Arsenic tribromide

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Arsenic tribromide
Ball and stick model of arsenic tribromide
Identifiers
CAS number 7784-33-0 YesY
PubChem 24569 YesY
ChemSpider 22973 YesY
EC number 232-057-4
RTECS number CG1375000
Jmol-3D images Image 1
Properties
Molecular formula AsBr3
Molar mass 314.634 g/mol
Appearance white to pale yellow crystalline solid
Density 3.54 g/cm3
Melting point 31.1 °C
Boiling point 221 °C
Solubility in water decomposes
Refractive index (nD) 2.3
Related compounds
Related compounds Phosphorus tribromide
arsenic trichloride
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Arsenic tribromide is the inorganic compound with the formula AsBr3. This pyramidal molecule is the only known binary arsenic bromide. AsBr3 is noteworthy for its very high refractive index of approximately 2.3. It also has a very high diamagnetic susceptibility.[1] The compound exists as colourless deliquescent crystals that fume in moist air.

Preparation[edit]

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]

2 As2O3 + 3 S + 6 Br2 → 4 AsBr3 + 3 SO2

Bromides of arsenic[edit]

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 [As2Br8]2−, [As2Br9]3−, and [As3Br12]3−.[3]

Organoarsenic bromides, (CH3)2AsBr and (CH3)AsBr2 are formed efficiently by the copper-catalyzed reaction of methyl bromide with hot arsenic metal. This synthesis is similar to the direct process used for the synthesis of methyl chlorosilanes.

Safety[edit]

Arsenic tribromide is toxic, as are all arsenic compounds.

References[edit]

  1. ^ CRC handbook of Chemistry and Physics, CRC Press
  2. ^ "Arsenic Tribromide" in Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 597.
  3. ^ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.