Copper stoichiometric processes

The industrial catalytic Reppe process is usually applied in the production of acrylic acid. The catalyst is NiBr2 promoted by copper halides used under forcing conditions. The BASF process, for example, is operated at 225°C and 100 atm in tetrahydrofuran solvent.188 Careful control of reaction conditions is required to avoid the formation of propionic acid, the main byproduct, which is difficult to separate. Small amounts of acetaldehyde are also formed. Acrylates can be produced by the stoichiometric process [Eq. (7.20)], which is run under milder conditions (30-50°C, 1-7 atm). The byproduct NiCl2 is recycled ... 

During these catalytic or stoichiometric processes, possible side reactions do occur which are shown in Scheme 4.3. These explain why the use of more than lequiv. of boronic acid is necessary. Furthermore, during the oxidation of copper(ll) to copper(lll), hydrogen peroxide is produced, which can decrease the yields of the reaction as a result of its reaction with the aryl boronic add. This may also explain why more than 1 equiv. of aryl boronic acid provides enhanced yields [10]. Moreover, the aryl boronic acid can form triaryl boroxines [11], and in doing so forms water, which can be removed from the reaction by molecular sieves. Evans and coworkers postulated that phenolic products would be formed as a result of the competitive arylation of water formed during the reaction process. 

Two copper(ll)-mediated coupling reactions and one Fe(III)-catalyzed reaction are outlined in Scheme 12.22. An example of the stoichiometric use of CuCl in the oxidative coupling of phenol 98 and amine 99 is shown in Equation 12.22-1, Scheme 12.22 [81]. This reaction also demonstrates the potential of copper-mediated processes in the formation of unsymmetrical adducts (with the formation of only minor amounts of homodimers as side products). The authors supported their experimental findings with calculations of the frontier orbital interactions and showed that the HOMO and LUMO interaction with the SOMO of the initially formed radical is favored in differently substituted coupling partners. The success of the reaction also strongly depends on the additive and the yield dropped significantly when the reaction was carried out without the chelating primary amine. 

Ethynylation of ketones is not cataly2ed by copper acetyUde, but potassium hydroxide has been found to be effective (180). In general, alcohols are obtained at lower temperatures and glycols at higher temperatures. Most processes use stoichiometric amounts of alkaU, but tme catalytic processes for manufacture of the alcohols have been described the glycols appear to be products of stoichiometric ethynylation only. 

Copper Hydroxide. Copper(II) hydroxide [20427-59-2] Cu(OH)2, produced by reaction of a copper salt solution and sodium hydroxide, is a blue, gelatinous, voluminous precipitate of limited stabiUty. The thermodynamically unstable copper hydroxide can be kiaetically stabilized by a suitable production method. Usually ammonia or phosphates ate iacorporated iato the hydroxide to produce a color-stable product. The ammonia processed copper hydroxide (16—19) is almost stoichiometric and copper content as high as 64% is not uncommon. The phosphate produced material (20,21) is lower ia copper (57—59%) and has a finer particle size and higher surface area than the ammonia processed hydroxide. Other methods of production generally rely on the formation of an iasoluble copper precursor prior to the formation of the hydroxide (22—26). 

R Cu, or litliium or magnesium homocuprates RfCuM fM = Li, MgX), are fre-quently used, but a number of catalytic processes have also been developed. These processes nornnally utilize a catalytic amount of a copper salt CuY and a stoichiometric amount of an organometallic reagent R M IM = Li, MgX, ZnX, etc.). Hie leaving groups used include balides, esters, sulfonates, and epoxides, among others. 

For definiteness, the oxidation of copper to copper(l) oxide may be considered. Our picture of the process is that cation vacancies and positive holes formed at the Cu O/Oj interface by equation, 1.166 are transported to the Cu/CujO interface where they are destroyed by copper dissolving in the non-stoichiometric oxide. We require an expression for the rate of oxidation. 

Treadwell A process for extracting copper from chalcopyrite by leaching with the stoichiometric quantity of sulfuric acid ... 

