p -toluenesulfonic acid

Structural formula
General
Surname	p -toluenesulfonic acid
other names	para -toluenesulfonic acid 4-methylbenzenesulfonic acid Toluene-4-sulfonic acid pTsOH Tosylic acid PTSA TOLUENE SULFONIC ACID ( INCI )
Molecular formula	C 7 H 8 O 3 S
Brief description	colorless or purple, pungent-smelling crystals
External identifiers / databases
CAS number 104-15-4 (anhydrous) 6192-52-5 ( monohydrate ) EC number 203-180-0 ECHA InfoCard 100.002.891 PubChem 6101 ChemSpider 5876 DrugBank DB03120 Wikidata Q285878
properties
Molar mass	172.20 g mol −1 (anhydrous)
Physical state	firmly
density	1.24 g cm −3
Melting point	106 ° C (anhydrous) 56 ° C ( monohydrate )
boiling point	185-187 ° C
Vapor pressure	10  Pa (20 ° C)
pK s value	- 2.8
solubility	easy in water (750 g l −1 )
safety instructions
GHS hazard labeling from  Regulation (EC) No. 1272/2008 (CLP) , expanded if necessary Caution H and P phrases H: 315-319-335 P: 302 + 352-304 + 340-305 + 351 + 338
Toxicological data	2570 mg kg −1 ( LD 50 ,  rat ,  oral , monohydrate)
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

• Toluenesulfonic acids

Individual evidence

1. ↑ Entry on TOLUENE SULFONIC ACID in the CosIng database of the EU Commission, accessed on May 11, 2020.
2. ↑ ^{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) .
3. ↑ ^{a b} Entry on methylbenzenesulfonic acids. In: Römpp Online . Georg Thieme Verlag, accessed on April 18, 2012.
4. ↑ Guthrie, JP Hydrolysis of esters of oxy acids: p K _a values ​​for strong acids. Can. J. Chem . 1978 , 56 , 2342-2354.
5. ↑ 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 .
6. ↑ Data sheet p-toluenesulfonic acid (PDF) from Merck , accessed on January 19, 2011.
7. ↑ Beyer-Walter, Textbook of Organic Chemistry, 23rd Edition, S. Hirzel Verlag 1998 ISBN 3-7776-0808-4
8. ↑ Thomas A. Unger: Pesticide Synthesis Handbook . William Andrew, 1996, ISBN 0-8155-1853-6 , pp. 1050 ( preview ).