Imidazole
Athanor · official
C3H4N2 · 68.08 g/mol
IUPAC name: 1H-imidazole
Also called 1,3-diazole, glyoxaline, histidine ring
DangerHarmful if swallowed · Causes severe skin burns and eye damage · May damage the unborn childNames and identifiers
- IUPAC name
- 1H-imidazole
- Synonyms
- 1,3-diazole, glyoxaline, histidine ring
+ 37 more
1H-Imidazole, Glyoxaline, Imidazol, Iminazole, Miazole, 1,3-Diazole, Imutex, Glyoxalin, 1,3-Diaza-2,4-cyclopentadiene, Pyrro(b)monazole, Glioksal, Formamidine, N,N'-vinylene-, Pyrro[b]monazole, Methanimidamide, N,N'-1,2-ethenediyl-, DTXSID2029616, N,N'-vinyleneformamidine, 7GBN705NH1, N,N'-1,2-ethenediylmethanimidamide, NSC-60522, DTXCID809616, CHEBI:16069, RefChem:5902, CHEBI:14434, 206-019-2, USAF EK-4733, Glioksal [Polish], IMD, CCRIS 3345, AI3-24703, NSC 60522, BRN 0103853, MFCD00005183, CHEMBL540, imidazole-, CAS-288-32-4, Imidazole (8CI), NSC51860
- Molecular formula
- C3H4N2
- Empirical formula
- C3H4N2
- Molecular weight
- 68.08 g/mol
- Exact mass
- 68.03745
- CAS number
- 288-32-4
- PubChem CID
- 795
- Canonical SMILES
- C1=CN=CN1
- Isomeric SMILES
- C1=CN=CN1
- InChI
- InChI=1S/C3H4N2/c1-2-5-3-4-1/h1-3H,(H,4,5)
- InChIKey
- RAXXELZNTBOGNW-UHFFFAOYSA-N
- Molfile
Names, InChI and the identifiers from PubChem, retrieved 2026-10-14.
Physical properties
- Appearance
- Colorless crystals[3]
4 values
From Hazardous Substances Data Bank (HSDB), the most authoritative source here.
Value As written Source – Liquid; Other Solid [1] EPA Chemical Data Reporting (CDR) – COLOURLESS-TO-YELLOW CRYSTALS WITH CHARACTERISTIC ODOUR. [2] ILO-WHO International Chemical Safety Cards (ICSCs) –shown Colorless crystals [3] 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. 752 – Colorless-yellow solid [3] Hazardous Substances Data Bank (HSDB)cites OECD; Screening Information Data Set (SIDS) Initial Assessment Report for SIDS Initial Assessment Meeting (SIAM) 17 Imidazole (CAS number 288-32-4) (2003). Available from, as of July 30, 2018: https://www.inchem.org/pages/sids.html - Odor
- Amine-like odor[3]
- Melting point
- 89 °C[2]
- Boiling point
- 268 °C[2]
2 values
Sources disagree; from ILO-WHO International Chemical Safety Cards (ICSCs), the most authoritative.
Value As written Source 268 °Cshown 268 °C [2] ILO-WHO International Chemical Safety Cards (ICSCs) 257 °C 257 °C @760 [mm Hg] [4] PAC Chemical Database, U.S. Department of Energy - Density
- 1.0303 @ 101°C[4]
2 values
2 of 2 sources agree on it (most common value).
Value As written Source – Relative density (water = 1): 1.03 [2] ILO-WHO International Chemical Safety Cards (ICSCs) –shown 1.0303 @ 101°C [4] PAC Chemical Database, U.S. Department of Energy - Solubility in water
- Solubility in water, g/100ml at 20 °C: 63.3 (good)[2]
3 values
From ILO-WHO International Chemical Safety Cards (ICSCs), the most authoritative source here.
Value As written Source – In water, 241 g/100 g at 20 °C [3] Hazardous Substances Data Bank (HSDB)cites Ebel K et al; Imidazole and Derivatives. Ullmann's Encyclopedia of Industrial Chemistry. 7th ed. (1999-2018). New York, NY: John Wiley & Sons. Online Posting Date: 15 June 2000. – In water, 663 g/L at 20 °C [3] Hazardous Substances Data Bank (HSDB)cites OECD; Screening Information Data Set (SIDS) Initial Assessment Report for SIDS Initial Assessment Meeting (SIAM) 17 Imidazole (CAS number 288-32-4) (2003). Available from, as of July 30, 2018: https://www.inchem.org/pages/sids.html –shown Solubility in water, g/100ml at 20 °C: 63.3 (good) [2] ILO-WHO International Chemical Safety Cards (ICSCs) - log P
- -0.02[2]
2 values
Sources disagree; from ILO-WHO International Chemical Safety Cards (ICSCs), the most authoritative.
