Telling the stories of people who risked their lives to save victims of the Holocaust through music is the focus of a project called The Garden of the Righteous. This project was introduced in a ...recent article in the Interdisciplinary Journal of Partnership Studies, called “Righteous Among the Nations: Music Without Borders” (Eisner et al., 2019). This piece provides an update on the evolution of the project during a time of pandemics.
► A cyclic voltammogram for reduction of Lindane at glassy carbon exhibits one irreversible peak. ► Electroreduction of Lindane is a six-electron process that leads to benzene and a small amount of ...chlorobenzene. ► Computations based on density functional theory suggest possible intermediates involved in the reduction of Lindane. ► Reduction of Lindane is a sequence of six one-electron steps with loss of chloride after each step.
Direct reduction of Lindane (1R,2r,3S,4R,5r,6S-hexachlorocyclohexane, 1) at carbon cathodes in dimethylformamide (DMF) containing 0.10M tetra-n-butylammonium tetrafluoroborate (TBABF4) has been explored by means of cyclic voltammetry and controlled-potential (bulk) electrolysis. Cyclic voltammograms for reduction of 1 at a glassy carbon electrode exhibit two cathodic peaks at −1.40V and −2.10V as well as an anodic peak at −1.93V; the first cathodic peak is attributed to reduction of 1 itself, whereas the second cathodic peak is due to reduction of chlorobenzene that is derived from 1. Controlled-potential (bulk) electrolyses conducted with reticulated vitreous carbon electrodes held at −1.70 or −2.20V reveal that reduction of 1 is essentially a six-electron process that affords benzene as major product (80–100% yield) along with small amounts of chlorobenzene (3–10% yield). To account for these products, a mechanism is proposed that is supported by the results of theoretical computations based on density functional theory.
Cyclic voltammetry has been employed to examine the electrochemistry of nickel(II) salen at a glassy carbon electrode in an ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate, BMIM
+BF
4
−). ...Residual water in the ionic liquid can be eliminated by introduction of activated molecular sieves into the electrochemical cell. Nickel(II) salen exhibits a one-electron, quasi-reversible reduction to nickel(I) salen, and the latter species serves as a catalyst for the cleavage of carbon–halogen bonds in iodoethane and 1,1,2-trichlorotrifluoroethane (Freon
® 113). In BMIM
+BF
4
− the diffusion coefficient for nickel(II) salen at room temperature has been determined to be
1.8×10
−8
cm
2
s
−1
, which is more than 500 times smaller than that
(1.0×10
−5
cm
2
s
−1)
in a typical organic solvent–electrolyte system such as dimethylformamide (DMF) containing 0.10 M tetramethylammonium tetrafluoroborate.
Cyclic voltammetry and controlled-potential (bulk) electrolysis have been used to investigate the direct reduction of 5-chloro-2-(2,4-dichlorophenoxy)phenol (triclosan,
1) in dimethylformamide (DMF) ...containing tetra-
n-butylammonium tetrafluoroborate (TBABF
4). Cyclic voltammograms for reduction of
1 at glassy carbon electrodes exhibit three irreversible peaks attributed to successive reductive cleavage of the three aryl carbon–chlorine bonds. Bulk electrolyses of
1 at reticulated vitreous carbon cathodes held at a potential between the first and second cathodic peaks afford only 5-chloro-2-(4-chlorophenoxy)phenol; however, at a more negative potential, a mixture of 5-chloro-2-(4-chlorophenoxy)phenol, 5-chloro-2-phenoxyphenol, and 2-phenoxyphenol is obtained. A scheme consisting of electron-transfer steps and accompanying chemical reactions is proposed that follows the classic mechanism for the reduction of aryl halides. To provide support for this mechanism, theoretical calculations based on density functional theory have been performed to model the electronic structures of
1 and the likely intermediates formed via its electroreduction. Catalytic reduction of
1 by nickel(I) salen and nickel(I) diethylsalen, each mediator electrogenerated at a glassy carbon electrode in DMF – 0.10
M TBABF
4, has been explored with the aid of cyclic voltammetry and controlled-potential electrolysis.
