Benzyl mercaptan

Benzyl mercaptan
Names
	Preferred IUPAC name Phenylmethanethiol
	Other names alpha-Toluenethiol; Benzylthiol; Thiobenzyl alcohol; Benzyl mercaptan; alpha-Toluolthiol; Benzylhydrosulfide; Benzyl hydrosulfide
Identifiers
CAS Number	100-53-8 ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:137674;
ChEMBL	ChEMBL1224557 ;
ChemSpider	13851383 ;
ECHA InfoCard	100.002.602
PubChem CID	7509;
UNII	OS34A21OBZ ;
CompTox Dashboard (EPA)	DTXSID6026664 ;
	InChI InChI=1S/C7H8S/c8-6-7-4-2-1-3-5-7/h1-5,8H,6H2 Key: UENWRTRMUIOCKN-UHFFFAOYSA-N ; InChI=1/C7H8S/c8-6-7-4-2-1-3-5-7/h1-5,8H,6H2 Key: UENWRTRMUIOCKN-UHFFFAOYAC;
	SMILES SCc1ccccc1;
Properties
Chemical formula	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)
Solubility in water	low
Solubility	very soluble in ethanol, ether ; soluble in CS2 ; slightly soluble in CCl4
Acidity (pKa)	9.43 (H2O)
Refractive index (nD)	1.5751 (20 °C)
Hazards
NFPA 704 (fire diamond)	2 2 0
Flash point	70 °C (158 °F; 343 K)
	Lethal dose or concentration (LD, LC):
LD50 (median dose)	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). verify (what is ?) Infobox references

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.

Preparation and occurrence

Benzyl 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

Benzyl 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

Methoxy-substituted benzyl mercaptans have been developed that cleave easily, are recyclable, and are odorless.^[5]

References

^ 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.

[CRC97-1] Haynes, William M., ed. (2016). CRC Handbook of Chemistry and Physics (97th ed.). CRC Press. pp. 5–89. ISBN 978-1-4987-5428-6.

[2] 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.

[3] Norman Kharasch; Robert B. Langford (1964). "2,4-Dinitrobenzenesulfenyl Chloride". Org. Synth. 44: 47. doi:10.15227/orgsyn.044.0047.

[Greene5th-4] 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.

[5] 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.

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