Sciencemadness Discussion Board

Phosphorous - A summary

BromicAcid - 6-5-2012 at 17:51

In celebration of the 10 year anniversary of SM (hint hint) I have decided to write up a summary of the phosphorus thread. I am attaching the crude document as a HTML file. Please, if there are any phosphorous experts out there with some time to spare look it over and give some feedback on what I missed. I am only trying to summarize what is in the thread for the most part although some new stuff did sneak in there. When it's done hopefully people who are impatient can at least look at this document before posting something that's already been discussed to death.

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Chemistry of Hydrogen Phosphides

AndersHoveland - 6-5-2012 at 18:04

Quote:

"...it is known that phosphorous acid, reduced with nascent hydrogen, yields phosphine and hypophosphorous acid,

For the formation of phosphine from phosphorous and sodium hydroxide, heated together, the following equation is usually given:
(4)P + (3)NaOH + (3)H2O --> PH3 + (3)NaH2PO2
Without a doubt the reaction is far more complicated.
...what has not been shown, that hydrogen and at least two acids of phosphorous are formed when phosphine is generated in the usual way. ...When phosphine was obtained, by heating an aqueous solution of potassium hydroxide with phosphorous, only from 10 to 40 percent of the gas obtained was phosphine [the remainder being hydrogen]. The decomposition of phosphonium iodide, PH4I, is the only method of obtaining pure phosphine."
investigation of sodamide and of its reaction-products with phosphorus" William Phillips Winter p42-43



The article goes on to say that the reaction of sodium phosphide with water generates small portions of phosphites and hydrogen gas, in addition to the main products of sodium hydroxide and phosphine.

Other sources [not referenced in this post] generally give the simplified equation for heating white P with NaOH as:

12 NaOH + P4 --> 4 Na3PO3 + 4 PH3
although this is likely not completely accurate.


Hydrogen sulfide is known to be able to reduce sulfur dioxide (actually sulfurous acid in aqueous solution) at room temperature. Perhaps phophine would similarly be able to reduce phosphorous acid (H3PO3)?

Aqueous alkali (KOH) dissolves red phopshorous, with the formation of phosphine. Interestingly, when hydrochloric acid was added to the solution, the phosphorous precipitated back into its elemental form.
Journal of the Chemical Society, Volume 75 (Great Britain) p.976

It seems apparent that hypophosphorous acid, H3PO2, is reduced by phosphine, PH3, to elemental phosphorous. The selective oxidation of PH3 by aqueous iodine also produces H3PO2. (in a similar reaction, iodine reduces thiosulfate, S2O3[-2], to tetrathionate, S4O6[-2] )

The fact that H3PO2 even exists suggests that the chemistry of the P-O bond is more similar to the C-O bond than the S-O bond, which is to say that H3PO3 is essentially not an oxidizer at ordinary temperatures, like SO2 can be. However, one paper mentions that PH3 can reduce 1-naphthol to naphthalene.
"Phosphine as a Reducing Agent" SHELDON A. BUCKLER, LOIS DOLL, FRANK K. LIND, MARTIN EPSTEIN. J. Org. Chem., 1962, 27 (3), pp 794–798
So the idea that PH3 could reduce H3PO3 is quite plausible.

Whether PH3 reacts with H3PO3 in aqeous solution is uncertain.

(the paper also describes the reaction of phosphine with nitrobenzene. There was no reaction at neutral conditions, but when sodium hydroxide was added then azoxybenzene was produced in high yield)
Quote:

"When heated by itself, hypophosphorous acid is resolved into phosphoric acid and phosphine. Phosphorous acid on heating at 200°C converts to phosphoric acid and phosphine."

