Two-electron reduction process

Au has recently received less attention than Pt as a supported catalyst because of its lower impact in PEMFC energy conversion technology, since the ORR is dominated by a two-electron reduction process, at what is a high overpotential, in acidic media. Nevertheless, it is an important oxygen reduction catalyst in alkaline media, and, in contrast to Pt, is oxide-free in the potential range where oxygen reduction occurs. 

All the [Ir(diphosphine)2]Cl complexes undergo a quasi-irreversible, two-electron reduction process followed by a chemical reaction. 

Consider, for example, the macrocyclic component 1 shown in Figure 5.1201 Such a species exhibits a two-electron reduction process, which corresponds to the simultaneous first reduction of the two equivalent bipyridinium units and, at a more negative potential, another two-electron process, which corresponds to the second reduction of such... 

Obtained in acetonitrile solution containing 0.2 mol dm-3 BuJNBF4 as supporting electrolyte. Solutions were 1 x 10-3 mol dm 3 in receptor and potentials were obtained with reference to an Ag/Ag electrode. Coulometric investigations suggest Et values represent a two-electron reduction process. b Cathodic shift in reduction potential produced by presence of anions (up to 4 equiv) added as their tetrabutylammonium salts. Precipitation of complex observed no CV could be obtained. Obtained in acetonitrile solution. 

The intrinsic instability of organocopper] 11) compounds is most probably associated with the redox properties of copper. Decomposition of organocopper] 11) compounds can occur by two different routes (i) formation of an organocopper]I) compound and an organic radical R" that can undergo further reactions, which formally represents a one-electron reduction process, and (ii) direct formation of R-R and Cu]0), which is formally a two-electron reduction process (reductive elimination cf Eqns. 1 and 2 in Scheme 1.3). 

In accordance with these experimental results, Wang et al. employed density functional theory calculations to comprehensively examine the possible reduction pathways for EC molecules in super-molecular structures Li+—(EC) [n = 1—5) and found that, thermodynamically, both one- and two-electron reductive processes are possible.A complete array of the possible reduction products from EC was listed in their paper considering the various competitive pathways, and they concluded that both (CH2OCO2-Li)2 and (CH2CH20C02Li)2 are the leading species in SEI, while minority species such as lithium alkox-ide, lithium carbide, and the inorganic Li2C03 coexist. 

Riboflavin undergoes a reversible and overall two-electron reduction process, in two overlapping one-electron steps. Both the final product and the one-electron reduction intermediate show acid base equlibria in the pH range 6-7. Thus a number of species take part in the redox process. Experimental investigation aimed at deriving the related equlibrium constants involves generation of the dihydro-... 

Higuera etal. [141] have studied reduction of 4-chloro-2,6-diisopropyloamino-5-triazine in acidic media up to pH 5, applying dc differential pulse polarogra-phy. In the recorded voltammograms, two main reduction peaks were observed, with a prepeak at less negative potentials, and a postpeak at more negative potentials, what points to adsorption of the compound at the electrode. Two main peaks corresponded to two-electron reduction process. 

In aqueous solution nobelium ions are most stable in the 2 oxidation state. In this oxidation state nobelium has a filled f-electron shell, 5f ", which is likely a major factor for its stability. The potential for the No(III)/No(II) couple has been calculated by Nugent et al. as 1.45 0.05 V [177]. A value of —1.4 to —1.5 V was determined by Silva and coauthors from experimental measurements [180]. David et al. have performed electrochemical amalgamation experiments for the reduction of No(II) to No(0) in aqueous acetate and citrate solutions [181]. They determined half-wave potentials of—1.709 0.006 V versus SCE in acetate and —1.780 0.004 V versus SCE in citrate. Their data was consistent with a reversible two-electron reduction process for which the data in acetate solution was taken as representative of a noncomplexing medium. The 1/2 value in acetate was converted to a value of —1.47 0.01 V versus SHE and subsequently used to derive a standard potential value of —2.49 0.06 V for the No(II)/No(0) couple. 

In an interesting recent work [36], a [EMIM][BF4] ionic Hquid with added [EMIM]Cl was successfuUy used to deposit Cd. It is formed on platinum, tungsten, and glassy carbon from CdCl4 in a quasireversible two-electron reduction process. This result is promising, as Te might perhaps also be deposited from such an ionic Hquid, thus possibly giving a system for direct CdTe electrodeposition. 

The interposed acid-base reactions which are most frequently observed, belong to two categories acid-base reactions following a one-electron transfer, as observed for numerous carbonyl compounds at higher pH values and for some hydrocarbons and proton-transfer reactions involving the product of a two-electron reduction process, usually carbanions. 

The first-formed intermediate (with an impaired electron) in combination with a second Lewis acid molecule has even greater electron affinity, and is reduced at a more positive potential to give a voltammogram that appears to be the result of an irreversible two-electron reduction process. In most cases it is an ECEC process in which each electron transfer (E part of the ECEC mechanism) to the Lewis acid (H30+) is reversible to give a product (H-) that forms a covalent bond with the substrate (H—Eh) (the C part of the mechanism). 

Aldehydes or ketones containing a cyclopropyl group adjacent to the carbonyl group can be converted to ring-opened carbonyl compounds by several different types of two-electron reduction processes. The most widely used method employs lithium metal in liquid ammonia as the reductant. The cyclopropyl ketone is usually dissolved in anhydrous diethyl ether and added to the blue metal-ammonia solution. Occasionally, the order of addition is reversed, and the lithium is added to a solution of the ketone in ammonia and diethyl ether. After a timed interval, the reduction is quenched by adding solid ammonium chloride to give a mixture of alcohols and ketones. This mixture is generally oxidized before isolation, with chromium(VI) oxide/pyridine or with sodium dichromate/sulfuric acid, to solely afford the ketone. 

Polarographic reduction of pyridazines and pyridazine 1,2-dioxide has been studied. " The polarographic behavior of pyridazine is typical of an overall two-electron reduction process. In alkaline solution it is reduced polarographically to 1,4-dihydropyridazine, but in acid solutions this compound gives an open-chain aminoimine. ... 

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