Hypophosphoric acid

Hypophosphoric acid
Names
	IUPAC name Hypodiphosphoric acid
	Other names Diphosphoric acid
Identifiers
CAS Number	7803-60-3;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:29263;
ChemSpider	22943;
PubChem CID	24536;
UNII	CY8Z35442Z;
CompTox Dashboard (EPA)	DTXSID0064886 ;
	InChI InChI=1S/H4O6P2/c1-7(2,3)8(4,5)6/h(H2,1,2,3)(H2,4,5,6) Key: TVZISJTYELEYPI-UHFFFAOYSA-N;
	SMILES OP(O)(P(O)(O)=O)=O;
Properties
Chemical formula	H4P2O6
Molar mass	161.98 g/mol
Appearance	White solid (dihydrate)
Melting point	54 °C (129 °F; 327 K)
Acidity (pKa)	2.2, 2.8, 7.3, 10.0
Conjugate base	Hypophosphate
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Hypophosphoric acid is a mineral acid with the formula H₄P₂O₆, with phosphorus in a formal oxidation state of +4. In the solid state it is present as the dihydrate, H₄P₂O₆·2H₂O. In hypophosphoric acid the phosphorus atoms are identical and joined directly with a P−P bond. Isohypophosphoric acid is a structural isomer of hypophosphoric acid in which one phosphorus has a hydrogen directedly bonded to it and that phosphorus atom is linked to the other one by an oxygen bridge to give a phosphorous acid/phosphoric acid mixed anhydride. The two phosphorus atoms are in the +3 and +5 oxidation states, respectively.