Organic Carbonates as Solvents in Synthesis and Catalysis

Amine- and phosphine-borane adducts: new interest in old molecules.

The electron transfer reactions involving quinones, hydroquinones, and catechols are very important in many areas of chemistry, especially in biological systems. The therapeutic efficiency as well as toxicity of anthracycline anticancer drugs, a class of anthraquinones, is governed by their electrochemical properties. Other quinones serve as important functional moiety in various biological systems like electron-proton carriers in the respiratory chain and their involvement in photosynthetic electron flow systems. The present paper summarizes literatures on the reduction of quinones in different solvents under various conditions using different electrochemical methods. The influence of different reaction conditions including pH of the media, nature of supporting electrolytes, nature of other additives, intramolecular or intermolecular hydrogen bonding, ion pair formation, polarity of the solvents, stabilization of the semiquinone and quinone dianion, catalytic property, and adsorption at the electrode surface, are discussed and relationships between reaction conditions and products formed have been presented.

https://downloads.hindawi.com/journals/ijelc/2011/816202.pdf

Electrochemical Reduction of Quinones in Different Media: A Review

The electrochemical reduction of oxygen in two different room-temperature ionic liquids, 1-ethyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)imide ([EMIM][N(Tf)2]) and hexyltriethylammonium bis-((trifluoromethyl)sulfonyl)imide ([N6222][N(Tf)2]) was investigated by cyclic voltammetry at a gold microdisk electrode. Chronoamperometric measurements were made to determine the diffusion coefficient, D, and concentration, c, of the electroactive oxygen dissolved in the ionic liquid by fitting experimental transients to the Aoki model. [Aoki, K.; et al. J. Electroanal. Chem. 1981, 122, 19]. A theory and simulation designed for cyclic voltammetry at microdisk electrodes was then employed to determine the diffusion coefficient of the electrogenerated superoxide species, O2·-, as well as compute theoretical voltammograms to confirm the values of D and c for neutral oxygen obtained from the transients. As expected, the diffusion coefficient of the superoxide species was found to be smaller than that of the oxygen in both ionic liquids. The diffusion coefficients of O2 and O2·- in [N6222][N(Tf)2], however, differ by more than a factor of 30 (DO2 = 1.48 × 10-10 m2 s-1, DO2·- = 4.66 × 10-12 m2 s-1), whereas they fall within the same order of magnitude in [EMIM]-[N(Tf)2] (DO2 = 7.3 × 10-10 m2 s-1, DO2·- = 2.7 × 10-10 m2 s-1). This difference in [N6222][N(Tf)2] causes pronounced asymmetry in the concentration distributions of oxygen and superoxide, resulting in significant differences in the heights of the forward and back peaks in the cyclic voltammograms for the reduction of oxygen. This observation is most likely a result of the higher viscosity of [N6222][N(Tf)2] in comparison to [EMIM][N(Tf)2], due to the structural differences in cationic component.

Voltammetry of oxygen in the room-temperature ionic liquids 1-ethyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)imide and hexyltriethylammonium bis((trifluoromethyl)sulfonyl)imide: One-electron reduction to form superoxide. Steady-state and transient behavior in the same cyclic voltammogram resulting from widely different diffusion coefficients of oxygen and superoxide

This review focuses on the more significant contributions to the understanding and use of ion-selective electrodes (ISE's). There is a strong interest in this field as over 1400 articles and abstracts were found during the writing of this review which covers the period from January 1986 through December 1987. The major analytical and electrochemical journals were read and a hand search of Chemical Abstracts uncovered the remaining articles. Unlike previous fundamental reviews, this paper will not attempt to list all the pertinent papers on ISE's. Rather, the more interesting works and applications are covered to illustrate examples of the general trends and directions of ISE interests.

Ion-Selective Electrodes.

Effect of metal ions on the polarographic reduction of organic compounds in dipolar arrotic solvents

Polarographic reduction of quinoline and its derivatives in non-aqueous solvents

The solubility and polarographic behavior of dissolved oxygen have been investigated in air-saturated DMSO-water mixtures at 25°C and 45°C. The first oxygen wave, which corresponds to one-electron reduction to superoxide ions in water-poor DMSO solutions of 0.1 M Et4NClO4, changes to a two-electron process in the range of water content between 10 and 30% because of the protonation reaction due to water. The rate of protonation is potential-dependent. The rate also depends on the species and the concentrations of the supporting electrolytes. The temperature effect is small. Using the solubility and polarographic data obtained, the polarographic diffusion coefficients of oxygen in the mixed solvent have been calculated.

Polarographic Studies of Dissolved Oxygen in DMSO-Water Mixtures

Propylene carbonate: purification and tests for purity

The polarographic behavior of alkali metal ions in hexamethylphosphoramide (HMPA) has been found to be greatly influenced by the cations of the supporting electrolytes. With 0.05 M Et4NClO4 as the supporting electrolyte, cesium and rubidium ions give diffusion-controlled, reversible waves at−2.32 and −2.35 V, respectively, vs. the Ag/0.1 M AgClO4 electrode, but sodium and lithium ions are not reduced until the reduction of the supporting electrolyte (−3.1 V). The potassium ion gives a wave at −2.37 V with a limiting current controlled by the rate of the preceding process. In 0.05 M Bu4NClO4 solutions, the reduction wave of the potassium ion is diffusion-controlled, but that of the sodium ion is kinetic and is very small. The lithium ion is not reduced until −3.1 V. In 0.05 M LiClO4, even the sodium ion is reduced reversibly with E1⁄2 at −2.47 V, while the reduction of the lithium ion starts from −2.65 V. In mixed supporting electrolytes, the presence of the tetraethylammonium ion is the determining factor...

Kosuke Izutsu

Papers

Effect of metal ions on the polarographic reduction of organic compounds in dipolar arrotic solvents

Polarographic reduction of quinoline and its derivatives in non-aqueous solvents

Polarographic Studies of Dissolved Oxygen in DMSO-Water Mixtures

Propylene carbonate: purification and tests for purity

Polarographic Investigation of Alkali Metal Ions in Hexamethylphosphoramide