Cyclopentanone

1Identification

Name

Cyclopentanone

IUPAC name

cyclopentanone

CAS number

120-92-3

EC number

204-435-9

Molecular formula

C5H8O

Molecular weight

84.12 g/mol

InChIKey

BGTOWKSIORTVQH-UHFFFAOYSA-N

SMILES

C1CCC(=O)C1

PubChem CID

8452

Synonyms

Adipic ketone, Ketocyclopentane, Ketopentamethylene, Dumasin, Adipinketon, Adipin keton, RefChem:5722, cyclopentan-1-one, oxocyclopentane, cyclopentanon, CYCLOPENTANONE (2,2,5,5-D4), cyclopentaneon, Dumasine, cyclo-pentanone

Recommended uses

• Used as intermediate for pharmaceuticals, biologicals, insecticides, and rubber chemicals; [Hawley]
  Haz-Map, Information on Hazardous Chemicals and Occupational Diseases
• INT FOR PHARMACEUTICALS, BIOLOGICALS, INSECTICIDES, & RUBBER CHEMICALS.
  Hazardous Substances Data Bank (HSDB)
• Solvent Intermediate
  EPA Chemical Data Reporting (CDR)
• Fragrance
  EPA Chemical Data Reporting (CDR)

Use categories: Flavouring Agent -> FLAVOURING_AGENT -> JECFA Functional Classes · Flavoring Agents -> JECFA Flavorings Index

Description

• Cyclopentanone appears as a clear colorless liquid with a petroleum-like odor. Flash point 87 °F. Less dense than water and insoluble in water. Vapors heavier than air.
  CAMEO Chemicals
• Cyclopentanone is a cyclic ketone that consists of cyclopentane bearing a single oxo substituent. It has a role as a Maillard reaction product.
  ChEBI
• structure
  Medical Subject Headings (MeSH)

2Hazard identification

Signal word

Warning

Pictograms

GHS02, GHS07

Classification source

Regulation (EC) No 1272/2008 of the European Parliament and of the Council

Precautionary statements

Other reported classifications

4 classification records exist across sources. Differences usually reflect purity, physical form or impurities.

NFPA 704 rating

• 2 - Materials that, under emergency conditions, can cause temporary incapacitation or residual injury.
  Hazardous Substances Data Bank (HSDB)
• 3 - Liquids and solids that can be ignited under almost all ambient temperature conditions. Materials produce hazardous atmospheres with air under almost all ambient temperatures or, though unaffected by ambient temperatures, are readily ignited under almost all conditions.
  Hazardous Substances Data Bank (HSDB)
• 0 - Materials that in themselves are normally stable, even under fire conditions.
  Hazardous Substances Data Bank (HSDB)

Health hazards

• Excerpt from ERG Guide 128 [Flammable Liquids (Water-Immiscible)]: CAUTION: Petroleum crude oil (UN1267) may contain TOXIC hydrogen sulphide gas. Inhalation or contact with material may irritate or burn skin and eyes. Fire may produce irritating, corrosive and/or toxic gases. Vapors may cause dizziness or asphyxiation, especially when in closed or confined areas. Runoff from fire control or dilution water may cause environmental contamination. (ERG, 2024)
  CAMEO Chemicals
• CAUTION: Petroleum crude oil (UN1267) may contain TOXIC hydrogen sulphide gas. · Inhalation or contact with material may irritate or burn skin and eyes. · Fire may produce irritating, corrosive and/or toxic gases. · Vapors may cause dizziness or asphyxiation, especially when in closed or confined areas. · Runoff from fire control or dilution water may cause environmental contamination.
  Emergency Response Guidebook (ERG)

Fire hazards

• Excerpt from ERG Guide 128 [Flammable Liquids (Water-Immiscible)]: HIGHLY FLAMMABLE: Will be easily ignited by heat, sparks or flames. Vapors may form explosive mixtures with air. Vapors may travel to source of ignition and flash back. Most vapors are heavier than air. They will spread along the ground and collect in low or confined areas (sewers, basements, tanks, etc.). Vapor explosion hazard indoors, outdoors or in sewers. Those substances designated with a (P) may polymerize explosively when heated or involved in a fire. Runoff to sewer may create fire or explosion hazard. Containers may explode when heated. Many liquids will float on water. Substance may be transported hot.
  CAMEO Chemicals
• · HIGHLY FLAMMABLE: Will be easily ignited by heat, sparks or flames. · Vapors may form explosive mixtures with air. · Vapors may travel to source of ignition and flash back. · Most vapors are heavier than air. They will spread along the ground and collect in low or confined areas (sewers, basements, tanks, etc.). · Vapor explosion hazard indoors, outdoors or in sewers. · Those substances designated with a (P) may polymerize explosively when heated or involved in a fire. · Runoff to sewer may create fire or explosion hazard. · Containers may explode when heated. · Many liquids will float on water. · Substance may be transported hot.
  Emergency Response Guidebook (ERG)
• Flammable. Heating will cause rise in pressure with risk of bursting. Gas/air mixtures are explosive.
  ILO-WHO International Chemical Safety Cards (ICSCs)

Hazards summary

• A skin and eye irritant; A possible respiratory tract irritant; Can be absorbed through skin; [ICSC] Inhalation of high concentrations can cause CNS depression; [HSDB] May cause irritation or burns to skin and eyes; [CAMEO] A skin and eye irritant; [eChemPortal: ESIS] Oral LD50 (mouse) = 1820 mg/kg; Effects in high-dose animal studies include somnolence, coma, and other changes to liver; [RTECS] Safe when used as a flavoring agent; [JECFA]
  Haz-Map, Information on Hazardous Chemicals and Occupational Diseases
• The major hazards encountered in the use and handling of cyclopentanone stem from its toxicologic properties and flammability. Toxic by all routes (ie, inhalation, ingestion, and dermal absorption), exposure to this peppermint-smelling, water-white liquid may occur from its production and use as an intermediate for pharmaceuticals, biologicals, insecticides, and rubber chemicals. Effects from exposure may include contact burns to the skin and eyes, CNS depression, and suffocation. In activities and situations where over-exposure may occur, wear protective clothing and a positive pressure self-contained breathing apparatus.
  Hazardous Substances Data Bank (HSDB)

3Composition / information on ingredients

This page describes the pure substance. Commercial products may be solutions or mixtures. Check Section 3 of your supplier's SDS for concentrations and other ingredients.

