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Pyrrole

Athanor · official

C4H5N · 67.09 g/mol

IUPAC name: 1H-pyrrole

Also called azole, imidole, divinylenimine

Rings
Open in Athanor
The structure of Pyrrole
Drawn from its SMILES with RDKit220
FlammableHarmful or irritantWarningFlammable liquid and vapor · Harmful if swallowed

Names and identifiers

IUPAC name
1H-pyrrole
Synonyms
azole, imidole, divinylenimine
+ 37 more

1H-Pyrrole, Azole, Divinylenimine, Imidole, Pyrrol, Monopyrrole, Divinyleneimine, 1-Aza-2,4-cyclopentadiene, FEMA No. 3386, Pyrroles, DTXSID5021910, NSC-62777, 86S1ZD6L2C, CHEBI:19203, DTXCID201910, Pyrrole 1539, RefChem:6188, CHEBI:26455, CHEBI:35556, 203-724-7, Pyrrole-15N, NSC 62777, (1H-Pyrrole)x, PYROLLE, MFCD00005216, pyrrole-, Polypyrrole pound PPy pound(c), Polypyrrole (undoped, extent of labeling: ~20 wt. % loading, composite with carbon black), CCRIS 2933, HSDB 119, EINECS 203-724-7, UNII-86S1ZD6L2C, Pyrrhol, Pyrole, beta-pyrrole, a pyrrole, AI3-18817

Molecular formula
C4H5N
Empirical formula
C4H5N
Molecular weight
67.09 g/mol
Exact mass
67.04220
CAS number
109-97-7
PubChem CID
8027
Canonical SMILES
C1=CNC=C1
Isomeric SMILES
C1=CNC=C1
InChI
InChI=1S/C4H5N/c1-2-4-5-3-1/h1-5H
InChIKey
KAESVJOAVNADME-UHFFFAOYSA-N
Molfile

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

Physical properties

TemperaturePressureDensity
Appearance
Yellowish or brown oil[1]
Odor
Agreeable empyreumatic odor resembling that of chloroform[1]
Melting point
-23.4 °C[2]
Boiling point
129.7 °C @760 [mmHg][2]
Density
0.9698 @ 20°C[2]
Solubility in water
Water solubility: 4.5 × 10⁴ mg/l @ 25 °C[1]
2 values

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

ValueAs writtenSource
–Soluble in alcohol, ether and dilute acids. Also soluble in most organic chemicals.[1] Hazardous Substances Data Bank (HSDB)cites Lewis, R.J., Sr (Ed.). Hawley's Condensed Chemical Dictionary. 12th ed. New York, NY: Van Nostrand Rheinhold Co., 1993, p. 984
–shownWater solubility: 4.5X10+4 mg/l @ 25 °C[1] Hazardous Substances Data Bank (HSDB)cites Riddick, J.A., W.B. Bunger, Sakano T.K. Techniques of Chemistry 4th ed., Volume II. Organic Solvents. New York, NY: John Wiley and Sons., 1985., p. 631
log P
log Kow = 0.75[1]
pKa
pKa= 17.5[1]
2 values

Only one source reports it.

ValueAs writtenSource
–shownpKa= 17.5[1] Hazardous Substances Data Bank (HSDB)cites Gerhartz, W. (exec ed.). Ullmann's Encyclopedia of Industrial Chemistry. 5th ed.Vol A1: Deerfield Beach, FL: VCH Publishers, 1985 to Present., p. A22 (93) 453
–pKa = -3.80 (protonated form) (conjugate acid)[1] Hazardous Substances Data Bank (HSDB)cites Perrin DD; Dissociation constants of organic bases in aqueous solution. IUPAC Chem Data Ser, Buttersworth, London (1965)
Vapor pressure
8.35 [mmHg] @25 °C[2]
Flash point
39 °C (102 °F) (CLOSED CUP)[1]
Viscosity
4.1123 × 10⁻³ Pa.s @ 249.74K[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
5
Rings
1
Aromatic rings
1
Fraction sp³ carbons (Fsp3)
0
H-bond donors
1
H-bond acceptors
0
Rotatable bonds
0
TPSA (Ų)
15.8
Formal charge
0
XLogP3
0.7 PubChem
Complexity
22 PubChem
Stereocenters
None
Double-bond geometry
None specified
Point group
C2v of one 3D conformer with its hydrogens, by Athanor’s engine (as in the app)

Elemental analysis

  • C71.61%
  • H7.51%
  • N20.88%

Isotope pattern

100%67.0424.8%68.045

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
1.01 Crippen (Wildman and Crippen 1999)
log S (water solubility)
-1.64 ESOL (Delaney 2004), log mol/L
Synthetic accessibility
3.43 SA score, 1 easy to 10 hard (Ertl and Schuffenhauer 2009)

Drug-likeness: Lipinski’s rule of five

  • Molecular weight ≤ 500: 67.09
  • log P ≤ 5 (Crippen): 1.01
  • H-bond donors ≤ 5: 1
  • H-bond acceptors ≤ 10: 0

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: 1,442 company reports to ECHA. Source [3].

  • Flammable
  • Harmful or irritant
220
NFPA 704[1]
  • H226Flammable liquid and vapor (10.7% of reports)
  • H302Harmful if swallowed (89.3% of reports)

Precautionary statements: P210, P233, P240, P241, P242, P243, P264, P270, P280, P301+P317, P303+P361+P353, P330, P370+P378, P403+P235, P501

Incompatibilities

  • ... CAN react WITH oxidizing materials.[1]
  • Violent reaction with 2-nitrobenzaldehyde.[1]

Safety data sheets on the supplier’s page: Hunan Chemfish Pharmaceutical Co., Ltd., SynQuest Laboratories, Smolecule.

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]PAC Chemical Database, U.S. Department of Energy · Public domain (US DOE) · 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]NMRShiftDB · Linked only · via PubChem · retrieved 2026-10-14
  5. [5]Human Metabolome Database (HMDB) · Linked only · via PubChem · retrieved 2026-10-14
  6. [6]SpectraBase · Linked only · via PubChem · retrieved 2026-10-14
  7. [7]NIST Mass Spectrometry Data Center · Linked only · via PubChem · retrieved 2026-10-14
  8. [8]MassBank Europe · Linked only · via PubChem · retrieved 2026-10-14
  9. [9]MassBank of North America (MoNA) · CC BY 4.0 · via PubChem · retrieved 2026-10-14
  10. ·Calculated values: computed by Athanor with RDKit 2026.09 from the structure.
  11. ·Literature on PubChem

Data last updated 2026-10-14.