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Hexachlorocyclopentadiene Basic information

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Hexachlorocyclopentadiene Chemical Properties

Melting point:
−10 °C(lit.)
Boiling point:
239 °C753 mm Hg(lit.)
1.702 g/mL at 25 °C(lit.)
vapor pressure 
0.13 psi ( 20 °C)
refractive index 
n20/D 1.5644(lit.)
Flash point:
109 °C
storage temp. 
Yellow to amber-colored liquid
Water Solubility 
805ug/L(22.5 ºC)
Henry's Law Constant
1.64(x 10-2 atm?m3/mol) at 25 °C (gas stripping-GC, Warner et al., 1987) 1.6(x 10-2 atm?m3/mol) (Pankow and Rosen, 1988)
Exposure limits
NIOSH REL: 10 ppb (100 mg/m3); ACGIH TLV: TWA 0.01 ppm (adopted), 0.002 mg/m3 ppm (skin).
Stability Stable, but light-sensitive. Non-flammable. Very reactive with alkenes and polynuclear hydrocarbons. Explosive with sodium. Incompatible with strong oxidizing agents, most common metals.
CAS DataBase Reference
77-47-4(CAS DataBase Reference)
NIST Chemistry Reference
1,3-Cyclopentadiene, 1,2,3,4,5,5-hexachloro-(77-47-4)
EPA Substance Registry System
Hexachlorocyclopentadiene (77-47-4)

Safety Information

Hazard Codes 
Risk Statements 
Safety Statements 
UN 2646 6.1/PG 1
WGK Germany 
Hazardous Substances Data
77-47-4(Hazardous Substances Data)
Drinking water standard (final): MCLG: 50 μg/L:MCL: 50 μg/L. In addition, a DWEL of 200 μg/L was recommended (U.S. EPA, 2000).



Hexachlorocyclopentadiene Usage And Synthesis


Hexachlorocyclopentadiene is a pale-yellow/lemon-yellow liquid with a characteristic musty or pungent odour (odour threshold – 0.03 ppm). Hexachlorocyclopentadiene does not occur naturally but is a manufactured chemical. It easily evaporates into the air. Hexachlorocyclopentadiene is the key intermediate in the manufacture of some pesticides, including heptachlor, chlordane, aldrin, dieldrin, and endrin. Hexachlorocyclopentadiene is also used in the manufacture of flame retardants and some resins, shock-proof plastics, fluorocarbons, and dyes. Hexachlorocyclopentadiene quickly breaks down by sunlight and reacts with other chemicals in the air.

Chemical Properties

Pale-yellow liquid; pungent odor. Nonflammable.

Chemical Properties

Hexachlorocyclopentadiene is a pale-yellow to amber-colored, oily liquid. Pungent, unpleasant odor. The odor threshold is 0.15 0.33 ppm.

Physical properties

Pale yellow to greenish-yellow liquid with a harsh, unpleasant odor. Odor threshold concentrations ranged from 1.4 to 1.6 μg/L (quoted, Keith and Walters, 1992).


Intermediate in the manufacture of chlorinated pesticides; intermediate in the manufacture of flame retardants


Environmental neurotoxicant. Used in the preparation of some insecticides, flame retardants, and resins.

General Description

A pale yellow liquid with a pungent odor. Density 14.3 lb /gal. Solidifies at 50°F. Insoluble in water. Noncombustible. Very toxic by skin absorption and inhalation. Corrosive to tissue.

Air & Water Reactions

Insoluble in water. Reacts slowly with water to form hydrochloric acid.

Reactivity Profile

Hexachlorocyclopentadiene is incompatible with strong oxidizing and reducing agents. Also incompatible with many amines, nitrides, azo/diazo compounds, alkali metals (sodium), and epoxides.


Toxic by ingestion, inhalation, and skin absorption. Questionable carcinogen.

Health Hazard

Hexachlorocyclopentadiene is very toxic and may be fatal if inhaled, swallowed, or absorbed through the skin. The probable human lethal dose is 50-500 mg/kg, or between 1 teaspoon and 1 ounce for a 150 lb. (70 kg) person. Severe exposure induces pulmonary hyperemia and edema, degenerative and necrotic changes in brain, heart and adrenal glands and necrosis of liver and kidney tubules.

