Description
Aluminum bromide is a light-yellow colored liquid or colorless monoclinic crystals. Very corrosive to skin, eyes and mucous membranes, moderately poisonous. Aluminum bromide is an inorganic binary compound. The substance is a salt of aluminum and bromine-hydrogen acid. it exists in form of a dimer. The commercial use of aluminum bromide is relatively insignificant at the moment. Aluminum bromide belongs as the main component to xylene electrolytes for electric precipitation of aluminum coatings. The anhydrous aluminum bromide is used in organic synthesis, in particular, in the alkylation reaction or Friedel-Crafts reaction by analogy with aluminum chloride.This compound can be catalyst in a bromo-alkanes` isomerizating reaction. Aluminum bromide can also be used as bromating agent, for example, in a reaction with chloroform.
Uses
The anhydrous form is used as a catalyst for the Friedel-Crafts alkylation reaction. Its catalytic activity is similar to anhydrous AlCl3. Commercial applications, however, are few.
Preparation
Prepared from bromine and metallic aluminum.
2Al + 3Br2 →Al2Br6 (anhydrous)
Reactions
Decomposes upon heating in air to bromine and metallic aluminum.
2 AlBr3→ 2Al + 3Br2
Reacts with carbon tetrachloride at 100°C to form carbon tetrabromide;
4AlBr3 + 3CCl4 → 4AlCl3 + 3Br4
Reaction with phosgene yields carbonyl bromide and aluminum chlorobromide;
AlBr3 + COCl2 → COBr2 + AlCl2Br
Reacts violently with water; absorbs moisture forming hexahydrate, AlBr3⋅6H2O
Chemical Properties
White Crystalline Powder
Physical properties
Colorless crystalline solid in anhydrous form; melts at 97.5°C; boils at 256°C;density 3.01 g/cm3 at 25°C; moisture sensitive, fumes in air; soluble in water (reacts violently in cold water, and decomposes in hot water, alcohols, acetone, hexane, benzene, nitrobenzene, carbon disulfide and many other organic sol_x0002_vents).
Uses
Anhydrous: bromination, alkylation, and isomerization catalyst in organic synthesis.
Uses
Alkylation, bromination and isomerization catalyst in organic synthesis.Aluminum bromide acts as a strong Lewis acid and is used in Lewis acid-promoted reactions such as epoxide ring openings. It is used as a catalyst for Friedel-Crafts alkylation reaction. It also finds application in bromination and isomerization reactions in organic synthesis. It is also used in polymerization reaction to prepare poly(o-xylene)from benzocyclobutene.
Preparation
Prepared from bromine and metallic aluminum.
2Al + 3Br2 ——? Al2Br6 (anhydrous).
General Description
A white to yellowish-red, lumpy solid with a pungent odor.
Reactivity Profile
An acid. May catalyze organic reactions. Corrosive to metals. Solutions of aluminum bromide in dichloromethane should be kept cold as a potentially dangerous exothermic halide exchange reaction occurs on warming, [Acc. Chem. Res., 1986, 19(3), 78].
Hazard
The anhydrous form reacts violently with water; corrosive to skin.
Health Hazard
CORROSIVE and/or TOXIC; inhalation, ingestion or contact (skin, eyes) with vapors, dusts or substance may cause severe injury, burns or death. Fire will produce irritating, corrosive and/or toxic gases. Reaction with water may generate much heat that will increase the concentration of fumes in the air. Contact with molten substance may cause severe burns to skin and eyes. Runoff from fire control or dilution water may cause pollution.
Fire Hazard
EXCEPT FOR ACETIC ANHYDRIDE (UN1715), THAT IS FLAMMABLE, some of these materials may burn, but none ignite readily. May ignite combustibles (wood, paper, oil, clothing, etc.). Substance will react with water (some violently), releasing corrosive and/or toxic gases and runoff. Flammable/toxic gases may accumulate in confined areas (basement, tanks, hopper/tank cars, etc.). Contact with metals may evolve flammable hydrogen gas. Containers may explode when heated or if contaminated with water. Substance may be transported in a molten form.
Safety Profile
A toxic, corrosive material. See also BROMIDES and ALUMINUM COMPOUNDS. Mixtures with sodium or potassium explode violently upon impact. When heated to decomposition it emits toxic fumes of Br-. Do not add H2O to anhydrous material. Hydrolysis can be violent.
Purification Methods
Reflux it and then distil it from pure aluminium chips in a stream of nitrogen into a flask containing more of the chips. It is then distilled under vacuum into ampoules [Tipper & Walker J Chem Soc 1352 1959]. Anhydrous conditions are essential, and the white to very light brown solid distillate can be broken into lumps in a dry-box (under nitrogen). It fumes in moist air. [Becher in Handbook of Preparative Inorganic Chemistry (Ed. Brauer) Academic Press Vol I p 812-813 1963.]
