Thiophenol is an organosulfur compound with the formula C6H5SH, sometimes abbreviated as PhSH. This foul-smelling colorless liquid is the simplest aromatic thiol. The chemical structures of thiophenol and its derivatives are analogous to phenols, where the oxygen atom in the hydroxyl group (-OH) bonded to the aromatic ring in phenol 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.
| |||
| Names | |||
|---|---|---|---|
| Preferred IUPAC name
Benzenethiol[1] | |||
Other names
| |||
| Identifiers | |||
3D model (JSmol)
|
|||
| 506523 | |||
| ChEBI | |||
| ChEMBL | |||
| ChemSpider | |||
| ECHA InfoCard | 100.003.306 | ||
| EC Number |
| ||
PubChem CID
|
|||
| RTECS number |
| ||
| UNII | |||
CompTox Dashboard (EPA)
|
|||
| |||
| |||
| Properties | |||
| C6H6S | |||
| Molar mass | 110.17 g·mol−1 | ||
| Appearance | Colorless liquid | ||
| Odor | Unpleasant, pungent | ||
| Density | 1.0766 g/mL | ||
| Melting point | −15 °C (5 °F; 258 K) | ||
| Boiling point | 169 °C (336 °F; 442 K) | ||
| 0.08%[2] | |||
| Solubility | Most organic solvents; aqueous base | ||
| Vapor pressure | 1 mmHg (18°C)[2] | ||
| Acidity (pKa) | |||
| -70.8·10−6 cm3/mol | |||
| Hazards | |||
| Occupational safety and health (OHS/OSH): | |||
Main hazards
|
Toxic | ||
| GHS labelling: | |||
    
| |||
| Danger | |||
| H226, H300, H310, H314, H315, H330, H410 | |||
| P210, P233, P240, P241, P242, P243, P260, P262, P264, P270, P271, P273, P280, P284, P301 P310, P301 P330 P331, P302 P350, P302 P352, P303 P361 P353, P304 P340, P305 P351 P338, P310, P312, P320, P321, P322, P330, P332 P313, P361, P362, P363, P370 P378, P391, P403 P233, P403 P235, P405, P501 | |||
| NFPA 704 (fire diamond) | |||
| Flash point | 56 °C; 132 °F; 329 K[2] | ||
| NIOSH (US health exposure limits): | |||
PEL (Permissible)
|
none[2] | ||
REL (Recommended)
|
C 0.1 ppm (0.5 mg/m3) [15-minute][2] | ||
IDLH (Immediate danger)
|
N.D.[2] | ||
| Related compounds | |||
Related thiols
|
1,2-Benzenedithiol Benzenemethanethiol | ||
Related compounds
|
Phenol Benzeneselenol Diphenyl disulfide | ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
| |||
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 thiomersal is a thiophenol.
Synthesis
editThere are several methods of synthesis for thiophenol and related compounds, although thiophenol itself is usually purchased for laboratory operations. 2 methods are the reduction of benzenesulfonyl chloride with zinc[5] and the action of elemental sulfur on phenyl magnesium halide or phenyllithium followed by acidification.
Via the Newman–Kwart rearrangement, phenols (1) can be converted to the thiophenols (5) by conversion to the O-aryl dialkylthiocarbamates (3), followed by heating to give the isomeric S-aryl derivative (4).[6]
In the Leuckart thiophenol reaction, the starting material is an aniline through the diazonium salt (ArN2X) and the xanthate (ArS(C=S)OR).[7][8] Alternatively, sodium sulfide and triazenes can react in organic solutions and yield thiophenols.[9]
Thiophenol can be manufactured from chlorobenzene and hydrogen sulfide over alumina at 700 to 1,300 °F (371 to 704 °C). The disulfide is the primary byproduct.[10] The reaction medium is corrosive and requires ceramic or similar reactor lining. Aryl iodides and sulfur in certain conditions may also produce thiophenols.[11]
Applications
editThiophenols are used in the production of pharmaceuticals including of sulfonamides. The antifungal agents butoconazole and merthiolate are derivatives of thiophenols.[9]
Properties and reactions
editAcidity
editThiophenol has appreciably greater acidity than does phenol, as is shown by their pKa values (6.62 for thiophenol and 9.95 for phenol). A similar pattern is seen for H2S versus H2O, and all thiols versus the corresponding alcohols. Treatment of PhSH with strong base such as sodium hydroxide (NaOH) or sodium metal affords the salt sodium thiophenolate (PhSNa).