Fire Hazard

Toxic hydrogen chloride, chlorine, and phosgene gases may form in fires. In presence of moisture, will corrode iron and other materials; flammable and explosive hydrogen gas may collect in enclosed space. Will corrode iron and other metals in the presence of moisture. Reacts slowly with water to form hydrochloric acid; however, the reaction is not hazardous. Hazardous polymerization may not occur.

Potential Exposure

Hexachlorocyclopentadiene is used to produce the flame retardant chlorendic anhydride, which has applications in polyesters; and to produce chlorendic anhydride and chlorendic acid; which is used as a flame retardant in resins. Hexachlorocyclopentadiene is also used as an intermediate in the production of pesticides, such as aldrin, dieldrin, and endosulfan.

Environmental Fate

Biological. When hexachlorocyclopentadiene (5 and 10 mg/L) was statically incubated in the dark at 25 °C with yeast extract and settled domestic wastewater inoculum for 7 d, 100% biodegradation with rapid adaptation was observed (Tabak et al., 1981). In a model ecosystem containing plankton, Daphnia magna, mosquito larva (Culex pipiens quinquefasciatus), fish (Cambusia affinis), alga (Oedogonium cardiacum), and snail (Physa sp.), hexachlorocyclopentadiene degraded slightly, but no products were identified (Lu et al., 1975).
Photolytic. The major photolysis and hydrolysis products identified in distilled water were pentachlorocyclopentenone and hexachlorocyclopentenone. In mineralized water, the products identified include cis- and trans-pentachlorobutadiene, tetrachlorobutenyne, and pentachloropentadienoic acid (Chou and Griffin, 1983). In a similar experiment, irradiation of hexachlorocyclopentadiene in water by mercury-vapor lamps resulted in the formation of 2,3,4,4,5- pentachloro-2-cyclopentenone. This compound hydrolyzed partially to hexachloroindenone (Butz et al., 1982). Other photodegradation products identified include hexachloro-2-cyclopentenone and hexachloro-3-cyclopentenone as major products. Secondary photodegradation products reported include pentachloro-cis-2,4-pentadienoic acid, Z- and E-pentachlorobutadiene, and tetrachlorobutyne (Chou et al., 1987). In natural surface waters, direct photolysis of hexachlorobutadiene via sunlight results in a half-life of 10.7 min (Wolfe et al., 1982).
Chemical/Physical. Slowly reacts with water forming HCl and 1,1-dihydroxytetrachlorocyclopentadiene (Kollig, 1993; NIOSH, 1997). The diene is unstable forming polymers (Kollig, 1993).

Solubility in organics

Based on structurally similar compounds, hexachlorocyclopentadiene is expected to be soluble in benzene, ethanol, chloroform, methylene chloride, trichloroethylene, and other liquid halogenated solvents.

Solubility in water

Based on structurally similar compounds, hexachlorocyclopentadiene is expected to be soluble in benzene, ethanol, chloroform, methylene chloride, trichloroethylene, and other liquid halogenated solvents.


UN2646 Hexachlorocyclopentadiene, Hazard Class: 6.1; Labels: 6.1-Poison Inhalation Hazard, Inhalation Hazard Zone B.

Purification Methods

Dry the diene with MgSO4, filter, and distil it under vacuum in a nitrogen atmosphere. Irritates skin and eyes, HIGHLY TOXIC. [McBee et al. J Am Chem Soc 77 4378 1955, UV spectra: Idol et al. J Org Chem 20 1746 1955, Beilstein 5 III 308, 5 IV 381.]


Reacts slowly with water to form hydro chloric acid; will corrode iron and most metals in presence of moisture. Explosive hydrogen gas may collect in enclosed spaces in the presence of moisture. Contact with sodium may be explosive.

Waste Disposal

Incineration after mixing with another combustible fuel. Care must be exercised to assure complete combustion to prevent the formation of phosgene. An acid scrubber is necessary to remove the halo acids pro duced. Consult with environmental regulatory agencies for guidance on acceptable disposal practices. Generators of waste containing this contaminant (≥100 kg/mo) must con form to EPA regulations governing storage, transportation, treatment, and waste disposal.



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