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p-Toluenesulfonic acid

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p-Toluenesulfonic acid[1]
P-Toluenesulfonic acid
Names
IUPAC name
4-methylbenzenesulfonic acid
Other names
Tosylic acid
tosic acid
PTSA
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.002.891 Edit this at Wikidata
KEGG
  • 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
CH3C6H4SO3H
Molar mass 172.20 g/mol (anhydrous)
190.22 g/mol (monohydrate)
Appearance colorless (white) solid
Density 1.24 g/cm3
Melting point 38 °C, 311 K (anhydrous) [2]
103-106 °C, 376-379 K (monohydrate)
Boiling point 140 °C (284 °F; 413 K)
67 g/100 mL
Acidity (pKa) -2.8 (water),[3]

8.5 (acetonitrile)[4]

Structure
tetrahedral at S
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 skin irritant
Related compounds
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) or tosylic acid (TsOH) is an organic compound with the formula CH3C6H4SO3H. It is a white solid that is soluble in water, alcohols, and other polar organic solvents. The 4-CH3C6H4SO2- group is known as tosyl group and is often abbreviated as Ts or Tos. Most often, TsOH refers to the monohydrate, TsOH.H2O.

TsOH is a strong organic acid, about a million times stronger than benzoic acid. It is one of the few strong acids that is solid and, hence, conveniently weighed. Also, unlike some strong mineral acids (especially nitric acid, sulfuric acid, and perchloric acid), TsOH is non-oxidizing.

Preparation and handling

TsOH is prepared on an industrial scale by the sulfonation of toluene. It hydrates readily. Common impurities include benzenesulfonic acid and sulfuric acid. Impurities can be removed by recrystallization from its concentrated aqueous solution followed by azeotropic drying with toluene.[5]

Toluenesulfonic acid finds use in organic synthesis as an "organic-soluble" acid catalyst. Examples of uses:

Tosylate esters

Ball-and-stick model of the tosylate anion

Tosylate esters are used as alkylating agents because the tosyl group is electron-withdrawing, which makes the tosylate anion a good leaving group. The tosyl group is also a protecting group for alcohols and amines, prepared by combining the alcohol with 4-toluenesulfonyl chloride, usually in an aprotic solvent, often pyridine, the basicity of which activates the reaction.[9] 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.

Reactions

p-Toluenesulfonic acid may be converted to p-toluenesulfonic anhydride by heating with phosphorus pentoxide.[10] When TsOH (any isomers) is treated with acid and water, toluene is formed:

CH3C6H4SO3H + H2O → C6H5CH3 + H2SO4

See also

References

  1. ^ Merck Index, 11th Edition, 9459.
  2. ^ Armarego, Wilfred (2003). Purification of Laboratory Chemicals. Elsevier Science. p. 370. ISBN 0-7506-7571-3.
  3. ^ Guthrie, J. P. Hydrolysis of esters of oxy acids: pKa values for strong acids. Can. J. Chem. 1978, 56, 2342-2354.
  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. ^ Perrin, D. D. and Armarego, W. L. F., Purification of Laboratory Chemicals, Pergamon Press: Oxford, 1988.
  6. ^ H. Griesser, H.; Öhrlein, R.; Schwab, W.; Ehrler, R.; Jäger, V. (2004). "3-Nitropropanal, 3-Nitropropanol, and 3-Nitropropanal Dimethyl Acetal". Organic Syntheses{{cite journal}}: CS1 maint: multiple names: authors list (link); Collected Volumes, vol. 10, p. 577.
  7. ^ 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{{cite journal}}: CS1 maint: multiple names: authors list (link); Collected Volumes, vol. 9, p. 722.
  8. ^ Imwinkelried, R.; Schiess, M.; Seebach, D. (1993). "Diisopropyl (2S,3S)-2,3-O-isopropylidenetartrate". Organic Syntheses{{cite journal}}: CS1 maint: multiple names: authors list (link); Collected Volumes, vol. 8, p. 201.
  9. ^ Nucleophilic Substitution
  10. ^ L. Field and J. W. McFarland (1963). "p-Toluenesulfonic Anhydride". Organic Syntheses; Collected Volumes, vol. 4, p. 940.
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