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Proline

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C5H9NO2 · 115.13 g/mol

IUPAC name: (2S)-pyrrolidine-2-carboxylic acid

Also called L-proline

Amino acids
Open in Athanor
The structure of Proline
Drawn from its SMILES with RDKit

Names and identifiers

IUPAC name
(2S)-pyrrolidine-2-carboxylic acid
Synonyms
L-proline, L-(-)-Proline, (2S)-pyrrolidine-2-carboxylic acid
+ 35 more

(S)-Pyrrolidine-2-carboxylic acid, (-)-Proline, 2-pyrrolidinecarboxylic acid, (-)-(S)-Proline, (S)-2-Pyrrolidinecarboxylic acid, prolina, Prolinum, (S)-Proline, (-)-2-Pyrrolidinecarboxylic acid, L-Prolin, L-alpha-Pyrrolidinecarboxylic acid, (S)-2-Carboxypyrrolidine, Prolinum [Latin], FEMA No. 3319, 2-Pyrrolidinecarboxylic acid, (S)-, PRO (IUPAC abbreviation), CB 1707, AI3-26710, L-Pro, 9DLQ4CIU6V, NSC 46703, L-2-pyrrolidinecarboxylic acid, NSC-46703, Prolin, DTXSID5044021, CHEBI:17203, Prolinum (Latin), (2S)-pyrrolidin-1-ium-2-carboxylate, CHEBI:26271, l proline, NSC46703, pyrrolidin-1-ium-2-carboxylate, RefChem:6486, DTXCID3024021, 205-702-2

Molecular formula
C5H9NO2
Empirical formula
C5H9NO2
Molecular weight
115.13 g/mol
Exact mass
115.06333
CAS number
147-85-3
PubChem CID
145742
Canonical SMILES
C1CC(NC1)C(=O)O
Isomeric SMILES
C1C[C@H](NC1)C(=O)O
InChI
InChI=1S/C5H9NO2/c7-5(8)4-2-1-3-6-4/h4,6H,1-3H2,(H,7,8)/t4-/m0/s1
InChIKey
ONIBWKKTOPOVIA-BYPYZUCNSA-N
Molfile

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

Physical properties

TemperaturePressureDensity
Appearance
White crystals or crystalline powder[2]
2 values

From Hazardous Substances Data Bank (HSDB), the most authoritative source here.

ValueAs writtenSource
–Dry Powder[1] EPA Chemical Data Reporting (CDR)
–shownWhite crystals or crystalline powder[2] Hazardous Substances Data Bank (HSDB)cites Larranaga, M.D., Lewis, R.J. Sr., Lewis, R.A.; Hawley's Condensed Chemical Dictionary 16th Edition. John Wiley & Sons, Inc. Hoboken, NJ 2016., p. 1135
Odor
Odorless[2]
Melting point
MP: 215-220 °C with decomposition (D(+)-Proline)[2]
2 values

Only one source reports it.

ValueAs writtenSource
215 to 220 °CshownMP: 215-220 °C with decomposition /D(+)-Proline/[2] Hazardous Substances Data Bank (HSDB)cites Larranaga, M.D., Lewis, R.J. Sr., Lewis, R.A.; Hawley's Condensed Chemical Dictionary 16th Edition. John Wiley & Sons, Inc. Hoboken, NJ 2016., p. 1135
205 °CMP: 205 °C with decomposition /DL-Proline/[2] Hazardous Substances Data Bank (HSDB)cites Larranaga, M.D., Lewis, R.J. Sr., Lewis, R.A.; Hawley's Condensed Chemical Dictionary 16th Edition. John Wiley & Sons, Inc. Hoboken, NJ 2016., p. 1135
Density
1.064 at 24 °C[2]
Solubility in water
Very soluble in water, alcohol; insoluble in ether[2]
log P
log Kow = -2.54[2]

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
8
Rings
1
Aromatic rings
0
Fraction sp³ carbons (Fsp3)
0.8
H-bond donors
2
H-bond acceptors
2 computed here · PubChem 3
Rotatable bonds
1
TPSA (Ų)
49.3
Formal charge
0
XLogP3
-2.5 PubChem
Complexity
103 PubChem
Stereocenters
1 definedCIP: C4: 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

  • C52.16%
  • H7.88%
  • N12.17%
  • O27.79%

Isotope pattern

100%115.0636.0%116.066117.068

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
-0.18 Crippen (Wildman and Crippen 1999)
log S (water solubility)
-0.38 ESOL (Delaney 2004), log mol/L
Synthetic accessibility
2.74 SA score, 1 easy to 10 hard (Ertl and Schuffenhauer 2009)

Drug-likeness: Lipinski’s rule of five

  • Molecular weight ≤ 500: 115.13
  • log P ≤ 5 (Crippen): -0.18
  • 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 99.1% (419 of 423) of all reports.[3]

Storage

  • Keep container tightly closed in a dry and well-ventilated place. Storage class (TRGS 510): Non Combustible Solids.[2]

Incompatibilities

  • Incompatible materials: Strong oxidizing agents[2]

Safety data sheets on the supplier’s page: AiFChem, an XtalPi Company, ChemoSapiens, Shenghe Chemical.

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. [1]EPA Chemical Data Reporting (CDR) · Public domain (US EPA) · via PubChem · retrieved 2026-10-14
  2. [2]Hazardous Substances Data Bank (HSDB) · Public domain (US NLM) · via PubChem · retrieved 2026-10-14
  3. [3]European Chemicals Agency (ECHA) · ECHA legal notice: reuse with acknowledgement · via PubChem · retrieved 2026-10-14
  4. [4]Human Metabolome Database (HMDB) · Linked only · via PubChem · retrieved 2026-10-14
  5. [5]SpectraBase · Linked only · via PubChem · retrieved 2026-10-14
  6. [6]MassBank Europe · Linked only · via PubChem · retrieved 2026-10-14
  7. [7]MassBank of North America (MoNA) · CC BY 4.0 · via PubChem · retrieved 2026-10-14
  8. [8]NIST Mass Spectrometry Data Center · Linked only · via PubChem · retrieved 2026-10-14
  9. ·Calculated values: computed by Athanor with RDKit 2026.09 from the structure.
  10. ·Literature on PubChem

Data last updated 2026-10-14.