorption maximum band lies at 388 nm, i.e., any ground state effects of substitution are not detectable by UV spectroscopy. Also, the fluorescence spectra of 97a-d in cyclohexane are all related to the absorption spectra by mirror symmetry. However, the fluorescence quantum yields for 97a-d in cyclohexane dramatically are substituent dependent (see Table 19), ranging from 0.20 for the methoxy derivative to 0.00059 for the acetyl compound [33,109],... 

In polar solvents such as chloroform, dichloromethane, acetone, and acetonitrile, the fluorescence quantum yields of 97a-d decrease by varying degrees (see Table 19). Moreover, in the case of the phenyl and acetyl derivatives 97c and 97d, the rather drastic decrease of the structured fluorescence from the locally excited anthracene is associated with the appearance of a structureless, red-shifted emission which is attributable to an intramolecular exciplex. For 97d, in which the electron acceptor properties of the aromatic carbonyl moiety are enhanced by p-acetyl substitution, exciplex emission is dominant even in toluene solution (see Figure 22). 

Radiolysis of vitreous aqueous solutions of H2S04 and NaOH is known to yield the anion radicals S04 and 0 which possess strong electron acceptor properties and are readily recorded by the characteristic EPR spectra [1, 2]. Reactions of electron transfer from FeS04 and AgN03 to S04, and from K4Fe(CN)6 to 0 at 77 and 4.2 K have been detected and investigated [3, 4]. 

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