A copper catalyzed click chemistry ligation process is employed to bind azides and terminal acetylenes to provide 1,4-disubstituted 1,2,3-triazole triazoles. The process comprises contacting an organic azide and a terminal alkyne with a source of reactive Cu(I) ion for a time sufficient to form by cycloaddition a 1,4-disubstituted 1,2,3-triazole. The source of reactive Cu(I) ion can be, for example, a Cu(I) salt or copper metal. The process is preferably carried out in a solvent, such as an aqueous alcohol. Optionally, the process can be performed in a solvent that comprises a ligand for Cu(I) and an amine.

Copper-catalysed ligation of azides and acetylenes

Copper, a native metal found in ores, is the principal metal in bronze and brass. It is a reddish metal with a density of 8920 kg m−3. All of copper’s compounds tend to be brightly colored: for example, copper in hemocyanin imparts a blue color to blood of mollusks and crustaceans. Copper has three oxidation states, with electronic configurations of Cu([Ar]3 d 104 s 1), Cu+([Ar]3 d 10), and Cu2+([Ar]3 d 9). Cu does not react with aqueous hydrochloric or sulfuric acids, but is soluble in concentrated nitric acid due to its lesser tendency to be oxidized. Cu(I) exists as the colorless cuprous ion, Cu+. Cu(II) is found as the sky-blue cupric ion, Cu2+. The Cu+ ion is unstable, and tends to disproportionate to Cu and Cu2+. Nevertheless, Cu(I) forms compounds such as Cu2O. Cu(I) bonds more readily to carbon than Cu(II), hence Cu(I) has an extensive chemistry with organic compounds.

In aqueous solutions, Cu2+ ion occurs as an aquacomplex. There is no clearly predominant structure among the four-, five-, and six-fold coordinated Cu(II) species (Chaboy et al. 2006). Hydrated Cu(II) ion has been represented as the hexaaqua complex Cu(H2O)62+, which shows the Jahn–Teller distortion effect (Sherman 2001; Bersuker 2006), whereby the two Cu–O distances of the vertical axial bond (Cu–Oax) are longer than four Cu–O distances in the equatorial plane (Cu–Oeq). The Jahn–Teller effect lowers the symmetry of Cu(H2O)62+ from octahedral Th to D2h. The sixfold coordination of hydrated Cu(II) species is questioned by a finding of fivefold coordination (Pasquarello et al. 2001; Chaboy et al. 2006; Little et al. 2014b …

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The Isotope Geochemistry of Zinc and Copper

Reactions of L-ascorbic acid with transition metal complexes

The purpose of this review is to summarize developments in the chemistry and metabolism of ascorbic acid during the past 14 years. Particular emphasis has been placed on information concerning ascorbate sulfate. Ofttimes the development of new chemistry related to ascorbic acid has appeared to progress slowly, yet in retrospect considerable progress has been made during the past 14 years. The work has been done in many laboratories and by many people. The major thrust of chemical work has been (1) to prepare chemical derivatives with biological activity but resistant to air oxidation, (2 ) to understand oxidative decomposition of ascorbic acid, and (3) to develop easier or better analytical methods for assay of ascorbic acid. In this report no coverage has been made of chemical developments to be reviewed by other speakers at this conference, such as the chemistry of monodehydroascorbic acid, or the enzyme ascorbic acid oxidase.

Chemistry and metabolism of ascorbic acid and ascorbate sulfate

Hydrogen peroxide was discovered in 1818 and has been used in bleaching for over a century [1]. H2O2 on its own is a relatively weak oxidant under mild conditions: It can achieve some oxidations unaided, but for the majority of applications it requires activation in one way or another. Some activation methods, e.g., Fenton's reagent, are almost as old [2]. However, by far the bulk of useful chemistry has been discovered in the last 50 years, and many catalytic methods are much more recent.



Although the decomposition of hydrogen peroxide is often employed as a standard reaction to determine the catalytic activity of metal complexes and metal oxides [3,4], it has recently been extensively used in intrinsically clean processes and in end-of-pipe treatment of effluent of chemical industries [5,6]. Furthermore, the adoption of H2O2 as an alternative of current industrial oxidation processes offer environmental advantages, some of which are (1) replacement of stoichiometric metal oxidants, (2) replacement of halogens, (3) replacement or reduction of solvent usage, and (4) avoidance of salt by-products. On the other hand, wasteful decomposition of hydrogen peroxide due to trace transition metals in wash water in the fabric bleach industry, was also recognized [7].



The low intrinsic reactivity of H2O2 is actually an advantage, in that a method can be chosen which selectively activates it to perform a given oxidation. There are three main active oxidants derived from hydrogen peroxide, depending on the nature of the activator; they are (1) inorganic oxidant systems, (2) active oxygen species, and (3) per oxygen intermediates.



Two general types of mechanisms have been postulated for the decomposition of hydrogen peroxide in the presence of transition metal complexes. The first is the radical mechanism (outer sphere), which was proposed by Haber and Weiss for the Fe(III)-H2O2 system [8]. The key features of this mechanism were the discrete formation of hydroxyl and hydroperoxy radicals, which can form a redox cycle with the Fe(II)/Fe(III) couple. The second is the peroxide complex mechanism, which was proposed by Kremer and Stein [9]. The significant difference in the peroxide complex mechanism is the two-electron oxidation of Fe(III) to Fe(V) with the resulting breaking of the peroxide oxygen-oxygen bond.



