Nitrous acid

Athanor · official

HNO₂ · 47.014 g/mol

Inorganic

Open in Athanor

Drawn from its SMILES with RDKit

DangerFatal if swallowed · Causes severe skin burns and eye damage · Causes serious eye damage · Very toxic to aquatic life

Names and identifiers

IUPAC name: nitrous acid
Synonyms: Nitrosyl hydroxide, HNO2, Kyselina dusite
+ 33 more
dioxonitric acid, hydroxidooxidonitrogen, Acid, Nitrous, T2I5UM75DN, hydrogen dioxonitrate(1-), DTXSID7064813, CHEBI:25567, (NO(OH)), [NO(OH)], RefChem:6071, DTXCID4048014, 231-963-7, HONO, Kyselina dusite [Czech], EINECS 231-963-7, UNII-T2I5UM75DN, HSDB 7801, Nitrogen dioxide ion, Nitrous acid, trans, Nitrogen peroxide ion, NITROUS ACID [MI], SCHEMBL1057, SCHEMBL9214, SCHEMBL9215, SCHEMBL809291, CHEMBL1161681, BLNWTAHYTCHDJH-UHFFFAOYSA-N, DB09112, DB-255799, NS00076377, C00088, Q207895, Q211891
Molecular formula: HNO₂
Empirical formula: HNO₂
Molecular weight: 47.014 g/mol
Exact mass: 47.00073
CAS number: 7782-77-6
PubChem CID: 24529
Canonical SMILES: N(=O)O
Isomeric SMILES: N(=O)O
InChI: InChI=1S/HNO2/c2-1-3/h(H,2,3)
InChIKey: IOVCWXUNBOPUCH-UHFFFAOYSA-N
Molfile

Names, InChI and the identifiers from PubChem, retrieved 2026-10-14.

Calculated

Heavy atoms: 3
Rings: 0
Aromatic rings: 0
Fraction sp³ carbons (Fsp3): 0
H-bond donors: 1
H-bond acceptors: 2 computed here · PubChem 3
Rotatable bonds: 0
TPSA (Å²): 49.7
Formal charge: 0
XLogP3: -0.3 PubChem
Complexity: 10 PubChem
Stereocenters: None
Double-bond geometry: None specified
Point group: Cs of one 3D conformer with its hydrogens, by Athanor’s engine (as in the app)

Elemental analysis

H2.14%
N29.79%
O68.06%

Isotope pattern

Each peak is a nominal mass with its abundance-weighted exact mass, as a percentage of the tallest, from IUPAC natural isotope abundances.

Computed from the structure with RDKit 2026.09 when this page was built, beside PubChem's own computed values from its record; where the two differ, both are shown.

Predicted

log P: 0.14 Crippen (Wildman and Crippen 1999)
log S (water solubility): -0.22 ESOL (Delaney 2004), log mol/L
Synthetic accessibility: 3.03 SA score, 1 easy to 10 hard (Ertl and Schuffenhauer 2009)

Drug-likeness: Lipinski’s rule of five

Molecular weight ≤ 500: 47.01
log P ≤ 5 (Crippen): 0.14
H-bond donors ≤ 5: 1
H-bond acceptors ≤ 10: 2

Passes all four rules.

Predictions, not measurements; each names its method. A measured log P, where a source reports one, is under Physical properties.

Safety

Danger

Most widely reported: 2 company reports to ECHA. Source [2].

Corrosive
Acute toxicity
Environmental hazard

H300Fatal if swallowed (50% of reports)
H314Causes severe skin burns and eye damage
H318Causes serious eye damage
H400Very toxic to aquatic life (50% of reports)

Precautionary statements: P260, P264, P264+P265, P270, P273, P280, P301+P316, P301+P330+P331, P302+P361+P354, P304+P340, P305+P354+P338, P316, P317, P321, P330, P363, P391, P405, P501

Incompatibilities

Reacts violenty with (phosphine) and (phosphorus trichloride). Reactions with 1-amino-5-nitrophenol, ammonium decahydroborate(2-), hydrazine (product is hydrogen azide); may give explosive products. Incompatibilities with anilines (e.g., 4-bromoaniline, 2-chloroaniline, 3-chloroaniline, 2-nitroaniline, 3-nitroaniline, 4-nitroaniline, aniline), semicarbazone, silver nitrate.[1]

Safety data sheets on the supplier’s page: Quality Control Solutions (QCS Standards), EvitaChem, Cooke Chemical Co., Ltd.

Always read the supplier’s safety data sheet before working with it.

Spectra

Experimental spectra held by these sources; each link opens the source's own record.

Literature

Reading PubChem, OpenAlex and GSRS…

Bioactivity

Reading ChEMBL…

References

[1]Hazardous Substances Data Bank (HSDB) · Public domain (US NLM) · via PubChem · retrieved 2026-10-14
[2]European Chemicals Agency (ECHA) · ECHA legal notice: reuse with acknowledgement · via PubChem · retrieved 2026-10-14
[3]NIST Mass Spectrometry Data Center · Linked only · via PubChem · retrieved 2026-10-14
[4]MassBank of North America (MoNA) · CC BY 4.0 · via PubChem · retrieved 2026-10-14
·Calculated values: computed by Athanor with RDKit 2026.09 from the structure.
·Literature on PubChem

Data last updated 2026-10-14.