|Preferred IUPAC name
Benzene sulphonic acid; Benzenesulphonic acid; Phenylsulfonic acid; Phenylsulphonic acid; Besylic acid
3D model (JSmol)
|UN number||2583, 2585, 1803|
|Molar mass||158.17 g·mol−1|
|Appearance||Colorless crystalline solid|
|Density||1.32 g/cm3 (47 °C)|
|Melting point||* 44 °C (hydrate)
|Boiling point||190 °C (374 °F; 463 K)|
|Solubility in other solvents||Soluble in alcohol, insoluble in non-polar solvents|
|Safety data sheet||External MSDS|
|GHS signal word||Danger|
|H290, H302, H314, H315, H319, H335|
|P234, P260, P261, P264, P270, P271, P280, P301+312, P301+330+331, P302+352, P303+361+353, P304+340, P305+351+338, P310|
|Flash point||> 113 °C|
Related sulfonic acids
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is ?)(|
Benzenesulfonic acid (conjugate base benzenesulfonate) 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 almost fully dissociated in water.
Benzenesulfonic acid and related compounds undergo desulfonation when heated in water near 200 °C. The temperature of desulfonation correlates with the ease of the sulfonation:
- C6H5SO3H + H2O → C6H6 + H2SO4H
The alkali metal salt of benzenesulfonic acid was once used in the industrial production of phenol. The process, sometimes called alkaline fusion, initially affords the phenoxide salt:
- 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.
In a diluted form, it is also used as a polymer remover stripping agent.
- Benzenesulfonic acid[dead link], Sigma-Aldrich
- Besylic acid, ChemIndustry
- 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