Value As written Source – log Kow = -0.08 [3] Hazardous Substances Data Bank (HSDB)cites Hansch, C., Leo, A., D. Hoekman. Exploring QSAR - Hydrophobic, Electronic, and Steric Constants. Washington, DC: American Chemical Society., 1995., p. 5 –shown -0.02 [2] ILO-WHO International Chemical Safety Cards (ICSCs) - pKa
- Reported, but no value passed the checks.
The 2 values and why
- Imidazole is a moderately strong base pKb = 7.0, and a weak acid pKa = 14.9 (could not be read; source [3])
- Imidazole is a heterocyclic compound containing two nitrogen atoms with pKa = 7.0 and pKa = 14.9 (could not be read; source [3])
- Vapor pressure
- Vapor pressure = 0.327 Pa at 25 °C (2.25 × 10⁻² mmHg at 25 °C)[3]
2 values
Sources disagree; from Hazardous Substances Data Bank (HSDB), the most authoritative.
Value As written Source 0.00245 mmHgshown Vapor pressure = 0.327 Pa at 25 °C (2.25X10-2 mm Hg at 25 °C) [3] Hazardous Substances Data Bank (HSDB)cites ECHA; Search for Chemicals. Imidazole (CAS No 288-32-4) Registered Substances Dossier. European Chemical Agency. Available from, as of July 30, 2018: https://echa.europa.eu/ 0.0023 mmHg Vapor pressure, Pa at 20 °C: 0.3 [2] ILO-WHO International Chemical Safety Cards (ICSCs) - Flash point
- 145 °C c.c.[2]
2 values
2 of 2 sources agree on it (most common value).
Value As written Source 145 °C 145 °C (293 °F) - closed cup [3] Hazardous Substances Data Bank (HSDB)cites Sigma-Aldrich; Safety Data Sheet for Imidazole. Product Number: I5513, Version 4.14 (Revision Date 01/25/2018). Available from, as of July 30, 2018: https://www.sigmaaldrich.com/safety-center.html 145 °Cshown 145 °C c.c. [2] ILO-WHO International Chemical Safety Cards (ICSCs) - Autoignition temperature
- 480 °C[2]
2 values
2 of 2 sources agree on it (most common value).
Value As written Source 480 °C 480 °C [3] Hazardous Substances Data Bank (HSDB)cites International Program on Chemical Safety/European Commission; International Chemical Safety Card (ICSC) on Imizadole (288-32-4), ICSC No. 1721 (November 2008). Available from, as of July 30, 2018: https://www.inchem.org/documents/icsc/icsc/eics1721.htm 480 °Cshown 480 °C [2] ILO-WHO International Chemical Safety Cards (ICSCs) - Viscosity
- Reported, but no value passed the checks.
The value and why
- 2.617 mm²/s at 100 °C (could not be read; source [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
- 5
- Rings
- 1
- Aromatic rings
- 1
- Fraction sp³ carbons (Fsp3)
- 0
- H-bond donors
- 1
- H-bond acceptors
- 1
- Rotatable bonds
- 0
- TPSA (Ų)
- 28.7
- Formal charge
- 0
- XLogP3
- -0.1 PubChem
- Complexity
- 28 PubChem
- Stereocenters
- None
- Double-bond geometry
- None specified
- Point group
- Cs of one 3D conformer with its hydrogens, by Athanor’s engine (as in the app)
Elemental analysis
- C52.93%
- H5.92%
- N41.15%
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
- 0.41 Crippen (Wildman and Crippen 1999)
- log S (water solubility)
- -1.26 ESOL (Delaney 2004), log mol/L
- Synthetic accessibility
- 3.45 SA score, 1 easy to 10 hard (Ertl and Schuffenhauer 2009)
Drug-likeness: Lipinski’s rule of five
- Molecular weight ≤ 500: 68.08
- log P ≤ 5 (Crippen): 0.41
- H-bond donors ≤ 5: 1
- H-bond acceptors ≤ 10: 1
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
Danger
Harmonized EU classification (CLP Annex VI). Source [5].
- Corrosive
- Harmful or irritant
- Health hazard
- H302Harmful if swallowed
- H314Causes severe skin burns and eye damage
- H360DMay damage the unborn child
Precautionary statements: P203, P260, P264, P270, P280, P301+P317, P301+P330+P331, P302+P361+P354, P304+P340, P305+P354+P338, P316, P318, P321, P330, P363, P405, P501
View all classifications (4)
- [5] Regulation (EC) No 1272/2008 of the European Parliament and of the Council · DangerH302, H314, H360D
- [6] European Chemicals Agency (ECHA)This chemical does not meet GHS hazard criteria for 0.2% (2 of 945) of reports.
