Benzyl mercaptan

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Benzyl mercaptan
Skeletal formula benzyl mercaptan
Ball-and-stick model of the benzyl mercaptan molecule
Names
Preferred IUPAC name
Phenylmethanethiol
Other names
alpha-Toluenethiol
Benzylthiol
Thiobenzyl alcohol
Benzyl mercaptan
alpha-Toluolthiol
Benzylhydrosulfide
Benzyl hydrosulfide
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.002.602
UNII
Properties
C7H8S
Molar mass 124.20 g/mol
Appearance colourless liquid
Odor 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
1.5751 (20 °C)
Hazards
NFPA 704
Flammability code 2: Must be moderately heated or exposed to relatively high ambient temperature before ignition can occur. Flash point between 38 and 93 °C (100 and 200 °F). E.g., diesel fuel Health code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g., chloroform Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point 70 °C (158 °F; 343 K)
Lethal dose or concentration (LD, LC):
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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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[edit]

It can be prepared by the reaction of benzyl chloride and thiourea.

Benzyl mercaptan has been identified in boxwood (Buxus sempervirens L.) and is known to contribute to the smoky aroma of certain wines.[1] It also occurs naturally in coffee.

Use in organic synthesis[edit]

The compound has been used as a source of the thiol functional group in organic synthesis. It is introduced by S-alkylation to give alkyl benzylthioethers. Debenzylation is effected by dissolving metal reduction, which attacks the weakened S-benzyl bond:[2]

RSCH2C6H5 + 2 "H" → RSH + CH3C6H5

Condensed tannins undergo acid-catalyzed cleavage in the presence of benzyl mercaptan.

Related derivatives[edit]

Methoxy-substituted benzyl mercaptans have been developed that cleave easily, are recyclable, and are odourless.[3]

References[edit]

  1. ^ Takatoshi Tominaga, Guy Guimbertau and Denis Dubourdieu, "Contribution of Benzenemethanethiol to Smoky Aroma of Certain Vitis vinifera L. Wines", J Ag Food Chem, 51, 1373-1376(2003) doi:10.1021/jf020756c
  2. ^ Norman Kharasch; Robert B. Langford (1973). "2,4-dinitro-Benzenesulfenyl chloride". Org. Synth. ; Coll. Vol., 5, p. 474 
  3. ^ M. Matoba, T. Kajimoto, M. Node "Development of a Novel Benzyl Mercaptan as a Recyclable Odorless Substitute of Hydrogen Sulfide" Synlett 2007, pp. 1930–4. doi:10.1055/s-2007-984524