Hydrocarbons oxidation-reduction potentials

Hambrick, G.A., Delaune, R.D., Patrick, W.H., Jr. (1980) Effects of estuarine sediment, pH and oxidation-reduction potential on microbial hydrocarbon degradation. Appl. Environ. Microbiol. 40, 365-9. 

Owing to their lower oxidation-reduction potential, manganese(III) salts are weaker oxidants han cobalt(III) compounds. The reactivity of Mn(OAc)3 towards hydrocarbons is strongly nhanced by the presence of strong acids or bromides. 

From the studies on the chemical relationship between aromatic hydrocarbons and their quinones, the theory of the oxidation-reduction potential of quinones was proposed. 

The oxidation-reduction potential of the aromatic hydrocarbon-quinone system and its possible involvement in cigarette smoke was revisited some years later. Schmeltz et aL (3510) reported that cigarette smoke condensate (CSC) possessed reducingpropertiessufflcienttoreduce2,5-cyclohexadiene-l,4-dione (1,4-benzoquinone p-benzoquinone) to 1,4-benzenediol (hydroquinone). This CSC-induced reduction apparently did not occur with 9,10-anthracenedione (9,10-anthraquinone). 

The last general category—namely, the reaction of ozone with aromatic hydrocarbons, has received an enormous amount of attention by ozone chemists. Most of this attention has concerned rate and reactivity studies in an attempt to correlate these experimental quantities with some known parameters of the hydrocarbons. Several reactivity correlations have been proposed, including those with bond localization energy, atom localization energies, and oxidation-reduction potentials. This category is also represented by a paper in this section, in which a possible correlation between ozone reactivity and carcinogenicity of some polycyclic aromatic compounds is explored. 

Table 12.1. Oxidation and Reduction Potentials for Some Aromatic Hydrocarbons"...

Reduction of fullerenes to fullerides — Reversible electrochemical reduction of Ceo in anhydrous dimethylformamide/toluene mixtures at low temperatures leads to the air-sensitive coloured anions Qo" , ( = 1-6). The successive mid-point reduction potentials, 1/2, at -60°C are -0.82, -1.26, -1.82, -2.33, —2.89 and —3.34 V, respectively. Liquid NH3 solutions can also be used. " Ceo is thus a very strong oxidizing agent, its first reduction potential being at least 1 V more positive than those of polycyclic aromatic hydrocarbons. C70 can also be reversibly reduced and various ions up to... 

The delocalised radical formed by protonation of the radical-anion is more easily reduced than the starting arene. For some polycyclic aromatic hydrocarbons, the redox potential for this radical species can be determined using a cyclic voltammetry technique [10]. Reduction in dimethylformamide is carried out to the potential for formation of the dianion. The dianion undergoes rapid monoprotonation and on the reverse sweep at a fast scan rate, oxidation of the monoanion to the radical can be observed. The radical intermediate from pyrene has E° = -1.15 V vs. see in dimethylformamide compared to E° = -2.13 V vs. see for pyrene,... 

In situ redox manipulation (ISRM) is an in situ, groundwater remediation technology for manipulating the oxidation-reduction (redox) potential of an unconfined aquifer to immobilize inorganic contaminants (metals, inorganic ions, and radionuclides) and to destroy organic contaminants (primarily chlorinated hydrocarbons). 

V. D. Parker [56] obtained in acetonitrile the oxidation and reduction potentials (EQx and ERea) of alternant aromatic hydrocarbons (AAH) by cyclic voltammetry and examined how those potentials are related to the ionization potential (IP) and the electron affinity (EA) of the compounds (Table 8.8). As expected, he found linear relations of unit slopes between E0x and IP and between ERed and EA. Moreover, he found that E0x and ERed of each AAH was symmetrical with respect to a common potential MAAH (-0.31 V vs SCE). The values of (E0x-MAAH) and (ERed Maa ) are correlated with the values of IP and EA, obtained in the vacuum, by E0x-Maah = IP- +AGsV+ and ERed-MAAII = liA-r/t-AG, respectively (Fig. 8.21). Here, is the work function of graphite and equal to 4.34 eV, and AGj v+ and AG v are the differences in solvation energies for the 0/+1 and 0/-1 couples of AAH. Experimentally, AG°V+ and AG°V were almost equal, not depending on the species of AAH, and were equal to -1.94 eV in AN. 

Tab. 8.8 Oxidation potentials, reduction potentials, ionization potentials and electron affinities of alternant aromatic hydrocarbons (AAHs) ...

The properties of the lanthanide elements and their organometallic complexes described in the previous section explain in part why organo-met lic chemists in the past found lanthanide chemistry much less interesting than transition metal chemistry. The highly ionic, trivalent organolanthanide complexes appeared to have little potential to interact with the small-molecule substrates that provide such a rich chemistry for the transition metals neutral unsaturated hydrocarbons, H2, CO, phosphines, etc. The two-electron oxidation reduction cycles so important in catalytic transition metal chemistry in 18 16 electron complexes seemed... 

Aromatic hydrocarbons are called 7r bases because of their rather low ionization potentials. On the other hand, aromatic compounds containing a nitrogen atom possess lower MO energy than the parent hydrocarbons, and they show less electron-donating character or electron-accepting character. The mode of action of the herbicide paraquat 300 (1,1 -dimethyl-4,4 -bipyridinium salt) is thought to be connected with its reversible reduction-oxidation reactivity. The compounds with a lower level of activity possess higher reduction potentials, and their one-electron transfer is not quite quantitatively reversed. 

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