p -toluenesulfonic acid
Structural formula | ||||||||||||||||||||||
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General | ||||||||||||||||||||||
Surname | p -toluenesulfonic acid | |||||||||||||||||||||
other names |
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Molecular formula | C 7 H 8 O 3 S | |||||||||||||||||||||
Brief description |
colorless or purple, pungent-smelling crystals |
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properties | ||||||||||||||||||||||
Molar mass | 172.20 g mol −1 (anhydrous) | |||||||||||||||||||||
Physical state |
firmly |
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density |
1.24 g cm −3 |
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Melting point |
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boiling point |
185-187 ° C |
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Vapor pressure |
10 Pa (20 ° C) |
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pK s value |
- 2.8 |
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solubility |
easy in water (750 g l −1 ) |
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safety instructions | ||||||||||||||||||||||
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Toxicological data | ||||||||||||||||||||||
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . |
p -Toluenesulfonic acid is an organic sulfonic acid . It forms a monohydrate and is an important reagent in organic synthesis. Their salts and esters arecalled tosylates .
presentation
p -Toluenesulfonic acid is a by-product of the Remsen-Fahlberg process for the production of saccharin . It is produced by sulfonation of toluene . The purification is carried out by crystallization from hydrochloric acid and azeotropic drying.
properties
In aqueous solutions, p -toluenesulfonic acid is largely dissociated. Its barium or lead salts, unlike those of sulfuric acid , are readily soluble in water. p -Toluenesulfonic acid decomposes in the heat, whereby u. A. Sulfur dioxide is produced.
use
p -Toluenesulfonic acid is used as an acidic catalyst, among other things for acetalizations , esterifications or for dehydrations. Its advantage over sulfuric acid is that it is non-oxidizing and hardly dehydrating. p -toluenesulfonic acid is used for synthesis of the pesticide amitraz , pretilachlor , propaquizafop , pyriproxifen and triasulfuron needed.
Toluenesulfonate as a leaving group
→ see main article tosyl group
In preparative chemistry, the anion of p -toluenesulfonic acid occurs as an important leaving group in nucleophilic substitutions . With the acid halide p -toluenesulfonic acid chloride (tosyl chloride), hydroxyl groups of a compound can be converted to sulfonic acid esters . This group is a good leaving group compared to the hydroxy group.
hazards
p- Toluenesulfonic acid always contains a little sulfuric acid and is extremely corrosive to the skin, mucous membranes and eyes. If you inhale the dust there is a risk of pulmonary edema .
See also
Individual evidence
- ↑ Entry on TOLUENE SULFONIC ACID in the CosIng database of the EU Commission, accessed on May 11, 2020.
- ↑ a b c d e f g h Entry on toluene-4-sulfonic acid (with a maximum of 5 percent sulfuric acid) in the GESTIS substance database of the IFA , accessed on February 1, 2016(JavaScript required) .
- ↑ a b Entry on methylbenzenesulfonic acids. In: Römpp Online . Georg Thieme Verlag, accessed on April 18, 2012.
- ↑ Guthrie, JP Hydrolysis of esters of oxy acids: p K a values for strong acids. Can. J. Chem . 1978 , 56 , 2342-2354.
- ↑ Entry on Toluene-4-sulphonic acid in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on February 1, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .
- ↑ Data sheet p-toluenesulfonic acid (PDF) from Merck , accessed on January 19, 2011.
- ↑ Beyer-Walter, Textbook of Organic Chemistry, 23rd Edition, S. Hirzel Verlag 1998 ISBN 3-7776-0808-4
- ↑ Thomas A. Unger: Pesticide Synthesis Handbook . William Andrew, 1996, ISBN 0-8155-1853-6 , pp. 1050 ( preview ).