Arsenic tribromide is the

inorganic compound In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemis ...

with the formula As Br₃. This pyramidal molecule is the only known binary arsenic bromide. AsBr₃ is noteworthy for its very high

refractive index In optics, the refractive index (or refraction index) of an optical medium is a dimensionless number that gives the indication of the light bending ability of that medium. The refractive index determines how much the path of light is bent, ...

of approximately 2.3. It also has a very high diamagnetic susceptibility. The compound exists as colourless

deliquescent Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption or adsorption from the surrounding environment, which is usually at normal or room temperature. If water molecules become suspended among the substance' ...

crystals that fume in moist air.

Preparation

Arsenic tribromide can be prepared by the direct bromination of arsenic powder. Alternatively, arsenic(III) oxide can be used as the precursor in the presence of elemental sulfur: :2 As₂O₃ + 3 S + 6 Br₂ → 4 AsBr₃ + 3 SO₂

Bromides of arsenic

AsBr₅ is not known, although the corresponding phosphorus compound PBr₅ is well characterized. AsBr₃ is the parent for a series of hypervalent anionic bromoarsenates including s₂Br₈sup>2−, s₂Br₉sup>3−, and s₃Br₁₂sup>3−.Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. . Organoarsenic bromides, (CH₃)₂AsBr and (CH₃)AsBr₂ are formed efficiently by the copper-catalyzed reaction of

methyl bromide Bromomethane, commonly known as methyl bromide, is an organobromine compound with formula C H3 Br. This colorless, odorless, nonflammable gas is produced both industrially and biologically. It has a tetrahedral shape and it is a recognized ozo ...

with hot arsenic metal. This synthesis is similar to the direct process used for the synthesis of methyl chlorosilanes.

Safety

Arsenic tribromide is toxic, as are most arsenic compounds.

References

Arsenic(III) compounds Arsenic halides Bromides Carcinogens Teratogens {{Inorganic-compound-stub