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Thionyl bromide

Names
IUPAC name Thionyl bromide
Other names Sulfur oxy dibromide
Identifiers
CAS Number	507-16-4
3D model (JSmol)	Interactive image
ChemSpider	61483
ECHA InfoCard	100.007.332
EC Number	208-064-3
PubChem CID	68176
UNII	N6CU78B13T
CompTox Dashboard (EPA)	DTXSID0060143
InChI InChI=1S/Br2OS/c1-4(2)3Key: HFRXJVQOXRXOPP-UHFFFAOYSA-N InChI=1/Br2OS/c1-4(2)3Key: HFRXJVQOXRXOPP-UHFFFAOYAY
SMILES BrS(Br)=O
Properties
Chemical formula	SOBr2
Molar mass	207.87 g/mol
Appearance	colorless liquid
Density	2.688 g/mL, liquid
Melting point	−52 °C (−62 °F; 221 K) ; may include supercooling
Boiling point	48 °C at 20 mmHg 136 °C at 1 atm but 1⁄3 decomposes
Solubility in water	decomposes
Solubility	reacts in HBr, acetone, and alcohol soluble in benzene, toluene, ether
Structure
Molecular shape	trigonal pyramidal
Dipole moment	1.47 D
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	Readily decomposes in air to toxic gases
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H312, H314, H332
Precautionary statements	P280, P305+P351+P338, P310
Flash point	Non-flammable
Safety data sheet (SDS)	"External MSDS"
Related compounds
Related compounds	SOCl2, SeOCl2; PBr3, Br2
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). N verify (what is  ?) Infobox references

Thionyl bromide is the chemical compound SOBr₂. It is less stable and less widely used than its chloride analogue, thionyl chloride, but engages in similar reactions.

Chemistry

It is prepared by the action of hydrogen bromide on thionyl chloride, although the corresponding reaction at higher pH (i.e. alkali bromides) proceeds only with difficulty:

SOCl₂ + 2 HBr → SOBr₂ + 2 HCl

Phosphorus trichlorodibromide (but not phosphorus pentabromide!) converts sulfur dioxide to thionyl bromide. Thionyl chlorobromide appears to be a key intermediate in these syntheses, but has not been isolated.

Thionyl bromide will convert alcohols to alkyl bromides and carboxylic acids to acyl bromides. Unlike with thionyl chloride, stoichiometric bases are problematic activating agents, because free bromide anions decompose thionyl bromide to tribromide, sulfur dioxide, and sulfur.

It can be used for brominations of certain α,β-unsaturated carbonyl compounds.

It may occasionally be used as a solvent.

Safety

SOBr₂ hydrolyzes readily in air to release dangerous fumes of sulfur dioxide and hydrogen bromide.

SOBr₂ + H₂O → SO₂ + 2 HBr

Decomposition to bromine and sulfur monoxide does not occur except at elevated temparatures.

References

1. ^ Magee, Philip S. (1971). "The Sulfur–Bromine Bond". In Senning, Alexander (ed.). Sulfur in Organic and Inorganic Chemistry. Vol. 1. New York: Marcel Dekker. pp. 271–276. ISBN 0-8247-1615-9. LCCN 70-154612.
2. "Thionyl bromide". Sigma Aldrich.
3. Mundy, B. P. (2004). "Thionyl Bromide". In Paquette, E. (ed.). Encyclopedia of Reagents for Organic Synthesis. New York: J. Wiley & Sons. doi:10.1002/047084289X.rt098. ISBN 0471936235.
4. Booth, Harold Simmons (1939). Inorganic syntheses. Volume 1. New York. p. 113. ISBN 978-0-470-13264-7. OCLC 86223179.{{cite book}}: CS1 maint: location missing publisher (link)
5. Saraf, S. D. (1 August 1969). "Reaction of thionyl bromide with tropolone and phenol". Canadian Journal of Chemistry. 47 (15): 2803–2804. doi:10.1139/v69-465.
6. Furlani, C.; Zinato, E. (May 1967). "Hexahalogenoniobates(V), Oxopentahalogenoniobates(V) and their electronic spectra". Zeitschrift für anorganische und allgemeine Chemie. 351 (3–4): 210–218. doi:10.1002/zaac.19673510311.
7. The chemistry of the actinide and transactinide elements. Volumes 1-6 (4th ed.). Dordrecht: Springer. 2010. p. 526. ISBN 978-94-007-0211-0.

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