Sulfur dichloride

Sulfur dichloride

Names
IUPAC name Dichlorosulfane Sulfur dichloride Sulfur(II) chloride
Other names Chloro thiohypobromite Dichloro sulfide Sulphur chloride
Identifiers
CAS Number	10545-99-0 Y
3D model (JSmol)	Interactive image
ChemSpider	23682
ECHA InfoCard	100.031.014
EC Number	234-129-0
PubChem CID	25353
RTECS number	WS4500000
UNII	8Q6684WQ9H Y
UN number	1828
CompTox Dashboard (EPA)	DTXSID4051538
InChI InChI=1S/Cl2S/c1-3-2 Key: FWMUJAIKEJWSSY-UHFFFAOYSA-N InChI=1/Cl2S/c1-3-2 Key: FWMUJAIKEJWSSY-UHFFFAOYAS
SMILES ClSCl
Properties
Chemical formula	SCl2
Molar mass	102.96 g·mol−1
Appearance	Cherry-red liquid
Odor	Pungent
Density	1.621 g/cm3
Melting point	−121.0 °C (−185.8 °F; 152.2 K)
Boiling point	59 °C (138 °F; 332 K) (decomposes)
Solubility in water	Insoluble, reacts slowly
Magnetic susceptibility (χ)	−49.4·10−6 cm3/mol
Refractive index (nD)	1.5570
Structure
Coordination geometry	C2v
Molecular shape	Bent
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H314, H335, H400
Precautionary statements	P260, P261, P264, P271, P273, P280, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P310, P312, P321, P363, P391, P403+P233, P405, P501
NFPA 704 (fire diamond)	3 1 1
Autoignition temperature	234 °C (453 °F; 507 K)
Safety data sheet (SDS)	ICSC 1661
Related compounds
Related	Disulfur dichloride Thionyl chloride Sulfuryl chloride
Related compounds	Sulfur difluoride Sulfur tetrafluoride Sulfur hexafluoride Disulfur dibromide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

Sulfur dichloride is the chemical compound with the formula SCl₂. This cherry-red liquid is the simplest sulfur chloride and one of the most common, and it is used as a precursor to organosulfur compounds. It is a highly corrosive and toxic substance, and it reacts on contact with water to form chlorine-containing acids.

Chlorination of sulfur

SCl₂ is produced by the chlorination of either elemental sulfur or disulfur dichloride.^[1] The process occurs in a series of steps, some of which are:

S₈ + 4 Cl₂ → 4 S₂Cl₂; ΔH = −58.2 kJ/mol

S₂Cl₂ + Cl₂ ↔ 2 SCl₂; ΔH = −40.6 kJ/mol

The addition of Cl₂ to S₂Cl₂ has been proposed to proceed via a mixed valence intermediate Cl₃S−SCl. SCl₂ undergoes even further chlorination to give SCl₄, but this species is unstable at near room temperature. It is likely that several S_nCl₂ exist where n > 2.

Disulfur dichloride, S₂Cl₂, is the most common impurity in SCl₂. Separation of SCl₂ from S₂Cl₂ is possible via distillation with PCl₃ to form an azeotrope of 99% purity, however sulfur dichloride loses chlorine slowly at room temperature and reverts to disulfur dichloride. Pure samples may be stored in sealed glass ampules which develop a slight positive pressure of chlorine, halting the decomposition.

Use of SCl₂ in chemical synthesis

SCl₂ is used in organic synthesis. It adds to alkenes to give chloride-substituted thioethers. Illustrative is its addition to 1,5-cyclooctadiene to give a bicyclic thioether^[2] A well tested method for the production of the mustard gas bis(2-chloroethyl)sulfide, is the addition of ethylene to sulfur dichloride:^[3]

SCl₂ + 2 C₂H₄ → (ClC₂H₄)₂S

SCl₂ is also a precursor to several inorganic sulfur compounds. Treatment with fluoride salts gives SF₄ via the decomposition of the intermediate sulfur difluoride. With H₂S, SCl₂ reacts to give "lower" sulfanes such as S₃H₂.

Reaction with ammonia affords sulfur nitrides related to S₄N₄. Treatment of SCl₂ with primary amines gives sulfur diimides. One example is di-t-butylsulfurdiimide.^[4]

Safety considerations

SCl₂ hydrolyzes with release of HCl. Old samples contain Cl₂.^{[citation needed]}

References