Dichloroacetylene

Dichloroacetylene (DCA) is an organochlorine compound with the formula C
2Cl
2.[1] It is a colorless, pyrophoric, explosive liquid that has a sweet and "disagreeable" odor.[2] Dichloroacetylene is neurotoxic, hepatotoxic, nephrotoxic and possibly carcinogenic.[3]

## Contents

* 1 History and production
* 1.1 Adventitious routes
* 2 Stability
* 3 Reactions
* 4 Biological role and toxicity
* 5 Additional reading
* 6 See also
* 7 References

## History and production

Dichloroacetylene was first synthesized via the thermal decarboxylation of barium trichloroacrylate by Jacob Böeseken (de) and J. F. Carriére in 1914:[4][5]

Ba(Cl
2C=C(Cl)COO)
2 → BaCl
2 \+ ClC≡CCl + 2CO

Dichloroacetylene was discovered as an intermediate in the synthesis of diphenylacetylene with calcium carbide, chlorine and benzene in 1918.[6] It was first synthesized from trichloroethylene by Erwin Ott (de), W. Ottemeyer and K. Packendorff in 1930.[1]

Ether solutions of up to 50 mol% dichloroacetylene are relatively stable, and such solutions can be safely generated by the dehydrochlorination of trichloroethylene. A popular procedure uses potassium hydride as the base:[7][8]

2C=CHCl + KH → ClC≡CCl + KCl + H

A trace of methanol is required.

It has also been generated (and used in situ) using lithium diisopropylamide under anhydrous conditions[9] as well as potassium hydroxide.[10]

### Adventitious routes

It is a by-product in the production of vinylidene chloride.[11] For instance, it can be formed from trichloroethylene.[12][13] It is also possible to produce dichloroacetylene from trichloroethylene at low concentrations by running the trichloroethylene through nitrogen at 120 °C in the presence of dry potassium hydroxide.[14]

## Stability

Pure dichloroacetylene is explosive, igniting or detonating spontaneously upon contact with air.[15] Products of this reaction include phosgene, carbon monoxide, and carbon dioxide:[15][14]

ClC≡CCl + O
2 → Cl
2C=O + CO

When heated to 130 °C in the absence of air, it explosively decomposes to the elements:[4]: 330, 336

ClC≡CCl → 2C + Cl

Dichloroacetylene has been reported to trimerize to hexachlorobenzene upon heating, as well as perhaps on exposure to light.[15]: 705 [4]: 334 While it does not undergo heat-induced polymerization, molybdenum pentachloride catalyzes its room-temperature polymerization to cis-polydichloroacetylene.[16]

Like other haloalkynes, dichloroacetylene is a strong halogen bond donor.[17] It forms an air-stable azeotrope with ether, boiling at 32 °C, that contains 55.4 wt% DCA, corresponding to a 1:1 molar ratio.[15][18]

Stabilizers such as trichloroethylene can support dichloroacetylene concentrations of up to 200 parts per million in air without significant decomposition.[3][19]

## Reactions

Dichloroacetylene, being electrophilic, adds nucleophiles, such as amines:[8]: 356

ClC≡CCl + R
2NH → Cl(H)C=CCl(NR

It forms pi-complexes with tungsten, such as [WCl
5(C
2Cl
2)]−
.[20]

## Biological role and toxicity

Dichloroacetylene causes severe neurological disorders,[11] among other problems.[21][22] Main route of human exposure to dichloroacetylene has been the breakdown of trichloroethylene in presence of alkali hydroxides, historically during trichloroethylene anaesthesia when soda lime was used. Humans exposed to dichloroacetylene showed symptoms such as nausea, vomiting, loss of appetite, headache, facial nervous and muscular issues, and formation of herpes-like lesions on the face. Some people reported itching around the eyes and pain around the jaw. It affects the trigeminal nerve in particular and over-exposure could be fatal.[19]

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 instances of lymphomas.[11] It also causes weight loss in animals.[21] 3.5% of a dose of dichloroacetylene remains in the corpses of male Wistar rats.[11] The LC50s 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.[14] The chemical is ingested primarily through glutathione-dependent systems. Glutathione also reacts with it. Hepatic and renal glutathione S-transferases serve as catalysts to this reaction. While dichloroacetylene is nephrotoxic in rats, its nephrotoxicity in humans is not well-understood.[3][2]

