Copper formate, decomposition mechanism

In this study, we extend the range of inorganic materials produced from polymeric precursors to include copper composites. Soluble complexes between poly(2-vinylpyridine) (P2VPy) and cupric chloride were prepared in a mixed solvent of 95% methanol 5% water. Pyrolysis of the isolated complexes results in the formation of carbonaceous composites of copper. The decomposition mechanism of the complexes was studied by optical, infrared, x-ray photoelectron and pyrolysis mass spectroscopy as well as thermogravimetric analysis and magnetic susceptibility measurements. 

The EfZ ratio of stilbenes obtained in the Rh2(OAc)4-catalyzed reaction was independent of catalyst concentration in the range given in Table 22 357). This fact differs from the copper-catalyzed decomposition of ethyl diazoacetate, where the ratio diethyl fumarate diethyl maleate was found to depend on the concentration of the catalyst, requiring two competing mechanistic pathways to be taken into account 365), The preference for the Z-stilbene upon C ClO -or rhodium-catalyzed decomposition of aryldiazomethanes may be explained by the mechanism given in Scheme 39. Nucleophilic attack of the diazoalkane at the presumed metal carbene leads to two epimeric diazonium intermediates 385, the sterically less encumbered of which yields the Z-stilbene after C/C rotation 357,358). Thus, steric effects, favoring 385a over 385 b, ultimately cause the preferred formation of the thermodynamically less stable cis-stilbene. 

The mechanism of the process is that the polymer reactive centers promote the metal nucleation and aggregation, after which the thermolysis occurs and the metal-containing substance is redistributed. The maximum amount of copper being introduced in PS through a common solvent is about 10%. At the same time, the polymer presence increases the temperature of cadmium trihydrate-oxalate decomposition [97], and the decay products increase the initial temperature of PETF intensive destruction. The copper formate thermal decomposition in the highly dispersed PETF presence allows us to produce a metallopolymeric composition (20-34% of copper) where the NP size distribution is maximal at 4nm, without any chemical interaction between the components. 

A 1989 review of the literature by Clarke gave many examples which support the importance of copper-silicon rich phases near the surface during the MCS reaction. Clarke noted that CusSi (eta phase) forms above 880 °C but will form at 350 °C in the presence of chloride ion. Methyl chloride reacts with copper to form copper chloride which then serves as the chloride source needed for formation of the eta phase, thus explaining the shorter induction period obtained using copper chloride vs other copper catalysts. The mechanism of replacement of silicon from the surface is by diffusion of copper into the bulk silicon to reform a copper-silicon rich surface. Iron-silicon phases stabilize the eta phase and metal promoters catalyze chloride transfer, e.g. see equation 2. Silicon also reacts with ZnCl2 and AICI3. Excess zinc causes unproductive decomposition of MeCl to give methane. Finally, Clarke presented data that ruled out the importance of methyl radicals in the MCS reaction. 

Three different crystalline forms of anhydrous copper(II) formate have been identified [1033] and these three variations provide a convenient group of reactants for an investigation of the influence of lattice structure on the kinetics and mechanisms of the decomposition. Erofe ev and Kravchuck [1034] showed that kinetic characteristics for the decompositions of two of these forms were appreciably different, an effect attributed to different relative dispositions of the cations in the two reactant structures. 

Fig. 18. Schematic representation of the mechanism of decomposition of copper(II) formate, proposed by Galwey et al. [97], (Reproduced, with permission, from Journal of Physical Chemistry.)...

The rate of peroxide decomposition and the resultant rate of oxidation are markedly increased by the presence of ions of metals such as iron, copper, manganese, and cobalt [13]. This catalytic decomposition is based on a redox mechanism, as in Figure 15.2. Consequently, it is important to control and limit the amounts of metal impurities in raw rubber. The influence of antioxidants against these rubber poisons depends at least partially on a complex formation (chelation) of the damaging ion. In favor of this theory is the fact that simple chelating agents that have no aging-protective activity, like ethylene diamine tetracetic acid (EDTA), act as copper protectors. 

This may occur by free-radical formation, especially in the presence of transition-metal ions such as those of iron or copper. Similar mechanisms can result in the decomposition of peroxide but there are means of controlling or avoiding this problem. 

Dowden and Reynolds observed that the rates of decomposition of hydrogen peroxide decreased from pure copper to copper-nickel alloys, thus suggesting that negative ion formation takes place in the heterogeneous catalytic reaction, in agreement with the Haber and Weiss mechanism based on catalysis in solution. 

Since copper (II) does not catalyze the AMP decomposition, the mechanism for acetic acid formation in the presence of copper (II) acetate is indicated by Reactions 17 and 18. 

Fig. 13.22. Mechanism of the Pd(0)-catalyzed arylation of a copper acetylide. Step 1 formation of a 7T complex between the catalytically active Pd(0) complex and the arylating agent. Step 2 oxidative addition of the arylating agent and formation of a Pd(II) complex with a

Kinetic evidence for synergic adsorption of carbon monoxide and water on the low-temperature shift catalyst Cu/ZnO/Fe203 was obtained by van Herwijnen and deJong (113), and IR spectra of surface formate were detected on several oxide catalysts, including CuO/MgO, at temperatures as low as 20 JC and pressures of 20 Torr, as reported by Davydov et al. (104). Decomposition of the surface formate to C02 and H2 occurred at 100-150°C over the Cu/MgO catalyst and at 250 300°C over the MgO catalyst, and the promotion effect of copper was attributed to the formation and decomposition of a labile surface formate (HCOO)2Cu. Ueno et al. (117) have shown earlier that surface formates are formed on zinc oxide, from CO and H20 as well as from C02 and H2, and hence an associative mechanism of the shift and reverse-shift reaction, involving formate intermediate, is believed to operate on many oxide catalysts. 

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