Leucine (C6H13NO2): structure, properties and hazards

Names and identifiers

IUPAC name: (2S)-2-amino-4-methylpentanoic acid
Synonyms: L-leucine, (S)-2-Amino-4-methylpentanoic acid, (S)-Leucine
+ 35 more
(2S)-2-amino-4-methylpentanoic acid, (S)-(+)-Leucine, Leucin, (S)-2-Amino-4-methylvaleric acid, L-alpha-Aminoisocaproic acid, LEUCINE, L-, Leucinum, Leucina, FEMA No. 3297, (2S)-alpha-leucine, L-leucin, 2-amino-4-methylvaleric acid, L-(-)-2-Amino-4-methylpentanoic acid, alpha-Aminoisocaproic acid, L-Leuzin, Leucine, l, NSC-46709, (2S)-alpha-2-amino-4-methylvaleric acid, GMW67QNF9C, L-Leu, DTXSID9023203, CHEBI:15603, (2S)-2-amino-4-methylpentanoate, L-Isomer Leucine, CHEBI:25017, NSC9252, L-Leucine High, L-Leucine 7413, RefChem:6453, L-Leucine High 7414, 2-Aminoisobutylacetic acid, DTXCID903203, 200-522-0, (2S)-2-azaniumyl-4-methylpentanoate, H-Leu-OH
Molecular formula: C₆H₁₃NO₂
Empirical formula: C₆H₁₃NO₂
Molecular weight: 131.17 g/mol
Exact mass: 131.09463
CAS number: 61-90-5
PubChem CID: 6106
Canonical SMILES: CC(C)CC(C(=O)O)N
Isomeric SMILES: CC(C)C[C@@H](C(=O)O)N
InChI: InChI=1S/C6H13NO2/c1-4(2)3-5(7)6(8)9/h4-5H,3,7H2,1-2H3,(H,8,9)/t5-/m0/s1
InChIKey: ROHFNLRQFUQHCH-YFKPBYRVSA-N
Molfile

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

Physical properties

Appearance: White crystals[2]
2 values
From Hazardous Substances Data Bank (HSDB), the most authoritative source here.
Value As written Source
– Dry Powder [1] EPA Chemical Data Reporting (CDR)
–shown White crystals [2] Hazardous Substances Data Bank (HSDB)cites Lewis, R.J. Sr.; Hawley's Condensed Chemical Dictionary 15th Edition. John Wiley & Sons, Inc. New York, NY 2007., p. 752
Solubility in water: In water, 2.15 × 10⁴ mg/L at 25 °C[2]
log P: log Kow = -1.52[2]
pKa: pKa = 2.35[2]

Value	As written	Source
–	Dry Powder	[1] EPA Chemical Data Reporting (CDR)
–shown	White crystals	[2] Hazardous Substances Data Bank (HSDB)cites Lewis, R.J. Sr.; Hawley's Condensed Chemical Dictionary 15th Edition. John Wiley & Sons, Inc. New York, NY 2007., p. 752

Each value as its source reports it, with the source's number after it (listed under References). Where several sources report a property, the row shows the value most of them agree on, the rule the app uses; open the values to see every one.

Calculated

Heavy atoms: 9
Rings: 0
Aromatic rings: 0
Fraction sp³ carbons (Fsp3): 0.83
H-bond donors: 2
H-bond acceptors: 2 computed here · PubChem 3
Rotatable bonds: 3
TPSA (Å²): 63.3
Formal charge: 0
XLogP3: -1.5 PubChem
Complexity: 101 PubChem
Stereocenters: 1 definedCIP: C5: S
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

C54.94%
H9.99%
N10.68%
O24.39%

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: 0.44 Crippen (Wildman and Crippen 1999)
log S (water solubility): -0.74 ESOL (Delaney 2004), log mol/L
Synthetic accessibility: 2.4 SA score, 1 easy to 10 hard (Ertl and Schuffenhauer 2009)

Drug-likeness: Lipinski’s rule of five

Molecular weight ≤ 500: 131.18
log P ≤ 5 (Crippen): 0.44
H-bond donors ≤ 5: 2
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

This chemical does not meet GHS hazard criteria for 100% (208 of 208) of all reports.[3]

Safety data sheets on the supplier’s page: Alfa Chemistry, J&H Chemical Co.,ltd, Aladdin Scientific.

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]EPA Chemical Data Reporting (CDR) · Public domain (US EPA) · via PubChem · retrieved 2026-10-14
[2]Hazardous Substances Data Bank (HSDB) · Public domain (US NLM) · via PubChem · retrieved 2026-10-14
[3]European Chemicals Agency (ECHA) · ECHA legal notice: reuse with acknowledgement · via PubChem · retrieved 2026-10-14
[4]NMRShiftDB · Linked only · via PubChem · retrieved 2026-10-14
[5]Human Metabolome Database (HMDB) · Linked only · via PubChem · retrieved 2026-10-14
[6]SpectraBase · Linked only · via PubChem · retrieved 2026-10-14
[7]MassBank Europe · Linked only · via PubChem · retrieved 2026-10-14
[8]MassBank of North America (MoNA) · CC BY 4.0 · via PubChem · retrieved 2026-10-14
[9]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%.