Thiophosgene

Thiophosgene
IUPAC name	Thiophosgene
Other names	Thiocarbonylchloride
Identifiers
CAS number	[463-71-8]
RTECS number	XN2450000
Properties
Molecular formula	CSCl2
Molar mass	114.98 g/mol
Appearance	yellow liquid
Density	1.50 g/cm3
Boiling point	70-75 °C
Solubility in water	decomp.
Solubility in other solvents	polar organic solvents rxn with amines, ROH
Refractive index (nD)	1.548
Structure
Molecular shape	planar, sp2, C2v
Hazards
Main hazards	highly toxic
R-phrases	22-23-36/37/38
S-phrases	7-9-36/37-45
Related compounds
Related compounds	COCl2 SCl2 SOCl2
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Thiophosgene is a yellow liquid with the formula CSCl₂. This compound has a trigonal planar geometry. It possesses two reactive C-Cl bonds that allow this reagent to be used in diverse procedures related to organic synthesis.

Synthesis of CSCl₂

CSCl₂ is prepared in a two-step process from carbon disulfide. In the first step, carbon disulfide is chlorinated to give trichloromethanesulfenyl chloride, 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 sulfur monochloride. Reduction of trichloromethanesulfenyl chloride produces thiophosgene:

CCl₃SCl + M → CSCl₂ + MCl₂

Typically, tin is used for the reducing agent M.

Uses of CSCl₂

CSCl₂ is mainly used to prepare compounds with the connectivity CSX₂ where X = OR, NHR. 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.

Safety considerations

CSCl₂ is considered highly toxic.

References

• Dyson, G. M. "Thiophosgene" Organic Syntheses, Coll. Vol. 1, p.506; Vol. 6, p.86.
• Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
• Sharma, S. "Thiophosgene in Organic Synthesis" Synthesis, 1978, pages 804-820.

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