Cupric modifications

Cupric sulfide, CuS, occurring as the mineral covellite (also known as covelline), exhibits a very unusual structure, in which the Cu is again partly 3-coordinate and partly 4-coordinate, with two-thirds of the sulfur atoms existing as S2 groups like those in pyrites. The low-temperature form of CuSe has also a covellite structure, the high-temperature modification (P-CuSe) being orthorhombic. All CuX2 compounds assume pyrite-type structures. 

A modification of the RDC design, based on the ring-disk arrangement of the RDE [36], incorporated an arc electrode [37,38] deposited on the surface of the membrane around the untreated area. This facilitated the electrochemical detection of species reacting at the interface at short times following the reaction. This method was used to study the solvent extraction of cupric ions, which were detected by reduction to copper metal at the arc electrode. The resulting current flow was related to the interfacial flux at the membrane. 

Additional acceleration of acylation can be obtained by inclusion of cupric salts, which coordinate at the pyridine nitrogen. This modification is useful for the preparation of highly hindered esters.122 Pyridine-2-thiol esters can be prepared by reaction of the carboxylic acid with 2,2 -dipyridyl disulfide and triphenylphosphine123 or directly from the acid and 2-pyridyl thiochloroformate.124... 

In contrast to numerous literature data, which indicate that protein oxidation, as a rule, precedes lipid peroxidation, Parinandi et al. [66] found that the modification of proteins in rat myocardial membranes exposed to prooxidants (ferrous ion/ascorbate, cupric ion/tert-butyl-hydroperoxide, linoleic acid hydroperoxide, and soybean lipoxygenase) accompanied lipid peroxidation initiated by these prooxidant systems. 

Carbon tetrachloride can be substituted for chloroform in this reaction when the cupric chloride modification described above is used. 

The ignition temperature of cupric azide is 202-205°C. The dry substance is exceptionally sensitive to friction, especially the green modification, and is often exploded by contact. It is also very sensitive to impact the green modification is exploded by a 2 kg weight falling from a height of less than 1 cm, the black one from a drop of about 1 cm. 

The most economical commercial preparation is high-temperature chlorination of ethene. A useful modification of this process uses hydrogen chloride in place of chlorine. An oxidizing agent is required to raise the oxidation state of chlorine in HC1 to that of Cl2 molecular oxygen is used for this purpose along with cupric salts as catalysts. 

The formation of the chlorides is effected in the dry way by calcination with sodium chloride or in the wet way by interaction with ferrous chloride and hydrochloric acid or with ferric chloride. The wet way is only adopted if fuel is scarce, or the escape of noxious vapours into the atmosphere is not permissible. In the dry method the ore is oxidized by a preliminary roasting, and then chloridized by calcination with sodium chloride or Abraum salts in a furnace of the reverberatory or muffle type, the principal product being cupric chloride. The Dotsch modification of the wet process, worked at Rio Tinto, depends on the action of ferric-chloride solution on a mixture of the ore with sodium sulphate and ferric chloride. The liquid drawn off from the bottom of the heaps of ore contains cuprous chloride in solution as a complex salt. The copper is liberated by the action of iron, the ferrous chloride simultaneously formed being chlorinated in towers to ferric chloride, and the product employed for moistening the heaps of ore. 

Cupric hydroxide, Cu(OH)2.—The hydroxide has been prepared in crystalline form by the action of a solution of caustic alkali on a basic cupric nitrate 2 and a basic cupric sulphate,3 and also by other methods.4 A hydrogel of varying composition is precipitated by addition of alkali to solutions of cupric salts.5 Unlike the colloidal form, the blue crystalline variety is stable at 100° C. A solid, colloidal variety has been obtained 6 as blackish-blue, brittle lamellae which dissolve in water to form the original solution. An amorphous modification is precipitated from ammoniaeal copper solutions by the action of alkali-metal hydroxides.7... 

The nature of the active site in beta-amylase is not unambiguously known for enzymes from different sources. Early experiments on purified barley and on malted barley first indicated, from studies of the modification of the enzyme with nitrous acid and ketene, that free tyrosine and sulfhydryl groups are essential for activity, whereas free a-amino groups are not. The importance of the sulfhydryl groups was emphasized by the partial recovery of activity of the modified or oxidized enzyme (that is, treated with nitrous acid, iodine, phenyl mercuribenzoate, ferricyanide, and cupric ions) when it was treated with hydrogen sulfide or cysteine. Barley feeto-amylase (not highly purified) has been reported to contain 12—15 sulfhydryl groups per molecule by titration with p-chloromercuribenzoate, and the loss of free sulfhydryl content by treatment with L-ascorbic acid in the presence of cupric ions was found to be directly related to the loss of activity. 

Novel polymerizable phosphatidylcholines were successfully synthesized by the research team of G. Just. To prepare a 32-membered macrocyclic diyne, the Eglinton modification of the Giaser coupiing was utilized. The diester-diyne starting material was slowly added to a refluxing solution containing 10 equivalents of cupric acetate in dry pyridine. The macrocycle was isolated in 54% yield after column chromatography. 

Bart reaction. (Scheller modification Star-key modification). Formation of aromatic arsonic acids by treating aromatic diazonium compounds with alkali arsenites in the presence of cupric salts or powdered silver or copper in the Scheller modification, primary aromatic amines are diazotized in the presence of arsenious chloride and a trace of cuprous chloride. 

This reaction was first reported by Bart in 1910. It is the synthesis of arylarsenic acids from aromatic diazonium compounds with alkali arsenites in the presence of cupric salts, powdered silver, or copper. Therefore, this reaction is generally known as the Bart reaction. In addition, the reaction between aromatic diazonium and arsenious chloride in the presence of trace amounts of cuprous chloride is referred to as the Scheller modification. Besides the Scheller modification, the Sakellarios modification is the reaction between sulfanilamide and phenyldisodium arenite. ... 

The acidic monmorillonite clay-supported cupric nitrate has been applied to improve the yield in addition, the application of cupric nitrate impregnated on H-ZSM-5 zeolite with a large number of internal active regions has altered the regioselectivity of nitration. Further modifications have adapted the combination of cupric nitrate and trifluoroacetic anhydride as the nitrating agent. ... 

This reaction has been extended by Weidenhagen through the condensation of Qf-acetoacetone, cupric acetate, and aqueous ammonia to afford imidazoles in yields up to 60%. " This method is thus known as the Weidenhagen modification or Weidenhagen Synthesis. In addition, the Radziszewski reaction has been further modified to proceed in acetic acid by the use of ammonium acetate or ammonium carbonate as the source of ammonia to give imidazoles of markedly improved yields,and this protocol has been recently carried out under microwave irradiation. Furthermore, it has been reported that the reaction of an amidine with an of-halo ketone also readily yields imidazoles. 

Additional acceleration of the rate of acylation can be obtained by inclusion of cupric salts that coordinate at the pyridine nitrogen. This modification is especially useful for... 

The CASS test and Corrodkote procedure are employed primarily for testing decorative chromium systems, with the CASS test ako being useful for testing anodized aluminum. These tests were developed to give a more rapid indication of corrosion resistance and a better correlation with service performance. They have come into prominence tis the most widely used modifications of the salt spray test because of their greater speed. Both tests employ cupric ion in the corrodant... 

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