Phosphorus pentabromide

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Phosphorus pentabromide
IUPAC name phosphorus pentabromide
Other names phosphorus(V) bromide
Identifiers
CAS number [7789-69-7]
Properties
Molecular formula PBr5
Molar mass 430.49 g/mol
Melting point

ca. 100 °C (decomposes)

Boiling point

106 °C (decomposes)

Solubility in water decomposes
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and references

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 an ionic species [PBr4]+[Br3]-.

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

PBr5PBr3 + Br2