Cyclopentane

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C₅H₁₀ · 70.13 g/mol

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DangerHighly Flammable liquid and vapor · Harmful to aquatic life with long lasting effects

Names and identifiers

IUPAC name: cyclopentane
Synonyms: Pentamethylene, ciclopentano, cyclopentan
+ 35 more
Zyklopentan, DTXSID6024886, T86PB90RNU, NSC-60213, DTXCID804886, CHEBI:23492, RefChem:129861, 206-016-6, MFCD00001356, HSDB 62, EINECS 206-016-6, NSC 60213, UN1146, UNII-T86PB90RNU, Cyclopentanes, trans-cyclopentane, CYCLOPENTANE [MI], Cyclopentane, HPLC Grade, CYCLOPENTANE 75%, WLN: L5TJ, CYCLOPENTANE [HSDB], EC 206-016-6, SCHEMBL1207, SCHEMBL2495, SCHEMBL2648, SCHEMBL5310, SCHEMBL104907, SCHEMBL135360, SCHEMBL146255, SCHEMBL216292, SCHEMBL312936, SCHEMBL2468301, SCHEMBL2992458, SCHEMBL3788025, SCHEMBL4132547
Molecular formula: C₅H₁₀
Empirical formula: CH₂
Molecular weight: 70.13 g/mol
Exact mass: 70.07825
CAS number: 287-92-3
PubChem CID: 9253
Canonical SMILES: C1CCCC1
Isomeric SMILES: C1CCCC1
InChI: InChI=1S/C5H10/c1-2-4-5-3-1/h1-5H2
InChIKey: RGSFGYAAUTVSQA-UHFFFAOYSA-N
Molfile

