Hexachloroethane

Hexachloroethane (perchloroethane) is an organochlorine compound with the chemical formula (CCl3)2. It is a white or colorless solid at room temperature with a camphor-like odor.[3] It has been used by the military in smoke compositions, such as base-eject smoke munitions (smoke grenades).

Hexachloroethane
Names
Preferred IUPAC name
Hexachloroethane
Other names
Carbon hexachloride, Ethane hexachloride, Perchloroethane
Identifiers
3D model (JSmol)
1740341
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.000.606
EC Number
  • 200-666-4
26648
KEGG
UNII
  • InChI=1S/C2Cl6/c3-1(4,5)2(6,7)8 checkY
    Key: VHHHONWQHHHLTI-UHFFFAOYSA-N checkY
  • InChI=1/C2Cl6/c3-1(4,5)2(6,7)8
    Key: VHHHONWQHHHLTI-UHFFFAOYAD
  • ClC(Cl)(Cl)C(Cl)(Cl)Cl
Properties
C2Cl6
Molar mass 236.74 g/mol
Appearance colorless crystals[1]
Odor camphor-like[1]
Density 2.091 g/mL at 25 °C
Melting point sublimes
Boiling point 183 to 185 °C (361 to 365 °F; 456 to 458 K)
0.005% (22.2 °C)[1]
Vapor pressure 0.2 mmHg (20 °C)[1]
-112.7·10−6 cm3/mol
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 Probable carcinogen, dangerous CNS depressant
NFPA 704 (fire diamond)
NFPA 704 four-colored diamond
2
0
0
Flash point noncombustible[1]
Lethal dose or concentration (LD, LC):
4460 mg/kg (rat, oral)
4970 mg/kg (guinea pig, oral)

[2]

NIOSH (US health exposure limits):
PEL (Permissible)
 TWA 1 ppm (10 mg/m3) [skin][1]
REL (Recommended)
 Ca TWA 1 ppm (10 mg/m3) [skin][1]
IDLH (Immediate danger)
 Ca [300 ppm][1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)
Infobox references

Manufacture

Chlorination of tetrachloroethylene at 100–140 °C with the presence of ferric 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.[4]: 101  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.[4]: 101 

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, a rubber accelerator, a component of fungicidal and insecticidal formulations as well as a moth repellant and a plasticizer for cellulose esters.[3]

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.[5]

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).[6][7] 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 (...)."[8]

Use as a riot control agent

HC smoke grenades, often used as smoke agents in combat, were used against protesters in Portland by Federal Protective Services and the Department of Homeland Security in Portland, Oregon during protests against police brutality. HC smoke began to be used more often by federal forces during Operation Diligent Valor. Despite numerous smoke canisters labeled "HC" being photographed by journalists and unusual levels of zinc and chloride, the two dominant combustion elements in HC smoke canisters, being found at protest locations, Rob Sperling, communications director for the Federal Protective Services denied the use of HC, claiming, "FPS doesn't have any items that contain HC."[9] The Portland Bureau of Environmental Services requested safety data sheets from FPS regarding the use of HC smoke. The request was denied.[9] While HC smoke has been most extensively used by FPS in Portland, OR during 2020-21 protests, police departments in other American cities, such as Milwaukee, Wi and Denver, CO have also purchased HC smoke canisters.[10] Most documented uses of HC smoke as a riot control agent occurred in the United States, with little being known about its use by other governments.

Health effects

Many protesters reported vomiting and a continued loss of appetite when exposed to the toxic smoke. Some have also reported changes in menstrual cycles. Despite its continued use by FPS as a riot control agent, the Department of Defense has begun to phase out the use of HC smoke after a 1994 report by the U.S. Army Biomedical Research and Development Laboratory due to ensure the safety of US soldiers, noting that, "Exposure of unprotected soldiers to high concentrations of HC smoke for even a few minutes has resulted in injuries and fatalities."[11]

Toxicity

Hexachloroethane is not particularly toxic when taken orally,[12] but is considered to be quite toxic by skin adsorption. The primary effect is depression of the central nervous system.[3] The concentration that is immediately dangerous to life or health is 300 ppm and the permissible exposure limit according to the Occupational Safety and Health Administration is 1 ppm (skin).[12] It is reasonably anticipated to be a carcinogen.[13]

References
  1. NIOSH Pocket Guide to Chemical Hazards. "#0316". National Institute for Occupational Safety and Health (NIOSH).
  2. "Hexachloroethane". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  3. Snedecor, Gayle (1999). "Hexachloroethane". In Kroschwitz, Jacqueline I. (ed.). Kirk-Othmer Concise Encyclopedia of Chemical Technology (4th ed.). New York: John Wiley & Sons, Inc. p. 428. ISBN 978-0471419617.
  4. "Hexachloroethane 101" (PDF). September 1997.
  5. ECHA, Annex XVII to REACH – Conditions of restriction, Restrictions on the manufacture, placing on the market and use of certain dangerous substances, mixtures and articles, entry 41: hexachloroethane
  6. "Appendix E: Smoke And Masking Agents" (PDF). Australian Department of Veteran Affairs. December 2003. p. E-3. Archived from the original (PDF) on 2014-02-13. Retrieved 2012-10-04.
  7. National Research Council (1997). Toxicity of Military Smokes and Obscurants, volume 1. Subcommittee on Military Smokes and Obscurants. Washington, DC: National Academy Press. p. 127
  8. Steinritz, D., Zehfuß, F., Stenger, B., Schmidt, A., Popp, T., Kehe, K., Mückter, H., Thiermann, H., Gudermann, T. (2018). Zinc chloride-induced TRPA1 activation does not contribute to toxicity in vitro. Toxicology Letters, 293, 133–139. doi:10.1016/j.toxlet.2017.09.008
  9. "Military-grade HC smoke used against Portland protesters". KOIN.com. 2020-10-20. Retrieved 2021-06-16.
  10. "Police deployed potentially lethal chemical during Black Lives Matter protests". Salon. 2021-02-21. Retrieved 2021-06-16.
  11. Lerner, Sharon (October 10, 2020). "Toxic Chemical Smoke Grenades Used in Portland". The Intercept. Retrieved 2021-06-16.
  12. "Documentation for Immediately Dangerous To Life or Health Concentrations (IDLHs) Hexachloroethane". NIOSH. May 1994. Retrieved 2012-10-04.
  13. "Report on Carcinogens, Twelfth Edition, Hexachloroethane" (PDF). NIH. 2011. Retrieved 2012-10-04.
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