4First-aid measures

• EYES: First check the victim for contact lenses and remove if present. Flush victim's eyes with water or normal saline solution for 20 to 30 minutes while simultaneously calling a hospital or poison control center. Do not put any ointments, oils, or medication in the victim's eyes without specific instructions from a physician. IMMEDIATELY transport the victim after flushing eyes to a hospital even if no symptoms (such as redness or irritation) develop. SKIN: IMMEDIATELY flood affected skin with water while removing and isolating all contaminated clothing. Gently wash all affected skin areas thoroughly with soap and water.
  CAMEO Chemicals
• 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 with a one-way valve or other device).
  Emergency Response Guidebook (ERG)

Symptoms of exposure

• Cough. Sore throat.
  ILO-WHO International Chemical Safety Cards (ICSCs)
• Redness. Pain.
  ILO-WHO International Chemical Safety Cards (ICSCs)

5Fire-fighting measures

• ALCOHOL FOAM, CARBON DIOXIDE, DRY CHEM.
  Hazardous Substances Data Bank (HSDB)

6Accidental release measures

Isolation and evacuation

• Excerpt from ERG Guide 128 [Flammable Liquids (Water-Immiscible)]: IMMEDIATE PRECAUTIONARY MEASURE: Isolate spill or leak area for at least 50 meters (150 feet) in all directions. LARGE SPILL: Consider initial downwind evacuation for at least 300 meters (1000 feet). FIRE: If tank, rail tank car or highway tank is involved in a fire, ISOLATE for 800 meters (1/2 mile) in all directions; also, consider initial evacuation for 800 meters (1/2 mile) in all directions. (ERG, 2024)
  CAMEO Chemicals
• Immediate precautionary measure · Isolate spill or leak area for at least 50 meters (150 feet) in all directions. Large Spill · Consider initial downwind evacuation for at least 300 meters (1000 feet). Fire · If tank, rail tank car or highway tank is involved in a fire, ISOLATE for 800 meters (1/2 mile) in all directions; also, consider initial evacuation for 800 meters (1/2 mile) in all directions.
  Emergency Response Guidebook (ERG)

Spill cleanup

• Collect leaking liquid in sealable containers. Absorb remaining liquid in sand or inert absorbent. Then store and dispose of according to local regulations.
  ILO-WHO International Chemical Safety Cards (ICSCs)

7Handling and storage

• Fireproof. Separated from acids. Cool. Keep in the dark. Keep in a well-ventilated room. Store only if stabilized.
  ILO-WHO International Chemical Safety Cards (ICSCs)

8Exposure controls / personal protection

No occupational exposure limits found in our sources.

Personal protective equipment

• Excerpt from ERG Guide 128 [Flammable Liquids (Water-Immiscible)]: Wear positive pressure self-contained breathing apparatus (SCBA). Structural firefighters' protective clothing provides thermal protection but only limited chemical protection. (ERG, 2024)
  CAMEO Chemicals

9Physical and chemical properties

10Stability and reactivity

Reactivity

• CYCLOPENTANONE polymerizes easily, especially in the presence of acids. Can react with oxidizing materials, i.e. hydrogen peroxide. (NTP, 1992)
  CAMEO Chemicals
• Highly flammable. Insoluble in water.
  CAMEO Chemicals

11Toxicological information

Short-term exposure effects

• The substance is irritating to the eyes, skin and possibly the respiratory tract.
  ILO-WHO International Chemical Safety Cards (ICSCs)

12Ecological information

Not available in the public sources we compile. Check Section 12 of the supplier's SDS.

13Disposal considerations

• The following wastewater treatment technologies have been investigated for cyclopentanone: concentration process: Biological treatment
  Hazardous Substances Data Bank (HSDB)

14Transport information

UN number: UN 2245

Shipping name

• UN 2245; Cyclopentanone
  Hazardous Substances Data Bank (HSDB)
• IMO 3.3; Cyclopentanone
  Hazardous Substances Data Bank (HSDB)

DOT hazard class

• Cyclopentanone
  US Code of Federal Regulations, Hazardous Materials, 49 CFR Part 172
• UN2245
  US Code of Federal Regulations, Hazardous Materials, 49 CFR Part 172
• Class 3 Flammable and combustible liquid (49 eCFR § 173.120)
  US Code of Federal Regulations, Hazardous Materials, 49 CFR Part 172

DOT label

• Flammable Liquid
  CAMEO Chemicals

UN classification

• UN Hazard Class: 3; UN Pack Group: III
  ILO-WHO International Chemical Safety Cards (ICSCs)

Emergency Response Guidebook

• 2245 128
  Emergency Response Guidebook (ERG)

How DOT hazard classes work →

15Regulatory information

No specific US regulatory listings found in our sources. Check Section 15 of your supplier's SDS for TSCA, SARA 313, CERCLA, Prop 65 and state listings.

Overview of SDS regulations (OSHA HazCom, WHMIS, REACH/CLP) →

16Other information

Compiled from PubChem CID 8452 and the sources it aggregates (attributed inline). Data retrieved 2026-10-12. This summary describes the pure substance and is not a supplier SDS.