Thionyl bromide

Thionyl bromide
Structure of the thionyl bromide molecule
Structure of the thionyl bromide molecule
3D model of a thionyl bromide molecule
3D model of a thionyl bromide molecule
Molecular arrangement in solid SOBr2 (note that this is dramatically different from the crystal structure of its chloride analogue)
Names
IUPAC name
Thionyl bromide
Other names
Sulfur oxy dibromide
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.007.332 Edit this at Wikidata
EC Number
  • 208-064-3
UNII
  • InChI=1S/Br2OS/c1-4(2)3 checkY
    Key: HFRXJVQOXRXOPP-UHFFFAOYSA-N checkY
  • InChI=1/Br2OS/c1-4(2)3
    Key: HFRXJVQOXRXOPP-UHFFFAOYAY
  • BrS(Br)=O
Properties
SOBr2
Molar mass 207.87 g/mol
Appearance colorless liquid
Density 2.688 g/mL, liquid[1]
Melting point −52 °C (−62 °F; 221 K) ; may include supercooling[1]
Boiling point
  • 48 °C at 20 mmHg[1]
  • 136 °C at 1 atm but 1⁄3 decomposes[1]
decomposes
Solubility reacts in HBr, acetone, and alcohol
soluble in benzene, toluene, ether
Structure
trigonal pyramidal
1.47 D[1]
Hazards[2]
Occupational safety and health (OHS/OSH):
Main hazards
 Readily decomposes in air to toxic gases
GHS labelling:
GHS05: CorrosiveGHS07: Exclamation mark
Danger
H312, H314, H332
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 [77 °F], 100 kPa).
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Thionyl bromide is the chemical compound SOBr2. It is less stable and less widely used than its chloride analogue, thionyl chloride.[3] It is prepared by the action of hydrogen bromide on thionyl chloride,[4] although the corresponding reaction at higher pH (i.e. alkali bromides) proceeds only with difficulty:[1]

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.[1]

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.[1]

It can be used for brominations of certain α,β-unsaturated carbonyl compounds.[5]

It may occasionally be used as a solvent.[6][7]

  1. ^ a b c d e f g h 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.