Cathodic behavior

Many papers deal with both analytical determination and cathodic transformations of thiones (21). Thus, a four-electron reduction of OLTIPRAZ [4-methyl-5-(2-pyrazinyl)-l,2-dithiole-3-thione] produces several species that could account for the schistosomicidal activity of metabolites of the starting compound. The first two-electron reduction (in aqueous media) affords the scission of the S —S linkage and the thus formed dianion can be readily [197] alkylated by common alkyl halides. Let us note that the cathodic behavior of structure (21) was shown to be strongly influenced by the nature of substituents and particularly [198] by the electron-donating ability of Rh... 

With l,2-di(phenylthio)benzene (24), two successive two-electron steps [207] can be observed in aprotic DMF [E = —1.82 V and 2 =—2.11 V vs Ag/AgI 0.1 M / reference system). On the other hand, substitution by efficient electron-withdrawing groups might change dramatically the cathodic behavior of ArSR-type compounds. Apparently, the captodative character of substituents attached to the phenyl ring (see Structure 25) strongly... 

Several results concerning the electrochemical reactions at the Si/HF interface have been published. Some were focused on the cathodic processes, others on the anodic etching reaction, and the influence of various parameters, such as doping level, influence of light, surface structure or presence of redox reactants, was investigated. A synthetic picture of anodic and cathodic behavior of both p- and n-type Si substrate, in the simplest condition of a pure 5% HF aqueous solution, in the dark is presented (see Fig. 5). 

Cathodic behavior after the prolonged (up to 10 s) potentiostatic polarization in... 

Earlier studies on the electrochemical reduction of aldehydes and ketones have been summarized in several reviews1,29,45 the reader should refer to those reviews for background material to the discussion which follows. Nevertheless, a short outline of the cathodic behavior of these substances will be helpful. 

The search for such curved Tafel plots has yielded some well-documented examples where essentially straight Tafel lines are observed, even when slight curvature is predicted from eqn. (37). In particular, this is the case for proton reduction [73] and the outer-sphere reduction of some Cr(III) aquo complexes [34] at mercury electrodes over wide overpotential ranges (> 600 mV). However, the former reaction is not an outer-sphere process with symmetrical reactant and product parabolae to which eqn. (37) should apply, but rather involves the formation of an adsorbed hydrogen atom intermediate. The influence of such a mechanistic feature upon the rate-potential behavior is unclear even now [74]. The Cr(III)/Cr(II) aquo couple at mercury has also been examined over wide ranges of anodic as well as cathodic over-potentials [75]. In contrast to the cathodic behavior, marked... 

Because of its inexpensive nature and widespread use as a cathode in batteries, Mn02 has been extensively studied from the viewpoint of its physicochemical properties and its cathodic behavior. It has also attracted... 

The rheological phase reaction method offers a new and simple way to prepare compounds and materials. The prepared compounds LiCo YyMn2.x.y04 show excellent capacity and cycleability. The cathode behavior of the LiMn204 can be greatly improved by simultaneous doping of cobalt and yttrium, and our results on LiCo, YyMn2.x-y04 show that the composition with x=0.02, y=0.015 exhibits the best high current rate (IC) capacity up to 60 cycles. The compound after optimization may find potential application in practical lithium-ion cells. 

Selective cathodic reduction of pyridines is a process of great industrial significanee [171]. As an example, dimethyl pyridinedicarboxylates undergo a highly selective electroreduction in methanol by use of a divided cell. The product obtained depends on the position of the substituents. Thus, the 2,3- and 2,5-dicarboxylates give the 1,2-dihydropyridines whereas the 2,6-, 3,4- and 2,4-dicarboxylates the 1,4-dihydropyridines [172]. Many other ring reductions of azines (often with dimerization as a side-reaction, see Section 6.4.3) are discussed in electrochemistry texts and reviews [116]. Attempts have been made to rationalize the herbicidal properties of dipyridinium salts in terms of their cathodic behavior [173]. 

Two very important points about the cathodic behavior of need to be mentioned. First, Cgo anions appear to be stable on the voltammetric time scale, but when electrogenerated by controlled potential coulometry in solution, only the mono- through tetra-anions are stable [6b,6e]. Second, although neutral C o may be insoluble in solvents such as dimethylformamide (DMF), acetonitrile, or tetrahydrofuran (THF), its anions dissolve readily. Therefore, these anions can be generated from a suspension of Cgo [12]. 

Cathodic Behavior of Sulfur, Tellurium, and Selenium an Easy Way... 

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