Cyclic voltammetry and controlled‐potential (bulk) electrolysis have been used to study the direct electrochemical reduction of cyclohexyl bromide (1) and cyclohexyl iodide (2) at glassy carbon ...cathodes in dimethylformamide (DMF) containing 0.10 M tetramethylammonium tetrafluoroborate (TMABF4). Direct reduction of 1 is a one‐step process that affords a carbanion intermediate, whereas 2 undergoes stepwise reduction to a radical and then a carbanion intermediate. Mixtures of cyclohexane, cyclohexene, and bicyclohexyl arise from bulk electrolyses of both 1 and 2. Catalytic reduction of 1 and 2 by nickel(I) salen and cobalt(I) salen electrogenerated at glassy carbon cathodes in DMF‐TMABF4 has been investigated with the aid of both cyclic voltammetry and bulk electrolysis. Products arising from these catalytic reductions are cyclohexane, cyclohexene, and bicyclohexyl, although significant amounts of unreduced 1 are found when cobalt(I) salen is utilized as the catalyst. Mechanistic aspects of the direct and catalyzed reductions of 1 and 2 are discussed.
Radical ideas: Direct electrochemical reduction of cyclohexyl bromide and cyclohexyl iodide at glassy carbon cathodes in dimethylformamide (DMF) containing 0.10 M tetramethyl‐ammonium tetrafluoroborate (TMABF4) affords both free radical‐ and carbanion‐derived products – cyclohexane, cyclohexene, and bicyclohexyl. Reduction of these halides with electrogenerated nickel(I) salen or cobalt(I) salen leads to free‐radical‐derived products (cyclohexane, cyclohexene, and bicyclohexyl) in different amounts.
A new
Na
14
(H
2
P
4
W
6
O
34
)
2
Co
2
Na
2
(H
2
O)
2
·26H
2
O (
1
) species with photocatalytic ability has been prepared and then characterized with the aid of FTIR spectroscopy, UV–visible ...spectrometry, TG/DTG, EDS–SEM, cyclic voltammetry, magnetic measurements,
31
P-NMR, and single-crystal X-ray diffraction. With a turnover number of 180 and a turnover frequency of 8.3 × 10
−4
s
−1
, this polyoxometalate exhibits high catalytic activity for the oxidation of water.
Graphical Abstract
In this paper we express the class of the structure sheaves of the closures of Deligne–Lusztig varieties as explicit double Grothendieck polynomials in the first Chern classes of appropriate line ...bundles on the ambient flag variety. This is achieved by viewing such closures as degeneracy loci of morphisms of vector bundles.
Cyclic voltammetry and controlled-potential electrolysis have been used to investigate the catalytic reduction of hexachlorobenzene and pentachlorobenzene by cobalt(I) salen that is electrogenerated ...at a carbon cathode in dimethylformamide containing 0.050
M tetramethylammonium tetrafluoroborate. Cyclic voltammograms for the reduction of cobalt(II) salen in the presence of either hexachlorobenzene or pentachlorobenzene show an enhanced cathodic peak for the catalyst–substrate reaction as well as loss of the anodic peak for reoxidation of cobalt(I) salen, revealing the effectiveness of the catalyst. However, cobalt(I) salen shows no catalytic activity toward tetrachlorobenzene or any less-chlorinated species. Controlled-potential electrolyses of cobalt(II) salen–hexachlorobenzene mixtures give both pentachlorobenzene and three isomers of tetrachlorobenzene, whereas bulk catalytic reduction of pentachlorobenzene affords three different tetrachlorobenzenes; for both substrates, substantial starting material remains unreduced. To account for the formation of the various products, a mechanistic scheme is proposed and discussed.
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