Hexachlorobutadiene
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IUPAC name
Hexachloro-1,3-butadiene
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| Other names
HCBD, HCDB, Perchlorobutadiene, perchloro-1,3-butadiene, tripen
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| Identifiers | |
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3D model (Jmol)
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| ChemSpider | |
| ECHA InfoCard | 100.001.605 |
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PubChem CID
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| Properties | |
| C4Cl6 | |
| Molar mass | 260.76 g/mol |
| Appearance | Colorless liquid |
| Odor | Mild, turpentine-like |
| Density | 1.665 g/mL at 25 ℃ |
| Melting point | -22 - -19 ℃ |
| Boiling point | 210-220 ℃ |
| Vapor pressure | 0.2 mmHg (20°C) |
| Hazards | |
| Main hazards | carcinogen |
| Safety data sheet | Sigma Aldrich |
| US health exposure limits (NIOSH): | |
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PEL (Permissible)
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none |
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REL (Recommended)
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Ca TWA 0.02 ppm (0.24 mg/m3) [skin] |
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IDLH (Immediate danger)
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Ca [N.D.] |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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 (what is   ?) |
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| Infobox references | |
Hexachlorobutadiene, Cl2C=C(Cl)C(Cl)=CCl2, is a colorless liquid at room temperature that has an odor similar to that of turpentine. It is a chlorinated aliphatic diene with niche applications but is most commonly used as a solvent for other chlorine-containing compounds.
Hexachlorobutadiene, or HCBD, is primarily produced in chlorinolysis plants as a by-product in the production of carbon tetrachloride and tetrachloroethene. Chlorinolysis is a radical chain reaction that occurs when hydrocarbons are exposed to chlorine gas under pyrolytic conditions. The hydrocarbon is chlorinated and the resulting chlorocarbons are broken down. This process is analogous to combustion, but with chlorine instead of oxygen.
Hexachlorobutadiene occurs as a by-product during the chlorinolysis of butane derivatives in the production of both carbon tetrachloride and tetrachloroethene. These two commodities are manufactured on such a large scale, that enough HCBD can generally be obtained to meet the industrial demand. Alternatively, hexachlorobutadiene can be directly synthesized via the chlorination of butane or butadiene.
The products of chlorinolysis reactions heavily depend upon both the temperature and pressure under which the reaction occurs. Thus, by adjusting these reaction conditions in the presence of chlorine gas, hexachlorobutadiene can be even further chlorinated to give tetrachloroethylene, hexachloroethane, octachlorobutene, and even decachlorobutane. In general, increasing the number of chlorine substituents on a compound increases its toxicity but decreases its combustibility. Chlorination via carbon skeleton cleavage is thermodynamically preferred, whereas chlorinated C4 products are favored at lower temperatures and pressures. The three chlorinolysis products of hexachlorobutadiene are shown in the reactions below.
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