Chemical Name: Hexachlorocyclopentadiene
IUPAC NAME: 1,2,3,4,5,5-hexachlorocyclopenta-1,3-diene
CAS No.: 77-47-4
EINECS: 201-029-3
RTECS: GY1225000
RTECS Class: Agricultural Chemical and Pesticide ;  Tumorigen ;  Reproductive Effector ;  Primary Irritant
EC Class: Very toxic ;  Toxic ;  Harmful ;  Corrosive ;  Dangerous for the Environment
Molecular Formula: C₅Cl₆
Molecular Weight: 272.77 g/mol
Melting Point: -10 °C(lit.)
Density: 1.83 g/cm³ 
Flash Point: 100.2 °C
Boiling Point: 242.8 °C at 760 mmHg 
Following is the structure of Hexachlorocyclopentadiene (77-47-4):

Product Categories about Hexachlorocyclopentadiene (77-47-4) are Pharmaceutical Intermediates ; Organics ; Method 612 ; 600 Series Wastewater Methods ; Alpha Sort ; E-LAlphabetic ; H ; HA -HTEPA ; Volatiles/ Semivolatiles ; 500 Series Drinking Water Methods ; Method 508
The chemical synonymous of Hexachlorocyclopentadiene (77-47-4) are Hexachlorocyclopentadiene ; Cyclopentadiene hexachloride ; Perchlorocyclopentadiene ; 1,2,3,4,5,5’-Hexachloro-1,3-cyclopentadiene ; 1,2,3,4,5,5-Hexachloro-1,3-cyclopentadiene ; 1,2,3,4,5,5-Hexachloro-3-cyclopentadiene ; 1,2,3,4,5,5-Hexachloro-cyclopenta-1,3-diene ; 1,3-Cyclopentadiene, hexachloro-

EPA Extremely Hazardous Substances List. Community Right-To-Know List. Reported in EPA TSCA Inventory.

A deadly poison by inhalation. Moderately toxic by ingestion and skin contact. Experimental teratogenic effects. Corrosive. A severe skin and eye irritant. May explode on contact with sodium. When heated to decomposition it emits toxic fumes of Cl⁻. See also CHLORINATED HYDROCARBONS, ALIPHATIC.
Analytical Methods:      For occupational chemical analysis use NIOSH: Hexachloro-1,3-cyclopentadiene, 2518.
Hazard Codes:
T+: Very toxic
N: Dangerous for the environment
T: Toxic
F: Flammable
Risk Statements about Hexachlorocyclopentadiene (77-47-4):
R11 Highly flammable.
R22 Harmful if swallowed. 
R24 Toxic in contact with skin. 
R26 Very toxic by inhalation.
R23/24/25: Toxic by inhalation, in contact with skin and if swallowed.
R50/53: Very toxic to aquatic organisms, may cause long-term adverse effects in the aquatic environment. 
R52/53: Harmful to aquatic organisms, may cause long-term adverse effects in the aquatic environment.
Safety Statements about Hexachlorocyclopentadiene (77-47-4):
S16 Keep away from sources of ignition.
S23 Do not breathe vapour. 
S25 Avoid contact with eyes.
S39 Wear eye / face protection.
S45 In case of accident or if you feel unwell, seek medical advice immediately (show the label whenever possible.)
S53 Avoid exposure - obtain special instructions before use.
S60 This material and its container must be disposed of as hazardous waste. 
S61 Avoid release to the environment. Refer to special instructions / safety data sheets.
S36/37: Wear suitable protective clothing and gloves.
Attention:
1. Storage: Tightly closed containers. Keep away from heat and water.
2. Handling: All chemicals should be considered hazardous. Avoid direct physical contact. Use appropriate, approved safety equipment. Untrained individuals should not handle this chemical or its container. Handling should occur in a chemical fume hood.

OSHA PEL: TWA 0.01 ppm
ACGIH TLV: TWA 0.01 ppm; Not Classifiable as a Human Carcinogen
DOT Classification:  6.1; Label: Poison

For occupational chemical analysis use NIOSH: Hexachloro-1,3-cyclopentadiene, 2518.

 Hexachlorocyclopentadiene (77-47-4) is an organochlorine compound that is a precursor to several pesticides. This colourless liquid is an inexpensive reactive diene. Many of its derivatives proved to be highly controversial, as studies showed them to be persistent organic pollutants. Collectively, the pesticides derived from hexachlorocyclopentadiene are called the cyclodienes. An estimated 2.7 x 10⁵ tons were produced until 1976, and some are still manufactured.It mainly used for making organochlorine pesticides, adenauer's agent, highway, LvDan and flame retardant plastics. It is prepared by chlorination of cyclopentadiene to give 1,1,2,3,4,5-octachlorocyclopentane, which in a second step undergoes dehydrochlorination:
C₅H₆ + 6 Cl₂ → C₅H₂Cl₈ + 4 HCl
C₅H₂Cl₈ → C₅Cl₆ + 2 HCl