Difference between revisions of "Phosphorus pentabromide"
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[[Category:Materials that react with water]] | [[Category:Materials that react with water]] |
Latest revision as of 20:58, 2 December 2018
Names | |
---|---|
Other names
Pentabromophosphorane
Phosphorus(V) bromide | |
Properties | |
PBr5 | |
Molar mass | 430.49 g/mol |
Appearance | Yellow crystalline solid |
Density | 3.61 g/cm3 |
Melting point | 103.7 °C (218.7 °F; 376.8 K) (decomposes) |
Boiling point | Decomposes |
Reacts | |
Solubility | Reacts with alcohols, carboxylic acids Soluble in AsCl3, bromine, liq. HBr, liq. HCl, liq. H2S, phosphoryl chloride, liq. SO2 sparingly soluble in benzene, carbon disulfide, carbon tetrachloride |
Thermochemistry | |
Std enthalpy of
formation (ΔfH |
-253.6 kJ/mol |
Hazards | |
Safety data sheet | Sigma-Aldrich |
Related compounds | |
Related compounds
|
Phosphorus tribromide Phosphoryl bromide |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
Infobox references | |
Phosphorus pentabromide is a reactive, unstable, yellow solid chemical compound with the formula PBr5. This compound has the structure PBr4+Br− in the solid state, but in the vapor phase is completely dissociated to PBr3 and Br2.
Contents
Properties
Chemical
Phosphorus pentabromide rapidly hydrolyzes in water to release hydrobromic and phorphorous acids.
Addition of elemental phosphorus to this liquid chemical will cause it to convert to PBr3.
Upon excess bromination or cooling below 15 K, it converts to phosphorus heptabromide, which is a red solid.
Physical
Phosphorus pentabromide is a yellowish crystalline solid, which breaks down to PBr3 and Br2 upon heating. PBr5 readily hydrolyzes in moist air. It is soluble in anh. HCl, HBr, H2S, but less so in benzene, CS2, carbon tet.
Availability
PBr5 is sometimes sold by chemical suppliers, but due to its hazards it's difficult to get hold of.
Preparation
Can be prepared by reacting PBr3 and bromine in equimolar amounts, at room temperature. Excess bromine will cause it to convert to PBr7. Petroleum ether can be used as a reaction solvent.
During the synthesis of phosphorus tribromide, small amounts of phosphorus pentabromide will be formed. To separate the pentabromide, the PBr3 and excess bromine are removed with a vacuum pump and condensed in a cold trap.
Projects
- Make phosphoryl bromide
- Make alkyl bromides
Handling
Safety
Phosphorus tribromide reacts with water and its fumes are very corrosive, as well as toxic. Wear proper protection when handling the compound.
Storage
In Schlenk flasks, at low temperatures. Periodically check for decomposition.
Disposal
Phosphorus pentabromide should be neutralized with a base, such as calcium hydroxide suspension outside or in a well ventilated area. Lots of HBr fumes will be produced during neutralization. Sodium thiosulfate can also be used as neutralizing agent, as it neutralizes bromine more effectively than bases.
References
Relevant Sciencemadness threads
- Articles containing unverified chemical infoboxes
- Chembox articles without image
- Chemical compounds
- Inorganic compounds
- Phosphorus compounds
- Bromides
- Phosphorus halides
- Materials that react with water
- Materials unstable in basic solution
- Things that can kill you very quickly
- Things that should NOT be messed with except by professionals
- Choking agents
- Solids