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.

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.