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 chemist ...
with the formula
As Br3. This pyramidal molecule is the only known
binary
Binary may refer to:
Science and technology Mathematics
* Binary number, a representation of numbers using only two digits (0 and 1)
* Binary function, a function that takes two arguments
* Binary operation, a mathematical operation that t ...
arsenic bromide. AsBr
3 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, or ...
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 As
2O
3 + 3 S + 6 Br
2 → 4 AsBr
3 + 3 SO
2
Bromides of arsenic
AsBr
5 is not known, although the corresponding phosphorus compound PBr
5 is well characterized. AsBr
3 is the parent for a series of
hypervalent
In chemistry, a hypervalent molecule (the phenomenon is sometimes colloquially known as expanded Octet rule, octet) is a molecule that contains one or more main group elements apparently bearing more than eight electrons in their valence shells. P ...
anionic bromoarsenates including
2Br8">s2Br8sup>2−,
2Br9">s2Br9sup>3−, and
3Br12">s3Br12sup>3−.
[Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. .]
Organoarsenic bromides, (CH
3)
2AsBr and (CH
3)AsBr
2 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 ozon ...
with hot arsenic metal. This synthesis is similar to the direct process used for the synthesis of methyl
chlorosilane
Chlorosilanes are a group of reactive, chlorine-containing chemical compounds, related to silane and used in many chemical processes. Each such chemical has at least one silicon-chlorine bond. Trichlorosilane is produced on the largest scale. The p ...
s.
Safety
Arsenic tribromide is toxic, as are most arsenic compounds.
References
Arsenic(III) compounds
Arsenic halides
Bromides
Carcinogens
Teratogens
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