Phosphorus tribromide

Chemical properties

Phosphorus tribromide is a colourless liquid(possibly hazy) 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 toalkyl bromides.
Phosphorus tribromide (PBr3) is commonly used in Hell-Volhard-Zelinsky halogenation for the α-bromination of carboxylic acids to form the corresponding acyl bromide. It is also useful for the conversion of primary and secondary alcohols to alkyl bromides.

The Uses of Phosphorus tribromide

Phosphorus tribromide is used mainly for the conversion of alcohols to alkyl bromides and it is used in tests for skin corrosivity. It is used for alkene preparation and it act as a lewis base and a lewis acid. Phosphorus tribromide is used in the manufacture of pharmaceuticals such as alprazolam, methohexital and fenoprofen.
Phosphorus tribromide may be used as a reagent:
In a novel protocol for synthesizing 7-ethoxy-1-(p-ethylphenoxy)-3,7-dimethyl-2-octene, a synthetic juvenile hormone mimic of trans,trans,cis-10,11-epoxy-7-ethyl-3,11-dimethyltrideca-2,6-dienoate.
To synthesize 1,2,3-diazaphosphinane, 1,2,3-thiazaphosphinine and 1,2-azaphosphole bearing a chromone ring.
To synthesize 1-Bromoundec-1-ene from 10-undecen-1-ol.

The Uses of Phosphorus tribromide

To a solution of the SM (1.12 g, 6.66 mmol) in dry ether (19 mL) at 0 C was added dropwise PBr3 (0.626 mL, 6.66 mmol). The ice bath was removed and the reaction was stirred for 3 h. H2O was carefully added to the mixture and the layers were separated. The org layer was washed with brine, dried (MgSO4), and concentrated in vacuo to provide the product. [1.49 g, 97%]

The Uses of Phosphorus tribromide

Phosphorus(III) bromide is used mainly for the conversion of alcohols to alkyl bromides and it is used in tests for skin corrosivity. It is used for alkene preparation and it act as a lewis base and a lewis acid. It is used as a catalyst for the alpha-bromination of carboxylic acids and used as intermediates in hell-volhard-zelinsky halogenation. Phosphorus tribromide is used in the manufacture of pharmaceuticals such as alprazolam, methohexital and fenoprofen. It is also used as a fire suppression agent.

What are the applications of Application

Phosphorus Tribromide is a component to test for skin corrosivity.

Preparation

Phosphorus tribromide, PBr3, is most conveniently prepared by reaction between liquid bromine and a solution of white phosphorus in PBr3. In most of its reactions, the tribromide resembles the trichloride although the former has been much less studied and in some cases the products seem to be more complex.

Reactions

Silyl phosphites such as (EtO)2POSiMe3 and (Et3SiO)3P are known. The latter compound can be prepared in 30% yield by reacting phosphorus tribromide with an organosilane in the presence of zinc chloride. Esters of the former type can be made by reaction.
3Et3SiO+PBr3–-(Et3SiO)3+3RBr
Et3SiONa+(EtO)2PCl–-(EtO)2POSiEt3+NaCl)

General Description

A colorless fuming liquid with a pungent odor. Corrosive to metals and tissue. Boiling point 347°F (175°C). Freezing point -40°F (-40°C).

Air & Water Reactions

Fumes in air. Decomposed by water to form phosphoric acid and hydrobromic acid. Reaction with warm water is very rapid and may be violent [Mellor v.8. 1032 1940].

Reactivity Profile

Phosphorus tribromide reacts with oxidizing agents to generate heat and products that may be flammable, combustible, or otherwise reactive; the reactions may be violent. Forms complexes with potassium or sodium metal that explode when shocked. Drop wise addition to 3-phenylpropanol caused an explosion when stirring of the mixture was discontinued [Chem. Brit., 1974, 10, 101-102].

Health Hazard

Inhalation causes severe irritation of nose, throat, and lungs. Ingestion causes burns of mouth and stomach. Contact with eyes or skin causes severe burns.

Safety Profile

Probably highly toxic. A corrosive irritant to the eyes, skin, and mucous membranes. Wdl react with water, steam, or acids to produce heat, toxic and corrosive fumes. Violent reaction or ignition with calcium hydroxide + sodium carbonate, phenylpropanol, sulfuric acid, oleum, fluorosulfuric acid, chlorosulfuric acid, 1,1,1 -tris(hydroxymethyl)methane, water, potassium, sodium, RuO4. When heated to decomposition it emits very toxic fumes of Brand POx. See also PHOSPHIDES and BROMIDES.

Purification Methods

It is decomposed by moisture, it should be kept dry and is corrosive. Purify it by distillation through an efficient fractionating column [see Whitmore & Lux J Am Chem Soc 54 3451] in a slow stream of dry N2, i.e. under strictly dry conditions. [Gay & Maxson Inorg Synth II 147 1946, Org Synth Col Vol II 358 1943.] Dissolve it in CCl4, dry it over CaCl2, filter and distil it. Store it in sealed ampoules under N2 and keep it away from light. HARMFUL VAPOURS.