Disulfur dichloride

Disulfur dichloride

Wireframe model of disulfur dichloride
Spacefill model of disulfur dichloride
Names
IUPAC name Disulfur dichloride
Systematic IUPAC name Dichlorodisulfane
Other names Bis[chloridosulfur](S–S) Dimeric sulfenic chloride Sulfur monochloride
Identifiers
CAS Number	10025-67-9 Y 85408-26-0 (isobutenate) Y
ChemSpider	23192 Y 19158348 (isobutenate) N
EC Number	233-036-2
Jmol 3D model	Interactive image
MeSH	Sulfur+monochloride
PubChem	24807
RTECS number	WS4300000
UN number	3390
InChI InChI=1S/Cl2S2/c1-3-4-2 Y Key: PXJJSXABGXMUSU-UHFFFAOYSA-N Y InChI=1/Cl2S2/c1-3-4-2 Key: PXJJSXABGXMUSU-UHFFFAOYAK
SMILES ClSSCl
Properties
Chemical formula	S2Cl2
Molar mass	135.04 g/mol
Appearance	Light-amber to yellow-red, oily liquid
Odor	pungent, nauseating, irritating
Density	1.688 g/cm3
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, chloroform, CCl4
Vapor pressure	7 mmHg (20 °C)
Refractive index (nD)	1.658
Structure
Coordination geometry	C2, gauche
Dipole moment	1.60 D
Vapor pressure	{{{value}}}
Related compounds
Related sulfur chlorides	Sulfur dichloride Thionyl chloride Sulfuryl chloride
Related compounds	Disulfur difluoride Disulfur dibromide
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

Disulfur dichloride is the chemical compound of sulfur and chlorine with the formula S₂Cl₂

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).

Synthesis, basic properties, reactions

Pure disulfur dichloride is a 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. The reaction takes place 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 gives 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:

S₂Cl₂ + n S → S_2+nCl₂

Pure disulfur dichloride is obtained by distilling the yellow-orange liquid over excess elemental sulfur.

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

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 heptasulfur imide (S₇NH) and related S-N rings S_8-x(NH)_x (x = 2, 3).

Applications

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

S₂Cl₂ + 2 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 at 60 °C (the Levinstein process):

S₂Cl₂ + 2 C₂H₄ → (ClC₂H₄)₂S + 1/8 S₈

Other uses include manufacturing sulfur dyes, insecticides, synthetic rubbers. Also used in cold vulcanization of rubbers, as polymerization catalyst for vegetable oils and for hardening soft woods.