Cu(0) species. Alternatively, the Cu(n) species may first undergo oxidation by an external oxidant (or internal redox process) to a Cu(m) intermediate, and then undergo reductive elimination to provide the product and a Cu(i) species. Re-oxidation to Cu(n) would then, in theory, complete the catalytic cycle, but in practice, most reactions of this type have been performed with stoichiometric amounts of the copper reagent. 

As described above, when CuCl is regenerated in the reaction, the process can be catalytic in copper. In other cases, a stoichiometric amount (2 equiv.) of CuCl is used. Although CuCN shows similar reactivity, CuBr and Cul are not so effective as compared to CuCl. Allylation benzene, naphthalene, and anthracene formation, as well as acylation are representative examples, which are described below. 

Copper has long played a dominant role in stoichiometric organometallic reactions in synthesis. Organocuprate mediated conjugate addition reactions are a cornerstone of carbon-carbon bond-forming reactions. Its preeminence has not been overlooked in the search for asymmetric versions of the reaction (134-136). However, the requirement for stoichiometric amounts of the metal has dampened efforts to introduce chirality into this process. 

The baking process has remained much the same until the present day at a stoichiometric ratio of 1 4, phthalic anhydride or phthalic acid reacts with an ammonia releasing compound. The reaction may also start from other suitable materials, such as phthalic acid derivatives, including phthalic acid esters, phthalic acid diamide, or phthalimide. Appropriate ammonia releasing agents include urea and its derivatives, such as biuret, guanidine, and dicyanodiamide. The fact that a certain amount of urea decomposes to form side products makes it necessary to use excess urea. Approximately 0.2 to 0.5, preferably 0.25 equivalents of copper salt should be added for each mole of phthalic anhydride. 0.1 to 0.4 moles of molybdenum salt per mole of phthalic anhydride is sufficient. The reaction temperature is between 200 and 300°C. 

The successes described above notwithstanding, synthetic chemistry in the 1990s was in large measure characterized by catalysis , which encouraged development of organocopper processes that were in line with the times. The cost associated with the metal was far from the driving force that was more (and continues to be) a question of transition metal waste. In other words, proper disposal of copper salt by-products is costly, and so precludes industrial applications based on stoichiometric copper hydrides. 

Application of the manganese and copper catalysed electrochemical reaction between acetic anhydride and styrenes is as efficient as the process using stoichiometric amounts of reagent [27], The reaction between acetic anhydride and buta-... 

The single crystals thus far prepared are too small for many physical property measurements. Also, the two techniques described for preparation of powders result in fine grained (and not sintered) materials which are also not appropriate for many measurements. A different technique, however, was recently developed which produces near theoretical density polycrystalline pellets (56). Stoichiometric mixtures of BaO, K02 and Bi2Os are mixed and melted in N2 gas and quickly quenched onto a copper block under the N2 atmosphere. The process must be performed... 

The use of a stoichiometric amount of palladium acetate, a fact that biases the original oxidative ring closure reactions, can be overcome by the use of an oxidant in the process, which re-oxidizes palladium(O) that is formed in the final step of the ring closure. Such a transformation is presented in 3.78., where an anilino-benzoquinone was ringd closed to give an indoloquinone in the presence of a catalytic amount of palladium acetate and a stoichiometric amount of copper(II) acetate.98... 

Standard textbooks normally paid little attention to gold chemistry compared with that of other metals, even other noble metals. This tendency has changed in the last two decades, with impressive development in its stoichiometric coordination and organometallic chemistry [2]. However, while platinum and palladium have been extensively used as catalysts for a long time, and copper and silver (partners of gold in the periodic table) are used in many large-scale processes, gold was not considered for these types of transformations [7]. 

Extending the definition of n-type and p-type reactions, as defined by Vol kenshtein (21) to the electron transfer step, it would seem that the only reaction given by Equation 1 is a p-type reaction. This reaction would be accelerated by the increase in the value of free hole concentration. On the other hand, all other reactions besides the one given by Equation 1 are n-type and would be accelerated by the increase in free electron concentration. Hydrocarbon oxidation reactions catalyzed by solid oxides are accompanied by oxidation and reduction of the catalyst and the degree of the stoichiometric disturbance in the semiconductor changes. The catalytic process in the oxidation of 2-methylpropene over copper oxide catalyst in the presence of Se02 can be visualized as ... 

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