Arsenic tribromide

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Arsenic tribromide
Ball and stick model of arsenic tribromide
Preferred IUPAC name
Arsenic tribromide
Systematic IUPAC name
Other names
Arsenic(III) bromide
Arsenous bromide
7784-33-0 YesY
ChemSpider 22973 YesY
ECHA InfoCard 100.029.143
EC Number 232-057-4
Jmol 3D model Interactive image
PubChem 24569
RTECS number CG1375000
Molar mass 314.634 g/mol
Appearance white to pale yellow crystalline solid
Density 3.54 g/cm3
Melting point 31.1 °C (88.0 °F; 304.2 K)
Boiling point 221 °C (430 °F; 494 K)
US health exposure limits (NIOSH):
PEL (Permissible)
[1910.1018] TWA 0.010 mg/m3[1]
REL (Recommended)
Ca C 0.002 mg/m3 [15-minute][1]
IDLH (Immediate danger)
Ca [5 mg/m3 (as As)][1]
Related compounds
Related compounds
Phosphorus tribromide
arsenic trichloride
Except where otherwise noted, 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.[2] The compound exists as colourless deliquescent crystals that fume in moist air.


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:[3]

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−.[4]

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.


Arsenic tribromide is toxic, as are most all arsenic compounds.


  1. ^ a b c "NIOSH Pocket Guide to Chemical Hazards #0038". National Institute for Occupational Safety and Health (NIOSH). 
  2. ^ CRC handbook of Chemistry and Physics, CRC Press
  3. ^ "Arsenic Tribromide" in Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 597.
  4. ^ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.