- [6] European Chemicals Agency (ECHA) · 945 reports · DangerH302, H314, H318, H360, H360D, H361
- [3] Hazardous Substances Data Bank (HSDB) · DangerH302, H314, H318, H360
First aid
- Fresh air, rest. Refer for medical attention.[2]
- Remove contaminated clothes. Rinse skin with plenty of water or shower. Refer immediately for medical attention.[2]
- Rinse with plenty of water (remove contact lenses if easily possible). Refer immediately for medical attention.[2]
- Rinse mouth. Rest. Do NOT induce vomiting. Give one or two glasses of water to drink. Refer immediately for medical attention.[2]
Storage
Incompatibilities
Safety data sheets on the supplier’s page: Alfa Chemistry, Hairui Chemical, INTERBIOSCREEN.
Always read the supplier’s safety data sheet before working with it.
Spectra
- NMRNMRShiftDB
- 1H NMRHuman Metabolome Database (HMDB) (500 MHz · Methanol) · Human Metabolome Database (HMDB) (Varian · 500 MHz · Water) · SpectraBase
- 13C NMRSpectraBase
- 15N NMRSpectraBase
- 1H-1H NMRHuman Metabolome Database (HMDB)
- 1H-13C NMRHuman Metabolome Database (HMDB) (Bruker · 400 MHz · Water)
- GC-MSHuman Metabolome Database (HMDB) (EI-B · positive) · MassBank of North America (MoNA) (HITACHI M-80 · EI-B · positive) · MassBank of North America (MoNA) (HITACHI M-80 · EI-B · positive) · NIST Mass Spectrometry Data Center · NIST Mass Spectrometry Data Center · NIST Mass Spectrometry Data Center
- MS-MSHuman Metabolome Database (HMDB) (Quattro_QQQ · Positive) · Human Metabolome Database (HMDB) (LC-ESI-QQ · positive) · Human Metabolome Database (HMDB) (LC-ESI-QQ · positive) · Human Metabolome Database (HMDB) (Positive) · Human Metabolome Database (HMDB) (Quattro_QQQ · Positive) · Human Metabolome Database (HMDB) (Quattro_QQQ · Positive)
- LC-MSMassBank Europe (Q Exactive Plus Orbitrap Thermo Scientific · LC-ESI-QFT · POSITIVE) · MassBank Europe (API3000, Applied Biosystems · LC-ESI-QQ · POSITIVE) · MassBank Europe (API3000, Applied Biosystems · LC-ESI-QQ · POSITIVE) · MassBank Europe (API3000, Applied Biosystems · LC-ESI-QQ · POSITIVE) · MassBank Europe (API3000, Applied Biosystems · LC-ESI-QQ · POSITIVE) · MassBank Europe (API3000, Applied Biosystems · LC-ESI-QQ · POSITIVE)
- Other MSMassBank Europe (ESI-QTOF · POSITIVE · ESI) · MassBank Europe (ESI-QTOF · POSITIVE · ESI) · MassBank Europe (ESI-QTOF · NEGATIVE · ESI) · MassBank Europe (ESI-QTOF · POSITIVE · ESI) · MassBank Europe (ESI-QTOF · NEGATIVE · ESI) · MassBank Europe (HITACHI M-80 · EI-B · POSITIVE)
- UV-VISSpectraBase
- FTIRSpectraBase (KBr WAFER)
- ATR-IRSpectraBase (Bio-Rad FTS · ATR-Neat (DuraSamplIR II))
- Vapor Phase IRSpectraBase (DIGILAB FTS-14 · Vapor Phase)
- RamanSpectraBase (FT-Raman)
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]ILO-WHO International Chemical Safety Cards (ICSCs) · CC BY 4.0 · via PubChem · retrieved 2026-10-14
- [3]Hazardous Substances Data Bank (HSDB) · Public domain (US NLM) · via PubChem · retrieved 2026-10-14
- [4]PAC Chemical Database, U.S. Department of Energy · Public domain (US DOE) · via PubChem · retrieved 2026-10-14
- [5]Regulation (EC) No 1272/2008 of the European Parliament and of the Council · EU reuse policy, CC BY 4.0 · via PubChem · retrieved 2026-10-14
- [6]European Chemicals Agency (ECHA) · ECHA legal notice: reuse with acknowledgement · via PubChem · retrieved 2026-10-14
- [7]NMRShiftDB · Linked only · via PubChem · retrieved 2026-10-14
- [8]Human Metabolome Database (HMDB) · Linked only · via PubChem · retrieved 2026-10-14
- [9]SpectraBase · Linked only · via PubChem · retrieved 2026-10-14
- [10]MassBank of North America (MoNA) · CC BY 4.0 · via PubChem · retrieved 2026-10-14
- [11]NIST Mass Spectrometry Data Center · Linked only · via PubChem · retrieved 2026-10-14
- [12]MassBank Europe · 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.