UN/NA Number Reference
DOT Class 3 Flammable Liquid placard

UN 2256: Cyclohexene

49 CFR 172.101 Hazardous Materials Table·ERG 2024

DOT Classification and Shipping

UN 2256 is assigned the proper shipping name Cyclohexene in the U.S. DOT Hazardous Materials Table (49 CFR 172.101). It is classified as a Class 3 Flammable Liquid material, Packing Group II. Required label(s): 3.

Packing group indicates the degree of danger within a hazard class: PG I is high danger, PG II medium, PG III low. The proper shipping name, hazard class, UN number, and packing group together form the basic shipping description that must appear on shipping papers and, where required, on the package and placard.

Emergency Response (ERG Guide 130)

Hazards: Flammable. Toxic vapor. Harmful if inhaled or absorbed. May accumulate in low areas.

Fire: Dry chemical, CO2, foam, water spray. Do not use straight streams.

Spill: Eliminate ignition sources. Stop leak. Absorb with sand/earth. Prevent waterway contamination.

Chemical and Physical Properties

Cyclohexene appears as a colorless liquid. Insoluble in water and less dense than water. Flash point 20 °F. Vapors heavier than air. Inhalation of high concentrations may have a narcotic effect. Used to make other chemicals.

CAS Number: 110-83-8
Molecular Formula: C6H10
Molecular Weight: 82.14 g/mol
Color / Form: Colorless liquid
Odor: Sweet odor
Boiling Point: 181 F
Melting Point: -154 °F (NIOSH, 2024)
Flash Point: 11 F
Autoignition: 471 °F (244 °C)
Specific Gravity: 0.81 (floats on water)
Vapor Pressure: 67 mmHg
Vapor Density: 2.8 (heavier than air)
Water Solubility: Insoluble
Log P: log Kow = 2.86

Regulatory Data

OSHA PEL
TWA 300 ppm (1015 mg/m 3 )
NIOSH REL
TWA 300 ppm (1015 mg/m 3 )
IDLH
2000 ppm

Special Provisions

49 CFR 172.102 special provision codes for this entry: IB2, T4, TP1. These codes modify the general requirements (packaging, quantity limits, exceptions) for this specific material. Look up each code in 49 CFR 172.102 for the full text.

Need the full interactive record? Open UN 2256 in the SpillNerd lookup tool for the live database entry with placard graphics, GHS pictograms, full segregation tables, and synonym search. For another material, use the UN number and chemical lookup.

Reference data compiled from the DOT Hazardous Materials Table (49 CFR 172.101), the 2024 Emergency Response Guidebook, and public chemical databases (PubChem, NIOSH, EPA). Always verify the correct shipping description against the current regulation and the manufacturer's SDS Section 14 before shipping.