Hydroxides alkaline earth metals

Chlorine reacts with alkaU and alkaline earth metal hydroxides to form bleaching agents such as NaOCl ... 

Composite Oxyalkoxides. Composite oxyalkoxides can be prepared by reaction of tetraalkyl titanates and alkaline-earth metal hydroxides. These oxyalkoxides and their derivatives can be hydroly2ed and thermally decomposed to give alkaline-earth metal titanates such as barium titanate (150). 

This is a quite remarkable result, as the chemoselective hydrogenation of geraniol over a heterogeneous catalyst has rarely been reported. It can be carried out over platinum containing zeolite (9), over Pt/Al203 modified with carboxylic acids (10), over Ni/diatomaceous earth and alkali hydroxides or carbonates (11) or NiRaney and alkali or alkaline earth metal hydroxides (12), yields never exceeding 85%. 

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. 

According to the Lewis theory, alkaline earth metal hydroxides are weaker bases than their oxides, the order of the strength of the basic sites being Ba(OH)2> SrO(OH)2 > Ca(OH)2 > Mg(OH)2. The hydroxides have been used recently as solid catalysts for organic transformations, such as the conjugate addition of methanol to a, S-unsaturated carbonyl compounds (12), cyanoethylation of alcohols (163,164), and transesterification reactions (166,167,171,172) which are described above. The extensive work of Sinisterra et al. (282) on the number and nature of sites and on the catalytic activity of the most basic alkali metal hydroxide, Ba(OH)2, is emphasized. It was found that commercial barium hydroxide octahydrate can be converted into... 

A. Catalytic Reactions on Alkaline Earth Metal Hydroxides A.l. Aldol Condensations... 

As demonstrated in previous sections, unique reactivity and selectivity have been often observed in aqueous media, but one of the big issues is the stability of catalysts in water. To overcome this, efficient catalysts that are stable and can work well in aqueous media were searched for, and metal hydroxides were found. With the exception of alkaline and alkaline earth metal hydroxides, these have not... 

Dialysis experiments" have shown that Ca2 , Mg2 , Ba2 , and Sr2 form soluble chelates in aqueous alkaline solution with D-galactose, D-glucose, D-fructose, D-arabinose, D-ribose, maltose, and lactose. The absence of any precipitation of alkaline-earth metal hydroxide when an aqueous solution containing D-fructose and an alkaline-earth metal salt is made alkaline... 

Complexes of Carbohydrate with Alkaline-earth Metal Hydroxide ... 

A review by Mackenzie and Quin,19 on complexes of alkaline-earth metal hydroxides, is recommended to those who desire a more thorough description of the methods of preparation. 

In summary, the reaction between an alkali metal alkoxide and a poly-hydroxy compound in hot alcoholic media produces an alcoholate and, possibly, a small proportion of alkoxide adduct however, the conditions governing the ratio of alcoholate to adduct have not yet been well defined. Reactions with alkali metal hydroxides and cyanides produce mixtures (of alcoholate and adduct) that consist mainly of alcoholate. Occurrence of reactions between alkaline-earth metal hydroxides and polyhydroxy compounds in anhydrous alcoholic media has not been reported. 

There have been no studies of adducts of alkaline-earth metal hydroxides with a view to determining the position, or positions, of attachment of alkaline-earth metal hydroxide on carbohydrates. 

Now let s consider strong and weak bases. The common strong bases are easy to remember they are the alkali metal and alkaline earth metal hydroxides and oxides, such as calcium oxide (Table J.l). When the oxide dissolves in water, the oxide ions, O2-, accept protons to form hydroxide ions ... 

The alkaline earth metal hydroxides M(OH)2 (M = Mg, Ca, Sr, or Ba) are also strong bases ( 100% dissociated), but they give lower OH- concentrations because they are less soluble. Their solubility at room temperature varies from 38 g/L for the relatively soluble Ba(OH)2 to 10-2 g/L for the relatively insoluble Mg(OH)2. Aqueous suspensions of Mg(OH)2, called milk of magnesia, are used as an antacid. The most common and least expensive alkaline earth hydroxide is Ca(OH)2, which is used in making mortars and cements. It is called slaked lime because it is made by treating lime (CaO) with water. Aqueous solutions of the slightly soluble Ca(OH)2 (solubility 1.3g/L) are known as limewater. 

For the quantitative deprotonation of nitroalkanes and active-methylene compounds, there is no need to employ the heavy artillery of lithium amides. Rather, it suffices to employ alkaline earth metal alkoxides or alkaline earth metal hydroxides. In addition, equilibrium reactions between these C,H acids and amines form enough enolate to initiate enolate reactions. 

Remember what we discussed in the context of Figure 13.44 ketones usually do not undergo aldol additions if they are deprotonated to only a small extent by an alkaline earth metal alkox-ide or hydroxide. The driving force behind that reaction simply is too weak. In fact, only a very few ketones can react with themselves in the presence of alkaline earth metal alkoxides or alkaline earth metal hydroxides. And if they do, they engage in an aldol condensation. Cyclopentanone and acetophenone, for example, show this reactivity. 

Reaction of tetraisopropyl titanate with an alkali or alkaline earth metal hydroxide in alcohol solution to form a soluble intermediate ... 

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