UN/NA Number Reference

UN 2561: 3-Methyl-1-butene

49 CFR 172.101 Hazardous Materials Table·ERG 2024

DOT Classification and Shipping

UN 2561 is assigned the proper shipping name 3-Methyl-1-butene in the U.S. DOT Hazardous Materials Table (49 CFR 172.101). It is classified as a Class 3 Flammable Liquid material, Packing Group I. 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 128)

Hazards: HIGHLY FLAMMABLE. Vapors may form explosive mixtures with air. Vapors heavier than air. Runoff may pollute waterways.

Fire: Small: dry chemical, CO2, water spray, regular foam. Large: water spray, fog, regular foam. Do not use straight streams.

Spill: Eliminate ignition sources. Stop leak if safe. Use foam to suppress vapors. Absorb with earth, sand, or other absorbent. Prevent runoff to waterways.

Chemical and Physical Properties

3-methyl-1-butene appears as a colorless volatile liquid with a disagreeable odor. Insoluble in water and less dense than water. Vapors heavier than air. Used to make other chemicals.

CAS Number: 563-45-1

Molecular Formula: C5H10

Molecular Weight: 70.13 g/mol

Color / Form: ... gas

Odor: Disagreeable odor

Boiling Point: 20.1 C

Melting Point: -168.5 °C

Flash Point: less than 20 F

Autoignition: 689 °F (365 °C)

Specific Gravity: 0.6213 @ 25 C/4 C

Vapor Pressure: 903 mm Hg @ 25 C

Water Solubility: Soluble in benzene

Special Provisions

49 CFR 172.102 special provision codes for this entry: T11, TP2. 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 2561 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.