UN/NA Number Reference
DOT Class 6.1 Toxic Substance placard

UN 2021: Chlorophenols, liquid

49 CFR 172.101 Hazardous Materials Table·ERG 2024

DOT Classification and Shipping

UN 2021 is assigned the proper shipping name Chlorophenols, liquid in the U.S. DOT Hazardous Materials Table (49 CFR 172.101). It is classified as a Class 6.1 Toxic Substance material, Packing Group III. Required label(s): 6.1.

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 153)

Hazards: TOXIC. Combustible. Corrosive. Causes burns. Toxic fumes when heated.

Fire: Small: dry chemical, CO2, water spray. Large: water spray, foam.

Spill: Do not touch. Stop leak if safe. Use water spray to reduce vapor.

Chemical and Physical Properties

2,3,4,6-tetrachlorophenol appears as brown flakes or beige solid. Strong odor. (NTP, 1992)

CAS Number: 58-90-2
Molecular Formula: C6H2Cl4O
Molecular Weight: 231.9 g/mol
Color / Form: NEEDLES FROM LIGROIN, ACETIC ACID
Odor: STRONG ODOR
Boiling Point: 302 F
Melting Point: 158 °F (NTP, 1992)
Flash Point: 100Â °C
Specific Gravity: 1.839
Vapor Pressure: 1 mmHg
Water Solubility: less than 1 mg/mL at 68 °F (NTP, 1992)
Log P: log Kow= 4.45

Regulatory Data

CERCLA RQ (40 CFR 302.4)
10 lb
RCRA Waste Code(s)
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A release of this material at or above its CERCLA reportable quantity (10 lb) requires immediate notification to the National Response Center at 800-424-8802.

Special Provisions

49 CFR 172.102 special provision codes for this entry: IB3, 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 2021 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.