Phosphorus tribromide
General
Systematic name	phosphorus tribromide
Other names	phosphorus(III) bromide phosphorous bromide tribromophosphine
Molecular formula	PBr3
Molar mass	270.70 g/mol
Appearance	clear, colourless liquid
CAS number	[7789-60-8]
Properties
Density and phase	2.852 g/cm3, liquid
Solubility in water	rapid hydrolysis
in methanol	decomposes
in acetone, chloroform, diethyl ether	soluble
Melting point	-41.5 °C (231.7 K)
Boiling point	173.2 °C (446.4 K)
Viscosity	? cP at ? °C
Structure
Molecular shape	trigonal bipyramidal
Dipole moment	? D
Hazards
MSDS	External MSDS
Main hazards	corrosive, toxic, reactive with water and alcohols
NFPA 704
Flash point	? °C
R/S statement	R: 14, 34, 37 S: 25, 45
RTECS number	TH4460000
Supplementary data page
Structure & properties	n, εr, etc.
Thermodynamic data	Phase behaviour Solid, liquid, gas
NMR	δ227 (downfield of H3PO4
Related compounds
Other anions	phosphorus trifluoride phosphorus trichloride phosphorus triiodide
Other cations	nitrogen tribromide arsenic tribromide antimony tribromide
Related compounds	phosphorus pentabromide phosphorus oxybromide
Except where noted otherwise, data are given for materials in their standard state (at 25°C, 100 kPa) Infobox disclaimer and references

