Copper ions act

Metal ions. Copper ions act as catalysts to accelerate deterioration reactions of many polymers, particularly synthetic rubbers. Spectacle frames constructed from cellulose nitrate are often more degraded in the area around copper-containing screws and around the wires in the arms, than... 

Here, the copper ion acts as a Lewis acid, and the ammonia is a Lewis base. The Cu (hydrated) ion is pale blue in solution, while the ammonia (the ammine) complex is deep blue. A similar reaction occurs with the green hydrated nickel ion to form a deep blue anunine complex. 

Therefore, equilibrimn (8) shifts to the left if whereas the redox potential of the Cu°Lm/Cu L couple is shifted cathodically if I >I (10). Thus, the addition of ligands for which both these criteria are fulfilled to a mixture of Cu (aq) and Cu° increases the concentration of the Cud) species in the solution and transforms the Cud) species into a stronger reducing agents. This is of importance in some catalytic systems where copper ions act as the catalyst and the activity depends on the redox potential of the [Cu(II)L ]/[Cu(I)L j] couple (10,25,29,30). 

Silver and copper ions act synergistically in the killing of Legionella bacteria, which are known to multiply in biofilms in hot water distribution systems. Copper-silver ionization has been used successfully to control Legionella spp. in many US hospital hot water systems after 5 to 11 years of operation however, high pH values and elevated chloride concentrations have negative effects on the biocidal efficacy of copper and silver, respectively, in water systems (Lin et al., 2002). 

Irradiation at 254 nm of solutions containing CuBr and norbomene results in dimerization of the olefm. Subsequent work with copper triflate [Cu(OTF)] in place of CuBr results in the formation of the exo,trans,exo dimer in 88% yield. Analysis of the quantum yield and other data from this photoreaction leads to the conclusion that a 1 2 ratio of Cu(I) alkene complex is the direct precursor of the dimer. A pathway involving a-bonded Cu-alkyl intermediates is a likely one (Scheme 7.1), although an alternative pathway has been considered where the copper ion acts purely as a template for the allowed photochemical [2+2] cycloaddition. 

Iron and chromium ions show negative influence in the photostability of polypropylene, whereas copper ions act as antioxidants [448]. 

May was the first to stress the important role pf CujClj within the pits on the mechanism, and he considered that it acted as a screen that prevented dissolved oxygen gaining access to the bottom of the pit thus preventing the formation of a protective CujO film the low solubility of CU2CI2 also maintained the activity of copper ions at a low value and thus facilitated anodic dissolution of the copper. 

Little work has been carried out on the mechanism of inhibition of the corrosion. of copper in neutral solutions by anions. Inhibition occurs in solutions containing chromate , benzoate or nitrite ions. Chloride ions and sulphide ions act aggressively. There is evidence that chloride ions can be taken up into the cuprous oxide film on copper to replace oxide ions and create cuprous ion vacancies which permit easier diffusion of cuprous ions through the film, thus increasing the corrosion rate. 

Many of the d-block elements form characteristically colored solutions in water. For example, although solid copper(II) chloride is brown and copper(II) bromide is black, their aqueous solutions are both light blue. The blue color is due to the hydrated copper(II) ions, [Cu(H20)fJ2+, that form when the solids dissolve. As the formula suggests, these hydrated ions have a specific composition they also have definite shapes and properties. They can be regarded as the outcome of a reaction in which the water molecules act as Lewis bases (electron pair donors, Section 10.2) and the Cu2+ ion acts as a Lewis acid (an electron pair acceptor). This type of Lewis acid-base reaction is characteristic of many cations of d-block elements. 

Copper (II) ions act as the oxidising agent (itself reduced) ... 

These copper ion-dependent enzymes [EC 1.10.3.1] (also referred to as diphenol oxidases, O-diphenolase, phe-nolases, polyphenol oxidases, or tyrosinases) catalyze the reaction of two catechol molecules with dioxygen to produce two 1,2-benzoquinone and two water. A variety of substituted catechols can act as substrates. Many of the enzymes listed under this classification also catalyze a monophenol monooxygenase activity [/.c., EC 1.14.18.1]. See also Monophenol Monooxygenase Tyrosine Monooxygenase... 

Mechanical components used in fuel systems such as pumps, valves, and bearings may contain copper or copper-containing alloys. As a fuel system component, copper is especially undesirable because it acts as a catalyst in promoting the oxidation of fuel paraffins to oxygen-rich, gumlike deposits. The following reaction sequence represents how copper ions can catalyze the oxidation and degradation of hydrocarbons. 

Prevent copper-catalyzed oxidation of fuel components. Copper ions can act as catalysts to initiate the rapid oxidation and degradation of fuel components. The result of this rapid oxidation will be a darkened, viscous fuel residue. 

Concentrated sulfuric acid will also act as a powerful oxidising agent. For example, when heated with metals such as copper it will oxidise them to copper ions and form copper(n) sulfate. 

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