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 pKa.  Using your logic, the acidity of MeOH would anticipate that OH- is ionizable, i.e. that O2- 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 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:

(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)
 * H3PO4: 2.146
 * H3PO3: 1.257
 * H3PO2: 1.244

Nomenclature
To quote from Greenwood and Earnshaw: "Phosphorous acid and phosphites [HPO(OH)2 and HPO32-]: Again, the recommended names (phosphonic acid and phosphonates) have found more general acceptance for organic derivatives such as RPO32-..." So the parent acid is ordinarily called phosphorous acid.--Smokefoot (talk) 12:17, 16 March 2019 (UTC)