Benzyl mercaptan is an organosulfur compound with the formula C6H5CH2SH. It is a common laboratory alkylthiol that occurs in trace amounts naturally. It is a colorless, malodorous liquid.
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| Names | |
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| Preferred IUPAC name
Phenylmethanethiol | |
| Other names
alpha-Toluenethiol
Benzylthiol Thiobenzyl alcohol Benzyl mercaptan alpha-Toluolthiol Benzylhydrosulfide Benzyl hydrosulfide | |
| Identifiers | |
3D model (JSmol)
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| ChEBI | |
| ChEMBL | |
| ChemSpider | |
| ECHA InfoCard | 100.002.602 |
PubChem CID
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| UNII | |
CompTox Dashboard (EPA)
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| Properties | |
| C7H8S | |
| Molar mass | 124.20 g/mol |
| Appearance | colourless liquid |
| Odor | Unpleasant leek or garlic-like |
| Density | 1.058 g/mL |
| Melting point | −30 °C (−22 °F; 243 K) |
| Boiling point | 195 °C (383 °F; 468 K) |
| low | |
| Solubility | very soluble in ethanol, ether soluble in CS2 slightly soluble in CCl4 |
| Acidity (pKa) | 9.43 (H2O)[1] |
Refractive index (nD)
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1.5751 (20 °C) |
| Hazards | |
| NFPA 704 (fire diamond) | |
| Flash point | 70 °C (158 °F; 343 K) |
| Lethal dose or concentration (LD, LC): | |
LD50 (median dose)
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493 mg/kg (rat, oral) |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Preparation and occurrence
editBenzyl mercaptan can be prepared by the reaction of benzyl chloride and thiourea. The initially formed isothiouronium salt must be subjected to alkaline hydrolysis to obtain the thiol.
It has been identified in boxwood (Buxus sempervirens L.) and is known to contribute to the smoky aroma of certain wines.[2] It also occurs naturally in coffee.
Use in organic synthesis
editBenzyl mercaptan is used for S-alkylation to give benzylthioethers.[3]
It has been used as a source of the thiol functional group in organic synthesis. Debenzylation can be effected by dissolving metal reduction:[4]
- RSCH2C6H5 + 2 H+ + 2 e− → RSH + CH3C6H5
Condensed tannins undergo acid-catalyzed cleavage in the presence of benzyl mercaptan.
Related derivatives
editMethoxy-substituted benzyl mercaptans have been developed that cleave easily, are recyclable, and are odorless.[5]
References
edit- ^ Haynes, William M., ed. (2016). CRC Handbook of Chemistry and Physics (97th ed.). CRC Press. pp. 5–89. ISBN 978-1-4987-5428-6.
- ^ Tominaga, Takatoshi; Guimbertau, Guy; Dubourdieu, Denis (2003). "Contribution of Benzenemethanethiol to Smoky Aroma of Certain Vitis vinifera L. Wines". Journal of Agricultural and Food Chemistry. 51 (5): 1373–1376. doi:10.1021/jf020756c. PMID 12590483.
- ^ Norman Kharasch; Robert B. Langford (1964). "2,4-Dinitrobenzenesulfenyl Chloride". Org. Synth. 44: 47. doi:10.15227/orgsyn.044.0047.
- ^ Wuts, Peter G. M. (2014). Greene's Protective Groups in Organic Synthesis (5th ed.). Hoboken, NJ: Wiley. p. 842. ISBN 978-1-118-05748-3.
- ^ Matoba, Manabu; Kajimoto, Tetsuya; Node, Manabu (2007). "Development of a Novel Benzyl Mercaptan as a Recyclable Odorless Substitute of Hydrogen Sulfide". Synlett. 2007 (12): 1930–1934. doi:10.1055/s-2007-984524.