alpha-Ketobutyric acid (C4H6O3): structure, properties and hazards

Names and identifiers

IUPAC name: 2-oxobutanoic acid
Synonyms: 2-oxobutanoate, alpha-ketobutyrate, 2-oxobutanoic acid
+ 36 more
2-ketobutyric acid, 2-oxobutyric acid, BUTANOIC ACID, 2-OXO-, 3-Methylpyruvic acid, Ketobutyrate, 2-oxobutyrate, 2-Ketobutanoic acid, Butyric acid, 2-oxo-, alpha-Oxo-n-butyric acid, alpha-oxobutyric acid, alpha-Oxobutyrate, FEMA No. 3723, B92RB6HY1A, NSC-60533, DTXSID9060524, CHEBI:30831, CHEBI:16763, I+--Ketobutyric acid, RefChem:555766, DTXCID5042740, 209-986-9, 2-Oxobutanoate, Propionylformic acid, Pyruvic acid, methyl-, Formic acid, propionyl-, 2-Oxo-n-butyric acid, 3-methyl pyruvic acid, 2-oxo-butyrate, a-Ketobutyric acid, 2-oxo-butanoic acid, alpha-Ketobutric acid, .alpha.-Oxobutyric acid, 2-keto-butyrate, alpha-Keto-n-butyric acid, .alpha.-Oxo-n-butyric acid, MFCD00004164
Molecular formula: C₄H₆O₃
Empirical formula: C₄H₆O₃
Molecular weight: 102.09 g/mol
Exact mass: 102.03169
CAS number: 600-18-0
PubChem CID: 58
Canonical SMILES: CCC(=O)C(=O)O
Isomeric SMILES: CCC(=O)C(=O)O
InChI: InChI=1S/C4H6O3/c1-2-3(5)4(6)7/h2H2,1H3,(H,6,7)
InChIKey: TYEYBOSBBBHJIV-UHFFFAOYSA-N
Molfile

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

Calculated

Heavy atoms: 7
Rings: 0
Aromatic rings: 0
Fraction sp³ carbons (Fsp3): 0.5
H-bond donors: 1
H-bond acceptors: 2 computed here · PubChem 3
Rotatable bonds: 2
TPSA (Å²): 54.4
Formal charge: 0
XLogP3: 0.1 PubChem
Complexity: 95 PubChem
Stereocenters: None
Double-bond geometry: None specified
Point group: C1 of one 3D conformer with its hydrogens, by Athanor’s engine (as in the app)

Elemental analysis

C47.06%
H5.92%
O47.01%

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: 0.05 Crippen (Wildman and Crippen 1999)
log S (water solubility): -0.37 ESOL (Delaney 2004), log mol/L
Synthetic accessibility: 2.37 SA score, 1 easy to 10 hard (Ertl and Schuffenhauer 2009)

Drug-likeness: Lipinski’s rule of five

Molecular weight ≤ 500: 102.09
log P ≤ 5 (Crippen): 0.05
H-bond donors ≤ 5: 1
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

Warning

Most widely reported: 1,442 company reports to ECHA. Source [1].

Harmful or irritant

H315Causes skin irritation (99.8% of reports)
H319Causes serious eye irritation (99.8% of reports)
H335May cause respiratory irritation (99.7% of reports)

Precautionary statements: P261, P264, P264+P265, P271, P280, P302+P352, P304+P340, P305+P351+P338, P319, P321, P332+P317, P337+P317, P362+P364, P403+P233, P405, P501

Safety data sheets on the supplier’s page: RR Scientific, Combi-Blocks, Biosynth.

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]Human Metabolome Database (HMDB) · Linked only · via PubChem · retrieved 2026-10-14
[3]SpectraBase · Linked only · via PubChem · retrieved 2026-10-14
[4]MassBank Europe · Linked only · via PubChem · retrieved 2026-10-14
[5]MassBank of North America (MoNA) · CC BY 4.0 · via PubChem · retrieved 2026-10-14
[6]NIST Mass Spectrometry Data Center · 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.

Similar structures

Tanimoto similarity on Morgan fingerprints (radius 2) with RDKit 2026.09, at least 45%.