(Hive Bee)
02-19-03 01:44
No 409706
      Preparation of pyrophosphoryl chloride
(Rated as: excellent)

Pyrophosphoryl chloride is used as a formylating agent (see ../rhodium/chemistry /formylations.html). But, purchasing it from a chem supply is rather expensive, so I decided to post this preparation.

Example 1

10.81g of phosphorus pentachloride are introduced into 14.07g of dichlorophosphoric acid 8molar ration of the acid to phosphorus pentachloride is 2:1), the mixture placed in a distillation flask and immediatelly connected with a vacuum distillation apparatus. By the application of water pump vacuum and cooling of the receiver and of the cold trap attached thereto with solid carbon dioxide, the hydrogen chloride formed was sucked off from the reaction mixture and the resultant phosphorus oxychloride continuously distilled off at 20° C and condensed in the receiver and cold trap. The last traces of phosphorus oxychloride formed are finally driven off by a gentle warming of the distillation flask. The receiver is then changed and the pyrophosphoryl chloride formed is distilled over.

Yield: 12.24g (93.6% of theory)

Example 4

60.74g of phosphorus oxychloride are mixed with 5.71mL of water (molar ratio of phosphorus oxychloride to water is 1:0.8). After the amount of HCl gas equivalent to the added amount of water has been liberated (standing for 24 h at 20° C), 53.01g of the ''hydrated phosphorus oxychloride'' are mixed with 31.86g of phosphorus pentachloride and further reacted and worked up as described as in example 1.

Yield: 24.87g (71.2% of theory)

Reference: Patent GB971664

I'm dreaming of the white crystals.
(Hive Bee)
02-19-03 09:20
No 409784
      Very nice!  Bookmark   

By any chance do you have a (simple) method of producing phosphorus oxychloride from scratch? (The lower down the foodchain to start, the better)
(Hive Addict)
02-19-03 10:39
No 409810
      POCl3  Bookmark   

React red phosphorous with Chlorine gas you get PCl3.
Burn this in dry air you get POCl3 (PCl3, and POCl3, reacts with water,and moisture in the air).
I can't remember where i read that though.
(Hive Bee)
02-19-03 13:25
No 409849
      POCl3, not from scratch...  Bookmark   

but better than nothing ..wink

Preparation of phosphorus oxychloride from phosphorus trichloride via oxidation with potassium (or sodium) chlorate:

In a 100 ml round-bottom flask, equipped with a 2 necked adapter with dropping funnel and a 4-bulb Allihn condensor, 16g of finely powdered potassium chlorate are covered with 20g of phosphorus oxychloride (This is because the reaction of phosphorus trichloride with chlorates is pretty hefty, without a "thinner" even a small explosion might occur). 50g of phosphorus trichloride are then added drop by drop, the first drops cause a very strong reaction, the liquid begins to boil and it becomes colourless. After all of the trichloride has been added, the such formed phosphorus oxychloride is distilled from the flask in an oil-bath at 150°C(bath temperature]. The yield is nearly quantitative, 72.5g of oxychloride, the theoretical amount is 75.8g.
Phosphorus oxychloride is a strongly refractive, fuming liquid, specific gravity 1.7, boiling point 107.2°C. Its melting point is 1.8°C.
Note: The used apparatus has to be completely dried before the beginning of the synthesis, also the chlorate has to be dried before (in a desiccator, I'd recommend). If water is present, the phosphorus trichloride will react extremely violent with the chlorate, causing intensive colouring of the mixture from oxides of chlorine.

[Translated from: "Präparative Chemie", from L. Vanino, Vol. I, Enke Verlag, 1921]

Italics mine

Quidquid agis, prudenter agas et respice finem!