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

Physical properties

TemperaturePressureDensity

Appearance: Colorless liquid[6]
6 values
From Hazardous Substances Data Bank (HSDB), the most authoritative source here.
Value As written Source
– Cyclopentane appears as a clear colorless liquid with a petroleum-like odor. Flash point of -35 °F. Less dense than water and insoluble in water. Vapors are heavier than air. [1] CAMEO Chemicals
– Liquid [2] EPA Chemical Data Reporting (CDR)
– COLOURLESS LIQUID WITH MILD ODOUR. [3] ILO-WHO International Chemical Safety Cards (ICSCs)
– Colorless liquid with a mild, sweet odor. [4] Occupational Safety and Health Administration (OSHA)
– Colorless liquid with a mild, sweet odor. [5] The National Institute for Occupational Safety and Health (NIOSH)
–shown Colorless liquid [6] Hazardous Substances Data Bank (HSDB)cites NIOSH. NIOSH Pocket Guide to Chemical Hazards. Department of Health & Human Services, Centers for Disease Control & Prevention. National Institute for Occupational Safety & Health. DHHS (NIOSH) Publication No. 2010-168 (2010). Available from: https://www.cdc.gov/niosh/npg
Odor: Mild, sweet odor[6]
Melting point: -93.7 °C[7]
5 values
5 of 5 sources agree on it (most common value).
Value As written Source
−94 °C -137 °F (USCG, 1999) [1] CAMEO Chemicalscites U.S. Coast Guard. 1999. Chemical Hazard Response Information System (CHRIS) - Hazardous Chemical Data. Commandant Instruction 16465.12C. Washington, D.C.: U.S. Government Printing Office.
−94 °C -94 °C [3] ILO-WHO International Chemical Safety Cards (ICSCs)
−94 °C -137 °F [4] Occupational Safety and Health Administration (OSHA)
−93.7 °Cshown -93.7 °C [7] PAC Chemical Database, U.S. Department of Energy
−94 °C -137 °F [5] The National Institute for Occupational Safety and Health (NIOSH)
Boiling point: 49.3 °C (120.7 °F) at 760 mmHg (USCG, 1999)[1]
5 values
5 of 5 sources agree on it (most common value).
Value As written Source
49.3 °Cshown 120.7 °F at 760 mmHg (USCG, 1999) [1] CAMEO Chemicalscites U.S. Coast Guard. 1999. Chemical Hazard Response Information System (CHRIS) - Hazardous Chemical Data. Commandant Instruction 16465.12C. Washington, D.C.: U.S. Government Printing Office.
49 °C 49 °C [3] ILO-WHO International Chemical Safety Cards (ICSCs)
49 °C 121 °F [4] Occupational Safety and Health Administration (OSHA)
49.3 °C 49.3 °C @760 [mm Hg] [7] PAC Chemical Database, U.S. Department of Energy
49 °C 121 °F [5] The National Institute for Occupational Safety and Health (NIOSH)
Density: 0.7457 @ 20°C[7]
5 values
4 of 5 sources agree on it (most common value).
Value As written Source
– 0.74 at 68 °F (USCG, 1999) - Less dense than water [1] CAMEO Chemicalscites U.S. Coast Guard. 1999. Chemical Hazard Response Information System (CHRIS) - Hazardous Chemical Data. Commandant Instruction 16465.12C. Washington, D.C.: U.S. Government Printing Office.
– Relative density (water = 1): 0.8 (20 °C) [3] ILO-WHO International Chemical Safety Cards (ICSCs)
– 0.75 [4] Occupational Safety and Health Administration (OSHA)
–shown 0.7457 @ 20°C [7] PAC Chemical Database, U.S. Department of Energy
– 0.75 [5] The National Institute for Occupational Safety and Health (NIOSH)
Solubility in water: Solubility in water: none[3]
4 values
From ILO-WHO International Chemical Safety Cards (ICSCs), the most authoritative source here.
Value As written Source
– Insoluble (NIOSH, 2024) [1] CAMEO Chemicals
– In water, 156 ppm at 25 °C [6] Hazardous Substances Data Bank (HSDB)cites Yalkowsky, S.H., He, Yan, Jain, P. Handbook of Aqueous Solubility Data Second Edition. CRC Press, Boca Raton, FL 2010, p. 158
–shown Solubility in water: none [3] ILO-WHO International Chemical Safety Cards (ICSCs)
– Insoluble [5] The National Institute for Occupational Safety and Health (NIOSH)
log P: log Kow = 3.00[6]
2 values
2 of 2 sources agree on it (most common value).
Value As written Source
–shown log Kow = 3.00 [6] 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. 14
– 3.0 [3] ILO-WHO International Chemical Safety Cards (ICSCs)
Vapor pressure: VP: 400 mmHg at 31.0 °C[6]
6 values
3 of 5 sources agree on it (most common value).
Value As written Source
400 mmHg 400 mmHg at 88 °F (NIOSH, 2024) [1] CAMEO Chemicals
400 mmHgshown VP: 400 mm Hg at 31.0 °C [6] Hazardous Substances Data Bank (HSDB)cites Lewis, R.J. Sr. (ed) Sax's Dangerous Properties of Industrial Materials. 11th Edition. Wiley-Interscience, Wiley & Sons, Inc. Hoboken, NJ. 2004., p. V2: 1048
317.8 mmHg 317.8 mm Hg at 25 °C [6] 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.
340 mmHg Vapor pressure, kPa at 20 °C: 45 [3] ILO-WHO International Chemical Safety Cards (ICSCs)
400 mmHg 400 mmHg at 88 °F [4] Occupational Safety and Health Administration (OSHA)
317.8 mmHg 317.8 [mm Hg] @25 °C [7] PAC Chemical Database, U.S. Department of Energy
1 more value was reported but failed the checks (unreadable or out of range), so it is not shown.
Flash point: -37 °C c.c.[3]
6 values
2 of 3 sources agree on it (most common value).
Value As written Source
< −7 °C less than 20 °F (USCG, 1999) [1] CAMEO Chemicalscites U.S. Coast Guard. 1999. Chemical Hazard Response Information System (CHRIS) - Hazardous Chemical Data. Commandant Instruction 16465.12C. Washington, D.C.: U.S. Government Printing Office.
−20 °C -20 °C (-4 °F) (Closed cup) [6] Hazardous Substances Data Bank (HSDB)cites Sigma-Aldrich; Material Safety Data Sheet for Cyclopentane. Product Number: 459747, Version 4.5 (Revision Date 06/30/2014). Available from, as of October 7, 2014: https://www.sigmaaldrich.com/safety-center.html
< −7 °C <20 °F (<-7 °C) (Closed cup) [6] Hazardous Substances Data Bank (HSDB)cites National Fire Protection Association; Fire Protection Guide to Hazardous Materials. 14TH Edition, Quincy, MA 2010, p. 325-35
−37 °Cshown -37 °C c.c. [3] ILO-WHO International Chemical Safety Cards (ICSCs)
< −7 °C <20 °F [4] Occupational Safety and Health Administration (OSHA)
−37 °C -35 °F [5] The National Institute for Occupational Safety and Health (NIOSH)
Autoignition temperature: 361 °C (682 °F)[6]
3 values
2 of 3 sources agree on it (most common value).
Value As written Source
361 °C 682 °F (USCG, 1999) [1] CAMEO Chemicalscites U.S. Coast Guard. 1999. Chemical Hazard Response Information System (CHRIS) - Hazardous Chemical Data. Commandant Instruction 16465.12C. Washington, D.C.: U.S. Government Printing Office.
361 °Cshown 682 °F (361 °C) [6] Hazardous Substances Data Bank (HSDB)cites National Fire Protection Association; Fire Protection Guide to Hazardous Materials. 14TH Edition, Quincy, MA 2010, p. 325-35
320 °C 320 °C [3] ILO-WHO International Chemical Safety Cards (ICSCs)
Viscosity: Reported, but no value passed the checks.
The value and why
O.44 mPa*s at 20 °C (could not be read; source [3])

