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Topic summary

Phosphorous acid

Phosphorous acid
Names IUPAC name
Phosphonic acid
Systematic IUPAC name
Phosphorous acid
Other names
Dihydroxyphosphine oxide

Dihydroxy(oxo)-λ-phosphane
Dihydroxy-λ-phosphanone
Orthophosphorous acid
Oxo-λ-phosphanediol
Oxo-λ-phosphonous acid

Metaphosphoroic acid
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard100.033.682EC Number
  • 237-066-7
1619 KEGG
RTECS number
  • SZ6400000
UNII
UN number2834
  • InChI=1S/H3O3P/c1-4(2)3/h4H,(H2,1,2,3)
    Key: ABLZXFCXXLZCGV-UHFFFAOYSA-N
  • InChI=1/H3O3P/c1-4(2)3/h4H,(H2,1,2,3)
    Key: ABLZXFCXXLZCGV-UHFFFAOYAF
  • HP(O)(OH)2: OP(=O)O
  • P(OH)3: OP(O)O
Properties H3PO3Molar mass81.99 g/mol Appearance white solid
deliquescentDensity1.651 g/cm (21 °C) Melting point73.6 °C (164.5 °F; 346.8 K) Boiling point200 °C (392 °F; 473 K) (decomposes) 310 g/100 mL Solubilitysoluble in ethanolAcidity (pKa) 1.3, 6.7 −42.5·10 cm/mol Structure pseudo-tetrahedral Hazards Occupational safety and health (OHS/OSH):
Main hazards
skin irritant GHS labelling: DangerH302, H314P260, P264, P270, P280, P301+P312, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P310, P321, P330, P363, P405, P501NFPA 704 (fire diamond)
3
0
1
Safety data sheet (SDS) Sigma-AldrichRelated compounds
Related compounds
H3PO4 (i.e., PO(OH)3)
H3PO2 (i.e., H2PO(OH))
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Phosphorous acid (or phosphonic acid) is the compound described by the formulaH3PO3. It is diprotic (readily ionizes two protons), not triprotic as might be suggested by its formula. Phosphorous acid is an intermediate in the preparation of other phosphorus compounds. Organic derivatives of phosphorous acid, compounds with the formula RPO3H2, are called phosphonic acids.

Wikipedia source