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Histidine

Athanor · official

C6H9N3O2 · 155.15 g/mol

IUPAC name: (2S)-2-amino-3-(1H-imidazol-5-yl)propanoic acid

Also called L-histidine

Amino acids
Open in Athanor
The structure of Histidine
Drawn from its SMILES with RDKit
Harmful or irritantWarningHarmful if swallowed · Causes skin irritation · Causes serious eye irritation · Harmful if inhaled

Names and identifiers

IUPAC name
(2S)-2-amino-3-(1H-imidazol-5-yl)propanoic acid
Synonyms
L-histidine, glyoxaline-5-alanine, L-(-)-Histidine
+ 35 more

histidina, Istidina, HISTIDINE, L-, L-Histidin, (2S)-2-amino-3-(1H-imidazol-4-yl)propanoic acid, (S)-4-(2-Amino-2-carboxyethyl)imidazole, FEMA No. 3694, L-His, (S)-alpha-amino-1H-imidazole-4-propanoic acid, Histidinum, 4-(2-Amino-2-carboxyethyl)imidazole, (S)-2-Amino-3-(4-imidazolyl)propionsaeure, (S)-alpha-Amino-1H-imidazole-4-propionic acid, (S)-a-Amino-1H-imidazole-4-propanoic acid, alpha-Amino-4(or 5)-imidazolepropionic acid, DTXSID9023126, (2S)-2-amino-3-(1H-imidazol-5-yl)propanoic acid, 1H-Imidazole-4-propanoic acid, alpha-amino-, (S)-, 4QD397987E, NSC-137773, CHEBI:15971, (2S)-2-amino-3-(imidazol-4-yl)propanoic acid, (S)-2-amino-3-(1H-imidazol-4-yl)propanoic acid, L-isomer Histidine, CHEBI:27570, NSC137773, (2S)-2-azaniumyl-3-(1H-imidazol-5-yl)propanoate, Histidine, L, L-Histidine High, Trepoxicam-7.5, alpha-Amino-1H-imidazole-4-propionic acid, L-Histidine 7409, RefChem:6442, L-Histidine High 7410, MELOXICAM, HISTIDINE

Molecular formula
C6H9N3O2
Empirical formula
C6H9N3O2
Molecular weight
155.15 g/mol
Exact mass
155.06948
CAS number
71-00-1
PubChem CID
6274
Canonical SMILES
C1=C(NC=N1)CC(C(=O)O)N
Isomeric SMILES
C1=C(NC=N1)C[C@@H](C(=O)O)N
InChI
InChI=1S/C6H9N3O2/c7-5(6(10)11)1-4-2-8-3-9-4/h2-3,5H,1,7H2,(H,8,9)(H,10,11)/t5-/m0/s1
InChIKey
HNDVDQJCIGZPNO-YFKPBYRVSA-N
Molfile

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

Physical properties

Appearance
COLORLESS[1]
Solubility in water
In water, 4.56 × 10⁴ mg/l @ 25 °C[1]
log P
log Kow= -3.32[1]
pKa
pKa = 2.76 @ 0 °C[1]

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
11
Rings
1
Aromatic rings
1
Fraction sp³ carbons (Fsp3)
0.33
H-bond donors
3
H-bond acceptors
3 computed here · PubChem 4
Rotatable bonds
3
TPSA (Ų)
92
Formal charge
0
XLogP3
-3.2 PubChem
Complexity
151 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

  • C46.45%
  • H5.85%
  • N27.08%
  • O20.62%

Isotope pattern

100%155.0707.8%156.072157.074

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)
-0.54 ESOL (Delaney 2004), log mol/L
Synthetic accessibility
3.19 SA score, 1 easy to 10 hard (Ertl and Schuffenhauer 2009)

Drug-likeness: Lipinski’s rule of five

  • Molecular weight ≤ 500: 155.16
  • log P ≤ 5 (Crippen): -0.64
  • H-bond donors ≤ 5: 3
  • H-bond acceptors ≤ 10: 3

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: 320 company reports to ECHA. Source [2].

  • Harmful or irritant
  • H302Harmful if swallowed (25.3% of reports)
  • H315Causes skin irritation (25.9% of reports)
  • H319Causes serious eye irritation (25.9% of reports)
  • H332Harmful if inhaled (25.3% of reports)

Precautionary statements: P261, P264, P264+P265, P270, P271, P280, P301+P317, P302+P352, P304+P340, P305+P351+P338, P317, P321, P330, P332+P317, P337+P317, P362+P364, P501

View all classifications (2)
  • [2] European Chemicals Agency (ECHA)This chemical does not meet GHS hazard criteria for 74.1% (237 of 320) of all reports.
  • [2] European Chemicals Agency (ECHA) · 320 reports · WarningH302, H315, H319, H332

Safety data sheets on the supplier’s page: AbaChemScene, 001Chemical, Alfa Chemistry.

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]Hazardous Substances Data Bank (HSDB) · Public domain (US NLM) · via PubChem · retrieved 2026-10-14
  2. [2]European Chemicals Agency (ECHA) · ECHA legal notice: reuse with acknowledgement · via PubChem · retrieved 2026-10-14
  3. [3]NMRShiftDB · Linked only · 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.