Cupric ions

Cupric ion has a unique abitity to compete with oxygen for a carbon-centered free radical (compare reaction 2) ... 

The hberated iodine, as the complex triiodide ion, may be titrated with standard thiosulfate solution. A general iodometric assay method for organic peroxides has been pubUshed (253). Some peroxyesters may be determined by ferric ion-catalyzed iodometric analysis or by cupric ion catalysis. The latter has become an ASTM Standard procedure (254). Other reducing agents are ferrous, titanous, chromous, staimous, and arsenite ions triphenylphosphine diphenyl sulfide and triphenjiarsine (255,256). 

The potentiometric micro detection of all aminophenol isomers can be done by titration in two-phase chloroform-water medium (100), or by reaction with iodates or periodates, and the back-titration of excess unreacted compound using a silver amalgam and SCE electrode combination (101). Microamounts of 2-aminophenol can be detected by potentiometric titration with cupric ions using a copper-ion-selective electrode the 3- and... 

The preferred ratio of cuprous to cupric ion ranges from 5 1 to 10 1, depending on system conditions. Too high a concentration of cuprous ion causes the system to disproportionate and form metallic copper (eq. 26) ... 

Cupric ion concentration is kept at an acceptable but low level by direct air oxidation of the solution. SoHds formation from sulfides in the feed gas is also possible therefore, pretreatment for sulfur removal is required. 

Carbon dioxide can cause product contamination through ammonium carbonate formation. Ammonium carbonate may also form by oxidation of carbon monoxide by cupric ion (eq. 27) ... 

The darkening reaction involves the formation of silver metal within the silver haUde particles containing traces of cuprous haUde. With the formation of metallic silver, cuprous ions are oxidized to cupric ions (1,4). The thermal or photochemical (optical bleaching) reversion to the colorless or bleached state corresponds to the reoxidation of silver to silver ion and the reduction of cupric ion to reform cuprous ion. 

The composition of this alloy (54% nickel, 15% molybdenum, 15% chromium, 5% tungsten and 5% iron) is less susceptible to intergranular corrosion at welds. The presence of chromium in this alloy gives it better resistance to oxidizing conditions than the nickel/molybdenum alloy, particularly for durability in wet chlorine and concentrated hypochlorite solutions, and has many applications in chlorination processes. In cases in which hydrochloric and sulfuric acid solutions contain oxidizing agents such as ferric and cupric ions, it is better to use the nickel/molybdenum/ chromium alloy than the nickel/molybdenum alloy. 

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. 

Early examples of enantioselective extractions are the resolution of a-aminoalco-hol salts, such as norephedrine, with lipophilic anions (hexafluorophosphate ion) [184-186] by partition between aqueous and lipophilic phases containing esters of tartaric acid [184-188]. Alkyl derivatives of proline and hydroxyproline with cupric ions showed chiral discrimination abilities for the resolution of neutral amino acid enantiomers in n-butanol/water systems [121, 178, 189-192]. On the other hand, chiral crown ethers are classical selectors utilized for enantioseparations, due to their interesting recognition abilities [171, 178]. However, the large number of steps often required for their synthesis [182] and, consequently, their cost as well as their limited loadability makes them not very suitable for preparative purposes. Examples of ligand-exchange [193] or anion-exchange selectors [183] able to discriminate amino acid derivatives have also been described. 

During the operation of the cell (or during the direct interaction of zinc metal and cupric ions in a beaker) the zinc is oxidised to Zn and corrodes, and the Daniell cell has been widely used to illustrate the electrochemical mechanism of corrosion. This analogy between the Daniell cell and a corrosion cell is perhaps unfortunate, since it tends to create the impression that corrosion occurs only when two dissimilar metals are placed in contact and that the electrodes are always physically separable. Furthermore, although reduction of Cu (aq.) does occur in certain corrosion reactions it is of less importance than reduction of HjO ions or dissolved oxygen. 

Frazer, M. J. and Langstaff, R. D., Influence of Cupric Ions on the Behaviour of Surface-active Agents Towards Aluminium , Bril. Corrosion J., 2, II (1%7) Szklarska-Smialowska, Z. and Janik-Czachor, H., Pitting Corrosion of 13Cr-Fe Alloy in Na2S04 Solutions Containing Chloride Ions , Corros. Sci., 7, 65 (1967)... 

Copper is the first member of Group IB of the periodic table, having atomic number 29 and electronic configuration 2.8.18.1. Loss of the outermost electron gives the cuprous ion Cu, and a second electron may be lost in the formation of the cupric ion Cu. ... 

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. 

The equilibrium between copper and cuprous and cupric ions is disturbed by the presence of oxygen in solution, since the reaction shown in equation 4.3 is facilitated, the oxygen acting as an electron acceptor. 

Reducing sugar (Section 25.6) A sugar that reduces silver ion in the Tollens test or cupric ion in the Fehling or Benedict tests. 

What about the state of equilibrium for the reaction represented by equation (11)1 Let us place a strip of metallic copper in a zinc sulfate solution. No visible reaction occurs and attempts to detect the presence of cupric ion by adding H2S to produce the black color of cupric sulfide, CuS, fail. Cupric sulfide has such low solubility that this is an extremely sensitive test, yet the amount of Cu+2 formed cannot be detected. Apparently the state of equilibrium for the reaction (11) greatly favors the products over the reactants. 

The reaction between ferric ion, Fe+3, and cuprous ion, Cu+, to produce ferrous ion, Fe+2, and cupric ion, Cu+2, is plainly an oxidation-reduction reaction ... 

Nickel metal reacts with cupric ions, Cu42, but not with zinc ions, Zn42 magnesium metal does react with Zn42. In each case of reaction, ions of +2 charge are formed. Use these data to expand the table of reactions on p. 206. 

The +1 state of copper is found only in complex compounds or slightly soluble compounds. The reason for this is that in aqueous solution cuprous ion is unstable with respect to disproportionation to copper metal and cupric ion. This comes about because cuprous going to cupric is a stronger reducing agent than copper going to cuprous. The following exercise in the use of E° puts this on a more quantitative basis ... 

A further way in which metabolic control may be exercised is the artificial deprivation of required ions and cofactors, for example aconitase must have ferrous ions for activity. Conversely, addition of toxic ions is possible, for example aconitase is inhibited by cupric ions. Finally the use of metabolic analogues is possible. If monofluoroacetate is added to cells then monofluorocitrate is produced by titrate synthase and this compound inhibits the activity of aconitase. Great care has to be taken when using metabolic analogues, however, they are often less than 100% specific and may have unexpected and unwanted serious side effects. 

When cleaning boilers containing iron-copper deposits (with, say, hydrochloric acid), unless special precautions are taken, the cupric oxide dissolves and the cupric ion is reduced to copper, which then replates onto the steel surface, thus beginning the corrosion cycle again. 

From the first of the two reactions shown, it can be seen that in the acid cleaning solution the cupric ion (Cu2+) is formed from cupric oxide. The thiourea component then reduces the cupric ion to the cuprous ion (Cu+) and, in a series of reactions, complexes it, essentially preventing the cupric ion from ultimately plating out as copper. 

Apart from generating the cupric ion, the acidic oxidation reaction (loss of electrons) produces cuprous ion as an intermediate from any cuprous oxide that may be present in the deposit. It is therefore neces-... 

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