Disulfur dichloride
Overview
 
Disulfur dichloride is the chemical compound
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...

 with the formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....

 S2Cl2
. Some alternative names for this compound are sulfur monochloride (the name implied by its empirical formula
Empirical formula
In chemistry, the empirical formula of a chemical compound is the simplest positive integer ratio of atoms of each element present in a compound. An empirical formula makes no reference to isomerism, structure, or absolute number of atoms. The empirical formula is used as standard for most ionic...

, 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 Cla-S-S and S-S-Clb planes is 90°.
Encyclopedia
Disulfur dichloride is the chemical compound
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...

 with the formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....

 S2Cl2
. Some alternative names for this compound are sulfur monochloride (the name implied by its empirical formula
Empirical formula
In chemistry, the empirical formula of a chemical compound is the simplest positive integer ratio of atoms of each element present in a compound. An empirical formula makes no reference to isomerism, structure, or absolute number of atoms. The empirical formula is used as standard for most ionic...

, 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 Cla-S-S and S-S-Clb planes is 90°. This structure is referred to as gauche, and is akin to that for H2O2
Hydrogen peroxide
Hydrogen peroxide is the simplest peroxide and an oxidizer. Hydrogen peroxide is a clear liquid, slightly more viscous than water. In dilute solution, it appears colorless. With its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent...

. A different isomer
Isomer
In chemistry, isomers are compounds with the same molecular formula but different structural formulas. Isomers do not necessarily share similar properties, unless they also have the same functional groups. There are many different classes of isomers, like stereoisomers, enantiomers, geometrical...

 of S2Cl2 is S=SCl2; this isomer forms transiently when S2Cl2 is exposed to UV-radiation (see thiosulfoxide
Thiosulfoxide
A thiosulfoxide is a chemical compound containing a sulfur to sulfur double bond of the type RR'S=S with R and R' both alkyl or aryl residues. A 1982 review concluded that there was as yet no definitive evidence for the existence of stable thiosulfoxides which can be attributed to the double bond...

s).

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
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...

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

Excess chlorine gives sulfur dichloride
Sulfur dichloride
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. It is used as a precursor to organosulfur compounds.-Chlorination of sulfur:...

:
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
Carbon disulfide
Carbon disulfide is a colorless volatile liquid with the formula CS2. The compound is used frequently as a building block in organic chemistry as well as an industrial and chemical non-polar solvent...

 as in the synthesis of thiophosgene
Thiophosgene
Thiophosgene is a red liquid with the formula CSCl2. It is a molecule with trigonal planar geometry. There are two reactive C–Cl bonds that allow it to be used in diverse organic syntheses.-Synthesis of CSCl2:...

.

Applications

S2Cl2 has been used to introduce C-S bonds. In the presence of AlCl3
Aluminium chloride
Aluminium chloride is the main compound of aluminium and chlorine. It is white, but samples are often contaminated with iron trichloride, giving it a yellow colour. The solid has a low melting and boiling point. It is mainly produced and consumed in the production of aluminium metal, but large...

, S2Cl2 reacts with benzene to give diphenyl sulfide:
S2Cl2 + 2 C6H6 → (C6H5)2S + 2 HCl + 1/8 S8

Aniline
Aniline
Aniline, phenylamine or aminobenzene is an organic compound with the formula C6H5NH2. Consisting of a phenyl group attached to an amino group, aniline is the prototypical aromatic amine. Being a precursor to many industrial chemicals, its main use is in the manufacture of precursors to polyurethane...

s react with S2Cl2 in the presence of NaOH via the so-called Herz reaction
Herz reaction
The Herz-reaction, named after the chemist Richard Herz, is the chemical conversion of an aniline-derivative to a so-called Herz-salt with disulfur dichloride, followed by hydrolysis of this Herz-salt to the corresponding sodium thiolate :-Benzothiazoles:The sodium thiolate 3 can be converted to...

 to give ortho-aminothiophenolates. These species are precursors to thioindigo dyes. It is also used to prepare the sulfur mustard
Sulfur mustard
The sulfur mustards, or sulphur mustards, commonly known as mustard gas, are a class of related cytotoxic, vesicant chemical warfare agents with the ability to form large blisters on exposed skin. Pure sulfur mustards are colorless, viscous liquids at room temperature...

"gas" by reaction with ethylene:
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.
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