Sulfur 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....

 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

SCl₂ is produced by the chlorination of either 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...

 or disulfur dichloride

Disulfur dichloride

Disulfur dichloride is the chemical compound with the formula S2Cl2 . Some alternative names for this compound are sulfur monochloride , disulphur dichloride and sulphur monochloride...

. The process occurs in a series of steps, some of which are:

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

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

The addition of Cl₂

Chlorine

Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...

 to S₂Cl₂ has been proposed to proceed via a mixed valence intermediate Cl₃S-SCl. SCl₂ undergoes even further chlorination to give SCl₄, but this species is unstable at near room temperature. It is likely that several S_xCl₂ exist where x > 2.

Disulfur dichloride

Disulfur dichloride

Disulfur dichloride is the chemical compound with the formula S2Cl2 . Some alternative names for this compound are sulfur monochloride , disulphur dichloride and sulphur monochloride...

, S₂Cl₂, is the most common impurity in SCl₂. Separation of SCl₂ from S₂Cl₂ is possible via distillation with PCl₃

Phosphorus trichloride

Phosphorus trichloride is a chemical compound of phosphorus and chlorine, having chemical formula PCl3. Its shape is trigonal pyramidal. It is the most important of the three phosphorus chlorides. It is an important industrial chemical, being used for the manufacture of organophosphorus compounds...

 to form an azeotrope

Azeotrope

An azeotrope is a mixture of two or more liquids in such a ratio that its composition cannot be changed by simple distillation. This occurs because, when an azeotrope is boiled, the resulting vapor has the same ratio of constituents as the original mixture....

 of 99% purity

Use of SCl₂ in chemical synthesis

• SCl₂ is used in organic synthesis
  Organic synthesis
  Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic molecules can often contain a higher level of complexity compared to purely inorganic compounds, so the synthesis of organic compounds has...
  
  . It adds to alkenes to give chloride-substituted thioethers. Illustrative applications are its addition to 1,5-cyclooctadiene
  1,5-Cyclooctadiene
  1,5-Cyclooctadiene is the organic compound with the chemical formula C8H12. Generally abbreviated COD, this diene is a useful precursor to other organic compounds and serves as a ligand in organometallic chemistry.- Synthesis :...
  
   to give a bicyclic thioether
  Thioether
  A thioether is a functional group in organosulfur chemistry with the connectivity C-S-C as shown on right. Like many other sulfur-containing compounds, volatile thioethers have foul odors. A thioether is similar to an ether except that it contains a sulfur atom in place of the oxygen...
  
   and ethylene
  Ethylene
  Ethylene is a gaseous organic compound with the formula . It is the simplest alkene . Because it contains a carbon-carbon double bond, ethylene is classified as an unsaturated hydrocarbon. Ethylene is widely used in industry and is also a plant hormone...
  
   to give 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...
  
   S(CH₂CH₂Cl)₂.

SCl₂ is also a precursor to several inorganic sulfur compounds. Treatment with fluoride salts gives SF₄

Sulfur tetrafluoride

Sulfur tetrafluoride is the chemical compound with the formula SF4. This species exists as a gas at standard conditions. It is a corrosive species that releases dangerous HF upon exposure to water or moisture...

. Reaction with ammonia affords sulfur nitrides related to S₄N₄

Tetrasulfur tetranitride

Tetrasulfur tetranitride is an inorganic compound with the formula S4N4. This gold-poppy coloured solid is the most important binary sulfur nitride, which are compounds that contain only the elements sulfur and nitrogen. It is a precursor to many S-N compounds and has attracted wide interest for...

. With H₂S, SCl₂ reacts to give "lower" sulfanes such as S₃H₂.

Safety considerations

SCl₂ hydrolyzes with release of HCl

Hydrogen chloride

The compound hydrogen chloride has the formula HCl. At room temperature, it is a colorless gas, which forms white fumes of hydrochloric acid upon contact with atmospheric humidity. Hydrogen chloride gas and hydrochloric acid are important in technology and industry...

. Old samples contain Cl₂.