Furan

Athanor · official

C₄H₄O · 68.07 g/mol

Also called oxole, furfuran, divinylene oxide

Rings

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Drawn from its SMILES with RDKit

DangerExtremely flammable liquid and vapor · Harmful if swallowed · Causes skin irritation · Harmful if inhaled · Suspected of causing genetic defects · May cause cancer · Harmful to aquatic life with long lasting effects

Names and identifiers

IUPAC name: furan
Synonyms: oxole, furfuran, divinylene oxide
+ 37 more
Divinylene oxide, Tetrole, Furfuran, Oxacyclopentadiene, Oxole, Furane, 1,4-Epoxy-1,3-butadiene, Axole, NCI-C56202, DTXSID6020646, UC0XV6A8N9, DTXCID20646, CHEBI:35559, Oxycyclopentadiene, RefChem:5845, 203-727-3, RCRA waste number U124, Furfurane, tetrole oxide, Furan (98%), MFCD00003222, Furan (stabilized with BHT), HSDB 89, CCRIS 3159, EINECS 203-727-3, UN2389, RCRA waste no. U124, UNII-UC0XV6A8N9, BRN 0103221, beta-furan, Oxol, AI3-24244, furan-, 2-Furan, Furan, 98%, FURAN [HSDB], FURAN [IARC]
Molecular formula: C₄H₄O
Empirical formula: C₄H₄O
Molecular weight: 68.07 g/mol
Exact mass: 68.02621
CAS number: 110-00-9
PubChem CID: 8029
Canonical SMILES: C1=COC=C1
Isomeric SMILES: C1=COC=C1
InChI: InChI=1S/C4H4O/c1-2-4-5-3-1/h1-4H
InChIKey: YLQBMQCUIZJEEH-UHFFFAOYSA-N
Molfile

