|Jmol-3D images||Image 1|
|Molar mass||158.18 g mol−1|
|Appearance||Colorless crystalline solid|
|Density||1.32 g/cm3 (47 °C)|
190 °C, 463 K, 374 °F
|Solubility in water||Soluble|
|Solubility in other solvents||Soluble in alcohol, insoluble in non-polar solvents|
|R-phrases||R20 R22 R34 R36 R37 R38|
|S-phrases||S26 S36/37/39 S45|
|Flash point||>113 °C|
|Related sulfonic acids||Sulfanilic acid
| (what is: / ?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Benzenesulfonic acid is an organosulfur compound with the formula C6H5SO3H. It is the simplest aromatic sulfonic acid. It forms white deliquescent sheet crystals or a white waxy solid that is soluble in water and ethanol, slightly soluble in benzene and insoluble in nonpolar solvents like diethyl ether. It is often stored in the form of alkali metal salts. Its aqueous solution is strongly acidic.
This conversion illustrates aromatic sulfonation, which has been called "one of the most important reactions in industrial organic chemistry."
Benzenesulfonic acid exhibits the reactions typical of other aromatic sulfonic acids, forming sulfonamides, sulfonyl chloride, and esters. The sulfonation is reversed above 220 °C. Dehydration with phosphorus pentoxide gives benzenesulfonic acid anhydride ((C6H5SO2)2O). Conversion to the corresponding benzenesulfonyl chloride (C6H5SO2Cl) is effected with phosphorus pentachloride.
It is a strong acid, being dissociated in water.
The alkali metal salt of benzenesulfonic acid was once widely used in the production of phenol:
- C6H5SO3Na + 2 NaOH → C6H5ONa + Na2SO3
- C6H5ONa + HCl → C6H5OH + NaCl
The process has been largely displaced by the Hock process, which generates less waste. Benzenesulfonic acid is mainly consumed by conversion to other specialty chemicals. A variety of pharmaceutical drugs are prepared as salts of benzenesulfonic acid and are known as besylates or besilates.
- Benzenesulfonic acid, Sigma-Aldrich
- Guthrie, J. P. Hydrolysis of esters of oxy acids: pKa values for strong acids Can. J. Chem. 1978, 56, 2342-2354. doi:10.1139/v78-385
- Otto Lindner, Lars Rodefeld "Benzenesulfonic Acids and Their Derivatives" in Ullmann's Encyclopedia of Industrial Chemistry 2005, Wiley-VCH, Weinheim. doi:10.1002/14356007.a03_507