p-Toluenesulfonic acid
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Slightly impure sample of the monohydrate
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Names | |||
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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 (
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ChEBI | |||
ChEMBL | |||
ChemSpider | |||
DrugBank | |||
ECHA InfoCard
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100.002.891 | ||
KEGG | |||
PubChem CID
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UNII |
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CompTox Dashboard (EPA)
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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
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skin irritant | ||
GHS labelling:[5] | |||
Warning | |||
H315, H319, H335 | |||
P302+P352, P305+P351+P338 | |||
Safety data sheet (SDS) | External MSDS | ||
Related compounds | |||
Related sulfonic acids
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Benzenesulfonic acid Sulfanilic acid | ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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p-Toluenesulfonic acid (PTSA, pTSA, or pTsOH) or tosylic acid (TsOH) is an
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
TsOH is prepared on an industrial scale by the sulfonation of toluene. Common impurities include benzenesulfonic acid and sulfuric acid. TsOH monohydrate contains an amount of water. To estimate the total moisture present as impurity, the Karl Fischer method is used.[citation needed] 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:
- Acetalization of an aldehyde.[7]
- Fischer–Speier esterification[8]
- Transesterification reactions[9]
Tosylates
Alkyl tosylates are
In a famous and illustrative use of tosylate, 2-norbornyl cation was displaced from the 7-norbornenyl tosylate. The elimination occurs 1011 times faster than the solvolysis of anti-7-norbornyl p-toluenesulfonate.[10]
Tosylates are also
Reactions
- TsOH may be converted to p-toluenesulfonic anhydride by heating with phosphorus pentoxide.[12]
- When heated with acid and water, TsOH undergoes hydrolysis to toluene:
- CH3C6H4SO3H + H2O → C6H5CH3 + H2SO4
This reaction is general for
See also
References
- ^ Merck Index, 11th Edition, 9459.
- ^ ISBN 978-0-12-805457-4.
- ^ Guthrie, J. P. Hydrolysis of esters of oxy acids: pKa values for strong acids. Can. J. Chem. 1978, 56, 2342-2354.
- ^ GHS: GESTIS 510754
- ^ .
- ^ 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.
- ^ 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.
- ^ Imwinkelried, R.; Schiess, M.; Seebach, D. (1993). "Diisopropyl (2S,3S)-2,3-O-isopropylidenetartrate". Organic Syntheses; Collected Volumes, vol. 8, p. 201.
- ISSN 0002-7863.
- ^ "Nucleophilic Substitution".
- ^ L. Field & J. W. McFarland (1963). "p-Toluenesulfonic Anhydride". Organic Syntheses; Collected Volumes, vol. 4, p. 940.
- ^ C. M. Suter (1944). The Organic Chemistry of Sulfur. New York: John Wiley & Sons. pp. 387–388.
- .