Aluminum cationic

The four oxygen anions in the tetrahedron are balanced by the -i-4 oxidation state of the silicon cation, while the four oxygen anions connecting the aluminum cation are not balanced. This results in -1 net charge, which should be balanced. Metal cations such as Na", Mg ", or protons (H" ) balance the charge of the alumina tetrahedra. A two-dimensional representation of an H-zeolite tetrahedra is shown ... 

You may be surprised to learn that many metal cations act as weak acids in water solution. A 0.10 M solution of A12(S04)3 has a pH close to 3 you can change the color of hydrangeas from red to blue by adding aluminum salts to soil At first glance it is not at all obvious how a cation such as Al3+ can make a water solution addic. However, the aluminum cation in water solution is really a hydrated species, A1(H20)63+, in which six water molecules are bonded to the central Al3+ ion. This spedes can transfer a proton to a solvent water molecule to form an H30+ ion ... 

Minerals often contain more than one cation or anion. For example, apatite, Caj ( 04)3 F, contains both phosphate and fluoride anions. Beryl, Bc3 AI2 Sig Oig, contains beryllium and aluminum cations as well as the Sig Oig polyatomic anion. An even more complicated example is gamierite, (Ni,Mg)e Si4 0io(OH)2,... 

In reality, the increase of the rate of dissolution due to increasing hydrogen ion concentration should increase the overall rate over that of the dissolution via direct transfer of aluminum cation through the O/S interface discussed above. 

There have been a small number of theoretical studies of cation ordering in LDHs. First principles molecular dynamics calculations [43] on [Mg3Al(OH)8]Cl LDHs discussed in Sect. 3.2.6 suggested that structures with adjacent aluminum cations were energetically less favorable than one without, although the chosen arrangement for the latter lacked either hexagonal or rhombohedral supercell. 

Micas are also composed of Si-0 tetrahedra. The anionic charge on the silicate sheet is the result of the replacement of silicon by aluminum. Cations such as potassium are interspaced between these negatively charged sheets. Some micas are used in construction and electrical engineering applications. Synthetic mica is manufactured on a large scale for industrial consumption in coatings, as fillers, etc. Micas are one of the many layered Si-0-intense materials found in nature. 

On nitrided aluminophosphates, AlPON, Massinon et al. [206] observed on a series of six samples with increasing nitrogen contents a good correlation between the catalytic activity in the Knoevenagel condensation reaction and the amount of surface NH, species (1 < x < 4) quantified by the Kjeldahl method. The authors suggest that those species are not the only active species and evoke an additional role of the nitride ions in the reaction [206] on the other hand, Benitez et al. [207] suggest hydroxyls linked to aluminum cations in the vicinity of terminal P-NH2 groups as basic centers. 

SIX-COORDINATE ALUMINUM CATIONS BASED ON SALEN LIGANDS... 

Six-Coordinate Aluminum Cations Based on Salen Ligands... 

When aluminum chloride salt is dissolved in water, aluminum (111) cations become surrounded by clusters of six water molecules to form a hexahydrated aluminum cation, Al(H20)g ". Being a Group lllA metal, aluminum easily gives up its valence electrons. The oxygen atom in water possesses two lone pairs. What kind of bonding most likely occurs between the aluminum and the hydrating water molecules ... 

The resulting hydrogen sites are envisioned to undergo hydrolysis and neutralization as shown in Equations 5 and 6, respectively. Then the aluminum cation formed in Equation 6 is replaced by ammonium ion... 

The colloidal silica dispersions are destabilized with hydrolyzed Al(III) primarily because of adsorption of polyhydroxo aluminum cations on the colloid surface which reduces the incipiently negative surface potential of Si02 colloids (adsorption coagulation). The pertinent solution variables describing the destabilization reaction are pH, total aluminum concentration Ct, and the ratio of aluminum dosage to the colloid surface concentration S. 

Clays are natural compounds of silica and alumina, containing major amounts of the oxides of sodium, potassium, magnesium, calcium, and other alkali and alkaline earth metals. Iron and other transition metals are often found in natural clays, substituted for the aluminum cations. Oxides of virtually every metal are found as impurity deposits in clay minerals. 

Next, the mechanism of the Type II reactions is discussed. To discriminate one of the enantiofaces of the acceptor it is desirable to place and to activate the electrophiles in a chiral environment. At the same time, effective activation of the Michael donor is required. In Shibasaki s ALB-catalyzed reaction (Scheme 3), it was proposed that the aluminum cation functioned as a Lewis acid to activate enones at the center of the catalyst, and that the Li-naphthoxide moiety deproton-ated the a-hydrogen of malonate to form the Li enolate (Scheme 9). Such simultaneous activation of both reactants at precisely defined positions became feasible by using multifunctional heterobimetallic complexes the mechanism is reminiscent of that which is operative in the active sites of enzymes. The observed absolute stereochemistry can be understood in terms of the proposed transition state model 19. Importantly, addition of a catalytic amount of KOt-Bu (0.9equiv. to ALB) was effective in acceleration of the reaction rate with no deterioration of the... 

These are a series of magnesium aluminum hydroxycarbonates with varying magnesium to aluminum ratios between 1.5 and 3.0g-atoms of magnesium to 1 g-atom of aluminum. They have layers of magnesium hydroxide interspersed with aluminum cations and carbonate anions. They show similar flame-retardant activity and thermal stability to ATH, but their higher cost currently limits their potential use. 

Figure 47 Polyamine-ligated aluminum cation accommodated by the fused five-membered rings.

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