Copper/ions/salts

In the presence of excess iodide ions, copper(II) salts produce the white insoluble copper(I) iodide and free iodine, because copper(II) oxidises iodide under these conditions. The redox potential for the half-reaction ... 

When a copper(II) salt dissolves in water, the complex aquo-ion [Cu(H2p)6P is formed this has a distorted octahedral (tetragonal) structure, with four near water molecules in a square plane around the copper and two far water molecules, one above and one below this plane. Addition of excess ammonia replaces only the four planar water molecules, to give the deep blue complex [Cu(NH3)4(H20)2] (often written as [Cu(NHj)4] for simplicity). TTo obtain [Cu(NH3)6], water must be absent, and an anhydrous copper(II) salt must be treated with liquid ammonia. 

Copperil) cyanide. CuCN (and copperil) thiocyanate), are similarly obtained as white precipitates on adding cyanide and thiocyanate ions (not in excess) respectively to copper(II) salts ... 

The reaction mechanism is not rigorously known, but is likely to involve the following steps." " First the arenediazonium ion species 1 is reduced by a reaction with copper-(l) salt 2 to give an aryl radical species 4. In a second step the aryl radical abstracts a halogen atom from the CuXa compound 5, which is thus reduced to the copper-1 salt 2. Since the copper-(l) species is regenerated in the second step, it serves as a catalyst in the overall process. 

Cupri-. cupric, copper(II). -azetst, n. cupric acetate, copper(II) acetate, -carbonat, n. cupric carbonate, copper(II) carbonate, -chlorid, n. cupric chloride, copper(II) chloride. -hydroxyd, n. cupric hydroxide, cop-per(II) hydroxide. -ion, n. cupric ion, copper(II) ion. -ozalat, n. cupric oxalate, copper(II) oxalate, -oxyd, n. cupric oxide, copper(II) oxide. -salz, n. cupric salt, copper(II) salt, -suifat, n. cupric sulfate. copper(II) sulfate, -sulfid, n. cupric sulfide, copper(II) sulfide, -verbihdung, /. cupric compound, copper(II) compound, -wein-saure, /. cupritartaric acid. 

K has the value of about 1 x 10 at 298 K, and in solutions of copper ions in equilibrium with metallic copper, cupric ions therefore greatly predominate (except in very dilute solutions) over cuprous ions. Cupric ions are therefore normally stable and become unstable only when the cuprous ion concentration is very low. A very low concentration of cuprous ions may be produced, in the presence of a suitable anion, by the formation of either an insoluble cuprous salt or a very stable complex cuprous ion. Cuprous salts can therefore exist in contact with water only if they are very sparingly soluble (e.g. cuprous chloride) or are combined in a complex, e.g. [Cu(CN)2) , Cu(NH3)2l. Cuprous sulphate can be prepared in non-aqueous conditions, but because it is not sparingly soluble in water it is immediately decomposed by water to copper and cupric sulphate. 

When ammonia is added to an aqueous solution of a copper(II) salt, a deep, almost opaque, blue color develops (Figure 15.1). This color is due to the formation of the Cu(NH3)42+ ion, in which four NH3 molecules are bonded to a central Cu2+ ion. The formation of this species can be represented by the equation... 

Fast sulphon black F ( C.I.26990). This dyestuff is the sodium salt of 1-hydroxy-8-( 2-hydroxynaphthylazo) -2- (sulphonaphthylazo) -3,6-disulph onic acid. The colour reaction seems virtually specific for copper ions. In ammoniacal solution it forms complexes with only copper and nickel the presence of ammonia or pyridine is required for colour formation. In the direct titration of copper in ammoniacal solution the colour change at the end point is from magenta or [depending upon the concentration of copper(II) ions] pale blue to bright green. The indicator action with nickel is poor. Metal ions, such as those of Cd, Pb, Ni, Zn, Ca, and Ba, may be titrated using this indicator by the prior addition of a reasonable excess of standard copper(II) solution. 

A salt bridge serves as an ionconducting connection between the two half-cells. When the external circuit is closed, the oxidation reaction starts with the dissolution of the zinc electrode and the formation of zinc ions in half-cell I. In half-cell II copper ions are reduced and metallic copper is deposited. The sulfate ions remain unchanged in the aqueous solution. The overall cell reaction consists of an electron transfer between zinc and copper ions ... 

