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  Home >> Chemistry Dictionary >>Aluminates - Aluminium Alkoxides

Alumina.
Aluminium oxide

Aluminates.
A group of compounds formally containing the
AI3+ ion in anionic hydroxy-or-oxo-complexes. Species containing [AI(OH)4]- and [(HO)Al3-Anionic Hydroxy-O-Al(OH)3]2- and higher polymers (cationic hydroxy species are also known—see aluminium hydroxide) are formed from Al3+ aq solutions at high pH. Solid salts are formed by crystallization or precipitation.

Aluminium.
A silvery white metal. It is very light metal, sp. g, 2.70 and good conductor of electricity. It is recovered pure and in quanity from its oxide by electrolytic reduction. It reacts with boiling solution of caustic alkalies to give aluminate and hydrogen as
2Al + 2NaOH + 2H2O = 2NaAlO2 + 3H2μ

Aluminium foil is used for packing fine article, e.g., sweets photographic and pharmaceutical products. Aluminium cables are preferred to those of copper on account of their lightness and low cost. Aluminium and its alloys are light and durable. Therefore, they are used in automobiles and air craft industries.
Symbol: Al; a.n. 13; m.p. 659.8 °C; b.p. 1800°C; r.d. 2.702

Pure aluminium is soft and ductile but its strength can be increased by work-hardening. A large number of alloys are manufactured; alloying elements include copper, manganese, silicon, zinc, and magnesium. Its lightness, strength (when alloyed), corrosion resistance. and electrical conductivity (62% of that of copper) make it suitable for a variety of uses, including vehicle and aircraft construction, building (window and door frames,) and overhead power cables. Although it is the third most abundant element in the earth’s crust (8.1% by weight) it was not isolated until 1825 by H.C. Oersted (1777-1851).

Aluminium alkoxides.
 Al(OR3). Formed by reaction between Al and the alcohol in the presence of HgCl2 as catalyst or from AlCl3 and RONa. The alkoxides are polymeric [Al(OBut)3]2, [Al(OPr1)3]4, fairly low melting solids readily hydrolysed by water. Used as specific reducing agents for C = O groups, for formation of esters from aldehydes by the Cannizzaro reaction [Al(OPr1)3, oxidation of secondary alcohols to ketones in the presence of excess Me2CO (Oppenauer oxidiation —Al(OBut)3) and with co-catalysts, e.g., TiCl4, as olefine polymerization catalysts. The most important aluminium alkoxides are Al(OBut)3 and Al(OP1)3

Aluminium alloys.
Important materials for their combination of light weight, strength and generally good corrosion resistance.

Aluminium bromide,
AlBr3. Very similar to AlCl3, formed from Al plus Br2 or Br2 over Al2O

3 plus carbon. forms hydrates.

Aluminium-t-butoxide, aluminium-t-butylate,
Al(OH(CH3)3)3, Al(OBut)3

Aluminium chloride.
Aluminium trichloride, AlCl2 is the stable chloride at room temperature. Colourless or yellowish solid d-2.44, sublimes 1800C. Soluble in water and many organic solvents. Prepared from Al and Cl2 or HCl or Cl2 over Al2O3 plus carbon. Forms complexes AlCl3.L with e.g., H3O, H2S and amines, and [AlCl4]- and [Al2Cl7]- complex with chloride ions. Solid AlCl3 contains octahedrally co-ordinated Al, dimeric, [Cl2Al(μ-Cl)2AlCl2] in the gas phase. Forms volatile, chloride-bridged species with many halides. Used as a source of aluminium slats, and (also in the laboratory) in, e.g. Friedel-Crafts syntheses.
Aluminium monochloride, AlCl, is formed at very high temperatures from AlCl3 and Al. The reaction is reversed on cooling.

 

           

 
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