By Electrooxidation

Other recovery methods have been used (10). These include leaching ores and concentrates using sodium sulfide [1313-82-2] and sodium hydroxide [1310-73-2] and subsequentiy precipitating with aluminum [7429-90-3], or by electrolysis (11). In another process, the mercury in the ore is dissolved by a sodium hypochlorite [7681-52-9] solution, the mercury-laden solution is then passed through activated carbon [7440-44-0] to absorb the mercury, and the activated carbon heated to produce mercury metal. Mercury can be extracted from cinnabar by electrooxidation (12,13). 

Menke EJ, Brown MA, Li Q, Hemminger JC, Penner RM (2006) Bismuth telluride (Bi2Te3) nanowires Synthesis by cyclic electrodeposition/stripping, thinning by electrooxidation, and electrical power generation. Langmuir 22 10564-10574... 

A substrate containing an amine carboxylate moiety is converted in an electrolyte solution in the presence of a strong acid to a cationic intermediate, an N-acyliminium cation, by electrooxidative reaction. This species is immediately reacted with an allylsilane [66, 67]. By nucleophilic reachon, C-C bond formahon is achieved. 

Nickel(III) xanthates, Ni(S2COR)3, with R = Me, Et, Pr, z-Pr, Bu, z-Bu, sec-Bu, can be quantitatively generated in acetonitrile solution by electrooxidation of anionic [Ni(S2COR)3] or by oxidative addition of ethyldixanthogen, [EtOC(S)S]2 to Ni(S2COEt)2. Solutions of Ni(S2COR)3 readily disproportionate into Ni(S2COEt)2 and [EtOC(S)S]2.240... 

Synthesis of Poly(phenylene Oxides) by Electrooxidative Polymerization of Phenols... 

Electrochemical epoxidation of olefins has been developed for the production of ethylene and propylene oxides in aqueous sodium chloride or bromide solution. However, associated with these electrolyses are difficulties in achieving product selectivity as well as in obtaining high yields of the epoxides. Recently, a regiose-lective )-epoxidation of polyisoprenoids (23) to (24), promoted by electrooxidation in an MeCN/THF/H20-NaBr-(Pt) system, has been achieved (Scheme 10) [52]. 

A spirolactone 23 was prepared by electrooxidation of /V-carbomethoxy-tyrosine (63JA3702). 

After Little s proposal, many researchers have pursued such an exciting system in vain. Even metallic behavior was rarely seen in doped organic polymers, gels, and actuators. As mentioned in Sect. 3.4.4, MCso with linearly polymerized Ceo" exhibited one-dimensional (M = Rb, Cs) or three-dimensional (M = K) metallic behavior [144]. Recently a doped poly aniline was reported to exhibit a metallic temperature dependence for a crystalline polymer chemical oxidation of monomers grew crystallite polyaniline [329] early doping studies on polypyrrole (PFg) and poly(3,4-ethylene-dioxythiophene)X (X = PFg, BF4, and CF3SO3) prepared by electrooxidation at low temperatures also showed a metallic temperature dependence below 10-20 K (Scheme 16) [330, 331]. 

Sakata M, Yoshida Y, Maesato M, Saito G, Matsumoto K, Hagiwara R (2006) Preparation of superconducting (TMTSF)2NbF6 by electrooxidation of TMTSF using ionic liquid as electrolyte. Mol Cryst Liq Cryst 452 103-112... 

Thus, Semmelhack et al.8 in 1983 published the oxidation of alcohols by an oxoammonium salt, generated by electrooxidation of catalytic TEMPO and, in 1984, Semmelhack et al.9 published a similar oxidation of alcohols, in which catalytic TEMPO is oxidized by Cu (II), which itself can be used in catalytic quantities, being generated by the oxidation of catalytic Cu (I) by excess of gaseous oxygen. 

An oxoammonium salt operating as a primary oxidant is generated by oxidation of catalytic TEMPO with Br2, which, in turn, is formed by electrooxidation of bromide anion. The formation of a dimeric ester side-compound is minimized increasing the quantity of TEMPO. 

Debenzylation of Ar-benzyl-6e/a-lactams 41 has been achieved by electrooxidative methoxylation of 41 at the benzylic position followed by hydrolysis with p-toluene-sulfonic acid in acetone 27>. For example, the electrolysis of A-benzyl-3-methylene-6e/fl-lactam 41 (R = OMe) in an MeOH E NClC —fPt) system in an undivided cell forms iV-methoxybenzyl-3-methylene-6efa-lactam 42 (R = MeO) in 54% yield (Scheme 2-14). The debenzylation of 42 is carried out on treatment with p-toluene-sulfonic acid in aqueous acetone to give 3-methylene-6e/a-lactam 43 in 50% yield. 

