Phosphorus pentabromide

Phosphorus pentabromide
Names
	IUPAC name Tetrabromophosphanium bromide
	Other names Pentabromo-λ5-phosphane; Pentabromophosphorane; Phosphorus(V) bromide; Phosphorus pentabromide; Tetrabromophosphonium bromide;
Identifiers
CAS Number	7789-69-7 ;
3D model (JSmol)	Interactive image;
ChemSpider	56429 ;
ECHA InfoCard	100.029.260
EC Number	232-186-6;
PubChem CID	62678;
UNII	3D9WIS0BQW ;
UN number	2691
CompTox Dashboard (EPA)	DTXSID6064874 ;
	InChI InChI=1S/Br5P/c1-6(2,3,4)5 Key: QRKVRHZNLKTPGF-UHFFFAOYSA-N ;
	SMILES BrP(Br)(Br)(Br)Br;
Properties
Chemical formula	PBr5
Molar mass	430.494 g·mol−1
Appearance	Yellow crystalline solid
Density	3.61 g/cm3
Melting point	ca. 100 °C (decomposes)
Boiling point	106 °C (223 °F; 379 K) (decomposes)
Solubility in water	Reacts with water
Solubility	Decomposes in ethanol; Soluble in CCl4 and CS2
Hazards
	Occupational safety and health (OHS/OSH):
Main hazards	Causes severe skin burns and eye damage
	GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H314
Precautionary statements	P260, P264, P280, P301+P330+P331, P302+P361+P354, P304+P340, P305+P354+P338, P316, P321, P363, P405, P501
Related compounds
Related compounds	Phosphorus pentafluoride; Phosphorus pentachloride; Phosphorus pentaiodide; Phosphorus tribromide; Phosphorus heptabromide; Phosphoryl bromide;
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Phosphorus pentabromide is a reactive, yellow solid of formula P Br₅, 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]

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

^ ^a ^b ^c ^d ^e ^f "Phosphorus pentabromide".
^ Corbridge, D. E. C. (2013). Phosphorus: Chemistry, Biochemistry and Technology, Sixth Edition. CRC Press. p. 154. ISBN 978-1-4398-4088-7.
^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
^ 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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[pubchem-1] ^ ^a ^b ^c ^d ^e ^f "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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