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Disulfur dichloride

Sulfur, S  Chlorine, Cl
Names
IUPAC names Disulfur dichloride Dichlorodisulfane
Systematic IUPAC name Chlorosulfanyl thiohypochlorite
Other names Bis(S–S) Dimeric sulfenic chloride Sulfur monochloride (incorrect name)
Identifiers
CAS Number	10025-67-9 85408-26-0 (isobutenate)
3D model (JSmol)	Interactive image
ChemSpider	23192 19158348 (isobutenate)
DrugBank	DB14647
ECHA InfoCard	100.030.021
EC Number	233-036-2
MeSH	Sulfur+monochloride
PubChem CID	24807
RTECS number	WS4300000
UNII	NJ7YR2EV0D
UN number	3390
CompTox Dashboard (EPA)	DTXSID3042427
InChI InChI=1S/Cl2S2/c1-3-4-2Key: PXJJSXABGXMUSU-UHFFFAOYSA-N InChI=1/Cl2S2/c1-3-4-2Key: PXJJSXABGXMUSU-UHFFFAOYAK
SMILES ClSSCl
Properties
Chemical formula	S2Cl2
Molar mass	135.02 g·mol
Appearance	Light-amber to yellow-red, oily liquid
Odor	pungent, nauseating, irritating
Density	1.688 g/cm
Melting point	−80 °C (−112 °F; 193 K)
Boiling point	137.1 °C (278.8 °F; 410.2 K)
Solubility in water	Decomposes, with loss of HCl
Solubility	Soluble in ethanol, benzene, ether, THF, chloroform, CCl4
Vapor pressure	7 mmHg (20 °C)
Magnetic susceptibility (χ)	−62.2·10 cm/mol
Refractive index (nD)	1.658
Structure
Point group	C2
Coordination geometry	2 at sulfur atoms
Molecular shape	gauche
Dipole moment	1.60 D
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H301, H314, H332, H400
Precautionary statements	P260, P261, P264, P270, P271, P273, P280, P301+P310, P301+P330+P331, P303+P361+P353, P304+P312, P304+P340, P305+P351+P338, P310, P312, P321, P330, P363, P391, P405, P501
NFPA 704 (fire diamond)	2 1 1
Flash point	118.5 °C (245.3 °F; 391.6 K)
Autoignition temperature	234 °C (453 °F; 507 K)
Lethal dose or concentration (LD, LC):
LCLo (lowest published)	150 ppm (mouse, 1 min) (1 ppm = 5.52 mg/m)
NIOSH (US health exposure limits):
PEL (Permissible)	TWA 1 ppm (5.52 mg/m)
REL (Recommended)	C 1 ppm (5.52 mg/m)
IDLH (Immediate danger)	5 ppm (1 ppm = 5.52 mg/m)
Safety data sheet (SDS)	ICSC 0958
Related compounds
Related sulfur chlorides/oxychlorides	Sulfur dichloride Thionyl chloride Sulfuryl chloride
Related compounds	Hydrogen disulfide Disulfur difluoride Disulfur dibromide Disulfur diiodide Dimethyl disulfide Diphenyl disulfide Diselenium dichloride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). N verify (what is  ?) Infobox references

Disulfur dichloride (or disulphur dichloride by the British English spelling) is the inorganic compound of sulfur and chlorine with the formula S₂Cl₂. It is an amber oily liquid.

Sometimes, this compound is incorrectly named sulfur monochloride (or sulphur monochloride by the British English spelling), the name implied by its empirical formula SCl.

S₂Cl₂ has the structure implied by the formula Cl−S−S−Cl, wherein the dihedral angle between the Cl−S−S and S−S−Cl planes is 85.2°. This structure is referred to as gauche, and is akin to that for H₂O₂. A rare isomer of S₂Cl₂ is S=SCl₂ (thiothionyl chloride); this isomer forms transiently when S₂Cl₂ is exposed to UV-radiation (see thiosulfoxides).

Synthesis, basic properties, reactions

Disulfur dichloride is a yellow liquid that fumes in moist air due to reaction with water:

16 S₂Cl₂ + 16 H₂O → 8 SO₂ + 32 HCl + 3 S₈

It is produced by partial chlorination of elemental sulfur. The reaction proceeds at usable rates at room temperature. In the laboratory, chlorine gas is led into a flask containing elemental sulfur. As disulfur dichloride is formed, the contents become a golden yellow liquid:

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

Excess chlorine produces sulfur dichloride, which causes the liquid to become less yellow and more orange-red:

S₂Cl₂ + Cl₂ ⇌ 2 SCl₂, ΔH = −40.6 kJ/mol

The reaction is reversible, and upon standing, SCl₂ releases chlorine to revert to the disulfur dichloride. Disulfur dichloride has the ability to dissolve large quantities of sulfur, which reflects in part the formation of polysulfanes:

8 S₂Cl₂ + n S₈ → 8 S_n+2Cl₂

Disulfur dichloride can be purified by distillation from excess elemental sulfur.

