Chemistry:Thiophosgene

Thiophosgene

Names
IUPAC name Carbonothioyl dichloride
Other names Thiophosgene; Thiocarbonyl chloride; Carbonothioic dichloride
Identifiers
CAS Number	463-71-8 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:29366 Y
ChemSpider	9645 Y
PubChem CID	10040
RTECS number	XN2450000
UNII	067FQP576P Y
InChI InChI=1S/CCl2S/c2-1(3)4 Y Key: ZWZVWGITAAIFPS-UHFFFAOYSA-N Y InChI=1/CCl2S/c2-1(3)4 Key: ZWZVWGITAAIFPS-UHFFFAOYAH
SMILES ClC(Cl)=S
Properties
Chemical formula	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)
Solubility in water	Decomposes
Solubility in other solvents	Reacts with amines and alcohols, soluble in polar organic solvents
Magnetic susceptibility (χ)	-50.6·10−6 cm3/mol
Refractive index (nD)	1.558
Structure
Molecular shape	planar, sp2, C2v
Hazards
Main hazards	Highly toxic
Flash point	62 °C (144 °F; 335 K)
Related compounds
Related compounds	Phosgene Thiocarbonyl fluoride Thiocarbonyl bromide Sulfur dichloride Thionyl chloride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

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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.

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
3SCl:

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, a rare sulfenyl chloride, and hydrolyzes the disulfur dichloride. Reduction of trichloromethanesulfenyl chloride produces thiophosgene:

CCl
3SCl + M → CSCl
2 + MCl
2

Tin and dihydroanthracene 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. 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.

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.

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

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.

See also

• Phosgene
• Carbonyl fluoride
• Sulfur dichloride