Phosphorus pentabromide

Phosphorus pentabromide is a reactive, yellow solid of formula PBr5, which has the structure PBr4+ Br− 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 ([PBr4]+[Br3]−).[1]

Phosphorus pentabromide
Names
IUPAC name
Tetrabromophosphanium bromide
Other names
Tetrabromophosphonium bromide
Phosphorus pentabromide
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.029.260
UNII
  • InChI=1S/Br5P/c1-6(2,3,4)5 checkY
    Key: QRKVRHZNLKTPGF-UHFFFAOYSA-N checkY
  • BrP(Br)(Br)(Br)Br
Properties
PBr5
Molar mass 430.49 g/mol
Appearance yellow solid
Density 3.61 g/cm3
Melting point ca. 100 °C (decomposes)
Boiling point 106 °C (223 °F; 379 K) (decomposes)
decomposes
Solubility decomposes in ethanol
soluble in CCl4 and CS2
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)
Infobox references

It can be used in organic chemistry to convert carboxylic acids to acyl bromides. It is highly corrosive. It decomposes above 100 °C to give phosphorus tribromide and bromine:[2]

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 (PBr7).[3]

References
  1. Corbridge, D. E. C. (2013). Phosphorus: Chemistry, Biochemistry and Technology, Sixth Edition. CRC Press. p. 154. ISBN 978-1-4398-4088-7.
  2. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
  3. 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.
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.