Phosphorus tribromide is a colourless liquid with the formula PBr₃. It fumes in air due to hydrolysis and has a penetrating odour. It is widely used in the laboratory for the conversion of alcohols to alkyl bromides. Image File history File links Download high-resolution version (1100x692, 55 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Phosphorus tribromide ... Image File history File links Download high-resolution version (1100x1045, 216 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Phosphorus tribromide User:Benjah-bmm27/Gallery User:Ben Mills/Gallery ... IUPAC nomenclature is a system of naming chemical compounds and of describing the science of chemistry in general. ... A chemical formula (also called molecular formula) is a concise way of expressing information about the atoms that constitute a particular chemical compound. ... Molar mass is the mass of one mole of a chemical element or chemical compound. ... CAS registry numbers are unique numerical identifiers for chemical compounds, polymers, biological sequences, mixtures and alloys. ... Density (symbol: ρ - Greek: rho) is a measure of mass per volume. ... In the physical sciences, a phase is a set of states of a macroscopic physical system that have relatively uniform chemical composition and physical properties (i. ... It has been suggested that this article or section be merged with Solution. ... This article describes water from a scientific and technical perspective. ... Hydrolysis is a chemical reaction or process in which a molecule is split into two parts by reacting with a molecule of water, which has the chemical formula H2O. One of the parts gets an OH- from the water molecule and the other part gets an H+ from the water. ... methanol is also used to fuel speedway bikes. ... Rotting fruit Decomposition is a phenomenon common in the sciences of biology and chemistry. ... In chemistry, acetone (also known as propanone, dimethyl ketone, 2-propanone, propan-2-one and β-ketopropane) is the simplest representative of the ketones. ... Chloroform, also known as trichloromethane and methyl trichloride, is a chemical compound with formula CHCl3. ... Diethyl ether, also known as ether and ethoxyethane, is a clear, colorless, and highly flammable liquid with a low boiling point and a characteristic smell. ... The melting point of a crystalline solid is the temperature at which it changes state from solid to liquid. ... The boiling point of a substance is the temperature at which it can change its state from a liquid to a gas throughout the bulk of the liquid at a given pressure. ... The pitch drop experiment at the University of Queensland. ... The poise (P) is the cgs unit of viscosity, 1 P = 1 g·cm-1·s-1 The SI analog is 1 pascal second (Pa·s) = 1 kg·m-1·s-1 = 10 P. It is named after Jean Louis Marie Poiseuille. ... four sp³ orbitals three sp² orbitals In chemistry, hybridisation or hybridization (see also spelling differences) is the concept of mixing atomic orbitals to form new hybrid orbitals suitable for the qualitative description of atomic bonding properties. ... // The Earths magnetic field, which is approximately a dipole. ... The debye (symbol: D) is a non-SI and non-CGS unit of electrical dipole moment. ... A material safety data sheet or MSDS is a form containing data regarding the properties of a particular substance. ... This page provides supplementary chemical data on phosphorus tribromide. ... The examples and perspective in this article or section may not represent a worldwide view. ... NFPA 704 is a standard maintained by the U.S. National Fire Protection Association. ... Image File history File links File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... The flash point of a flammable liquid is the lowest temperature at which it can form an ignitable mixture with air. ... Risk and Safety Statements, also known as R/S statements, R/S numbers, R/S phrases, and R/S sentences, is a system of hazard codes and phrases for labeling dangerous chemicals and compounds. ... RTECS, also known as Registry of Toxic Effects of Chemical Substances, is a database of toxicity information compiled from the open scientific literature that is available for charge. ... This page provides supplementary chemical data on phosphorus tribromide. ... This page provides supplementary chemical data on phosphorus tribromide. ... The refractive index (or index of refraction) of a material is the factor by which the phase velocity of electromagnetic radiation is slowed in that material, relative to its velocity in a vacuum. ... The dielectric constant εr (represented as or K in some cases) is defined as the ratio: where εs is the static permittivity of the material in question, and ε0 is the vacuum permittivity. ... This page provides supplementary chemical data on phosphorus tribromide. ... Nuclear Magnetic Resonance Spectroscopy most commonly known as NMR Spectroscopy is the name given to the technique which exploits the magnetic properties of nuclei. ... Phosphoric acid, also known as orthophosphoric acid or phosphoric(V) acid, is an inorganic mineral acid having the chemical formula H3PO4. ... An ion is an atom or group of atoms that normally are electrically neutral and achieve their status as an ion by loss or addition of one or more electrons. ... Phosphorus trifluoride (formula PF3, is a colourless and odourless gas. ... Phosphorus trichloride (formula PCl3) is the most important of the three phosphorus chlorides. ... Phosphorus triiodide (PI3) is an unstable red solid which reacts violently with water. ... An ion is an atom or group of atoms that normally are electrically neutral and achieve their status as an ion by loss or addition of one or more electrons. ... Arsenic tribromide is the chemical compound with the formula AsBr3. ... Antimony tribromide (SbBr3) is a chemical compound. ... Phosphorus pentabromide is a yellow solid of formula PBr5, which has the structure PBr4+ Br− in the solid state. ... In chemistry, the standard state of a material is its state at 1 bar (100 kilopascals) and 25 degrees Celsius (298. ... General Name, Symbol, Number phosphorus, P, 15 Chemical series nonmetals Group, Period, Block 15, 3, p Appearance waxy white/ red/ black/ colorless Atomic mass 30. ... General Name, Symbol, Number bromine, Br, 35 Chemical series halogens Group, Period, Block 17, 4, p Appearance gas/liquid: red-brown solid: metallic luster Atomic mass 79. ... Hydrolysis is a chemical reaction or process in which a molecule is split into two parts by reacting with a molecule of water, which has the chemical formula H2O. One of the parts gets an OH- from the water molecule and the other part gets an H+ from the water. ... Functional group of an alcohol molecule. ... In chemistry, an alkyl halide is an organic molecule of the form R_X, where X is a halide and R contains a carbon atom bonded to other functional groups or hydrogens. ...

Chemical properties

Phosphorus tribromide, like PCl₃ and PF₃, has both properties of a Lewis base and a Lewis acid. For example, with a Lewis acid such as boron tribromide it forms stable 1:1 adducts such as Br₃B-PBr₃. At the same time PBr₃ can react as an electrophile or Lewis acid in many of its reactions, for example with amines. Phosphorus trichloride (formula PCl3) is the most important of the three phosphorus chlorides. ... Phosphorus trifluoride (formula PF3, is a colourless and odourless gas. ... A Lewis base is any molecule or ion that can form a new covalent bond by donating a pair of electrons. ... In chemistry, a Lewis acid can accept a pair of electrons and form a coordinate covalent bond, after the American chemist Gilbert Lewis. ... Bromine tribromide, BBr3, is a liquid compound containing boron and bromine. ... In chemistry, an electrophile (literally electron-lover) is a reagent attracted to electrons that participates in a chemical reaction by accepting an electron pair in order to bond to a nucleophile. ...

