DDTea
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Posts: 940
Registered: 25-2-2003
Location: Freedomland
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Reduction of Phosphoric Acid
Would it be possible to reduce Ortho-Phosphoric Acid, which is the most common OTC form of Phosphoric Acid, into it's Meta- and Hypo-
derivatives? These acids are much less common, and for those interested in Organophosphorus Chemistry, much more useful.
I am particularly interested in Hypophosphoric Acid (H3PO2). It has two Hydrogens bonded directly to the Phosphorus, perhaps allowing for easy
substitutions (to allow for synthesis of Phosphonates). Metaphosphoric Acid would also be useful, perhaps for the synthesis of DFP (should my idea
about substituting the "non-acid" Hydrogens be possible).
Now, can anyone tell me if the following reaction will yield the desired results?
H3PO4 + C --> H3PO2 + CO2
Or instead of Carbon, should a better reducing Agent be used, such as Tin or Zinc? If this reaction does in fact work, what kind of temperatures
would be required? Also, would high temperatures dehydrate the Ortho-Phosphoric Acid to Pyrophosphoric Acid? Or would it simply decompose it to
Phosphine and other such things?
[Edited on 8-9-03 by Samosa]
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madscientist
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Registered: 19-5-2002
Location: American Midwest
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Heating H<sub>3</sub>PO<sub>4</sub> would initially dehydrate it to
H<sub>4</sub>P<sub>2</sub>O<sub>7</sub>. From there, it'll dehydrate further into higher polyphosphoric
acids, until you have metaphosphoric acid. You might be able to reduce metaphosphoric acid by heating it with charcoal at temperatures around that
required to generate elemental phosphorus from a phosphate, silicon dioxide, and charcoal. Metals will just react with the acid in a typical single
replacement reaction, liberating hydrogen gas.
I weep at the sight of flaming acetic anhydride.
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