Dichloroacetylene has mutagenic effects on Salmonella typhimurium.[11]

Like trichloroethylene, dichloroacetylene is metabolized to S-(1,2-dichlorovinyl)-L-cysteine (DCVC) in vivo.[23][24]

The maximum safe concentration of dichloroacetylene in air is 0.1 parts per million.[25] It is unsafe to store dichloroacetylene in close proximity to potassium, sodium, or aluminium powder. According to the Department of Transportation, it is forbidden to ship dichloroacetylene.[2]

## Additional reading

* Trifu, Roxana Melita (1999), "Dichloroacetylene", Homopolymers of Dihaloacetylenes, p. 57, ISBN 978-0-549-39503-4, Bibcode: 1999PhDT.......149T, https://books.google.com/books?id=7VD8eUGZn-gC&pg=PA57

## See also

* Dibromoacetylene
* Difluoroacetylene
* Diiodoacetylene
* Organochloride

## References

1. ↑ 1.0 1.1 Henning Hopf; Bernhard Witulski (1995). "Functionalized Acetylenes in Organic Synthesis - The Case of the 1-Cyano- and the 1-Halogenoacetylenes". in Stang, Peter J.. Modern Acetylene Chemistry. Weinheim: VCH. pp. 33–66. doi:10.1002/9783527615278.ch02. ISBN 9783527615261.
2. ↑ 2.0 2.1 2.2 Pohanish, Richard P. (2011), Sittig's Handbook of Toxic and Hazardous Chemicals and Carcinogens, William Andrew, pp. 908-910, ISBN 9781437778694, https://books.google.com/books?id=f6HclgoIkjcC&q=Dichloroacetylene&pg=PA910
3. ↑ 3.0 3.1 3.2 Valacchi, Giuseppe; Davis, Paul A., eds. (January 1, 2008), Oxidants in Biology: A Question of Balance, Springer Science+Business Media, pp. 217–218, ISBN 9781402083990, https://books.google.com/books?id=ghnUBsij2vEC&q=Dichloroacetylene&pg=PA217
4. ↑ 4.0 4.1 4.2 Smirnov, K M; Tomilov, Andrei P; Shchekotikhin, A I (31 May 1967). "Haloacetylenes". Russian Chemical Reviews 36 (5): 326–338. doi:10.1070/RC1967v036n05ABEH001627. https://www.russchemrev.org/RCR1627pdf.
5. ↑ Böeseken, J.; Carriére, J. F. (1914). "Over het dichlooracetyleen (tevens een waarschuwing)". Versl. Wis. Nat. Afd. K. Akad. Wet. (Amsterdam) 22: 1186–1188. https://archive.org/details/verslagvandegew2221914_2/page/1186/mode/2up?q="dichlooracetyleen".
6. ↑ Clinton Davidson: Tolane chlorides from calcium carbide, chlorine and benzene. In: Journal of the American Chemical Society. 40, Nr. 2, 1918, S. 397–400, doi:10.1021/ja02235a009.
7. ↑ Denis, Jean Noel; Moyano, Albert; Greene, Andrew E. (1987). "Practical synthesis of dichloroacetylene". The Journal of Organic Chemistry 52 (15): 3461–3462. doi:10.1021/jo00391a059.
8. ↑ 8.0 8.1 "Bis[heteroatom-functionalized Acetylenes (Update 2014)"]. Science of Synthesis Knowledge Updates: Houben-Weyl methods of molecular transformations. 2014/3. Stuttgart: Thieme. 11 June 2014. p. 354. ISBN 978-3-13-176281-8. https://archive.org/details/scienceofsynthes0003unse/page/354/mode/2up?q=dichloroacetylene.
9. ↑ "Dichlorovinylation of an Enolate: 8-Ethynyl-8-Methyl-1,4-Dioxaspiro[4.5]Dec-6-Ene". Organic Syntheses 64: 73. 1986. doi:10.15227/orgsyn.064.0073.
10. ↑ Siegel, J.; Jones, Richard Arvin.; Kurlansik, L. (1970). "Safe and Convenient Synthesis of Dichloroacetylene". The Journal of Organic Chemistry 35 (9): 3199. doi:10.1021/jo00834a090.
