Question

h3po3 undergoes disproportion reaction but h3po4 does not

Answer 1

Phosphorous acid, P(OH)3, is SAID to undergo disproportionation to phosphoric acid, H3PO4, and PH3, i.e. phosphine...on the bench I NEVER ONCE GOT THIS REACTION to work....

+IIIP(OH)3+6H++6e−→−IIIPH3+3H2O(l)

+IIIP(OH)3+H2O→H3+VPO4+2H++2e−

And so we add the former to THREE of the latter to get....

4P(OH)3→PH3+3H3PO4

And so why is it said to occur? Well, certainly P(OH)3 is unstable with respect to oxidation...whereas the FULLY oxidized acid H3PO4 might be more thermodynamically stable.