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Dichloroacetylene

Dichloroacetylene
Structure of dichloroacetylene
Names
IUPAC name
Dichloroethyne
Other names
DCA, dichloroethyne
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.149.197
RTECS number
  • AP1080000
Properties
C2Cl2
Molar mass 94.927[1]
Appearance colorless oily liquid[1]
Odor disagreeable, sweetish
Density 1.26 g/cm3
Melting point −66 to −64 °C (−87 to −83 °F; 207 to 209 K)
Boiling point 33 °C (91 °F; 306 K) explodes
insoluble
Solubility soluble in acetone, ethanol, ether
Hazards
Main hazards explosive, potential carcinogen[1]
US health exposure limits (NIOSH):
PEL (Permissible)
none[1]
REL (Recommended)
Ca C 0.1 ppm (0.4 mg/m3)[1]
IDLH (Immediate danger)
Ca (N.D.)[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Dichloroacetylene (DCA[2]) is an oily pyrophoric[3] liquid chemical compound with the chemical formula C2Cl2. Its odor is sweet and "disagreeable".[4] The compound is volatile at standard temperature and pressure and explodes on contact with air.[3][5] It is a toxic compound. It displays nephrotoxic effects to rats, but not to humans. It can be made from the compound trichloroethylene. Dichloroacetylene is not soluble in water.

Properties

Dichloroacetylene explodes upon reaching its boiling point of 33° Celsius (91.4° Fahrenheit).[5] However, it is insoluble in water.[6] Dichloroacetylene can explode when heated or upon contact with air. It also engages in vigorous reaction with materials that are oxidizers.[5] It also engages in violent reactions with acids.[6] Dichloroacetylene is an oil at standard temperature and pressure.[7] It has a density of 1.2 times that of water while in its liquid state and 3.3 times that of air while in its gaseous state.[6]

Dichloroacetylene can detonate if it is set on fire in an enclosed space.[6] It can also burn in the presence of chlorine to produce phosgene.[8]

The stability of dichloroacetylene increases in the presence of large amounts of trichloroethylene.[9]

A mixture of dichloroacetylene with ether forms an azeotrope. This azeotrope has a boiling point of 32° Celsius. Additionally, when dichloroacetylene is mixed with ether, the likelihood of it exploding is reduced.[3]

Unlike the related acetylenes, dichloroacetylene does not readily polymerize. Polydichloroacetylene is however claimed as a white solid.[3]

Occurrence, production and applications

Dichloroacetylene is not produced commercially. However, a 1980 report claimed that it is produced as a by-product in the production process of vinylidene chloride. The compound is also possible to produce by pyrolysis of some types of chlorohydrocarbons.[5] For instance, it can be formed from trichloroethylene.[10] This primarily occurs in the presence of bases with pHs between 11 and 13.[11] It is also possible to produce dichloroacetylene from trichloroethylene at low concentrations by running the trichloroethylene through nitrogen at 120° Celsius in the presence of dry potassium hydroxide.[2] Despite the existing methods of production, there are no known commercial applications for dichloroacetylene.[5]

Additionally, there is another method of producing dichloroacetylene. This method produces high-purity dichloroacetylene in gram amounts. This method involves the pyrolysis of dichloromaleic anhydride at a temperature of 850° Celsius. Dichloroacetylene produced via this method does not need to be separated from any solvents.[3]

Dichloroacetylene can be produced with 82% purity by the pyrolysis of difluoromaleic anhydride at a temperature of 950° Celsius. It is the haloacetylene produced in the highest amounts by this reaction.[3]

Dichloroacetylene can occur and be stable in air at concentrations of up to 200 parts per million if certain other compounds are also present.[12]

Biological role and toxicity

Dichloroacetylene has a toxic effect on humans who are exposed to it. The most common effect that the compound has on humans is the development of neurological disorders. These disorders can persist for any amount of time between a number of days and a number of years.[5] Exposure to the chemical can also cause a large range of other symptoms, including a headache, vomiting and nausea, jaw pain, cranial nerve palsy, appetite loss, and acute lung edema.[13][14] Dichloroacetylene's level of carcinogenity in humans is not classifiable, although there are small amounts of evidence that suggest that the chemical is carcinogenic in animals.[5]

