Cobalt acetate, decomposition

The solvent acid also affects the oxidation rate since the rate with cobalt acetate (Table II) is reduced in propionic or butyric acids in contrast to the increase in the hydroperoxide decomposition rate. 

Since copper (II) does not significantly catalyze the peracetic acid decomposition, we have studied the kinetics of this reaction only in the presence of manganese and cobalt acetates. 

With cobalt as catalyst the plot of log [peracetic acid] vs. time was linear for each cobalt acetate concentration. The first-order rate constants obtained at different cobalt concentrations (k2 ) were plotted as a function of total cobalt (Cot) concentration, and the plot indicates a first-order dependence on total cobalt as shown in Figure 3. The experimental rate law for the cobalt-catalyzed decomposition is thus ... 

With manganese and cobalt acetate the reaction of peracetic acid with acetaldehyde is very fast, and AMP is not detected. By comparing our rates with literature values of k17, k.17, and k18 we cannot propose a mechanism in which the only role of the metal ion is to catalyze the decomposition of AMP. The experimental rates in the presence of either manganese or cobalt acetates are much faster than the noncatalytic rate of formation of AMP. Thus, AMP per se is probably not an intermediate in the presence of these catalysts. 

The only definite borate hydrates of cobalt are the CoO - 3B203 - 8H20 and CoO 3B203 10H2O compounds. The octahydrate is prepared by evaporation of acetic acid from cobalt acetate-boric acid mixtures, or by mixing aqueous solutions of cobalt chloride, borax, and boric acid (206). The 1 3 7.5 borate can form as a solid solution and, in the presence of 3% boric acid, affords the decahydrate (117). The crystal structure determination of this 1 3 10 compound shows it to possess the hexaborate ion (380). The IR spectra (402) and thermal decomposition (396) of these compounds have been determined. 

According to the authors, cobalt acetate catalyzes the decomposition of peracid and the related reaction rate is more or less proportional to the concentration of CoAc2. This appears to imply a chain termination reaction other than one between peroxidic radicals. 

At high temperature thermolysis (1270K) of cobalt acetate with PS, PAA, and PMVK present, the metal clusters that are catalyzing an oxygen electrolytic reduction had formed [98]. As the thermal decomposition of silver trifluoro-acetyl-acetonate at 613 K occurs in polyimide film [99-101], the film becomes metallized (a structure called film on film ) and a nanocomposite is formed with high surface conductivity and light reflection coefficient (above 80%). 

Barium oxide and carbonate are known to catalyze the formation of CHP. Cobalt acetate catalyzes both the formation and decomposition of CHP. Other alkylaromatics react... 

Cobalt acetate (Co(COOCCH3)2, Aldrich) and dodecanethiol (CH3(CH2)n)SH, Aldrich, 99- -%) have been used for the synthesis of cobalt mercaptide. Cobalt acetate was dissolved in ethanol under stirring and a solution of dodecanethiol in ethanol was added to this solution drop by drop. Then the precipitate was isolated by vacuum filtration and washed by acetone. Cobalt mercaptide was quite soluble in nonpolar organic solvents and its thermal decomposition gave a pure CoS phase. 

PTFE increases the decomposition temperature of cadmium oxalate trihy-drate. Moreover, the products of cadmium complex degradation, in turn, increase the temperature at which an intensive degradation of PTFE begins. The thermal decomposition of the highly dispersed copper formate leads to the formation of a metal-polymer composition (20-34% Cu). The maximum on the nanoparticles granulometric composition curve corresponds to 4nm. No chemical interaction between the components was observed. The decomposition of a fine dispersion of palladium hydroxide in polyvinyl chloride (PVC) results in spatial structures with highly dispersed Pd particles (S = 26 m g ) in the nodes. This process increases in the temperature required for complete dehydrochlorination of PVC. The thermolysis of cobalt acetate in the presence of PS, PAA, and poly(methyl vinyl ketone) proceeds... 