Value	As written	Source
–	Cyclopentane appears as a clear colorless liquid with a petroleum-like odor. Flash point of -35 °F. Less dense than water and insoluble in water. Vapors are heavier than air.	[1] CAMEO Chemicals
–	Liquid	[2] EPA Chemical Data Reporting (CDR)
–	COLOURLESS LIQUID WITH MILD ODOUR.	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
–	Colorless liquid with a mild, sweet odor.	[4] Occupational Safety and Health Administration (OSHA)
–	Colorless liquid with a mild, sweet odor.	[5] The National Institute for Occupational Safety and Health (NIOSH)
–shown	Colorless liquid	[6] Hazardous Substances Data Bank (HSDB)cites NIOSH. NIOSH Pocket Guide to Chemical Hazards. Department of Health & Human Services, Centers for Disease Control & Prevention. National Institute for Occupational Safety & Health. DHHS (NIOSH) Publication No. 2010-168 (2010). Available from: https://www.cdc.gov/niosh/npg

Value	As written	Source
−94 °C	-137 °F (USCG, 1999)	[1] CAMEO Chemicalscites U.S. Coast Guard. 1999. Chemical Hazard Response Information System (CHRIS) - Hazardous Chemical Data. Commandant Instruction 16465.12C. Washington, D.C.: U.S. Government Printing Office.
−94 °C	-94 °C	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
−94 °C	-137 °F	[4] Occupational Safety and Health Administration (OSHA)
−93.7 °Cshown	-93.7 °C	[7] PAC Chemical Database, U.S. Department of Energy
−94 °C	-137 °F	[5] The National Institute for Occupational Safety and Health (NIOSH)

Value	As written	Source
49.3 °Cshown	120.7 °F at 760 mmHg (USCG, 1999)	[1] CAMEO Chemicalscites U.S. Coast Guard. 1999. Chemical Hazard Response Information System (CHRIS) - Hazardous Chemical Data. Commandant Instruction 16465.12C. Washington, D.C.: U.S. Government Printing Office.
49 °C	49 °C	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
49 °C	121 °F	[4] Occupational Safety and Health Administration (OSHA)
49.3 °C	49.3 °C @760 [mm Hg]	[7] PAC Chemical Database, U.S. Department of Energy
49 °C	121 °F	[5] The National Institute for Occupational Safety and Health (NIOSH)

Value	As written	Source
–	0.74 at 68 °F (USCG, 1999) - Less dense than water	[1] CAMEO Chemicalscites U.S. Coast Guard. 1999. Chemical Hazard Response Information System (CHRIS) - Hazardous Chemical Data. Commandant Instruction 16465.12C. Washington, D.C.: U.S. Government Printing Office.
–	Relative density (water = 1): 0.8 (20 °C)	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
–	0.75	[4] Occupational Safety and Health Administration (OSHA)
–shown	0.7457 @ 20°C	[7] PAC Chemical Database, U.S. Department of Energy
–	0.75	[5] The National Institute for Occupational Safety and Health (NIOSH)

