Chemical elements
  Phosphorus
    Isotopes
    Energy
    Preparation
    Applications
    Physical Properties
    Chemical Properties
      Alkali Phosphides
      Alkaline Earth Phosphides
      Copper Silver and Gold Phosphides
      Zinc Group Phosphides
      Aluminium Phosphide
      Titanium Group Phosphides
      Tin Phosphides
      Lead Phosphides
      Arsenic Phosphides
      Antimony Phosphides
      Bismuth Phosphides
      Chromium Phosphides
      Molybdenum and Tungsten Phosphides
      Manganese Phosphides
      Iron Phosphides
      Cobalt Phosphides
      Phosphonium Chloride
      Phosphonium Bromide
      Phosphonium Iodide
      Hydrogen Phosphides
      Alkylphosphines
      Phosphorus Trifluoride
      Phosphorus Pentafluoride
      Phosphorus Trifluorodichloride
      Phosphorus Trifluorodibromide
      Fluophosphoric Acid
      Phosphorus Dichloride
      Phosphorus Trichloride
      Phosphorus Pentachloride
      Phosphorus Chlorobromides
      Phosphorus Chloroiodides
      Phosphorus Tribromide
      Phosphorus Pentabromide
      Phosphorus Diiodide
      Phosphorus Triiodide
      Phosphorus Oxytrifluoride
      Phosphorus Oxychloride
      Pyrophosphoryl Chloride
      Metaphosphoryl Chloride
      Phosphoryl Monochloride
      Phosphoryl Dichlorobromide
      Phosphoryl Chlorodibromide
      Phosphoryl Tribromide
      Metaphosphoryl Bromide
      Phosphoryl Oxyiodides
      Phosphorus Thiotrifluoride
      Phosphorus Thiotrichloride
      Phosphorus Thiotribromide
      Mixed Phosphorus Thiotrihalides
      Phosphorus Suboxides
      Phosphorus Trioxide
      Phosphorus Dioxide
      Phosphorus Pentoxide
      Hypophosphorous Acid
      Phosphorous Acid
      Meta- and Pyro-phosphorous Acids
      Hypophosphoric Acid
      Tetraphosphorus Trisulphide
      Diphosphorus Trisulphide
      Tetraphosphorus Heptasulphide
      Phosphorus Pentasulphide
      Phosphorus Oxysulphides
      Phosphorus Thiophosphites
      Phosphorus Thiophosphates
      Phosphorus Selenophosphates
      Phosphorus Sulphoselenides
      Diamidophosphorous Acid
      Phosphorus Triamide
      Monamidophosphoric Acid
      Diamidophosphoric Acid
      Triamidophosphoric Acid
      Dimetaphosphimic Acid ≡P=
      Trimetaphosphimic Acid
      Tetrametaphosphimic Acid
      Penta- and Hexametaphosphimic Acid
      Monamidodiphosphoric Acid
      Diamidodiphosphoric Acid
      Triamidodiphosphoric Acid
      Nitrilotrimetaphosphoric acid
      Monothioamidophosphoric Acids
      Thiophosphoryl Nitride
      Di- Tri-imido- and -amido-thiophosphates
      Imidotrithiophosphoric Acid =
      Phosphorus Chloronitrides
      Triphosphonitrilic Chloride
      Tetraphosphonitrilic Chloride
      Pentaphosphonitrilic Chloride
      Hexaphosphonitrilic Chloride
      Heptaphosphonitrilic Chloride
      Triphosphonitrilic Bromide
      Phosphorus Halonitrides
      Phosphorus Nitride
      Phosphine
      Pyrophosphoric Acid
      Phosphoric acids
    Slow Oxidation
    Phosphatic Fertilisers

Pyrophosphoryl Chloride, P2O2Cl4






Pyrophosphoryl Chloride, or Diphosphorus trioxytetrachloride, P2O2Cl4 was first prepared by the action of N2O3 or N2O4 on PCl3. It is also produced as an intermediate product in the hydrolysis of POCl3. Thus when POCl3 is heated with a tenth of its weight of water in a sealed tube at 100° C. the three phosphoric oxychlorides (phosphoryl, pyrophosphoryl and metaphosphoryl) are present and may be separated by distillation in vacuo. Phosphorus pentachloride (2 mols.) and water (3 mols.) also gave this oxychloride when heated to 126° C. under pressure. When separated by fractional distillation under reduced pressure from POCl3, which is more volatile, and PO2Cl, which is less volatile, the pyro-compound appeared as a colourless fuming liquid which had a much lower freezing-point and a higher boiling-point than POCl3. At ordinary pressures it distilled with decomposition. The analysis agreed with the empirical formula given.

The density is about 1.58. The freezing-point is below -50° C., the boiling-point 210° to 215° C.

The liquid distils with some decomposition, which may be expressed by the equation

3P2O3Cl4 ⇔ 4POCl3 + P2O5

The reaction must be reversible since P2O3Cl4 has been obtained by the interaction of the compounds on the right-hand side.

By the action of PCl5 the ordinary oxychloride is regenerated, thus P2O3Cl4 + PCl5 = 3POCl3

PBr5 reacts in a similar manner with the production of an oxychloro- bromide, thus

P2O3Cl4 + PBr5 = 2POBrCl2 + POBr3

Hydrolysis leads to the same final products as are formed in the hydrolysis of POCl3. Pyrophosphoryl chloride also acts in a similar way with organic compounds containing the hydroxyl group giving, e.g., ethyl esters of phosphoric and chlorophosphoric acids.

Addition compounds with lime, magnesia and several other basic oxides were formed in organic solvents such as acetone, or ethyl acetate and other esters, and appeared as crystalline substances, associated usually with two molecules of the solvent, e.g. CaO.P2O3Cl4.2(CH3)2CO.


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