Thiophosgene

Thiophosgene

Thiophosgene

Chemical compound

Thiophosgene is a red liquid with the formula CSCl2. It is a molecule with trigonal planar geometry. There are two reactive C–Cl bonds that allow it to be used in diverse organic syntheses.[1]

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Preparation

CSCl2 is prepared in a two-step process from carbon disulfide. In the first step, carbon disulfide is chlorinated to give trichloromethanesulfenyl chloride (perchloromethyl mercaptan), CCl3SCl:

CS2 + 3 Cl2 → CCl3SCl + S2Cl2

The chlorination must be controlled as excess chlorine converts trichloromethanesulfenyl chloride into carbon tetrachloride. Steam distillation separates the trichloromethanesulfenyl chloride, a rare sulfenyl chloride, and hydrolyzes the disulfur dichloride. Reduction of trichloromethanesulfenyl chloride produces thiophosgene:

CCl3SCl + M → CSCl2 + MCl2

Tin[2] and dihydroanthracene[3] have been used for the reducing agents.

Reactions

CSCl2 is mainly used to prepare compounds with the connectivity CSX2 where X = OR, NHR.[4] Such reactions proceed via intermediate such as CSClX. Under certain conditions, one can convert primary amines into isothiocyanates. CSCl2 also serves as a dienophile to give, after reduction 5-thiacyclohexene derivatives. Thiophosgene is also known as the appropriate reagent in Corey-Winter synthesis for stereospecific conversion of 1,2-diols into alkenes.[5]

It forms a head-to-tail dimer upon irradiation with UV light:[6]

2 CSCl2 → S2(CCl2)2

Unlike thiophosgene monomer, a red liquid, the photodimer, an example of a 1,3-dithietane, is a colourless solid.

Thisphosgene decomposes at 200 °C or above to form carbon disulfide and carbon tetrachloride.[7] It has also been observed decomposing to hydrogen sulfide, hydrogen chloride, and carbonyl sulfide gases via contact with human tissue.[8][failed verification]

Toxicology and safety

CSCl2 is considered highly toxic. Inhalation of the substance can cause irritation of respiratory system, burns, delayed pulmonary edema and death.[9]

See also

References

  1. [1]
    Manchiu D. S. Lay, Mitchell W. Sauerhoff And Donald R. Saunders "Carbon Disulfide" in Ullmann's Encyclopedia Of Industrial Chemistry, 2000, Wiley-VCH, Weinheim. doi:10.1002/14356007.a05_185
  2. [2]
    Dyson, G. M. (1926). "Thiophosgene". Organic Syntheses. 6: 86. doi:10.15227/orgsyn.006.0086.
  3. [3]
    K. T. Potts, C. Sapino (1972). "Thiocarbonyl halides". In S. Patai (ed.). Acyl Halides. PATAI'S Chemistry of Functional Groups. pp. 349–380. doi:10.1002/9780470771273.ch11. ISBN 978-0-470-77127-3.
  4. [4]
    Pascual, Roxana Martinez "Thiophosgene" Synlett 2015, vol. 26, pp. 1776-1777.doi:10.1055/s-0034-1380659
  5. [5]
    Sharma, S. (1978). "Thiophosgene in Organic Synthesis". Synthesis. 1978 (11): 803–820. doi:10.1055/s-1978-24896.
  6. [6]
    B. Krebs H. Beyer (1969). "Die Kristall- und Molekelstruktur des dimeren Thiophosgens". Z. Anorg. Allg. Chem. 365 (3–4): 199–210. doi:10.1002/zaac.19693650315.
  7. [7]
    U.S. Coast Guard, Department of Transportation (1999). CHRIS - Hazardous Chemical Data. Commandant Instruction 16465.12C. Washington, D.C.: U.S. Government Printing Office — via Cameo Chemicals. As cited in "Thiophosgene" PubChem compound record.
  8. [8]
    "Thiophosgene".
  9. [9]
    US National Library of Medicine (2020). Hazardous Substances Databank entry, as summarized on "Thiophosgene" PubChem compound record.

Further reading

  • Holleman, Arnold Frederik; Wiberg, Egon (2001), Wiberg, Nils (ed.), Inorganic Chemistry, translated by Eagleson, Mary; Brewer, William, San Diego/Berlin: Academic Press/De Gruyter, ISBN 0-12-352651-5
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