Carbonates alkaline earth metals

Alkali and alkaline earth metals, Carbon dioxide, carbon tetrachloride, or other chlorinated... 

Conjugate addition of methanol to a,/l-unsaturated carbonyl compounds forms a new carbon-oxygen bond to yield valuable ethers (Scheme 26). Kabashima et al. (12) reported the conjugate addition of methanol to 3-buten-2-one on alkaline oxides, hydroxides, and carbonates at a temperature of 273 K. The activities of the catalyst follow the order alkaline earth metal oxides > alkaline earth metal hydroxides > alkaline earth metal carbonates. All alkaline earth metal oxides exhibited high catalytic activities and, as in alcohol condensations and nitroaldol reactions, their catalytic activities were not much affected by exposure to CO2 and air. 

To neutralize the hydrolysis products the solution is passed through a column (of about 15-cm length and 1-cm width) packed with an anion exchanger (e.g.,anion exchanger from Example 5-10). Neutralization with alkaline earth metal carbonates is to be avoided at all costs, in order to prevent epimerization of glucose to mannose which is favored by complex formation between mannose and alkaline earth metal ions. 

The alkylation reaction of various alkali and alkaline-earth metal carbonates with alkyl halides R(CH2)nX (X = Cl, Br, I) is a primary synthetic procedure in organic chemistry for obtaining various symmetrical and unsymmetrical dialkyl carbonates under phase-transfer conditions in polar aprotic solvents [45]. Excellent yields may be obtained by running the reaction at 383 K in ionic liquids such as... 

Alkali and alkaline earth metals, Carbon dioxide, carbon tetrachloride, and other chlorinated hydrocarbons. (Also prohibit eg. sodium, magnesium, calcium, potassium, water, foam and dry chemical on fires involving these metals—dry sand should powdered aluminum. be available). 

A comparison of the yields of the 16-membered ring compound 56i in cyclization reactions using different metal carbonates is shown in Table 6 In the series of the alkali metal carbonates the best yields are obtained with CS2CO3. Tl ions, which possess the highest polarizability in the periodic system of the elements [51a], led to yields which are comparable to those obtained with Rb2C03 and K2CO3, whereas by using the alkaline earth metal carbonates no reaction could be observed [51]. 

Led by the efforts of Westerhausen and coworkers, a variety of heavy alkaline earth metal zincates or aluminates under formation of alkaline earth metal-carbon contacts have been prepared. Examples include the reaction of trialkylalanes with donor-free calcium i)fr-amides to afford dimeric aluminates, shown in Figure 30. Noteworthy is the planar Ca2N2 center of this complex, in addition to close calcium-aluminum contacts, which may indicate the presence of three-center, two-electron bonding. 

US patent 5,686,380 includes the use of other supports, such as a-alumina, in addition to alkaline earth metal carbonates. At least 50% by weight of the support should be an alkaline earth metal carbonate. 

The solubility products of alkaline-earth metal carbonates according to reaction (3.7.66) were determined by a SAM [333], which consisted in the introduction of the weight of carbonate into the solvent, up to its saturation. The latter was detected by measurements of the e.m.f. of the potentiometric cell (3.7.67). The calibration plot E-p(CO ) ... 

To determine the solubilities of alkaline-earth carbonates in molten KCl-NaCl we used the calibration-like method [350], which consisted in the addition of weights of the substance studied to the solvent with subsequent measurement of the equilibrium e.m.f. Let us consider the applicability of such a technique to our case. The increase in the total initial concentration of alkaline-earth metal carbonate in the solution leads to the growth of ion concentrations on the right-hand side of equation (3.7.66) quite naturally, their product should also increase. Under the constant pressure of C02 (1 atm) the concentration of carbonate ion is proportional to that of O2- according to the simple relationship... 

Indeed, the first argument confirming the formation of pure carbonate precipitate consists of the following. The system considered is under equilibrium conditions, and therefore, it is clear that the solid phase is not only under equilibrium conditions with the melt, but it also contacts with the gas atmosphere. As seen from the discussion above, the equilibrium CO2 pressures over all alkaline-earth metal carbonates are efficiently less than 1 atm, and therefore, the formation of the oxides under these conditions is practically excluded. 

As is seen, the precipitation begins at rather high concentrations of the carbonates added. The comparison of oxide solubility products taken from the literature with the products mMe2+m0i- in the saturated solutions considered in the present work, shows that in all cases the solutions are unsaturated with respect to the corresponding oxides. Hence, we can conclude that in molten KCl-NaCl saturated with C02, alkaline-earth metal carbonate precipitation... 

Introduction Alkaline-earth metal carbonates and especially calcite are the most popular reactants in studying the decomposition kinetics of solids. This is caused, not only by the use of carbonates as mineral raw materials for some industrial processes (in particular, production of lime), but also by the fact that the decomposition of calcite is a convenient model reaction for studying the kinetics and mechanism of solid-state reactions as a whole. An enormous number of papers, summarized in part in several monographs [43, 45, 99] and reviews [100-102], deal with the decomposition of carbonates. A series... 

Despite the many-fold differences in the molar enthalpies (parameter E) for calcite and other alkaline-earth metal carbonates, measured on the basis of different kinetic models and, above all, under different conditions (in a vacuum and in the presence of CO2), the enthalpies measured in the equimolar and isobaric modes by the third-law method (Table 16.58) appear to be reasonably consistent (the largest difference, by a factor of 1.13, is... 

Partially aromatic polyamide compositions that contain an alkaline earth metal carbonate exhibit an excellent adhesion to metal coatings which are produced by electroless or electrolytic plating [66,67]. 

Hydroxides of alkali metals and alkaline earth metals, carbonates of... 

---