4-Toluenesulfonyl chloride

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4-Toluenesulfonyl chloride
P-Toluenesulfonyl chloride structure.svg
CAS number 98-59-9 YesY
PubChem 160808444
ChemSpider 7119 YesY
Jmol-3D images Image 1
Molecular 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 Hydrolysis
Main hazards Releases acid
NFPA 704
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g., canola oil Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point 128 °C (262 °F; 401 K)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

4-Toluenesulfonyl chloride (p-toluenesulfonyl chloride, toluene-p-sulfonyl chloride) is an organic compound with the formula CH3C6H4SO2Cl. This white, 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.


Main article: Tosyl

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


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[edit]

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]


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


  1. ^ a b c Whitaker, D. T.; Whitaker, K. S.; Johnson, C. R.; Haas, J. (2006). "p-Toluenesulfonyl Chloride". Encyclopedia of Reagents for Organic Synthesis. New York: John Wiley. doi:10.1002/047084289X.rt136.pub2. 
  2. ^ Ichikawa, J.; Nadano, R.; Mori, T.; Wada, Y. (2006), "5-endo-trig Cyclization of 1,1-Difluoro-1-alkenes: Synthesis of 3-Butyl-2-Fluoro-1-Tosylindole", Org. Synth. 83: 111 ; Coll. Vol. 11: 834 
  3. ^ Whitmore, F. C.; Hamilton, F. H. (1922), "Sodium Toluenesulfinate", Org. Synth. 2: 89 ; Coll. Vol. 1: 492 
  4. ^ Lindner, O.; Rodefeld, L. (2005), "Benzenesulfonic Acids and Their Derivatives", Ullmann's Encyclopedia of Industrial Chemistry, Weinheim: Wiley-VCH, doi:10.1002/14356007.a03_507