Chemistry:Thiophosgene

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Thiophosgene
Thiophosgene
Thiophosgene
Thiophosgene.png
Names
IUPAC name
Carbonothioyl dichloride
Other names
Thiophosgene; Thiocarbonyl chloride; Carbonothioic dichloride
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
RTECS number
  • XN2450000
UNII
Properties
CSCl
2
Molar mass 114.97 g·mol−1
Appearance Red liquid
Odor Persistent, choking odor
Density 1.50 g/cm3
Boiling point 70 to 75 °C (158 to 167 °F; 343 to 348 K)
Decomposes
Solubility in other solvents Reacts with amines and alcohols, soluble in polar organic solvents
-50.6·10−6 cm3/mol
1.558
Structure
planar, sp2, C2v
Hazards
Main hazards Highly toxic
Flash point 62 °C (144 °F; 335 K)
Related compounds
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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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

CSCl
2
is prepared in a two-step process from carbon disulfide. In the first step, carbon disulfide is chlorinated to give trichloromethanesulfenyl chloride (perchloromethyl mercaptan), CCl
3
SCl
:

CS
2
+ 3 Cl
2
→ CCl
3
SCl + S
2
Cl
2

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:

CCl
3
SCl + M → CSCl
2
+ MCl
2

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

Reactions

CSCl
2
is mainly used to prepare compounds with the connectivity CSX
2
where X = OR, NHR.[4] 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.[5]

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

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.

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]

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. [9]

See also


References

  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. Dyson, G. M. (1926). "Thiophosgene". Organic Syntheses 6: 86. doi:10.15227/orgsyn.006.0086. 
  3. 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. 
  4. Pascual, Roxana Martinez "Thiophosgene" Synlett 2015, vol. 26, pp. 1776-1777.doi:10.1055/s-0034-1380659
  5. Sharma, S. (1978). "Thiophosgene in Organic Synthesis". Synthesis 1978 (11): 803–820. doi:10.1055/s-1978-24896. 
  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. "Thiophosgene". https://pubchem.ncbi.nlm.nih.gov/compound/Thiophosgene. 
  8. "Thiophosgene". https://pubchem.ncbi.nlm.nih.gov/compound/Thiophosgene. 
  9. Cite error: Invalid <ref> tag; no text was provided for refs named {{{1}}}

Further reading