S₂Cl₂ also arises from the chlorination of CS₂ as in the synthesis of thiophosgene or carbon tetrachloride.

Reactions

S₂Cl₂ hydrolyzes to sulfur dioxide and elemental sulfur. When treated with hydrogen sulfide, polysulfanes are formed as indicated in the following idealized formula:

2 H₂S + S₂Cl₂ → H₂S₄ + 2 HCl

It reacts with ammonia to give tetrasulfur tetranitride as well as heptasulfur imide (S₇NH) and related S−N rings S_8−n(NH)_n (n = 2, 3).

16 NH₃ + 6 S₂Cl₂ → S₄N₄ + S₈ + 12 NH₄Cl

With primary and secondary alkoxide equivalents, it forms disulfoxylate esters:

2 ROH + S₂Cl₂ + 2 NEt₃ → (R–O–S)₂ + 2 Cl

In principle the subsequent addition of base should give sulfoxylate esters, but typically induces disproportionation to aldehydes and alcohols instead.

Applications

S₂Cl₂ has been used to introduce C−S bonds. In the presence of aluminium chloride (AlCl₃), S₂Cl₂ reacts with benzene to give diphenyl sulfide:

8 S₂Cl₂ + 16 C₆H₆ → 8 (C₆H₅)₂S + 16 HCl + S₈

Anilines (1) react with S₂Cl₂ in the presence of NaOH to give 1,2,3-benzodithiazolium chloride (2) (Herz reaction) which can be transformed into ortho-aminothiophenolates (3), these species are precursors to thioindigo dyes.

It is also used to prepare mustard gas via ethylene at 60 °C (the Levinstein process):

8 S₂Cl₂ + 16 H₂C=CH₂ → 8 (ClCH₂CH₂)₂S + S₈

If the reaction is performed at a temperature under 30 °C, the sulfur stays in "pseudo-solution" and avoids the problems associated with the sulfur that is formed during the reaction.

Other uses of S₂Cl₂ include the manufacture of sulfur dyes, insecticides, and synthetic rubbers. It is also used in cold vulcanization of rubbers, as a polymerization catalyst for vegetable oils and for hardening soft woods.

Safety and regulation

S₂Cl₂ can be used to produce bis(2-chloroethyl)sulfide S(CH₂CH₂Cl)₂, known as the mustard gas:

S₂Cl₂ + 2 H₂C=CH₂ → S(CH₂CH₂Cl)₂ + "S"

Consequently, it is listed in Schedule 3 of the Chemical Weapons Convention. Facilities that produce and/or process and/or consume scheduled chemicals may be subject to control, reporting mechanisms and inspection by the Organisation for the Prohibition of Chemical Weapons.

References

1. ^ NIOSH Pocket Guide to Chemical Hazards. "#0578". National Institute for Occupational Safety and Health (NIOSH).
2. ^ Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0-07-049439-8
3. "Sulfur monochloride". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
4. Holleman, A. F.; Wiberg, E. Inorganic Chemistry Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
5. Hartman, W. W.; Smith, L. A.; Dickey, J. B. (1934). "Diphenylsulfide". Organic Syntheses. 14: 36; Collected Volumes, vol. 2, p. 242.
6. R. J. Cremlyn An Introduction to Organosulfur Chemistry John Wiley and Sons: Chichester (1996). ISBN 0-471-95512-4
7. Garcia-Valverde M., Torroba T. (2006). "Heterocyclic chemistry of sulfur chlorides – Fast ways to complex heterocycles". European Journal of Organic Chemistry. 2006 (4): 849–861. doi:10.1002/ejoc.200500786.
8. F. Fehér "Dichlorodisulfane" in Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 371.
9. Tyree Jr., S. Y. (1967). "Chapter VI". Inorganic Syntheses. doi:10.1002/9780470132401. ISBN 9780470131688.
10. • Thompson, Q. E.; Crutchfield, M. M.; Dietrich, M. W.; Pierron, E. (1 Aug 1965) . "Organic Esters of Bivalent Sulfur I: Dialkoxy Disulfides". JOC. 30 (8). doi:10.1021/jo01019a044.
    • Thompson, Q. E. "——— III: Sulfoxylates". Ibid. doi:10.1021/jo01019a046
11. ^ Lauss, Hans-Dietrich; Steffens, Wilfried (2000). "Sulfur Halides". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a25_623. ISBN 3527306730.

• Disulfides
• Sulfur chlorides