Sciencemadness Discussion Board - hypophosphoric convertion

hypophosphoric convertion

white shirt/black tie - 25-12-2004 at 08:59

Can phosphoric acid be converted into hypophosphoric -and if so how?

HRH_Prince_Charles - 25-12-2004 at 16:45

No.

There are several oxyacids of phosphorus. I think the useful ones are phosphorous acid and hypophosphorous acid (phosphinic acid). You can make the acid from the phosphite salt, used as a foliar fertilizer.

solo - 25-12-2004 at 17:21

This is the synthesis of the hypophosphorous acid, you will see that the acid you want to use is nowhere in the method involved.....solo

HYPOPHOSPHOROUS ACID
[6303-21-5]
Formula: H3PO2; MW 65.997
Structure: H
|
H—P—OH
||
O
Synonym: phosphinic acid
Uses
Hypophosphorous acid is used to prepare hypophosphite salts and in electroplating
baths.
Physical Properties
Colorless deliquescent crystals or oily liquid; sour odor; density 1.493 g/cm3;
melts at 26.5°C; boils at 130°C; very soluble in water, alcohol and ether; density
of a 50% aqueous solution is 1.13 g/mL.
Thermochemical Properties
?Hf° (cry) –144,50 kcal/mol
?Hf° (liq) –142.30 kcal/mol
?Hfus 2.32 kcal/mol
Preparation
Hypophosphorous acid may be prepared by various methods:
1. Boiling white phosphorus with calcium hydroxide:
P4 + 4Ca(OH)2 + 8H2O ? 4Ca(H2PO2)2 + 4H2
The calcium salt is soluble in water. Treatment with sulfuric acid yields the
hypophosphorous acid:
(H2PO2)2Ca + H2SO4 ? 2H3PO2 + CaSO4
The product mixture is filtered to remove insoluble CaSO4. The aqueous solution
of hypophosphorous acid is concentrated under reduced pressure.
Concentrated baryta water may be used instead of calcium hydroxide.
2. By treating sodium hypophosphite, NaH2PO2 with an ion-exchange resin.
The sodium salt may be produced by boiling white phosphorus with a solution
of sodium hydroxide, a reaction similar to (1) above.

3. By oxidation of phosphine with an aqueous iodine solution: PH3 + 2I2 + 2H2O ? H3PO2 + 4HI The above method may be considered safer than that involving heating whitephosphorus with an alkali.Hypophosphorous acid must be stored below 50°C. It is sold commerciallyas an aqueous solution at various concentrations. Reactions Pure hypophosphorous acid is a monobasic acid, pKa=1.2. It reacts withbases forming the corresponding salts: H3PO2 + NaOH ? NaH2PO2 + H2O It decomposes rapidly on heating above 100°C to orthophosphoric acid andphosphine: 100o C2H3PO2 ??? H3PO4 + PH3? The phosphorus atom in hypophosphorus acid is in the lowest oxidation state,+1. The compound is, therefore, a powerful reducing agent. It combines readily
and often explosively with oxidizing agents. For example, the acid reducesmercury(II) nitrate or mercury(II) oxide into mercury metal violently. AnalysisElemental composition: H 4.58%, P 46.94%, O 48.49%. The hypophosphiteion may be oxidized to orthophosphate by careful oxidation. Theorthophophate, PO43¯ ion, may be measured by colorimetry either by usingammonium molybdate and vanadium (yellow color), ammonium molybdateand stannous chloride (blue color), or ammonium molybdate, potassium antimonyl
tartrate and asorbic acid (an intense blue color). Absorbances of thesolution are read at 400 (or 470), 650 (or 690) and 880 nm, respectively.Hypophosphite ion alternatively may be identified by ion chromatography. Hazard The compound is a very powerful reducing agent. Reactions with oxidizingagents may progress to explosive violence (See Reactions). Also, heating thiscompound above 100°C can produce toxic phosphine, which also may explodein air.

....as read in Handbook of Inorganic Chemicals
Pradyot Patnaik, Ph.D.

[Edited on 26-12-2004 by solo]

cyclonite4 - 25-12-2004 at 19:13

@white shirt/black tie (previous username: white shrit/black tie, probably changed because of spelling error

): You seem to have much interest in phosphorus, what plans do you have for it? I'm just curious

600538411 - 17-6-2005 at 18:29

As stated above, Hypophosphorus Acid can be synthesised from Elemental Phosporus (aka White Phos) but still this leaves me wondering... Is it possible to get rid of that annoying double bonded oxygen in phosphoric acid (H3PO4) to form Phosphorus acid (H3PO3)?

Any help would be greatly appreciated

12AX7 - 17-6-2005 at 21:10

Would it be possible to roast with carbon, or would that only go right to P as is industrial process?

Tim

BromicAcid - 17-6-2005 at 21:36

Although the phosphate anion is reluctant to be reduced I am sure there is some combination of dry phosphate and a reducing agent such as a metal powder that could be taken advantage of that, upon heating, would give appreciable amounts of the reduced anion, vaguely smiliar to the methods to make nitrite from nitrate using lead as the reducing agent. The key of course finding the best combination of reactants and in doing so determining the relative amounts of your desired product being produced. Separation would be somewhat easy, if for example zinc or aluminum used then dissolution in water, basification to give the precipiated hydroxide followed by filtering, leaving you with the salt of whatever salt you origionally threw in the mix.

