Phosphorus Tribromide

       
 

Phosphorus Tri Bromide Properties :

 
 
CAS NO :
7789-60-8  
  MOLECULER FORMULA : PBr3  
 
COLOUR :
COLOURLESS TO PALE YELLOW FUMMING LIQUID.  
 
SOLUBLE :
SOLUBLE IN ALCOHOL CHLOROFORM  
 
BOILING POINT :
164 C  
 
DENSITY :
2.88 W/W  
 
ASSAY :
99. % BY G.C  
  ACETIC ACID 0.3%  

Phosphorus Tribromide is represented by the formula PBr3 and is a colorless liquid. This compound fumes in moist air due to hydrolysis has a sharp odor. It is used in laboratory to convert alcohols into alkyl bromides.

Preparation

PBr3 is prepared by dealing with red phosphorous with bromine. An excess of phosphorous is used in order to prevent the formation of PBr5. This reaction is highly combustible and is often conducted in the presence of diluents like PBr3.

The phosphorous tribromide like PCl3 and PF3 has dual properties of both Lewis base and Lewis acid. For instance boron tribromide forms stable 1:1 abducts like Br3B:PBr3. PBr 3 can react as an electrophile or with Lewis acid with some of its reactions which can be with amines. Its reaction with alcohol is most important because it replaces the OH group with a bromine atom to produce an alkyl bromide. Here all three bromides can be transferred.

Applications

The main application of Phosphorous Tribromide is to convert the primary or secondary alcohols into alkyl bromide. Pbr3 usually gives higher yields than hydrobromic acid. This avoids the problem of carbocation rearrangement because even neopentyl bromide can be made from alcohol.

PBr3 also acts like a catalyst for the α-bromination of carboxylic acids. Acyl bromides are not much prepared as compared to Acyl chlorides. They are used as an intermediate in the Hell Volhard Zelinsky halogenation. PBr3 reacts with carboxylic acid to form acyl bromide which is more reactive in nature.

Commercially, phosphorous bromide is used in the manufacture of pharmaceuticals like alprazolam, methohexital and fenoprofen. It is also a potent fire suppression agent which is marketed under the name PhostrEx.

Precautions

PBr turns into corrosive HBr and reacts violently with water and alcohol. In these reactions they produce phosphorous acid as a by-product. When you are carrying out the distillation process this can decompose above 160 degree C and can cause violent reaction on being contact with air.

Dhruv Chem manufactures pure and excellent quality chemicals through some of the best raw materials. Phosphorous Bromide is manufactured at its in-house manufacturing unit and goes through stringent test before final delivery.

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