Ethanethiol

Ethanethiol[1][2]
Names
IUPAC name
Ethanethiol
Other names
Ethyl mercaptan, Mercaptoethane, Ethyl sulfhydrate
Identifiers
75-08-1 Yes
ChemSpider 6103 Yes
Jmol-3D images Image
PubChem 6343
RTECS number KI9625000
UNII M439R54A1D Yes
UN number 2363
Properties
C2H6S
Molar mass 62.13404 g·mol−1
Appearance Colorless liquid[3]
Odor skunk-like[3]
Density 0.8617 g·cm−3
Melting point −148 °C (−234 °F; 125 K)
Boiling point 35 °C (95 °F; 308 K)
0.7% (20°C)[3]
Vapor pressure 442 mmHg (20°C)[3]
Acidity (pKa) 10.6
Hazards
Main hazards Nauseating
EU classification F Xn N
R-phrases R11, R20, R50/53
S-phrases S16, S25, S60, S61
NFPA 704
Flammability code 4: Will rapidly or completely vaporize at normal atmospheric pressure and temperature, or is readily dispersed in air and will burn readily. Flash point below 23 °C (73 °F). E.g., propane 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
4
2
0
Flash point −48 °C; −55 °F; 225 K[3]
Explosive limits 2.8%-18.0%[3]
US health exposure limits (NIOSH):
C 10 ppm (25 mg/m3)[3]
C 0.5 ppm (1.3 mg/m3) [15-minute][3]
500 ppm[3]
Related compounds
Related compounds
 Methanethiol
Butanethiol
Ethanol
thiophenol
Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Ethanethiol, commonly known as ethyl mercaptan, is a colorless gas or clear liquid with a distinct odor. It is an organosulfur compound with the formula CH3CH2SH. Abbreviated EtSH, it consists of an ethyl group (Et), CH3CH2, attached to a thiol group, SH. Its structure parallels that of ethanol, but with S instead of O. The odor of EtSH is infamous. Ethanethiol is more volatile than ethanol due to a diminished ability to engage in hydrogen bonding. Ethanethiol is toxic. It occurs naturally as a minor component of petroleum, and may be added to otherwise odorless gaseous products such as liquefied petroleum gas (LPG) to help warn of gas leaks. At these concentrations, ethanethiol is not harmful.

Preparation

Ethanethiol is prepared by the reaction of ethylene with hydrogen sulfide over a catalyst. The various producers utilize different catalysts in this process. It has also been prepared commercially by the reaction of ethanol with hydrogen sulfide gas over an acidic solid catalyst, such as alumina.[4]

Ethanethiol was originally reported by Zeise in 1834.[5] Zeise treated calcium ethyl sulfate with a suspension of barium sulfide saturated with hydrogen sulfide. He is credited with naming the C2H5S- group as mercaptum.

Ethanethiol can also be prepared by a halide displacement reaction, where ethyl halide is reacted with aqueous sodium bisulfide. This conversion was demonstrated as early as 1840 by Henri Victor Regnault.[6]

Odor

Ethanethiol has a strongly disagreeable odor that humans can detect in minute concentrations. The threshold for human detection is as low as one part in 2.8 billion parts of air. Its odor resembles that of leeks, onions, durian or cooked cabbage, but is quite distinct. Ethanethiol is intentionally added to butane and propane (see: LPG) to impart an easily noticed smell to these normally odorless fuels that pose the threat of fire, explosion, and asphyxiation.

Reactions

Main article: Thiol

Ethanethiol is a valued reagent in organic synthesis. In the presence of sodium hydroxide, it gives the powerful nucleophile SEt−. The salt can be generated quantitatively by reaction with sodium hydride.[7]

Ethanethiol can be oxidized to ethyl sulfonic acid, using bleach and related strong aqueous oxidants. Weaker oxidants, such as ferric oxide give the disulfide, diethyl disulfide:

2 EtSH + H2O2 → EtS-SEt + 2 H2O

Like other thiols, it behaves comparably to hydrogen sulfide. For example, it binds, concomitant with deprotonation to "soft" transition metal cations, such as Hg2+, Cu+, and Ni2+ to give polymeric thiolato complexes, Hg(SEt)2, CuSEt, and Ni(SEt)2, respectively.

Uses

In the underground mining industry, ethanethiol or ethyl mercaptan is referred to as "stench gas".[8] The gas is released into underground mine ventilation systems as an early warning system to alert mine workers during an emergency.[9] In Ontario, mining legislation dictates that "The alarm system in an underground mine shall, consist of the introduction into all workplaces of sufficient quantities of ethyl mercaptan gas or similar gas to be readily detectable by all workers".[10]

See also

References

  1. ↑ Merck Index, 12th edition, 3771
  2. ↑ "ICSC 0470 - ETHANETHIOL".
  3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 "NIOSH Pocket Guide to Chemical Hazards #0280". National Institute for Occupational Safety and Health (NIOSH).
  4. ↑ Norell, John; Louthan, Rector P. (1988). "Thiols". Kirk-Othmer Concise Encylclopedia of Chemical Technology (3rd ed.). New York: John Wiley & Sons, Inc. pp. 946–963. ISBN 978-0471801047.
  5. ↑ Zeise, William Christopher (1834). "Sur le Mercaptan; avec des Observations sur d'autres produits resultant de l'Action des Sulfovinates ainsi que de l'Huile de vin, sur des sulfures metalliques". Annales de Chimie et de Physique 56: 87–97.
  6. ↑ Regnault, V (1840). "Ueber die Einwirkung des Chlors auf die Chlorwasserstoffäther des Alkohols und Holzgeistes und über mehrere Punkte der Aethertheorie". Ann. 34: 24–52. doi:10.1002/jlac.18400340103.
  7. ↑ Mirrington, R. N.; Feutrill, G. I. (1988). "Orcinol Monomethyl Ether". Org. Synth.; Coll. Vol. 6, p. 859
  8. ↑ "Stench Gas". Zacon Ltd. Retrieved 20 February 2015.
  9. ↑ "A Stench Gas Warning System for Information Governance?". Barclay T Blair. Retrieved 20 February 2015.
  10. ↑ "Occupational Health and Safety Act: R.R.O. 1990, REGULATION 854 MINES AND MINING PLANTS Sect. 26(6)(a)". Ontario Ministry of Labour. Retrieved 20 February 2015.

External links