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Ethyl mercaptan

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Title: Ethyl mercaptan  
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Subject: Flammability limit, List of UN numbers 2301 to 2400
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Ethyl mercaptan


CAS number 75-08-1 YesY
PubChem 6343
ChemSpider 6103 YesY
UNII M439R54A1D YesY
RTECS number KI9625000
Jmol-3D images Image 1
Molecular formula C2H6S
Molar mass 62.13404 g·mol−1
Density 0.8617 g·cm−3
Melting point

-148 °C, 125 K, -234 °F

Boiling point

35 °C, 308 K, 95 °F

Acidity (pKa) 10.6
EU classification N
R-phrases R11, R20, R50/53
S-phrases S16, S25, S60, S61
Main hazards Nauseating
NFPA 704
Related compounds
Related compounds Methanethiol
 YesY (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
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.


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.[3]

Ethanethiol was originally reported by Zeise in 1834.[4] 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.[5]


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.


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.[6]

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.


External links

  • NLM Hazardous Substances Databank – Ethyl mercaptan
  • CDC - NIOSH Pocket Guide to Chemical Hazards
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