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

Physical properties

TemperaturePressureDensity

Appearance: Colorless liquid, turns brown upon standing; color change is retarded if a small amount of water is added[4]
4 values
From Hazardous Substances Data Bank (HSDB), the most authoritative source here.
Value As written Source
– Furan appears as a clear colorless liquid with a strong odor. Flash point below 32 °F. Less dense than water and insoluble in water. Vapors heavier than air. [1] CAMEO Chemicals
– Liquid [2] EPA Chemical Data Reporting (CDR)
– CLEAR COLOURLESS LIQUID WITH CHARACTERISTIC ODOUR. TURNS BROWN ON STANDING. [3] ILO-WHO International Chemical Safety Cards (ICSCs)
–shown Colorless liquid, turns brown upon standing; color change is retarded if a small amount of water is added [4] Hazardous Substances Data Bank (HSDB)cites Lewis, R.J. Sr.; Hawley's Condensed Chemical Dictionary 15th Edition. John Wiley & Sons, Inc. New York, NY 2007., p. 587
Odor: Ethereal[4]
Melting point: -85.61 °C[5]
3 values
3 of 3 sources agree on it (most common value).
Value As written Source
−86 °C -123 °F (EPA, 1998) [1] CAMEO Chemicalscites U.S. Environmental Protection Agency. 1998. Extremely Hazardous Substances (EHS) Chemical Profiles and Emergency First Aid Guides. Washington, D.C.: U.S. Government Printing Office.
−85.6 °C -85.6 °C [3] ILO-WHO International Chemical Safety Cards (ICSCs)
−85.6 °Cshown -85.61 °C [5] PAC Chemical Database, U.S. Department of Energy
Boiling point: 31.3 °C[3]
3 values
3 of 3 sources agree on it (most common value).
Value As written Source
32 °C 90 °F at 758 mmHg (EPA, 1998) [1] CAMEO Chemicalscites U.S. Environmental Protection Agency. 1998. Extremely Hazardous Substances (EHS) Chemical Profiles and Emergency First Aid Guides. Washington, D.C.: U.S. Government Printing Office.
31.3 °Cshown 31.3 °C [3] ILO-WHO International Chemical Safety Cards (ICSCs)
31.5 °C 31.5 °C @760 [mm Hg] [5] PAC Chemical Database, U.S. Department of Energy
Density: 0.9514 @ 20°C[5]
3 values
3 of 3 sources agree on it (most common value).
Value As written Source
– 0.9371 at 66.92 °F (EPA, 1998) - Less dense than water [1] CAMEO Chemicalscites U.S. Environmental Protection Agency. 1998. Extremely Hazardous Substances (EHS) Chemical Profiles and Emergency First Aid Guides. Washington, D.C.: U.S. Government Printing Office.
– Relative density (water = 1): 0.94 [3] ILO-WHO International Chemical Safety Cards (ICSCs)
–shown 0.9514 @ 20°C [5] PAC Chemical Database, U.S. Department of Energy
Solubility in water: Solubility in water, g/l at 25 °C: 10[3]
4 values
From ILO-WHO International Chemical Safety Cards (ICSCs), the most authoritative source here.
Value As written Source
– less than 1 mg/mL at 72 °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.
– Soluble in alcohol and ether [4] Hazardous Substances Data Bank (HSDB)cites Lewis, R.J. Sr.; Hawley's Condensed Chemical Dictionary 15th Edition. John Wiley & Sons, Inc. New York, NY 2007., p. 587
– In water, 1X10+4 mg/L at 25 °C [4] Hazardous Substances Data Bank (HSDB)cites PMID:7241352 Valvani SC et al; J Pharm Sci 70: 502-7 (1981)
–shown Solubility in water, g/l at 25 °C: 10 [3] ILO-WHO International Chemical Safety Cards (ICSCs)
log P: 1.34[3]
2 values
2 of 2 sources agree on it (most common value).
Value As written Source
– log Kow = 1.34 [4] 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. 8
–shown 1.34 [3] ILO-WHO International Chemical Safety Cards (ICSCs)
Vapor pressure: 493 mmHg at 20 °C (68 °F, NTP 1992)[1]
4 values
2 of 4 sources agree on it (most common value).
Value As written Source
493 mmHgshown 493 mmHg at 68 °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.
600 mmHg 600 mm Hg at 25 °C /from experimentally derived coefficients/ [4] Hazardous Substances Data Bank (HSDB)cites Daubert, T.E., R.P. Danner. Physical and Thermodynamic Properties of Pure Chemicals Data Compilation. Washington, D.C.: Taylor and Francis, 1989.
490 mmHg Vapor pressure, kPa at 20 °C: 65.8 [3] ILO-WHO International Chemical Safety Cards (ICSCs)
750 mmHg 750 [mm Hg] @31 °C [5] PAC Chemical Database, U.S. Department of Energy
Flash point: -35 °C[3]
Autoignition temperature: 390 °C[3]
Viscosity: 0.38 cP at 20 °C[4]
Refractive index: Index of refraction: 1.4214 at 20 °C/D[4]

Value	As written	Source
–	Furan appears as a clear colorless liquid with a strong odor. Flash point below 32 °F. Less dense than water and insoluble in water. Vapors heavier than air.	[1] CAMEO Chemicals
–	Liquid	[2] EPA Chemical Data Reporting (CDR)
–	CLEAR COLOURLESS LIQUID WITH CHARACTERISTIC ODOUR. TURNS BROWN ON STANDING.	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
–shown	Colorless liquid, turns brown upon standing; color change is retarded if a small amount of water is added	[4] Hazardous Substances Data Bank (HSDB)cites Lewis, R.J. Sr.; Hawley's Condensed Chemical Dictionary 15th Edition. John Wiley & Sons, Inc. New York, NY 2007., p. 587

Value	As written	Source
−86 °C	-123 °F (EPA, 1998)	[1] CAMEO Chemicalscites U.S. Environmental Protection Agency. 1998. Extremely Hazardous Substances (EHS) Chemical Profiles and Emergency First Aid Guides. Washington, D.C.: U.S. Government Printing Office.
−85.6 °C	-85.6 °C	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
−85.6 °Cshown	-85.61 °C	[5] PAC Chemical Database, U.S. Department of Energy

