4-Toluenesulfonyl chloride

4-Toluenesulfonyl chloride
IUPAC name 4-methylbenzenesulfonyl chloride
Other names Tosyl chloride, p-toluenesulfonyl chloride, p-TsCl, TsCl
Identifiers
CAS number	98-59-9 Y
ChemSpider	7119 Y
Jmol-3D images	Image 1
SMILES O=S(Cl)(=O)c1ccc(cc1)C
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
Properties
Molecular formula	C7H7ClO2S
Molar mass	190.65 g/mol
Appearance	White solid
Melting point	65-69 °C
Boiling point	134 °C at 10 mmHg
Solubility in water	hydrolysis
Hazards
Main hazards	releases acid
NFPA 704	1 3 0
Flash point	128 °C
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

4-Toluenesulfonyl chloride (p-toluenesulfonyl chloride, toluene-p-sulfonyl chloride) is an organic compound with the formula CH₃C₆H₄SO₂Cl. This colourless, malodorous solid is a reagent widely used in organic synthesis.^[1] Abbreviated TsCl or TosCl, it is a derivative of toluene and contains a sulfonyl chloride (-SO₂Cl) functional group.

Uses

Main article: Tosyl

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:^[2]

CH₃C₆H₄SO₂Cl + R₂NH → CH₃C₆H₄SO₂NR₂ + HCl

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

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.^[1]

Other reactions

Being a widely available reagent, TsCl has been heavily examined from the perspective of reactivity. It is used in dehydrations to make nitriles, isocyanides, diimides.^[1] In an unusual reaction focusing on the sulfur center, zinc reduces TsCl to the sulfinate, CH₃C₆H₄SO₂Na.^[3]

Manufacture

TsCl is inexpensively available for laboratory use. It is a by-product from the production of o-toluenesulfonyl chloride (a precursor for the synthesis of saccharin), via the chlorosulfonation of toluene:^[4]

CH₃C₆H₅ + SO₂Cl₂ → CH₃C₆H₄SO₂Cl + HCl

References

1. ^ ^{a b c} D. Todd Whitaker, K. Sinclair Whitaker, Carl R. Johnson, Julia Haas, "p-Toluenesulfonyl Chloride" in Encyclopedia of Reagents for Organic Synthesis, 2006, John Wiley, New York. doi:10.1002/047084289X.rt136.pub2 Article Online Posting Date: September 15, 2006
2. ^ Junji Ichikawa, Ryo Nadano, Takashi Mori, and Yukinori Wada (2006), "5-endo-trig Cyclization of 1,1-Difluoro-1-alkenes: Synthesis of 3-Butyl-2-Fluoro-1-Tosylindole", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=Cv83p0111 
3. ^ Frank C. Whitmore, Frances H. Hamilton (1941), "Sodium Toluenesulfinate", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=CV1P0492 ; Coll. Vol. 1: 492 
4. ^ Otto Lindner, Lars Rodefeld "Benzenesulfonic Acids and Their Derivatives" in Ullmann's Encyclopedia of Industrial Chemistry 2001, Wiley-VCH, Weinheim. Published online: 15 September, 2000