4-Toluenesulfonyl Chloride

This white, malodorous solid is a reagent widely used in organic synthesis. Abbreviated TsCl or TosCl, it is a derivative of toluene and contains a sulfonyl chloride (−SO₂Cl) functional group.

4-Toluenesulfonyl chloride

Names
Preferred IUPAC name 4-Methylbenzene-1-sulfonyl chloride
Other names Tosyl chloride, p-toluenesulfonyl chloride, p-TsCl, TsCl
Identifiers
CAS Number	98-59-9 Y
3D model (JSmol)	Interactive image
ChemSpider	7119 Y
ECHA InfoCard	100.002.441
PubChem CID	7397
UNII	027KYN78B4 Y
CompTox Dashboard (EPA)	DTXSID1052660
InChI InChI=1S/C7H7ClO2S/c1-6-2-4-7(5-3-6)11(8,9)10/h2-5H,1H3 Y Key: YYROPELSRYBVMQ-UHFFFAOYSA-N Y InChI=1/C7H7ClO2S/c1-6-2-4-7(5-3-6)11(8,9)10/h2-5H,1H3 Key: YYROPELSRYBVMQ-UHFFFAOYAN
SMILES O=S(Cl)(=O)c1ccc(cc1)C
Properties
Chemical formula	C7H7ClO2S
Molar mass	190.65 g/mol
Appearance	White solid
Melting point	65 to 69 °C (149 to 156 °F; 338 to 342 K)
Boiling point	134 °C (273 °F; 407 K) at 10 mmHg
Solubility in water	Reacts with water
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	Releases HCl on contact with water
NFPA 704 (fire diamond)	3 1 0
Flash point	128 °C (262 °F; 401 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

In characteristic manner, TsCl converts alcohols (abbreviated ROH) into the corresponding toluenesulfonate esters, or tosyl derivatives ("tosylates"):

CH₃C₆H₄SO₂Cl + ROH → CH₃C₆H₄SO₂OR + HCl

Tosylates can be cleaved with lithium aluminium hydride:

4 CH₃C₆H₄SO₂OR + LiAlH₄ → LiAl(O₃SC₆H₄CH₃)₄ + 4 RH

Thus, tosylation followed by reduction allows for removal of a hydroxyl group.

Likewise, TsCl is used to prepare sulfonamides from amines:

CH₃C₆H₄SO₂Cl + R₂NH → CH₃C₆H₄SO₂NR₂ + HCl

The resulting sulfonamides are non-basic and, when derived from primary amines, are even acidic.

TsCl reacts with hydrazine to give p-toluenesulfonyl hydrazide.

The preparation of tosyl esters and amides are conducted in the presence of a base, which absorbs hydrogen chloride. The selection of the base is often crucial to the efficiency of tosylation. Typical bases include pyridine and triethylamine. Unusual bases are also used; for example, catalytic amounts of trimethylammonium chloride in the presence of triethylamine is highly effective by virtue of the trimethylamine.

Being a widely available reagent, TsCl has been heavily examined from the perspective of reactivity. It is used in dehydrations to make nitriles, isocyanides and diimides. In an unusual reaction focusing on the sulfur center, zinc reduces TsCl to the sulfinate, CH₃C₆H₄SO₂Na.

This reagent is inexpensively available for laboratory use. It is a by-product from the production of ortho-toluenesulfonyl chloride (a precursor for the synthesis of the common food additive and catalyst saccharin), via the chlorosulfonation of toluene:

CH₃C₆H₅ + SO₂Cl₂ → CH₃C₆H₄SO₂Cl + HCl

Tosyl chloride is considered to be a toxic and corrosive substance.