Phosphoryl bromide

Phosphoryl bromide

Names
IUPAC name Phosphoryl bromide
Other names Phosphoric tribromide Phosphorus(V) oxybromide
Properties
Chemical formula	POBr3
Molar mass	286.69 g/mol
Appearance	Colorless clear solid
Odor	Acrid
Density	2.82 g/cm3
Melting point	56 °C (133 °F; 329 K)
Boiling point	192 °C (378 °F; 465 K)
Solubility in water	Reacts
Solubility	Reacts with alcohols, carboxylic acids Soluble in benzene, bromine, chloroform, carbon disulfide, diethyl ether, liq. HBr, liq. HCl, conc. sulfuric acid, THF
Hazards
Safety data sheet	Sigma-Aldrich
Flash point	Non-flammable
Related compounds
Related compounds	Phosphorus tribromide Phosphorus pentabromide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Phosphoryl bromide is an inorganic compound, a colorless or faint orange-ish solid, which fumes in moist air. It's a phosphorus halide that has the formula POBr₃.

Properties

Chemical

POBr₃ hydrolyzes in water and moist air to form hydrobromic acid and phosphoric acid.

Physical

Phosphoryl bromide is a colorless to faint yellow-orange solid, which readily fumes in air. It is soluble in diethyl ether, benzene, chloroform, carbon disulfide, concentrated sulfuric acid.

Availability

Phosphoryl bromide is sold by various suppliers, but due to its hazards it's almost impossible to obtain. It's best to make it yourself.

Preparation

Can be prepared by adding bromine to phosphorus tribromide at 0 °C, followed by careful addition of water and vacuum distillation of the resulting slurry.

Another route is the reaction of phosphorus pentabromide with phosphorus pentoxide:

3 PBr₅ + P₂O₅ → 5 POBr₃

Projects

• Make phosphate esters

Handling

Safety

POBr₃ reacts with the moisture from air to release HBr fumes which are very corrosive and toxic. Wear proper protection when handling the compound.

Storage

Should be kept in closed air-tight containers, in a glovebox or desiccator. Schlenk flasks are good storage containers.

Disposal

Phosphoryl bromide should be neutralized with a base, such as calcium hydroxide suspension outside or in a well ventilated area. Since the neutralization produces plenty of HBr fumes, this should be performed in a fumehood or outside. Sodium thiosulfate can also be used as neutralizing agent, as it neutralizes HBr and Br₂ more effectively.