Compounds of alkaline earth metals

Thinking Critically Remember that most compounds of alkaline earth metals do not dissolve easily in water. What is the white solid that formed when washing soda was added to the solution of magnesium sulfate ... 

The development of volatile compounds of alkaline-earth metals has attracted attention because of the need for these compounds as precursors for the preparation of thin films by chemical gas phase methods. Hatanpaa and coworkers [200] characterized the effect of ancillary ligands on the structural and thermal properties of several [Mg(thd)2(A)] complexes, in which A is a neutral Lewis-base ligand. They showed that the evaporation processes of diamine adducts contain two overlapping steps, the first step associated with the evaporation of amine and the second with the evaporation of [Mg2(thd)4] dimer. All the complexes containing amines evaporated almost completely, but the complex which contained 1,2-ethanediol, was thermally unstable and decomposed when heated. At temperatures below the dissociation temperature, all adducts of diamines appeared to evaporate intact. 

The coordination catalysts for these reactions are diverse. They can be compounds of alkaline earth metals, like calcium amide, or calcium amide-alkoxide. They can also be Ziegler-Natta-type catalysts. These can be alkoxides of aluminum, magnesium, or zinc combined with ferric chloride. Others are reaction products of dialkylzinc with water or alcohol. They can also be bimetallic //-oxoalkoxides, such as [(RO)2A102]Zn. Other catalysts are aluminum or zinc metalloporphyrin derivatives (see Fig. 4.1). 

Standard Enthalpy of Formation of Compounds of Alkaline-earth Metals at 25°C (kJ mole- )... 

Filtration or settling after addition of compounds of alkaline earth metals [32— 36]... 

Diazotization of the aminosulfonic acid and subsequent coupling onto the sodium salt of 2-hydroxy-3-naphthoic acid initially affords the monoazo compound in the form of its soluble sodium salt. Subsequent reaction with chlorides or sulfates of alkaline earth metals or with a manganese salt, frequently in the presence of a dispersion agent, or rosin or its derivatives, at elevated temperature yields the insoluble BONA pigment lake. 

The alkali metal suboxides are well understood in terms of formation, structure, and properties, yet we still face some unsolved problems that will also be addressed in the following. In contrast, the first suboxide of barium came to light only recently [24], and one has to see whether this compound is the tip of another iceberg, as turned out to be the case with the subnitrides of alkaline earth metals. 

Peterson and Scarrah 165) reported the transesterification of rapeseed oil by methanol in the presence of alkaline earth metal oxides and alkali metal carbonates at 333-336 K. They found that although MgO was not active for the transesterification reaction, CaO showed activity, which was enhanced by the addition of MgO. In contrast, Leclercq et al. 166) showed that the methanolysis of rapeseed oil could be carried out with MgO, although its activity depends strongly on the pretreatment temperature of this oxide. Thus, with MgO pre-treated at 823 K and a methanol to oil molar ratio of 75 at methanol reflux, a conversion of 37% with 97% selectivity to methyl esters was achieved after 1 h in a batch reactor. The authors 166) showed that the order of activity was Ba(OH)2 > MgO > NaCsX zeolite >MgAl mixed oxide. With the most active catalyst (Ba(OH)2), 81% oil conversion, with 97% selectivity to methyl esters after 1 h in a batch reactor was achieved. Gryglewicz 167) also showed that the transesterification of rapeseed oil with methanol could be catalyzed effectively by basic alkaline earth metal compounds such as calcium oxide, calcium methoxide, and barium hydroxide. Barium hydroxide was the most active catalyst, giving conversions of 75% after 30 min in a batch reactor. Calcium methoxide showed an intermediate activity, and CaO was the least active catalyst nevertheless, 95% conversion could be achieved after 2.5 h in a batch reactor. MgO and Ca(OH)2 showed no catalytic activity for rapeseed oil methanolysis. However, the transesterification reaction rate could be enhanced by the use of ultrasound as well as by introduction of an appropriate co-solvent such as THF to increase methanol solubility in the phase containing the rapeseed oil. 

Reaction with sulfuric acid yields monoperoxysulfuric acid. Reactions with many alkaline earth compounds yield peroxides of alkaline earth metals ... 

The cyclocondensation reaction was used in the synthesis of phosphane complexes of alkaline earth metals. For example, reaction of BeCl2 with 2equiv of Li[C(PMe2)2(SiMe3)] afforded compound 57 as colorless crystals (Equation 10). Magnesium and calcium complexes were similarly prepared <1998EJI905>. 

The addition of an alkaline earth metal enolate A to a carbonyl compound is always an exer-gonic process irrespective of whether the enolate is derived from a ketone, an ester, or an amide and whether the carbonyl compound is an aldehyde or a ketone (Figure 13.44, top). One of the reasons for this exergonicity hes in the fact that the alkaline earth metal ion is part of a chelate in the alkoxide B of the aldol addition product. The driving forces for the additions of alkaline earth metal enolates of esters and amides to carbonyl compounds are further increased because the aldol adducts B are resonance-stabilized, whereas the enolates are not. 

A special group of inhibitors are those substances which suppress the decomposition of hydrogen peroxide in alkaline solutions, which are used for bleaching purposes or for preparation of addition compounds of hydrogen peroxide. Good stabilizers for such solutions are e. g. magnesium orthosilicate, water glass and phosphates of alkaline-earth metals. 

Cement binders are based on silicates, aluminates, aluminium silicates, aluminium ferrites of alkaline earth metals (mainly calcium). The hydration of these compounds or their mixtures with the formation of... 

Chemical interferences occur when the analyte forms a thermally stable compound with a molecular or ionic species present in the sample solution. Examples include the suppression of alkaline earth metals due to the presence of phosphate, silicate or aluminate in the sample solution in the air-acetylene flame. The most well-known example of this is the absorption signal suppression that occurs for Ca at 422.7 nm owing to increasing amounts of phosphate. This signal suppression is due to the formation of calcium pyrophosphate, a thermally stable compound in the flame. 

Compounds of the earth metals and alkaline earth metals Compounds of the heavy metals... 

What is the oxidation number of alkaline earth metals in their compounds Of alkali metals (20.1)... 

The reactions of fluorine with aqueous solutions of alkaline-earth-metal chlorides give different products depending on the Group II metal. With MC12 (M = Ca, Sr, or Mg), fluorination leads directly to MF2, but with BaCl2 the compound BaF(HF2) is formed. An intermediate step in the reaction involves the formation of BaCIF followed by substitution of Cl by HF2.77... 

The standard X-ray diffraction patterns for 57 compounds have been collected. The data comprise Miller indices, interplanar spacings, and lattice constants for inorganic compounds, solid solutions of alkali-metal halides and of alkaline-earth metal nitrates. ... 

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