Value	As written	Source
32 °C	90 °F at 758 mmHg (EPA, 1998)	[1] CAMEO Chemicalscites U.S. Environmental Protection Agency. 1998. Extremely Hazardous Substances (EHS) Chemical Profiles and Emergency First Aid Guides. Washington, D.C.: U.S. Government Printing Office.
31.3 °Cshown	31.3 °C	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
31.5 °C	31.5 °C @760 [mm Hg]	[5] PAC Chemical Database, U.S. Department of Energy

Value	As written	Source
–	0.9371 at 66.92 °F (EPA, 1998) - Less dense than water	[1] CAMEO Chemicalscites U.S. Environmental Protection Agency. 1998. Extremely Hazardous Substances (EHS) Chemical Profiles and Emergency First Aid Guides. Washington, D.C.: U.S. Government Printing Office.
–	Relative density (water = 1): 0.94	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
–shown	0.9514 @ 20°C	[5] PAC Chemical Database, U.S. Department of Energy

Value	As written	Source
–	less than 1 mg/mL at 72 °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.
–	Soluble in alcohol and ether	[4] Hazardous Substances Data Bank (HSDB)cites Lewis, R.J. Sr.; Hawley's Condensed Chemical Dictionary 15th Edition. John Wiley & Sons, Inc. New York, NY 2007., p. 587
–	In water, 1X10+4 mg/L at 25 °C	[4] Hazardous Substances Data Bank (HSDB)cites PMID:7241352 Valvani SC et al; J Pharm Sci 70: 502-7 (1981)
–shown	Solubility in water, g/l at 25 °C: 10	[3] ILO-WHO International Chemical Safety Cards (ICSCs)

Value	As written	Source
–	log Kow = 1.34	[4] 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. 8
–shown	1.34	[3] ILO-WHO International Chemical Safety Cards (ICSCs)

Value	As written	Source
493 mmHgshown	493 mmHg at 68 °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.
600 mmHg	600 mm Hg at 25 °C /from experimentally derived coefficients/	[4] Hazardous Substances Data Bank (HSDB)cites Daubert, T.E., R.P. Danner. Physical and Thermodynamic Properties of Pure Chemicals Data Compilation. Washington, D.C.: Taylor and Francis, 1989.
490 mmHg	Vapor pressure, kPa at 20 °C: 65.8	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
750 mmHg	750 [mm Hg] @31 °C	[5] PAC Chemical Database, U.S. Department of Energy

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: 0
H-bond acceptors: 1
Rotatable bonds: 0
TPSA (Å²): 13.1
Formal charge: 0
XLogP3: 1.3 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

C70.58%
H5.92%
O23.50%

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: 1.28 Crippen (Wildman and Crippen 1999)
log S (water solubility): -1.81 ESOL (Delaney 2004), log mol/L
Synthetic accessibility: 3.41 SA score, 1 easy to 10 hard (Ertl and Schuffenhauer 2009)

Drug-likeness: Lipinski’s rule of five

Molecular weight ≤ 500: 68.07
log P ≤ 5 (Crippen): 1.28
H-bond donors ≤ 5: 0
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 [6].

Flammable
Harmful or irritant
Health hazard

NFPA 704[4]

H224Extremely flammable liquid and vapor
H302Harmful if swallowed
H315Causes skin irritation
H332Harmful if inhaled
H341Suspected of causing genetic defects
H350May cause cancer
H412Harmful to aquatic life with long lasting effects

Precautionary statements: P203, P210, P233, P240, P241, P242, P243, P260, P261, P264, P270, P271, P273, P280, P301+P317, P302+P352, P303+P361+P353, P304+P340, P317, P318, P319, P321, P330, P332+P317, P362+P364, P370+P378, P403+P235, P405, P501

View all classifications (2)

[6] Regulation (EC) No 1272/2008 of the European Parliament and of the Council · DangerH224, H302, H315, H332, H341, H350, H412
[7] European Chemicals Agency (ECHA) · 263 reports · DangerH224, H302+H332, H302, H315, H332, H341, H350, H373, H412

Exposure limits

IDLH: 13 ppm [From IDLH Table: Furan] (NIOSH, 2024)[1]
MAK (Maximale Arbeitsplatz Konzentration): 0.056 mg/m[3]

