Acetonitrile electrochemistry

Acetic add, frons-cyclohexanediaminetetra-metal complexes, 554 Acetic add, ethylenediaminetetra-in analysis, 522 masking, 558 metal complexes, 554 Acetic acid, iminodi-metal complexes, 554 Acetic acid, nitrilotri-metal complexes titrimetry, 554 Acetoacetic add ethyl ester bromination, 419 Acetone, acetyl-deprotonation metal complexes, 419 metal complexes reactions, 422 Acetone, selenoyl-liquid-liquid extraction, 544 Acetone, thenoyltrifluoro-liquid-liquid extraction, 544 Acetone, trifluorothenoyl-in analysis, 523 Acetonitrile electrochemistry in, 493 exchange reactions, 286 metal complexes hydrolysis, 428 Acetylacetone complexes, 22 liquid-liquid extraction, 543 Acetylacetone, hexafiuorothio-metal complexes gas chromatography, 560 Acetylactone, trifluorothio-metal complexes gas chromatography, 560 Acetylation metal complexes, 421 Acetylenedicarboxylic add dimethyl ester cycloaddition reactions, 458 Acid alizarin black SN metallochromic indicator, 556 Actinoids... 

Acetamide [60-35-5] C2H NO, mol wt 59.07, is a white, odorless, hygroscopic soHd derived from acetic acid and ammonia. The stable crystalline habit is trigonal the metastable is orthorhombic. The melt is a solvent for organic substances it is used ia electrochemistry and organic synthesis. Pure acetamide has a bitter taste. Unknown impurities, possibly derived from acetonitrile, cause its mousy odor (1). It is found ia coal mine waste dumps (2). 

Acetonitrile and hydrogen cyanide are hy-products that may he recovered for sale. Acetonitrile (CH3CN) is a high polarity aprotic solvent used in DNA synthesizers, high performance liquid chromatography (HPLC), and electrochemistry. It is an important solvent for extracting butadiene from C4 streams. Table 8-1 shows the specifications of acrylonitrile, HCN, and acetonitrile. ... 

Figure 5. Cyclic voltammograms of (a) 2,5"" -di-methyl-a-hexathiophene and (b) poly(2,2 -bithio-phene) films in acetonitrile containing 0.1 M E NCIO 103 (Reprinted from G. Zotti, G. Schia-von, A. Berlin, and G. Pagani, Electrochemistry of end-ca )ed oligothienyls-new insights into the polymerization mechanism and the charge storage, conduction and capacitive properties of polythiophene, Synth. Met. 61 (1-2) 81-87, 1993, with kind permission from Elsevier Science S.A.)...

Of particular interest is an electrochemistry study on related Mn(CNR) complexes, and on several carbonyl species 154). The one-electron oxidation process in acetonitrile (Mn(CNR)6+ Mn(CNR)s +) is substantially... 

Frank SN, Bard AJ (1975) Semiconductor Electrodes. 11. Electrochemistry at n-type Ti02 electrodes in acetonitrile solutions. J Am Chem Soc 97 7427-7433... 

Re(bpy)(CO)3Cl-modified electrodes has not yet been explained. However, from the cyclic voltammograms of fac-Re(bpy)(CO)3Cl (Fig. 14) and from the intermediate complexes formed by electrolysis in acetonitrile in the presence and absence of C02, two different electrocatalytic pathways (Fig. 15) were suggested144 initial one-electron reduction of the catalyst at ca. -1.5 V versus SCE followed by the reduction of C02 to give CO and C03, and initial two-electron reduction of the catalyst at ca. -1.8 V to give CO with no C03. The electrochemistry of [Re(CO)3(dmbpy)Cl] (dmbpy = 4,4 -dimethyl-2,2 -bipyridine) was investigated145 to obtain mechanistic information on C02 reduction, and the catalytic reac-... 

The first indication that such O-coordinated (phenoxyl)metal complexes are stable and amenable to investigation by spectroscopy was obtained when the electrochemistry of the colorless, diamagnetic complexes [Mm(LBu2)], [Mm(LBuMet)] (M = Ga, Sc) containing three coordinated phenolates in the cis-position relative to each other was investigated in acetonitrile solutions (142). A representative structure of [Scm(LBuMet)] is shown in Fig. 12. 

