Phosphonic acid
A phosphorus oxoacid that consists of a single pentavalent phosphorus covalently bound via single bonds to a single hydrogen and two hydroxy groups and via a double bond to an oxygen. The parent of the class of phosphonic acids. — ChEBI
Safety documents & references
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Identity & molecular properties
Source-linked values| CAS number | 13598-36-2 | ChEBI ↗ |
| Molecular formula | H3O3P | ChEBI ↗ |
| Molar mass | 81.995 g/mol | ChEBI ↗ |
| Monoisotopic mass | 81.98198 Da | ChEBI ↗ |
| Formal charge | 0 | ChEBI ↗ |
| ChEBI identifier | CHEBI:44976 | ChEBI ↗ |
Cross-source molecular data
PubChem| Molar mass | 81.996 g/mol | PubChem ↗ |
| Exact mass | 81.98198095 Da | PubChem ↗ |
PubChem computed values are shown separately from the ChEBI record. An exact InChIKey match was used to connect the records. Molecular descriptors do not describe a supplied product’s purity, particle size or performance.
Names & structural identifiers
Copy any identifierphosphonic aciddihydrogen hydridotrioxophosphate(2-)ABLZXFCXXLZCGV-UHFFFAOYSA-N[H]OP([H])(=O)O[H]InChI=1S/H3O3P/c1-4(2)3/h4H,(H2,1,2,3)Names & synonyms
Names are supplied by ChEBI. Trade names and related synonyms may describe a broader product context.
Classification & relationships
ChEBI ontologyRoles recorded in ChEBI
Database role annotations describe reported biological or chemical roles; they are not product approvals or recommendations for use.
Safety classification · Japan
NITE / Japanese governmentPhosphonic acid (tautomer: Phosphorous acid) · 22A4021
| Endpoint | Reported classification |
|---|---|
| Self-reactive substances and mixtures | Type G |
| Acute toxicity （Oral） | Category 4 |
| Skin corrosion/irritation | Category 1 |
| Serious eye damage/eye irritation | Category 1 |
Selected source-reported endpoints. Other endpoints, rationales and conditions remain in the original classification. Missing or unlisted information does not mean non-hazardous. This is not a global classification or transport decision.
Read the original NITE classificationMass ↔ amount of substance
Calculated from sourced massUses 81.995 g/mol from ChEBI. Assumes the substance described by this record; no purity or concentration correction is applied.
Elemental composition
Theoretical mass fractionsOPHCalculated theoretical mass fractions from the reported formula and PubChem periodic-table atomic masses. These are not assay or purity results.
Research & patent references
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Sources & record history
Checked 27 Sep 2026Release 255, 9 September 2026. ChEBI three-star (manually annotated) source entry. View original record ↗ · CC BY 4.0
PubCAS formats source data, connects references and computes explicitly labelled conversions. CAS cross-references are supplied by ChEBI; they do not constitute CAS verification or endorsement.