Phenylalanine (C9H11NO2): structure, properties and hazards

Names and identifiers

IUPAC name: (2S)-2-amino-3-phenylpropanoic acid
Synonyms: L-phenylalanine, (S)-2-Amino-3-phenylpropanoic acid, (2S)-2-amino-3-phenylpropanoic acid
+ 35 more
3-Phenyl-L-alanine, (S)-Phenylalanine, (L)-Phenylalanine, 3-Phenylalanine, beta-Phenyl-L-alanine, (S)-2-Amino-3-phenylpropionic acid, Antibiotic FN 1636, L-Alanine, phenyl-, Alanine, 3-phenyl-, fenilalanina, L-Alanine, 3-phenyl-, (S)-alpha-Amino-beta-phenylpropionic acid, Phenylalaninum, Alanine, phenyl-, L-, (S)-alpha-Aminohydrocinnamic acid, FEMA No. 3585, (S)-alpha-Amino-benzenepropanoic acid, Phenylalanine, L-, (S)-(-)-Phenylalanine, Hydrocinnamic acid, alpha-amino-, laevo-phenyl alanine, L-Phe, alpha-Aminohydrocinnamic acid, Benzenepropanoic acid, alpha-amino-, (S)-, Phenylalamine, DTXSID4040763, 47E5O17Y3R, (-)-beta-Phenylalanine, beta-Phenyl-alpha-alanine, (S)-alpha-Aminobenzenepropanoic acid, NSC-79477, CHEBI:17295, L-2-Amino-3-phenylpropionic acid, Phenyl-alpha-alanine, L-Isomer Phenylalanine
Molecular formula: C₉H₁₁NO₂
Empirical formula: C₉H₁₁NO₂
Molecular weight: 165.19 g/mol
Exact mass: 165.07898
CAS number: 63-91-2
PubChem CID: 6140
Canonical SMILES: C1=CC=C(C=C1)CC(C(=O)O)N
Isomeric SMILES: C1=CC=C(C=C1)C[C@@H](C(=O)O)N
InChI: InChI=1S/C9H11NO2/c10-8(9(11)12)6-7-4-2-1-3-5-7/h1-5,8H,6,10H2,(H,11,12)/t8-/m0/s1
InChIKey: COLNVLDHVKWLRT-QMMMGPOBSA-N
Molfile

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

Physical properties

TemperaturePressureDensity

Appearance: L-phenylalanine is an odorless white crystalline powder. Slightly bitter taste. pH (1% aqueous solution) 5.4 to 6. (NTP, 1992)[1]
Odor: Slight[2]
Melting point: 283 °C (541 °F) (decomposes) (NTP, 1992)[1]
Boiling point: 295 °C (563 °F) at 760 mmHg (sublimes) (NTP, 1992)[1]
Solubility in water: In water, 2.64 × 10⁴ mg/L at 25 °C[2]
2 values
From Hazardous Substances Data Bank (HSDB), the most authoritative source here.
Value As written Source
– 10 to 50 mg/mL at 77 °F (NTP, 1992) [1] CAMEO Chemicalscites National Toxicology Program, Institute of Environmental Health Sciences, National Institutes of Health (NTP). 1992. National Toxicology Program Chemical Repository Database. Research Triangle Park, North Carolina.
–shown In water, 2.64X10+4 mg/L at 25 °C [2] Hazardous Substances Data Bank (HSDB)cites Yalkowsky, S.H., He, Yan., Handbook of Aqueous Solubility Data: An Extensive Compilation of Aqueous Solubility Data for Organic Compounds Extracted from the AQUASOL dATAbASE. CRC Press LLC, Boca Raton, FL. 2003., p. 578
log P: log Kow = -1.38[2]
pKa: pKa = 1.24[2]

Value	As written	Source
–	10 to 50 mg/mL at 77 °F (NTP, 1992)	[1] CAMEO Chemicalscites National Toxicology Program, Institute of Environmental Health Sciences, National Institutes of Health (NTP). 1992. National Toxicology Program Chemical Repository Database. Research Triangle Park, North Carolina.
–shown	In water, 2.64X10+4 mg/L at 25 °C	[2] Hazardous Substances Data Bank (HSDB)cites Yalkowsky, S.H., He, Yan., Handbook of Aqueous Solubility Data: An Extensive Compilation of Aqueous Solubility Data for Organic Compounds Extracted from the AQUASOL dATAbASE. CRC Press LLC, Boca Raton, FL. 2003., p. 578

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: 12
Rings: 1
Aromatic rings: 1
Fraction sp³ carbons (Fsp3): 0.22
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: 153 PubChem
Stereocenters: 1 definedCIP: C2: 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

C65.44%
H6.71%
N8.48%
O19.37%

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: 0.64 Crippen (Wildman and Crippen 1999)
log S (water solubility): -1.44 ESOL (Delaney 2004), log mol/L
Synthetic accessibility: 1.88 SA score, 1 easy to 10 hard (Ertl and Schuffenhauer 2009)

Drug-likeness: Lipinski’s rule of five

Molecular weight ≤ 500: 165.19
log P ≤ 5 (Crippen): 0.64
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 98.3% (338 of 344) of all reports.[3]

First aid

Eyes: First check the victim for contact lenses and remove if present. Flush victim's eyes with water or normal saline solution for 20 to 30 minutes while simultaneously calling a hospital or poison control center. Do not put any ointments, oils, or medication in the victim's eyes without specific instructions from a physician. Immediately transport the victim after flushing eyes to a hospital even if no symptoms (such as redness or irritation) develop. Skin: Immediately flood affected skin with water while removing and isolating all contaminated clothing.[1]

Safety data sheets on the supplier’s page: Smolecule, MuseChem, AKos Consulting & Solutions.

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]CAMEO Chemicals · Public domain (NOAA) · 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]Human Metabolome Database (HMDB) · Linked only · via PubChem · retrieved 2026-10-14
[5]SpectraBase · Linked only · via PubChem · retrieved 2026-10-14
[6]MassBank Europe · Linked only · via PubChem · retrieved 2026-10-14
[7]MassBank of North America (MoNA) · CC BY 4.0 · via PubChem · retrieved 2026-10-14
[8]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%.