Phosphorus pentabromide

Phosphorus pentabromide is a reactive, yellow solid of formula PBr5, which has the structure [PBr4]+Br− (tetrabromophosphonium bromide) in the solid state but in the vapor phase is completely dissociated to PBr3 and Br2. Rapid cooling of this phase to 15 K leads to formation of the ionic species phosphorus heptabromide (tetrabromophosphonium tribromide [PBr4]+[Br3]−).[2]

Phosphorus pentabromide
Names
IUPAC name
Tetrabromophosphanium bromide
Other names
  • Pentabromo-λ5-phosphane[1]
  • Pentabromophosphorane[1]
  • Phosphorus(V) bromide[1]
  • Phosphorus pentabromide
  • Tetrabromophosphonium bromide
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.029.260
EC Number
  • 232-186-6
UNII
UN number 2691
  • InChI=1S/Br5P/c1-6(2,3,4)5 checkY
    Key: QRKVRHZNLKTPGF-UHFFFAOYSA-N checkY
  • BrP(Br)(Br)(Br)Br
Properties
PBr5
Molar mass 430.494 g·mol−1
Appearance Yellow crystalline solid[1]
Density 3.61 g/cm3
Melting point ca. 100 °C (decomposes)
Boiling point 106 °C (223 °F; 379 K) (decomposes)
Reacts with water
Solubility Decomposes in ethanol
Soluble in CCl4 and CS2
Hazards[1]
Occupational safety and health (OHS/OSH):
Main hazards
 Causes severe skin burns and eye damage
GHS labelling:
GHS05: Corrosive
Danger
H314
P260, P264, P280, P301+P330+P331, P302+P361+P354, P304+P340, P305+P354+P338, P316, P321, P363, P405, P501
Related compounds
Related compounds
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

It can be used in organic chemistry to convert carboxylic acids to acyl bromides. It is highly corrosive. It strongly irritates skin and eyes.[1] It decomposes above 100 °C to give phosphorus tribromide and bromine:[3]

PBr5 → PBr3 + Br2

Reversing this equilibrium to generate PBr5 by addition of Br2 to PBr3 is difficult in practice because the product is susceptible to further addition to yield phosphorus heptabromide [PBr4]+[Br3]−.[4]

References
  1. https://pubchem.ncbi.nlm.nih.gov/compound/Phosphorus-pentabromide
  2. Corbridge, D. E. C. (2013). Phosphorus: Chemistry, Biochemistry and Technology, Sixth Edition. CRC Press. p. 154. ISBN 978-1-4398-4088-7.
  3. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
  4. Popov, A. I.; Skelly, N. E. (1954). "Spectrophotometric Study of Phosphorus Pentabromide in Various Solvents". J. Am. Chem. Soc. 76 (15): 3916–3919. doi:10.1021/ja01644a014.
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