| Thiophenol | |
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Thiophenol |
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Other names
Benzenethiol |
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| Identifiers | |
| CAS number | 108-98-5 |
| PubChem | 7969 |
| ChemSpider | 7681 |
| UNII | 7K011JR4T0 |
| ChEBI | CHEBI:48498 |
| ChEMBL | CHEMBL119405 |
| RTECS number | DC0525000 |
| Jmol-3D images | Image 1 |
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| Properties | |
| Molecular formula | C6H6S |
| Molar mass | 110.19 g/mol |
| Appearance | colorless liquid, with unpleasant odour. |
| Density | 1.0766 g/mL |
| Melting point |
-15 °C |
| Boiling point |
169 °C |
| Acidity (pKa) | 8 (H2O)[1], 10 (DMSO)[2] |
| Hazards | |
| R-phrases | R10 R24/25 R26 R41 |
| S-phrases | S23 S26 S28 S36/37/39 S45 |
| Main hazards | Toxic |
| Related compounds | |
| Related thiols | 1,2-Benzenedithiol Benzenemethanethiol |
| Related compounds | Phenol Benzeneselenol Diphenyl disulfide |
| (verify) (what is: /?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
Thiophenol is an organosulfur compound with the formula C6H6S, and sometimes abbreviated as PhSH. This foul-smelling colourless liquid is the simplest aromatic thiol. The chemical structures of thiophenols are analogous to phenols except the oxygen atom in the hydroxyl group (-OH) bonded to the aromatic ring is replaced by a sulfur atom. The prefix thio- implies a sulfur-containing compound and when used before a root word name for a compound which would normally contain an oxygen atom, in the case of 'thiol' that the alcohol oxygen atom is replaced by a sulfur atom.
Thiophenols also describes a class of compounds formally derived from thiophenol itself. All have a sulfhydryl group (-SH) covalently bonded to an aromatic ring. The organosulfur ligand in the medicine merthiolate is a thiophenol.
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There are several methods of synthesis for thiophenol and related compounds, although thiophenol itself is usually purchased for laboratory operations. Methods are the reduction of benzenesulfonyl chloride with zinc.[3] and the action of elemental sulfur on phenyl magnesium halide or phenyllithium followed by acidification.
Phenols can be converted to the thiophenols via rearrangement of their O-aryl dialkylthiocarbamates.[4] In the Leuckart Thiophenol Reaction the starting material is an aniline through the diazonium salt (ArN2X) and the xanthate (ArS(C=S)OR) [5][6]
Thiophenol has appreciably greater acidity than does phenol. Thiophenol has a pKa of 6 vs 10 for phenol. A similar pattern is seen for H2S vs. H2O and all thiols vs. the corresponding alcohols. Treatment of PhSH with strong base such as sodium hydroxide (NaOH) or sodium metal affords the salt sodium thiophenolate (PhSNa).
The thiophenolate is highly nucleophilic, which translates to a high rate of alkylation.[7] Thus, treatment of C6H5SH with methyl iodide in the presence of a base gives methyl phenyl sulfide, C6H5SCH3, a thioether. Such reactions are fairly irreversible. C6H5SH also adds to α,β-unsaturated carbonyls via Michael addition.
Thiophenols, especially in the presence of base is easily oxidized to diphenyl disulfide:
The disulfide can be reduced back the thiol using sodium borohydride followed by acidification. This redox reaction is also exploited in the use of C6H5SH as a source of H atoms.
Phenylsulfenyl chloride, a blood-red liquid (b.p. 41–42 °C), can be prepared by the reaction of thiophenol with chlorine (Cl2).[8]
Metal cations form thiophenolates, some of which are polymeric. One example is "C6H5SCu," obtained by treating copper(I) chloride with thiophenol.[9]
Thiophenol is an irritant and toxic by ingestion, absorption through skin, or inhalation. This chemical is also flammable.