Value	As written	Source
–	Insoluble (NIOSH, 2024)	[1] CAMEO Chemicals
–	In water, 156 ppm at 25 °C	[6] Hazardous Substances Data Bank (HSDB)cites Yalkowsky, S.H., He, Yan, Jain, P. Handbook of Aqueous Solubility Data Second Edition. CRC Press, Boca Raton, FL 2010, p. 158
–shown	Solubility in water: none	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
–	Insoluble	[5] The National Institute for Occupational Safety and Health (NIOSH)

Value	As written	Source
–shown	log Kow = 3.00	[6] 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. 14
–	3.0	[3] ILO-WHO International Chemical Safety Cards (ICSCs)

Value	As written	Source
400 mmHg	400 mmHg at 88 °F (NIOSH, 2024)	[1] CAMEO Chemicals
400 mmHgshown	VP: 400 mm Hg at 31.0 °C	[6] Hazardous Substances Data Bank (HSDB)cites Lewis, R.J. Sr. (ed) Sax's Dangerous Properties of Industrial Materials. 11th Edition. Wiley-Interscience, Wiley & Sons, Inc. Hoboken, NJ. 2004., p. V2: 1048
317.8 mmHg	317.8 mm Hg at 25 °C	[6] 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.
340 mmHg	Vapor pressure, kPa at 20 °C: 45	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
400 mmHg	400 mmHg at 88 °F	[4] Occupational Safety and Health Administration (OSHA)
317.8 mmHg	317.8 [mm Hg] @25 °C	[7] PAC Chemical Database, U.S. Department of Energy

Value	As written	Source
< −7 °C	less than 20 °F (USCG, 1999)	[1] CAMEO Chemicalscites U.S. Coast Guard. 1999. Chemical Hazard Response Information System (CHRIS) - Hazardous Chemical Data. Commandant Instruction 16465.12C. Washington, D.C.: U.S. Government Printing Office.
−20 °C	-20 °C (-4 °F) (Closed cup)	[6] Hazardous Substances Data Bank (HSDB)cites Sigma-Aldrich; Material Safety Data Sheet for Cyclopentane. Product Number: 459747, Version 4.5 (Revision Date 06/30/2014). Available from, as of October 7, 2014: https://www.sigmaaldrich.com/safety-center.html
< −7 °C	<20 °F (<-7 °C) (Closed cup)	[6] Hazardous Substances Data Bank (HSDB)cites National Fire Protection Association; Fire Protection Guide to Hazardous Materials. 14TH Edition, Quincy, MA 2010, p. 325-35
−37 °Cshown	-37 °C c.c.	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
< −7 °C	<20 °F	[4] Occupational Safety and Health Administration (OSHA)
−37 °C	-35 °F	[5] The National Institute for Occupational Safety and Health (NIOSH)

Value	As written	Source
361 °C	682 °F (USCG, 1999)	[1] CAMEO Chemicalscites U.S. Coast Guard. 1999. Chemical Hazard Response Information System (CHRIS) - Hazardous Chemical Data. Commandant Instruction 16465.12C. Washington, D.C.: U.S. Government Printing Office.
361 °Cshown	682 °F (361 °C)	[6] Hazardous Substances Data Bank (HSDB)cites National Fire Protection Association; Fire Protection Guide to Hazardous Materials. 14TH Edition, Quincy, MA 2010, p. 325-35
320 °C	320 °C	[3] ILO-WHO International Chemical Safety Cards (ICSCs)

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: 0
Fraction sp³ carbons (Fsp3): 1
H-bond donors: 0
H-bond acceptors: 0
Rotatable bonds: 0
TPSA (Å²): 0
Formal charge: 0
XLogP3: 3 PubChem
Complexity: 11 PubChem
Stereocenters: None
Double-bond geometry: None specified
Point group: C2 of one 3D conformer with its hydrogens, by Athanor’s engine (as in the app)

Elemental analysis

C85.63%
H14.37%

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: 1.95 Crippen (Wildman and Crippen 1999)
log S (water solubility): -1.5 ESOL (Delaney 2004), log mol/L
Synthetic accessibility: 1 SA score, 1 easy to 10 hard (Ertl and Schuffenhauer 2009)

Drug-likeness: Lipinski’s rule of five

Molecular weight ≤ 500: 70.14
log P ≤ 5 (Crippen): 1.95
H-bond donors ≤ 5: 0
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

Danger

Harmonized EU classification (CLP Annex VI). Source [8].