Alkylation
editThe thiophenolate is highly nucleophilic, which translates to a high rate of alkylation.[12] Thus, treatment of C6H5SH with methyl iodide in the presence of a base gives methyl phenyl sulfide, C6H5SCH3, a thioether often referred to as thioanisole. Such reactions are fairly irreversible. C6H5SH also adds to α,β-unsaturated carbonyls via Michael addition.
Oxidation
editThiophenols, especially in the presence of base are easily oxidized to diphenyl disulfide:
- 4 C6H5SH O2 → 2 C6H5S-SC6H5 2 H2O
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.
Chlorination
editPhenylsulfenyl chloride, a blood-red liquid (b.p. 41–42 °C, 1.5 mm Hg), can be prepared by the reaction of thiophenol with chlorine (Cl2).[13]
Coordination to metals
editMetal cations form thiophenolates, some of which are polymeric. One example is "C6H5SCu," obtained by treating copper(I) chloride with thiophenol.[14]
Safety
editThe US National Institute for Occupational Safety and Health has established a recommended exposure limit at a ceiling of 0.1 ppm (0.5 mg m−3), and exposures not greater than 15 minutes.[15]
References
edit- ^ "Front Matter". Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. pp. P001–P004. doi:10.1039/9781849733069-FP001. ISBN 978-0-85404-182-4.
- ^ a b c d e f NIOSH Pocket Guide to Chemical Hazards. "#0050". National Institute for Occupational Safety and Health (NIOSH).
- ^ Cox, Brian G. Acids and Bases: Solvent Effects on Acid-base Strength. 1st ed. Oxford, UK: Oxford UP, 2013.
- ^ Bordwell, Frederick G.; Hughes, David L. (1982). "Thiol acidities and thiolate ion reactivities toward butyl chloride in dimethyl sulfoxide solution. The question of curvature in Broensted plots". The Journal of Organic Chemistry. 47 (17): 3224–3232. doi:10.1021/jo00138a005.
- ^ Adams, R.; C. S. Marvel, C. S. "Thiophenol". Organic Syntheses
{{cite journal}}: CS1 maint: multiple names: authors list (link); Collected Volumes, vol. 1, p. 504.. - ^ Melvin S. Newman and Frederick W. Hetzel (1971). "Thiophenols from Phenols: 2-Naphthalenethiol". Organic Syntheses. 51: 139. doi:10.15227/orgsyn.051.0139.
- ^ Leuckart, J. prakt. Chem., [2] 41, 189 (1890).
- ^ Tarbell, D. S.; Fukushima, D. K. (1947). "m-Thiocresol". Organic Syntheses. 27: 81. doi:10.15227/orgsyn.027.0081; Collected Volumes, vol. 3, p. 809.
- ^ a b Kazem-Rostami, Masoud; Khazaei, Ardeshir; Moosavi-Zare, Ahmad; Bayat, Mohammad; Saednia, Shahnaz (2012). "One-pot synthesis of thiophenols". Synlett. 23 (13): 1893–1896. doi:10.1055/s-0032-1316557. S2CID 196805424.
- ^ US Patent 2,490,257, Duncan J. Crowley & Alvin L Kosak, "Mono- and Polyalkyl Mono- and Polynuclear Mercaptans", issued 1949-12-06, assigned to Socony-Vacuum Oil Co.
- ^ Jiang, Y.; Qin, Y.; Xie, S.; Zhang, X.; Dong, J.; Ma, D., A (2009). "General and Efficient Approach to Aryl Thiols: CuI-Catalyzed Coupling of Aryl Iodides with Sulfur and Subsequent Reduction". Organic Letters. 22 (1): 52–56. doi:10.1021/acs.orglett.9b03866. PMID 31833778. S2CID 209341111.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ Campopiano, O. (2004). "Thiophenol". Encyclopedia of Reagents for Organic Synthesis. New York: John Wiley & Sons. doi:10.1002/047084289X. hdl:10261/236866. ISBN 9780471936237..
- ^ Barrett, A. G. M.; Dhanak, D.; Graboski, G. G.; Taylor, S. J. (1993). "(Phenylthio)nitromethane". Organic Syntheses
{{cite journal}}: CS1 maint: multiple names: authors list (link); Collected Volumes, vol. 8, p. 550. - ^ Posner, G. H.; Whitten, C. E. "Secondary and Tertiary Alkyl Ketones from Carboxylic Acid Chlorides and Lithium Phenylthio(alkyl)cuprate Reagents: tert-Butyl Phenyl Ketone". Organic Syntheses
{{cite journal}}: CS1 maint: multiple names: authors list (link); Collected Volumes, vol. 6, p. 248. - ^ CDC - NIOSH Pocket Guide to Chemical Hazards
External links
edit- Thiophenol, Toxicology Data Network