Phosphorus Halides


Phosphorus forms two types of halides, PX3 (X = F, Cl, Br, I) and PX5 (X = F, Cl, Br).

Phosphorus Trichloride

  • Passing dry chlorine over heated white phosphorus, Phosphorus Trichloride is prepared :

            

  • Action of thionyl chloride with white phosphorus.

            


Properties

  • It is a colourless oily liquid
  • It hydrolyses in the presence of moisture 
  • It reacts with organic compounds containing –OH group
  • It has a pyramidal shape, in which phosphorus is sp3 hybridised.


Phosphorus Pentachloride

It is prepared by the reaction of white phosphorus with excess of dry chlorine

Action of SO2Cl2 on phosphorus


Properties

  • It is a yellowish white powder
  • In moist air, it hydrolyses to POCl3 and finally gets converted to phosphoric acid

  • When heated, it sublimes but decomposes on stronger heating

  • It reacts with organic compounds containing –OH group converting them to chloro derivatives
  • Finely divided metals on heating with PCl5 give corresponding chlorides
  • It is used in the synthesis of some organic compounds
  • In gaseous and liquid phases, it has a trigonal bipyramidal structure


  • In the solid state it exists as an ionic solid, [PCl4]+[PCl6]– in which the cation, [PCl4]+ is tetrahedral and the anion, [PCl6]–octahedral.


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