It is very probable that PH3 would not reduce H3PO4, just as H2S does not reduce aqueous H2SO4. Phosphoric acid can, for example, be distilled with sodium iodide to make anhydrous hydrogen iodide, known to be a stronger reducing agent than H2S.
Quote:

When boiled in alkaline liquids [aqueous KOH] they [hypophosphites] are decomposed into phosphates and hydrogen.
KPH2O2 + (2)KHO --> K3PO4 + H4

The dry salts decompose when heated, giving phosphoretted hydrogen [PH3] (hence they are very flammable) and leaving a residue of pyrophosphate.
(2)BaP2H4O4 --> (2)PH3 + H2O + Ba2P2O7

"A dictionary of chemistry and the allied branches of other sciences, Volume 4", Henry Watts, p524



Various Other Hydrides of Phosphorous

P2H4, first obtained by P. Thenard (Comptes rendus, 1844, 18, p. 652) by decomposing calcium phosphide with warm water, the products of reaction being then passed through a U tube surrounded by a freezing mixture (see also L. Gattermann, Ber., 1890, 23, p. 1174). It is a colourless liquid which boils at 57°-58° C. It is insoluble in water, but soluble in alcohol and ether. It is very unstable, being readily decomposed by heat or light. By passing the products of the decomposition of calcium phosphide with water over granular calcium chloride, the P2H4 gives a new hydride, P12H6 and phosphine, the former being an odourless, canary-yellow, amorphous powder. When heated in a vacuum it evolves phosphine, and leaves an orange-red residue of a second new hydride, P9H2 (A. Stock, W. Bottcher, and W. Lenger, Ber., 9 9, 4 39, 47, 2853).

P4H2, first obtained by Le Verrier, is formed by the action of phosphorus trichloride on gaseous phosphine (Besson, Comptes rendus, 111, p. 972); by the action of water on phosphorus di-iodide and by the decomposition of calcium phosphide with hot concentrated hydrochloric acid. It is a yellow solid, which is insoluble in water. It burns when heated to about 200° C. When warmed with alcoholic potash it yields gaseous phosphine, hydrogen and a hypophosphite.

Interesting Non-Reactivity of Phosphorus:
Elemental phosphorous can apparently be dissolved in liquid sulfur dichloride without reaction.


Phosphine as a Reducing Agent:

Precipitated cuprous oxide [Cu2O] is acted on rapidly by phosphine at ordinary temperature, forming a grey white mass and water, the grey substance is quite insoluble in water, if air be excluded; it is [PCu3]. It melts at a red heat, is rapidly dissolved by nitric acid or bromine water, and is attacked by hot sulfuric acid, with the formation of sulfur dioxide and phosphine. It does not reduce potassium permanganate.

While phosphine acts differently on the aqueous solutions of different cupric salts, its action of the ammoniacal solutions of all of them (chloride, sulfate, nitrate, acetate, formate, hydroxide) is the same. Copper phosphide is formed in amount corresponding to two-thirds of the phosphine which disappears, while the phopshorous of the other third is found in the liquid, as phosphoric and hypophosphorous acids in molecular proportions-

(6)PH3 + (12)CuCl2 + (6)H2O + (x)NH3 --> (4)PCu3 + PO4H3 + PO2H3 + (24)HCl + (x)NH3

If, after the absorption of the phosphine, oxygen be admitted, the precipitate redissolves completely, using up a volume of oxygen double that of the phosphine absorbed in the first place.

Journal of the Society of Chemical Industry, Volume 18, p716

One paper describes the reaction of phosphine (PH3) with nitrobenzene. There was no reaction at neutral conditions, but when sodium hydroxide was added then azoxybenzene was produced in high yield. PH3 will also reduce 1-naphthol to naphthalene.
"Phosphine as a Reducing Agent"
SHELDON A. BUCKLER, LOIS DOLL, FRANK K. LIND, MARTIN EPSTEIN. J. Org. Chem., 1962, 27 (3), pp 794–798


[Edited on 7-5-2012 by AndersHoveland]

Lambda-Eyde - 6-5-2012 at 18:18

Fantastic work, BromicAcid. I haven't been very interested in phosphorus production myself, but I appreciate that you have collected and condensed the discussion into a single document. I'd like to see more of these summary articles on several topics. Potassium from KOH + Mg springs to mind.

If you'd like, I could typeset the document to create a LaTeX file and upload a pdf, .htm seems like a weird choice to me. :P Send me a U2U if you'd like me to help.

