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Disulfur dichloride

Disulfur dichloride
IUPAC name Sulfur(I) chloride
Other names Disulfur dichloride
Sulfur monochloride
CAS number 10025-67-9
RTECS number WS4300000
Molecular formula S2Cl2
Molar mass 135.04 g/mol
Appearance yellow liquid
Density 1.688 g/cm³, liquid
Melting point

–80 °C

Boiling point

137.1 °C

Solubility in water decomp with loss of HCl
Refractive index (nD) 1.658
Main hazards corrosive
NFPA 704
R-phrases 14-20-25-29-35-50
S-phrases 26-36/37/39-45-61
Related Compounds
Related compounds SCl2
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and references

Disulfur dichloride is the chemical compound with the formula S2Cl2. An alternative name for this compound is sulfur monochloride, the name implied by its empirical formula, SCl. S2Cl2 has the structure implied by the formula Cl-S-S-Cl, wherein the angle between the Cla-S-S and S-S-Clb planes is 90°. This structure is referred to as gauche, and is akin to that for H2O2. A different isomer of S2Cl2 is S=SCl2; this isomer forms transiently when S2Cl2 is exposed to UV-radiation.

Additional recommended knowledge

Synthesis and basic properties

Disulfur dichloride is an orange/yellow liquid that smokes in air due to reaction with water:

2 S2Cl2 + 2 H2O → SO2 + 4 HCl + 3/8 S8

It is synthesized by partial chlorination of elemental sulfur:

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

Excess chlorine gives sulfur dichloride:

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

Both reactions are reversible, and upon standing, SCl2 releases chlorine to revert to the disulfur dichloride. It has the ability to dissolve sulfur, which reflects in part the formation of polysulfanes:

S2Cl2 + n S → S2+nCl2

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

Applications in synthesis

S2Cl2 has been used to introduce C-S bonds. In the presence of AlCl3, S2Cl2 reacts with benzene to give diphenyl sulfide:

S2Cl2 + C6H6 → (C6H5)2S + 2 HCl + 1/8 S8

Anilines react with S2Cl2 in the presence of NaOH via the so-called Herz reaction to give ortho-aminothiophenolates. These species are precursors to thioindigo dyes. It is also used to prepare the sulfur mustard "gas" by reaction with ethylene:

S2Cl2 + 2 C2H4 → (ClC2H4)2S + 1/8 S8


    1. Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
    2. W. W. Hartman, L. A. Smith, and J. B. Dickey "Diphenylsulfide" Organic Syntheses, Coll. Vol. 2, p.242; Vol. 14, p.36.
    3. R. J. Cremlyn “An Introduction to Organosulfur Chemistry” John Wiley and Sons: Chichester (1996). ISBN 0-471-95512-4
    4. Garcia-Valverde M., Torroba T. (2006). "Heterocyclic chemistry of sulfur chlorides - Fast ways to complex heterocycles". European J. Org. Chem. 4: 849-861.
    This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Disulfur_dichloride". A list of authors is available in Wikipedia.
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