It is our intention in this article to briefly summarize the kinetics as well as the mechanisms of the decomposition of hydrogen peroxide, homogeneously and heterogeneously, in the presence of transition metal complexes. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 643–666, 2000

Kinetics and mechanisms of decomposition reaction of hydrogen peroxide in presence of metal complexes

The kinetics of the oxidation of ascorbic acid by the copper(II) ion has been studied spectrophotometrically by a stopped-flow technique. At pH 4–6, the initial rate of the decrease in the monohydroascorbate anion is of the second-order with respect to the total concentration of the copper(II) ion and of the first-order with respect to the concentrations of the monovalent and divalent ions of ascorbic acid:-(d[HA^-]/dt)_t=0=k_1[Cu(II)]_T^2[HA^-]+k_2[Cu(II)]_T^2[A^2-] where HA− and A2− are the monovalent and divalent ions of ascorbic acid respectively. k1, k2, and the activation parameters are obtained as follows: k1=3.1×104, k2=6.1×1010 M−2 s−1, ΔH\eweq=17 kcal/mol, ΔS\eweq=8.3 cal/deg mol, and ΔG\eweq=15 kcal/mol. The EPR signal from the ascorbate radical is not observed in the kinetic run by either a flow technique or a quenching technique. Some discussions of the mechanism of the reaction are given.

Kinetics of the Oxidation of Ascorbic Acid by the Copper (II) Ion in an Acetate Buffer Solution

The catalytic decomposition of hydrogen peroxide by the ammine-copper(II) complex ions has been studied using kinetic measurements, UV and visible spectroscopy, electron-spin resonance spectroscopy, and polarography. It was found that there were two reaction paths in the catalytic decomposition of hydrogen peroxide. In the first case, a linear part was observed in the plot of the amount of oxygen evolved vs. time. In this case, a brown intermediate was formed which was later found to be a diamagnetic peroxo-copper complex and to contain some of the stable oxygen anion radical just after the mixing of the reactants. The activation energy of the reaction was found to be 23±1 kcal mol−1. In the second case, no linear part was observed in the kinetic curve. In this case, the reaction had a reaction order in hydrogen peroxide varying from the first- to the second-order depending on the initial concentrations of the reactants. The nature of the brown compound and the active species of the reaction is discussed.

The Decomposition of Hydrogen Peroxide with Metal Complexes. I. The Catalytic Decomposition of Hydrogen Peroxide by the Ammine-Copper(II) Complex Ions in an Aqueous Solution

The formation constants of the triiodide ion were determined in water-alcohol mixed solvents by a spectro-photometric method at various temperatures. The formation reaction of the triiodide ion from an iodide ion and an iodine molecule is accompanied by a negative enthalpy change and a positive entropy change at various alcohol contents: ΔH°/kJ mol−1, −15.4 (in water) to −14.3 (in methanol) in the water–methanol system, −15.4 (in water) to −21.4 (in ethanol) in the water–ethanol system; ΔSx°/J K−1 mol−1, 36 (in water) to 57 (in methanol) in the water–methanol system, and about 36 at various ethanol contents in the water-ethanol system. The enthalpy term is the dominant factor in the water–ethanol mixtures, whereas the entropy term is the dominant factor in the water–methanol mixtures. In order to explain the thermodynamic behavior, the changes in the solvation properties as well as the activity coefficients of solutes must be considered in both the mixture systems.

The Detemination of the Formation Constants of the Triiodide Ion in Water–Alcohol Mixed Solvents at Various Temperatures

PROBLEM TO BE SOLVED: To provide a power feed system having a means which stably feeds power even if a voltage is instantaneously lowered, does not cause an actual harm, and copes with the instantaneous voltage drop, and to streamline and simplify the system SOLUTION: This receiving equipment comprises: a general load bus bar connected to a commercial line, a general load which receives power from the general load bus bar; an important load bus bar which is connected to the general load bus bar via a high-speed breaker, and connected to a cogeneration power generation system; and an important load which receives power from the important load bus bar While the voltage is instantaneously lowered at least at the general load bus bar, the high-speed breaker disconnects the general load bus bar from the important load bus bar, and power is fed to the important load from the cogeneration power generation system COPYRIGHT: (C)2009,JPO&INPIT

Sumio Nakamura

Papers

Kinetics of the Oxidation of Ascorbic Acid by the Copper (II) Ion in an Acetate Buffer Solution

The Decomposition of Hydrogen Peroxide with Metal Complexes. I. The Catalytic Decomposition of Hydrogen Peroxide by the Ammine-Copper(II) Complex Ions in an Aqueous Solution

The Detemination of the Formation Constants of the Triiodide Ion in Water–Alcohol Mixed Solvents at Various Temperatures

Power feed system of receiving equipment

Kinetics of the oxidation of ascorbic acid by the copper(ii) ion in an acetate buffer solution