Edit: I'm by no means a phosphorus expert, but the correct spelling is phosphorus, not phosphorous! Phosphorous, as in phosphorous acid, refers to P<sup>3+</sup>... But I'm quite sure that you actually know that. :D

[Edited on 7-5-2012 by Lambda-Eyde]

BromicAcid - 7-5-2012 at 14:57

Thanks for the detailed input AndersHoveland, I'll be sure to include some of that in the summary. I have other information that I wanted to include that was not in the thread but didn't want to since it's supposed to just be a summary of the thread then I realized I could just make another post. I recently purchased the phosphorus supplement edition of the Comprehensive Treatise on Inorganic and Theoretical Chemistry which has interesting sections on phosphides that decompose to give phosphorus as well as additional information on using hydrogen to reduce phosphates that I didn't see anywhere else in the thread. Not suited for home experimentation but when it comes to phosphorus, what is?

Also, thanks Lambda, I have had issues with spelling phosphorus for some time... not sure why. I will be sure to get that corrected in the final version. As for the HTML, I wanted to link to the references at the end and it was the only available tool that I had at my disposal, the only PDF making tool I have is CutePDF but that does not create links. If you could do a final conversion of the file upon completion I would appreciate it.

As for other articles being summarized, when the Prepublication section was first created that was listed amongst the goals (to summarize long threads) however I haven't seen much work done in that area. Personally I would like to see the sodium thread summarized and put back together (electrochemical and chemical) to remake the behemoth that it used to be.

Lambda-Eyde - 7-5-2012 at 15:21

Quote: Originally posted by BromicAcid  

Also, thanks Lambda, I have had issues with spelling phosphorus for some time... not sure why. I will be sure to get that corrected in the final version. As for the HTML, I wanted to link to the references at the end and it was the only available tool that I had at my disposal, the only PDF making tool I have is CutePDF but that does not create links. If you could do a final conversion of the file upon completion I would appreciate it.

Sure, I could do that. Creating links in LaTeX is no problem at all. Just give me a holler when you're done and we can work out the details via U2U!

White Yeti - 11-5-2012 at 15:45

Nicely done! I'll make sure to read this summary. Do you want to post a link on the phosphorus page, so as to direct people to this thread? Or did you leave it out on purpose?

AndersHoveland - 11-5-2012 at 16:40

also to make an additional comment,
Quote:
"...it is known that phosphorous acid, reduced with nascent hydrogen, yields phosphine and hypophosphorous acid,"

by "nascent hydrogen" the author no doubt meant that the H3PO3 is reduced in the presence of zinc reacting with hydrochloric acid. This is from an old piece of literature, and it was commonly believed at that time that Zn + HCl produced "free hydrogen", although it was proven much later that hydrogen radicals are not actually produced, and that there is a different mechanism that exmplains these regents reducing action. Zn + HCl can also reduce nitrobenzene to aniline.

BromicAcid - 16-5-2012 at 16:22

Here is my second attempt at a final version. I have stolen the SM logo from other member publications (Polverone, any objections?) and put it into a PDF with internal links (hopefully working).

@ White Yeti: I didn't post a link from the phosphorus thread yet because I wasn't sure how long this would be a work in progress depending on how much feedback I received.



Attachment: Phosphorus Summary.pdf (204kB)
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Magpie - 16-5-2012 at 20:55

This is a wonderful summary. Thank you for your hard work and dedication!

garage chemist - 16-5-2012 at 21:44

Thank you BromicAcid. From this article and some references posted in the Phosphorus thread I am now thinking that the reduction of lead phosphate with hydrogen holds most promise.
The french article by Hutter et al. (CONTRIBUTION A L'ÉTUDE
DE L'ACTION DE L'HYDROGÈNE SUR LES PHOSPHATES) and especially the article about microscale synthesis of radiolabelled PCl3 from H3PO4 gave me hope that a medium-temperature method (600-800°C) actually does exist. Pb3(PO4)2 + H2 could well be what we are all looking for.
I missed both of these articles at the time they were posted due to not frequenting the Phosphorus thread enough, and most likely would never have stumbled over them without your summary, BromicAcid.

Also, I have the the impression that I too am guilty of speculating about theoretical methods that I know nothing about, like thermal decomposition of phosphine. The only thing that made me think that this might work is a sentence in one of my german chemistry books stating that the solid phosphines obtained from heating mono-and diphosphine "decompose further at higher temperatures". So don't take this too seriously.