Hexachloroethane (perchloroethane) is an organochlorine compound with the chemical formula C2Cl6. Its structure is Cl3C−CCl3. It is a white or colorless solid at room temperature with a camphor-like odor. It has been used by the military in smoke compositions, such as base-eject smoke munitions (smoke grenades).
History Hexachloroethane was discovered along with ethylene tetrachloride ("protochloride of carbon") 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 (ZnCl2). 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. 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 a 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 International Agency for Research on Cancer classifies it as Group 2B (possibly carcinogenic to humans), and the U.S. National Toxicology Program lists it as reasonably anticipated to be a human carcinogen. The compound is highly toxic to aquatic life and may bioaccumulate in organisms, posing long-term risks to aquatic environments.
References
External links US Government Agency for Toxic Substances and Disease Registry ToxFAQs for Hexachloroethane US CDC NIOSH Pocket Guide to Chemical Hazards Scorecard.org chemical profile Archived 2020-08-05 at the Wayback Machine US EPA Hexachloroethane fact sheet