The most important reaction of PBr₃ is with alcohols, where it replaces an OH group with a bromine atom to produce an alkyl bromide. Note that all three bromines can be transferred. In general usage, alcohol (from Arabic al-khwl الكحول, or al-ghawl الغول) refers almost always to ethanol, also known as grain alcohol, and often to any beverage that contains ethanol (see alcoholic beverage). ... // Hydroxyl group The term hydroxyl group is used to describe the functional group -OH when it is a substituent in an organic compound. ... In chemistry, an alkyl halide is an organic molecule of the form R_X, where X is a halide and R contains a carbon atom bonded to other functional groups or hydrogens. ...

PBr₃ + 3 ROH → 3 RBr + HP(O)(OH)₂

The mechanism (shown for a primary alcohol) involves initial activation of the alcohol oxygen by the electrophilic phosphorus (to form a good leaving group), followed by an S_N2 substitution at the alcohol carbon. Functional group of an alcohol molecule. ... In chemistry, an alkyl halide is an organic molecule of the form R_X, where X is a halide and R contains a carbon atom bonded to other functional groups or hydrogens. ... The compound phosphorous acid, with formula H3PO3, is an oxoacid of phosphorus. ... The SN2 reaction is a type of nucleophilic substitution, where a nucleophile attacks an electrophilic center and bonds to it, expelling another group called a leaving group. ...

Image File history File links PBr3_alcohol_rxn. ...

Because of the S_N2 substitution step, the reaction generally works well for primary and secondary alcohols, but fails for tertiary alcohols. If the reacting carbon centre is chiral, the reaction usually occurs with inversion of configuration at the alcohol carbon, as is usual with an S_N2 reaction. Functional group of an alcohol molecule. ... The term chiral (pronounced ) is used to describe an object which is non-superimposable on its mirror image. ... The different types of isomers. ...

In a similar reaction, PBr₃ also converts carboxylic acids to acyl bromides. Structure of a carboxylic acid The 3D structure of the carboxyl group A space-filling model of the carboxyl group Carboxylic acids are organic acids characterized by the presence of a carboxyl group, which has the formula -(C=O)-OH, usually written as -COOH. In general, the salts and anions... An acyl halide (also known as an acid halide) is an organic compound containing a carbon atom which is double_bonded to an oxygen atom and singly bonded to a chlorine atom. ...

PBr₃ + 3 RCOOH → 3 RCOBr + HP(O)(OH)₂

PBr₃ is a reasonably strong reducing agent, and the oxidation of PBr₃ with oxygen gas is more vigorous than seen with PCl₃. It gives an explosive reaction that forms P₂O₅ and Br₂. Structure of a carboxylic acid The 3D structure of the carboxyl group A space-filling model of the carboxyl group Carboxylic acids are organic acids characterized by the presence of a carboxyl group, which has the formula -(C=O)-OH, usually written as -COOH. In general, the salts and anions... An acyl halide (also known as an acid halide) is an organic compound containing a carbon atom which is double_bonded to an oxygen atom and singly bonded to a chlorine atom. ... The compound phosphorous acid, with formula H3PO3, is an oxoacid of phosphorus. ... Semi-accurate illustration of a redox reaction Redox reactions include all chemical processes in which atoms have their oxidation number (oxidation state) changed. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Atomic mass 15. ... Phosphorus pentoxide, perhaps more accurately diphosphorus pentoxide, is so called because of its empirical formula P2O5, as should be expected of any element in oxidation number +5. ... General Name, Symbol, Number bromine, Br, 35 Chemical series halogens Group, Period, Block 17, 4, p Appearance gas/liquid: red-brown solid: metallic luster Atomic mass 79. ...

Preparation

PBr₃ is by treating phosphorus with bromine, using PBr₃ itself as the solvent (white phosphorus is soluble in PBr₃). An excess of phosphorus is used in order to prevent formation of PBr₅. General Name, Symbol, Number phosphorus, P, 15 Chemical series nonmetals Group, Period, Block 15, 3, p Appearance waxy white/ red/ black/ colorless Atomic mass 30. ... General Name, Symbol, Number bromine, Br, 35 Chemical series halogens Group, Period, Block 17, 4, p Appearance gas/liquid: red-brown solid: metallic luster Atomic mass 79. ...

