Chemistry:Thiophosgene
Thiophosgene is a red liquid with the formula CSCl
2. 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]
Preparation
Typically, CSCl
2 is prepared in a two-step process from carbon disulfide. In the first step, carbon disulfide is chlorinated to give trichloromethanesulfenyl chloride (CCl
3SCl), a rare sulfenyl chloride:
- CS
2 + 3 Cl
2 → CCl
3SCl + S
2Cl
2
The chlorination must be controlled as excess chlorine converts trichloromethanesulfenyl chloride into carbon tetrachloride. Steam distillation separates the trichloromethanesulfenyl chloride and hydrolyzes the disulfur dichloride. Reduction of trichloromethanesulfenyl chloride with, e.g., tin[2] or dihydroanthracene[3] produces thiophosgene:
- CCl
3SCl + M → CSCl
2 + MCl
2
An alternative one-step reaction is[4]
- CCl4 + H2S → SCCl2 + 2 HCl
Reactions
CSCl
2 is mainly used to prepare compounds with the connectivity CSX
2 where X = OR, NHR.[5] Such reactions proceed via intermediate such as CSClX. Under certain conditions, one can convert primary amines into isothiocyanates.
CSCl
2 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.[6]
It forms a head-to-tail dimer upon irradiation with UV light:
- 2 CSCl
2 → S
2(CCl
2)
2
Unlike thiophosgene monomer, a red liquid, the photodimer, an example of a 1,3-dithietane, is a colourless solid.[7] Swarts fluorination of the dimer and then cracking is the principal route to thiocarbonyl fluoride.[8]
Thiophosgene decomposes at 200 °C or above to form carbon disulfide and carbon tetrachloride.[9] It has also been observed decomposing to hydrogen sulfide, hydrogen chloride, and carbonyl sulfide gases via contact with human tissue.[10]
Toxicology and safety
CSCl
2 is considered highly toxic. Inhalation of the substance can cause irritation of respiratory system, burns, delayed pulmonary edema and death.[11]
See also
References
- ↑ 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
- ↑ Dyson, G. M. (1926). "Thiophosgene". Organic Syntheses 6: 86. doi:10.15227/orgsyn.006.0086.
- ↑ K. T. Potts, C. Sapino (1972). "Thiocarbonyl halides". in S. Patai. Acyl Halides. PATAI'S Chemistry of Functional Groups. pp. 349–380. doi:10.1002/9780470771273.ch11. ISBN 978-0-470-77127-3.
- ↑ Graham-Otto's Ausführliches Lehrbuch der Chemie (in German; 1881). Germany: Vieweg.
- ↑ Pascual, Roxana Martinez "Thiophosgene" Synlett 2015, vol. 26, pp. 1776-1777.doi:10.1055/s-0034-1380659
- ↑ Sharma, S. (1978). "Thiophosgene in Organic Synthesis". Synthesis 1978 (11): 803–820. doi:10.1055/s-1978-24896.
- ↑ 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.
- ↑ Potts, K. T.; Sapino, C. (1972). "Thiocarbonyl halides". in Patai, Saul. The Chemistry of Acyl Halides. The Chemistry of Functional Groups. Wiley. pp. 354–355. doi:10.1002/9780470771273.ch11. ISBN 978-0-471-66936-4.
- ↑ 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.
- ↑ "Thiophosgene". https://pubchem.ncbi.nlm.nih.gov/compound/Thiophosgene.
- ↑ 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, San Diego/Berlin: Academic Press/De Gruyter, ISBN 0-12-352651-5
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