Sulfuryl chloride

Sulfuryl chloride is SO₂Cl₂, a compound composed of sulfur, oxygen, and chlorine. At room temperature, it is a colorless liquid with a pungent odor. Sulfuryl chloride is not found in nature, as can be inferred from its speedy hydrolysis

Sulfuryl chloride is commonly confused with thionyl chloride, SOCl₂. The properties of these two sulfur oxychlorides are quite different: sulfuryl chloride is a source of chlorine whereas thionyl chloride is a source of chloride ions.

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Properties

Sulfuryl chloride reacts violently with water, releasing hydrogen chloride gas:

2 H₂O + SO₂Cl₂ → 2 HCl + H₂SO₄

SO₂Cl₂ will also decompose when heated to or above 100 °C, about 40 ° above its boiling point.

Upon standing, SO₂Cl₂ decomposes to sulfur dioxide and chlorine, which gives the older samples a slightly yellowish color.

Structure

Sulfur is tetrahedral in SO₂Cl₂, being bound to two oxygen atoms via double bonds and to two chlorine atoms via single bonds. The oxidation state of the sulfur atom is +6, as in H₂SO₄.

Synthesis of sulfuryl chloride

SO₂Cl₂ is prepared by the reaction of sulfur dioxide and chlorine in the presence of a catalyst, such as activated carbon.

SO₂ + Cl₂ → SO₂Cl₂

The crude product can be purified by fractional distillation. It is uncommon to prepare SO₂Cl₂ in the laboratory because it is supplied by many chemical companies, including FisherChemicals, AcrosOrganics, SFChem, Sigma-Aldrich.

Uses

Sulfuryl chloride is often used as source of Cl₂. Because it is a pourable liquid, it is considered more convenient than Cl₂ to measure, store, and dispense. SO₂Cl₂ is widely used as a reagent in the conversion of C-H --> C-Cl adjacent to activating substituents such as carbonyls and sulfoxides. It also chlorinates as alkanes, alkenes, alkynes, aromatics, and epoxides. Such reactions occur under free radical conditions using an initiator such as AIBN. SO₂Cl₂ can also convert alcohols to alkyl chlorides. In industry, sulfuryl chloride is most used in producing pesticides.

SO₂Cl₂ can also be used to treat wool to prevent shrinking.

Precautions

SO₂Cl₂ is toxic, corrosive, and acts as a lachrymator. As described above, it can form explosive mixtures with water, as well as donor solvents such as DMSO and DMF.

References

http://chemfinder.cambridgesoft.com
http://www.chem.unep.ch/irptc/sids/OECDSIDS/7791255.pdf
http://www.mrw.interscience.wiley.com/eros/articles/rs140/frame.html

Further reading

Lautens, M.; Bouchain, G. "[4+3] Cycloaddition in Water. endo,endo-Dimethyl-8-Oxabicyclo[8-Oxabicyclo[3.2.1]oct-6-en-3-one" Organic Syntheses, ; Vol. 79, p.251 (2002) (Coll. Vol. 10, p.336 (2004)). α-Chlorination of 3-pentanone.