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p-Toluenesulfonic acid

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p-Toluenesulfonic acid[1]

Slightly impure sample of the monohydrate
Names
Preferred IUPAC name
4-Methylbenzene-1-sulfonic acid
Other names
4-Methylbenzenesulfonic acid
Tosylic acid
Tosic acid
para-Toluenesulfonic acid
PTSA
pTsOH
TsOH
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.002.891 Edit this at Wikidata
KEGG
UNII
  • InChI=1S/C7H8O3S/c1-6-2-4-7(5-3-6)11(8,9)10/h2-5H,1H3,(H,8,9,10) checkY
    Key: JOXIMZWYDAKGHI-UHFFFAOYSA-N checkY
  • InChI=1/C7H8O3S/c1-6-2-4-7(5-3-6)11(8,9)10/h2-5H,1H3,(H,8,9,10)
    Key: JOXIMZWYDAKGHI-UHFFFAOYAG
  • Cc1ccc(cc1)S(=O)(=O)O
Properties
C7H8O3S
Molar mass 172.20 g/mol (anhydrous)
190.22 g/mol (monohydrate)
Appearance colorless (white) solid
Density 1.24 g/cm3
Melting point 105 to 107 °C (221 to 225 °F; 378 to 380 K) (monohydrate)[2]
38 °C (100 °F; 311 K) (anhydrous)[2]
Boiling point 140 °C (284 °F; 413 K) at 20 mmHg
67 g/100 mL
Acidity (pKa) −2.8 (water) reference for benzenesulfonic acid,[3]

8.5 (acetonitrile)[4]

Structure
tetrahedral at S
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 skin irritant
GHS labelling:[5]
GHS07: Exclamation mark
Warning
H315, H319, H335
P302+P352, P305+P351+P338
Safety data sheet (SDS) External MSDS
Related compounds
Related sulfonic acids
 Benzenesulfonic acid
Sulfanilic acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)

p-Toluenesulfonic acid (PTSA, pTSA, or pTsOH) or tosylic acid (TsOH) is an organic compound with the formula CH3C6H4SO3H. It is a white extremely hygroscopic solid that is soluble in water, alcohols, and other polar organic solvents.[6] The CH3C6H4SO2 group is known as the tosyl group and is often abbreviated as Ts or Tos. Most often, TsOH refers to the monohydrate, TsOH.H2O.[6]

As with other aryl sulfonic acids, TsOH is a strong organic acid. It is about one million times stronger than benzoic acid.[6] It is one of the few strong acids that is solid and therefore is conveniently weighed and stored.

Preparation and uses

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TsOH is prepared on an industrial scale by the sulfonation of toluene. Common impurities include benzenesulfonic acid and sulfuric acid. TsOH is most often supplied as the monohydrate, and it may be necessary to remove the complexed water before use. Impurities can be removed by recrystallization from its concentrated aqueous solution followed by azeotropic drying with toluene.[2]

TsOH finds use in organic synthesis as an "organic-soluble" strong acid. Examples of uses include:

Tosylates

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Alkyl tosylates are alkylating agents because tosylate is electron-withdrawing as well as a good leaving group. Tosylate is a pseudohalide. Toluenesulfonate esters undergo nucleophilic attack or elimination. Reduction of tosylate esters gives the hydrocarbon. Thus, tosylation followed by reduction allows for the deoxygenation of alcohols.

Structures of the 7-norbornenyl cation with p-orbital stabilization.

In a famous and illustrative use of tosylate as a leaving group, the 2-norbornyl cation was formed by an elimination reaction of 7-norbornenyl tosylate. The elimination occurs 1011 times faster than the solvolysis of anti-7-norbornyl p-toluenesulfonate.[10]

Tosylates are also protecting groups for alcohols. They are prepared by combining the alcohol with 4-toluenesulfonyl chloride in the presence of a base. These reactions are usually performed in an aprotic solvent, often pyridine, which additionally acts as a base.[11]

Reactions

[edit]
CH3C6H4SO3H + H2O → C6H5CH3 + H2SO4

This reaction is general for aryl sulfonic acids.[13][14]

See also

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References

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  1. ^ Merck Index, 11th Edition, 9459.
  2. ^ a b c Armarego, W. L. F. (2003). Purification of Laboratory Chemicals (8th ed.). Oxford: Elsevier Science. p. 612. ISBN 978-0-12-805457-4.
  3. ^ Guthrie, J. P. Hydrolysis of esters of oxy acids: pKa values for strong acids. Can. J. Chem. 1978, 56, 2342-2354. doi:10.1139/v78-385
  4. ^ Eckert, F.; Leito, I.; Kaljurand, I.; Kütt, A.; Klamt, A.; Diedenhofen, M. Prediction of Acidity in Acetonitrile Solution with COSMO-RS. J. Comput. Chem. 2009, 30, 799-810. doi:10.1002/jcc.21103
  5. ^ GHS: GESTIS 510754
  6. ^ a b c Baghernejad, Bita (31 August 2011). "Application of p-toluenesulfonic Acid (PTSA) in Organic Synthesis". Current Organic Chemistry. 15 (17): 3091–3097. doi:10.2174/138527211798357074.
  7. ^ H. Griesser, H.; Öhrlein, R.; Schwab, W.; Ehrler, R.; Jäger, V. (2004). "3-Nitropropanal, 3-Nitropropanol, and 3-Nitropropanal Dimethyl Acetal". Organic Syntheses; Collected Volumes, vol. 10, p. 577.
  8. ^ Furuta, K.; Gao, Q.-z.; Yamamoto, H. (1998). "Chiral (Acyloxy)borane Complex-catalyzed Asymmetric Diels-Alder Reaction: (1R)-1,3,4-Trimethyl-3-cyclohexene-1-carboxaldehyde". Organic Syntheses; Collected Volumes, vol. 9, p. 722.
  9. ^ Imwinkelried, R.; Schiess, M.; Seebach, D. (1993). "Diisopropyl (2S,3S)-2,3-O-isopropylidenetartrate". Organic Syntheses; Collected Volumes, vol. 8, p. 201.
  10. ^ Winstein, S.; Shatavsky, M.; Norton, C.; Woodward, R. B. (1955-08-01). "7-Norbornenyl and 7-Norbornyl cations". Journal of the American Chemical Society. 77 (15): 4183–4184. doi:10.1021/ja01620a078. ISSN 0002-7863.
  11. ^ "Nucleophilic Substitution".
  12. ^ L. Field & J. W. McFarland (1963). "p-Toluenesulfonic Anhydride". Organic Syntheses; Collected Volumes, vol. 4, p. 940.
  13. ^ C. M. Suter (1944). The Organic Chemistry of Sulfur. New York: John Wiley & Sons. pp. 387–388.
  14. ^ J. M. Crafts (1901). "Catalysis in concentrated solutions". J. Am. Chem. Soc. 23 (4): 236–249. doi:10.1021/ja02030a007.
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