Flammable

NFPA 704[6]

H225Highly Flammable liquid and vapor
H412Harmful to aquatic life with long lasting effects

Precautionary statements: P210, P233, P240, P241, P242, P243, P273, P280, P303+P361+P353, P370+P378, P403+P235, P501

View all classifications (3)

[8] Regulation (EC) No 1272/2008 of the European Parliament and of the Council · DangerH225, H412
[9] European Chemicals Agency (ECHA) · 763 reports · DangerH225, H304, H336, H412
[6] Hazardous Substances Data Bank (HSDB) · DangerH225, H402, H412

Exposure limits

PEL: None See Appendix G[5]
REL-TWA (Time Weighted Average): 600 ppm (1720 mg/m³)[4]
REL: TWA 600 ppm (1720 mg/m3)[5]
TLV: 600 ppm as TWA[3]
TLV-TWA (Time Weighted Average): 1000 ppm [2021][4]
IDLH: N.D. See: IDLH index[5]

First aid

Excerpt from NIOSH Pocket Guide for Cyclopentane: Eye: Irrigate immediately - If this chemical contacts the eyes, immediately wash (irrigate) the eyes with large amounts of water, occasionally lifting the lower and upper lids. Get medical attention immediately. Skin: SOAP WASH - If this chemical contacts the skin, wash the contaminated skin with soap and water. Breathing: Respiratory support - If a person breathes large amounts of this chemical, move the exposed person to fresh air at once. If breathing has stopped, perform artificial respiration. Keep the affected person warm and at rest.[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…[10]
(General first aid procedures) Eye: Irrigate immediately - If this chemical contacts the eyes, immediately wash (irrigate) the eyes with large amounts of water, occasionally lifting the lower and upper lids. Get medical attention immediately. Skin: Soap wash - If this chemical contacts the skin, wash the contaminated skin with soap and water. Breathing: Respiratory support Swallow: Medical attention immediately - If this chemical has been swallowed, get medical attention immediately.[5]
Fresh air, rest. Refer for medical attention.[3]

Storage

Fireproof. Well closed. Separated from strong oxidants and food and feedstuffs. Store in an area without drain or sewer access. Provision to contain effluent from fire extinguishing.[3]
Conditions for safe storage, including any incompatibilities: Keep container tightly closed in a dry and well-ventilated place. Containers which are opened must be carefully resealed and kept upright to prevent leakage.[6]

Incompatibilities

Strong oxidizers (e.g. Chlorine, bromine, fluorine).[6]
Incompatible materials: Strong oxidizing agents.[6]
Strong oxidizers (e.g., chlorine, bromine, fluorine)[5]

Safety data sheets on the supplier’s page: EvitaChem, Sinfoo Biotech, LGC Standards.

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]Occupational Safety and Health Administration (OSHA) · Public domain (US DOL) · via PubChem · retrieved 2026-10-14
[5]The National Institute for Occupational Safety and Health (NIOSH) · Public domain (US CDC) · via PubChem · retrieved 2026-10-14
[6]Hazardous Substances Data Bank (HSDB) · Public domain (US NLM) · via PubChem · retrieved 2026-10-14
[7]PAC Chemical Database, U.S. Department of Energy · Public domain (US DOE) · via PubChem · retrieved 2026-10-14
[8]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
[9]European Chemicals Agency (ECHA) · ECHA legal notice: reuse with acknowledgement · via PubChem · retrieved 2026-10-14
[10]Emergency Response Guidebook (ERG) · Public domain (US DOT) · via PubChem · retrieved 2026-10-14
[11]NMRShiftDB · Linked only · via PubChem · retrieved 2026-10-14
[12]SpectraBase · Linked only · via PubChem · retrieved 2026-10-14
[13]MassBank of North America (MoNA) · CC BY 4.0 · via PubChem · retrieved 2026-10-14
[14]NIST Mass Spectrometry Data Center · Linked only · via PubChem · retrieved 2026-10-14
[15]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.