11. ↑ 11.0 11.1 11.2 11.3 11.4 "Dichloroacetylene", IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans 39: 369–78, 1986, PMID 3465694, http://monographs.iarc.fr/ENG/Monographs/vol71/mono71-88.pdf
12. ↑ John T. James; Harold L. Kaplan; Martin E. Coleman (1996), B5 Dichloroacetylene, doi:10.17226/5435, ISBN 978-0-309-05629-8, http://www.nap.edu/openbook.php?record_id=5435&page=117, retrieved July 3, 2013
13. ↑ 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, Bibcode: 1984ArTox..56...74G
14. ↑ 14.0 14.1 14.2 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
15. ↑ 15.0 15.1 15.2 15.3 "1-Halogenoacetylenes". Chemistry of Acetylenes. 1969. pp. 674–675. ISBN 9780783709321. https://archive.org/details/chemistryofacety0000vieh/page/674/mode/2up?q=dichloroacetylene.
16. ↑ Gould, George L.; Eswara, Veena; Trifu, Roxana M.; Castner, David G. (1 April 1999). "Polydifluoroacetylene, Polychlorofluoroacetylene, and Polydichloroacetylene". Journal of the American Chemical Society 121 (15): 3781–3782. doi:10.1021/ja983840a.
17. ↑ Cavallo, Gabriella; Metrangolo, Pierangelo; Milani, Roberto; Pilati, Tullio; Priimagi, Arri; Resnati, Giuseppe; Terraneo, Giancarlo (24 February 2016). "The Halogen Bond". Chemical Reviews 116 (4): 2478–2601. doi:10.1021/acs.chemrev.5b00484.
18. ↑ Ott, Erwin; Packendorff, Kurt (10 June 1931). "Über das Dichloracetylen (II.) und den Einfluß der Reaktionsgeschwindigkeit auf den stereochemischen Verlauf der Halogen‐Addition an die Acetylen‐Bindung". Chem. Ber. 64 (6): 1324–1329. doi:10.1002/cber.19310640619. "Diese Molekülverbindung ist zwar vollig unempfindlich gegen Sauerstoff, sie ist aber locker, besitzt den charakteristischen Geruch beider Komponenten und zerfällt beim Mischen mit Wasser, in dem sich der Äther sehr viel leichter löst und sich das nunmehr abgeschiedene Dichlor-acetylen entzündet.".
19. ↑ 19.0 19.1 ﻿Proceedings of the 2nd Annual Conference on Atmospheric Contamination in Confined Spaces, 4 and 5 May 1966﻿ (Report). Aerospace Medical Research Laboratory. December 1966. pp. 55–56.
20. ↑ Stahl, Karlheinz; Weller, Frank; Dehnicke, Kurt (1986). "Dichloracetylen als stabiler Komplexligand die Kristallstruktur von PPh4[WCL5(C2Cl2)] · 0,5 CCL4". Zeitschrift für Anorganische und Allgemeine Chemie 533 (2): 73–82. doi:10.1002/zaac.19865330210.
21. ↑ 21.0 21.1 Cite error: Invalid `<ref>` tag; no text was provided for refs named `PGCH`
22. ↑ Dichloroacetylene, http://www.osha.gov/dts/chemicalsampling/data/CH_232700.html, retrieved July 3, 2013
23. ↑ Purich, Daniel L., ed. (September 15, 2009), Advances in Enzymology and Related Areas of Molecular Biology, Amino Acid Metabolism, John Wiley & Sons, ISBN 9780470123973, https://books.google.com/books?id=xHIPCjTrOhYC&q=Dichloroacetylene&pg=PA212
24. ↑ Kanhai, Wolfgang; Dekant, Wolfgang; Henschler, Dietrich (January 1989). "Metabolism of the nephrotoxin dichloroacetylene by glutathione conjugation". Chemical Research in Toxicology 2 (1): 51–56. doi:10.1021/tx00007a009. ISSN 0893-228X. PMID 2519231.
25. ↑ Hazardous Material Fact Sheet, April 1997, http://nj.gov/health/eoh/rtkweb/documents/fs/0640.pdf, retrieved July 4, 2013

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