Disulfur dichloride
IUPAC name	Disulfur dichloride Dichlorodisulfane Bis[chloridosulfur](S–S)
Other names	Sulfur monochloride
Identifiers
CAS number	10025-67-9 Y
EC number	233-036-2
UN number	1828
RTECS number	WS4300000
SMILES	ClSSCl
Properties
Molecular formula	S2Cl2
Molar mass	135.04 g/mol
Appearance	yellow liquid
Density	1.688 g/cm3
Melting point	–80 °C
Boiling point	137.1 °C
Solubility in water	decomp with loss of HCl
Solubility	soluble in ethanol, benzene, ether, chloroform, CCl4 [1]
Refractive index (nD)	1.658
Structure
Coordination geometry	gauche
Dipole moment	1.60 D [2]
Hazards
MSDS	ICSC 0958
EU Index	016-012-00-4
EU classification	Toxic (T) Harmful (Xn) Corrosive (C) Dangerous for the environment (N)
R-phrases	R14, R20, R25, R29, R35, R50
S-phrases	(S1/2), S26, S36/37/39, S45, S61
NFPA 704	1 2 1
Flash point	118.5 °C
Autoignition temperature	234 °C
Related compounds
Related sulfur chlorides	Sulfur dichloride Thionyl chloride Sulfuryl chloride
Related compounds	Disulfur difluoride Disulfur dibromide
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Disulfur dichloride is the chemical compound with the formula S₂Cl₂ ^{[3][4][5] [6]} . Some alternative names for this compound are sulfur monochloride (the name implied by its empirical formula, SCl), disulphur dichloride (British English Spelling) and sulphur monochloride (British English Spelling). S₂Cl₂ has the structure implied by the formula Cl-S-S-Cl, wherein the angle between the Cl^a-S-S and S-S-Cl^b 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 (see thiosulfoxides).

[edit] 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 → S_2+nCl₂

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

[edit] 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

[edit] References

1. ^ Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0070494398
2. ^ Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0070494398
3. ^ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
4. ^ W. W. Hartman, L. A. Smith, and J. B. Dickey "Diphenylsulfide" Organic Syntheses, Coll. Vol. 2, p.242; Vol. 14, p.36.
5. ^ R. J. Cremlyn “An Introduction to Organosulfur Chemistry” John Wiley and Sons: Chichester (1996). ISBN 0-471-95512-4
6. ^ Garcia-Valverde M., Torroba T. (2006). "Heterocyclic chemistry of sulfur chlorides - Fast ways to complex heterocycles". European J. Org. Chem. 4: 849–861. doi:10.1002/ejoc.200500786.