Isoxazole (C3H3NO): structure, properties and hazards

Names and identifiers

IUPAC name: 1,2-oxazole
Synonyms: 1,2-oxazole, azoxole, 1-Oxa-2-azacyclopentadiene
+ 36 more
Isoxazoles, 00SRW0M6PW, NSC-137774, DTXSID7059775, CHEBI:35595, RefChem:150159, DTXCID9037874, CHEBI:55373, 206-018-7, Isooxazole, MFCD00003149, UNII-00SRW0M6PW, 2-azafuran, EINECS 206-018-7, Isoxazole, 99%, NSC 137774, SCHEMBL1318, SCHEMBL3224, SCHEMBL9621, SCHEMBL9672, CHEMBL13257, SCHEMBL216484, SCHEMBL348146, SCHEMBL393230, SCHEMBL448614, orb1221602, orb1299765, SCHEMBL1664715, STR08895, BDBM50664237, NSC137774, SBB071031, AKOS005254996, CS-W011365, FI02593, HY-W010649
Molecular formula: C₃H₃NO
Empirical formula: C₃H₃NO
Molecular weight: 69.06 g/mol
Exact mass: 69.02146
CAS number: 288-14-2
PubChem CID: 9254
Canonical SMILES: C1=CON=C1
Isomeric SMILES: C1=CON=C1
InChI: InChI=1S/C3H3NO/c1-2-4-5-3-1/h1-3H
InChIKey: CTAPFRYPJLPFDF-UHFFFAOYSA-N
Molfile

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

Calculated

Heavy atoms: 5
Rings: 1
Aromatic rings: 1
Fraction sp³ carbons (Fsp3): 0
H-bond donors: 0
H-bond acceptors: 2
Rotatable bonds: 0
TPSA (Å²): 26
Formal charge: 0
XLogP3: 0.1 PubChem
Complexity: 30 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

C52.17%
H4.38%
N20.28%
O23.17%

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: 0.67 Crippen (Wildman and Crippen 1999)
log S (water solubility): -1.43 ESOL (Delaney 2004), log mol/L
Synthetic accessibility: 4.23 SA score, 1 easy to 10 hard (Ertl and Schuffenhauer 2009)

Drug-likeness: Lipinski’s rule of five

Molecular weight ≤ 500: 69.06
log P ≤ 5 (Crippen): 0.67
H-bond donors ≤ 5: 0
H-bond acceptors ≤ 10: 2

Passes all four rules.

¹³C NMR shifts, predicted

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: 151 company reports to ECHA. Source [1].

Flammable
Corrosive

H225Highly Flammable liquid and vapor
H314Causes severe skin burns and eye damage (69.5% of reports)
H318Causes serious eye damage (68.9% of reports)

Precautionary statements: P210, P233, P240, P241, P242, P243, P260, P264, P264+P265, P280, P301+P330+P331, P302+P361+P354, P303+P361+P353, P304+P340, P305+P354+P338, P316, P317, P321, P363, P370+P378, P403+P235, P405, P501

Safety data sheets on the supplier’s page: abcr GmbH, Aladdin Scientific, ChemoSapiens.

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]European Chemicals Agency (ECHA) · ECHA legal notice: reuse with acknowledgement · via PubChem · retrieved 2026-10-14
[2]NMRShiftDB · Linked only · via PubChem · retrieved 2026-10-14
[3]SpectraBase · Linked only · via PubChem · retrieved 2026-10-14
[4]MassBank of North America (MoNA) · CC BY 4.0 · via PubChem · retrieved 2026-10-14
[5]NIST Mass Spectrometry Data Center · Linked only · via PubChem · retrieved 2026-10-14
[6]MassBank Europe · Linked only · 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.

Isomers in the library

Oxazole