Sulfonates electron acceptor

The radical anions of dialkyl sulfoxides (or sulfones) may be obtained by direct capture of electron during y-irradiation. It was shown that electron capture by several electron acceptors in the solid state gave anion adducts 27. It was concluded276 that these species are not properly described as radical anions but are genuine radicals which, formed in a solid state cavity, are unable to leave the site of the anions and exhibit a weak charge-transfer interaction which does not modify their conformation or reactivity appreciably, but only their ESR spectra. For hexadeuteriodimethyl sulfoxide in the solid state, electron capture gave this kind of adduct 278,28 (2H isotopic coupling 2.97 G is less than 3.58 G normally found for -CD3). 

Introduction of the phenylthio group onto the 5-carbon atom of alcohols can have valuable synthetic applications. 5-Phenylthio alcohols can be oxidized to the corresponding 5-sulfoxides and sulfones (with their versatile reactivities) or they can be deprotonated by strong base converting the 5-carbon atom to a nucleophilic species. Conversion of 5-phenylthio alcohols to the corresponding 5-carbonyl compounds can be achieved via halogenation followed by subsequent hydrolysis. In this way an inversion of the reactivity of the 5-carbon atom may be accomplished and it can react as an electron acceptor. 

Lie TJ, T Pitta, ER Leadbetter, W Godchaux, JR Leadbetter (1996) Sulfonates novel electron acceptors in anaerobic respiration. Arch Microbiol 166 204-210. 

Lie TJ, W Godchaux, JR Leadbetter (1999) Sulfonates as terminal electron acceptors for growth of sulfite-reducing bacteria (Desulfitobacterium spp.) and sulfate-reducing bacteria effects of inhibitors of sulfidogenesis. A / Environ Microbiol 65 4611-4617. 

The transport of toluene-4-sulfonate into Comamonas testosteroni has been examined (Locher et al. 1993), and rapid uptake required growth of the cells with toluene-4-sulfonate or 4-methylbenzoate. From the results of experiments with various inhibitors, it was concluded that a toluenesulfonate anion/proton symport system operates rather than transport driven by a difference in electrical potential (A (/), and uptake could not take place under anaerobic conditions unless an electron acceptor such as nitrate was present. 

The reductive lithiation of a-alkoxy phenylsulfides is a slow process (typically 0.5-1 h at -78°C) and lowering the LUMO of the electron acceptor by using, for example, an anomeric sulfone, leads to a much faster electron transfer [11]. Reductive lithiation of sulfone 22 is fast (less than 1 min) and leads to similar a-lithio reagents to those described above and Scheme 8 shows examples of simple a-C-2-deoxyglycosides 23 and 24 prepared by this protocol. The most interesting feature of anomeric sulfones is that alkylation prior to the reductive desulfonylation event is achievable. In this way, a one-pot four-step sequence... 

The excess negative charge located in the interior of metallic silver colloids could also be transferred to other electron acceptors, including methylviologen, nitrobenzene, nitropyridinium oxide, anthracene quinone sulfonic add, and potassium cyanohexaferrate(III)[506, 531], The efficiency and, indeed, the direction of electron transfer were found to depend on the position of the Fermi level of the surface-modified silver particles. For example, chemisorption of AgN to a silver particle is shown to result in a shift of the Fermi level to a more positive potential, as shown in the lower line in Fig. 84. 

Cytochrome 62 is stereospecific for l(- -)-lactate. It also oxidizes other a-hydroxymonocarboxylic acids at slow rates 80, 96). As electron acceptors ferricyanide, methylene blue, 2,6-dichloroindophenol, 1,2-naphthoquinone 4-sulfonate, and cytochrome c have been used. This wide acceptor specificity is characteristic of a number of flavoproteins, which are generally capable of reducing quinoid structures and ferric compounds 97). However, as will be seen below, cytochrome c is considered to be the physiological electron acceptor for the yeast L-lactate dehydrogenase. 

An especially clean example of electron transfer chemistry involving carbon-carbon multiple bonds as electron acceptors, i.e., proceeding via anion radicals is the cyclobutanation of phenyl vinyl sulfone induced by reduction at a mercury pool cathode (Scheme 76) [122]. 

Electron-transfer reactions in the Cyt/- PC P700 sequence may be illustrated by the informative experiments reported in 1980 by Haehnel, Propper and Krause". These authors used broken spinach chloroplasts treated with NH OH or DCMU to inactivate or block electron transfer from PS II in the sample. The buffer used was Tricine containing ascorbate, plus diaminodurene (DAD) or DCIP as the secondary electron donor system and 9,10-anthraquinone-2-sulfonate as the secondary electron acceptor. As shown in Fig. 5, a short blue flash elicits an instantaneous absorbance decrease due to P700 photooxidation, which is followed by a multi-phasic decay representing re-reduction of P700 by PC. Note that the initial portion near the flash was slightly tmncated by fluorescence interference. 

The role of the additive (e.g. HMPA, DMPU) in the process is to increase the reducing power of Sm(II) and is crucial since no elimination reaction is observed in its absence, unless a better single-electron acceptor aromatic sulfone, such as a fS-hydroxy imidazolyl sulfone is used (Eq. 54).102 The employment of imidazolyl sulfones increases the efficiency of the olefination process due to the absence of a retro-aldolization reaction and the change in the nature of the leaving group (probably HOSmI2). 

In a recent pubHcation, Alivisatos and co-workers reported the making of hybrid nanorods-polymer solar cells and their properties [122]. These solar cells were made by spin casting of a solution of both poly(3-hexylthiophene) (hole acceptor) and CdSe nanorods (electron acceptor) onto indium tin oxide glass substrates coated with poly(ethylene dioxythiophene) doped with polystyrene sulfonic acid and aluminum as a top contact. Nanorods have been used in composites so as to improve the carrier mobiHty. Indeed, the latter can be high for some inorganic semiconductors, but it is typically extremely low for conjugated polymers [123]. The use of the nanorods suppHes an interface for the charge transfer as well as a direct path for electrical transport. Also, because of their anisotropy, self-assembly of these nanorods is observed by electron microscopy. It shows... 

However maquettes for the design of redox proteins were proposed, based on a three helix bundle with a capping Co(III) (bipyridine)3 electron acceptor at the N-terminus and an electron donor at the C-terminus (199, 200). These proteins were tested for LRET. The a-helical percent was adjusted by addition of urea or trifluoroethanol (201, 202). Intriguingly, studies of one of the proteins (l6-mer-three helix bundle) shows a 2-fold higher LRET rate constant when the percent of helicity is 77% than when it is 0% (denatured in urea). However authors indicate that the kinetics is not a simple first-order one in the presence of urea. They interprete these data as coming from different donor-acceptor distances. The distribution of distances was determined by fluorescence lifetimes fit. Both when helicity is 0% or 77%, distributions peak around 18 A for the Ru(II) (16-mer)3-A (where A=5-((((2-acetyl)amino]ethyl)amino)-naphthalene-l sulfonic acid). Actually the distance appears 0.7A shorter for a-helix which is found consistent with the increased rate constant, by the authors. 

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