The carbon-nitrile bond in cyanoalkanes is cleaved by reduction at very negative potentials. This is the route for decomposition of acetonitrile at tlie limit for its use as an aprotic solvent in electrochemistry [114, 115]. Preparative scale reduction of cyanoalkanes is best carried out in anhydrous ethylamine containing lithium chloride as supporting electrolyte and gives 60-80 % yields of the alkane plus cyanide ion. 

One of the early examples of the application of the SHG technique in electrochemistry, proving its high sensitivity, is the investigation of the sulfate monolayers adsorbed on pc-Ag electrodes [10]. Also, one should mention the paper by Gamp-bell and Gorn [11], who have evidenced that the SHG method is also applicable to studies in nonaqueous solutions, namely, to the investigations of hydrogen evolution in acetonitrile (AGN). 

Electrochemistry offers alternative routes to the preparation of active zinc for the Reformatsky reactions, for instance exploiting the cathodic reduction (—0.8 V v.v SCE) of ZnBr2 in acetonitrile containing Bu4N+BF4 as supporting electrolyte53. 

The electrochemistry of tetrazolium salts (220) in aqueous media was discussed in Part I. In a strictly aprotic medium 220 gives a reversible one-electron reduction to a radical with a lifetime longer than the time scale of CV.352 In moist acetonitrile the reaction becomes a two-electron reduction similar to that in aqueous, basic media a formazan (221) is formed... 

In nonaqueous solvents, nonprotonated species can be generated. Consequently, many electrochemical studies of organic compounds employ nonaqueous solvents such as acetonitrile, dimethylformamide, and dimethyl sulfoxide [53]. Electrochemistry in nonaqueous solvents is addressed in Chapters 15-18. 

Other low-temperature studies have been motivated by the desire to characterize and understand processes occurring in unusual media. For example, the use of liquid ammonia [8-10] and liquid sulfur dioxide [11-13] naturally requires reduced temperatures unless high pressures are used, as is done for electrochemistry in supercritical fluids [14]. Frozen media are interesting systems in terms of mass transport phenomena and microstructural effects. Examples include glasses of acetonitrile and acetone [15], frozen dimethyl sulfoxide solutions [16,17], and the solid electrolyte HC104 5.5 H20 [18-20]. 

It is clear that a variety of solvents commonly used in electrochemistry is available for low-temperature studies. Particularly noteworthy are the solvent mixture butyronitrile/ethyl chloride, which can be used down to about 100 K [25,47], and the inclusion of the low-polarity cosolvent, toluene, to enhance the solubility of a substrate that is insoluble in many polar solvents, in this case the fullerene, [50,51]. When low solution resistance is a priority and only moderately low temperatures are needed (above ca. -50°C), polar solvents such as acetonitrile and A Af-dimethylformamide are preferred. 

As we have pointed out previously, oxygen and water concentrations can be kept at extremely low levels with a properly maintained purification train. In fact, contamination by water is much more easily controlled in a dry box than on a vacuum line. This may result in part from the number of operations and manipulations necessary to use a vacuum line. The oxidation of the cation radical of thianthrene to the dication illustrates this point. The dication is very electrophilic and is rapidly attacked by any nucleophiles (e.g., water). The electrochemistry of the dication in solutions prepared in the dry box (with acetonitrile as the solvent purified as described earlier) is reversible if a little care is taken in preparing the solvent and in drying the glassware. It is more difficult to obtain such reversible behavior when solutions are prepared on a vacuum line. 

Frank, SN and Bard, A3, Semiconductor Electrodes. II. Electrochemistry at n-type TiO Electrodes in Acetonitrile Solutions, 3. Amer. Chem. Soc., 97, 7427, 1975. 

Dimethyl sulfoxide (Me2SO). The applications of Me2SO in electrochemistry have been thoroughly reviewed.93 It is a particularly useful solvent because it has a high dielectric constant and is sufficiently resistant to both oxidation and reduction to provide a fairly wide potential range. It is, however, not as resistant as acetonitrile or propylene carbonate to oxidation and these latter two solvents are preferred over Me2SO for this purpose. 

Since rans- RuVI(b)2(0)2]2+ are only stable in aqueous medium, their electrochemistry in aprotic solvent such as acetonitrile has not been investigated. 

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