Ethyl mercaptan

Ethanethiol[1][2]
Template:Chemboximage
IUPAC name Ethanethiol
Other names Ethyl mercaptan
Identifiers
CAS number	75-08-1 Y
PubChem	6343
ChemSpider	6103 Y
UNII	M439R54A1D Y
RTECS number	KI9625000
Jmol-3D images	Image 1
SMILES CCS
InChI InChI=1S/C2H6S/c1-2-3/h3H,2H2,1H3 Y Key: DNJIEGIFACGWOD-UHFFFAOYSA-N Y InChI=1/C2H6S/c1-2-3/h3H,2H2,1H3 Key: DNJIEGIFACGWOD-UHFFFAOYAW
Properties
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
Hazards
EU classification	N
R-phrases	R11, R20, R50/53
S-phrases	S16, S25, S60, S61
Main hazards	Nauseating
NFPA 704	4 2 0
Related compounds
Related compounds	Methanethiol Butanethiol Ethanol thiophenol
Y (verify) (what is: Y/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.

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.^[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]

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

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.

References

External links

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