First aid

Signs and Symptoms of Furan Exposure: Acute exposure to furan may produce dizziness, nausea, vomiting, diarrhea, and anorexia. Irritation and burning of the eyes and skin may occur. Furan vapor is a central nervous system depressant. Emergency Life-Support Procedures: Acute exposure to furan may require decontamination and life support for the victims. Emergency personnel should wear protective clothing appropriate to the type and degree of contamination. Air-purifying or supplied-air respiratory equipment should also be worn, as necessary.[1]
General First Aid: · Call 911 or emergency medical service. · Ensure that medical personnel are aware of the material(s) involved, take precautions to protect themselves and avoid contamination. · Move victim to fresh air if it can be done safely. · Administer oxygen if breathing is difficult. · If victim is not breathing: -- DO NOT perform mouth-to-mouth resuscitation; the victim may have ingested or inhaled the substance. -- If equipped and pulse detected, wash face and mouth, then give artificial respiration using a proper respiratory medical device (bag-valve mask, pocket mask equipped…[8]
Fresh air, rest. Half-upright position. Administration of oxygen may be needed. Refer immediately for medical attention.[3]
Remove contaminated clothes. Rinse skin with plenty of water or shower. Refer for medical attention .[3]

Storage

Fireproof. Well closed. Cool. Keep in the dark. Store only if stabilized. Separated from strong oxidants and acids. Provision to contain effluent from fire extinguishing. Store in an area without drain or sewer access.[3]
Before entering confined space where this chemical may be present, check to make sure that an explosive concentration does not exist. Store in an explosion-proof refrigerator. Keep in a tightly closed container under an inert atmosphere and protect from light for long-term storage. A regulated, marked area should be established where this chemical is handled, used, or stored ...[4]
Fireproof. Separated from strong oxidants, acids. Cool. Well closed. Store only if stabilized ... Closed system, ventilation, explosion-proof electrical equipment and lighting. Do NOT use compressed air for filling, discharging, or handling. Use non-sparking handtools.[4]
Precautions FOR "carcinogens": Storage site should be as close as practical to lab in which carcinogens are to be used, so that only small quantities required for ... Expt need to be carried. Carcinogens should be kept in only one section of cupboard, an explosion-proof refrigerator or freezer (depending on chemicophysical properties ...) that bears appropriate label. An inventory ... Should be kept, showing quantity of carcinogen & date it was acquired ... Facilities for dispensing ... Should be contiguous to storage area. (chemical Carcinogens)[4]

Incompatibilities

Violent reaction with acids, oxidizers. Unless stablized with an inhibitor, air exposure forms unstable peroxides.[4]
Contact with acids can initiate a violent exothermic reaction.[4]

Safety data sheets on the supplier’s page: VladaChem, Clinivex, Achemtek.

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]EPA Chemical Data Reporting (CDR) · Public domain (US EPA) · via PubChem · retrieved 2026-10-14
[3]ILO-WHO International Chemical Safety Cards (ICSCs) · CC BY 4.0 · via PubChem · retrieved 2026-10-14
[4]Hazardous Substances Data Bank (HSDB) · Public domain (US NLM) · via PubChem · retrieved 2026-10-14
[5]PAC Chemical Database, U.S. Department of Energy · Public domain (US DOE) · via PubChem · retrieved 2026-10-14
[6]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
[7]European Chemicals Agency (ECHA) · ECHA legal notice: reuse with acknowledgement · via PubChem · retrieved 2026-10-14
[8]Emergency Response Guidebook (ERG) · Public domain (US DOT) · via PubChem · retrieved 2026-10-14
[9]NMRShiftDB · Linked only · via PubChem · retrieved 2026-10-14
[10]Human Metabolome Database (HMDB) · Linked only · via PubChem · retrieved 2026-10-14
[11]SpectraBase · Linked only · via PubChem · retrieved 2026-10-14
[12]MassBank of North America (MoNA) · CC BY 4.0 · via PubChem · retrieved 2026-10-14
[13]NIST Mass Spectrometry Data Center · Linked only · via PubChem · retrieved 2026-10-14
[14]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.