Talk:Phosphorous acid

Is the phosphite H of phosphorous acid not ionisable? the corresponding H in the corresponding esters (such as diethyl phosphite) can be easily removed with bases such as NaH, in a preparatively useful manner. it isn't too much of a stretch to think the same applies to phosphorous acid. Xcomradex 22:57, 25 June 2006 (UTC)

Ah ha. i am correct, eg. trisodium phosphite CAS# 22620-95-7. removed comment from main page. Xcomradex 23:01, 25 June 2006 (UTC)

My two-cents worth - the hazard/flaw in this style of thinking is that HP(O)(OEt)₂ is charge-neutral whereas [HPO₃]^2- is a dianion. Charge strongly affects pK_a. Using your logic, the acidity of MeOH would anticipate that OH^- is ionizable, i.e. that O^2- would be stable in soln. It is plausible that the proton in [HPO₃]^2- is ionizable, but the existence of Na₃[PO₃] does not prove this. For one thing, what would this stuff be soluble in? Na₂O and Na₃P are also known, but they have no solution chemistry.--Smokefoot 00:48, 26 June 2006 (UTC)

Yeah i had thought as much too. but a quick look at trisodium phosphite shows it is prepared industrially by treating white P with NaOH, which implies deprotonation occurs, if not directly then via the phosphite tautomer. these conditions are much more mild than i would have expected, so i'm starting to think the phosphite tautomer is directly involved. incidently, patents exist for preparing aqueous H₃PO₃ from aqueous Na₃PO₃ (eg. US4278647) so the compound of sufficent utility to have attracted commercial interest, and it has aqueous solution chemistry. my two cents anyway. Xcomradex 23:30, 28 June 2006 (UTC)

Xcomradex: amazing and nifty chemical factoid. Like you say, if NaOH can be used, then something is deprotonatable.Thanks for taking the time to comment. Best wishes,--Smokefoot 23:47, 28 June 2006 (UTC)

No worries, thanks for trying to keep me honest. its good to see stuff isn't getting put in the wiki chemistry section without people looking over it. i see you do a fair bit of editing too, good luck. Xcomradex 06:10, 29 June 2006 (UTC)

Just thought I'd throw in my two cents worth. As it also says in the article, the P bound H doesn't deprotonate. There's no such thing as Na₃PO₃. Boiling P4 and NaOH gives NaHPO₃ - actually the main product of said procedure is NaH₂PO₂ as well as a fair bit of phosphine. Sveingold (talk) 22:09, 11 October 2009 (UTC)

image-bond lengths etc actually relates to the solid form

The image is IMHO misleading. The dimensions are those found in the solid which is extensivelly H bonded--Axiosaurus (talk) 12:15, 24 March 2008 (UTC)

Also conflict between picture (which takes dimensions from this paper doi:10.1002/zaac.19905910103 and the article which uses Wiberg. Does anyone know where Wiberg took its data from?--Axiosaurus (talk) 09:42, 25 March 2008 (UTC)

The phosphonic acid article

In the phosphonic acid article (unreferenced) it mentions the two tautomeric forms one, [P(OH)₃] named phosphorous acid and the other, [PHO(OH)₂], phosphonic. Is there a ref for the equilibrium? Wiber g just says lies entirely to the right i.e (HPO(OH)₂.Re name is there a right answer or are, in the confusing world of P acid naming, both sort of right? --Axiosaurus (talk) 12:23, 24 March 2008 (UTC)

I just thought I'd clean this up a bit. The section on phosphine generation is scientifically true but this is really not the way to generate phosphine - check out www.cytec.com for instance to convince yourself that phosphine is really delivered in lecture bottles and not generated from phosphorous acid - that'd be very messy. Also the reference to its use as fertilizer is incorrect, if the author had bothered to read the quoted article he/she would have noticed that no direct fertilizer effect is associated with phosphorous acid. Sveingold (talk) 22:10, 11 October 2009 (UTC)

Lede crap

if you take 1 mol of H3PO3 and add 3 mol of NaOH you get 1 mol of Na3PO3 plus some water

simple as that —Preceding unsigned comment added by 70.180.238.179 (talk) 22:33, 7 January 2011 (UTC) It's really not simple as that - two protons are bound to P via O and thus take part in acid-base reactions, the third P-H bound hydrogen really doesn't. Try it out for yourself in the lab or check Gmelins Handbuch or such. — Preceding unsigned comment added by 82.176.180.229 (talk) 22:12, 10 October 2012 (UTC)

First pka

Are you sure the first pka for phosphorous acid is 1.3? I have found many times a pka for phosphorous acid of 2.0. and in the french Wikipedia version, the specified pka is 2.0. I think the true pka is 2.0, as I use phosphorous acid and I measured pH of H3PO3 solutions, it looks close to a pH of 2. Any comments?? Thanks in advance Tom — Preceding unsigned comment added by 193.8.28.49 (talk) 07:42, 15 February 2016 (UTC)

Thank you for leaving a note. According to Greenwood and Earnshaw refer to a report that describes these pKa's at RT:

• H₃PO₄: 2.146
• H₃PO₃: 1.257
• H₃PO₂: 1.244

(John W. Larson, Margaret Pippin "Thermodynamics of ionization of hypophosphorous and phosphorous acids. Substituent effects on second row oxy acids" Polyhedron 1989, volume 8, pages 527–530. doi:10.1016/S0277-5387(00)80751-2). I always assumed that phosphoric was the strongest acid.--Smokefoot (talk) 19:19, 15 February 2016 (UTC)

Nomenclature

To quote from Greenwood and Earnshaw: "Phosphorous acid and phosphites [HPO(OH)₂ and HPO₃^2-]: Again, the recommended names (phosphonic acid and phosphonates) have found more general acceptance for organic derivatives such as RPO₃^2-..." So the parent acid is ordinarily called phosphorous acid.--Smokefoot (talk) 12:17, 16 March 2019 (UTC)