The oxidation of benzaldehyde in the presence of cobaltous acetate has been studied in detail by Marta, Boga and co-workers [226-230]. A radical chain mechanism was involved and inhibition of this reaction both by jS-naphthol and by cobaltous ion at high concentration, have been observed. The initiation step was found to involve the decomposition of a Co CPhCOaH) complex to give Co species which were the reactive intermediates. The rate constant and heat of formation of the Co (PhC03H) complex were determined. Bawn and Jolley [225] have shown that at low Co concentration, the oxidation of benzaldehyde follows rate law, equation (177). 

Richardson [331-333] has studied the catalytic decomposition of tertAmiyl hydroperoxide by cobalt acetate in acetic acid. The principle products were again r -butyl alcohol and oxygen. Results of kinetic studies, ESR measurements and deuterium isotope effects are in agreement with a mechanism involving attack by r -butylperoxy radical on a dimeric cobalt-hydroperoxide complex, equation (206) [333]. 

Redox reactions. The chemical reduction of metal salts by sodium boron hydride is a common procedure in the preparation of metals and metal alloys. Nanoparticles of iron, FeZrB, FeCoB and FeCoB have been obtained from the corresponding sulphate salts, and NdFeB compounds from neodymium and iron chloride salts. Cobalt nanoparticles have been prepared from cobalt acetate using 1,2 dodecanediol as a mild reducing agent. FePt nanoparticles are produced by the decomposition of iron pentacarbonyl and the reduction of platinum tetrachloride complexes in an organic solvent. Redox reactions can also be produced by electrochemical methods, or in the solid phase. ... 

The higher iodides, however, tend to be unstable and decomposition occurs to the lower iodide (PI5 -> PI3). Anhydrous chlorides and bromides of some metals may also be prepared by the action of acetyl (ethanoyl) halide on the hydrated ethanoate (acetate) in benzene, for example cobalt(II) and nickel(II) chlorides ... 

Table HI illustrates that cobalt behaves as an extraordinary catalyst in its reaction with MCPBA increasing the rate by a factor of 400,000 and reducing the activation from 27 to 9.5 kcal/mol. However, cobalt also greatly enhances the selectivity in the system (Table HI). The yield to the desired acid increases from 89% to 100% with the expected decrease in the by-products. The thermal decomposition of MCPBA, equation 2, releases the hydroxyl radical which can easily attack the acetic acid forming carbon dioxide and methyl acetate.

The thermal decomposition of MCPBA is slow and unselective. When cobalt catalyzed, the initial reaction is very fast and selective but the reaction is Wdered by the re-arrangement of Co(in)a to Co(III)s and by the slow reaction with m-chlorotoluene. These reactions are also characterized by a high steady state concentration of Co(III). High concentrations of Co(III) are not desirable because Co(III) is known to react with the acetic acid solvent and also decarboxylate aromatic acids (2). 

Peracetic acid decomposition kinetics in the presence of cobalt or copper acetates were studied in the same apparatus used for the manganese-catalyzed reaction. However, in these studies it was used as a batch reaction system. The reactor was charged with peracetic acid (ca. 0.5M in acetic acid) and allowed to reach the desired temperature. At this time the catalyst (in acetic acid) was added. Samples were withdrawn and quenched with potassium iodide at measured time intervals. 

Oxidation of Acetaldehyde. When using cobalt or manganese acetate the main role of the metal ion (beside the initiation) is to catalyze the reaction of peracetic acid with acetaldehyde so effectively that it becomes the main route to acetic acid and can also account for the majority of by-products. Small discrepancies between acetic acid efficiencies in this reaction and those obtained in acetaldehyde oxidation can be attributed to the degradation of peracetoxy radicals—a peracetic acid precursor— by Reactions 14 and 16. The catalytic decomposition of peracetic acid is too slow (relative to the reaction of acetaldehyde with peracetic acid) to be significant. The oxidation of acetyl radical by the metal ion in the 3+ oxidation state as in Reaction 24 is a possible side reaction. Its importance will depend on the competition between the metal ion and oxygen for the acetyl radical. 

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