Yamamoto K., Kimihisa A., Asada T., Nishide H., Tsuchida E. (1988) Preparation of Poly(/ -phcnylcne) by Electrooxidative Polymerization in Acid Media. Bull Chem Soc Jap. 61, 5,1731-1734. 

Poly(oxy-1,4-phenylene) is obtained by electrooxidative polymerization of / -bromo-phenol in aqueous NaOH solution. The yield increases when aqueous NaOH is replaced by aqueous KOH or when the reaction is conducted at higher temperature. In contrast, p-chlorophenol electrooxidatively dimerizes to give the biologically and pharmacologically important dioxin, 2,7-dichlorodibenzo[, ][l,4]dioxine254. In an effort to find protective chemical coatings, electrooxidative polymerization of ra-chlorophenol and ra-bromophenol was observed255. 

Figure 3-22 Resonance Raman spectra of 0=Fe(IV)(TMP) (top trace) and its 180 isotope analogue (bottom trace), generated at -40°C by electrooxidation of Fe(III)(TMP)(OH) at 1.2V in CH2CI2 containing OFI and 18OH, respectively. Both spectra were obtained in situ via backscattering from the low-temperature Raman spectroelectrochemical cell using 406.7 nm excitation ( 50mW) and 8cm slit widths. (Reproduced with permission from Ref. 74. Copyright 1988 John Wiley Sons, Ltd.)...

Further investigations on the field of oxidative bond cleavage even made single bonds accessible. Thus, biaryls 10 and 11 were similarly obtained by electrooxidation of 9,10-dihydrophenanthrene. Moreover, the cleaving reaction of benzylic carbons was also exploited in the synthesis p-tert-butylbenzaldehyde dimethyl acetale (3) starting from l,2-di-(p-ferf-butylphenyl)ethane (4, 1,2-DPTE) (Fig. 5.8) (Zollinger et al. 2004b). 

Some homoleptic unsymmetrical (dmit/mnt, dmit/tdas) dithiolene nickel complex-based D-A compounds with D = TTF and EDT-TTF also exhibit metal-like conductivity (see Table I) (101). Their molecular structure is shown in Scheme 3. The unsymmetrical tetraalkylammonium salts [MLjLJ- (M = Ni, Pd, Pt) have been prepared by ligand exchange reaction between tetraalkylammonium salts of MLj and ML21 (128, 129) and the D-A compounds have been synthesized by electrooxidation. Among these complexes, only the Ni derivatives exhibit metallic-like properties, namely, TTF[Ni(dmit)(mnt)] (metallic down to --30 K), a-EDT-TTF[Ni(dmit)(mnt)] (metallic down to 30 K), TTF[Ni(dmit)(tdas)] (metallic down to 4.2 K), and EDT-TTF[Ni(dmit)(tdas)] (metallic down to --50 K) (see Table I). The complex ot-EDT-TTF-[Ni(dmit)(mnt)J is isostructural (130) to a-EDT-TTF[Ni(dmit)2)] [ambient pressure superconductor, Section II.B.2 (124)]. Under pressure, conductivity measurements up to 18 kbar show a monotonous decrease of the resistivity but do not reveal any superconducting transition (101). 

Not only methyl groups but practically any other alkyl groups attached to aromatic rings are oxidized to carboxyls by sufficiently strong oxidants, such as nitric acid [460, 461, 462, 463, 464, 891], chromic acid and its derivatives [550, 551, 624, 633, 634, 1129, 1130], and potassium permanganate [503, 841, 880, 881, 882, 883, 1131]. Occasionally, such oxidations have been effected by other reagents, such as ozone [68], sulfomonoperacid (Oxone) [205], sodium hypochlorite [696], and nickel dioxide [933], or by electrooxidation [117] (equation 181). 

Homologues of pyridine are converted into the corresponding pyri-dinecarboxylic acids by electrooxidation [117], by oxidation with dilute nitric acid [462], or by treatment with potassium permanganate [503, 555] (equation 187). 

The formation of grafted films on carbon electrode surfaces is attained by electrooxidation of arylacetates under Kolbe electrolysis conditions [64]. 

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. 

Figure 11.4 Potentiostatic deposition of polyfluorene (octylthiophene) film (PFDOBT-HH) onto a Pt wire by electrooxidation of a 0.002 M solution of 2,7-bis(4-octylthien-2-yl)-fluoren-9-one in 0.25 M TEABF4/CH2CI2.

Radical cation salts of 69 were prepared by electrooxidation. The stoichiometries of two of these salts which formed crystals suitable for X-ray crystallographic analysis are (69)3(PF6)2 and (69)2I3. The crystal structure determination show that these species consist of segregated stacks of donors and acceptors. 

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