The synthesis and mechanism of formation of a triazene from an arenediazonium ion and an amine with one or two aliphatic substituents (see Scheme 13-1, R = alkyl, R = H or alkyl) will be discussed in Section 13.2. Here we will briefly mention Dimroth s method (1903, 1905 a) for synthesis of wholly aliphatic triazenes (Scheme 13-6, R and R = alkyl). Dimroth obtained these by the action of Grignard reagents on alkyl azides followed by isolation via copper(i) salts. The Grignard method can also be applied for the synthesis of triazenes with an aromatic substituent by using an aryl azide. 

Like all the coinage metals, copper forms compounds with oxidation number + 1. However, in water, copper(I) salts disproportionate into metallic copper and copper(II) ions. The latter exist as pale blue [Cu(H20)6]2+ ions in water. 

The reaction with ammonia or amines, which undoubtedly proceeds by the SnAt mechanism, is catalyzed by copper and nickel salts, though these are normally used only with rather unreactive halides. This reaction, with phase-transfer catalysis, has been used to synthesize triarylamines. Copper ion catalysts (especially cuprous oxide or iodide) also permit the Gabriel synthesis (10-61) to be... 

Copper salts such as CuS04 are potent catalysts of the oxidative modification of LDL in vitro (Esterbauer et al., 1990), although more than 95% of the copper in human serum is bound to caeruloplasmin. Cp is an acute-phase protein and a potent inhibitor of lipid peroxidation, but is susceptible to both proteolytic and oxidative attack with the consequent release of catalytic copper ions capable of inducing lipid peroxidation (Winyard and... 

The alkylamination of quinizarin (22) in the presence of copper salts has been studied by Matsuoka and co-workers.16 The reaction proceeds via oxidation by copper ion of 22 to quinizarinoquinone (29). 2-Alkylamino-quinizarin (25) was obtained in quantitative yield. The 1,2-ring-closure product (30) is obtained by the reaction of 22 with ethylenediamines in the presence of copper ions17 (Scheme 9). 

The rate of release of NO from SNAP in the absence of any copper ions (the spontaneous or thermal reaction) is very slow indeed. The reason for the very low stability of nitrosocysteine is that there is a ready complexation of copper ions to this compound, a process that is the precursor of NO release [18]. Further studies by Butler and Williams [19] showed that it is the cuprous ion, Cu(I), which is the active species in effecting NO release from a nitrosothiol, whatever copper salt is present in solution. Cuprous ions are readily generated from Cu(II) by reaction with a thiol ... 

The reaction is initiated by attack of a nucleophile (Ye), usually the counterion associated with the Cu ion, at one of the CN groups of the phthalonitrile, which is activated by its coordination with the Cu ion. Subsequently a cycliza-tion reaction to an isoindoline derivative takes place. These steps are three times repeated by a series of similar reactions finally resulting in a cyclization to a CuPc ring intermediate, whose formation is facilitated by the coordinating role of the copper ion. With a copper (II) salt as reactant it is suggested that Y is eliminated from the intermediate, e.g. the Cl ion in the case of CuCl2. The monochloro de-rivate of CuPc is than formed by an electrophilic attack of Cl on the CuPc initially formed. 

In contrast to Bosman et al., who only found metal complexation in the periphery of polypropylene imine) dendrimers, Tomalia and co-workers reported on the incorporation of copper ions into the interior of PAMAM dendrimers judging from EPR and UV/Vis studies [220, 221]. Metal binding in the dendrimer interior has also been observed for dendrimers carrying multiple ligands for metal complexation within their framework such as crown-ethers [222, 223] (Cs(I)-complexes), piperazine [224] (Pd(II)- and Cu(II)-complexes) or triazocyclononane [225] (Cu(II)- and Ni(II)-complexes). In most cases addition of the metal-salt to the dendrimer led to the formation of 1 1 complexes. 

Example Polystyrenes ranging from PS 2200 to PS 12500 form [M+metal] ions with Ag" and Cu" ions when silver or copper(I) salts are admixed to the sample preparation, hi case of PS 12500, both metal ions were found to effect cationi-zation equally well, i.e., without causing differences in average molecular weight or ionic abundances (Fig. 10.12). [106]... 

In summary, the copper ion transfers an electron from the unsaturated substrate to the diazo-nium cation, and the newly formed diazonium radical quickly loses nitrogen. The aryl radical formed attacks the ethylenic bond within the active complexes that originated from aryldiazo-nium tetrachlorocuprate(II)-olefin or initial arydiazonium salt-catalyst-olefln associates and yields >C(Ar)-C < radical. The latter was detected by the spin-trap ESR spectroscopy. The formation of both the cation-radical [>C=C<] and radical >C(Ar)-C < as intermediates indicates that the reaction involves two catalytic cycles. In the other case, radical >C(Ar)-C < will not be formed, being consumed in the following reaction ... 

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