Posted 26 May 2005 - 03:11 AM
Posted 26 May 2005 - 03:51 AM
Well more of a guess then anything but I'd say that the resonance form of the conjugate base finds additional stability from the pair of electrons that form the P-H bond.
Or maybe it's stabler because of less steric hinderence with it's resonance form..
Posted 26 May 2005 - 10:39 PM
Posted 27 May 2005 - 01:59 AM
Posted 27 May 2005 - 02:31 AM
i must disagree. the phosphorus in phosphorous acid is trivalent with the oxygen... ....in the structure shown in your link, phosphorus makes 4 bonds.
No it's pentavalent. Common states for phosphorus are -3, +3, +5
No acutally if you'd like to count again you'd notice that it makes 5 bonds; 1 with the hydrogen and 4 with the oxygen's (2 single bound, 1 double bonded).
5 bond is very common for phosphorus.
It's the same with Phosphoric acid except one of the oxygens is missing and the hydrogen is directly bonded to the Phosphorus
Anyways I KNOW I am correct. Why don't you just go look up the structure from a reputible source and find out for yourself.
The source I supplied (PubChem) is a very good one, very reliable. It's actually a new offshoot directory from NCBI.
I didn't draw that myself...
Here's another http://www.chemicall...HOROUS ACID.htm
But please go prove it for yourself if you can't take my word.
Posted 27 May 2005 - 03:10 AM
i know that +5 is common for phosphorus, but please consider the fact that phosphorus is commonly found at +3. consider the halides of phosphorus; it is comparatively much more difficult to bring phosphorus to +5 than +3.
i have seen my share of images of the structure you present as well as the structure i proposed.
Posted 27 May 2005 - 03:25 AM
Considering the halides doesn't prove anything. Both PCl3 and PCl5 are common.
I can't really think of any other way to explain it. If you can't take my word there isn't much more I can say.
Maybe someone else can clear up this stalemate...
Posted 27 May 2005 - 03:57 AM
Posted 27 May 2005 - 04:16 AM
Posted 27 May 2005 - 05:04 AM
Posted 27 May 2005 - 05:26 AM
due to less hindered overlap of the p orbitals in forming the resonance conditions. Those Oxigens need to be planar when fully dissacociated to resonate and 3 would fit better then 4...
Or due to the closer proximity of the H on the H-P bond helps stabalize the negative charge on the oxygen....
Posted 27 May 2005 - 01:04 PM
So I would have to say that phosphorus acid is more acidic than phosphoric acid due to its lower number of acidic hydrogens, and the stability of the conjugate base upon coversion to hydrogenphosphate.
Posted 2 June 2005 - 03:22 AM
Just go to google and search (acidity of H3PO4, H3PO3, it's the first one on the page) or use the html version(not very clear, missing images)
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