Hexachloroethane

History

Hexachloroethane was discovered along with carbon tetrachloride by Michael Faraday in 1820. Faraday obtained it by chlorinating ethylene. He named it "perchloride of carbon". Faustino Malaguti obtained hexachloroethane by exposing a mixture of tetrachloroethylene and chlorine to sunlight. He termed it "chloride of chlorethose" as it was produced by the chlorination of tetrachloroethylene (then known as "chlorethose").

Manufacture

Chlorination of tetrachloroethylene at 100–140 °C with the presence of iron(III) chloride is the most commonly used commercial production method, however several other methods exist. A high purity form can be produced in a small scale by reacting chlorine together with barium carbide. In September 1997, it was reported as no longer being produced in the United States for commercial distribution, but was produced as a by-product of industrial chlorination process. :

Applications

Hexachloroethane has been used in the formulation of extreme pressure lubricants. It has also been used as a chain transfer agent in the emulsion polymerization of propylene–tetrafluoroethylene copolymer. Hexachloroethane has been used as an anthelmintic in veterinary medicine (under the tradename Avlothane), a rubber accelerator, a component of fungicidal and insecticidal formulations as well as a moth repellant and a plasticizer for cellulose esters.

Hexachloroethane has been used in the manufacture of degassing pellets to remove hydrogen gas bubbles from molten aluminum in aluminum foundries. This use, as well as similar uses in magnesium, is being phased out in the European Union.

Use as smoke agent

Smoke grenades, called hexachloroethane smoke or HC smoke, utilize a mixture containing roughly equal parts of hexachloroethane and zinc oxide and approximately 6% granular aluminium. These smokes are toxic, which is attributed to the production of zinc chloride (). According to Steinritz et al., “Due to its potential pulmonary toxicity,” zinc chloride producing smoke grenades “have been discharged from the armory of most western countries (…).” HC smoke inhalation can cause severe acute respiratory distress syndrome, and one study found that it can cause permanent liver damage. The chemical is a suspected carcinogen, has effects on the nervous system, and can cause sudden collapse and death at high doses. The United States Naval Academy considers it a chemical weapon. It is also considered a "Type 2" pulmonary agent and a lung-damaging agent.

In 2020, US federal agents in Portland, Oregon used canisters of HC gas against protestors.

Toxicity

Hexachloroethane has relatively low acute oral toxicity, with an median lethal dose (LD50) greater than 5000 mg/kg in rats, but is readily absorbed through the skin. The primary effect of exposure is depression of the central nervous system. Acute inhalation exposure may cause coughing and breathing difficulty, with toxic effects potentially delayed up to 24 hours. Occupational exposure limits are typically set at 1 ppm (10 mg/m³) as an 8-hour time-weighted average, with skin notations in the United States, Canada, and international guidelines indicating that dermal absorption contributes significantly to overall exposure. The concentration immediately dangerous to life or health is 300 ppm.

Hexachloroethane is suspected of causing cancer and may cause organ damage through prolonged or repeated exposure. The compound is highly toxic to aquatic life and may bioaccumulate in organisms, posing long-term risks to aquatic environments.

References

References

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