Sulfuryl chloride

Sulfuryl chloride is an inorganic compound with the formula SO₂Cl₂. At room temperature, it is a colorless liquid with a pungent odor. Sulfuryl chloride is not found in nature.

Sulfuryl chloride

Structure and dimensions of sulfuryl chloride
Ball-and-stick model of sulfuryl chloride
Names
IUPAC name Sulfuryl chloride
Other names Sulfonyl chloride Sulfuric chloride Sulfur dichloride dioxide
Identifiers
CAS Number	7791-25-5 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:29291 Y
ChEMBL	ChEMBL3186735
ChemSpider	23050 Y
ECHA InfoCard	100.029.314
EC Number	232-245-6
Gmelin Reference	2256
PubChem CID	24648
RTECS number	WT4870000
UNII	JD26K0R3J1 Y
UN number	1834
CompTox Dashboard (EPA)	DTXSID6029707
InChI InChI=1S/Cl2O2S/c1-5(2,3)4 Y Key: YBBRCQOCSYXUOC-UHFFFAOYSA-N Y InChI=1/Cl2O2S/c1-5(2,3)4 Key: YBBRCQOCSYXUOC-UHFFFAOYAD
SMILES ClS(Cl)(=O)=O
Properties
Chemical formula	SO2Cl2
Molar mass	134.9698 g mol−1
Appearance	Colorless liquid with a pungent odor. Yellows upon standing.
Density	1.67 g cm−3 (20 °C)
Melting point	−54.1 °C (−65.4 °F; 219.1 K)
Boiling point	69.4 °C (156.9 °F; 342.5 K)
Solubility in water	hydrolyzes
Solubility	miscible with benzene, toluene, chloroform, CCl4, glacial acetic acid
Refractive index (nD)	1.4437 (20 °C)[1]
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H314, H335
Precautionary statements	P260, P261, P264, P271, P280, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P310, P312, P321, P363, P403+P233, P405, P501
NFPA 704 (fire diamond)	3 0 2 W
Flash point	Not flammable
Related compounds
Related sulfuryl halides	Sulfuryl fluoride
Related compounds	Thionyl chloride Chlorosulfonic acid Sulfuric acid Chromyl chloride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

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. An alternative IUPAC name is sulfuryl dichloride.

Sulfur is tetrahedral in SO₂Cl₂ and the oxidation state of the sulfur atom is +6, as in sulfuric acid.

Synthesis

SO₂Cl₂ is prepared by the reaction of sulfur dioxide and chlorine in the presence of a catalyst, such as activated carbon.^[2]

SO₂ + Cl₂ → SO₂Cl₂

The product can be purified by fractional distillation.

Legacy routes

Sulfuryl chloride was first prepared in 1838 by the French chemist Henri Victor Regnault.^[3]

Older routes include oxidation of thionyl chloride:

5 SOCl₂ + HgO → ClSSCl + HgCl₂ + 3 SO₂Cl₂

2 SOCl₂ + MnO₂ → SO₂ + MnCl₂ + SO₂Cl₂

Reactions

Sulfuryl chloride reacts with water, releasing hydrogen chloride gas and sulfuric acid:

2 H₂O + SO₂Cl₂ → 2 HCl + H₂SO₄

For sulfuryl chloride, this happens at room temperature, but the related sulfuryl fluoride does not hydrolyse at temperatures up to 150 °C.

SO₂Cl₂ will also decompose when heated to or above 100 °C, about 30 °C above its boiling point.

Upon standing, SO₂Cl₂ decomposes to sulfur dioxide and chlorine, which gives the older samples a slightly yellowish color.^[2]

SO₂Cl₂ can be used as a source of chlorine in alkane radical chlorination, initiated chemically (usually by peroxide) or by light:^[4]

CH₄ + SO₂Cl₂ → CH₃Cl + SO₂ + HCl

Uses

Sulfuryl chloride is used as a source of Cl₂. Because it is a pourable liquid, it is considered more convenient than Cl₂ to dispense.

Sulfuryl chloride is used in the conversion of C−H to C−Cl adjacent to activating substituents such as carbonyls and sulfoxides:^[5][6]

RC(O)CH₂R' + SO₂Cl₂ → RC(O)CHClR' + HCl + SO₂

It also chlorinates alkanes, alkenes, alkynes, aromatics, ethers (such as tetrahydrofuran) and epoxides. Such reactions occur under free radical conditions using an initiator such as AIBN. It convert thiols or disulfides into the corresponding sulfenyl chlorides:^[7]

RSH + SO₂Cl₂ → RSCl + HCl + SO₂

Occasionally, sulfinyl chlorides result from such reactions.^[8] SO₂Cl₂ can also convert alcohols to alkyl chlorides. In industry, sulfuryl chloride is most used in producing pesticides. Phosphorus pentachloride is prepared by the reaction of white phosphorus with sulfuryl chloride.

Sulfuryl chloride can also be used to treat wool to prevent shrinking.

Precautions

Sulfuryl chloride is toxic, corrosive, and acts as a lachrymator. It releases hydrogen chloride upon contact with water, as well as donor solvents such as dimethyl sulfoxide and dimethylformamide.