Thionyl bromide

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Thionyl bromide
IUPAC name	Thionyl bromide
Other names	Sulfur oxy dibromide
Identifiers
CAS number	[507-16-4]
SMILES	O=S(Br)Br
Properties
Molecular formula	SOBr2
Molar mass	207.87 g/mol
Appearance	colorless liquid
Density	2.688 g/mL, liquid
Melting point	–52 °C
Boiling point	68 °C/40 mmHg
Solubility in water	decomposes violently
Structure
Molecular shape	trigonal pyramidal
Hazards
Main hazards	dangerously sensitive to water source of bromine, HBr
R-phrases	14-20/21-34
S-phrases	26-36/37/39-45
Flash point	nonflammable
Related compounds
Related compounds	SOCl2, SeOCl2; PBr3, Br2
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Thionyl bromide is the chemical compound SOBr₂. It is less stable and less widely used than its chloride analogue, thionyl chloride. It is prepared by the action of hydrogen bromide on thionyl chloride, a characteristic reaction where a stronger acid is converted to a weaker acid:

SOCl₂ + 2HBr → SOBr₂ + 2HCl

Thionyl bromide is used for some brominations of certain α,β-unsaturated carbonyls, and it also converts alcohols to alkyl bromides. Otherwise it hydrolyzes readily to release sulfur dioxide:

SOBr₂ + H₂O → SO₂ + 2HBr

[edit] Safety

SOBr₂ hydrolyzes readily to release dangerous HBr. It also reacts with acetone to give a hazardous lacrymator.

[edit] References

Mundy, B. P. "Thionyl Bromide" in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York.