Ethanol, electron donor

The anaerobic dechlorination of hexachlorobenzene has been described in anaerobic mixed cultures supplemented with electron donors including lactate, ethanol, or glucose (Holliger et al. 1992) successive and partial dechlorination produced 1,2,4- and 1,3,5-trichlorobenzenes, while the 1,2,3-trichlorobenzene was further dechlorinated. The partial dechlorination of 1,2,3,4-tetra-, 1,2,3,5-tetra-, and pentachlorobenzene has been examined in a methanogenic mixed culture using lactate as electron donor (Middeldorp et al. 1997), and sterile Rhine River sand was needed to maintain dechlorination activity for unresolved reasons. 

Simultaneously, an electron donor, i.e., water or ethanol, is oxidized by the holes generated in the valence band hff) (Equation (3)). 

The first bipolar axis (DMSO/ethanol) accounts for the contrast between compounds with NO2 substitutions and those without. Compounds with a NO2 substituent systematically obtain higher scores on this bipolar axis than others. The second bipolar axis (methylenedichloride/ethanol) seems to produce an order of the substituents according to their electronic properties. To emphasize this point we have reproduced the log double-centered biplot again in Fig. 31.10. The dashed line near the middle separates the class of NO2 substituted chalcones from the other compounds. Further, we have joined substituents by line segments according to the sequence CF3, F, H, methyl, ethyl, I -propyl, t-butyl, methoxy, phenyl and di-methylamine. The electronic properties of these substituents vary progressively from electron acceptors to electron donors [ 11 ] in accordance with their scores on the second bipolar axis. 

Since anaerobic azo dye reduction is an oxidation-reduction reaction, a liable electron donor is essential to achieve effective color removal rates. It is known that most of the bond reductions occurred during active bacterial growth [48], Therefore, anaerobic azo dye reduction is extremely depended on the type of primary electron donor. It was reported that ethanol, glucose, H2/CO2, and formate are effective electron donors contrarily, acetate and other volatile fatty acids are normally known as poor electron donors [42, 49, 50]. So far, because of the substrate itself or the microorganisms involved, with some primary substrates better color removal rates have been obtained, but with others no effective decolorization have been observed [31]. Electron donor concentration is also important to achieve... 

For in situ metal bioprecipitation (ISBP), sulphate-reducing bacteria are provided with electron donors such as molasses, lactate, HRC (Koenigsberg et al., 2002), MRC (Koenigsberg, 2002), ethanol and/or other carbon sources. The bacteria oxidize the electron donor and transfer... 

The classical type A enzymes show marked differences in their abilities to oxidize two-electron donors. All the enzymes initially examined, whether eukaryotic or prokaryotic in origin, were members of clade III. These are rather effective as two-electron peroxidases. But the oxidations of ethanol and formate by the paradigmatic clade II enzyme from E. coli, HPII, are much slower. There is little information concerning the activity of type A enzymes in clade I. 

The reaction follows the consensus mechanism for aliphatic —H activation by oxyl-ferryl compounds (35) in which the first step is H-atom abstraction via TS1 to give a hydroxo-Fe(III) complex with a C-centered alkyl radical, labeled IN. This is followed by a rebound step via TS2 to give the final product, ethanol and the ferrous active site. Overall, this is a two-electron oxidation process where the bonding orbital serves as the electron donor and the H-atom abstraction is rate limiting. 

Laser flash photolysis has been performed with the halogenated derivatives in ethanol [374], Measurements of the triplet lifetimes as a function of dye concentration, laser power, and in the presence of electron donors allowed us to determine the rate constants collected in Table 17. 

Using the polymerized viologen bilayers, the viologen units were removed from the outer surface to which they were attached by ester linkages by reaction with imino ethanol. Photolysis with [Ru(bipy)3]2+ in the bulk phase then led to viologen cation radical formation on the inner surface. Presumably the iminoethanol groups acted as electron donors.342... 

Therefore, Fe(II) must be regenerated, for example by means of a Fe(III) reducing bacteria using ethanol as an electron donor [4] ... 

Ethanol, acetate and methanol are suitable electron donors for the reduction of Fe (III)EDTA to Fe(II)EDTA2. From experimental measurements [5], it appeared that the lag phase with methanol is substantially longer than with ethanol or acetate. Therefore, ethanol will be used as an electron donor. 

The first reaction is catalyzed by a mixed microbial population in which Bacillus azotoformans is the main denitrifying bacteria, and ethanol is the electron donor. Fe(II) is also regenerated from Fe(III) by means of reducing bacteria Dcfcrri-bacteres, using ethanol as the electron donor. These bacteria are found in the Veendam and Eerbeek sludges, as described in a previous section. 

Chromate(VI) has been reported to undergo reduction to Crv as a result of PET between its LMCT excited state and an external electron donor. In the study carried out for several aliphatic alcohols (methanol, ethanol, propan-2-ol, butan-1-ol, butan-2-ol, 2-methyl-propan-2-ol) two pathways of PET were identified one-electron transfer for intermolecular and two-electron transfer for intramolecular systems [96,97]. The intermolecular mechanism of the CrVI excited state quenching was also found for phenol or its derivatives [98], whereas in the case of an anion donor (such as oxalate) an effect of external cations was observed [99],... 

Henglein et al. have also found dimerization-products at ZnS-colloids, using 2-propanol as an electron donor and CO2 as an electron acceptor [190]. The dimerization produced was pinacol, and its formation has been interpreted by the same mechanism as given for the ethanol oxidation. Inoue et al. performed the same experiment, but did not find pinacol as a dimerization-product [191]. According to Muller et al., these differences may be due to slight differences in the preparation of the ZnS-colloids, which seems to be extremely critical [187]. 

Ogawa and coworkers have examined peptide y -strand mimics of the general type 24 (R = CH(CH3)2, n = 1-3), consisting of a ruthenium(II) polypyridyl electron donor tethered to a cobalt(III) pentammine electron acceptor by an polyvaline peptide chain [107]. A related parallel ) -sheet mimic has also been studied [108]. These compounds adopt the conformational properties found within the individual strands of a y -pleated sheet in both aqueous and methanol solutions. Emission lifetime measurements and HPLC product analyses suggest that the binuclear donor-acceptor compounds undergo photoinduced electron transfer. The values of et decrease with increasing donor acceptor distance according to y = 1.1 A, which is observed for electron transfers both in water at 298 K and in ethanol-... 

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