4-Toluenesulfonyl chloride explained

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.

Uses

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

CH3C6H4SO2Cl + ROH → CH3C6H4SO2OR + HClTosylates can be cleaved with lithium aluminium hydride:

4 CH3C6H4SO2OR + LiAlH4 → LiAl(O3SC6H4CH3)4 + 4 RHThus, tosylation followed by reduction allows for removal of a hydroxyl group.

Likewise, TsCl is used to prepare sulfonamides from amines:

CH3C6H4SO2Cl + R2NH → CH3C6H4SO2NR2 + HClThe 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.[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 and diimides.[1] In an unusual reaction focusing on the sulfur center, zinc reduces TsCl to the sulfinate, CH3C6H4SO2Na.

Manufacture

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

Hazards

Tosyl chloride is "a corrosive lachrymator."[1]

Notes and References

  1. Encyclopedia: Whitaker, D. T. . Whitaker, K. S. . Johnson, C. R. . Haas, J. . p-Toluenesulfonyl Chloride . Encyclopedia of Reagents for Organic Synthesis . 2006 . John Wiley . New York . 10.1002/047084289X.rt136.pub2 . http://onlinelibrary.wiley.com/o/eros/articles/rt136/frame.html . 2013-05-28 . https://web.archive.org/web/20160305090729/http://onlinelibrary.wiley.com/o/eros/articles/rt136/frame.html . 2016-03-05 . dead . P-Toluenesulfonyl Chloride . 978-0471936237 .