600538411 - 18-6-2005 at 06:03

So there is no patented writeups related to this topic it would be shear exerimental chemistry at it's finest?

Handbook of inorganic chemicals available for download !

Lambda - 19-6-2005 at 10:45

Quote:

Originally posted by solo 26-12-2004
....as read in Handbook of Inorganic Chemicals
Pradyot Patnaik, Ph.D.

Handbook of inorganic chemicals available for download !.

Patnaik P. Handbook of inorganic chemicals (3.72 mb)
http://rapidshare.de/files/2487499/Patnaik_P._Handbook_of_in...

Quote:

All good things come to those who wait patiently.

600538411 - 20-6-2005 at 14:36

Hmm interesting read... Was reading with Carbon and alot of heat you can take Phosphoric acid back to "Elemental Phosphorus" (As stated by Tim above) for which you could synth either Hypo or Ortho Phosphorus Acid... I didn't really want to have to go back that far though (Due to dangers of Phospine gas and Homemade WP still seems to be in the experimental stages in the dedicated thread on these forums...)

OK so I am still on the hunt...

[Edited on 20-6-2005 by 600538411]

[Edited on 20-6-2005 by 600538411]

harderm - 6-4-2015 at 22:00

All of the synthetic methods I've seen here seem to involve the use or production of elemental phosphorous or phosphine. Both of these are hazardous materials, and I would like to avoid them. Also, both of them, as well as hypophosphorous acid and its salts, are listed precursors watched by the DEA. :mad:

Importing and handling them legally requires a license that costs hundreds of dollars to obtain - Not to mention the inventorying and reporting requirements.... I want hypophosphorous acid or some salt of it to use in chemical metallurgy experiments - to reduce precious metal salts by environmentally safe methods. I don't need a lot, yet the route seems completely blocked to a small-scale experimentalist with innocent intentions. If anyone knows of a way to accomplish what I want, please let me know.

Amos - 7-4-2015 at 04:57

Am I the only one that correctly read the post as hypophosphorIC acid, and not hypophosphorOUS? I mean, sure, they might be getting it wrong, but you can't all just assume that.

woelen - 7-4-2015 at 05:32

What is hypophosphoric acid? I know
1) phosphoric acid: O=P(OH)3, tribasic
2) phosphorous acid: O=P(H)(OH)2, dibasic, one H directly connected to P
3) hypophosphorous acid: O=P(H)2(OH), monobasic, two H's directly connected to P

I do not know of hypophosphoric acid. Phosphoric acid can form condensation products, but it still contains phosphorus in oxidation state +5. Examples are pyrophosphoric acid, which is (HO)2(O)P-O-P(O)(OH)2, which can be considered as a combination of two molecules of phosphoric acid by removal of water, and metaphosphoric acid, (HPO3)n. But these are not hypo-acids, the prefix hypo is used for lower oxidation states.

EDIT: I did a google search on hypophosphoric acid. Most hits mention hypophosphorous acid, but one link indeed mentions a remarkable acid, which is similar to pyrophosphoric acid, but without the O between the two P-atoms, hence (HO)2(O)P-P(O)(OH)2 with a direct link between the two phosphorus atoms:

http://www.chemspider.com/Chemical-Structure.22943.html

There even is a wiki-page about this acid. I learnt something new

http://en.wikipedia.org/wiki/Hypophosphoric_acid

[Edited on 7-4-15 by woelen]

Yuehuizhou - 8-4-2017 at 10:45

The formal oxidation state of hypophosphoric acid is +4, between phosphorous acid (+3) and phosphoric acid (+5).

Magpie - 8-4-2017 at 12:15

Hypophosphorous acid, H3PO2, and its salts, don't seem to be available OTC in the US. H3PO2 would be useful for removing -NH2 from arenes. Of course, it also has uses in drug cookery and so is proscribed by the DEA.

The potassium salts of phosphorous acid, H3PO3, are available OTC in ~50% aqueous solutions as treatment for root rot. Offhand I don't know of what value these may be to the home chemist.

Panache - 9-4-2017 at 07:15

Ok no-0ne can post again in this thread until 2019, going by the spacings between previous posts.
Also what is a convertion?

[Edited on 9-4-2017 by Panache]

Magpie - 10-4-2017 at 18:34

Panache I'm going to break your rule. I'm getting pissed thinking about how useful H3PO2 would be:

Say you need to add a functional group to a benzene ring. In one case you need a meta director, in another you need an o,p director. Temporary addition of an -NO2 or an -NH2 would work. Then when done reduce the -NO2 to -NH2, as required. The -NH2 is then removed by H3PO2 after diazotization. :mad:

[Edited on 11-4-2017 by Magpie]

Cryolite. - 10-4-2017 at 22:23

And it's extremely good at reducing benzylic alcohols to alkanes... (no, not that substrate) It would also probably be a great hydrogen donor for transfer hydrogenation, although I haven't tried this. It's also a good way to introduce phosphorus into an organic compound and also has a rich radical chemistry. Thankfully I managed to source some

Magpie - 11-4-2017 at 12:56

I suppose if I wanted it bad enough I could synthesize it from white P.