Hypophosphorous acid

Hypophosphorous acid
Names
	IUPAC name Phosphinic acid
	Other names Hydroxy(oxo)-λ5-phosphane; Hydroxy-λ5-phosphanone; Oxo-λ5-phosphanol; Oxo-λ5-phosphinous acid; Phosphonous acid (for minor tautomer)
Identifiers
CAS Number	6303-21-5 ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:29031 ;
ChEMBL	ChEMBL2105054 ;
ChemSpider	10449263 ; 10459437 (17O2) ; 2342086 (2H3) ;
ECHA InfoCard	100.026.001
KEGG	D02334 ;
PubChem CID	3085127 (2H3);
UNII	8B1RL9B4ZJ ;
UN number	UN 3264
CompTox Dashboard (EPA)	DTXSID90873902 DTXSID90206211, DTXSID90873902 ;
	InChI InChI=1S/H3O2P/c1-3-2/h3H2,(H,1,2) Key: ACVYVLVWPXVTIT-UHFFFAOYSA-N ; InChI=1/H3O2P/c1-3-2/h3H2,(H,1,2) Key: ACVYVLVWPXVTIT-UHFFFAOYAQ;
	SMILES O[PH2]=O;
Properties
Chemical formula	H3PO2
Molar mass	66.00 g/mol
Appearance	colorless, deliquescent crystals or oily liquid
Density	1.493 g/cm3 1.22 g/cm3 (50 wt% aq. solution)
Melting point	26.5 °C (79.7 °F; 299.6 K)
Boiling point	130 °C (266 °F; 403 K) decomposes
Solubility in water	miscible
Solubility	very soluble in alcohol, ether
Acidity (pKa)	0.89±0.05
Conjugate base	Phosphinate
Structure
Molecular shape	pseudo-tetrahedral
Hazards
Flash point	Non-flammable
Safety data sheet (SDS)	JT Baker
Related compounds
Related phosphorus oxoacids	Phosphorous acid; Phosphoric acid
Related compounds	Sodium hypophosphite; Barium hypophosphite
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Hypophosphorous acid (HPA), or phosphinic acid, is a phosphorus oxyacid and a powerful reducing agent with molecular formula H₃PO₂. It is a colorless low-melting compound, which is soluble in water, dioxane and alcohols. The formula for this acid is generally written H₃PO₂, but a more descriptive presentation is HOP(O)H₂, which highlights its monoprotic character. Salts derived from this acid are called hypophosphites.

HOP(O)H₂ exists in equilibrium with the minor tautomer HP(OH)₂. Sometimes the minor tautomer is called hypophosphorous acid and the major tautomer is called phosphinic acid.