Studies on male rats and rabbits have shown that inhalation of dichloroacetylene can cause tubular necrosis, focal necrosis, and other nephrotoxic effects. Additionally, the rabbits that were given dichloroacetylene experienced hepatotoxic and neuropathological effects. Inhalation of dichloroacetylene also causes benign tumors of the livers and kidneys of rats. The chemical also caused increased incidences of lymphomas.[5] It also causes weight loss in animals.[13] 3.5% of a dose of dichloroacetylene remains in the corpses of male Wistar rats.[5] The LD50s of mice exposed to dichloroacetylene are 124 parts per million for a 1-hour exposure by inhalation and 19 parts per million for a 6-hour exposure by inhalation.[2] The chemical is ingested primarily through glutathione-dependent systems. Glutathione also reacts with it. Hepatitic and renal glutathione S-transferases serve as catalysts to this reaction. While dichloroacetylene is nephrotoxic in rats, it does not show any signs of nephrotoxicity in humans.[9]

Dichloroacetylene has mutagenic effects on Salmonella typhimurium.[5]

The maximum safe concentration of dichloroacetylene in air is 0.1 parts per million.[7] It is unsafe to store dichloroacetylene in close proximity to potassium, sodium, or aluminum powder.[4]

Like trichloroethylene, dichloroacetylene is metabolized to DCVC in vivo.[15]

History

Dichloroacetylene was first synthesized in 1930. It has been characterized by IR and mass spectrometry. However, there is no reported nuclear magnetic resonance data pertaining to it as of 1999.[3]

According to the Department of Transportation, it is forbidden to ship dichloroacetylene.[4]

See also

References

  1. ^ a b c d e f NIOSH Pocket Guide to Chemical Hazards. "#0188". National Institute for Occupational Safety and Health (NIOSH).
  2. ^ a b c Reichert, D.; Ewald, D.; Henschler, D. (1975), "Generation and inhalation toxicity of dichloroacetylene", Food and Cosmetics Toxicology, 13 (5): 511–5, doi:10.1016/0015-6264(75)90004-8, PMID 1201833
  3. ^ a b c d e f g Trifu, Roxana Melita (1999), "Dichloroacetylene", Homopolymers of Dihaloacetylenes (Ph.D. Thesis), p. 57, Bibcode:1999PhDT.......149T, ISBN 978-0-549-39503-4
  4. ^ a b c Pohanish, Richard P. (2011), Sittig's Handbook of Toxic and Hazardous Chemicals and Carcinogens, ISBN 9781437778694[page needed]
  5. ^ a b c d e f g h i j "Dichloroacetylene" (PDF), IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans, 39: 369–78, 1986, PMID 3465694
  6. ^ a b c d Dichloroacetylene, International Programme on Chemical Safety, October 17, 2001
  7. ^ a b Hazardous Material Fact Sheet (PDF), April 1997, retrieved 2013 Check date values in: |accessdate= (help)
  8. ^ Chemical Datasheet: Dichloroacetylene, retrieved 2013 Check date values in: |accessdate= (help)
  9. ^ a b Valacchi, Giuseppe; Davis, Paul A., eds. (January 1, 2008), Oxidants in Biology: A Question of Balance, Springer Science+Business Media, ISBN 9781402083990[page needed]
  10. ^ John T. James; Harold L. Kaplan; Martin E. Coleman (1996), B5 Dichloroacetylene, retrieved 2013 Check date values in: |accessdate= (help)
  11. ^ Greim, H; Wolff, T; Höfler, M; Lahaniatis, E (1984), "Formation of dichloroacetylene from trichloroethylene in the presence of alkaline material--possible cause of intoxication after abundant use of chloroethylene-containing solvents", Archives of Toxicology, 56 (2): 74–7, doi:10.1007/bf00349074, PMID 6532380
  12. ^ Proceedings, Aerospace Medical Research Laboratory, 1966[page needed]
  13. ^ a b Dichloroacetylene, November 18, 2010, retrieved 2013 Check date values in: |accessdate= (help)
  14. ^ Dichloroacetylene, retrieved 2013 Check date values in: |accessdate= (help)
  15. ^ Purich, Daniel L., ed. (September 15, 2009), Advances in Enzymology and Related Areas of Molecular Biology, Amino Acid Metabolism, ISBN 9780470123973[page needed]