P₄ + 6 Br₂ → 4 PBr₃

General Name, Symbol, Number phosphorus, P, 15 Chemical series nonmetals Group, Period, Block 15, 3, p Appearance waxy white/ red/ black/ colorless Atomic mass 30. ... General Name, Symbol, Number bromine, Br, 35 Chemical series halogens Group, Period, Block 17, 4, p Appearance gas/liquid: red-brown solid: metallic luster Atomic mass 79. ...

Uses

The main use for phosphorus tribromide is for conversion of primary or secondary alcohols to alkyl bromides^[7], as described above. PBr₃ usually gives higher yields than hydrobromic acid, and it avoids problems of carbocation rearrangement- for example even neopentyl bromide can be made from the alcohol in 60% yield^[6]. Functional group of an alcohol molecule. ... In chemistry, an alkyl halide is an organic molecule of the form R_X, where X is a halide and R contains a carbon atom bonded to other functional groups or hydrogens. ... It has been suggested that this article or section be merged into hydrogen bromide. ... A carbocation is an ion with a positively-charged carbon atom. ... Neopentane, also called dimethylpropane or 2,2-dimethylpropane, is a double-branched-chain alkane with five carbon atoms. ...

Another use for PBr₃ is as a catalyst for the α-bromination of carboxylic acids. Although acyl bromides are rarely made in comparison with acyl chlorides, they are used as intermediates in Hell-Volhard-Zelinsky halogenation ^[8]. Initially PBr₃ reacts with the carboxylic acid to form the acyl bromide, which is more reactive towards bromination. The overall process can be represented as Structure of a carboxylic acid The 3D structure of the carboxyl group A space-filling model of the carboxyl group Carboxylic acids are organic acids characterized by the presence of a carboxyl group, which has the formula -(C=O)-OH, usually written as -COOH. In general, the salts and anions... General Chemical Structure of an Acyl Chloride In organic chemistry, an acyl chloride (or acid chloride) is an organic compound which is a reactive derivative of a carboxylic acid. ... The Hell-Volhard-Zelinsky halogenation reaction halogenates carboxylic acids at the α carbon. ...

Image File history File links PBr3_HVZ_rxn. ...

On a commercial scale, phosphorus tribromide is used in the manufacture of pharmaceuticals such as alprazolam, methohexital and fenoprofen. It is also a potent fire suppression agent marketed under the name PhostrEx. Pharmacology (in Greek: pharmacon is drug, and logos is science) is the study of how chemical substances interfere with living systems. ... Alprazolam is a short-acting drug in the benzodiazepine class used to treat anxiety disorders and as an adjunctive treatment for depression. ... Methohexital is a short-acting intravenous anaesthetic induction agent, that is, used to commence anaesthesia. ...

Precautions

PBr₃ evolves corrosive HBr, is toxic, and reacts violently with water and alcohols.

In reactions that produce phosphorous acid as a by-product, when working up by distillation be aware that this can decompose above about 160 °C to give phosphine which can cause explosions in contact with air.^[7] The compound phosphorous acid, with formula H3PO3, is an oxoacid of phosphorus. ... Phosphine is the common name for phosphorus hydride (PH3), also known by the IUPAC name phosphane and, occasionally, phosphamine. ...

References

1. N. N. Greenwood, A. Earnshaw, Chemistry of the Elements, 2nd ed., Butterworth-Heinemann, Oxford, UK, 1997.
2. Handbook of Chemistry and Physics, 71st edition, CRC Press, Ann Arbor, Michigan, 1990.
3. J. March, Advanced Organic Chemistry, 4th ed., p. 723, Wiley, New York, 1992.
4. The Merck Index, 7th edition, Merck & Co, Rahway, New Jersey, USA, 1960.
5. R. R. Holmes, Journal of Inorganic and Nuclear Chemistry 12, 266-275 (1960).
6. L. G. Wade, Jr., Organic Chemistry, 6th ed., p. 477, Pearson/Prentice Hall, Upper Saddle River, New Jersey, USA, 2005.
7. George C. Harrison, H. Diehl, in Organic Syntheses Collective Volume 3, p 370, Wiley, New York, 1955.
8. L. G. Wade, Jr., Organic Chemistry, 6th ed., p. 1051, Pearson/Prentice Hall, Upper Saddle River, New Jersey, USA, 2005.

External links

• Links to external chemical sources.