Electrooxidation function

Shukla AK, Ravikumar MK, Roy A, Barman SR, Sarma DD, Arico AS, Antonucci V, Pino L, Giordano N. 1994. Electrooxidation of methanol in sulfuric-acid electrolyte on platinized-carbon electrodes with several functional-group characteristics. J Electrochem Soc 141 1517-1522. 

Another useful route to alkaloids involves the electrochemical oxidation of lactams (145) bearing functionality on nitrogen that can be used to intramolec-ularly capture an intermediate acyl im-minium ion (146). The concept is portrayed in Scheme 33 and is highlighted by the synthesis of alkaloids lupinine (150) and epilupinine (151) shown in Scheme 34 [60]. Thus, the electrooxidation of lactam (147) provided a 71% yield of ether (148). Subsequent treatment with titanium tetrachloride affected cyclization and afforded the [4.4.0] bicyclic adduct (149). Krapcho decarbomethoxylation followed by hydride reduction of both the... 

Success in indirect electrooxidation with a metal redox carrier depends on the choice of a metal ion (1) that is best suited for the desired functionalization (2) that is soluble in the electrolysis media in both the high and the low oxidation states (3) that is expected to undergo electrooxidative regeneration with high current efficiency as well as to react with the substrate in a high yield (4) that can be readily separated from the products ... 

While dicarboxylic acid-functional pyrroles have received only cursory attention in condensation polymerizations, other derivatives have been studied extensively. Pyrrole itself has been electrooxidatively polymerized (81CS145) to give a flexible conductive film, presumably containing poly(2,5-pyrrolediyl) units (23) as the main structural feature. The blue-black polymer obviously contains other functionality, as evidenced by elemental analysis and by the fact that it carries a partial positive charge, and it exhibits p-type conductivities approaching the metallic range (e.g. 100 fi-1 cm-1). The main utility of poly(pyrrole) (23) has been for the modification of electrode surfaces, although numerous other applications can be envisioned. 

The electrooxidation procedure has been used in the preparation of a key intermediate for the fi /-helminthosporal synthesis 93). Aromatic steroids have been functionalized by means of anodic substitution introducing nucleophiles in the benzylic position 94a) or at the aromatic nucleus 94b). 

Electrooxidation of halide salts is quite useful for the generation of reactive species of halogen atoms under mild conditions. Functionalization of alkenes involving the formation of halohydrins, 1,2-halides, a-halo ketones, epoxides, allylic halides and others has been achieved by electrochemical reactions and is well documented in the literature. On the other hand, electrogenerated carbenium ions can be captured by nucleophilic halide anions, providing a new route to halogenated compounds... 

Figure 10 presents the in situ SPAIRS spectra of CO electrooxidation recorded as a function of potential at a Pt E-TEK modified by Ru with a surface coverage close to 0.20 (RuEiec20%/Pt-C catalyst). (A) spectra are calculated with a reference spectrum taken at 0.1 V vs. RHE, in order to detect the appearance of the band located close to 2345 cm related to CO2 (B) spectra are calculated with reference spectrum at 0.95 V, in order to determine the absorption band located close to 2071 cm assigned to adsorbed COl on Pt (COL/Pt) ° ""° (C) spectra are calculated with reference spectrum at 0.5 V vs. RHE in order to make visible the absorption band related to COl adsorbed on Ru (COl/Ru) located close to 2025 cm-. "°... 

Narayanasamy, J., Anderson, A. (2003). Mechanism for the electrooxidation of carbon monoxide on platinum by HjO. Density functional theory calculation. /. Electroanalytical Chem. 554-555,35-40. 

Fig. 43 Methanol electrooxidation current densities as a function of ruthenium coverage at 0.56 V ( ) and at 0.38 V ( ) on the Pt(111)/Ru electrode. (Reprinted with permission from Ref. 147, Copyright 1998 by the American Chemical Society).

Current density expressions for hydrogen and CO oxidation, yf, and jco, are given in Eq. (32) as a function of anode potential Va referenced to a SHE corrected for local Nernstian potential shift associated with local values of pn2 different than 1. Note that the same overpotential is assumed at a given anodic potential for both Ha( s and COads electrooxidation. This means that both k and kfc describe the rate of the anodic process at 0 V RHE (and full surface coverage by the corresponding surface species). 

Other reference electrodes have been proposed for use in the nonaqueous solvents that are widely used in coordination chemistry. Their main advantage is that they allow one to work with a single solvent. Among these electrodes, the Ag+/Ag electrode is reversible in many solvents.4 Ag+ ions are introduced as salts, such as AgCl or AgBF4. However, the inner solution has to be refreshed due to the reactivity of Ag+. Another class consists of redox electrodes in which the two components are in solution, such as ferrocenium ion/ferrocene Fc+/Fc.5 Since the potential is dependent on the concentration ratio of the redox couple, this ratio must be kept constant. An attractive solution to prevent the use of a junction lies in the preparation of a functionalized-polymer coated electrode such as poly(vinylferrocene).6 The polymer is deposited by electrooxidation in its oxidized form, polyFc+, and then partially reduced to yield poly Fc+/Fc. Their use is limited by their relative stability in the different solvents. 

The modulation in the vibrational frequency of CO on Pt-Ru is attributed to the charge transfer from Ru to Pt, due to difference in work function that weakens the Ru-CO bond and strengthens the Pt-CO bond. The weaker bonding of Ru-CO on Pt-Ru makes CO more reactive here than on pure Ru, and accordingly, electrooxidation sets in earlier in the potential scale. On the other hand. 

Fig. 5. Activity of HF-treated (Cu,oo-xPdx) Zr67 amorphous alloys in formaldehyde and fromate ion electrooxidation as a function of palladium concentration [O, 0.3M H2CO , 0.3Af HCOONa (I.OAf NaOH, 0.3 V) (reference reversible hydrogen electrode), 303 K]. (Reprinted from Ref. 110 with permission of Elsevier Sequoia, S.A.)...

Of the primary alcohols, a number of studies have investigated the electro-oxidation characteristics of ethanol, 2-propanol, and butanol. There have been several reviews on the electro-oxidation of these molecules on Pt, Au, and Pt/Au alloys. A number of trends have been observed for the electrooxidation of primary alcohols, including (i) the rate of electro-oxidation is dependent upon the pH of the solution, with R being the electrocatalyst in acidic media, (ii) the reactivity of the alcohols is governed by the position of the functional group on the backbone (primary alcohols are more reactive than secondary compounds, and tertiary alcohols show little reactivity), (iii) for the primary and secondary alcohols the first step in the dissociative adsorption... 

Instrumentation. A cell design employing reticulated vitreous carbon as the working electrode material that enables both UV-Vis absorption and luminescence measurements has been described [47]. A thin-layer cell with a platinum working electrode has been developed [69]. The luminescence of the electrooxidation products of o-tolidine as a function of electrode potential was studied. A simplified flow cell design has been reported [70]. Luminescence spectra and fluorescence intensity for various aromatic compounds and their electrochemical and photochemical reaction products were observed as a function of flow rate, current and time after the potential step. In the latter study the electrooxidation of p-phenylenediamine (PPD) was examined. The cyclic voltammogram showed two oxidation peaks the first one is assumed to be caused by the formation of the radical cation according to... 

Z.Z. Zhu, Z. Wang, and H.L. Li, Functional multi-walled carbon nanotube/polyaniUne composite films as supports of platinum for formic acid electrooxidation Appl. Surf. Sci., 254, 2934-2940 (2008). 

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