P-Toluenesulfonic acid

p-Toluenesulfonic acid
	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
CAS Number	104-15-4 ; 6192-52-5 (monohydrate) ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:27849 ;
ChEMBL	ChEMBL541253 ;
ChemSpider	5876 ;
DrugBank	DB03120 ;
ECHA InfoCard	100.002.891
KEGG	C06677 ;
PubChem CID	6101;
UNII	QGV5ZG5741 ; 3BTO78GAFF ((monohydrate) ;
CompTox Dashboard (EPA)	DTXSID0026701 ;
	InChI InChI=1S/C7H8O3S/c1-6-2-4-7(5-3-6)11(8,9)10/h2-5H,1H3,(H,8,9,10) Key: JOXIMZWYDAKGHI-UHFFFAOYSA-N ; 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;
	SMILES Cc1ccc(cc1)S(=O)(=O)O;
Properties
Chemical formula	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) ; 38 °C (100 °F; 311 K) (anhydrous)
Boiling point	140 °C (284 °F; 413 K) at 20 mmHg
Solubility in water	67 g/100 mL
Acidity (pKa)	−2.8 (water) reference for benzenesulfonic acid,; 8.5 (acetonitrile)
Structure
Molecular shape	tetrahedral at S
Hazards
	Occupational safety and health (OHS/OSH):
Main hazards	skin irritant
	GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H315, H319, H335
Precautionary statements	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). verify (what is ?) Infobox references

Para-Toluenesulfonic acid (PTSA, pTSA, or pTsOH) or tosylic acid (TsOH) is an organic compound with the formula CH₃ C₆H₄ SO₃H. It is a white extremely hygroscopic solid that is soluble in water, alcohols, and other polar organic solvents. 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.

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